GB2081483A - Vehicle alarm and immobilising device - Google Patents

Abstract

A vehicle alarm and immobilising device in which an arrangement of push-buttons located inside the vehicle is used to introduce a coded signal into the device to switch the device into its non-operating state. When the device is switched to its ready state, the vehicle is immobilised and, if a door is opened, the device changes to its activated state and an alarm will sound unless the coded signal is introduced into the device within a time interval. If the signal is introduced, the device changes to its non-operating state and, if the signal is not introduced, the alarm sounds and the vehicle remains immobilised. <IMAGE>

Description

SPECIFICATION Vehicle alarm and immobilising device This invention relates to a combined alarm and immobilising device for a motor vehicle.

Vehicle alarm devices which are in use at the present time are set when all the doors of the vehicle are closed and, if any of these doors is opened, then the alarm is sounded.

To prevent the alarm from sounding, when a door is opened by a legitimate user of the vehicle, it is necessary to provide a switch to de-energise the alarm circuit. The switch may be positioned on the exterior of the vehicle, so that it can be actuated with a key before the door is opened, or it may be positioned inside the vehicle, in which case, a time delay circuit prevents the alarm circuit from being energised for a period of time which is sufficient for the switch to be actuated by a legitimate user of the vehicle. On the other hand, an intruder, who does not know where the switch is located within the car, or who does not have a key for actuating the switch, is unable to prevent the alarm circuit from being actuated.

If, however, an intruder has a suitable key, or he knows where the switch is located within the car, then the alarm can be switched off and the value of the alarm device is lost.

It is an object of the present invention to provide an alarm and immobilising device for a motor vehicle which does not rely on the need for a key operated switch to switch off the alarm.

According to a first aspect of the present invention, an alarm and immobilising device for a motor vehicle having one or more doors leading to a passenger carrying compartment, an engine and an audible alarm device comprises a memory device containing a preset coded signal; a comparator device arranged to compare a coded signal applied thereto with said coded signal in the memory device; means for applying a coded signal to said comparator device; a circuit for actuating the alarm device; and a circuit for immobilising the engine, the alarm and immobiliser device being such that, with all the doors shut and the device switched on, the circuit for immobilising the engine is energised and, when subsequently one of the doors is opened, the circuit for immobilising the engine remains energised and, after a predetermined time interval, the circuit for actuating the alarm device is energised, unless a coded signal, which is the same as the preset coded signal in the memory device, is applied to the comparator device and, if the correct signal is applied within the time interval, the circuit for immobilising the engine is de-energised.

According to a second aspect of the invention, an alarm and immobilising device for a motor vehicle has two operating states, in the first of which the vehicle is electrically immobilised and, if a door of the vehicle is opened and a predetermined coded signal is fed into the device within a predetermined time interval, then the device reverts to a non-operating state in which the vehicle is not immobilised but, if a door is opened and the coded signal is not fed into the device within the predetermined time interval, then the device automatically changes to the second operating state, in which the vehicle remains immobilised and an alarm is sounded.

In one embodiment of the invention, a device suitable for alarming and immobilising a motor car, having a passenger carrying compartment which is closed by one or more doors and which is propelled by an internal combustion engine, employs a push-button arrangement for feeding the coded signal into the device. The push-button arrangement may consist of, say, ten push buttons numbered 0-9 respectively and, by operating say six of the ten buttons in sequence, a very large number of unique coded signals can be fed into the device. Alternatively, twenty six pushbuttons may be provided, each labelled with a different letter of the alphabet. Again, by choosing a word of, say, six letters, then a very large number of unique coded signals or "passwords" can be obtained by operating the push-buttons in sequence.If desired, the ten push-buttons, numbered 0-9 and the twenty six push buttons labelled A-z may be provided, so that the coded signal or "password" may consist of letters and numbers.

The push-buttons are conveniently mounted on a keyboard which is securely attached to the dashboard of the motor vehicle.

The device has a non-operating or OFF state and two operating states, namely READY and ACTIVATED.

An ON switch is actuated to change the device from its OFF state to its READY state, but the device is not in its READY state until at least one door of the vehicle has been opened and all the doors are subsequently closed. When it is in its READY state, the device immobilises the engine in some way by preventing the ignition circuit from being energised; thus, in the ready state, the vehicle is immobilised. When a door is opened to give access to the vehicle, the device automatically changes to the ACTIVATED state. In this state, the vehicle remains immobilised and, after a predetermined time interval of, say, 1 5 seconds, the alarm will be actuated unless, before the end of the time interval, a correct "password" is fed into the device by operating some of the push-buttons in the correct sequence.

