GB2319432A

GB2319432A - Analogue telephone socket tester

Info

Publication number: GB2319432A
Application number: GB9623777A
Authority: GB
Inventors: Stephen Roberts
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-11-15
Filing date: 1996-11-15
Publication date: 1998-05-20
Also published as: GB9623777D0

Abstract

An improved design of telephone socket tester which enables the integrity of the electrical connection of the shunt wire (bell wire) to be established without the need to initiate an incoming ringing signal. The design detects the presence of the dialling tone by monitoring the telephone line through the capacitor 6 mounted in the Master Socket and the associated wiring of parallel connections to secondary sockets.

Description

ANALOGUE TELEPHONE SOCKET TESTER This invention relates to an analogue telephone socket tester.

Current wiring practice requires that exchange lines, and extensions from privately-owned exchanges, are terminated with Master Sockets. The two wires of the incoming line, known as the 'a' and 'b' wires, are connected to the appropriate terminals of the Master Socket, and a third connection, the 'shunt' wire, or 'bell' wire, is formed by inserting a series-connected capacitor as shown in Figure 1. Any subsequent extension sockets require all three connections to be made in parallel with the appropriate connections of the Master Socket. A wire from this third connection carries the ac ringing voltage to all subsequent socket outlets. If it is not connected to a particular socket, a telephone connected to that socket will not ring on an incoming call, but will function in other respects.

Simple socket testers are available but these only test for the correct connection of the 'a' and 'b' wires. With such testers, in order to test for the correct connection of the 'shunt' wire, it is necessary to plug in instead a device capable of indicating a ringing signal (such as a telephone) and then arrange for a ringing signal to be applied to the line. This method of testing is time-consuming, not always convenient, and requires a telephone or other device in addition to the socket tester.

According to the present invention, there is provided a means of testing for the presence and correct connection, by means of the shunt wire, of the capacitor incorporated in the Master Socket by taking advantage of the fact that electrical audio-frequency signals present on the line will be transmitted through the capacitor.

Such signals include the 'dialling tone' (ie. that tone generated at the exchange which is present and audible when the handset of an ordinary telephone is lifted to the 'off-hook' position, but before any form of dialling has taken place). By arranging within the tester a simulation of the 'off-hook' condition, the presence of the tone monitored at the shunt wire provides a positive indication that the connection is intact.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing (Figure 2) which shows the circuit diagram of the relevant part of a socket tester.

Referring to Figure 2, the socket tester comprises, in addition to a line voltage level and polarity detection and indication circuit 1, a load resistor 2, a switch 3, a loudspeaker 4, an over-voltage protection circuit 5 and a flying lead terminated in a plug suitable for connecting to a telephone socket. Capacitor 6 is an integral part of the Master Socket.

In order to test for the correct connection of the shunt wire, the flying lead is plugged into the socket to be tested, and switch 3 is closed, thus allowing line current from the exchange to flow through resistor 2. The exchange responds by connecting to the line an audible tone source which is routed to the loudspeaker 4 via the capacitor 6. The absence of the tone indicates a fault condition.

The over-voltage protection circuit 5 is provided to protect the loudspeaker should a ringing voltage be applied to the line while the tester is connected.

As an alternative arrangement to this example, the loudspeaker 4 could be replaced with any other form of tone detector, such as an electronic circuit with a visual output.

Claims

1. A means of testing the integrity of the shunt wire electrical connection at any telephone socket connected to an analogue telephone exchange by detecting the presence of a tone applied to the telephone line and routed to a detection device by means of the capacitor incorporated within the Master Socket.

2. A means of testing the integrity of the shunt wire electrical connection at any telephone socket connected to an analogue telephone exchange as claimed in Claim 1, wherein the detection device is an audio transducer.

3. A means of testing the integrity of the shunt wire electrical connection at any telephone socket connected to an analogue telephone exchange as claimed in Claim 1, wherein the detection device provides an audible output.

4. A means of testing the integrity of the shunt wire electrical connection at any telephone socket connected to an analogue telephone exchange as claimed in Claim 1, wherein the detection device provides a visual output.