JPS6143052A - Subscriber circuit - Google Patents

Abstract

PURPOSE:To decrease the number of large capacity resistors by using a protection resistor in common use with the transmission resistor of a ringer signal in an electronic exchange so as to use the resistor switchingly by a changeover circuit. CONSTITUTION:In transmitting a call signal, a relay RL is operated by a control signal from the exchange and the call signal flows to a subscriber telephone set TEL through resistors R4, R6' by contacts rl1-rl3. When the subscriber responds to the signal, a current of a -48V power supply flows superimposingly and when a DC voltage of the resistor R6' reaches a reference value or over, the relay RL is restored and the subscriber telephone set TEL is connected to a codec CODEC. In the talking state, if the subscriber lines are short-circuited, the current flows in the path of -48V power - resistors R6, Rb', R3- earth, and when the line A of the subscriber lines is grounded, the current flows in the path of -48V power - resistors R6, Rb'- earth and when the line B is grounded, the current flows in the path of -48V power - resistors R6, R6'- subscriber telephone set TEL - earth, then no current supply circuit is damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] □ ′ The present invention relates to an improvement in the subscriber circuit of an electronic exchange.゛.

The subscriber circuit referred to here is installed at the subscriber terminal in a digital electronic exchange, and supplies DC current to the subscriber telephone, has a function of sending a ringing signal, a function of detecting a subscriber's response when sending a ringing signal, and a loop function. It has current monitoring, 2W-4W conversion function, A/'D conversion function, D/A conversion function, etc.

[Prior Art] - "Figure 2 is a diagram showing an example of a conventional subscriber circuit. In the figure, R1 and R12 are resistors, C1 and C2 are capacitors, and Ql and Q2 are capacitors, respectively. transistor, OPI,
OF2 is an operating amplifier, HYB is a hybrid, C0DEC is a codec, RT is a ring trip circuit, CR is a calling signal source, rll, r12, and r13 are contacts of a relay RL (not shown), and the location is a subscriber. The telephone and NW are networks. In addition, the same symbol represents the same object throughout all the figures below.

When sending a ringing signal to a subscriber's telephone, relay RL is operated by a control signal from the exchange main body, and its contact r11
, r12, r13, the ringing signal flows through resistor R'1 and resistor R2 to the subscriber's telephone equipment. When the call bell rings and the subscriber answers and goes off-hook, a superimposed DC current flows from the -48V power supply, and therefore, when the DC voltage at resistor R2 exceeds the reference value, the ring trip circuit RT is activated. It is determined that the subscriber has gone off-hook, and a ring trisop signal is sent to the exchange main unit, and as a result, relay RL is restored, and the subscriber's telephone equipment becomes hybrid HYB.
It is connected to the codec GODB,C via.

The part surrounded by dotted lines in Figure 2 is the so-called communication current supply circuit, and as is well known, when the communication state is established, the relay R
This is a circuit for supplying communication current to the subscriber's telephone device via the L contacts rll and rl2.

In addition, resistors R3 and R4 are protective resistors for bypassing large currents in the event of a short circuit or ground fault when the subscriber line has low resistance, and the current capacity of resistor R4 is higher at the higher voltage point. Naturally, a large one is used because it is used in

On the other hand, since the ringer voltage is 70 to 90V, the ringer sending resistor R2 also requires a resistor with a relatively large current capacity (about 3W).

This configuration is detailed in JP-A-57-25766-Electronic Power Supply Circuit.

[Problems to be Solved by the Invention] As is clear from the above description, the resistors R2 to R4 shown in FIG. 2 are components having a large current capacity due to their electrical characteristics.

This is not a desirable situation, as electronic exchanges are now becoming integrated circuits, which require the use of special parts for mounting.

It is an object of the present invention to provide a circuit that can be constructed without using large-capacity resistors as much as possible.

[Means for solving problems]

A means to solve the problem is to provide a switching circuit operated by a ringer sending control signal to the subscriber line via a resistor in the subscriber circuit of the electronic exchange, and the resistor is connected to the protective resistor of the power supply circuit. This is achieved by a subscriber circuit commonly used for the ringer sending resistor.

[Effect]

゛According to the present invention, focusing on the fact that the time when the current supply circuit is supplying the talking current and the time when it is sending out the ringer signal do not overlap in time, the high voltage side of the current supply circuit is The large-capacity protective resistor inserted between the collector and emitter of the circuit's power supply transistor is also used as the ringer signal transmission resistor, and can be switched using a switching circuit, eliminating the need for a large-capacity resistor that is undesirable in terms of implementation. This has the great effect of reducing the number of times used.

〔Example〕

FIG. 1 is a diagram showing one embodiment of a subscriber circuit according to the present invention.

In the figure, Ra%Rh is the resistance according to the present invention.

The invention will now be described in detail with reference to the figures.

The resistors Ra and Rh are large capacity resistors.

The present invention is an improvement that focuses on the point that the ringer signal transmission time and the current supply circuit operation time do not coexist.

When this circuit sends a calling signal, the relay RL is operated by a control signal from the exchange main body, as in the case of Fig. 2, and its contacts rlLr12 and rl3 cause the calling signal to pass through the resistor Ra and the resistor Rh. flow to the subscriber's telephone equipment.

　　　　　　.

When the ringing bell rings and the subscriber answers and goes off-hook, a current of -48V flows in a superimposed manner.As a result, when the DC voltage across the resistor RM exceeds the reference value, the ring trip circuit RT indicates that the subscriber goes off-hook. It is determined that a non-button trip signal is sent to the exchange main body, and as a result, relay RL is restored and the subscriber telephone device is switched to hybrid HY.
It is connected to the codec C0DEC via B. The first
Contacts rl 1 , rl 2, r of relay RL in the figure
The state l3 indicates the position in the recovery state.

If the subscriber line is short-circuited during this call, -48
A current flows from the v power supply to the resistor R6 to the resistor Rb to the resistor Ra to the ground, and does not damage the current supply circuit (the part surrounded by the dotted line).

Also, when the A line side of the subscriber line is grounded, the 48V power supply ~
Current flows between resistor R6 - resistor Rb - ground, and even when the B line side of the subscriber line is grounded, current flows between - 48V power supply - resistor R6 - resistor Rb - subscriber telephone equipment - ground, so the current supply circuit is connected to both. will not be damaged,
.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to reduce the number of large-capacity resistors used, which has a great effect on the mounting of equipment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of a subscriber circuit according to the present invention. FIG. 2 is a diagram showing an example of a conventional subscriber circuit. In the figure, R1-R12 are resistors, C1 and C2 are capacitors, Ql and C2 are transistors, OPI and OF
2 is an operation amplifier, HYB is a hybrid, CODEC is a coaching, RT is a ring trip circuit, CR is a calling signal source, rll, r12, and r13 are contacts of a relay RL, respectively, LOC is a subscriber telephone, NW is a network, Ra. Rb is a resistor according to the invention.

Claims (1)

[Claims] In the subscriber circuit of an electronic exchange, a switching circuit operated by a ringer sending control signal is provided to the subscriber line via a resistor, and the resistor is commonly used as a protection resistor of the power supply circuit and a ringer sending resistor. A subscriber circuit characterized by: