JPH036073Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electronic key telephone device, and more particularly to an extension current supply circuit for a main device.

[Technical background of the invention]

FIG. 1 shows an example of a circuit diagram of an electronic key telephone device equipped with a conventional extension current supply circuit. The electronic button telephone device consists of a main device 1 and a plurality of extension telephones 2 connected to it. The main device 1 includes a plurality of extension call current supply circuits 3,
It consists of an extension communication path 4 and a communication path switching circuit 5. The extension current supply circuit 3 includes a control circuit 31, a transistor (switch element) 32, a filter circuit 33, and a residual charge absorption circuit 34. Filter circuit 33 consists of resistor R ₂ and capacitor C ₁
It is composed of. This filter circuit 33 is
Noise from a DC power supply is prevented from entering an extension telephone line 4, and a voice signal from an extension telephone 2 making an extension telephone call is prevented from leaking to other circuits through the DC power supply. A DC voltage of 24 V from a DC power source (not shown) is applied to the emitter of the transistor 32, and a control voltage from the control circuit 31 is applied to the base via a resistor _R1 . The collector of transistor 32 is connected to resistor R ₂ of filter circuit 33 . Control circuit 3
The control voltage 1 is also applied to the residual charge absorption circuit 34, and this residual charge absorption circuit 34 is connected to the filter circuit 3.
3 is connected to absorb the charge of capacitor _C1 . The output side of the filter circuit 33 is a resistor
It is connected to an extension line 4 via R ₃ and R ₄ , and this extension line 4 is connected to a plurality of extension telephones 2 through a line switching circuit 5 . The communication path switching circuit 5 includes a plurality of self-holding communication path switching switches 5.
1,52. The self-holding communication path changeover switches 51 and 52 are constructed by connecting a parallel circuit of a capacitor and a resistor between the gate and cathode of a photothyristor, and the voltage of this capacitor shortens the turn-on time of the photothyristor.

Next, the operation of this example will be explained. When the extension telephone 2 is connected to the extension telephone line 4 by operating an operation button (not shown) on the extension telephone 2, the control circuit 31 in the extension telephone current supply circuit 3 of the main device 1 is controlled. The voltage becomes low level, and a base current flows through the transistor (PNP type) 32 through the DC power supply emitter, base, resistor R ₁ , and control circuit 31 . Therefore, the transistor 32
turns on, and the emitter and collector become conductive.
Therefore, the direct current passes through the emitter and collector of the transistor 32 and first charges the capacitor _C1 in the filter circuit 33. At the same time as the capacitor C ₁ is charged, the resistor R ₃ , the extension line 4,
Self-holding type communication path changeover switch 51, extension telephone 2, self-holding type communication path changeover switch 52, resistor
A talking current is supplied to the extension telephone 2 through the route _R4 and the earth, and the extension telephone 2 becomes capable of making a telephone call.

At the end of the call, the extension call current supply circuit 3
In order to set the control voltage to a high level, the control circuit 31 in the filter circuit 31 cuts off the base current of the transistor 32, turns off the transistor 32, turns on the residual charge absorption circuit 34, and drains the capacitor in the filter circuit 33. The charge accumulated in C ₁ is instantly discharged through this residual charge absorption circuit 34, and the charge accumulated in the capacitors of the self-holding communication path changeover switches 51 and 52 is also discharged through the residual charge absorption circuit 34, and the extension To quickly disconnect a telephone set 2 from an extension call current supply circuit 3. Therefore, the self-holding type communication path changeover switches 51 and 52 in the communication path switching circuit 5 are turned off, and the extension communication path 4 is placed in an open state.

[Problems with background technology]

By the way, in the conventional extension call current supply circuit 3, since the filter circuit 33 is connected to the collector side of the transistor 32, the transistor 32
Immediately after turning on, a charging current flows to charge the capacitor _C1 , and the capacity of the transistor 32 must be increased by the amount of this charging current, resulting in an increase in cost. Furthermore, since the residual charge absorption circuit 34 was configured to absorb even the charge of the capacitor _C1 , there was a problem in that the communication path could not be quickly disconnected at the end of a call.

[Purpose of invention]

In view of the above-mentioned drawbacks, the present invention reduces the capacity of the switch element that controls the passage or non-passage of direct current to the extension communication path, and supplies extension communication current that enables the communication path to be quickly disconnected at the end of the call. The purpose is to provide circuits.

[Summary of the idea]

The present invention includes a switch element connected between a DC power source and the extension communication path and controlling whether or not to supply the DC current to the extension telephone, in an extension communication current supply circuit that supplies a DC current to an extension communication path. , is connected between the switch element and the DC power supply, and prevents noise contained in the DC power supply from passing through to the extension communication path, and the voice signal sent from the extension telephone loops back. In order to prevent this, the circuit is equipped with an RC filter that conducts the flow to the ground side, charges the capacitor constituting the filter circuit with the DC current, and has a semiconductor switch element and a self-holding communication path changeover switch. A residual charge absorption circuit for absorbing the residual charge of the self-holding type call path changeover switch is connected between the extension telephone line and the semiconductor switch is controlled by the control circuit when a call is started based on the call operation of the extension telephone. On the other hand,
The above object is achieved by turning off the semiconductor switch and causing the residual charge absorption circuit to absorb the residual charge at the end of the call.

[Example of idea]

Hereinafter, one embodiment of the extension current supply circuit of the present invention will be described with reference to the drawings, with the same parts as in the conventional example being denoted by the same reference numerals.

