WO2007057023A1

WO2007057023A1 - A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil

Info

Publication number: WO2007057023A1
Application number: PCT/DK2006/000645
Authority: WO
Inventors: Tom Nøhr CHRISTIANSEN
Original assignee: S-Rain Control A/S
Priority date: 2005-11-18
Filing date: 2006-11-20
Publication date: 2007-05-24

Abstract

A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil according to a aspect of the invention comprises a water pipeline, a first plurality of controllable irrigation valves, a second plurality of field sensors measuring specific irrigation parameters, and a third plurality of localised irrigation control units. The third plurality of localised irrigation control units each comprises a sensor decoder connected to a specific field sensor of the second plurality of field sensors and/or a line decoder connected to a specific controllable irrigation valve of the first plurality of controllable irrigation valves. The two-wire controlling and monitoring system further comprises a controller and power supply unit having a set of schedules of instructions and supplying power by applying a first alternating DC voltage signal to a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units. The two-wire cable provides the power from the controller and power supply unit to each of the third plurality of localised irrigation control units. The controller and power supply unit transmits the schedules of instructions to the third plurality of localised irrigation control units through the two-wire cable and receives the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable.

Description

A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil

This invention relates generally a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil.

Description of the related art

The most commonly known two-wire irrigation control systems, such as control systems described in US patents US 3,723,753, US 4,004,612, US 4,007,458, US 4,131 ,882, US 4,176,395, US 4,535,401 , US 5,570,030 and US 5,848,609 to which reference is made and which are hereby incorporated in the present specification by reference, provide control of a number of remotely located irrigation or sprinkler valves from a central location by means of control signals encoded on to a single pair of power transmission lines linking a central encoder and a number of remote decoders.

The two-wire irrigation control system according to US 4,007,458 encodes and transmits an address of a specific remotely located irrigation valve and on/off signals onto an alternating current signal (AC) by clipping half portions of the signal to represent zero values.

Similarly the two-wire interactive irrigation control system according to US 4,176,395 transmits data by selectively clipping the original power frequency signal during eight consecutive cycles, suppressing the power frequency signal during the following full cycle, during which time a feedback signal may be transmitted from sensors located at specific areas, then transmitting eight undistorted power frequency cycles, and suppressing the power frequency signal for one following cycle, during which time a feedback signal relating to a portable operator may be transmitted.

Both two-wire irrigation control systems according to US 4,007,458 and US 4,176,395 communicate to remotely located irrigation valves or decoders by clipping of the power signals consequently while performing a transmission on the power line power to the remotely located irrigation valves or decoders is significantly reduced.

Furthermore the two-wire irrigation control systems according to US 4,007,458 and US 4,176,395 utilises sinusoidal signals for transmitting power to remotely located irrigation valves or decoders. Sinusoidal signals being AC signals generally need to be converted into DC in order to drive microprocessor electronic circuitry adding total costs of the two-wire irrigation systems for the electronics incorporated in the remotely located irrigation valves or decoders.

An object of the present invention is to provide a two-wire controlling and monitoring system for in particular controlling a plurality of controllable irrigation or sprinkler valves placed at specific localised areas, monitoring specific irrigation parameters at the specific localised areas and communicating through a two-wire cable with line and sensor decoders located at the specific localised areas while limiting above described power loss due to signalling on the two-wire cable.

A further object of the present invention is to provide a two-wire controlling and monitoring system for in particular controlling a plurality of controllable irrigation or sprinkler valves placed at specific localised areas, monitoring specific irrigation parameters at the specific localised areas and communicating through a two-wire cable with line and sensor decoders located at the specific localised areas while limiting above described power loss due to signalling on the two-wire cable.

Moreover it is an object of the present invention to compensate for leak currents in the two-wire cable.

A particular advantage of the present invention is utilisation of a power supply signal for the operation of the controllable irrigation valves hence performing an improved power transmission within general safety specifications.

A particular feature of the present invention is an improved corrosion resistance. A further particular advantage of the present invention is the compensation of leak currents. The degree of compensation of the leak currents represents a measure of the quality of the signalling forth and back on and through the two-wire cable.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a first aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering or non-watering of said specific area of said localised areas of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors and/or a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said sensor decoder and said line decoder further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, and said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable.

According to the basic realisation of the first aspect of the present invention the application of two alternating DC voltage signals having respectively inverted polarity on to the two-wire cable provides an improved power transmission with respect to prior art's application of sinusoidal voltage signals. The improvement is approximately a factor 2. Sinusoidal voltage signals although ideal for some purposes impose a restriction on maximum attainable power transmission during a time frame caused by the inherent shape of the voltage signal squared as compared to a square wave voltage signal squared. Furthermore, by relying on slow alternating DC voltage signals for powering of the decoders instead of relying on sinusoidal voltage signals having standard 50Hz or 60Hz network frequencies a less noise sensitive and subsequently cheaper circuit may be implemented, since relatively little attention should be given to noise considerations. Additionally, the square wave structure of the alternating DC voltage signal provides an ideal platform for carrying binary information, which will be further described below.

The water pipeline characteristic of the two-wire irrigation controlling and monitoring system according to the first aspect of the present invention is wholly or partly buried under ground, or the water pipeline is placed on the ground. Parts of the pipelines being above ground level provide movable sections that may easily be moved into positions according to the conditions of the local areas. Furthermore the water pipeline is constructed from plastic materials or metal materials such as iron, steel, copper, silver, gold or any alloys thereof in any combinations thereof.

Generally plastic tubes are favourable since the price is low with respect to metal material pipes and since plastic tubes are more flexible rendering it possible to rearrange the layout of the pipes without causing severe expenses.

The first plurality of controllable irrigation valves according to the first aspect of the present invention are magnetically, electrically, hydraulically or pneumatically operated or combinations thereof. The first plurality of controllable irrigation valves according to the first aspect of the present invention is preferably electrically operated and opened by applying an inrush voltage or current signal followed by a hold voltage or current signal to the pair of valve control inputs and closed by applying no voltage or current signal to the pair of valve control inputs. Further according to the first aspect of the present invention the line decoders provide the inrush voltage, the hold voltage and the zero voltage to the first plurality of controllable irrigation valves by supplying from the pair of valve control outputs a pulsed alternating DC control signal to the pair of valve control inputs in accordance with the transmitted schedules of instructions. The pulsed alternating DC voltage signal defines a maximum differential voltage in the range of 25V to 45V such as ranges 27V to 43V or 30V to 40V or preferably the maximum differential voltage is 35V, defines a minimum differential voltage in the range of OV to 5V such as ranges OV to 3V or OV to 1 V or preferably the minimum differential voltage is OV and defines a line decoder output pulse width in the range of 10μs to 0.1s such as ranges 200μs to 2ms or 800μs to 1.25ms or preferably the line decode output pulse width is 1ms. The line decoder output pulse width defines a first part having the maximum differential voltage and a second part having the minimum differential voltage. The pulsed alternating DC voltage signal constitutes the inrush voltage by having the first part longer than or equal to the second part during a period in the range 10ms to 1s such as 30ms to 100ms and constitutes the hold voltage by having the first part shorter than the second part during a period determined in accordance with the schedule of instructions transmitted to the line decoders by the controller and power supply unit. The parts may have any particular lengths to provide for any composition of signals generating a wide variety of average voltages, however the composition described above is optimal for driving an electrically driven irrigation valve with respect to power consumption of the line decoder.

The first pulse width of the first and second alternating DC voltage signals according to the first aspect of the present invention is equal to the second pulse width, is smaller than the second pulse width or is greater than the second pulse width. Preferably the first pulse width is substantially equal to the second pulse width thereby constituting a square wave voltage signal.

The first alternating DC voltage signal and the second alternating DC voltage signal according to the first aspect of the present invention alternate with a frequency less than AC frequency of power networks such as 50Hz or 60Hz. The first pulse width of the first alternating DC voltage signal and the second alternating DC voltage signal is in the range 100ms to 10s such as ranges 200ms to 2s, 300ms to 1s, 400ms to 800ms, 450 ms to 550 ms, 475 ms to 525 ms or 490 ms to 510 ms, or preferably the first pulse width is 500 ms and the second pulse width of the first alternating DC voltage signal and the second alternating DC voltage signal is in the range 100ms to 10s such as ranges 200ms to 2s, 300ms to 1s, 400ms to 800ms, 450 ms to 550 ms, 475 ms to 525 ms or 490 ms to 510 ms, or preferably the second pulse width is 500 ms. By reducing frequency of alternation, toggling or inversion of the first and the second alternating DC voltage signals the noise sensitivity of the circuitry is reduced and furthermore the tolerances as to acceptable accuracy of pulse widths is shifted from μs range to ms range.

The first alternating DC voltage signal and the second alternating DC voltage signal according to the first aspect of the present invention during the first pulse width and the second pulse width averages voltages greater than or equal to zero voltage. Alternatively, the first alternating DC voltage signal and the second alternating DC voltage signal during the first pulse width and the second pulse width averages voltages less than or equal to zero voltage. In particular the first alternating voltage signal and the second alternating voltage signal during the first pulse width and the second pulse width averages an average voltage in the range -5V to -0.5V such as ranges — 4V to -1 V or -2.5V to -1.5V, or preferably the average voltage is -2V. The voltage maximum of the first and second alternating DC voltage signals according to the first aspect of the present invention is in a range from +1 OV to +20V, such as ranges +13V to +19V or +14V to +17V, or preferable the voltage maximum is +15V and the voltage minimum in a range from -15V to -25V, such as ranges -17V to - 23V and -19V to -21V, or preferable the voltage minimum is -20V. By applying a numerically larger minimum voltage compared to maximum voltage off setting the average voltage below ground voltage the risk for deterioration of the two-wire cable caused by corrosion is significantly reduced since the deterioration of the two- wire cable at locations where the presence of an insulating layer around the two- wire cable has been damaged will be based on an alkaline process. The alkaline process donates electrons to the ground level due to the voltage difference and accepts a layer of ions substituting the missing electrons and thus the layer of ion creates a saturation layer at the exposed part of the two-wire cable reducing further corrosion of the two-wire.

The maximum current according to the first aspect of the present invention is in the range of 0.5A to 2A such as 0,75A to 1.5A and e.g. preferably the maximum current is 1.1A, and the minimum current is in the range 2OmA to 15OmA such as ranges 3OmA to 100mA or 35mA to 85mA, or preferably the minimum current is 40mA. Additionally, the third pulse width defining a part of the alternating DC current signal is greater than the fourth pulse width, and the fourth pulse width defining another part of the alternating DC current signal is in the range 0.1ms to 10ms such as range 0.5ms to 7ms or preferably the fourth pulse width is shorter than 5ms. The alternating DC current signal provides low current sequences during which communication may be performed from irrigation control units placed at specific locations to the controller and power supply unit.

Communication from the controller and power supply unit to the irrigation control units placed at specific locations may consist of schedules of instructions according to the first aspect of the present invention. The schedules of instructions are transmitted onto the two-wire system by re-scaling the first pulse width or the second pulse width of the first and second alternating DC voltage signals to a fifth pulse width in the range 10ms to 49ms such as ranges 15ms to 35ms or 17ms to 25ms, or preferably the fifth pulse width is 20ms indicating a binary "1", or by re- scaling the first pulse width or the second pulse width of the first and second alternating DC voltage signals to a sixth pulse width in the range 0.5ms to 9ms such as ranges 1 ms to 8ms or 2ms to 5ms, or preferably the sixth pulse width is 5ms indicating binary "0". By modulating pulse width of the first and second alternating DC voltage signals instead of clipping of portions of the voltage signals significantly improves power transmission from the controller and power supply unit to the irrigation control units while providing ingenious means for communication.

The transmitted schedules of instructions according to the first aspect of the present invention comprise a type declaration determining additional content of a transmission from the controller and power supply unit to the third plurality of localised irrigation control units. The additional content such as an address of a specific designated localised irrigation control unit of the third plurality of localised irrigation control units, data disclosing information regarding actions to be taken by the specific designated localised irrigation control unit of the third plurality of localised irrigation control units and/or a first check and a second check ensuring a safe reception of the transmission is terminated by stop signal having a seventh pulse width. The seventh pulse width is in the range 50ms to 70ms such as 55ms to 65ms, or preferably the seventh pulse width is 60ms. The content of transmissions may have numerous purposes and achieve numerous tasks and provide means for performing a wide variety of transmissions comprising a plurality of information types.

The above described type declaration comprising 4 bits provides 16 optional operations such as Arbitration, Data, Control (On/Off), Broadcast, Test and Pole leaving room for still 10 possible operations which according to today's needs is sufficient. However an increase of the transmission size of the type declaration to 8, 16 or 32 bits will even further expand the possible variety of operations. The address of the specific designated localised irrigation control unit of the third plurality of localised irrigation control units comprises an address transmission size in the range 0 to 128 bits such as ranges 0 to 64 bits or 0 to 32, or the address transmission size is preferably 16 bits. The address transmission size determines the maximum number of possible communicative or addressable irrigation control units connected to the controller and power supply. Therefor if additional irrigation control units are needed for either operation of sensors or control of irrigation valves the address transmission size may be extended accordingly.

The data disclosing information regarding actions to be taken by the specific designated localised irrigation control unit of the third plurality of localised irrigation control units comprises a data transmission size in the range of 0 to 64KBYTE. The data contained in a transmission may include information regarding timing of opening and closing of the controllable irrigation valves, however the data may include a wide variety of informations.

The first check and the second check ensuring a safe reception of the transmission comprise a check transmission size in the range 0 to 128 bits such as ranges 0 to 64 bits or 0 to 32 bits or preferably the check transmission size is 4 bit for each of the first and second check. The first and second check provides means for checking if transmitted information has been properly received.

The controller and power supply unit according to the first aspect of the present invention comprises a microprocessor, a storage unit for storing the schedules of instructions, an output section for providing power to the two-wire cable and transmitting the schedules of instruction on the two-wire cable, and an input section for monitoring voltage of the two-wire cable. An interrupt window is initiated following a DC alternation of the first alternating DC voltage signal and the second alternating DC voltage signal and a power supply period. The power supply period is in the range 250ms to 550ms such as ranges 300ms to 500ms or 350ms to 450ms, or preferably the power supply time period is 400ms and the interrupt window is in the range of 0ms to 20ms or preferably the interrupting window is shorter than 5ms. The microprocessor controls the output section to apply the minimum current to the two-wire cable during an interrupt window. The interrupt window allows the sensor decoders or line decoders to perform an interrupt during which the decoders may communicate information to the controller and power supply unit.

Each of the sensor decoders and/or line decoders comprises a short circuiting circuit providing an interrupt signal during the interrupt window to the controller and power supply unit by unidirectional short circuiting the pair of control and power supply inputs hence reducing differential voltage of the two-wire cable and no interrupt signal by open circuiting the pair of control and power supply inputs. The interrupt signal is constituted by a voltage drop of the differential voltage of the two- wire cable in the range 5V to 35V such as range 15V to 30V, or preferably the voltage drop is 25V thus the differential voltage is 10V. Hence the voltage of the two-wire cable during the interrupt signals is negative relative to ground voltage e.g. -10V and therefor the alkaline process described earlier is maintained during interrupt signals. The microprocessor records the interrupt signal from at least one sensor decoder and/or line decoder of the third plurality of localised irrigation control units through the input section monitoring voltage of the two-wire cable and subsequently operates the output section to perform a DC alternation of the first alternating DC voltage signal and the second alternating DC voltage signal and operates the output section to terminate the interrupt window and apply the maximum current to the two-wire cable. Additionally, the microprocessor following a recording of the interrupt signal from at least one interrupting sensor decoder and/or line decoder of the third plurality of localised irrigation control units performs a DC alternation of the first alternating DC voltage signal and the second alternating DC voltage signal and transmits the type declaration Arbitration followed by a series of binary 'Ts including an answer window for the at least one interrupting sensor decoder and/or line decoder of the third plurality of localised irrigation control units to answer as described below to the binary "1". The answer window is initiated following a DC alternation of the first alternating DC voltage signal and the second alternating DC voltage signal and a pause period, the pause period is in the range 2ms to 10ms such as ranges 3ms to 8ms or 4ms to 6ms, or preferably the pause period is 5ms. The answer window is in the range of 0ms to 20ms or preferably the answer window is shorter than 2.5ms. The series of binary "1"s constitute an opportunity for the interrupting decoder to answer yes or no during an answer window in accordance with the interrupting decoder's address. By selecting a series of binary "1 "s for obtaining the address from the interrupting decoder the shortest Arbitration transmission is achieved since in case of several interrupting decoders the decoder with the lowest address will be addressed first and decoders with higher addresses will be addressed subsequently at next possible interrupt.

