JPH01318342A - Incoming signal supply circuit - Google Patents

Abstract

PURPOSE:To prevent the production of a surge voltage when an incoming signal is interrupted by not using a relay but using a semiconductor element as a means for interruption switching of a signal from an incoming signal generation source. CONSTITUTION:The 2nd switch SW2 comprising SCRs 6a, 6b is connected to a speech current supply line L1 between a loop detection circuit 1 and a telephone set 2 via a parallel connection circuit 1 comprising a resistor 4 and a capacitor 5 and a combination circuit comprising a diode bridge circuit 7 and the 3rd switch SW3 consisting of a photo transistor(TR) is connected to a speech current supply line L2 between the 1st switch SW1 comprising the photo TR and the telephone set 2. In the case of supplying an incoming signal to the telephone set 2, the 1st switch SW1 is turned off and the 2nd and 3rd switches SW2, SW3 are turned on and off synchronizingly periodically to supply the signal from the incoming signal generating source 3 to the telephone set 2. Thus, production of a surge voltage is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an incoming call signal supply circuit for a telephone, and more particularly to an incoming call signal supply circuit for a telephone when a standalone telephone is connected to a main device.

[Prior Art] A button telephone device is usually configured by connecting a plurality of button telephones or a single telephone to a main device.

A circuit for supplying an incoming call signal to a single telephone will be briefly explained with reference to FIG.

As shown in FIG. 2, the loop detection circuit 1 and the contacts of a relay (not shown), Ill, are connected to the talking current supply line RL1 connected to the positive side of the talking current supply source E, and the talking current Talking current supply line L connected to the negative side of supply source E
An incoming signal generation source 3 is connected between the relay contacts (J and 112), and the telephone current supply line L2 is connected to the telephone set 2.
is connected.

In such a device, the relay contacts j,, 11 are
Outside the incoming call signal supply circuit, a relay is turned off by a control section (not shown) of the main device, so that it is connected to the call current supply line side. When receiving a call signal from the main device, the control section periodically turns on and off the relay to connect its contacts l11. fJ2 periodically from the incoming signal source 31F! By switching between I and the communication current supply line side, an incoming signal is supplied to the telephone I12. When the telephone 1fi2 goes off-hook, the loop detection circuit 1 detects this and sends a signal to the control section. When off-hook, the control section turns off the relay and its contacts, 1
11. j2 to the current supply line side to stop the switching operation, and connect the telephone fi2 to the current supply line L1. Enable connection to L2.

[Problem to be solved by the invention] However, in the conventional button telephone device as described above, the incoming signal to a single telephone is a high voltage, so if this is interrupted by a relay contact, a surge voltage is generated, which causes noise. There was a problem in that it had a negative effect on peripheral circuits.

Therefore, the technical object of the present invention is to provide an incoming signal supply circuit that can prevent noise generation.

1. Means for Solving the Problem] The present invention connects a loop detection circuit to the positive side communication current supply line connected to the communication current supply source, and connects a loop detection circuit to the negative side communication current supply line for forming a communication current path. In a communication current circuit connected to a first switch, the first switch is formed of a phototransistor, one end of a second switch having bidirectional conduction characteristics is connected to the positive side of the communication current supply source, and The other end is connected to one end of a circuit in which a resistor and a capacitor are connected in parallel, and the other end of the circuit in which the resistor and a capacitor are connected in parallel is connected to the positive side communication current supply between the loop detection circuit and the telephone set. one end of the incoming signal generation source is connected to the negative side of the communication current supply source, and the other end is connected to one end of a combination circuit of a diode bridge circuit and a third switch formed of a phototransistor; The other end of the combination circuit is connected to the negative communication current supply line between the first switch and the telephone, and
- The third switch is characterized in that the third switch is turned on and off by the control unit.

[Operation] According to the present invention, except when supplying an incoming call signal to the telephone, the control section turns on the first switch and turns off the second and third switches to connect the telephone to the communication current supply line. enable. When supplying an incoming signal to the telephone, the control section turns off the first switch, turns off the second switch, and so on. The third switch is synchronously turned on and off at a predetermined period to supply the telephone with the signal from the incoming signal source.

