Cable tracers are used for tracking and troubleshooting cables quickly. They are suitable for identification and maintenance of telephony networks and also for testing any kind of lines not-connected to the mains. Suitable applications are wiring test for computer Local Area Networks (LAN) and telephony extensions.
There are countless cable tracers on the market, but they all operate on similiar principles. They transmit a signal on to the cable and have a receiver that detects that signal.
Method: use the tone generator and the probe to determine where a cable is going and whether or not (and where) the cable is interrupted.
The Tone Generator is a hand held, battery powered instrument designed to perform a variety of tests on unenergized telephone lines or LAN cables. Alligator clips and a standard RJ11 plug allow the tone generator to be connected to stripped wires, terminal panels, wall plates, or modular single line jacks. The Tone Generator usually generates continuous tone or warbled tone with selectable test frequencies. Frequencies are usually around 1kHz frequency.
The Line Tracer is a hand held inductive tracer that will help to identify wires without piercing the insulation. It can trace Tone Generator signals through dry wall, wood and many other non metal surfaces.
The conventional use of the inductive amplifier is the location of breaks in hidden wires, even buried in concrete. The typical wire detection range in a concrete wall is 10-20 cm. One of the manufacturers of the inductive amplifier is Tempo. Inductive amplifiers can also be used to find an individual cable pair in a telephone cross connect or cable head when used in conjunction with a tone generator.
Inductive amplifier can be used to trace mains wiring inside the wall. In case the mains wiring is is or can be reliably disconnected from mains power source, it is possible to trace disconnected mains wiring like telephone wiring is traced. Make sure the power is off before connecting the tone generator. If live mains wiring needs to be tested, you need tools specific for that: Voltage detectors are helpful once you find your wires — they let you test whether the wires are live. You can also buy circuit and wire tracers made specifically for the purpose of locating electrical wiring behind walls and underground. These tools tend to be expensive, though.
Some instructional articles:
How to Use a Wire Tracer article gives you some basic instructions.
Deciphering wiring article has some tips on cable tracing and notes cases where tracers do not always work well.
Are you interested in circuit diagrams of cable tracers? Here are some pointers to those:
My Cable tracing inductive amplifier blog posting has several circuit diagrams.
Fox and Hound cable tracer article has links to generator circuits.
Fox – Hound, Cable Tracers, Signal Tracers, Line Tracers – whatever you want to call them project page has circuit diagrams.
Cable wizard cable tracer manual has many circuit details in it.