GB2112532A - Device for testing jack plugs and jack plug leads - Google Patents

Abstract

A device for testing jack plug leads having a respective jack plug connected to opposite ends thereof, comprises two jack plug sockets adapted to receive the jack plugs, a source of emf (10), connections serving to connect the source of emf between two normally open contacts (14, 16) of one of the sockets, and a low current light source such as a light-emitting diode (20) connected between normally open contacts (22, 24) of the other socket such that when jack plugs at opposite ends of a lead are inserted into the two sockets the light source will only illuminate if no fault exists in the jack plug lead. A more complex version, which provides for a battery test without need for an additional switch which also permits fault diagnosis, incorporates two stereo jack plug sockets each having three pairs of normally closed contacts appropriately connected to a source of emf and a low current light source such as a light-emitting diode. One socket can be used as a battery tester by inserting a mono jack plug therein. A jack plug lead can be tested and fault diagnosis carried out using the outermost contact pair of the two sockets as a continuity tester. <IMAGE>

Description

SPECIFICATION Device for testing jack plugs and jack plug leads Field ofinvention This invention concerns a testing device by which the condition of a jack plug and of a lead connecting thereto can be checked. The device is particularly useful for testing leads having jack plugs connected to both ends thereof which are conventionally referred to as jack plug leads.

Background to the invention Atesting device is known having two sockets into which the two jack plugs of a jack plug lead can be fitted and which includes a plurality of switches for connecting different checking circuits to the lead and plugs. The device requires considerable concentration to determine whether a plug or lead is satisfactory and to isolate and identify any particularfault. It does not lend itself to a quick test of a jack plug lead which is all that is required when on location and setting up equipment and the like. It is more a laboratory or work shop tester which allows the jack plugs and leads to be thoroughly tested and any faults diagnosed before repair.

A second device is known having a number of lamps (typically light emitting diodes to conserve battery power) and two sockets into which the two jack plugs of a jack plug lead can be fitted. As with the other device however, considerable skill is needed to determine whether (and if so what) fault exists. The device is confused by the presence of two simultaneous faults in plugs and leads as can often occur.

It is therefore an object of the present invention to provide an improved testing device which readily allows a faulty lead/plug to be spotted and which will not be confused by simultaneous faults which can be used later to identify simply and reliably what fault or faults exists.

It is another object of the invention to provide a device which does not include switches which require to be operated to use the device, switches being expensive components which are prone to damage.

Summary ofthe invention According to one aspect of the present invention a device for testing jack plug leads comprises: a) a housing containing two jack plug sockets adapted to receive the jack plugs, b) a source of emf having a high internal resistance to limit the current flow if short circuited, c) connections serving to connect the source of emf between two normally open contacts of one of the sockets, and e) a low current lamp such as a light-emitting diode connected between normally open contacts of the other socket.

When no jack plugs are inserted, the lamp does not light and no current drains from the source of emf. Upon inserting jack plugs at opposite ends of a lead to the two sockets, the lamp will light only if there is continuity along both of the leads joining the two jack plugs and provided there is no short circuit between the two leads. In the event of open circuit or short circuit the lamp will not light.

Since the device will indicate a fault condition if the source of the emf is low, the device preferably includes a battery indicator.

In one embodiment the battery indicator comprises switches which can be used to connect the respective contacts of the two jack plug sockets together and simulate a good jack plug lead between the two sockets. The switches may be operated by a single push button control. The lamp will light up if the source of the emf is up to strength when the switches are closed.

The source of emf may comprise a battery which if it does not itself have sufficient internal resistance may be connected in series with a resistor having an appropriate ohmic resistance to increase the internal resistance of the source (made up of the battery and resistor in series) as seen by the jack plug socket across which the source is connected.

The battery may be of the re-chargeable type. If so a socket may be provided for connecting to the battery a source of charging emf.

A simple device such as described will allow jack plug leads to be tested with the minimum effort but in general will not reveal whether a lead is open circuit or short circuit or both.

