JPS6019177B2 - Telephone line core comparison switching circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a core wire comparison detector for a subscriber's telephone line, and more specifically, in a main distribution frame (hereinafter referred to as MDF) such as in a telephone office, when a handset is in a no-call state. This invention relates to a sliding door circuit that allows fiber comparison of subscriber telephone lines even in the case of

An example of a subscriber telephone line is shown in FIG.

Although FIG. 1 shows a circuit with two bare wires A and B, a considerable number of bare wires are connected to an actual MDF. The subscriber's telephone line normally uses bare L and negative wires, and when there is no call, the hook switch IA of handset 1 is on and the L wire is grounded, and the negative power supply 2 is applied to the L2 wire. This makes it unbalanced. When you pick up handset 1 to make a call,
Hook switch IA is turned on, forming a circuit of relay contact 3, mine coil IB, hook switch IA, relay contact 4, subscriber relay RL, and negative power supply 2. This turns on subscriber relay RL, turns on relay contact 5, and forms a circuit of relay saddle point 5, relay RL, and negative power supply 2. When the relay R} is turned on, it switches the relay contacts 3 and 4, connects the negative power supply from the exchange 6 to the L line and the L line, respectively, and creates an equilibrium state when looking at the exchange side from the terminals 7 and 8 of the MDF. It transmits signals, etc. In the call state, the relay contacts 3 and 4 are switched, so the subscriber relay RL is turned off, but the relay RL continues to keep the relay contacts 3 and 4 switched by a self-holding circuit. In the embodiment of FIG. 1, the negative power supply 2 is -4
It is the island.

Therefore, in a no-call state, terminal 7 of the L line is OV, L2
The terminal 8 of the line is a -48V unbalanced circuit, and during a call, the voltage from the exchange 6 is not necessarily the same due to voltage drops due to the resistance of the L line and the L line, but for example, the voltage at terminal 7 is about the same. 5V, and the voltage at terminal 8 is about -43V, resulting in a balanced circuit. As mentioned above, the subscriber's telephone line is an unbalanced circuit when there is no call.

By the way, when attempting to perform fiber comparison for the L, line, and L2 line of the subscriber's telephone line, the following problem arises. The L wire of each bare wire is grounded in a non-call state.
Therefore, for example, if you add the fiber comparison signal to terminals 7 and 8 on the bare wire A side in Figure 1, a signal will also appear on terminal 7 on the bare wire B side, and you will know which bare wire's L wire is being compared. I don't understand. However, when the communication state is established, the relay contacts 3 and 4 are switched, and only the bare wire in the communication state becomes an independent balanced circuit. In other words, fiber comparison cannot be performed in a no-call state, but
Once you are on the phone, you can compare the core wires. This invention is intended to solve the above-mentioned problem.The subscriber's telephone line detects whether the call state is a no-call state, and when the call state is a no-call state, the relay contact 9 is turned on as shown in FIG. A resistor R, which has the same function as the current state, is forcibly connected to the terminals 7 and 8, and the state remains the same during the communication state, so that the wires can be compared. A detailed explanation will be given below based on the drawings. FIG. 2 is an explanatory diagram of the configuration of a switching circuit according to an embodiment of the present invention.

In the figure, 7 and 8 on the dashed line are terminals of a part of the MDF, and the right side of the terminals 7 and 8 is the switching circuit according to the present invention. Reference numeral 10 in the figure is a reference power supply, which is set to a voltage lower than the voltage at terminal 7 when there is no call, and higher than the voltage at terminal 7 when there is a call. In the embodiment shown in FIG. 2, the voltage of the reference power supply 10 is approximately 1V. 11 is a comparator, one input end of which is connected to terminal 7, and the other input end connected to a reference power source.

When the voltage at the terminal 7 is higher than the voltage at the reference power source 10, the comparator 11 outputs a logic level "1" and outputs the logic level "1" from the terminal 7.
When the voltage of the reference power supply 10 is lower than the voltage of the reference power supply 10, a logic level "0" is outputted to its output. 12 is a detector which detects whether or not the switching circuit according to the present invention is connected to terminals 7 and 8; when it is connected, it outputs a logic level "1", and when it is not connected, it outputs a logic level "1"; When this happens, a logic level "0" is output to its output.

FIG. 3 shows an example of the circuit of the detector 12.

Now, when the detector 12 is not connected to the terminals 7 and 8, the logic level "1" is applied to the two inputs of the off circuit 12A by the resistors R2 and R3, and the output of the off circuit 12A is at the logic level "1". 1”. Either terminal 7 or 8 1
Even when the detector 12 is connected to the OFF circuit 12A, the output of the OFF circuit 12A is at the logic level "1". When the detector 12 is connected to both terminals 7 and 8, the ground voltage of the L line on the terminal 7 side is applied to one input of the OR circuit 12A, and -48V of the L line on the terminal 8 side is connected to the resistor R4 and the diode D. , becomes approximately OV and is added to the other input of the OR circuit 12A, so the output of the OR circuit 12A becomes logic level "0". In addition, the third
The diode D2 in the figure is for keeping the input of the OR circuit 12A at logic level "0" even if a negative voltage appears on the L line. 13 in Fig. 2 is a flip-flop, which has a set and reset terminal on the input side, and a detector 12 at the reset terminal.
The output of the comparator 11 is connected to the set terminal.

