GB2192998A

GB2192998A - Telephone line tester

Info

Publication number: GB2192998A
Application number: GB08715108A
Authority: GB
Inventors: Peter Starkie Isherwood
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-07-21
Filing date: 1987-06-26
Publication date: 1988-01-27
Also published as: GB8715108D0; GB8617805D0

Abstract

A telephone line tester comprises a plug (4) for connection to a telephone socket a zener diode (5) and LED (15) which indicates when the voltage in the line is at the required level and in the required direction; an LED (20) which indicates when the line voltage is of reverse polarity; and a switch (16) and LED (19) which indicates when a dial signal is available. <IMAGE>

Description

SPECIFICATION Circuit tester This invention relates to an electrical circuit tester and more particularly to a telephone line tester which is small enough to be carried in the pocket of a garment.

Hitherto conventional methods of testing a telephone line have involved an engineer visiting the premises of the user of the telephone and carrying out tests in conjunction with the telephone exchange. The need for personnel in separate locations to co-operate in the testing of a line can be inconvenient.

Accordingly there has been a growing need for some means of testing which enables an engineer or the user to carry out the appropriate tests without reference to the telephone exchange. Accordingly this invention is directed to a telephone socket line tester which can be small enough to be carried in the pocket of a garment and which gives a visual indication that the telephone line from the exchange is connected for the correct polarity and or the correct voltage and that the dialling tone is also available.

Accordingly this invention provides a telephone socket line tester comprising connecting means for connecting the tester to a telephone line a polarity tester circuit incorporating a first detection device which indicates when the polarity and or the correct voltage of the voltage in the circuit is incorrect and a second tester circuit connected in parallel to the first tester circuit incorporating a detection device which indicates when the voltage in the second tester circuit falls below a predetermined level. The line tester incorporates preferably a third tester circuit incorporating a detector which indicates when a dial signal is available the third circuit being connected in parallel with the first and second circuits.

This invention is illustrated but not restricted by the following drawings which shows a preferred form of a telephone line tester constructed according to the present invention and which is adapted to be carried in the pocket of an operative.

Figure 1 is a view taken in plan showing the tester.

Figure 2 is a side elevation of the tester shown in Fig. 1.

Figure 3 shows schematically the wiring circuits employed in the tester shown in Figs. 1 and 2.

In these figures the same numerals represent the same features. In Figs. 1 and 2 a case (1) made conveniently of a synthetic plastic material has approximate measurements of 100x 15 x 10 mm although the size of the case is not critical since it can have any convenient dimensions. The case is provided with a pocket clip (2) and a cover (3) for a plug (4) which is used conveniently for a PBX telephone socket. This is a form of socket which is used widely and through it a user's telephone is connected by a line to a telephone exchange. However by simple adaption the' present tester can be used for other forms of telephone sockets. The casing is also provided with apertures for accommodating three light emitting diodes forming part of the circuit enclosed by the casing.These diodes comprise a low current diode (5), a standard diode for the standard dial voltage (6) and a second low current diode (7) and a push-button switch (8).

Fig. 3 shows schematically the arrangement of three tester circuits namely a first low current circuit (9), a standard current circuit (10) and a polarity testing circuit (11). All three circuits are connected in parallel.

The low current circuit (9) comprises plug (4) for the PBX socket, a 45 v zenner diode (5) for giving a small voltage through a b watt 390 R, 5% limiting resistor (13) and a light emitting diode (14) of 5M/A which emits a red light when the voltage in the circuit. rises above a predetermined level.

The STD circuit (10) comprises a push-button switch (16), a 4 watt 680 R 5% limiting resistor (17), 2.2 mfd 50v capacitor (1-8) and a light emitting diode (19) which when activated emits a green light. This circuit is also connected to plug (4).

The polarity circuit comprises a low current light emitting diode (20) which emits a red light if the polarity in the circuit is reversed and a 15 Kr 5% 4 watt limiting resistor {21).

The construction of the tester is now clarified by way of its operation.

The tester is powered by the voltage employed in the telephone line namely 50v. The cap is removed from the tester to expose plug (4) which is inserted into a PBX socket.

If the voltage is above 45 volts and is of the correct polarity the zener diode (12) passes current through limiting resistor (13) and causes the low current light emitting diode (15) to give a red light. On the other hand if the current is below 45 volts diode (15) will not light. If the polarity is incorrect because, for example the connections to a plug socket have been reversed the current through resistor (21) will be limited to a 5m/a and as a result the light emitting diode (20) will give a red warning light.

When switch (16) in the standard current tester circuit (10) is pressed the current in the telephone line increases to 14 M/a passing through limiting resistor (17) and capacitor (18). This has the effect equivalent to a user lifting a receiver from a telephone and the telephone giving a dial tone. When the switch has been pressed capacitor (18) charges up and causes light emitting diode (19) to give a green light. At the same time diode (15) is extinguished, thus indicating that a dialling tone is available.

The tester can be assembled in different ways. For example all the components can be mounted on a board provided with an appropriate printed circuit. The switch (16) together with its spring can be constructed conveniently on the board. The case can be made in two halves from a synthetic plastics material on which can be printed in contrasting colour information concerning the use of the tester.

Whilst this invention is directed primarily to a tester small enough to be carried in the pocket of a garment testers having different dimensions and utilising different forms of signalling devices are envisaged within the scope of the present invention.

Claims

1. A telephone socket tester comprising connecting means for connecting the tester to a telephone line, a polarity tester circuit incorporating a first detection device which indicates when the polarity is in a required direction in the circuit and/or the voltage is at a required level and a second detector circuit connected in parallel to the first detector circuit incorporating a second detection device which indicates when the voltage in the second tester circuit falls below a predetermined level.

2. A telephone socket line tester according to Claim 1 incorporating a third detector circuit incorporating a third detector which indicates when a dial signal is available the third circuit being connected in parallel with the first and second circuits.

3. A telephone socket tester claimed in either of Claims 1 or 2 wherein the connecting means is a plug for a PBX telephone socket.

4. A telephone socket tester according to any one of the preceding claims wherein each of the detection devices is a light emitting diode.

5. A telephone socket tester according to any one of the previous claims when powered by the voltage employed in a telephone line.

6. A telephone socket tester according to Claim 5 when the voltage is 50v.

7. A telephone socket tester incorporating an STD circuit operated by a switch.

8. Telephone socket testers as claimed in any one of the preceding claims.

9. Telephone socket testers as hereinbefore described with particular reference to the drawings.