If the correct "password" is fed into the device within the time interval, then the device is changed to its OFF state and the vehicle is no longer immobilised.

If the correct "password" is not fed into the device within the time interval, then the alarm sounds for a fixed period and the vehicle remains immobilised until the correct "password" is fed into the device.

The device is used to protect the engine compartment of the vehicle by providing a switch on the lid of the compartment. When the device is in its READY state, it is changed to its ACTIVATED state and the alarm is actuated immediately the lid of the compartment is opened.

Similarly the boot of the vehicle can be protected.

In order that the invention may be more readily understood it will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front elevation of a control panel of the device, and Figure 2 is a circuit diagram of the device.

Referring to Fig. 1, a control panel 1, for mounting in a convenient position in a motor car, has ten push-buttons 3, numbered 0-9 respectively, and twenty six push-buttons 5, labelled A-Z respectively, an ON switch 7, a CLEAR switch 9, three light emitting diodes (LED) 11, which serve to display information, four LEDs 1 3 which serve to illuminate the panel and a miniature loud-speaker 1 5.

The push-buttons 3 and 5 are for feeding a "password" of, say, six digits into the device.

The ON switch is for switching the device from an OFF state to a READY state, the CLEAR switch is for use if an incorrect pushbutton is pressed, and the speaker is for a tone feedback which sounds momentarily upon pressing any of the switches.

Installation There are three simple steps involved in installing this device in the car:- 1. Fitting the keyboard and the case enclosing the control system.

2. Installing a bonnet switch and switches on the rear doors of a four door vehicle, if required.

3. Wiring.

The keyboard may be fitted anywhere in the car. This is the only part of the device visible to anyone. The case may be installed anywhere out of immediate reach.

A bonnet switch is a switch installed in a way so as to contact when the bonnet is opened. This switch extends the protection to the engine compartment. It can be omitted if this extension is not desired. Similarly, the switches on the rear doors extend the protection to all the doors of the vehicle but may be omitted if this is not required.

Power Supply It is either OFF or READY, unless it has been ACTIVATED. Since it is always left in one of these two states, this device is designed to consume almost no electricity in these states. The amount dissipated is less than 1 micro-watt.

Operation The OFF nonsperating state In this state, the device is inactive, and the.

only active switch on the keyboard is the ON switch, and this only when the car ignition is switched off. When the car is in use, this switch is also inactive, leaving the whole keyboard inactive, as a precautionary measure. This will ensure that the alarm is not accidentally switched ON when the car is in motion.

The READY state When the engine is switched off, the speaker 1 5 sounds a pulsating bleep for two seconds, reminding the driver to switch on the alarm. The ON switch 7 is now active. In order to change the state to READY, so as to commence protection, this switch has to be pressed before leaving the car. However, the device will not function until a door is opened and closed, allowing the person to leave the car before starting protection. When the ON switch is active, and is pressed, one of the LEDs 11, coloured red, will switch on, indicating acceptance of the ON command. This LED will switch off when all the doors have been shut, assuring the owner that the device has moved to the READY state. If any of the doors are accidentally left open, the alarm will sound, in approximately ninety seconds, warning the owner of this mistake.The ON LED helps to prevent this from happening, since it will not switch off unless the doors have been shut.

The instant the READY state is reached, the car is electrically immobilised, and this immobilisation is maintained until the correct "password" is fed into the keyboard. For the device to move to the ACTIVATED state, the following possibilities exist: 1. One of the doors is opened, the ACTI VATED state is immediately triggered and a fixed time interval of, say, 1 5 seconds is allowed for the "password" to be fed into the keyboard. A pulsating bleep, lasting three seconds, is sounded by the keyboard speaker 15, reminding the owner to feed-in the "password" by operating the appropriate pushbuttons 3, 5. If this is not done, the warning alarm will be triggered and the car horn or siren sounded, accompanied by flashing lights, if required. This warning alarm will i automatically switch off after one minute, so as not to go on continuously if the owner is not there to activate it. If the door is left open, however, the alarm will stay on even past the one minute limit, until the door is shut. It will ensure that an intruder will not succeed by leaving the car door open and hiding, hoping that noone claims the car during the warning period. After the alarm has sounded for one minute, or the car door is shut, whichever comes later, the alarm will switch back to the READY state to regain normal protection. It should be noted that, during all these events the car is continuously immobilised, and the engine will not function until the correct "password" is fed.