[Example] The present invention will be described in detail below with reference to the drawings. 1st
The figure shows one embodiment of the invention. As shown in the figure, 48
A loop detection circuit 1 is connected to the north side communication @flow supply line connected to the communication current supply source E of V, and a phototransistor is connected to the negative side communication current supply line L2 as a first switch SW1. It is connected. Loop detection circuit 1
One end of a parallel circuit of a resistor 4 and a capacitor 5 is connected to the communication current supply line 1-1 between the telephone set 2 and the telephone 2, and the other end of the parallel circuit has opposite polarities. It is connected to one end of a second switch SW2 made up of two 5CRs 6a and 6b connected in parallel. The other end of the second switch SW2 is connected to the positive terminal of the communication current supply source E. One end of the incoming signal generation source 3 is connected to the negative side of the communication current supply source E, and the other end is connected to one end of a combination circuit consisting of a diode bridge circuit 7 and a third switch SW3 made of a phototransistor. There is. The other end of the combination circuit is connected to a communication current supply line L2 between the first switch SWI and the telephone 2. here,
The parallel connection circuit of the resistor 4 and the capacitor 5 is a circuit for preventing the AC component from flowing to the loop detection circuit 1 side when an incoming signal is supplied.

In the circuit described above, the control section (not shown) turns on the first switch SW1 and turns on the second switch SW1 except for the incoming signal supply circuit.
．． Third switch SW2. SW3 is turned off.

On the other hand, when supplying an incoming signal to the telephone a2, the first switch SW1 is turned off and the second switch SW1 is turned off. Third switch SW2. S
W3 is turned on periodically and synchronously.

The signal from the incoming signal generation source 3 is supplied to the telephone set 2 by turning it off. Note that a DC voltage of 148 V from the communication current supply source E is superimposed on the incoming call signal. By the way, the second
The switch SW2 is used to electrically isolate the parallel connection circuit of the resistor 4 and capacitor 5 from the call current supply line during a call. This is because the impedance component of the parallel-connected circuit may affect the impedance of the circuit formed during a call, which may interfere with the call. Furthermore, the reason why the second switch SW2 is composed of two SCRs is to provide a bidirectional conduction function so that the AC signal from the incoming signal generation source 3 can be supplied to the telephone set 2 when an incoming signal is supplied.

Therefore, the switch SW2 only needs to have bidirectional conduction characteristics, and for example, an element such as a triac may be used.

It goes without saying that the present invention is not limited to key telephone devices, but can also be applied to PBXs and the like.

"Effects of the Invention" As described above, the present invention uses a semiconductor element instead of a relay as a means for switching on and off the signal from the incoming signal generation source in the incoming signal supply circuit, so that incoming calls with high voltage Surge voltage does not occur when the signal is intermittent. Furthermore, since a semiconductor element is used, the device can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing a conventional technique. DESCRIPTION OF SYMBOLS 1... Loop detection circuit, 2... Telephone, 3... Incoming signal generation source, 4... Resistor, 5... Capacitor,
6a. 6b...5CR27...Diode bridge circuit. 1 8 -

Claims (1)

[Claims] 1. In a talking current circuit in which a loop detection circuit is connected to the talking current supply line on the positive side connected to the talking current supply source, and a first switch for forming a talking current path is connected to the negative side talking current supply line, A circuit in which the first switch is composed of a phototransistor, one end of a second switch having bidirectional conduction characteristics is connected to the positive side of the communication current supply source, and the other end is connected in parallel with a resistor and a capacitor. The other end of the circuit in which the resistor and the capacitor are connected in parallel is connected to the positive communication current supply line between the loop detection circuit and the telephone set, and the one end of the incoming signal generation source is connected to one end of the circuit. It is connected to the negative side of the communication current supply source, and its other end is connected to one end of a combination circuit of a diode bridge circuit and a third switch made of a phototransistor, and the other end of the combination circuit is connected to the negative side of the first switch. An incoming call signal supply circuit for a telephone set, which is connected to the negative side call current supply line between the switch and the telephone set, and is configured to control on/off of the first to third switches by a control section.