A development of the invention allows the different faults to be indicated by simple procedures and co-incidentally also provides for a battery test without the need for an additional switch. This allows a comprehensive tester to be constructed using the minimum of parts and therefore at minimum cost.

According, therefore to another aspect of the present invention, a jack plug lead tester comprises two multiple way jack plug sockets, each socket including three pairs of normally closed contacts which are opened when a jack plug is inserted therein and which make electrical contact with different conductive regions along the length of the plug when so inserted, two of the said normally closed pairs making contact with the shank of a normal mono jack plug when inserted therein so that the contacts of these two pairs will be short circuited by the shank of a jack plug inserted into the socket irrespective of the condition of the plug or any lead connected thereto, electrical conductor means connecting a source of emf to one of the two contacts shorted by the said plug shank, second conductor means connecting the other contact which is electrically shorted to the first contact on insertion of a plug to a normally closed contact set on the other socket, and third conductor means connecting the opposite side of the source of emf to another contact set on the said second socket, electric lamp means being connected to the said second and third conductor means through the said normally closed contact sets.

It will be seen that if a mono jack plug is inserted fully into the first socket (into a position known as position 3) the shorting of the two contacts of that socket by the shank of the plug will complete a circuit containing the source of the emf and the lamp. By appropriate choice of source and lamp so the latter can be caused to be illuminated upon the circuit being closed.

If the internal impedance of the source (typically a dry battery) is too low, a load resistor may be connected in the third conductor means.

It will be further noted that if the first mentioned jack plug is connected to a second jack plug via a lead and all connections are correct and no short circuit exists, the insertion of the second jack plug fully into the second socket will have the effect of opening the normally closed contact pairs so that the lead conductor connecting the two sleeves of the plugs will connect the first mentioned contact associated with the first socket with one side of the lamp and the tip of the second jack plug will make contact with the opposite side of the lamp.By providing a fourth conductive path between the said other side of the source of emf and the third contact of the first mentioned socket (i.e. that contact which is electrically contacted by the tip of the first plug when fully inserted into the first socket) so the circuit will be completed through the lead conductor which joins the two plug tips. Again the circuit interconnecting the source of emf and the lamp will be completed and the lamp will be illuminated.

The device thus allows a mono jack plug lead to be tested for continuity or short circuit by simply inserting one of the jack plugs fully into the first socket and checking that the lamp illuminated (indicating correct battery condition) and thereafter inserting the other jack plug into the second socket and observing whether the light remains illuminated when the second jack plug has been fully inserted into the second socket. If it does remain illuminated then the lead is good. If the lamp is extinguished then a fault exists on the lead or in the plugs and the jack plug lead can either be tested there and then to ascertain the nature of the fault or can be discarded and replaced by a good lead and subsequently checked to ascertain the nature of the fault to allow the lead to be mended.

Fault diagnosis on a faulty jack plug can be carried out by using the outermost contact pair of the two sockets as a continuity tester. In particular, continuity from the tip or sleeve of one plug to the tip or sleeve of the other can be tested by inserting the plugs into appropriate intermediate positions in the two jack plug sockets. By insertin both plugs into the respective sockets so that the two outermost contact pairs of each socket are opened (position 2), continuity from sleeve to sleeve can be checked, the light source illuminating it the connection is good.

Similarly, by inserting both plugs into the respective sockets so that only the outermost contact pair of each socket is opened (position 1) continuity from tip to tip can be checked, the light source illuminating it the connection is good. Further, if one plug is located in position 1 and the other in position 2 the light source will not illuminate with a correctly operating lead. Confusing readings thus do not arise if a compound fault exists, in contrast to the known complex testers.

For both aspects of the invention, the light source conveniently comprises a light-emitting diode (LED).

