Looks like a what we call a "tone set". basicly it sends a radio signal down a pair of wires. You need an amplifier/probe to pick up the signal. the amp' used by OR engineers looks like a very fat marker pen. The BT tone sets typicaly are mid blue (or grey/blue for newer ones) About the size of a glasses case. (much older ones a bigger and bright yellow)
The amp picks up the tone (the bt ones send a beep. usual speed is about 2 a second, although you can change the speed so you can distinguish one tone from another) when the amp is in close proximity to the wires. If you short out the pair then the tone dissapears altogether so hey presto thats your pair that you were looking for.
Its one of the handyest tools a comms engineer can have. If you see an engineer in a mass of wires and wonder how do they know which pair they are looking for. Sometimes thats how we find them.
you can send the signal on a known pair of wires and elsewhere figure out exactly which wire/block/connector it pops up on. Or along which cable the wires run.
Or to confirm the fact that some idiot connected an earth wire under the plasterwork between the earth on a faulty ring main to the telephone extention cable somewhere under the plaster which explained the blinding blue flash on removing an nte followed by a big bang and all the fuses going in the barn conversion. (customer was suffering from repeatedly dead modems and an occasional loud buzzing on the line)
maplins sell a couple of tone set models. A OR engineer would typicaly have 2-3.
if you see a chap holding a black plastic wedge about 120mm wide and a metre long sweeping one end above the ground. This is a bigger version of the amp. This is known as a C.A.T. (cable avoidance tool) with which you can pick up underground electrical cables or in conjunction with a genny (signal generator). This looks like a small tool box and is a bigger version of a tone set. It can be connected directly to wiring or have an inductor cliped around a cable, or just sat over a cable or metal pipe. this will send a signal along the cable as a tone set would. Another end would be connected to ground typicaly a screwdriver in the soil (which is the second set of instructions on your photo).
With this you can very accurately pinpoint hidden cabling and locate their depth. the cat is cranked down in volume until you can pin point the cable to within a centimetre. tilt it at 45 degrees and then move it away until the signal drops. the distance from the vertical position to the new position is the depth of the cable. You may see paint markings on the road/pavement sometimes. A dot indicates a utility directly below. and a stripe either side denotes the depth (from the dot to either stripe) the stripe is either side the lenght of the utility so you know which direction the utility runs. And one stripe each side of the dot. So if its being dug out, one gets covered by spoil, the other is still seen as a reference by the digger.
Grey paint = telecoms, red = power, yellow=gas, blue=processed water, green =waste water/sewage. White= pretty patterns marked by the local council which no one can understand.
A box with an X in the middle= dig hole here
You can hire these and you'll be amazed how accurately you can locate stuff underground.