2. The bonnect is opened. This moves the device to the ACTIVATED state, and triggers the warning alarm simultaneously, maintaining immobilisation throughout. The subsequent events are the same as described in (1) above.

3. The key switch is turned in an attempt to start the car. The same occurs as in (2) above.

This enables the owner to leave the key in the ignition key switch with complete confidence, since the car keys serve no purpose when the car is protected by this security device.

The centre information LED 11, which is yellow, along with the four illuminating LEDs 13, switch on as soon as the device moves to the ACTIVATED state. The yellow LED, along with the three second bleep, reminds the owner that this state is reached and the keyboard is ready to accept the "password". The remaining information LED, which is green, switches on momentarily indicating the acceptance of the password, when it is correct, and the de-activation of the alarm.

Referring now to Fig. 2, the push-button switches 3, 5 are represented by switches SW1-SW10, the ON switch 7 is represented by switch SW12, the CLEAR switch 9 by SW11 and the door switches by reference 1 7.

A diode arrangement 19, consisting of six diode pairs, provides an input to an integrated circuit IC1. Six of the push-buttons SW1-SW10, corresponding to the six alarm numbers of the "password", are hard wired to corresponding ones of the diode pairs, thereby inputting the chosen six figure number into the comparator. A second integrated circuit IC2 has a pair of flip flops FF2 and FF1 built into it and a third integrated circuit IC3 has a pair of flip flops FF1 and FF2 built into it. When the switches SW 1 -SW 1 0 are pressed to prevent the alarm from being actuated, transistor TR3 clocks FF2 in IC2 which in turn clocks IC1 whenever any of the switches is pressed.If the switch which is pressed does not correspond to the corresponding number of the "password", TR1 is switched on and it clocks FF1 of IC2. If the correct switch is pressed, TOR 1 stays off. When all of the switches have been pressed to feed in the "password", IC1 checks via transistor TR5 whether FF1 has been clocked. If it has not been clocked, corresponding to a correct input of the "password", a pulse is sent to IC3 to reset it to the non-operating state.

FF2 of IC2 serves to eliminate switch bounce errors caused by faulty operation of the switches SW1-SW10.

Relay 1, fed by a transistor To17, serves to by-pass the ignition switch on the car and thus immobilise the car when the contact of the relay is open. In an alternative arrangement, the relay can short out the contacts on the distributor, thus preventing any high voltages from being supplied to the sparking plugs. Relay 1 is open in the READY and ACTIVATED states. Relay 2, fed by transistor To16, serves to connect the battery supply to the audible alarm during the warning period of the ACTIVATED state of the device.

There are several timers in the device. A timer, constituted by capacitors C9, C10, resistor R23 and transistor TR1 2, has a period of about ninety seconds and the period commences when the ON switch SW12 is operated. If, at the end of the ninety second period, a door has not been opened, the ON command is disregarded and the device reverts to the non-operating state. If, however, a car door has been opened but not closed, then, at the end of the ninety second period, the device will move to the ACTIVATED state and an alarm signal is produced on the speaker 1 5 to remind the user of this fact.

This will help to warn the owner that the door is still open.

When the device is in its READY state and a door is opened, then a timer, constituted by transistors TR14, TR15, capacitor Cl 1 and variable resistor VR2, produces a delay of, say, fifteen seconds before actuating the alarm. It is desirable that the alarm signal should pulsate, so an oscillator, constituted by capacitor C13, transistor TR16 and variable resistor VR3, serves to open and shut the relay 2 to produce the pulsating tone.

A timer, constituted by capacitor C12, resistor R28 and variable resistor VR1, is started when the alarm commences. It has a period of, say, one minute. At the end of the period, the timer switches off the alarm and the device reverts to the READY state.

An integrated circuit IC4 is an oscillator for driving the miniature speaker 1 5. As mentioned above, integrated circuit IC3 has a pair of flipflops FF1 and FF2. FF1 corresponds to the READY or ACTIVATED state and FF2 corresponds to the OFF and READY state.