As in the case of the interrupt signal the short circuiting circuit provides an answer signal during the answer window to the controller and power supply unit by unidirectional short circuiting the pair of control and power supply inputs hence reducing differential voltage of the two-wire cable and no answer signal by open circuiting the pair of control and power supply inputs. The answer signal is constituted by a voltage drop of the differential voltage on the two-wire cable in the range 5Vto 35V such as range 15V to 30V, or preferably the voltage drop is 25V or the differential voltage is 10V. Hence the voltage of the two-wire cable during the answer signals is negative relative to ground voltage e.g. -10V and therefor the alkaline process described above is maintained during the answer window. The microprocessor interprets the answer signal as an indication of a binary "0" and no answer signal as a binary "1".

The microprocessor according to the first aspect of the present invention further controls the output section to supply the minimum current to the two-wire cable during the answer window, so as to avoid unnecessary power loss caused by answering decoders transmission of binary "0"s. As soon as the answer form the answering decoder is detected by the controller and power supply unit the controller and power supply unit applies the maximum current to the two-wire cable. Hence the power loss is significantly reduced as compared to techniques in state of the art control irrigation systems.

The second plurality of field sensors according to the first aspect of the present invention comprises a selection of temperature sensors, humidity sensors, pressure sensors, magnetic field sensors, mechanical movement sensors, mechanical strain sensors, flow sensors, fertiliser sensors or any combination thereof. The objective of these sensors is to provide specific parameters giving a complete picture of the conditions of the specific localised areas and may further be implemented in a wide variety of ways in order to obtain specific requested information regarding the conditions of the ground. A further objective of these sensors is to provide irrigation parameters giving a complete picture of the working conditions, functionality and operation of the controllable irrigation valves.

The controller and power supply unit according to the first aspect of the present invention during a declared type of transmission of schedules of instructions requests the specific irrigation parameters from an addressed sensor decoder of the third plurality of localised irrigation control units and subsequently the controller and power supply unit transmits a series of binary "1" including the answer window for the addressed decoder to answer to the binary "1 ". The microprocessor records the answer signal from at least one sensor decoder of the third plurality of localised irrigation control units through the input section monitoring the voltage of the two- wire cable and operates the output section to perform a DC alternation of the first alternating DC voltage signal and the second alternating DC voltage signal and subsequently operates the output section to terminate the answer window and apply the maximum current to the two-wire cable. The term DC alternation is to be conceived as a generic term for toggle, inversion or switching between the maximum and minimum voltages of the first and second alternating DC voltage signal. By implementing the communication from the irrigation control units as described above a series of advantages are achieved. The two-wire irrigation controlling and monitoring system consumes little power during normal operation and during transmission of information between the controller and power supply unit and the irrigation control units. By accomplishing the transmission of information using a pulse width defining a binary "1" and a pulse width defining a binary "0" the two-wire irrigation controlling and monitoring system provides an undisturbed power transmission at the same time as exchange of information.

The above objects, the above advantages and the above features together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a second aspect of the present invention obtained by a method for controlling and monitoring in particular irrigation of localised areas of soil and comprising the following steps of: providing water to said localised areas of soil through a water pipeline, controlling discharge or supply of water from said water pipeline, providing watering or non-watering of a specific area of said localised areas of soil through a first plurality of controllable irrigation valves each positioned at said specific area of said localised areas of soil and said first plurality of controllable irrigation valves having a pair of valve control inputs, measuring specific irrigation parameters through a second plurality of field sensors positioned at said specific areas of said localised areas of soil and said second plurality of field sensors having a pair of sensor outputs, transmitting control signals to said first plurality of controllable irrigation valves and said second plurality of field sensors though a third plurality of localised irrigation control units comprising a sensor decoder and a line decoder, providing valve control signals to said first plurality of controllable irrigation valves and/or recording said specific irrigation parameters from said second plurality of field sensors, each of said third plurality of localised irrigation control units having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves and/or a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of the second plurality of field sensors and having a pair of control and power supply inputs, providing a set of schedules of instructions by means of a controller and power supply unit having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, providing a two-wire cable, interconnecting said controller and power supply unit and said third plurality of localised irrigation control units through a two- wire cable connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said control and power unit to each of said third plurality of localised irrigation control units, and transmitting said schedules of instructions from said controller and power supply unit to said third plurality of localised irrigation control units through said two- wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable.

The method according to the second aspect of the present invention describes operation of a two-wire controlling and monitoring system which includes any of the above discussed features and provides a method for achieving significant reductions in power consumption relative to today's state of the art.

The above objects, the above advantages and the above features together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a third aspect of the present invention obtained by a localised irrigation control unit for a two-wire controlling and monitoring system including a controller and power supply unit and for in particular irrigation of localised areas of soil and said localised irrigation control unit comprising: a field sensor decoder for receiving input signals from a field sensor, converting said input signals to a binary number and transmitting said binary number to said controller and power supply unit, and a line decoder for receiving instructions from said controller and power supply unit or a mark sender unit, converting said instructions to a control signal and providing said control signal to a controllable irrigation valve.

The localised irrigation control unit according to the third aspect of the present invention provides means for irrigating of the localised areas, means for measuring of specific irrigation parameters describing the conditions of the localised areas, means for communicating with the mark sender unit and means performing communication with the controller and power supply unit. The localised irrigation control unit circuitry may be implemented for carrying out communication on a two- wire conducting cable, but may however be implemented for carrying out communication on optic cables or be implement for carrying out communication through radio transmitted signals. The input signals comprising analogue voltage signals, analogue current signals, digital pulse count signals, digital pulse width modulation signals or digital pulse frequency modulation signals or any combinations thereof. The mark sender provides the possibility for manually controlling the operation of the controllable irrigation valves irrespective of the schedules of instructions transmitted by the controller and power supply unit. The mark sender ensures that an operator may initiate irrigation at localised areas by transmitting control signals to the controllable irrigation valve from the mobile mark sender.

The sensor decoder included in the localised irrigation control unit according the third aspect of the present invention comprises a field sensor power supply and field sensor signal amplifier having a pair of sensor inputs connected to a pair of sensor outputs of a specific field sensor, a control and power supply input section having pair of control and power supply inputs connected to a two-wire cable interconnecting the sensor decoder and the controller and power supply unit, a short circuiting circuit having switching means connected between the pair of control and power supply inputs, and a first microprocessor unit interconnecting the field sensor power supply and field sensor signal amplifier and the short circuiting circuit.

The line decoder included in the localised irrigation control unit according the third aspect of the present invention comprises a control and power supply input section having a pair of control and power supply inputs connected to the two-wire cable interconnecting the line decoder and the controller and power supply unit, a valve control power output stage having at least one pair of valve control outputs connected to a pair of valve control inputs of a specific controllable irrigation valve, and a second microprocessor unit interconnecting the control and power supply input section and the valve control output.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a fourth aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area controlled by the controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and a specific line decoder being the intentional receiver of a specific schedule of instructions responding by transmitting an acknowledgement signal to the controller and power supply unit through the two-wire cable within a first time frame of the first pulse provided the specific schedule of instructions is correctly received or, alternatively, transmitting a not-acknowledgement signal to the controller and power supply unit through the two-wire cable within a second time frame of the first pulse provided the specific schedule of instructions is not correctly received.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a fifth aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area of the localised areas controlled by the controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, the sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and a specific sensor decoder being the intentional receiver of a specific schedule of instructions responding by transmitting an acknowledgement signal to the controller and power supply unit through the two-wire cable within a first time frame of the first pulse provided the specific schedule of instructions is correctly received or, alternatively, transmitting a not-acknowledgement signal to the controller and power supply unit through the two-wire cable within a second time frame of the first pulse provided the specific schedule of instructions is not correctly received.

The two-wire controlling and monitoring systems according to the fourth and fifth aspects of the present invention are particularly advantageous in that the intentional receiver of a specific schedule of instructions responds positively by transmitting an acknowledgement signal provided the specific schedule of instructions is correctly received or alternatively transmits a not-acknowledgement signal provided the specific schedule of instruction is not correctly received. By the positive acknowledgement or not-acknowledgement, the controller and power supply unit receive positive verification of receipt or not-receipt from the intentional receiver by receiving the acknowledgement or not-acknowledgement signal, respectively, and also by the lack of any acknowledgement or not-acknowledgement signal determines that no intentional receiver of the specific schedule of instructions has received the schedule of instructions and, therefore, a retransmission is carried out, likewise, by the receipt of the not-acknowledgement signal, a retransmission is carried out.

The transmission of the acknowledgement or, alternatively, the not-acknowledgement signal from the intentional receiver of the specific schedule of instructions within the first or the second time frames, respectively, is advantageously controlled by the controller and power supply unit supplying a minimum current to the two-wire cable during the first and the second time frames of the first pulse allowing the transmission of the acknowledgement or, in the alternative, the not- acknowledgement signal from the intentional receiver of the specific schedule of instructions to the controller and power supply unit to be carried out in accordance with the short-circuit signalling technique mentioned above and also to be described in greater details below with reference to the presently preferred embodiment of the system according to the present invention.

The first frame may according to a first embodiment of the two-wire controlling and monitoring system according to the fourth and fifth aspects of the present invention be located prior to the second frame, however, according to the presently preferred embodiment of the two-wire controlling and monitoring system according to the fourth and fifth aspects of the present invention, the second frame is located prior to the first frame, thereby allowing the controller and power supply unit to readily retransmit the schedule of instructions after receipt of the not-acknowledgement signal.

The two-wire controlling and monitoring system according to the fourth and fifth aspects of the present invention preferably further exhibit the features of the two- wire controlling and monitoring system according to the first aspect of the present invention as discussed above.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a sixth aspect of the present invention obtained by a method for controlling and monitoring in particular irrigation of localised areas of soil and comprising the following steps of: providing water to the localised areas of soil through a water pipeline, controlling the discharge or supply of water from the water pipeline, providing watering of the specific area of a localised areas of soil through a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil and the first plurality of controllable irrigation valves having a pair of valve control inputs, measuring specific irrigation parameters through a second plurality of field sensors positioned at specific areas of the localised areas of soil and the second plurality of field sensors having a pair of sensor outputs, transmitting control signals to the first plurality of controllable irrigation valves and the second plurality of field sensors though a third plurality of localised irrigation control units comprising a sensor decoder and a line decoder, providing valve control signals to the first plurality of controllable irrigation valves and/or recording the specific irrigation parameters from the second plurality of field sensors, each of the third plurality of localised irrigation control units having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves and/or a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors and having a pair of control and power supply inputs, providing a set of schedules of instructions by means of a controller and power supply unit having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, providing a two-wire cable, interconnecting the controller and power supply unit and the third plurality of localised irrigation control units through a two-wire cable connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the control and power unit to each of the third plurality of localised irrigation control units, transmitting the schedules of instructions from the controller and power supply unit to the third plurality of localised irrigation control units through the two-wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and transmitting from an irrigation control unit being the intentional receiver of a specific schedule of instructions an acknowledgement signal to the controller and power supply unit through the two-wire cable within a first time frame of the first pulse, provided the specific schedule of instructions is correctly received or alternatively a not-acknowledgement signal to the controller and power supply unit through the two-wire cable within a second time frame of the first pulse provided the specific schedule of instructions is not correctly received.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a seventh aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area controlled by the controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and a first time frame being defined in the first alternating DC voltage signal, within the first time frame of a first occurring first alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to a first short circuiting current detection level and measuring any reduction of the first alternating DC voltage signal, and within the first time frame of a succeeding first alternating DC voltage signal the controller and power supply unit increasing the first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of the first alternating DC voltage signal.

The two-wire controlling and monitoring system in the seventh aspect of the present invention further comprising: a second time frame being defined in the second alternating DC voltage signal, within the second time frame of a first occurring second alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to the increased first short circuiting current detection level and measuring any reduction of the second alternating DC voltage signal, and within the second time frame of a succeeding second alternating DC voltage signal the controller and power supply unit increasing the increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of the second alternating DC voltage signal.

According to the basic realisation of the seventh aspect of the present invention, during the first time frame the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units and during the second time frame the controller and power supply unit not transmitting the schedules of instructions to the third plurality of localised irrigation control units.

According to the basic realisation of the seventh aspect of the present invention the controller and power supply unit subsequently applies during the first and second alternating DC voltage signals the increased first short circuiting current detection level and the second short circuiting current detection level.

According to the basic realisation of the seventh aspect of the present invention the two-wire controlling and monitoring system further comprises a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and the third plurality of localised irrigation control units further comprises a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, and the sensor decoders further each having a pair of control and power supply inputs.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a eighth aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area of the localised areas controlled by the controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, the sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and a first time frame being defined in the first alternating DC voltage signal, within the first time frame of a first occurring first alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to a first short circuiting current detection level and measuring any reduction of the first alternating DC voltage signal, and within the first time frame of a succeeding first alternating DC voltage signal the controller and power supply unit increasing the first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of the first alternating DC voltage signal.

The two-wire controlling and monitoring system in the eighth aspect of the present invention further comprises a second time frame being defined in the second alternating DC voltage signal, within the second time frame of a first occurring second alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to the increased first short circuiting current detection level and measuring any reduction of the second alternating DC voltage signal, and within the second time frame of a succeeding second alternating DC voltage signal the controller and power supply unit increasing the increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of the second alternating DC voltage signal.

According to the basic realisation of the eighth aspect of the present invention during the first time frame the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units and during the second time frame the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units.

According to the basic realisation of the eighth aspect of the present invention the controller and power supply unit subsequently apply during the first and second alternating DC voltage signals the increased first short circuiting current detection level and the second short circuiting current detection level.

According to the basic realisation of the eighth aspect of the present invention the third plurality of localised irrigation control units each further comprises a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a ninth aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area controlled by the controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and a third time frame being defined in the first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within the third time frame the controller and power supply unit measuring a measuring level of the first alternating DC voltage signal for detecting any reduction of the first alternating DC voltage signal, and provided the measuring level of the first alternating DC voltage signal being below the first short circuit voltage signalling detection level, the first short circuit voltage signalling detection level being set below the measuring level of the first alternating DC voltage. The two-wire controlling and monitoring system in the ninth aspect further comprises a fourth time frame being defined in the second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within the fourth time frame the controller and power supply unit measuring a measuring level of the second alternating DC voltage signal for detecting any reduction of the second alternating DC voltage signal, and provided the measuring level of the second alternating DC voltage signal being below the second short circuit voltage signalling detection level, the second short circuit voltage signalling detection level being set below the measuring level of the second alternating DC voltage signal.

According to the basic realisation of the ninth aspect of the present invention during the third time frame the controller and power supply unit not transmitting the schedules of instructions to the third plurality of localised irrigation control units and during the fourth time frame the controller and power supply unit not transmitting the schedules of instructions to the third plurality of localised irrigation control units.

According to the basic realisation of the ninth aspect of the present invention the controller and power supply unit subsequently apply during the first and second alternating DC voltage signals the first and second short circuiting voltage signalling detection levels.

According to the basic realisation of the ninth aspect of the present invention the two-wire controlling and monitoring system further comprises a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and the third plurality of localised irrigation control units further comprising a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, and the sensor decoders further each having a pair of control and power supply inputs.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a tenth aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area of the localised areas controlled by the controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, the sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, and a third time frame being defined in the first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within the third time frame the controller and power supply unit measuring a measuring level of the first alternating DC voltage signal for detecting any reduction of the first alternating DC voltage signal, and provided the measuring level of the first alternating DC voltage signal being below the first short circuit voltage signalling detection level, the first short circuit voltage signalling detection level being set below the measuring level of the first alternating DC voltage signal.

The two-wire controlling and monitoring system in the tenth aspect further comprises a fourth time frame being defined in the second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within the fourth time frame the controller and power supply unit measuring a measuring level of the second alternating DC voltage signal for detecting any reduction of the second alternating DC voltage signal, and provided the measuring level of the second alternating DC voltage signal being below the second short circuit voltage signalling detection level, the second short circuit voltage signalling detection level being set below the measuring level of the second alternating DC voltage signal.

According to the basic realisation of the tenth aspect of the present invention during the third time frame the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units and during the fourth time frame the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units.

According to the basic realisation of the tenth aspect of the present invention the controller and power supply unit subsequently applying during the first and second alternating DC voltage signals the first and second short circuiting voltage signalling detection levels.

According to the basic realisation of the tenth aspect of the present invention the third plurality of localised irrigation control units each further comprises a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to an eleventh aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area controlled by the controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, a first time frame being defined in the first alternating DC voltage signal, within the first time frame of a first occurring first alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to a first short circuiting current detection level and measuring any reduction of the first alternating DC voltage signal, and within the first time frame of a succeeding first alternating DC voltage signal the controller and power supply unit increasing the first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of the first alternating DC voltage signal, a second time frame being defined in the second alternating DC voltage signal, within the second time frame of a first occurring second alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to the increased first short circuiting current detection level and measuring any reduction of the second alternating DC voltage signal, and within the second time frame of a succeeding second alternating DC voltage signal the controller and power supply unit increasing the increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of the second alternating DC voltage signal, a third time frame being defined in the first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within the third time frame the controller and power supply unit measuring a measuring level of the first alternating DC voltage signal for detecting any reduction of the first alternating DC voltage signal, and provided the measuring level of the first alternating DC voltage signal being below the first short circuit voltage signalling detection level, the first short circuit voltage signalling detection level being set below the measuring level of the first alternating DC voltage signal, and a fourth time frame being defined in the second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within the fourth time frame the controller and power supply unit measuring a measuring level of the second alternating DC voltage signal for detecting any reduction of the second alternating DC voltage signal, and provided the measuring level of the second alternating DC voltage signal being below the second short circuit voltage signalling detection level, the second short circuit voltage signalling detection level being set below the measuring level of the second alternating DC voltage signal.

According to the basic realisation of the eleventh aspect of the present invention during the first and second time frames the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units and during the third and fourth time frames the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units.

According to the basic realisation of the eleventh aspect of the present invention the controller and power supply unit subsequently apply during the first and second alternating DC voltage signals the increased first short circuiting current detection level, the second short circuiting current detection level, and the first and second short circuit voltage signalling detection levels.

According to the basic realisation of the eleventh aspect of the present invention, the two-wire controlling and monitoring system further comprises a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and the third plurality of localised irrigation control units further comprising a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, and the sensor decoders further each having a pair of control and power supply inputs.

The above object, the above advantage and the above feature together with numerous other objects, advantages and features which will be evident from the below detailed description of a preferred embodiment of the present invention is according to a twelfth aspect of the present invention obtained by a two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to the localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of the localised areas of soil, communicating with the water pipeline, providing watering of the specific area of the localised areas controlled by the controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of the localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to the pair of sensor outputs of a specific field sensor of the second plurality of field sensors for providing power to the second plurality of field sensors and recording the specific irrigation parameters from the second plurality of field sensors, the sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of the pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to the first alternating DC voltage signal to another of the pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to the pair of control and power outputs, a two-wire cable interconnecting the controller and power supply unit and the third plurality of localised irrigation control units and connecting the pair of control and power outputs of the controller and power supply unit to the control and power inputs of the third plurality of localised irrigation control units and providing the power from the controller and power supply unit to each of the third plurality of localised irrigation control units, the controller and power supply unit transmitting the schedules of instructions to the third plurality of localised irrigation control units through the two- wire cable and receiving the specific irrigation parameters from the third plurality of localised irrigation control units through the two-wire cable, a first time frame being defined in the first alternating DC voltage signal, within the first time frame of a first occurring first alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to a first short circuiting current detection level and measuring any reduction of the first alternating DC voltage signal, and within the first time frame of a succeeding first alternating DC voltage signal the controller and power supply unit increasing the first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of the first alternating DC voltage signal, a second time frame being defined in the second alternating DC voltage signal, within the second time frame of a first occurring second alternating DC voltage signal, the controller and power supply unit reducing the alternating DC current to the increased first short circuiting current detection level and measuring any reduction of the second alternating DC voltage signal, and within the second time frame of a succeeding second alternating DC voltage signal the controller and power supply unit increasing the increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of the second alternating DC voltage signal, a third time frame being defined in the first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within the third time frame the controller and power supply unit measuring a measuring level of the first alternating DC voltage signal for detecting any reduction of the first alternating DC voltage signal, and provided the measuring level of the first alternating DC voltage signal being below the first short circuit voltage signalling detection level, the first short circuit voltage signalling detection level being set below the measuring level of the first alternating DC voltage signal, and a fourth time frame being defined in the second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within the fourth time frame the controller and power supply unit measuring a measuring level of the second alternating DC voltage signal for detecting any reduction of the second alternating DC voltage signal, and provided the measuring level of the second alternating DC voltage signal being below the second short circuit voltage signalling detection level, the second short circuit voltage signalling detection level being set below the measuring level of the second alternating DC voltage signal.

According to the basic realisation of the twelfth aspect of the present invention during the first and second time frames the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units and during the third and fourth time frames the controller and power supply unit does not transmit the schedules of instructions to the third plurality of localised irrigation control units.

According to the basic realisation of the twelfth aspect of the present invention the controller and power supply unit subsequently apply during the first and second alternating DC voltage signals the increased first short circuiting current detection level, the second short circuiting current detection level, and the first and second short circuit voltage signalling detection levels.

According to the basic realisation of the twelfth aspect of the present invention the third plurality of localised irrigation control units each further comprises a line decoder having a pair of valve control outputs connected to the pair of valve control inputs of a specific controllable irrigation valve of the first plurality of controllable irrigation valves for providing valve control signals to the first plurality of controllable irrigation valves, the line decoders further each having a pair of control and power supply inputs.

According to the basic realisation of the twelfth aspect of the present invention the voltage maximum is in a range from +10V to +20V, such as ranges +13V to +19V or +14V to +17V, or preferable the voltage maximum is +15V and/or wherein the voltage minimum in a range from -15V to -25V, such as ranges -17V to -23V and - 19V to -21V, or preferable the voltage minimum is -20V.

According to the basic realisation of the twelfth aspect of the present invention the first alternating DC voltage signal and the second alternating DC voltage signal during the first pulse width and the second pulse width averages voltages greater than or equal to zero voltage or wherein the first alternating DC voltage signal and the second alternating DC voltage signal during the first pulse width and the second pulse width averages voltages less than or equal to zero voltage and/or wherein the first alternating DC voltage signal and the second alternating DC voltage signal averages during the first pulse width and the second pulse width an average voltage in the range -5V to -0.5V such as ranges -4V to -1 V or -2.5V to -1.5V, or preferably the average voltages are -2V.

Brief description of the drawings

Fig. 1 shows a schematic overview of the two-wire controlling and monitoring system according to the preferred embodiment of the present invention. Fig. 2 shows in perspective a localised irrigation control unit according to the preferred embodiment of the present invention and interconnecting a two-wire cable and a controllable irrigation valve in communication with a water pipeline, and the localised irrigation control unit further being connected to a field sensor.

Fig. 3 shows alternating DC voltage signals versus time provided from a controller and power supply unit on the two-wire cable to at least one of the localised irrigation control units.

Fig. 4 shows alternating DC current signal versus time applied by the controller and power supply unit on to the two-wire cable and received by at least one of the localised irrigation control units.

Fig. 5 shows a control voltage signal versus time provided by a line decoder in one of the localised irrigation control units to one of the controllable irrigation valves.

Fig. 6 shows a transmission of schedules of instructions provided by the controller and power supply unit to the localised irrigation control units.

Fig. 7 shows an example of the contents of a transmission from the controller and power supply unit to the localised irrigation control units.

Fig. 8 shows a alternating DC voltage line signal transmitted on one conductor of the two-wire cable and corresponding alternating DC current signal between conductors of the two-wire cable.

Fig. 9 shows a differential voltage signal between conductors of the two-wire cable and the corresponding two alternating DC voltage line signals.

Fig. 10 shows a transmission of a type declaration followed by a sequence of binary 'Ts including an answer window. Fig. 11 shows a circuit diagram of the presently preferred embodiment of a sensor decoder.

Fig. 12 shows a circuit diagram of the presently preferred embodiment of a line decoder having one valve control output.

Fig. 13 shows a circuit diagram of the presently preferred embodiment of a line decoder having at least one valve control output.

Figs. 14a and 14b show a circuit diagram of a microprocessor and storage section included in a controller and power supply unit according to a preferred embodiment of the present invention.

Figs. 15a and 15b show a circuit diagram of a power output stage included in a controller and power supply unit according to a preferred embodiment of the present invention.

Figs. 16a and 16b show a circuit diagram of a mark sender according to a preferred embodiment of the present invention.

Figs. 17a - 17c show alternating DC voltage signals versus time illustrating a first and presently preferred technique of transmission of acknowledgement or not- acknowledgement signals from an intentional receiving decoder to the controller and power supply unit after transmission of a schedule of instructions from the controller and power supply unit to the intentional receiving decoder.

Figs. 18a - 18c show alternating DC voltage signals versus time illustrating a second and alternative technique of transmission of acknowledgement or not- acknowledgement signals from an intentional receiving decoder to the controller and power supply unit after transmission of a schedule of instructions from the controller and power supply unit to the intentional receiving decoder.

Fig. 19 shows a principle diagram of the controller and power supply unit supplying a DC voltage to the two-wire cable.

Fig. 20 shows a non-compensated system where leak currents is no problem.

Fig. 21 shows a compensated system where leak currents is a problem.

Fig. 22 shows a compensated system where leak currents are compensated for by means of current compensation.

Fig. 23 shows a compensated system where leak currents are compensated for by means of voltage compensation.

Fig. 24 shows a circuit diagram implementing current compensation.

Fig. 25 shows a circuit diagram implementing voltage compensation.

Detailed description of the present invention

The two-wire controlling and monitoring system designated by numeral 10 in its entirety and shown in Fig. 1, provides irrigation of localised areas e.g. a golf course having certain areas needing a particular amount of irrigation and others a smaller amount of irrigation, parks having tree sections, lawns or flower beds all needing particular amounts of irrigation, greenhouse production lines having a series of production steps for plants, flowers or vegetables all needing a particular amount of irrigation or farming fields having a variety of produce needing a variety of amounts of irrigation.

The two-wire controlling and monitoring system 10 has an inlet connection 12 supplying water from a general household water pump station or a water tank to a pump 14. The pump 14 is mechanically, pneumatically, hydraulically, electrically or magnetically driven or driven by combinations thereof and provides a water pressure on a water pipeline 16 enabling the water pipeline 16 to supply water to a plurality of localised irrigation control units 18 positioned at a series of localised areas of soil 20.

The water pipeline 16 may be constructed from metal pipes produced in materials such as iron, steel, copper, aluminium, silver, gold or any alloys thereof and/or plastic pipes produced in materials such as PVC, PP or PE or any combinations thereof.

The localised irrigation control units 18 are positioned at the series of localised areas of soil 20 and provides irrigation to specific areas of each of the localised areas of soil 20 through a plurality of local pipelines 22 possibly mounted with sprinkling gadgets 24. The localised irrigation control units 18 utilises connections 40 and the pump 14 utilises connections 26 to communicate through a two-wire cable 28 interconnecting a controller and power supply unit 30 with the plurality of localised irrigation control units 18 and the pump 14. The controller and power supply unit 30 transmits power and schedules of instructions to the plurality of localised irrigation control units 18.

The controller and power supply unit 30 comprises a keyboard 32 for a user to communicate schedules of instructions i.e. controlling timing of irrigation and position of irrigation to be stored and executed by a computer 34. The controller and power supply unit 30 further comprises a monitor 36 for displaying the operation of the two-wire controlling and monitoring system 10 and a printer 38 for printing out information from the computer 34. The computer 34 may include a an internal or external modem through which remotely monitoring and controlling of the computer 34 is achieved and thereby remotely monitoring and controlling of the controller and power supply unit 30. The computer 34 may further have access to internet facilities which similarly provides the possibility for remotely monitoring and controlling of the computer 34 and thereby the controller and power supply unit 30. Additionally, a series of computers for example operating irrigation monitoring and controlling systems like the computer 34 may be monitored and controlled from a central unit located at any position world-wide hooked up to the internet or connecting to the series of computers through use of modems. The localised irrigation control units 18 are situated in a house or cabinet 46, shown in Fig. 2, made of a wear resistant material such as metals like aluminium or steel or plastics like PVC, PP or PE. The house 46 protects the localised irrigation control units 18 from any hostile environment the house is positioned in.

Each of the localised irrigation control units 18, as shown in Fig. 2, may comprise a controllable irrigation valve 42 controlling release of water from the water pipeline 16 and a line decoder 44 transmitting the necessary schedules of instructions to the controllable irrigation valve 42.

The controllable irrigation valve 42 may be magnetically, electrically, hydraulically or pneumatically operated or combinations thereof, however, according to the presently preferred embodiment of the invention the controllable irrigation valve 42 is electrically operated through connectors placed in a connector box 48 in the house 46. The connector box 48 comprises a solenoid, which controls the valve in an open or closed position. Variations of current applied to the solenoid causes the induction of magnetic fields, which subsequently activate the valve.

The line decoder 44 receives transmissions of schedules of instructions from the controller and power supply unit 30 through the two-wire cable 28. A pair of control and power inputs 40 connects the line decoder 44 to the two-wire cable 28. A pair of valve control outputs 50 connects the connector box 48 to the line decoder 44. The line decoder 44 applies control signals 100 to the connector box 48 through the pair of valve control outputs 50, which control signals 100, described in further detail below with reference to Fig. 5, are further communicated by the connector box 48 to the controllable irrigation valve 42. Alternatively the line decoder 44 may receive start instructions through radio transmissions produced by a mobile handhold mark sender providing the opportunity to initiate irrigation at specific localised areas regardless of schedules of instructions. This enables manual control of the controllable irrigation valves 42.

The localised irrigation control unit 18 further comprises a sensor decoder 52, as shown in Fig. 1 and 2, recording a specific irrigation parameter from a field sensor 54 through a pair of sensor outputs 56 and providing a conversion of the specific irrigation parameter measured by the field sensor 54 to a binary number and additionally performing a transmission of the binary number to the controller and power supply unit 30. The sensor decoder 52 id connected to the two-wire cable 28 through a pair of control and power inputs 58. The specific irrigation parameters may be soil or air temperature, soil or air humidity, water pressure in the water pipeline 16, water flow in the water pipeline 16 or water flow through one of the controllable irrigation valves 42. Furthermore the specific irrigation parameters may be mechanical movement, mechanical strain or magnetic fields which may be utilised for the determination of the functionality or operation of the controllable irrigation valves 42.

The line decoder 44 and the sensor decoder 52 receive power through the two-wire cable 28 from the controller and power supply unit 30. Fig. 3 shows voltage versus time curves of a first alternating DC voltage signal, designated by LA, and a second alternating DC voltage signal, designated by LB, simultaneously provided by the controller and power supply unit 30 to the two-wire cable 28 for powering of the line decoder 44 and the sensor decoder 52.

The first alternating DC voltage signal LA has a positive pulse with a pulse width 64 in the range 450ms to 550ms and a negative pulse with a pulse width 66 in the range 450ms to 550ms. In the presently preferred embodiment of the invention the pulse width 64 is substantially equal to 500ms, and the pulse width 64 and the pulse width 66 are substantially equal.

The first alternating DC voltage signal LA has a maximum voltage 146 in the range of +10V to +20V and has a minimum voltage 148 in the range of -15V to -25V. In the presently preferred embodiment of the invention the maximum voltage 146 is +15V and the minimum voltage 148 is equal to -20V.

The first alternating DC voltage signal LA is symmetrical about a line 142 indicating a negative off set voltage of the first alternating DC voltage signal LA, in the presently preferred embodiment of the invention the off set voltage is approximately -2V.

The second alternating DC voltage signal LB is inverted in comparison with the first alternating DC voltage signal LA and has a negative pulse with a pulse width 68 in the range 450ms to 550ms and a positive pulse with a pulse width 70 in the range 450ms to 550ms. In the presently preferred embodiment of the present invention the pulse width 68 is substantially equal to 500ms and the pulse width 64, the pulse width 66, the pulse width 68 and the pulse width 70 are substantially equal.

The term inverted in this context means a phase shift between the first .alternating DC voltage signal LA and the second alternating DC voltage signal LB of approximately 180°.

The second alternating DC voltage signal LA has a maximum voltage 60 in the range of +10V to +20V and has a minimum voltage 62 in the range of -15V to - 25V. In the presently preferred embodiment of the invention the maximum voltage 60 is equal to the maximum voltage 146 of the first alternating DC voltage signal LA, and the minimum voltage 62 is equal to the minimum voltage 148 of the first alternating DC voltage signal LA.

The second alternating DC voltage signal LA is symmetrical about a line 144, which line 144 indicates a negative off set voltage of the second alternating DC voltage signal LB. In the presently preferred embodiment of the invention the off set voltage of the second alternating DC voltage signal is approximately equal to the off set voltage of the first alternating DC voltage signal.

By off setting the first and the second alternating DC voltage signals LA, LB with a negative voltage relative to ground 140 a substantially slower corrosion of the two- wire cable 28 is achieved. In case of negative off set, the current will run from the ground level 140 to copper material of the two-wire cable 28 resulting in an alkaline process, which is less hazardous to the copper material than an electron acceptor donating process relative to ground level 140, achieved in case of positive off set forcing the current to run from the copper material to the ground level 140. Fig. 4 shows a current versus time curve of an alternating DC current signal 80 provided by the controller and power supply unit 30 between the wires of the two- wire cable 28. The alternating DC current signal 80 has a maximum current 78 in the range of 0.5A to 2A, and has a minimum current 76 in the range of 2OmA to 15OmA. In the presently preferred embodiment of the invention the maximum current 78 is 1.1 A and the minimum current 76 is 40mA.

The alternating DC current signal 80 furthermore has a pulse width 72 defining the period of minimum current 76 of the alternating DC current signal 80, which pulse width 72 is in the range 0.1ms to 10ms, and has a pulse width 74 defining the period of maximum current 78 of the alternating DC current signal 80. In the presently preferred embodiment of the invention the pulse width 72 is shorter than 5ms and the pulse width 74 is lesser than 500ms. The length of the pulse width 74 is depending on which operation is performed by the controller and power supply unit 30. In case of an Arbitration or data transferring transmission consisting of a series of binary "1"s then the pulse width 74 is shorter than 20ms. During normal operation the pulse width 74 however, is shorter than 500ms.

Fig. 5 shows a voltage versus time curve of the control signal 100 provided by the line decoder 44 to the controllable irrigation valve 42. The control signal 100 consists of an inrush signal 102 and a hold signal 104. The inrush signal 102 provides a maximum voltage 82 for operating the controllable irrigation valve 42 in an open position enabling water to flow from the water pipeline 16 to the local pipeline 22 positioned in the localised areas 20. The inrush signal 102 defines a pulse width 88 in the range 10ms to 1s in the presently preferred embodiment of the invention the pulse width 88 is in the range 30ms to 100ms. When the controllable irrigation valve 42 is completely opened, the line decoder 44 changes the control signal 100 from the inrush signal 102 to the hold signal 104. The hold signal 104 has a reduced maximum voltage 84. The line decoder 44 continues to transmit the hold signal 104 as long as dictated by the schedules of instructions. As soon as the control signal is turned off 106 providing ground voltage 86 to the controllable irrigation valve 42, the controllable irrigation valve 42 closes and thereby disables the flow of water from the water pipeline 16 to the local pipeline 22.

In order to reduce power consumption of the controllable irrigation valves 42 the control signal 100 in the presently preferred embodiment of the invention is construed from a series of square wave pulses 114 constituting an pulsed inrush signal 110 and constituting a pulsed hold signal 112. The square wave pulse 114 defines a voltage maximum 92 having a pulse width 94 and defines a voltage minimum 90 having a pulse width 96 in the pulsed inrush signal 110 and defines the voltage maximum 92 having a pulse width 99 and defines the voltage minimum 90 having a pulse width 98 in the pulsed hold signal 112. According to a first embodiment of the present invention the pulse width 94 and the pulse width 96 and the pulse width 99 are 1ms, but may be any value in the range 100μs to 0.1s. The pulse width 98 is 10ms, but may be any value in the range 6ms to 30ms. The average voltage of the pulsed inrush signal 110 is equal to the maximum voltage 82 of the inrush signal 102 and the average voltage of the pulsed hold signal 112 is equal to the reduced maximum voltage 84 of the hold signal 104. According to a second and presently preferred embodiment of the invention and as shown in Fig. 5 the sum of the pulse widths 94 and 96 and the sum of the pulse widths 98 and 99 are 1ms, but may be any value in the range 100μs to 0.1s. During the pulsed inrush signal 110 the pulse width 94 is substantially larger than the pulse width 96 thereby constituting an average voltage of the pulsed inrush signal 110 equal to the maximum voltage 82 of the inrush signal 102. During the pulsed hold signal 112 the pulse width 98 is substantially smaller than the pulse width 99 thereby constituting an average voltage of the pulsed hold signal 112 equal to the reduced maximum voltage 84 of the hold signal 104.

The maximum voltage 92 of the control signal 100 in the presently preferred embodiment of the invention is 35V, but may have any value in the range 5V to 45V. The minimum voltage 90 of the control signal 100 in the presently preferred embodiment of the invention is OV equal to ground level 86, but may be in the range OV to δV.

The controller and power supply unit 30 transmits schedules of instructions simultaneously to transmitting power through the two-wire cable 28 to the line decoder 44. The schedules of instructions are transmitted to the irrigation control units 18 in a sequential binary pattern 118 construed from alternations or toggling of the first alternating DC voltage signal LA and the second alternating DC voltage signal LB. Fig. 6 shows a voltage versus time curve 116 having a normal pattern 126 where the first alternating DC voltage signal LA has the pulse width 64, the maximum voltage 146 and minimum voltage 148 and having the binary pattern 118. The sequential binary pattern 118 is provided by simultaneous alternations of the first alternating DC voltage signal LA and the second alternating DC voltage signal LB. Fig. 6 shows only the first alternating DC voltage signal for simplicity.

The binary pattern 118 defines a binary "1"s by having a pulse width 120 in the range 10ms to 49ms and defines a binary "0"s by having a pulse width 122 in the range 1ms to 9ms. In the presently preferred embodiment of the invention the pulse width 120 defining binary "1" is 20ms and the pulse width 122 defining binary "0" is approximately 5ms.

A transmission of the binary pattern 118 is concluded by a pulse width 124 defining a stop signal in the range of 50ms to 70ms. In the presently preferred embodiment of the invention the pulse width 124 is 60ms.

The transmission of schedules of instructions in the form of the binary pattern 118 from the controller and power supply unit 30 to the irrigation control unit 18, is shown as an example in Fig. 7 and according to the presently preferred embodiment of the invention the transmission consists of type declaration 128 defining the type of operation needed by the irrigation control unit 18. In the presently preferred embodiment of the invention type declarations may be "Arbitration" used for prioritising functions, "Data" used for transmitting data to the irrigation control unit 18, "Control" used for switching line decoders 44 in the irrigation control units 18 on and off, "Broadcast" used for transmission of data to all irrigation control units 18 in the two-wire controlling and monitoring system 10, "Test" used for testing the functionality of one of the irrigation control units 18 and "Pole" used for extracting specific irrigation parameters from one of the sensor decoders 52 in the irrigation control units 18.

Depending on which type declaration 128 is transmitted the binary pattern 118 may further consist of an address 130 having a transmission size in the range 0 128 bits, data having a transmission size in the range of 0 to IGbits, a first check having a transmission size in the range of 0 to 128 bits, a second check having a transmission size in the range of 0 to 128 bits and finally the transmission is concluded by the stop signal defined by the pulse width 124. In the presently preferred embodiment of the invention the type declaration consists of 4 bits, the address consists of 16 bits, the data consists of up to 64KBYTE (1 BYTE equal to 1024 bits), the first check consists of 4 bits and the second check consists of 4 bits.

Fig. 8 shows a voltage versus time curve of the first alternating DC voltage signal LA and simultaneously a curve of current versus time of the alternating DC current signal 80. During the positive pulse having the pulse width 64 the controller and power supply unit 30 provides an interrupt window 154 during which the alternating DC current signal applies the minimum current 76 to the two-wire cable 28 until an interrupt from the irrigation control units 18 is detected. The pulse width 72 of the minimum current 76 part of the alternating DC current signal 80 determines the interrupt window's 154 active time period. In the presently preferred embodiment of the invention the active time period of the interrupt window is shorter than 5ms. The precise length of the pulse width 72 is determined according to detection by the controller and power supply 30 of an interrupt from the irrigation control units 18. As soon as an interrupt is detected during the interrupt window 154 the DC alternating current signal shifts state and provides maximum current 78 to the two-wire cable.

The interrupt window 154 follows an alternation 150 of the first alternating DC voltage signal LA and a power active time period 152. In the presently preferred embodiment of the invention the power active time period 152 is 400ms.

The sensor decoder 52 comprises a short circuiting circuit for unidirectional short circuiting the pair of control and power inputs 58. The sensor decoder 52 may request an interrupt of the two-wire controlling and monitoring irrigation system 10 by unidirectional short circuiting the pair of control and power inputs 58 during the interrupt window 154 and hence provide a voltage drop 158 of a differential voltage 156 between the first alternating DC voltage signal LA and the second alternating DC voltage signal LB, shown in Fig. 9. Fig. 9 shows a voltage versus time curve of the differential voltage 156 during transmission of the request of an interrupt. In the presently preferred embodiment of the invention the maximum voltage of the differential voltage 156 is in the range 25V to 45V or preferably 35V and during the request of an interrupt the differential voltage may drop to a value in the range 15V to 30V. However, in the presently preferred embodiment of the invention the differential voltage may drop to a maximum of 25V or to a voltage of -1 OV relative to ground voltage.

Fig. 9 furthermore shows voltage versus time curves of the first alternating DC voltage signal LA and the second alternating DC voltage signal LB during the request for an interrupt. As Fig. 9 shows, during the request of an interrupt performed in the interrupt window 154 the voltage difference between the first alternating DC voltage signal LA and the second alternating DC voltage signal LB is significantly reduced, which reduction is detected by the controller and power supply unit 30. In response to the request of an interrupt the controller and power supply unit 30 performs an alternation 160 of the first alternating DC voltage signal LA and the second alternating DC voltage signal LB and performs a shift in state of the DC alternating current signal 80 from minimum current 76 to maximum current 78. Since the short circuiting is unidirectional the effect of the short circuit is avoided following the DC alternation of the first alternating DC voltage signal LA and the second alternating DC voltage signal LB. At the same time the DC alternation indicates to the plurality of irrigation control units 18 that the controller and power supply unit 30 has received an interrupt from one of the plurality of irrigation control units 18 and therefor the plurality of irrigation control units 18 are prepared for the controller and power supply unit's 30 initiation of a transmission 162 of the type declaration "Arbitration" on the two-wire cable 28.

Fig. 10 shows a curve of the second alternating DC voltage signal LB transmitting the transmission 162 comprising a type declaration. If the type declaration transmitted is "Arbitration" then the controller and power supply unit 30 continues it's transmission by applying a series of binary "1"s 168 to the two-wire cable 28 in order to obtain an address of the interrupting irrigation control unit 18 having the lowest address. Each of these binary "1"s include an answer window 166 during which the minimum current 76 is applied to the two-wire cable 28. If at least one of the interrupting irrigation control units 18 during the first answer window 166 performs a unidirectional short circuiting of the pair of control and power inputs 58, then the controller and power supply unit 30 interprets the resulting voltage drop as a binary "0" indicating that the most significant bit of the address of the at least one of the interrupting irrigation control units 18 is "0". On the other hand if none of the interrupting irrigation units 18 perform a short circuiting of the pair of control and power inputs 58 during the answer window 166, then the controller and power supply unit 30 interprets a binary "1" indicating that the most significant bit of the addresses of all of the interrupting irrigation control units 18 is "1". Subsequently the controller and power supply unit 30 initiates transmission of a second binary "1 " including a second answer window 166 by performing a new alternation of the first alternating DC voltage signal LA and the second alternating DC voltage signal LB and applies the maximum current 78 to the two-wire cable 28. This process is repeated until the controller and power supply unit 30 has located the interrupting irrigation control unit 18 having the lowest address. In effect the interrupting irrigation control units 18 answer "yes" or "no" to the transmission of the series of binary "1"s 168 in accordance with the interrupting irrigation control units' 18 own address. When the controller and power supply unit 30 has identified for example the interrupting sensor decoder 52 by detecting the sensor decoder's 52 answers in the answer window 166, then the controller and power supply unit 30 continues a new transmission of binary "1"s including answering windows 166 for the interrupting sensor decoder 52 to transmit data from the sensor decoder 52 to the controller and power supply unit 30 by answering "yes" or "no".

Similar communication techniques as described above between the controller and power supply unit 30 and the individual irrigation control units 18 is utilised during the controller and power supply unit's 30 request for data from the irrigation control units 18 and during any type declaration in which obtaining information from the irrigation control units 18 is required.

Voltage drops outside a designated interrupt window 154 or answer window 166 or voltage drops below an acceptable voltage minimum during such a window (154, 166) may be due to erroneous equipment. Thus voltage drops further may show if the two-wire controlling and monitoring system has faulty equipment. Alternatively, the controller and power supply unit 30 may establish a separate test window in both high and low pulses of both the first alternating DC voltage signal LA and the second alternating DC voltage signal LB. The test window may be initiated following a toggle or alternation of the first and second alternating DC voltage signal LA and LB. According to one embodiment of the present invention the test window is initiated 100ms following a specific pre-selected alternation and has a length of 10ms. By reducing the alternating DC current signal 80 to minimum current 76 during the test window erroneous signalling from the irrigation control unit 18 is avoided.

