JPH02127890A - Restoration signal transmission system for signal circuit - Google Patents

Abstract

PURPOSE:To release a load relay completely even if an open current of the load relay is small by connecting an earth transmission circuit to an output of a constant resistance circuit able to be switched into a low resistance state and a high resistance state with a control signal and sending an earth level to the output for a prescribed time when the constant resistance circuit is in the high resistance state. CONSTITUTION:The constant resistance circuit 1 reaches a low resistance state when a control signal CONT 1 sent from a control circuit 13 through a control line 14 is low level to a resistance changeover circuit 2 and reaches a high resistance state when the CONT 1 goes to a high level. Moreover, an earth transmission circuit 8 is connected to an output terminal 12 of the constant resistance circuit 1 and earth level is given to the output terminal 12 of the constant resistance circuit 1 when a control signal CONT 2 sent from the control circuit 13 through the control line 15 goes to a high level. When the constant resistance circuit 1 is at high resistance state, an earth level is sent to the output terminal for a prescribed time only. Thus, even if the open current of the load relay is small, the relay is surely released.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a trunk circuit of a telephone exchange and a power supply circuit and loop forming circuit of a PCM carrier connected to the trunk of the exchange, and in particular to a power supply circuit and a loop forming circuit of a PCM carrier connected to the trunk of a telephone exchange. This relates to a recovery signal sending method.

[Conventional technology]

As a conventional circuit of this type, a relay drive circuit using a constant resistance circuit will be explained using FIG. 3 as an example. As shown in FIG. 3, this circuit includes a constant resistance circuit 1 that can be switched between a low resistance state and a high resistance state by a control signal. It is configured to operate the load relay 11 by supplying a current of . In Figure 3,
7 is a driving battery; 9 and 10 are respectively the ground insulation resistance of the line and the ground stray capacitance; 13 is a control circuit; and 14 is a control line connecting this control circuit 13 and the resistance value switching circuit 2 of the constant resistance circuit 1. , the control signal C0 output from the control circuit 13
The NT switches the internal equivalent resistance value of the constant resistance circuit 1 between low resistance and high resistance.

[Problem that the invention seeks to solve]

However, in the conventional circuit described above, since the constant resistance circuit 1 includes the bias resistors 3 and 4, leakage current flows as an output current even if the transistor 6 is cut off. As a result, if the winding resistance value of the load relay 110 is high and the open current value is lower than the muddy current, there is a problem that the load relay will not recover and will fail.

In addition, if the length of the connection line to the load relay 11 is long, there is a problem that the load relay 11 will not be restored immediately even if the transistor 6 is cut off due to the charge accumulated in the stray capacitance 10 of the line. was there.

[Means to solve the problem]

In order to solve this problem, the restoration signal sending method of the signal circuit according to the present invention includes a constant resistance circuit that can be switched between a low resistance state and a high resistance state according to a first control signal, and a constant resistance circuit that can switch between a low resistance state and a high resistance state according to a first control signal. a ground air sending circuit for connecting ground air to the output terminal of the circuit in accordance with a second control signal; and the first earth air sending circuit for driving and controlling these constant resistance circuits and the ground air sending circuit. and a control circuit that respectively generates a second control signal, and when the constant resistance circuit is in a high resistance state, earth air is sent to the output terminal for a predetermined period of time.

[Effect]

Therefore, in the present invention, when the constant resistance circuit is in a high resistance state, by sending earth air to the output terminal for a predetermined period of time, recovery can be ensured even if the open current value of the load relay is small. It becomes possible to do so.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an example of the restoration signal sending method according to the present invention. In FIG. 1, the constant resistance circuit 1 is
A transistor 6, a bias resistor 3.4 for giving a bias current to the transistor 6, an emitter resistor 5 connected to the emitter of the transistor 6, and an internal equivalent resistance value of the constant resistance circuit, which is divided into low resistance and high resistance. It is constituted by a resistance value switching circuit 2 for switching to resistance. This constant resistance circuit 1 has a control circuit 13 in its resistance value switching circuit 2.
Control signal C0NT1 sent through the control line 14
When it is at a lower level, it is in a low resistance state, and when it is at a high level, it is in a high resistance state. Also,
A ground air sending circuit 8 is connected to the output terminal 12 of the constant resistance circuit 1, and when the control signal C0NT2 sent from the control circuit 13 through the control line 15 becomes high level, Earth air is applied to the output terminal 12 of the resistance circuit 1. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Next, the operation of the above embodiment will be explained with reference to FIG. Here, in FIG. 2(a), the control signal C0NT sent by the control circuit 13 to each control [14 and
1. A timing chart of C0NT2 is shown. first,
The control circuit 13 outputs control signals C0NTl and C0NT2.
When both are set to the lower level (region 2 in FIG. 2), the constant resistance circuit 1 becomes a low resistance state and the earth air sending circuit 8 becomes an OFF state. In this case, since the load relay 11 is supplied with a current higher than the current from the battery 7, the load relay 11 operates in the same manner as in the conventional example. And during this operation (
When restoring the load relay 11 in the area (■), the control circuit 13 outputs the control signal C0NT1 as shown in FIG.
At the same time, the control signal C0NT is set to high level.
2 is set to a high level (region ■ in FIG. 2), the constant resistance circuit 1 enters a high resistance state, and the earth air sending circuit 8 sends earth air to its output terminal 12.

As a result, the charge accumulated in the stray capacitance IIi'10 of the line is forcibly discharged, and the leakage current flowing through the load relay 11 becomes completely zero. Next, after setting the control signal C0NT2 to high level for a predetermined time T, the control signal C0NT2 is set to low level (area ■ in FIG. 2), and output terminal 1
2 is in a high resistance state with respect to the ground (GND) and the battery 7 in terms of direct current and alternating current. As a result, load relay 1
The current flowing through the load relay 11 is limited to less than the open current, and the load relay 11 can be reliably restored.

〔Effect of the invention〕

As explained above in 1-1, the present invention connects an earth air sending circuit to the output of a constant resistance circuit that can be switched between a low resistance state and a high resistance state according to a control signal, and the constant resistance circuit is switched to a high resistance state. By sending earth air to the output for a predetermined period of time, it is possible to completely restore the load relay even when the open current value is small.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG.
The figure is a circuit diagram showing an example of the conventional technology. 1φ...constant resistance circuit, T...φ, battery, 8...-earth air supply circuit, 11...load relay 13...control circuit, 14.15...control line . Patent applicant: NEC Corporation

Claims (1)

[Claims] a constant resistance circuit that can be switched between a low resistance state and a high resistance state by a first control signal; and a ground air sending circuit for connecting ground air to an output terminal of the constant resistance circuit in accordance with a second control signal. , a control circuit that generates the first and second control signals for driving and controlling the constant resistance circuit and the ground air sending circuit, respectively, and when the constant resistance circuit is in a high resistance state, the output thereof is A recovery signal sending method for a signal circuit, characterized in that earth air is sent to a terminal for a predetermined period of time.