FR2870070A1 - TEST METHOD FOR LINE EQUIPMENT PROVIDED WITH A DETACHING DETECTOR AND LINE EQUIPMENT FOR IMPLEMENTING THE SAME - Google Patents

Abstract

The invention relates to methods for testing analog telephone line equipment, in particular for detecting failures in their on-hook / on-hook detection circuit (112). The method involves isolating (103) the equipment from the telephone line, to apply (108) the normal battery signal to it and to apply to one of the wires (202) connecting the hybrid circuit (107) to the detection circuit (112) a test signal making it possible to reverse the polarity at the input of this detection circuit. If this circuit fails, its output logic signal (Vs) remains stationary, indicating this failure. Using a high repetition rate test signal, it is also possible to test the operation of the bell signal cut-off filter (312), thereby removing the usual equipment test relay (105).

Description

TEST METHOD FOR LINE EQUIPMENT

HAVING A DETACHING DETECTOR

  AND LINE EQUIPMENT FOR IMPLEMENTATION

  The present invention relates to test methods for analog telephone line equipment, more particularly for those having a stall detector using a voltage comparator and a filter for preventing this detector from operating on the ring signal. It also relates to line equipment adapted to implement this method.

  FIG. 1 shows a conventional line equipment intended to be connected by a telephone line L1 / L2 101 to a basic telephone set, ie which operates on an ordinary analog line, as opposed to systems of the type ISDN or ADSL for example. Lines and organs for transmitting and receiving voice signals between this equipment and the switch are known and have not been shown to simplify the figure and because they do not interfere with the invention.

  The telephone line is connected at the input of the line equipment to a surge protection device 102, of known type.

  This device 102 is connected to a line test relay 103. This relay isolates the line equipment from the telephone line, to connect it to a line test bus 104.

  A second equipment test relay 105 makes it possible to test the operation of the line equipment, in particular the off-hook / on-hook function, and more particularly the comparator of the stall detecting circuit 112, or the hang-up circuit, of the telephone set connected to the line equipment, isolating the input of the hybrid network 107 to connect it to an equipment test bus 106.

  Outside these test periods, this relay 105 thus connects the line, from the relay 103, to the input of the hybrid network 107.

  This hybrid network is connected via a ring relay 108 to either a supply circuit 109 or a ring circuit 111. In this illustrative example, this circuit 109 is connected to the two switching circuits of FIG. this relay, and corresponds to one, to the supply of Vbat, and for the other, to + of this power supply. However, in a known manner, the - is the hot spot and the + is connected to the general mass 110.

  The controls of these various relays are known and are therefore not shown in the figure.

  The output of the hybrid network 107 is connected to the circuit 112 for detecting stall / hang-up. A voltage Vcc, applied to the circuit 112 by a connection 114, makes it possible to operate it. During the detection of the stall, the circuit 112 sends a logic signal on an output connection 113. When detecting the hangup, it transmits a complementary logic signal.

  The use of a test relay 105 entails an additional cost which is all the more important since there are as many relays as there are line equipment and thus telephone sets served by the system.

  To reduce these costs by eliminating these test relays, the invention proposes a test method for analog telephone line equipment connected to a switch comprising a control computer, this equipment comprising a line test relay for isolating the telephone line equipment, a hybrid resistor network, a ringing relay for applying a VBAT power signal to the equipment, and a stall / hook detection circuit connected to the hybrid circuit by two wires respectively carried to voltages VA and VB, this detection circuit delivering a logic signal stall / hang-up, mainly characterized in that, under the control of said computer, the line test relay is opened to isolate the equipment, it opens the relay signal to apply the power signal and is applied on one of said two son a test signal to reverse the polarity between VA and VB, and in that the switching of said logic signal in response to the test signal is tested, indicating that the at least one stall / hang detecting circuit is functioning properly.

  According to another characteristic, the stall / hook detection circuit comprising a low-pass filter followed by a comparator, the test signal is formed of an alternating signal with a repetition frequency lower than the filter cut-off frequency to control the operation of the comparator, followed or preceded by an alternating signal with a repetition frequency higher than this cutoff frequency to control the operation of the filter.

  The invention also proposes analog telephone line equipment for the implementation of this method, mainly characterized in that said line test relay is directly connected to said hybrid resistor network without the interposition of a test relay. equipment, and in that the equipment comprises a test circuit for applying on one of the two connection wires connecting this network to the stall / hook detector a set and interrupted supply voltage under the control of a signal of test.

  According to another characteristic, said test circuit is formed of a transistor fed by said voltage to reduce this voltage on said connection wire via a first resistor, and the transistor is controlled by said test signal by intermediate of a second resistance.

  Other features and advantages of the invention will become apparent from the following description, with reference to the appended figures which represent: FIG. 1, the simplified diagram of a known line equipment; Figure 2, the diagram of Figure 1, modified according to the invention; and - Figure 3, the diagram of the organs of Figure 3 contained in the dotted frame 115.

  FIG. 2 shows a line equipment enabling the method according to the invention to be implemented. It can be seen that this line equipment differs from that shown in FIG. 1 only in the removal of the operating test relay 105 and by the addition in the dotted box 115 of a test device formed of a few components.

  The more detailed diagram of the organs contained in this dashed frame 115, shown in FIG. 3, makes it possible to explain the operation of the method according to the invention.

  The output of the hybrid circuit 107 is connected to the input of the circuit 112 by two connection wires 201 and 202 respectively connected to the potentials VA and VB.

  The test device mentioned above is, in this embodiment, connected to the wire 202, but it could be connected to the wire 201 by making the necessary adaptations on the polarities.