In a modified arrangement, it is arranged that, if an intruder enters the car without opening the door, say, by breaking one of the windows, and attempts to operate the ignition key switch, then the bonnet switch unit is actuated and the device reverts to its ACTI VATED state immediately. If protection is required for the windows, a thin conductive tape is applied to each window and, if the tape is broken, the device immediately causes the alarm to be actuated.

In a modified arrangement, under certain circumstances, such as the vehicle being serviced, one might wish to make the key board inactive, so that no-one will accidentally switch on the alarm and not know how to deactivate it. For the key board to become inactive, the ON switch has to be pressed and held-in for five seconds. Once moved to the in-active state, the key board speaker sounds a bleep, and the ON LED switches off. This state can be kept indefinitely and does not affect normal operation of the vehicle, nor does the normal operation of the vehicle affect it. In order to activate the key board and put the alarm back into operation, the CL switch has to be pressed and held in for ten seconds.

An optional arrangement allows the customer to programme his own "password" or combination number. For this purpose, a fusibly-linked diode array memory is fitted into the circuit. Programming is done by pressing the CL switch and, holding it in, pressing the desired "password", being less than or equal to nine letters or digits. Once this is done, still holding in the CL switch, the ON switch is to be pressed. This permanently disables to programming unit and puts the alarm in opera tion mode.

Claims (10)

1. An alarm and immobilising device for a motor vehicle having one or more doors leading to a passenger carrying compartment, an engine and an audible alarm device, comprising a memory device containing a preset coded signal; a comparator device arranged to compare a coded signal applied thereto with said coded signal in the memory device; means for applying a coded signal to said comparator device; a circuit for actuating the alarm device; and a circuit for immobilising the engine, the alarm and immobiliser device being such that, with all the doors shut and the device switched on, the circuit for immobilising the engine is energised and, when subsequently one of the doors is opened, the circuit for immobilising the engine remains energised and, after a predetermined time interval, the circuit for actuating the alarm device is energised, unless a coded signal, which is the same as the preset coded signal in the memory device, is applied to the comparator device and, if the correct signal is applied within the time interval, the circuit for immobilising the engine is de-energised.

2. An alarm and immobilising device for a motor vehicle having one or more doors leading to a passenger carrying compartment, wherein the alarm has two operating states, in the first of which the vehicle is electrically immobilised and, if a door of the vehicle is opened and a predetermined coded signal is fed into the device within a predetermined time interval, then the device reverts to a nonoperating state in which the vehicle is not immobilised but, if a door is opened and the coded signal is not fed into the device within the predetermined time interval, then the device automatically changes to the second op erating state, in which the vehicle remains immobilised and an alarm is sounded.

3. An alarm and immobilising device as claimed in claim 1 or 2, in which the coded signal is fed into the device by the user operating a plurality of push-button switches in a required sequence.

4. An alarm and immobilising device as claimed in claim 1, in which the circuit for immobilising the engine comprises a relay in series with the contacts of the ignition key switch, which relay provides an open circuit in the READY and ACTIVATED states irrespective of the condition of the key switch.

5. An alarm and immobilising device as claimed in claim 1, in which the circuit for immobilising the engine comprises a relay which, when not energised in the READY and ACTIVATED states, provides a short circuit across the breaker points of the distributor of the engine.

6. A device as claimed in claim 2, in which the lid of the engine compartment has a switch which is actuated when the lid is opened and, when the switch is actuated, the device automatically changes from its first to the second operating state and the alarm is sounded immediately.

7. A device as claimed in claim 2, in which the windows of the vehicle have switches associated therewith and breaking of a window actuates a switch causing the de vice to change automatically from its first to the second operating state and the alarm is sounded immediately.

8. A device as claimed in any preceding claim, in which an oscillator and speaker are provided and indicate, by an audible signal when the device changes to its second operat ing state, that a coded signal should be en tered into the device.

9. A device as claimed in claim 3, in which the push-buttons initially form part of a fusible linked programmable device and, after the switches have been operated in the re quired sequence for the first time, the link is fused to disable the programmable device and thereby prevent the sequence from being changed.

10. In or for use in a motor vehicle, an alarm and immobilising device substantially as hereinbefore described with reference to the accompanying drawings.