In preferred embodiments a bicolour LED is used which illuminates in two different colours depending on the polarity of connections. Thus such an LED will illuminate in one colour (eg green) if a jack plug lead being tested is correctly wired, in another colour (eg red) if the lead is cross wired, and will not illuminate if a fault of a different nature is present. This arrangement thus readily permits a certain degree of fault diagnosis - it is to be noted that in certain circumstances it is very useful to be able to detect the presence of cross wiring of a lead, as such a lead can be used in emergency circumstances.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure lisa circuit diagram of a simple jack plug lead tester embodying the invention, and Figure 2 is a circuit diagram of a more complex design which includes provision for testing the battery and identifying the nature of any fault.

Detailed description of drawings As shown in Figure 1 a jack plug lead tester comprises a battery 10 connected through a resistor 12 having a value typically of the order of 1000 ohms to the tip contact 14 of a first jack plug socket. The sleeve connecting contact of the socket 16 is connected via a conductor 18 to the opposite side of the battery 10.

A light-emitting diode 20 is connected to the sleeve connecting contact 22 and the tip connecting contact 24 of a second jack plug socket.

If the two plugs of a good jack plug lead are inserted fully into the two sockets, a continuous circuit will be established containing the battery the resistor the lead and the light-emitting diode which latter will be illuminated.

If the jack plug lead is open circuit or if a short circuit exists between the conductors of the lead or in the plugs the light-emitting diode will not be illuminated.

Although not shown, a double pole switch may be provided for temporarily bridging the contacts 26 and 28 and the contacts 30 and 32 so that the circuit containing the battery resistor and LED can be completed irrespective of the jack plug lead. In this way the battery condition can be tested since if upon depressing the switch the LED does not illuminate, it can be assumed that the battery is dead.

The device simply allows the condition of a lead to be tested but does not allow any indication of the nature of the fault to be obtained.

The circuit of an improved testing device is shown in Figure 2.

In Figure 2 the two mono jack plug sockets are replaced by two stereo jack plug sockets each having a tip contact 34 and 36 respectively and two sleeve contacts 38 and 40 on the one hand and 42 and 44 on the other. When employed with stereo jack plugs, the tip of the plug engages for example contact 34, the first part of the sleeve a contact such as 38 and the last part of the sleeve makes contact with contact 40.

Such a socket will accept a mono jack plug (as is normally used with stage amplifying equipment and the like with which the testing device is generally intended to be used) but when a mono plug is inserted, whilst the tip contact 34 makes proper contact with the tip, the other two contacts such as 38 and 40 are electrically shorted by the continuous electrical shank of the mono plug.

This fact is used in the circuit of Figure 2 to allow not only the battery condition to be indicated (as will hereinafter be described) but also allows fault identification tests to be performed using intermediate positions of the jack plugs in the sockets.

The first shank contact 40 is connected to one side of a battery 46 the other side of which is connected through a resistor 48 typically having a value of 1000 ohms to the tip contact 34 of the same socket and through a second resistor 50 also having a value typically of 100,000 ohms to an earthing contact 52 associated with the tip contact 36 of the other socket.

The earthing contact 52 normally makes good electrical contact with the contact 36 but upon inserting a jack plug fully into the second socket, the tip of the plug will not only make contact with the contact 36 but will also displace the contact so as to open the circuit between the contact 36 and contact 52.

The contact 36 is connected to one side of a light-emitting diode 54 the opposite side of which is connected to the shank connecting contact 44 of the second socket.

For convenience a first socket is labelled A and the second socket B.

The earthing contact 56 of the contact 44 of socket B is connected via conductor 58 to the second sleeve contact 38 of socket A.

Upon fully inserting a mono jack plug into socket A, contacts 38 and 40 are electrically shorted together and it will be noted that a circuit containing the battery 46, resistor 50, contacts 52 and 36, light-emitting diode 54, contacts 56 and 44, contacts 38 and 40 will be completed thus causing the light-emitting diode to be illuminated provided the battery 46 is up to strength.

Assuming that the light emitting diode 54 is illuminated, the second jack plug associated with the lead under test can then be inserted into socket B and if inserted fully, and if the lead is in good order, the breaking of the normally closed contacts 36 and 52, and 44 and 56, will be compensated by the continuity between the shanks of the two plugs and the tips of the two plugs via the interconnecting lead.