In the presently preferred embodiment of the invention the alternating DC current signal 80 during the answer window 166 is reduced to the minimum current 76, which minimum current 76 lasts for the pulse width 72. The length of the pulse width 72 is determined in accordance with the earliest response from one of the answering irrigation control units 18 and limited to a having a maximum length of 2.5ms. The answer window 166 during a transmission of a series of binary "1"s is initiated following a non-active time period of approximately 5ms.

Generally speaking the communication between the controller and power supply unit 30 and the irrigation control units 18 is implemented by utilising a unidirectional short circuiting circuit in the irrigation control units 18 for transmitting an interrupt request to the controller and power supply unit 30 and for transmitting answers to the controller and power supply unit 30. The reaction of the controller and power supply unit 30 is immediate alternation and consequently a shorter time having minimum current 76 applied to the two-wire cable 28. Even if the reaction of the controller and power supply unit 30 during the process of obtaining information from the irrigation control units 18 during the answer windows 166 is not restricted in the sense that a binary "0" must be 5ms but rather that a binary "0" is indicated entirely by a short circuiting signal from the irrigation control units 18 at any moment within the answer window. However, the faster the short circuiting signal is detected by the controller and power supply unit the better the power transfer to the irrigation control units 18 becomes.

The two-wire controlling and monitoring system 10 may be configured in a variety of ways. The presently preferred embodiment of the electronics of the two-wire controlling and monitoring system 10 is shown in Figs. 11 to 16.

Fig. 11 shows a circuit diagram of the presently preferred embodiment of the sensor decoder 52. The circuit diagram shows the short circuiting circuit 170, a control and power supply input section 186 having pair of control and power supply inputs designated by Line-A and Line-B, a constant voltage supply 172, a microprocessor 174 and a field sensor power supply and field sensor signal amplifier 176.

The short circuiting circuit 170 comprises a differential amplifier monitoring polarity of the lines Line-A and Line-B and communication information regarding polarity of the lines Line-A and Line-B to the microprocessor 174. The short circuiting circuit 170 further comprises two transistors for unidirectional short circuiting of the lines Line-A and Line-B. The transistors are controlled by the microprocessor 174 and operated to open or close during interrupt windows 154 and answering windows 166.

The control and power supply input section 186 provides an electrical separation between the two-wire cable 28 and the sensor decoder 52. This is achieved by employing bridge circuitry in combination with a reservoir capacitor. During interrupt windows 154 and answering windows 166 the current supplied to the two-wire cable 28 is significantly reduced and therefor in order to keep the sensor decoder functioning during these short periods the reservoir capacitor supplies the current needed for operating the sensor decoder 52.

Fig. 12 shows a circuit diagram of the presently preferred embodiment of the line decoder 44 having one valve control output. The circuit diagram shows a control and power supply input section 186 having pair of control and power supply inputs designated by LA and LB, a microprocessor 178 and an output power stage 180 for operating the controllable irrigation valves 42 to open and closed positions.

Fig. 13 shows a circuit diagram of the presently preferred embodiment of the line decoder 44 having at least one valve control output. The circuit diagram shows the microprocessor 178 and a plurality 182 of the power output stage 180 for operating a series of the controllable irrigation valves 42 to open and closed positions.

Similarly to the circuit diagram for the sensor decoder 52 depicted in Fig. 11 the line decoder 44 shown in Fig. 12 and the line decoder shown in Fig. 13 comprise power supply input sections 186 electrically separating the two-wire cable 28 from the internal circuitry of the line decoders 44 in Figs. 12 and 13. The power supply input section 186 consists of a bridge circuit and a reservoir capacitor.

Figs. 14a and 14b show a circuit diagram of a controller section of the presently preferred embodiment of the controller and power supply unit 30.

Figs. 15a and 15b show a circuit diagram of power supply section of the presently preferred embodiment of the controller and power supply unit 30.

Figs. 16a and 16b show a circuit diagram of a mark sender for transmitting start information to the controllable irrigation valves 42 irrespective of the controller and power supply unit's 34 schedules of instructions. The mark sender provides the opportunity for manually control the controllable irrigation valves 42 to open or close and thereby provide an operator the possibility to manually adjust the irrigation during inspection of for example a golf course.

In the above described two-wire controlling and monitoring system, the controller and supply unit 30 supplies a specific schedule of instructions to the two-wire cable 28 for addressing a specific decoder. After the transmission of the specific schedule of instructions to the intentional receiver of the schedule of instructions being a specific decoder, the controller and power supply unit has to carry out the above described "arbitration" in order to obtain information regarding safe receipt of the schedule of instructions and also regarding the performance of the instruction, i.e. information relating to the decoder performing the intentional action or not performing the intentional action. Provided all instructions are to be verified by the above "arbitration", app. 50% of the information band which will be used for the recognition and verification of receipt and the performing of a specific instruction. In order to allow a more simple confirmation of receipt, or in the alternative not-receipt of the intentional information or schedule of instructions by a specific intentional receiving decoder, dedicated time frames are included in the transmission window as is illustrated in Figs. 17a - 17c and 18a - 18c.

In Fig. 17a, a conventional transmission of a schedule of instructions 118 by the alternating of the DC power supply output is shown which alternating periods have a duration of 100-400 ms.

After the transmission of the specific schedule of instructions, the stop signal represented by the pulse 124 is transmitted indicating to the receiving decoders the termination of the transmission of a schedule of instructions. The stop signal 124 shown in Fig. 17a has duration of 60 ms. and is terminated by a reversal of the polarity of the signals of the two-wire cable. Within the next full period designated the reference numeral 119, a pause is established for the initial 200 ms. allowing any transients or disturbances to be eliminated or to die out. In the 200 ms. pause, two time frames designated reference numerals 72' and 72" representing the supply of minimum current from the controller and power supply unit to the two-wire cable are indicated in Fig. 17a within which time frames a not-acknowledgement signal shown in Fig.17c or an acknowledgement signal shown in Fig. 17b may be transmitted from the intentional receiving decoder to the controller and power supply unit by short circuiting the two-wire cable and doing so establishing the above described signalling to the controller and power supply unit.

According to the diagrams of Figs. 17a - 17c, the not-acknowledgement signal shown in Fig. 17c is transmitted within the time frame 72' app., 100 ms. after the stop signal pulse 124 whereas the acknowledgement signal is transmitted within the time frame 72" app. 120 ms. after the stop signal pulse 124.

Preferably, the not-acknowledgement signal is transmitted prior to the acknowledgement signal for allowing the controller and power supply unit to positively recognise by the receipt of the not-acknowledgement signal that a retransmission has to be made, however, in an alternative embodiment of the signalling technique illustrated in Fig. 17a - 17c, the acknowledgement signal may be transmitted prior to any not-acknowledgement signal allowing the controller and power supply unit to recognise by the receipt of the acknowledgement signal that no retransmission need to be made. At any rate, the controller and power supply unit determines on the basis of the receipt of an acknowledgement signal or a not- acknowledgement signal or no signals at all whether or not a retransmission is to be made. Alternatively, the above time frames 72' and 72" may be changed relative to the overall length of the period 119, i.e. different from the above described 100 ms. and 120 ms.

In Figs. 18a - 18c, a different technique of signalling receipt or not-receipt of a schedule of instructions from an intentional receiving decoder is illustrated. As distinct from the first and presently preferred embodiment of the acknowledgement/ not-acknowledgement technique shown in Fig. 17a - 17c, the technique illustrated in Figs. 18a - 18c includes no specific 60 ms. stop signal pulse 124 as the intentional receiving decoder simply after the transmission of the schedule of instructions 118 starts signalling the not-acknowledgement or the acknowledgement of the schedule of instructions by transmitting the not-acknowledgement signal within the time frame 72' as illustrated in Fig. 18c, app. 160 ms. after the schedule of instructions pulse 118 or, in the alternative, by transmitting the acknowledgement signal within the time frame 72' as illustrated in Fig. 18b after app. 180 ms.

Like the above described first and presently preferred signal and technique described with reference to Fig. 17a - 17c, the occurrence of the acknowledgement and the not-acknowledgement signals may be reversed as the acknowledgement signal may be transmitted within the time frame 72' whereas the not-acknowledge- merit signal may be transmitted within the time frame 72", and the above described periods of 160 ms. and 180 ms. may also be amended.

Generally, the transmission of the acknowledgement or not-acknowledgement signals from the intentional receiving decoder to the controller and power supply unit improves the overall efficiency of the two-wire controlling and monitoring system by reducing the time needed for verifying proper or improper receipt of a schedule of instructions to a single transmission pulse.

In the two-wire controlling and monitoring system, the acknowledgement or not- acknowledgement signalling technique may further be employed for additional signalling purposes such as signalling from a sensor decoder the correspondence or lack of correspondence between the intentional state of a unit or an entity monitored by the sensor decoder, and the actual state of the unit or entity monitored by the sensor decoder such as e.g. the state of a valve or a pump.

In the above described two-wire controlling and monitoring system, the controller and supply unit 30 supplies a specific schedule of instructions to the two-wire cable 28 for addressing a specific decoder. After the transmission of the specific schedule of instructions to the intentional receiver of the schedule of instructions being a specific decoder, the controller and power supply unit has to carry out the above described "arbitration" in order to obtain information regarding safe receipt of the schedule of instructions and also regarding the performance of the instruction, i.e. information relating to the decoder performing the intentional action or not performing the intentional action. Provided all instructions are to be verified by the above "arbitration", app. 50% of the information band which will be used for the recognition and verification of receipt and the performing of a specific instruction. In order to allow a more simple confirmation of receipt, or in the alternative not-receipt of the intentional information or schedule of instructions by a specific intentional receiving decoder, dedicated time frames are included in the transmission window.

In the system discussed with reference to the above figures leak currents between wires in the two-wire cable 28 and the ground in which the cable is placed may occur. Even though leak currents should be avoided, it is not always possible due to "sores" in the cable/wire isolation or non-correct watertight jointing between the cable and the irrigation control unit 18.

When signalling from the controller and power supply unit 30 to the irrigation control unit 18, leak currents are usually not a problem. The leak current works as an extra load on the two-wire system, i.e. on the two-wire cable 28. But when signalling in the other direction, i.e. from the irrigation control unit 18 to the controller and power supply unit 30 leak currents may influence the ability of the controller and power supply unit 30 to interpret the signalling correctly.

Signals sent from one of the irrigation control units 18 intended to be received at the controller and power supply unit 30 as discussed with reference to Figs. 6 and 7 are square shaped with a certain amplitude, however due to the leak currents on the transmission line - with the worst influence on the signals sent from one of the irrigation control units 18 - may deteriorate the signal from the irrigation control units 18 with the result that the signals no longer are as intended, e.g. the amplitude is lowered or pulled down with the result that signals received at the controller and power supply unit 30 are misinterpreted.

Signalling from the irrigation control unit 18 to the controller and power supply unit 30 is performed by the irrigation control unit 18 in special signalling time frames in and during which it is allowed for the irrigation control unit 18 to short-circuit the two-wire cable 28 if the irrigation control unit 18 wants the voltage on the two-wire cable 28 to be shifted in polarity. The controller and power supply unit 30 detects the short circuit and makes the actual polarity shift, also named "toggling". Thereby the irrigation control unit 18 may create a sequence of polarity shifts, which shifts equal a data packet from the irrigation control unit 18 to the controller and power supply unit 30.

The voltage of the two-wire cable 28 is provided, see Fig. 3, where the two-wire cable 28 receives power from the controller and power supply unit 30. The same Fig. shows voltage versus time curves of a first and a second alternating DC voltage signal simultaneously provided by the controller and power supply unit 30, this signal being referred to in the following as the line voltage from a denoted corresponding line voltage generator.

The controller and power supply unit 30 registers the short-circuit from the irrigation control unit 18 by 1) and 2), i.e.:

1) Lowering the current limit for the line voltage generator to a low value in the special signalling time frame, typically the current limit value is 5OmA. The current limit. value has to be relatively low due to - and to avoid - voltage drops in the copper resistance of the two-wire cable 28. The controller and power supply unit 30 controls the current limit for the line voltage generator. A current limiter circuit described with reference to Fig. 19 is connected in series with the line voltage generator supplying e.g. 35 V DC, the level for the max current drawn from the current limiter circuit is adjustable by an internal circuitry of the controller and power supply unit 18.

2) Sensing that the voltage V2_-Wire across the two-wire cable 28 is pulled down under a fixed voltage of 10V in the special signalling time frame. The voltage should be significantly below the minimum voltage of the two-wire cable 28 during full load voltage, e.g. 23-25V. As all irrigation control units 18 by definition have a diode with a condensator circuit towards/against the two-wire cable 28, it may only be an intentional short-circuit which pulls or draws the voltage of the two-wire cable 28 down.

Leak currents in cables work partly as an equivalent of a resistor connected between the two-wires in the two-wire cable 28. If this resistance becomes too small for leak currents, it will as a result pull the two-wire cable 28 line resistance down to a low value in and during the special signalling time and make the controller and power supply unit 30 believe that a polarity shift is desired, which is not intended and is due to the leak current or leak currents.

This causes two problems: the first problem is that the controller and power supply unit 30 will use a part of the its bandwidth to make random signalling, and the second problem: the signalling from the irrigation control unit 18 back to the controller and power supply unit 30 will not be possible, since the signalling is distorted due to leak currents.

For these reasons, according to the implementation of the invention, the leak currents and their effects are to be compensated for as discussed in the following: Leak currents and their influence on the two-wire cable 28 are constant e.g. during a short period of time, for instance 2-10 seconds, at the end of this period or even during this period the system may be considered stable, and the currents may be considered DC currents since no pulses or polarity shifts take place on the two-wire cable 28. When the leak current has been compensated for, signalling on the two- wire cable 28 may take place again. When e.g. another period has passed - or just the short period of time referred to above has passed, leak currents could have changed, which again has to be compensated for.

However, leak currents will be dependent of the two-wire polarity at that occasion because leakage from the individual wire towards the ground is important for the total load on the two-wire cable 28. Therefore the influence of the leak currents in the stable "time frame" is measured by applying a "time frame" during which it is certain that none of the irrigation control units 18 will attempt to signal back to the controller and power supply unit 30, i.e. none of the irrigation control units 18 transmits any parameters, e.g. specific irrigation control parameters to the controller and power supply unit 30. During the time frame no schedules of instructions are sent from the controller and power supply unit 18 to the irrigation control units 18.

Afterwards the leak currents may be attempted compensated out in that the irrigation control unit 18 short-circuit later will respond to a resistance constituted by e.g. the short-circuit condition and the + cable resistance electronics in the irrigation control unit 18 parallel with the known leak current which is now known.

The two methods apply a definition of a voltage detection level V_dete_Ction and a margin Vmar_gin for the voltage detection level. The voltage detection level V_dete_cti_on defines the level for a received parameter from one of the irrigation control units. See for example Figs. 20 and 21 to the left side under "normal communication", where the "shift" indicates that the measured V2-wire voltage level was under the V_detecti_oπ voltage, i.e. a pulled down voltage level was detected being a part of the bits signalling stream from one of the irrigation control units.

The margin Vmargin is seen in relation to Vdetection and is applied -when added to Vdetectioπ as the upper level for Vdetection, and conversely if Vmargin is subtracted from

Vdetection it IS the lOW^βr level for V_detection-

Two different solutions are possible that compensate for the leak current or leak currents, i.e. a method of current compensation and another method applying voltage compensation.

