JPH03295340A - Office line interface circuit - Google Patents

Abstract

PURPOSE:To attain the reduction of cost and the simplification of control by using a relay to isolate a battery detection circuit and connect a loop close circuit and a speaking circuit at the time of starting a call for keeping the speaking circuit isolated during dialing and during standby. CONSTITUTION:During the standby, the loop close circuit 2 is kept in an opened state, and in addition, the speaking circuit 1 is kept isolated from an office line by the relay contact 3, and a circuit equivalent to a state that only a call detection circuit 1 and the battery detection circuit 7 are connected is constructed from on office line side, and the dialing is sent by interrupting the loop close circuit 2, and during sending the dialing, the speaking circuit 4 is kept isolated by operating the relay. Besides, the degree of balance of installation during the call is kept by isolating the battery detection circuit 7 by the contact 9 of the other side of the relay. Thus, a means to isolate the battery detection circuit 7 during the call and the means to isolate the speaking circuit 4 during dialing is realized by one piece of the relay by using it in common.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a PBX exchange, and particularly to a call detection circuit.

The present invention relates to a central office line interface circuit suitable for economically constructing a battery detection circuit, a loop closing circuit, and a communication circuit.

[Conventional technology]

In the conventional device, as described in Japanese Patent Application No. 59-226637, only the call detection circuit and the battery detection circuit are connected between the A and B lines on the central office line side during standby, and the loop closing circuit and the communication circuit are connected. A separate circuit was provided to disconnect the relay contacts and the dial A communication circuit.

In conventional circuits, when a call is received, after the called party responds, the relay is operated to connect the loop closing circuit and the talking circuit to the central office line, and when making an outgoing call, the relay is also operated and the loop closing circuit and the talking circuit are connected to the central office line. A system was adopted in which a circuit was connected to form a call state, and a separate circuit was provided to disconnect the call circuit during dialing.

[Problem to be solved by the invention]

In the conventional circuit described above, only the call detection circuit and battery detection circuit are connected to the A and B lines on the central office side during standby, and a relay and relay driver are used to separate the loop closing circuit and the talking circuit. A circuit for disconnecting the impedance communication circuit and a control circuit or control program for the circuit are required, which is uneconomical. SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned uneconomical problem by using a single relay that serves both as a means for disconnecting the battery detection circuit during a call and as a means for disconnecting a call circuit during a dialing.

[Means to solve the problem]

In order to achieve the above purpose, the loop closing circuit during standby is kept in an oven state, and the communication circuit is separated from the office line by a relay contact, so that only the call detection circuit and battery detection circuit are connected from the office line side. We created a circuit equivalent to the one used in the system, and the loop closing circuit is used intermittently for dialing, and during dialing, the relay is activated to disconnect the communication circuit, thereby preventing dial distortion. It is something. When the communication circuit is disconnected, the battery detection circuit
The other contact of the relay is connected to the B line, but by configuring the circuit with a high impedance circuit, it is possible to prevent it from affecting the transmission characteristics of the dial.

[Effect]

In the standby state, the call circuit is disconnected by one contact of the relay provided to disconnect the call circuit during dialing, and the loop closing circuit is left open, so that the battery is not transmitted to the central office. A state equivalent to when only the detection circuit and the call detection circuit are connected can be created.

During a call, the battery detection circuit is disconnected from the other contact of the relay to maintain balance during the call, thereby preventing common mode induced voltage from turning into normal mode noise and interfering with the call. .

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1, 2, and 3.

FIG. 1 is a circuit diagram of an embodiment of a station line interface circuit according to the present invention. In Figure 1, 1 is a call detection circuit that detects a call signal (AC) that allows direct current to pass through, 2 is a loop closing circuit that opens and closes a DC loop with high impedance for voice signals, and 3 and 9 are central office line interfaces. Relay contacts C1, C2 and 4 are controlled by a circuit control unit (not shown); 4 is a communication circuit consisting of a 2-wire, 4-wire converter C0DEC, etc.; 5 is a communication transformer that passes communication signals;
6 is a DC cut capacitor, and 7 is a battery detection circuit. FIG. 2 is a diagram of the operation of the circuit in the case of an incoming connection, and FIG. 3 is a diagram of the operation of the circuit in the case of an outgoing connection. The operation of this circuit will be explained below. When the central office line interface circuit shown in FIG. 1 is in a standby state, the communication circuit 4 is in a disconnected state by relay contacts C, 3 (l old state) in this circuit.