In this case, however, the circuit will be completed through the resistor 48 rather than the resistor 50.

Furthermore, the lead 58 will serve no purpose and the circuit between contacts 44 and 40 will be completed via the jack plug sleeves and the lead between the jack plugs.

Fault identification on a faulty jack plug lead can be determined by withdrawing the jack plugs until the tip of each jack plug disengages the tip engaging contacts 34 and 36. In this condition, the circuit through resistor 50 to the light emitting diode 54 is completed via normally closed contacts 36 and 52 and the circuit between contacts 40 and 44 is completed via the jack plug lead connecting the two shanks of the plugs which contact the contacts 40 and 44 respectively.

If the lead is good the diode 54 will be illuminated.

Likewise if the two jack plugs are removed until the tips are in the first position, the circuit will be completed through the lead joining the two tips of the jack plugs. If this circuit is good then the light emitting diode will be illuminated. If the lead is not good then the diode will not be illuminated.

Further tests between tip and sleeve and between sleeve and tip can be effected by inserting one of the jack plugs into the first position and the other into the second position or vice versa. Illumination of the diode in either state will indicate a short circuit fauit.

In order to facilitate the fault identification procedure outlined above, the jack plug sockets are provided with click stops to facilitate partial insertion of jack plugs, into intermediate positions 1 and 2.

In both of the embodiments described above, the light-emitting diode is preferably a bicolour LED which illuminates in two different colours (eg green and red) depending on the polarity of connections.

This feature permits cross wiring of a lead to be diagnosed, as discussed above.

The components of the testing devices are located in a suitable housing, for example in the form of a moulded plastics eg nylon casing, possible with integrally formed jack sockets.

Claims (12)

1. A device for testing jack plug leads comprising a) two jack plug sockets adapted to receive the jack plugs.

b) a source of emf having a high internal resistance to limit the current flow if short circuited.

c) connections serving to connect the source of emf between two normally open contacts of one of the sockets, and e) a low current light source connected between normally open contacts of the other socket.

2. A device according to claim 1, including a battery indicator.

3. A device according to claim 2, wherein the battery indicator comprises switch means which can be used to connect the respective contacts of the two jack plug sockets together and stimulate a good jack plug lead between the two sockets.

4. A device according to claim 3 wherein the switch means is operated by a single push button control.

5. A device for testing jack plug leads, comprising first and second multiple way jack plug sockets, each socket including three pairs of normally closed contacts which are opened when a jack plug is inserted therein and which makes electrical contact with different conductive regions along the lengths of the plug when so inserted, the pairs of contacts for each socket including a first pair for contacting the tip of a jack plug when fully inserted into the socket, and second and third pairs for contacting spaced region of the shank of a jack plug when fully inserted into the socket, so that the contacts of the second and third pairs will be short circuited by the shank of the jack plug fully inserted into the socket, a source of emf connected by first conductor means to a contact of one the second and third pair of the first socket, a contact of the other of the second and third pair of the first socket being connected by second conductor means to one of the contact pairs of the second socket, the opposite side of the source of emf being connected by third conductor means to another contact pair of the said second socket, a light source being connected to the said second and third conductor means through the relevant contact pairs of the second socket.

6. A device according to claim 5, wherein the jack plug sockets include click stops to assist partial insertion ofjack plugs therein.

7. A device according to any one of the preceding claims, wherein the light source comprises a light-emitting diode.

8. A device according to claim 7, wherein the light source comprises a bicolour light-emitting diode.

9. A device according to any one of the preceding claims, wherein the source of emf comprises a battery.

10. A device according to claim 9, wherein the battery is rechargeable, a recharging socket being provided.

11. A device according to any one of the preceding claims, wherein the components are located in a housing.

12. A device for testing jack plug leads, substantially as herein described with reference to, and as shown in, Figure 1 or 2 of the accompanying drawings.