Current compensation method: 1. The controller and power supply unit 30 sets up a "time frame" at a time when it is expected that none of the irrigation control units 18 is responding, i.e. no irrigation control unit 18 signals any parameters back. Further, during the time frame no schedules of instructions are sent from the controller and power supply unit 18 to the irrigation control units 18. 2. The voltage, V_2-Wir_e to which the two-wire cable 28 is pulled down to, is measured. 3. If the voltage V_2-Wire is below the sum of Vdetection + V_margin the current limitation is increased in the "time frame", i.e. the value of the current limitation l_max is increased in step with e.g. 5mA or with a DC current value known from earlier attempts to work properly. 4. Points 2 and 3 are repeated until the voltage is OK, i.e. until the voltage to which the two-wire cable 28 is pulled down to, i.e.V2_-Wire equals or is higher than Vdetection ⁺

Vmargin-

5. Points 2-4 are repeated with reversed two-wire cable 28 polarity. When subsequent signalling from the irrigation control unit 18, the found value of the current limitation l_max .which is dependent on the polarity of the two-wire cable 28, is now used together with V_detec_tion to detect short-circuit from one of the irrigation control units 18. Voltage compensation method:

1. The controller and power supply unit 30 sets up a "time frame" at a time when it is expected that none of the irrigation control units 18 is responding, i.e. no irrigation control unit 18 signals any parameters back. Further, during the time frame no schedules of instructions are sent from the controller and power supply unit 18 to the irrigation control units 18.

2. The voltage, i.e. V₂-_Wir_e to which the two-wire cable 28 is being pulled down to, is measured.

3. If the voltage V₂-_Wire is below (V_detection + V_margin), the V_detection is lowered to V_margin under the actual voltage V₂__Wj_re, i.e. V_detection equals V_2-WiPe minus Vmargin-

4. Points 2-3 - just above - are repeated with reversed polarity of the two-wire cable 28.

When subsequent signalling from the irrigation control unit 18 the found value of Vd_ete_cti_on now found is used (dependent of the polarity of the two-wire cable 28) to detect short-circuit from one of the irrigation control units 18.

In difficult cases a combination of the current and the voltage compensation would be usable, e.g. in cases where leaks are difficult to compensate for by applying the current or the voltage compensation. E.g. if from past attempts it is known that a certain non-normal value of the current limitation l_maχ was reached and/or the method had to repeat points 2-3 of the current compensation method more times than normally required, the current and voltage compensation may be combined methods.

Either the first or the second method, i.e. the current and the voltage compensation may be applied first.

A further advantage of the two methods - and the methods applied in combination or in succession - is that the controller and power supply unit 30 may evaluate the quality of the two-wire communication. If the compensation exceeds certain limits - as expressed in V_detection +/ - V_margin and/or in the value of the current limitation l_maχ - the controller and power supply unit 30 is able to warn the operator of the system in time that the two-wire communication from the irrigation control unit 18 to the controller and power supply unit 30 may be unstable. As discussed, unstable due to unwanted leak currents somewhere in the cables of the two-wire controlling and monitoring system 10.

The two-wire system, i.e. the two cables of the two-wire cable 28 are by nature bipolar, i.e. the two-wire lines, Line-A and Line-B are symmetrical. To simplify the drawings the system is shown in the condition where Line-A is positive and Line-B is negative in relation to the ground. The line change circuit is therefore also left out in the drawings. The voltage referred to is to be seen in relation to Line-B, which is also seen and regarded as a OV level (DC ground level) in all measurements. In Fig. 19, in the principle diagram, which shows the controller and power supply unit 30 supplying e.g. + 35V DC to the two-wire lines, Line-A and Line-B. The 35 V DC is an example of the level for the line voltage for the two-cable wire signalling system.

In series with the output stage there is a current limiter - indicated with the two overlapping circles having an arrow, the arrow indicating the current flow direction, which is regulated by the signal l_max. As is known in general in the art for a current limiter circuit - regardless of its implementation - such a circuit only allows that current up to a max current limit may flow. In the case where a load, typical a relative low load (with a low resistance) the load will due to Ohms law I = U / R "try" to draw current I, however if this current is computed to be higher than l_max only l_max flows. Conversely, if the current is computed to be lower than l_maχ - in the case where the load is a high resistance - following Ohms law: I = U / R - 1 as computed then only flows.

The final voltage across the two-wire cable 28, i.e. V₂-_Wire wire is compared with V_detection and thus generas the signal "Shift" provided the final voltage on the two- wire cable 28 is lower than V_detection- V₂-_Wire is measured after the current limiter circuit by means of a voltmeter measuring the voltage across its two terminals, i.e. across Line-A and Line-B. "Shift" means that the controller and power supply unit 30 wants to re-polarise the two-wire simultaneously provided voltages (Toggle). This, however, is not shown. The two-wire lines A+B are symbolised by means of copper resistances in the wire denoted with the three R_cu and the load considered equivalent to the leak current(s) in the cable is symbolised with Rι_eak- Signalling switch for the irrigation control unit 18 is shown with the circuit around S1.

In Fig. 20, a sequence by a non-compensated system in which R|_eak is not critical is shown. In this case there is no need to apply the invention (Current or voltage compensation or their combination) since the value of R|_eak is not critical.

The control from the irrigation control unit 18 of S1 expects "Shift" at position 2 and 4 and none at position 1 and 3. It is noted that "Shift" is correct.

Fig. 21 shows the same sequence as the foregoing figure, but now R|_eak has a critical value. The resistor is equivalent to leak(s). Ri_eak now causes erroneous shifts at position 1 and 3. Communication from the irrigation control unit 18 to(wards) the controller and power supply unit 30 is not possible due to the erroneous shifts at position 1 and 3. These two shifts are caused by leak current(s) not compensated for.

Fig. 22 shows where current compensation according to the invention is applied and R|_eak is critical. During a period when no irrigation control unit 18 is known to switch S1 , i.e. the "time frame" at a time when it is expected that none of the irrigation control units 18 is responding, i.e. no irrigation control unit 18 signals back, a sequence is run through (a-d) with an increasingly reduced l_max (here three reductions as shown) in order to find the exact l_max which just then compensates for the error induced from R|_eak- This means that the V₂-_Wire voltage at this point does not go below the sum of V_detectioπ and V_margin.

Communication, i.e. the signalling in the form of transferring parameters from the irrigation control unit 18 to the controller and power supply unit 30 therefore functions correctly as indicated in the sequence 1 to 4. The current compensation method - compensating out leak currents in a two cable wire signalling system signalling between a controller and power supply unit and one or more irrigation control units - may be considered to execute the steps:

setting up the first and second alternating DC voltage signals to be simultaneously provided to the two-wire cable,

defining a current limiter circuit connected in series with the simultaneously applied DC voltage signals, the current limiter circuit having l_max as its current limitation level, the current limitation level l_maχ being adjustable,

defining a voltage detection level Vde_tection and a margin V_margin for the voltage detection level, the voltage detection level defining the level for a received parameter from one of the irrigation control units,

defining a line voltage, V_2-Wir_e which is measured as the voltage across the two-wire cable 28 at a point after the current limiter circuit,

defining a time frame in which none of the irrigation control units transmits nor the controller and power supply unit transmits parameters to one another,

measuring the line voltage, V_2-Wi_Ye , in the time frame by means of a voltmeter, increasing the current limitation level l_max of the current limiter circuit,

repeating the two foregoing steps until the measured line voltage V_2-Wire is higher than or equals the sum of the Vdetection and the margin V_margjn, and

applying the found current limitation level l_max for the line voltage when receiving signals sent from one of one or more irrigation control units to the controller and power supply unit. And in order to operate with the opposite line voltage supply from the line voltage generator which supplies the two-cable wire signalling system the current compensation method further executes the step of:

reversing the two simultaneously supplied DC voltage levels, and applying the above steps resulting in another found current limitation l_max for these DC voltage levels.

Fig. 23 shows where voltage compensation according to the invention is applied as the alternative to the current compensation, and again R|_eak has a critical value.

During a period when no irrigation control unit 18 is known to switch S1, i.e. the "time frame" at a time when it is expected that none of the irrigation control units 18 is responding, i.e. no irrigation control unit 18 signals back, a sequence is run through (a-b) during which sequence V_detecti_on in principle is reduced so that the reduced voltage for V_dete_cu_on compensates for the error induced from Rι_eak- This means that the V2-_Wire voltage does not go below the sum of Vdetection and V_margin- Accordingly, the voltage detection level, V_detecti_on is set to the line voltage, V₂-_Wire minUS Vmargin-

Communication, i.e. the signalling in the form of transferring parameters from the irrigation control unit 18 to the controller and power supply unit 30 is subsequently to be expected to function correct as indicated in the sequence 1 to 4.

The voltage compensation method - compensating out leak currents in a two cable wire signalling system signalling between a controller and power supply unit and one or more irrigation control units - may be considered to execute the steps:

defining a time frame in which none of the irrigation control units transmits nor the controller and power supply unit transmits parameters to one another, defining a voltage detection level V_detecti_on and a margin V_margj_n for the voltage detection level, the voltage detection level defining the level for a received parameter from one of the irrigation control units,

defining a line voltage, V_2-Wjr_e which is measured as the voltage across the two-wire cable 28,

measuring the line voltage, V₂._Wir_e , in the time frame by means of a voltmeter, setting the voltage detection level, V_detection to the line voltage, V₂-_Wj_re minus V_margin, when the voltage V_2-Wire is below (V_detection + V_margin), and

applying the set voltage detection level, V_detection for the level line voltage when receiving signals sent from one of one or more irrigation control units to the controller and power supply unit.

And in order to operate with the opposite line voltage supply from the line voltage generator which supplies the two-wire cable signalling system, the voltage compensation method further executes the step of:

reversing the two simultaneously supplied DC voltage levels, and applying the above steps resulting in another found voltage detection level V_detecti_on for these DC levels.

The numerical value of the first and second DC level line voltage is e.g. 35 V. The V_detection and/or the margin V_margin level is/are user selectable, e.g. by means of a menu driven selection on the controller and power supply unit. This also applies to l_max.

Each of the methods - voltage and current compensation and the combination of the two - is implemented as an addition to the normal basic functioning of the system for irrigation, i.e. normally the system is used to irrigate whereby normal signalling goes forth and back between the irrigation control units and the controller and power supply unit. Normally, the methods are always active, but of course no compensation takes place when not detected to be required. However, in case that leak currents deteriorate and/or make it difficult for the controller and power supply unit to receive signalling from any of the irrigation control units, one of these three methods are applied to compensate out the leak currents.

The invention could be physically implemented as follows:

Method No. 1, i.e. the current compensation requires that there is a variable current limiter in the two-wire output stage besides a voltmeter measuring V_2-Wire across its two terminals. See the enclosed circuit diagram SDC-1 in Fig. 24. The applicant has implemented the current compensation by means of the circuit shown in the diagram.

Method No. 2 i.e. the Voltage compensation requires nothing beyond what is normally implemented for the communication between the control unit 18 and the controller and power supply unit 30 communication. This means that the electronic circuitry already present, i.e. the electronic circuitry as used prior to this invention may be applied. (Switching between High/Low current limitation and a voltmeter). See the enclosed circuit diagram RBC200 in Fig. 25. The applicant has implemented the voltage compensation by means of the circuit shown in the diagram.

Example

The sensor decoder 52 shown in Fig. 11 and as described above was implemented in a prototype version from the following components. Fuse

P1 230V

Resistors:

R1 46R4 R14 39R2 R27 470K

R2 46R4 R15 10K R28 470K

R3 100K R16 39K R29 56K

R4 86K6 R17 39K R30 39K

R5 100K R18 10K R31 27K1

R6 100K R19 39K R32 39K

R7 100K R20 39K R33 56K

R8 10K R21 86K6 R34 100K

R9 150K R22 4R7 R35 2K49

R10 768K R23 10K R36 825R

R11 22K1 R24 10K R37 2R2

R12 100K R25 10K R38 39K

R13 39K R26 10K

Capacitors

C1 1000μ C6 33p C11 1n

C2 10n C7 1n C12 1n

C3 100n C8 1n C13 1n

C4 10μ C9 100n

C5 33p C10 100n

Diodes

D1 DF04S D6 BYD 17D D11 22V

D2 10V D7 6V8 D12 22V

D3 BYD 17D D8 LL4148 D13 15V

D4 BYD17D D9 LL4148

D5 BYD 17D D10 3V2 Transistors

Q1 TIP122 Q4 BC856 Q6 MJD6039

Q2 BC856 Q5 BC846 Q7 MJD6039

Q3 BC846

Integrated Circuits and Crystal

IC1 ST6220 IC3 LM317LM IC5 LMC662C

IC2 93C05 IC4 LM358N X1 6.144MHz

The line decoder 44 shown in Fig. 12 and as described above was implemented in a prototype version from the following components.

Fuse

P1 20OmA

Resistors:

R1 470K R6 68K R11 1M

R2 100K R7 56K R12 470K

R3 100K R8 470K R13 1K

R4 680K R9 1K R18 1K

R5 100K R10 33K R19 3K3

Capacitors

C1 3n3 C4 10μ C6 1000μ

C2 3n3 C5 10μ C7 3n3

C3 3n3 Diodes

D1 DF04S D3 LL4148 D5 BYD 17D

D2 BZX84-10V D4 MLL4690 D6 BYD17D

Transistors

Q1 BC856B Q3 2SB1214 Q4 2SB1817

Q2 BC856B

Integrated Circuits

IC1 μPD7556 IC2 93C06

Resistors:

R1 470K R8 470K R14 3K3

R2 100K R9 1K R15 3K3

R3 100K R10 33K R16 3K3

R4 680K R11 1M R17 3K3

R5 100K R12 68K R18 1K

R6 68K R13 1K R19 3K3

R7 56K

Capacitors

C1 3n3 C3 2200μ C5 1μ

C2 3n3 C4 10μ

Diodes

D1 DF04S D7 BYD17D D13 BYD 17D

D2 BZX84-10V D8 BYD 17D D14 BYD 17D

D3 LL4148 D9 BYD 17D D15 BYD 17D D4 MLL4690 D10 BYD 17D D16 BYD17D

D5 BYD 17D D11 BYD 17D D17 BYD 17D

D6 BYD 17D D12 BYD 17D

Transistors

Q1 BC856B Q4 2SB1214 Q7 MJD6039

Q2 BC855B Q5 2SB1214 Q8 2SB1214

Q3 2SB1214 Q6 2SB1214 Q9 2SB1214

Integrated Circuits

IC1 uPD7556 IC2 93C06

The microprocessor and storage section shown in Fig. 14a and 14b and as described above was implemented in a prototype version from the following components.

Resistors:

R105 4K7 R14 1M R102 PTC4.3

R104 1K R4 680K R101 OR

Capacitors and Inductors

C101 100μ C108 22n C6 33p

C103 100n C109 22n C7 33p

C104 100n C110 22n L101 10μ

C105 100n cm 22n L102 10μ

C106 100n C112 10μ L103 10μ

C107 100n C113 22n Diodes

D1 ICTE5 D104 BZW06P6V8B D105 BZW06P6V8B

Integrated Circuits and Crystal

IC101 27256 IC108 74HC573 IC4 PC812

IC102 62256 IC110 75175 IC5 PC813

IC103 6264 IC111 74HC02 IC6 PC910

IC 104 6264 IC112 74HC08 X1 11.0592

IC106 74HC138 IC115 4548

IC107 8031 IC116 74HC366

The power output stage shown in Fig. 15a and 15b and as described above was implemented in a prototype version from the following components.