FIG. 2 is a block diagram showing an embodiment of an electronic key telephone device equipped with the extension current supply circuit of the present invention. The electronic button telephone device has a configuration in which a plurality of extension telephones 2 are connected to a main device 1, and the main device 1 further includes a plurality of extension call current supply circuits 3, extension call paths 4, and call path switching circuits 5. It consists of The extension current supply circuit 3 includes a control circuit 31, a transistor (switch element) 32, a filter circuit 33, and a residual charge absorption circuit 34. The filter circuit 33 is composed of a resistor _R2 and a capacitor _C1 . A DC voltage of 24V from a DC power supply (not shown) is applied to a filter circuit 33.
It is applied to the resistor R ₂ of , and is further supplied to the emitter of the transistor 32 via the resistor R ₃ . The collector of the transistor 32 is connected to one end of the extension communication path, and is also connected to the residual charge absorption circuit 34. The other end of the extension line 4 is connected to the ground via a resistor _R4 together with a capacitor _C1 . The control voltage of the control circuit 31 is applied to the base of the transistor 32 via the resistor R ₁ and is also applied to the residual charge absorption circuit 34 . Call path switching circuit 5
is a plurality of self-holding communication path switching switches 51, 5.
It consists of 2.

Next, the operation of this embodiment will be explained. When the extension telephone 2 is connected to the extension communication path 4 by operating an operation button (not shown) on the extension telephone 2, the control voltage of the control circuit 31 becomes low level, and the transistor 32 is connected to the resistor _R1. A base current flows through the transistor 32, and this transistor 32 is turned on. At this time, the capacitor of the filter circuit 33
Since C ₁ is charged with a 24V DC voltage generated from a power supply circuit (not shown), only the current supplied to the extension line 4 flows through the transistor 32 .

By the way, the self-holding communication path switching switch 51 constituting the communication path switching circuit 5 is turned on at the same time as the transistor 32 is turned on, and as described above, a 24V DC current is passed through the resistor R ₂ , the resistor R ₃ , and the transistor 32. DC current is supplied to the extension telephone 2 through the emitter, collector, extension communication path 4, self-holding communication path changeover switch 51, extension telephone 2, self-holding communication path changeover switch 52, resistor _R4 , and earth route. Ru. In this state, the extension telephone 2 becomes available for conversation.

In addition, the self-holding type communication path changeover switch 5
1 and 52 are mounted in a number corresponding to the operation buttons (not shown) of a plurality of extension telephones 2, and only the self-holding call path changeover switches 51 and 52 at the point corresponding to the extension telephone 2 whose button is operated are turned on. The communication current serves as the holding current for these switches 51 and 52.

Next, when another operation button (not shown) is pressed without taking down the handset (not shown) of the extension telephone 2 at the end of the call, the control circuit in the extension call current supply circuit 3 31 changes the control voltage from low level to high level. By this,
The base current of transistor 32 is cut off and it is turned off. At the same time, the residual charge absorption circuit 34
is turned on, and the self-holding communication path changeover switch 5
Absorbs the residual charge of the 1.52 capacitor. As a result, the holding current of the self-holding type changeover switches 51 and 52 in the communication path switching circuit 5 is instantaneously dissipated, these switches 51 and 52 are turned off, and the extension communication path 4 is placed in an open state. That is, in this embodiment as well, the extension telephone 2 is quickly disconnected from the extension telephone current supply circuit 3, and a plurality of extension telephones 2 are unintentionally connected to the same extension telephone current supply path 3, or one It is possible to prevent the extension telephone 2 from being connected to a plurality of extension call current supply paths 3.

According to this embodiment, a filter circuit 33 is inserted before the transistor 32 of the extension current supply circuit 3, and the 24V DC voltage is applied to the transistor 32 through the filter circuit 33, so that the transistor 32 is turned on. At this time, the current flowing through this transistor 32 is only the current supplied to the extension communication line 4, and the current capacity of the transistor 32 can be made smaller compared to the conventional example.
The cost of the extension call current supply circuit 3 can be reduced.

[Effect of idea]

As described above, according to the extension current supply circuit of the present invention, the charging current flows from the DC power supply to the capacitor of the RC filter, but does not flow to the switch element, and the current flowing through the switch element is smaller than that of the conventional switch. The capacitance of the element can be miniaturized and costs can be reduced, and the residual charge absorption circuit only needs to absorb the residual charge of the self-holding communication path changeover switch without absorbing the charge of the capacitor. This has the effect of quickly disconnecting the call during a call.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a circuit example of an electronic key telephone device equipped with a conventional extension call current supply circuit, and Fig. 2 is an example of an electronic key telephone device equipped with an extension call current supply circuit according to the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Main device, 2... Extension telephone, 3... Extension call current supply circuit, 4... Extension call path, 5... Call path switching circuit, 31... Control circuit, 32... Transistor (switch element) , 33...filter circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] In an extension call current supply circuit that supplies direct current from a DC power source to an extension telephone of an electronic key telephone device through an extension call path having a self-holding call path changeover switch, the DC power supply and a semiconductor switch element connected between the extension telephone line and controlling whether or not to apply the DC current to the extension telephone; and a semiconductor switch element connected between the semiconductor switch element and the DC power supply and included in the DC power supply. In addition to preventing noise from passing through to the extension telephone line side, the voice signal sent from the extension telephone is routed to the ground side so that it does not loop back.
an RC filter; a residual charge absorption circuit that is connected between the semiconductor switch element and the extension line and absorbs the residual charge of the self-holding switch; and a call start based on a call operation of the extension telephone. An extension call current supply circuit comprising: a control circuit that turns on the semiconductor switch at times, and turns off the semiconductor switch and causes the residual charge absorption circuit to absorb residual charge when a call ends.