The operation in the case of an incoming connection will be explained with reference to FIGS. 1 and 2. A ringing signal that intermittents at regular intervals as shown in Fig. 2 (1) is sent from the station line, but since a negative DC voltage appears on the B line during the xylent section, it is connected to the B line by relay contact C29. The battery detection circuit 7 detects the battery and connects it to the central processing unit W (hereinafter referred to as CP) through the control circuit 8.
An event indicating the arrival of a B-line battery is sent to the B-line battery.

Next, in the ringing signal section, an AC signal of 20H2 is applied between the A and B lines, so the ringing detection circuit 1 detects this, and the C
An event indicating that a call signal has arrived at P is sent.

This allows the CP to call the called party and monitor its response.
When the called party answers, the CP sends information indicating that the called party has answered to the control circuit 8 of the office line interface circuit, and the control circuit 8 of the office line interface circuit drives the loop closing circuit 2 to close the loop at the office side. Closes a DC loop against. The station circuit detects the current Kt flowing due to the loop closure, stops the ringing signal, and transitions to a talking state. The control circuit 8 of the office line interface circuit connects the telephone circuit 4 and the office line via the DC cut capacitor 6 and the telephone transformer 5 by operating the relay contacts C and 3 at the timing until the ringing signal stops, thereby making a telephone call. form a circuit. At the same time, the battery detection circuit becomes disconnected from the B line by relay contact C79.

Next, the operation in the case of an outgoing connection will be explained with reference to FIGS. 1 and 3. When the calling party issues a connection request to the central office line from a telephone or the like, the CP sends a command to request the central office line activation to the control circuit 8 of the central office line interface circuit. In response to this command, the control circuit 8 of the office line interface circuit drives the loop closing circuit 2 to close a DC loop to the office side. Relay contacts C and 3 are operated almost at the same time as the station is started, allowing dial tones from the station to pass through. At this time, the battery detection circuit is disconnected from the B line by relay contact C9. When the station circuit learns that it has been activated by the loop current, it prepares to receive a dial and waits for the arrival of the dial. When the caller dials, the CP sends dial information to the control circuit 8 of the central office line interface circuit, so the control circuit 8 controls the loop closing circuit 2 based on the dial information to disconnect or disconnect the DC loop. conduct. While the dial is being sent out, the relay contact C□3 is restored as shown in FIG. 3 (1) to disconnect the communication circuit so that it is completely open to the station only during the dial break. When each digit has been dialed, the relay contact C13 is operated to make the central office line interface circuit completely ready for communication.

〔Effect of the invention〕

According to the present invention, the conventional station line interface circuit
Only the battery detection circuit and the call detection circuit were connected to the central office line during each period, and a relay was installed that disconnected the battery detection circuit and connected the loop closing circuit and the call circuit when entering the common line when making and receiving calls. On the other hand, by using the relay as a circuit used to disconnect the call circuit during dialing and during each period, the circuit and its control circuit can be eliminated, reducing costs and simplifying control. This makes it possible to realize high-density packaging of central office line interface circuits.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the circuit configuration of a central office line interface circuit according to an embodiment of the present invention, Fig. 2 is an operation diagram showing the circuit operation in the case of an incoming connection, and Fig. 3 is a circuit diagram showing the circuit operation in the case of an outgoing connection. FIG. 1...Call detection circuit 2...Loop closing circuit 3.
... Relay contact 1 4 ... Call circuit 5 ... Call transformer 6 ... DC cut capacitor 7 ... Battery detection circuit 8 ... Control circuit 9 ... Relay contact 2

Claims (1)

[Claims] 1. A call detection circuit and a loop closing circuit are connected between the A and B lines of a pair of office lines, and a communication circuit is transformer-coupled via a DC cut capacitor, and the communication circuit is disconnected during standby. A station line interface circuit characterized by having a relay contact that is released.