Resistors:

R1 390R R17 487K R34 1K

R2 1K R18 10K R35 2OK

R3 Not Used R19 110K R36 1M

R4 390R R20 53K6 R37 68R

R5 Not Used R21 365K R38 270R

R6 100R R22 4R7 R39 47R

R7 100R R23 470R R40 100K

R8 10K R24 470R R51 390K

R9 18K R25 27R R52 10K

R10 390K R26 27R R53 1 K

R11A 2R R27 1K P1 S10K25

R11B 2R R28 47R P2 S10K25

R11C 2R R29 10K P3 S10K25

R11D 2R R30 100K P5 S10K25

R12 1K R31 100K P6 S10K25

R13 1M R32 100K P7 S10K25

R15 10K R33 100R

R16 14K

Capacitors and Inductors

C1 Not Used C12 10μ C51 100n

C2 Not Used C13 10μ C52 1μ

C3 Not Used C14 10μ L1 25μ

C4 Not Used C15 22n L2 25μ

C5 1n C16 22n RE1 Relay

C8 1000μ C20 Not Used

C9 100μ C21 Not Used

C10 100μ C50 100n

Diodes

D1 BYW98 D6 1N4148 D10 1N4002

D2 BYW98 D8 1N4002 D11 1N4002

D4 Z6V8 D9 1N4002 D103 1N4148

D5 Z15V/1W

Transistors

T1 BC637 T4 BC637 T8 TIP100

T2 BDW74D T5 BDW74D

T3 IRFD02 T6 IRFD02 Integrated Circuits

IC1 LM7812 IC9 4001 IC13 ADC0834

IC2 CA3240A IC10 4053 IC14 44111

IC3 LM340LA IC11 4094 IC15 TCA365A

IC7 LM3395 IC12 4094

The mark sender shown in Fig. 16a and 16b and as described above was implemented in a prototype version from the following components.

Resistors:

R1 12R R9 100K R17 10K

R2 10K R10 100K R18 56K

R3 5K6 R11 270K R19 27K

R4 22R R12 270K R20 10K

R5 2K2 R13 10K R21 1K

R6 10K R14 3K3 R22 100K

R7 680R R15 10K R23 10K

R8 330R R16 2K2

Capacitors and Inductors

C1 10μ C6 47n C11 10μ

C2 220μ C7 47n C12 100n

C3 100n C8 47n C13 220μ

C4 22Op C9 47n L1 100μ

C5 100μ C10 100n Diodes

D1 DFO4M D3 10V D5 3V9

D2 P6KE47A D4 BYW100 D6 1N4148

Transistors

T1 IRF9120 T3 IRF110 T4 1RF110

T2 BC337

Integrated Circuits and Crystal

IC1 80C31 IC5 74HC541 IC8 LM324

IC2 26G256 IC6A 74HC95 IC9 7555

IC3 74HC573 IC6B 74HC352 IC10 LM317

IC4 X2444 IC7 74HC86 X1 6.144MHz

The circuit diagram in Fig. 24 implementing the current compensation was implemented in a prototype version by the applicant and is considered to be self- explanatory and consists of the following part:

Used Part Type Designator

Resistors

2 0.9A P102 P103

9 IOOR R108 R109 R118 R131

R132 R133 R134 R135

R136

3 1OK RlOl R102 R116

2 10KO R125 R127

2 13K0 R126 R128

1 IKO R129

1 22R R112

1 300R R120

1 3K32 R121

3 3R90 R105 R106 R107

2 40K2 R123 R124

4 4K7 RIlO RlIl R117 R122

1 681R R119

2 6K8 R103 R104

4 8R25 R113 R114 R115 R130 capacitors 3 IOONF ClOl C102 C103 2 1NF/500V C104 C105

Coils

2 1000UH/0.6A LlOl L102

Spark gabs

1 90V PlOl

Diodes

4 22V D113 D114 D115 D116

2 3V3 DlOl D102

2 BT136D D117 D118

4 BYD17 D109 DIlO Dill D112

4 LL4148 D103 D106 D107 D108

Transistors

1 BC846 Q106

1 BC856 Q107

2 MJD6039 Q104 Q105

1 Si9400DY Q103

2 TIP127 QlOl Q102

Integrated Circuits 1 LM339 IC103 1 LM358 IC104 1 LM393A IC102 1 74HC02 IClOl

The circuit diagram in Fig. 25 implementing the voltage compensation was implemented in a prototype version by the applicant and is considered to be self- explanatory and consists of the following part:.

Used Part Type Designator

Resistors

1 0R51 R29

4 IOOR R19 R20 R33 R44

4 1OK R37 R39 R8 R9

2 10KO R21 R22

2 13K0 R23 R24

1 150K R2

4 IKO R13 Rl4 R27 R7

1 IKOO R41

1 IMO R45

1 IRO R38 2 220K R34 R6

1 22K R5

1 22K NTC R43

3 27K R3 R35 R36

2 2K2 Rl R4

4 390R RIl R12 R15 R16

2 3K32 R40 R42

2 40K2 R25 R26

3 4K7 RlO R17 R18

1 56K R28

1 5K11 R32

2 681R R30 R31

Capacitors

3 10NF Cl ClO C2

3 IUF C7 C8 C9

1 INF C5

3 IOONF C3 C4 C6

Coils

1 ImH Ll

Diodes

2 BZX84C2V4 D2 D3 1 LL4148 D4

Transistors

3 BC846 Q5 Q6 Ql 2 TIP122 Q3 Q4 2 TIP127 Ql Q2

Integrated Circuits

1 4053 IC3

2 LM358 IC2 IC6 3 LM393A IC5 IC7 IC8

1 74HC02 IC4

1 74HC14 ICl

Claims

1. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area controlled by said controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and a specific line decoder being the intentional receiver of a specific schedule of instructions responding by transmitting an acknowledgement signal to said controller and power supply unit through said two-wire cable within a first time frame of said first pulse provided said specific schedule of instructions is correctly received or, alternatively, transmitting a not-acknowledgement signal to said controller and power supply unit through said two-wire cable within a second time frame of said first pulse provided said specific schedule of instructions is not correctly received.

2. The two-wire controlling and monitoring system according to claim 1 , said controller and power supply unit supplying a minimum current to said two-wire cable during said first and second time frames of said first pulse.

3. The two-wire controlling and monitoring system according to claim 2, said first frame being prior to said second frame.

4. The two-wire controlling and monitoring system according to claim 2, said second frame being prior to said first frame.

5. The two-wire controlling and monitoring system according to claim 1, further comprising a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and said third plurality of localised irrigation control units further comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, and said sensor decoders further each having a pair of control and power supply inputs.

6. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil and comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area of said localised areas controlled by said controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, said sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and a specific sensor decoder being the intentional receiver of a specific schedule of instructions responding by transmitting an acknowledgement signal to said controller and power supply unit through said two-wire cable within a first time frame of said first pulse provided said specific schedule of instructions is correctly received or, alternatively, transmitting a not-acknowledgement signal to said controller and power supply unit through said two-wire cable within a second time frame of said first pulse provided said specific schedule of instructions is not correctly received.

7. The two-wire controlling and monitoring system according to claim 6, said controller and power supply unit supplying a minimum current to said two-wire cable during said first and second time frames of said first pulse.

8. The two-wire controlling and monitoring system according to claim 7, said first frame being prior to said second frame.

9. The two-wire controlling and monitoring system according to claim 7, said second frame being prior to said first frame.

10. The two-wire controlling and monitoring system according to claim 6, said third plurality of localised irrigation control units each further comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs,

11. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said water pipeline is wholly or partly buried under ground, or said water pipeline is placed on the ground and/or wherein said water pipeline are constructed from plastic materials or metal materials such as iron, steel, copper, silver, gold or any alloys thereof in any combinations thereof.

12. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said first plurality of controllable irrigation valves are magnetically, electrically, hydraulically or pneumatically operated or combinations thereof and/or wherein said first plurality of controllable irrigation valves are opened by applying an inrush voltage or current signal followed by a hold voltage or current signal to said pair of valve control inputs and closed by applying no voltage or current signal to said pair of valve control inputs and/or wherein said second plurality of field sensors comprises a selection of temperature sensors, humidity sensors, pressure sensors, flow sensors, magnetic field sensors, mechanical movement sensors, mechanical strain sensors, fertiliser sensors or any combination thereof.

13. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said first pulse width is equal to said second pulse width or wherein said first pulse width is smaller than said second pulse width or wherein said first pulse width is greater than said second pulse width.

14. The two-wire controlling and monitoring system according to claims 1 or 6, said schedule of instructions being transmitted onto said two-wire system by re-scaling said first pulse width or said second pulse width to a fifth pulse width smaller than said first pulse width or said second pulse width and indicating a binary "1", or by re-scaling said first pulse width or said second pulse width to a sixth pulse smaller than said first pulse width or said second pulse width and indicating a binary "0".

15. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said first alternating DC voltage signal and said second alternating DC voltage signal alternate with a frequency less than AC frequency of power networks such as 50Hz or 60Hz.

16. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said first pulse width of said first alternating DC voltage signal and said second alternating DC voltage signal is in the range 100ms to 10s such as ranges 200ms to 2s, 300ms to 1s, 400ms to 800ms, 450 ms to 550 ms, 475 ms to 525 ms or 490 ms to 510 ms, or preferably said first pulse width is 500 ms and/or wherein said second pulse width of said first alternating DC voltage signal and said second alternating DC voltage signal is in the range 100ms to 10s such as ranges 200ms to 2s, 300ms to 1s, 400ms to 800ms, 450 ms to 550 ms, 475 ms to 525 ms or 490 ms to 510 ms, or preferably said second pulse width is 500 ms.

17. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said voltage maximum is in a range from +10V to +20V, such as ranges +13V to +19V or +14V to +17V, or preferable said voltage maximum is +15V and/or wherein said voltage minimum in a range from -15V to - 25V, such as ranges -17V to -23V and -19V to -21V, or preferable said voltage minimum is -20V.

18. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said first alternating DC voltage signal and said second alternating DC voltage signal during said first pulse width and said second pulse width averages voltages greater than or equal to zero voltage or wherein said first alternating DC voltage signal and said second alternating DC voltage signal during said first pulse width and said second pulse width averages voltages less than or equal to zero voltage and/or wherein said first alternating DC voltage signal and said second alternating DC voltage signal averages during said first pulse width and said second pulse width an average voltage in the range -5V to -0.5V such as ranges -4V to -1 V or -2.5V to -1.5V, or preferably said average voltages are -2V.

19. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said maximum current is in the range of 0.5A to 2A such as 0.75A to 1.5A, or preferably said maximum current is 1.1A and/or wherein said minimum current is in the range 2OmA to 15OmA such as ranges 3OmA to 100mA or 35mA to 85mA, or preferably said minimum current is 40mA.

20. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said third pulse width is greater than said fourth pulse width and/or wherein said fourth pulse width is in the range 0.1ms to 10ms such as range 0.5ms to 7ms or preferably said fourth pulse width is shorter than 5ms.

21. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said line decoders provides said inrush voltage, said hold voltage and said zero voltage to said first plurality of controllable irrigation valves by supplying from said pair of valve control outputs a pulsed alternating DC control signal to said pair of valve control inputs in accordance with said transmitted schedules of instructions and/or wherein said pulsed alternating DC signal defining a maximum voltage in the range of 25V to 45V such as ranges 27V to 43V or 30V to 40V or preferably said maximum voltage being 35V, defining a minimum voltage in the range of OV to 5V such as ranges OV to 3V or OV to 1 V or preferably said minimum voltage being OV, defining a line decoder output pulse width in the range of 100μs to 0.1s such as ranges 200μs to 2ms or 800μs to 1.25ms or preferably said first decode output pulse width being 1ms, said line decoder output pulse width defining a first part having said maximum voltage and a second part having said minimum voltage, and wherein said pulsed alternating DC signal constituting said inrush voltage by having said first part longer than or equal to said second part during a period in the range 10ms to 1s such as 30ms to 100ms and constituting said hold voltage by having said first part shorter than said second part during a period determined in accordance with said schedule of instructions transmitted to said line decoders by said controller and power supply unit.

22. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said schedules of instructions are transmitted onto said two-wire system by re-scaling said first pulse width or said second pulse width to fifth pulse width in the range 10ms to 49ms such as ranges 15ms to 35ms or 17ms to 25ms, or preferably said fifth pulse width is 20ms indicating a binary "1", or by re- scaling said first pulse width or said second pulse width to a sixth pulse width in the range 0.1ms to 9ms such as ranges 2ms to 8ms or 3ms to 6ms, or preferably said sixth pulse width is 5ms indicating binary "0" and/or wherein said schedules of instructions comprise a type declaration determining additional content of a transmission from said controller and power supply unit to said third plurality of localised irrigation control units, said additional content such as an address of a specific designated localised irrigation control unit of said third plurality of localised irrigation control units, data disclosing information regarding actions to be taken by said specific designated localised irrigation control unit of said third plurality of localised irrigation control units and/or a first check and a second check ensuring a safe reception of said transmission is terminated by stop signal having a seventh pulse width and/or wherein said seventh pulse width is in the range 50ms to 70ms such as 55ms to 65ms, or preferably said seventh pulse width is 60ms.

23. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said type declaration comprising 4 bits provides 16 optional operations such as Arbitration, Data, Control (On/Off), Broadcast, Test and Pole and/or wherein said address of said specific designated localised irrigation control unit of said third plurality of localised irrigation control units comprises an address transmission size in the range 0 to 128 bits such as ranges 0 to 64 bits or 0 to 32, or said address transmission size preferably 16 bits and/or wherein said data disclosing information regarding actions to be taken by said specific designated localised irrigation control unit of said third plurality of localised irrigation control units comprises a data transmission size in the range of 0 to 64KBYTE and/or wherein said first check and said second check ensuring a safe reception of said transmission comprise a check transmission size in the range 0 to 128 such as ranges 0 to 64 bits or 0 to 32 bits or preferably said check transmission size is 4 bit for each of said first and second check.

24. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said controller and power supply unit comprising a microprocessor, a storage unit for storing said schedules of instructions, an output section for providing power to said two-wire cable and transmitting said schedules of instruction on said two-wire cable, and an input section for monitoring voltage of said two-wire cable, said microprocessor controls said output section to apply said minimum current to said two-wire cable during an interrupt window and/or wherein each of said sensor decoders and/or line decoders comprise a short circuiting circuit providing an interrupt signal during said interrupt window to said controller and power supply unit by unidirectional short circuiting said pair of control and power supply inputs hence reducing differential voltage of said two-wire cable and no interrupt signal by open circuiting said pair of control and power supply inputs, said interrupt signal being constituted by a voltage drop of said differential voltage of said two-wire cable in the range 5V to 35V such as range 15V to 30V, or preferably said voltage drop is 25V and/or wherein said interrupt window is initiated following a DC alternation of said first alternating DC voltage signal and said second alternating DC voltage signal and a power supply period, said power supply period is in the range 250ms to 550ms such as ranges 300ms to 500ms or 350ms to 450ms, or preferably said power supply time period is 400ms and said interrupt window is in the range 0ms to 20 ms or preferably said interrupt window is shorter than 5ms.

25. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said microprocessor records said interrupt signal from at least one sensor decoder and/or line decoder of said third plurality of localised irrigation control units through said input section monitoring voltage of said two-wire cable and subsequently operates said output section to perform a DC alternation of said first alternating DC voltage signal and said second alternating DC voltage signal and operates said output section to terminate said interrupt window and apply said maximum current to said two-wire cable and/or wherein said microprocessor following a recording of said interrupt signal from at least one interrupting sensor decoder and/or line decoder of said third plurality of localised irrigation control units performs a DC alternation of said first alternating DC voltage signal and said second alternating DC voltage signal and transmits said type declaration Arbitration followed by a series of binary "1"s including an answer window for said at least one interrupting sensor decoder and/or line decoder of said third plurality of localised irrigation control units to answer to said binary "1" and/or wherein said answer window is initiated following a DC alternation of said first alternating DC voltage signal and said second alternating DC voltage signal and a pause period, said pause period is in the range 2ms to 10ms such as ranges 3ms to 8ms or 4ms to 6ms, or preferably said pause period is 5ms and said answer window is in the range 0ms to 20ms or preferably said answer window is shorter than 2.5ms.

26. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said short circuiting circuit providing an answer signal during said answer window to said controller and power supply unit by unidirectional short circuiting said pair of control and power supply inputs hence reducing differential voltage of said two-wire cable and no answer signal by open circuiting said pair of control and power supply inputs, said answer signal is constituted by a voltage drop of said differential voltage of said two-wire cable in the range 5V to 35V such as range 15V to 30V, or preferably said voltage drop is 25V and/or wherein said microprocessor controls said output section to supply said minimum current to said two-wire cable during said answer window.

27. The two-wire irrigation controlling and monitoring system according to any of the claims 1 or 6, wherein said controller and power supply unit during a declared type of transmission of schedules and instructions requests said specific irrigation parameters from an addressed sensor decoder of said third plurality of localised irrigation control units and subsequently said controller and power supply unit transmits a series of binary "1" including said answer window for said addressed decoder to answer to said binary "1 " and/or wherein said microprocessor records said answer signal from at least one sensor decoder of said third plurality of localised irrigation control units through said input section monitoring said voltage of said two-wire cable and operates said output section to perform a DC alternation of said first alternating DC voltage signal and said second alternating DC voltage signal and subsequently operates said output section to terminate said answer window and to apply said maximum current to said two-wire cable and/or wherein said microprocessor interprets said answer signal as an indication of a binary "0" and no answer signal as a binary "1".

28. A method for controlling and monitoring in particular irrigation of localised areas of soil and comprising the following steps of: providing water to said localised areas of soil through a water pipeline, controlling the discharge or supply of water from said water pipeline, providing watering of said specific area of a localised areas of soil through a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil and said first plurality of controllable irrigation valves having a pair of valve control inputs, measuring specific irrigation parameters through a second plurality of field sensors positioned at specific areas of said localised areas of soil and said second plurality of field sensors having a pair of sensor outputs, transmitting control signals to said first plurality of controllable irrigation valves and said second plurality of field sensors though a third plurality of localised irrigation control units comprising a sensor decoder and a line decoder, providing valve control signals to said first plurality of controllable irrigation valves and/or recording said specific irrigation parameters from said second plurality of field sensors, each of said third plurality of localised irrigation control units having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves and/or a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors and having a pair of control and power supply inputs, providing a set of schedules of instructions by means of a controller and power supply unit having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, providing a two-wire cable, interconnecting said controller and power supply unit and said third plurality of localised irrigation control units through a two-wire cable connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said control and power unit to each of said third plurality of localised irrigation control units, transmitting said schedules of instructions from said controller and power supply unit to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and transmitting from an irrigation control unit being the intentional receiver of a specific schedule of instructions an acknowledgement signal to said controller and power supply unit through said two-wire cable within a first time frame of said first pulse, provided said specific schedule of instructions is correctly received or alternatively a not-acknowledgement signal to said controller and power supply unit through said two-wire cable within a second time frame of said first pulse provided said specific schedule of instructions is not correctly received.

29. The method for controlling and monitoring in particular irrigation of localised areas of soil according to claim 28, said controller and power supply unit supplying a minimum current to said two-wire cable during said first and second time frames of said first pulse.

30. The method for controlling and monitoring in particular irrigation of localised areas of soil according to claim 29, said first frame being prior to said second frame.

31. The method for controlling and monitoring in particular irrigation of localised areas of soil according to claim 29, said second frame being prior to said first frame.

32. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area controlled by said controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and a first time frame being defined in said first alternating DC voltage signal, within said first time frame of a first occurring first alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to a first short circuiting current detection level and measuring any reduction of said first alternating DC voltage signal, and within said first time frame of a succeeding first alternating DC voltage signal said controller and power supply unit increasing said first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of said first alternating DC voltage signal.

33. The two-wire controlling and monitoring system according to claim 32 further comprising a second time frame being defined in said second alternating DC voltage signal, within said second time frame of a first occurring second alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to said increased first short circuiting current detection level and measuring any reduction of said second alternating DC voltage signal, and within said second time frame of a succeeding second alternating DC voltage signal said controller and power supply unit increasing said increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of said second alternating DC voltage signal.

34. The two-wire controlling and monitoring system according to claim 32, during said first time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

35. The two-wire controlling and monitoring system according to claim 33, during said second time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

36. The two-wire controlling and monitoring system according to claim 32, said controller and power supply unit subsequently applying during said first and second alternating DC voltage signals said increased first short circuiting current detection level and said second short circuiting current detection level.

37. The two-wire controlling and monitoring system according to claim 32, further comprising a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and said third plurality of localised irrigation control units further comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, and said sensor decoders further each having a pair of control and power supply inputs.

38. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area of said localised areas controlled by said controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, said sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and a first time frame being defined in said first alternating DC voltage signal, within said first time frame of a first occurring first alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to a first short circuiting current detection level and measuring any reduction of said first alternating DC voltage signal, and within said first time frame of a succeeding first alternating DC voltage signal said controller and power supply unit increasing said first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of said first alternating DC voltage signal.

39. The two-wire controlling and monitoring system according to claim 38 further comprising a second time frame being defined in said second alternating DC voltage signal, within said second time frame of a first occurring second alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to said increased first short circuiting current detection level and measuring any reduction of said second alternating DC voltage signal, and within said second time frame of a succeeding second alternating DC voltage signal said controller and power supply unit increasing said increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of said second alternating DC voltage signal.

40. The two-wire controlling and monitoring system according to claim 38, during said first time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

41. The two-wire controlling and monitoring system according to claim 39, during said second time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

42. The two-wire controlling and monitoring system according to claim 38, said controller and power supply unit subsequently applying during said first and second alternating DC voltage signals said increased first short circuiting current detection level and said second short circuiting current detection level.

43. The two-wire controlling and monitoring system according to claim 38, said third plurality of localised irrigation control units each further comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs.

44. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area controlled by said controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and a third time frame being defined in said first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within said third time frame said controller and power supply unit measuring a measuring level of said first alternating DC voltage signal for detecting any reduction of said first alternating DC voltage signal, and provided said measuring level of said first alternating DC voltage signal being below said first short circuit voltage signalling detection level, said first short circuit voltage signalling detection level being set below said measuring level of said first alternating DC voltage signal.

45. The two-wire controlling and monitoring system according to claim 44 further comprising a fourth time frame being defined in said second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within said fourth time frame said controller and power supply unit measuring a measuring level of said second alternating DC voltage signal for detecting any reduction of said second alternating DC voltage signal, and provided said measuring level of said second alternating DC voltage signal being below said second short circuit voltage signalling detection level, said second short circuit voltage signalling detection level being set below said measuring level of said second alternating DC voltage signal.

46. The two-wire controlling and monitoring system according to claim 44, during said third time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

47. The two-wire controlling and monitoring system according to claim 45, during said fourth time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

48. The two-wire controlling and monitoring system according to claim 44, said controller and power supply unit subsequently applying during said first and second alternating DC voltage signals said first and second short circuiting voltage signalling detection levels.

49. The two-wire controlling and monitoring system according to claim 44, further comprising a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and said third plurality of localised irrigation control units further comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, and said sensor decoders further each having a pair of control and power supply inputs.

50. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area of said localised areas controlled by said controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, said sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, and a third time frame being defined in said first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within said third time frame said controller and power supply unit measuring a measuring level of said first alternating DC voltage signal for detecting any reduction of said first alternating DC voltage signal, and provided said measuring level of said first alternating DC voltage signal being below said first short circuit voltage signalling detection level, said first short circuit voltage signalling detectionlevel being set below said measuring level of said first alternating DC voltage signal.

51. The two-wire controlling and monitoring system according to claim 50 further comprising a fourth time frame being defined in said second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within said fourth time frame said controller and power supply unit measuring a measuring level of said second alternating DC voltage signal for detecting any reduction of said second alternating DC voltage signal, and provided said measuring level of said second alternating DC voltage signal being below said second short circuit voltage signalling detection level, said second short circuit voltage signalling detection level being set below said measuring level of said second alternating DC voltage signal.

52. The two-wire controlling and monitoring system according to claim 50, during said third time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

53. The two-wire controlling and monitoring system according to claim 51, during said fourth time frame said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

54. The two-wire controlling and monitoring system according to claim 50, said controller and power supply unit subsequently applying during said first and second alternating DC voltage signals said first and second short circuiting voltage signalling detection levels.

55. The two-wire controlling and monitoring system according to claim 50, said third plurality of localised irrigation control units each further comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs,

56. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area controlled by said controlling and monitoring system and having a pair of valve control inputs, a third plurality of localised irrigation control units each comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, a first time frame being defined in said first alternating DC voltage signal, within said first time frame of a first occurring first alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to a first short circuiting current detection level and measuring any reduction of said first alternating DC voltage signal, and within said first time frame of a succeeding first alternating DC voltage signal said controller and power supply unit increasing said first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of said first alternating DC voltage signal, a second time frame being defined in said second alternating DC voltage signal, within said second time frame of a first occurring second alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to said increased first short circuiting current detection level and measuring any reduction of said second alternating DC voltage signal, and within said second time frame of a succeeding second alternating DC voltage signal said controller and power supply unit increasing said increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of said second alternating DC voltage signal, a third time frame being defined in said first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within said third time frame said controller and power supply unit measuring a measuring level of said first alternating DC voltage signal for detecting any reduction of said first alternating DC voltage signal, and provided said measuring level of said first alternating DC voltage signal being below said first short circuit voltage signalling detection level, said first short circuit voltage signalling detection level being set below said measuring level of said first alternating DC voltage signal, and a fourth time frame being defined in said second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within said fourth time frame said controller and power supply unit measuring a measuring level of said second alternating DC voltage signal for detecting any reduction of said second alternating DC voltage signal, and provided said measuring level of said second alternating DC voltage signal being below said second short circuit voltage signalling detection level, said second short circuit voltage signalling detection level being set below said measuring level of said second alternating DC voltage signal.

57. The two-wire controlling and monitoring system according to claim 56, during said first and second time frames said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

58. The two-wire controlling and monitoring system according to claim 56, during said third and fourth time frames said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

59. The two-wire controlling and monitoring system according to claim 56, said controller and power supply unit subsequently applying during said first and second alternating DC voltage signals said increased first short circuiting current detection level, said second short circuiting current detection level, and said first and second short circuit voltage signalling detection levels.

60. The two-wire controlling and monitoring system according to claim 56, further comprising a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, and said third plurality of localised irrigation control units further comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, and said sensor decoders further each having a pair of control and power supply inputs.

61. A two-wire controlling and monitoring system for in particular irrigation of localised areas of soil comprising: a water pipeline providing water to said localised areas of soil, a first plurality of controllable irrigation valves each positioned at a specific area of said localised areas of soil, communicating with said water pipeline, providing watering of said specific area of said localised areas controlled by said controlling and monitoring system of soil and having a pair of valve control inputs, a second plurality of field sensors positioned at specific areas of said localised areas of soil, providing specific irrigation parameters and having a pair of sensor outputs, a third plurality of localised irrigation control units each comprising a sensor decoder having a pair of sensor inputs connected to said pair of sensor outputs of a specific field sensor of said second plurality of field sensors for providing power to said second plurality of field sensors and recording said specific irrigation parameters from said second plurality of field sensors, said sensor decoders further each having a pair of control and power supply inputs, a controller and power supply unit having a set of schedules of instructions and having a pair of control and power outputs supplying power by applying a first alternating DC voltage signal defining a voltage maximum having a first pulse width and defining a voltage minimum having a second pulse width to one of said pair of control and power outputs, simultaneously applying a second alternating DC voltage signal similarly shaped but of inverted polarity as compared to said first alternating DC voltage signal to another of said pair of control and power outputs and applying an alternating DC current defining a current maximum having a third pulse width and defining a current minimum having a fourth pulse width to said pair of control and power outputs, a two-wire cable interconnecting said controller and power supply unit and said third plurality of localised irrigation control units and connecting said pair of control and power outputs of said controller and power supply unit to said control and power inputs of said third plurality of localised irrigation control units and providing said power from said controller and power supply unit to each of said third plurality of localised irrigation control units, said controller and power supply unit transmitting said schedules of instructions to said third plurality of localised irrigation control units through said two-wire cable and receiving said specific irrigation parameters from said third plurality of localised irrigation control units through said two-wire cable, a first time frame being defined in said first alternating DC voltage signal, within said first time frame of a first occurring first alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to a first short circuiting current detection level and measuring any reduction of said first alternating DC voltage signal, and within said first time frame of a succeeding first alternating DC voltage signal said controller and power supply unit increasing said first short circuiting current detection level to an increased first short circuiting current detection level so as to compensate any reduction of said first alternating DC voltage signal, a second time frame being defined in said second alternating DC voltage signal, within said second time frame of a first occurring second alternating DC voltage signal, said controller and power supply unit reducing said alternating DC current to said increased first short circuiting current detection level and measuring any reduction of said second alternating DC voltage signal, and within said second time frame of a succeeding second alternating DC voltage signal said controller and power supply unit increasing said increased first short circuiting current detection level to a second short circuiting current detection level so as to compensate any reduction of said second alternating DC voltage signal, a third time frame being defined in said first alternating DC voltage signal, and a first short circuit voltage signalling detection level being defined, within said third time frame said controller and power supply unit measuring a measuring level of said first alternating DC voltage signal for detecting any reduction of said first alternating DC voltage signal, and provided said measuring level of said first alternating DC voltage signal being below said first short circuit voltage signalling detection level, said first short circuit voltage signalling detection level being set below said measuring level of said first alternating DC voltage signal, and a fourth time frame being defined in said second alternating DC voltage signal, and a second short circuit voltage signalling detection level being defined, within said fourth time frame said controller and power supply unit measuring a measuring level of said second alternating DC voltage signal for detecting any reduction of said second alternating DC voltage signal, and provided said measuring level of said second alternating DC voltage signal being below said second short circuit voltage signalling detection level, said second short circuit voltage signalling detection level being set below said measuring level of said second alternating DC voltage signal.

62. The two-wire controlling and monitoring system according to claim 61, during said first and second time frames said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

63. The two-wire controlling and monitoring system according to claim 61, during said third and fourth time frames said controller and power supply unit not transmitting said schedules of instructions to said third plurality of localised irrigation control units.

64. The two-wire controlling and monitoring system according to claim 61, said controller and power supply unit subsequently applying during said first and second alternating DC voltage signals said increased first short circuiting current detection level, said second short circuiting current detection level, and said first and second short circuit voltage signalling detection levels.

65. The two-wire controlling and monitoring system according to claim 61 , said third plurality of localised irrigation control units each further comprising a line decoder having a pair of valve control outputs connected to said pair of valve control inputs of a specific controllable irrigation valve of said first plurality of controllable irrigation valves for providing valve control signals to said first plurality of controllable irrigation valves, said line decoders further each having a pair of control and power supply inputs.

66. The two-wire irrigation controlling and monitoring system according to claim 61, wherein said voltage maximum is in a range from +10V to +20V, such as ranges +13V to +19V or +14V to +17V, or preferable said voltage maximum is +15V and/or wherein said voltage minimum in a range from -15V to -25V, such as ranges -17V to -23V and -19V to -21V, or preferable said voltage minimum is -20V.

67. The two-wire irrigation controlling and monitoring system according to claim 61, wherein said first alternating DC voltage signal and said second alternating DC voltage signal during said first pulse width and said second pulse width averages voltages greater than or equal to zero voltage or wherein said first alternating DC voltage signal and said second alternating DC voltage signal during said first pulse width and said second pulse width averages voltages less than or equal to zero voltage and/or wherein said first alternating DC voltage signal and said second alternating DC voltage signal averages during said first pulse width and said second pulse width an average voltage in the range -5V to -0.5V such as ranges -~4V to - 1 V or -2.5V to -1.5V, or preferably said average voltages are -2V.