JPH10290290A - Telephone line interruption detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the telephone line interruption detector by which whether or not a line interruption takes place is detected on the occurrence of a lockout alarm. SOLUTION: When a line interruption or a telephone handset off-hook continues for a prescribed time, an exchange 2 detects an alarm automatically to disconnect a line (a). Upon the receipt of the alarm by a telephone line interruption detector 1, a line automatic loop forming section 1-2 throws a line (b) to a position of a line (c) to terminate a line 3 thereby forming a line loop with the line 3 and a telephone set 4. The telephone line interruption detector 1 uses an alarm (ALM) detection transmission section 1-1 to send a DC voltage to the telephone set 4 and a PB signal to detect an alarming position. When an ALM detection measurement section 1-3 detects a prescribed level of the PB signal or over via the telephone set 4, it is discriminated that no line fault exists and when the section 1-3 detects a prescribed level or below, it is discriminated that a line fault exists and an alarm is outputted to a host line interruption detector or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a telephone line disconnection detecting device, and more particularly to a telephone line disconnection detecting device used in a small telephone exchange.

[0002]

2. Description of the Related Art Very large telephone exchanges used in a public telephone network are provided with extremely complicated functions. However, in a small telephone exchange (PBX),
For example, there are telephones A, B, and C. The telephones A and B, or the telephones B and C are connected via a two-wire (2W) type circuit, and have very basic functions. do not have.

In the above-mentioned small telephone exchange, if telephones A and B are connected to each other and, for example, the line connection to telephone B is lost from the viewpoint of the telephone exchange, after a certain period of time elapses, the lock is established. Out alarm is output. Note that "lockout" refers to disconnecting a subscriber or an incoming line in an invalid hold state by a common device in order to prevent the common device from being invalidated and held due to a handset being taken off for a certain period of time or longer.

However, for example, when the line connection to the telephone B is lost, the following two cases: a) The call is completed and the telephone B is hooked up, but the telephone A is not hooked up. B Line disconnection (line failure) has occurred on the line to telephone A while a call is in progress;

[0005]

In the case of a conventional small telephone exchange, even if a lockout alarm is output, it is not possible to identify which of the above cases.

An object of the present invention is to provide a telephone line disconnection detecting device capable of detecting whether a line disconnection has occurred when a lockout alarm has occurred.

[0007]

A telephone line disconnection detecting device according to the present invention issues an alarm and disconnects the telephone line when a lockout alarm occurs on a telephone line connected to a telephone via a line. A telephone line disconnection detecting device added to the telephone exchange including the means, a detection loop forming means for forming a detection loop by terminating the disconnected telephone line in response to the alarm, and Test signal transmitting means for transmitting a test signal to one of the wires, test signal receiving means for receiving the transmitted test signal from the other wire of the disconnected telephone line, and reception of the test signal receiving means And line disconnection detecting means for detecting a line disconnection when the test signal level is below a certain value.

The operation of the present invention is as follows. When a lockout alarm occurs, disconnect the line on which the lockout alarm occurred from the telephone exchange, insert a telephone line disconnection detection device to form a unique loop, and send out a PB signal (a test signal including a multi-frequency signal). By detecting the returned PB signal, the line disconnection is detected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a telephone line disconnection detecting apparatus according to the present invention. In FIG. 1, a telephone line disconnection detecting device-related system according to the present invention is a representative of a telephone line disconnection detecting device 1, a small telephone exchange 2 for connecting a relatively small number of telephone lines, and a telephone line connected to the telephone exchange 2. (The other telephone lines and telephones are not shown).

The telephone exchange 2 has a line circuit 2-1 connected to the (2W type) line 3, and a telephone line disconnection detecting device 1 when a lockout alarm occurs on the line (line 3 / telephone 4). Alarm (alarm; ALM) part 2
-2. The telephone line disconnection detecting device 1 sends an PLM signal to one of the two wires of the line 3 by an ALM detection transmitting unit 1-1. When a lockout alarm occurs, the line 3 is disconnected from the telephone exchange 2. The ALM connected to the wire of the line 3 is the opposite of the line automatic loop forming unit 1-2 and the ALM detection transmitting unit 1-1 that are terminated.
It comprises a detection and measurement unit 1-3.

The operation of the embodiment of the present invention is as follows. When the line disconnection or the telephone receiver off-hook state continues for a certain period of time, the exchange 2 automatically detects an alarm (lockout alarm) and gives an alarm to the telephone line disconnection detecting device 1. Notify via the unit 2-2 and disconnect the line a. When the telephone line disconnection detecting device 1 receives an alarm, the line automatic loop forming section 1-2 switches the line b to the line c and changes the line 3 to a resistor r having a characteristic impedance of, for example, 600Ω.
1 and a telephone set via line 3 (internal impedance r2 as viewed from line 3 is, for example, 600Ω)
4, a line (detection) loop is formed.

In a state where the loop is formed, the telephone line disconnection detecting device 1 sends a DC voltage (power supply) to be supplied to the telephone 4 and a PB signal for detecting an alarm point from the ALM detection transmitting section 1-1. Send out. If the PB signal can be detected by the ALM detection / measurement unit 1-3 via the telephone 4 at a certain level or higher, it is determined that there is no line abnormality, and the line automatic loop forming unit 1-2 switches the line c to the line b, Route 3 is reconnected to telephone exchange 2. If the PB signal can be detected by the ALM detection / measurement unit 1-3 only at a certain level or less, it is determined that the line has been disconnected, and an alarm is output to a higher-level line disconnection detecting device or the like.

[0014]

As described above, according to the present invention, when the telephone exchange detects a lockout alarm, a detection loop is formed to detect whether a line disconnection has occurred or whether the telephone is simply in an off-hook state. There is an effect that can be done.
Further, since the telephone line disconnection detecting device according to the present invention can be externally attached as an additional device of the telephone exchange, there is also an effect that the telephone exchange does not need to be modified.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Telephone line disconnection detection apparatus 1-1 ALM detection transmission part 1-2 Automatic line loop formation part 1-3 ALM detection measurement part 2 Telephone exchange 2-1 Line circuit 2-2 Alarm part Three times line 4 Telephone

Claims (3)

[Claims] 1. A telephone line disconnection detecting device added to a telephone exchange including means for issuing an alarm and disconnecting the telephone line when a lockout alarm is generated in a telephone line connected to a telephone via a line path. Detecting means for forming a detection loop by terminating the disconnected telephone line in response to the alarm, and transmitting a test signal to one of the disconnected telephone lines. Means, test signal receiving means for receiving the transmitted test signal from the other wire of the disconnected telephone line, and when the test signal level received by the test signal receiving means is below a certain value And a line disconnection detecting means for detecting a line disconnection. 2. The telephone line disconnection detecting device according to claim 1, wherein said test signal is a PB signal. 3. The telephone line disconnection detecting device according to claim 1, wherein when the line disconnection detecting means detects a line disconnection, an alarm is issued to an upper line disconnection detecting device.