Oscillator 87J
Handheld tone generator for cable pair identification
Made in UK
These are a small handheld unit that are designed to generate a tone pulse and either be directly connected or have this source signal induced into the wire pair - the "sister" equipment (which I have sold already - it is NOT supplied) is a portable amplifier/receiver is used at the point you wish to locate the particular pair of wire. By waving the receiver "wand" around the pairs, you can quickly and easily locate the test pair amongst a myriad of wires within a multicore cable. Once located, the suspect pair is shorted and the source tone should change to confirm this.
Back in the "old" days you could hear these in use by the linesman. Typically you are chatting away on your landline and all of sudden you will hear a clicking or pulse tone on your line, sometimes it will be a warbling sound - very freaky!
It doesn't necessarily mean that the linesman is working on YOUR telephone line but that they are generating a test tone in the same cable as your telephone pair and the signal is being induced into your phone line as well. Could be anywhere, outside your house or right back at the exchange.
This unit is powered by 4x standard AA Alkaline batteries
Push and hold down the top button and it springs into life, the pulsing tone (which you cannot hear of course) is indicated by a pulsing red led.
By pushing the ON/OFF button repeatedly, you can change the pulse rate (four rates can be selected 3, 5, 8.5 and 11.5Hz)
The tone frequency generated is fixed at 1Khz
Using the leads/alligator clips you can direct connect to the pair of wires under test OR you can just have the leads near the pair and the signal is induced into the cable under test (far less precise though and you will not get any correct pair indication)
At some distance point, where you want to identify the correct cable pair of wires, you wave around your amplifier/receiver (advertised separately) - the louder the tone, the closer you are. To confirm you have the correct pair, short them - the tone will stop.
This unit will also allow for the testing/detection of a cable pair for the presence of a short between the two wires - this short can be up to 2Km away, this unit will detect it.
When a short does exist, in addition to the flashing red led - a green led will also light up (pulsing in time with the red led)
Everything is in great shape, it all works fine
The cables (2) for connecting to the wires under test are in excellent condition - no damage to the sheath which feels like a silicon based covering.
Not into telephone cabling? These units are also excellent in any situation where you need to locate a pair of wires in a cable over some distance. You can even just use it to simply identify multiple cables if you have a bundle of them.
Outputs are either DC coupled (transformer) or isolated (capacitor blocked) up to 200V - just depends where you plug the leads in (3 plug sockets on the top being ground, Signal DC and Signal AC.
Very difficult to find these as they are no longer used within the Telco network around, I know for sure that I only have one of this 87J and the associated amplifier/receiver
If the information above is a bit confusing, I have the full manual but these are really simple to use in practice.
These can still be bought in UK, new they cost around $120 Australian
