JPS588788B2 - External abnormal voltage detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for detecting an external abnormal voltage for a calling register trunk for detecting a subscriber's call.

As shown in Fig. 1, conventional electronic exchange detects a subscriber's call when a line relay 2 connected to a power supply through a cut-off contact CO detects a loop due to off-hook of a telephone 1 on the subscriber's line. After the line relay 2 is disconnected by the off contact CO, the telephone 1 is connected to the calling register trunk via the network 3.

As a result, the A relay of the receiving circuit 6 detects the loop of the telephone 1 and operates, and the dial tone sending wire 4 operates to send a dial tone (400 Hz) to the telephone.

Upon hearing this, the subscriber performs a dial operation, and in response to the dial pulse, the A relay of the receiving circuit 6 operates to recover, disconnects and connects the contact a of the circuit 7, and sends a pulse corresponding to the dialed number to the control device of the exchange. , electronic exchange control is performed.

In such a configuration, if an external abnormal voltage is applied to the subscriber line, etc., for example, when a commercial power supply is connected to the subscriber line due to an accident, the continuous abnormal voltage may cause the line to be disconnected even though the telephone has not formed a loop. Relay 2 operates, giving the same effect as telephone 1 making a call through the loop.

As mentioned above, when a call is made, the exchange connects to the originating register trunk, but if a call is made due to abnormal voltage, there is a risk of destroying the originating register circuit such as the receiving circuit.

Therefore, it is necessary to actively detect this abnormality and disconnect the subscriber line.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting an external abnormal voltage to a calling register trunk for detecting a subscriber's call.

In order to achieve the above object, the external abnormal voltage detection method of the present invention includes a circuit for detecting external continuous abnormal voltage in the calling register trunk that detects the calling of the subscriber's line in an electronic exchange. The present invention is characterized in that when a call is detected, the abnormal voltage is identified by connecting to the abnormal voltage detection circuit before connecting to the calling register circuit in the trunk.

The present invention will be described in detail below with reference to examples.

FIG. 2 is an explanatory diagram showing the configuration of an embodiment of the present invention.

The difference between this figure and Figure 1 is that an abnormal voltage detection circuit 20 is provided in front of the transmitting register circuit of the transmitting register trunk, which is surrounded by a broken line, and in connection with this, a control circuit 21 that is connected to the control device of the exchange is provided. That's what happened.

The abnormal voltage detection circuit 20 is branched by a contact S so as to be normally connected to the input line of the transmitting register trunk, and is connected to a diode 13 and a resistor R.

12 to the check CH relay 11 whose other end is grounded.

On the other hand, the control circuit 21 includes a contact circuit 14 and an S relay 15, which are respectively connected to the control device.

The circuit 14 has a contact a operated by the A relay of the receiving circuit 6 and a contact c operated by the CH relay 11 of the abnormal voltage circuit 20.
h are connected in parallel.

The S relay 15 operates to close the contact S after a certain period of time has elapsed without the CH relay 11 operating after the line relay LR2 has operated.

In the above configuration, for example, when abnormal AC voltage 10 is applied to the subscriber line from the outside, line relay LR2 is operated by this voltage.

Before the exchange is connected to a transmitting register circuit such as a receiving circuit, it is led to an abnormal voltage detection circuit 21 through an inoperable contact S to operate a CH relay 11.

As a result, the contact channel of the circuit 14 is turned on, informing the control device of the occurrence of the abnormal voltage, the control device issues an alarm, and disconnects the subscriber line from the exchange.

If the call is from a subscriber and the CH relay 11 does not operate, the S relay 15 operates after a certain period of time has passed after the operation of the L R relay 2, and the contact S of the input line of the calling register trunk
is turned on to connect the telephone 1 to a transmitting register circuit such as the receiving circuit 6, and the normal operation described in FIG. 1 is performed.

As explained above, according to the present invention, an abnormal voltage detection circuit is provided in the originating register trunk, and the abnormal voltage is detected and the subscriber line is disconnected from the exchange before being connected to the originating register circuit. This is useful for early detection of accidents and limiting the damage caused by accidents.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a conventional example, and FIG. 2 is an explanatory diagram showing the configuration of an embodiment of the present invention. In the figure, 1 is a telephone;
2 is a line relay, 3 is a network, 4 is a dial tone transmission wire, 6 is a receiving circuit, 11 is a check relay, 12 is a resistor, 13 is a diode, 14 is a contact circuit, 1
5 is an S relay, 20 is an abnormal voltage detection circuit, and 21 is a control circuit.

Claims (1)

[Claims] 1. A calling register trunk that detects calls on a subscriber's line in an electronic exchange is equipped with a circuit for detecting continuous abnormal voltage from an external source, and connects to the calling register circuit in the trunk when a calling on a subscriber's line is detected. An external abnormal voltage detection method, characterized in that an abnormal voltage is identified by connecting the abnormal voltage detection circuit to the abnormal voltage detection circuit.