  This device is formed of a resistor 203 connected on one side to the wire 202 and supplied from the other from a voltage source Vcc by a transistor 204. A test signal is applied on the basis of this transistor by a resistor 205. This transistor is in this example a bipolar transistor, but any other technology could be suitable. The values of the resistors 203 and 205 are calculated in known manner as a function of the values of the other parameters and of the mode of operation explained below.

  The off-hook / on-hook detection circuit 112 essentially comprises a voltage comparator 212 and a filter 312. This filter, which in this embodiment of the active type, can be activated or deactivated by an activation signal applied by a connection. 313. It receives the signals from the hybrid circuit 107 to eliminate the ringing signals. The comparator 212 is connected to the output of this filter, which prevents it from switching on the ringing signals when sending the call signal.

  In a known manner, when the telephone set connected to the line equipment picks up, the voltage between VA and VB is reversed. This inversion is detected by the comparator 212 which emits at its output a logic signal VS which indicates this stall. On the hang-up, the operation is reversed. This logic signal, when established, is a stable signal without transition.

  To test the operation of the comparator 212, the invention proposes, after having disconnected the equipment from the line via the relay 103 and applied the battery voltage via the relay 108, to send on the basis of the transistor 204 a logic test signal 206 formed of an alternation of 0 and 1 respectively corresponding to the ground and the voltage Vcc. To avoid the influence of the filter 312, it will preferably be deactivated. It will also be possible, if necessary, to use for the test signal 206 a repetition frequency which is much lower than the cut-off frequency of the filter. These operations are carried out simply by programming the control computer of the switch to which the line equipment is connected.

  When the transistor 204 is blocked by the test signal, the voltage VB is not changed by the test circuit and the voltage difference VA VB is positive, since the line is not connected to the equipment, which corresponds to the on-hook state. The logic signal VS at the output of the comparator 212 thus indicates to the computer that this state is on-hook.

  When the transistor 204 is unblocked at the change of state of the test signal, the test circuit applies on the wire 202, from the voltage Vcc, a voltage sufficient to raise the voltage VB above the voltage VA. The values of Vcc and of resistance 203 are calculated, in a known manner, to obtain this voltage inversion. The voltage difference VA - VB thus becomes negative, which simulates an off-hook condition. The logic signal VS thus switches to indicate to the computer this off-hook state.

  If this signal VS does not switch to the change of state of the test signal, it means that the on-hook / off-hook detection system is defective. The defect most often concerns the comparator 212, but it may also concern the hybrid circuit 107 or the filter 312.

  It would be enough in fact to a single change of state on the test signal to test this operation, but it will preferentially use a repetitive state change at a slow rate, much lower than the cutoff frequency of the filter 312.

  The control computer of the switch to which the line equipment is connected can thus very easily, by detecting this absence of response of the output signal VS to the test signal, determine that the on-hook / off-hook detection circuit of this equipment of line is defective. This detection will be done by simply programming this calculator.

  The method according to the invention also makes it possible to test the correct operation of the filter 312. For this, a test signal 206 is used, the repetition frequency of which is here considerably greater, preferably 10 times, than the filter cut-off frequency. Under these conditions, the voltage difference VA - VB switches itself to this repetition frequency which generates a square signal which, after filtering by the filter 312, gives a continuous component with possibly a very small residual alternating with the repetition frequency . This does not make it possible to switch the comparator 212 and the VS output signal remains constant. The control computer detects this lack of response and the interpreter, in relation to the repetition frequency that he himself imposed, as a good operation of the filter. On the other hand, a switchover of the output signal VS to the rhythm of the test signal indicates a malfunction of this filter. Here again this detection will be done by simple programming of the computer.

  In order to be able to control both the operation of the comparator 212 and the filter 312, it will suffice to proceed in two successive steps by first sending a test signal with a low repetition frequency and then a test signal with a high repetition frequency, or vice versa.

  The invention thus allows for each line equipment to remove the test relay 105 as well as the bus and its associated electronics, at the cost of a few low-cost components added to each equipment, and some programming lines added in the program of the switch computer which is connected to all line equipment.

Claims (4)

  1 - Test method for analog telephone line equipment connected to a switch comprising a control computer, this equipment comprising a line test relay (103) for isolating the equipment of the telephone line, a hybrid resistor network (107), a bell relay (108) for applying to the equipment a VBAT power signal (109), and a stall / hook detecting circuit (112) connected to the hybrid circuit by two wires (201,202 ) respectively carried at voltages VA and VB, this detection circuit delivering a logic signal (Vs) stall / hang-up, characterized in that, under the control of said computer, the line test relay is opened to isolate the equipment, the ringing relay is opened to apply the supply signal and a test signal is applied to one of the two said son (202) to reverse the polarity between VA and VB, and that the we test l t switching of said logic signal in response to the test signal, which indicates the proper operation of at least the stall / hook detection circuit.   2 - Process according to claim 1, characterized in that, the stall / hook detection circuit comprising a low-pass filter (312) followed by a comparator (212), the test signal is formed of an alternating signal with a repetition rate lower than the filter cut-off frequency to control the operation of the comparator, followed or preceded by an alternating signal with a repetition frequency higher than this cut-off frequency to control the operation of the filter.   3 - analogue telephone line equipment for implementing the method according to any one of claims 1 and 2, characterized in that said line test relay (103) is directly connected to said hybrid resistor network (107) without the interposition of an equipment test relay (105), and in that the equipment comprises a test circuit (203-205) for applying to one of the two connecting wires (226, 202) connecting this network at the detector stall / hookup a supply voltage (Vcc) established and interrupted under the control of a test signal.   4 - analog telephone line equipment according to claim 3, characterized in that said test circuit is formed of a transistor (204) supplied by said voltage (Vcc) to reduce this voltage on said connection wire (202) by the intermediate of a first resistor (203), and that the transistor is controlled by said test signal via a second resistor (205).