When the input to the reset terminal is at logic level "1", flip-flop 13 is reset, and its output is at logic level "0", turning off relay RL. When the input to the reset terminal is at logic level "0", the reset of the flip-flop 13 is released, and the output of the flip-flop 13 is stopped by the input to the set terminal. When the input to the set terminal is at logic level "1", the output of flip-flop 13 also becomes logic level "1", turning on relay RL. When the input to the set terminal is at logic level "0", the output of flip-flop 13 is also at logic level "0", keeping relay RL in the off state. When relay RL turns on and off, it makes and breaks relay contact 9 and connects resistor R to terminal 7.
Enter 8 and cut.

That is, when the switching circuit of the present invention is connected to the MDF shown in FIG. 1, logic level "0" is applied to the reset terminal of flip-flop 13, and the reset terminal of flip-flop 13 is released.

When the L line and the - line are unbalanced, the terminal 7 is at ground potential, so the output of the comparator 11 becomes logic level "1". Therefore, the output of flip-flop 13 also becomes logic level "1", turning on relay RL3 and terminals 7 and 8.
A resistor R, is connected in parallel with . When resistor R is connected,
As explained in FIG.
The state is the same as when A is turned on, and the exchange system becomes a balanced circuit. In a balanced circuit, a voltage of approximately 15V appears at terminal 7, and the output of comparator 11 becomes logic level "0", but unless flip-flop 13 is reset, its output is logic level "1", and relay RL3 is turned on. Continue to maintain.
Furthermore, if the switching circuit of the present invention is connected to a place where the L and L2 lines are already in a balanced circuit, the reset of the flip-flop 13 will be canceled, but since the voltage at terminal 7 is about 1 W, the comparison will be made. The output of the flip-flop 11 is at a logic level of ``0.'' The output of the flip-flop 13 is also at a logic level of ``0'' and the relay RL3 is on.A resistor R is further connected in parallel to the switching system, which is a balanced circuit. There isn't.

To perform a fiber comparison of a subscriber's telephone line as shown in Figure 1,
Connect the switching circuit of this invention to terminals 7 and 8 of the MDF, create a balanced circuit by looking at the AC manufacturing system from terminals 7 and 8, and then send a core contrast signal to the handset 1 side from terminals 7 and 8. Just measure it.

It should be noted that if the input impedance of the switching circuit is made sufficiently large according to the present invention with respect to the impedance on the handset 1 side including the L, line and - line, it will not affect the subscriber's telephone line. Also, when the L line and the - line are in a talking state, dial-in pulses etc. may come in, but if you insert a low-pass filter etc. between terminal 7 and comparator 11, dial-in pulses etc. Malfunctions can be prevented. As explained above in detail, according to the present invention, a subscriber's telephone line that is unbalanced due to no calls can be forcibly made into a balanced circuit and this state can be maintained. It becomes possible to perform fiber comparison, and has the advantage that maintenance and inspection of subscriber telephone lines can be carried out efficiently.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a subscriber's telephone line, FIG. 2 shows a configuration diagram of an embodiment of the present invention, and FIG. 3 shows an example of the circuit of the detector 12. 1... Handset, IA... Hook switch, 2... Power supply, 3, 4, 9...
Relay contact, 6...Exchange machine, 7, 8...
・Terminal, 10...Reference power supply, 11...
Comparator, 12...Detector, 13...Flip-flop, L. , L2...Telephone line, MD
F... Main distribution board, R. ...Resistance, RL
．． ...Subscriber relay, RL2...Self-holding relay, RL...Relay. Figure 2 Figure 3 Figure 1

Claims (1)

[Claims] 1 When there is no call, ground the L_1 line and connect a negative voltage to the L_2 line to create an unbalanced circuit, and when there is a call, turn on the handset switch to connect the negative power from the converter to the L_1 line, respectively. In a telephone line connected to the L_2 line to form a balanced circuit, the above L_1 when there is no call
A reference power source having a voltage lower than the terminal voltage of the line and higher than the terminal voltage of the L_1 line during a call state, one end of the input is connected to the terminal of the L_1 line, and the other end of the input is connected to the reference power source. A comparator to be connected, a flip-flop to which the output of the comparator is connected, a relay to which the output of the flip-flop is connected, and when the relay is turned on, the L_1
and a relay contact that connects a resistor in parallel between the line and the L_2 line, and when the voltage of the L_1 line is higher than the voltage of the reference power source, the relay is turned on by the output of the comparator, and a call state is established. By connecting the resistor, which has the same function as , the L_1 line and the L_2 line are made into a balanced circuit and that state is maintained, and when the voltage of the L_1 line is lower than the voltage of the reference power supply, the relay remains off. 1. A switching circuit for comparing core wires of a telephone line, characterized in that: