This is a really cool piece of equipment capable of saving us hours if not days of work.
There have been plenty of occasions where a wire had broken or shorted somewhere in the aircraft that was not allowed to be broken. (aircraft operate under a minimum equipment list, some systems that are not so important are allowed to be inoperative, some have a repair time limit but some are not allowed to be inoperative period).
When one of those wires breaks and has no spare wire close to it, it will have to be repaired immediately.

If we are unlucky it can take hours or days to find a broken wire somewhere in the aircraft. There are ways to search for these wires offcourse by removing connectors at disconnect stations, bulkheads and such to discriminate where the wire has broken but if there is a large length of wire going under the floor or through a hard to reach place this can turn out to be quite a nightmare. We have also cut wires in the middle to be repaired later just to know in wich direction to search.

The cable tracer is a tool that we can use to find a broken wire with relative ease.
The cable tracer that our company uses has three components, one active signal generator, one passive (for use in powered wire systems up to 300 volts) and one tracer unit wich can be selected in three levels of sensitivity and finetuned to increase the detection range from roughly 1 centimeter to 3 meters.

We connect the active signal generator to a piece of wire that we've spanned across a workbench.
tracer connected to a wire

I select the tracer to maximum sensitivity and step a good 2.5 meters back and still get a clear signal.
The red LED's indicate from 0 to 10, 10 being the strongest reception. The wheel on the right side is the finetuning of the sensitivity and the x1, x10, x100 switch on the left is the course sensitivity selector with x100 being the most sensitive.

Here's the tracer up close with a less sensitive setting. The setting is x1 to get a less sensitive reception and the wheel is turned down to 2.
less sensitive

Let's say the wire was broken at this point.
wire cut

Then we only have to move the tracer away from the end of the wire to find our broken point.
found the broken point

Then let's look at the other option on the tracer, the 'short' option.
short option

When we select the short option we are going to look for a wire that is shorted to ground.
In this case we will use the wire on the bench but halfway we will connect it to a piece of structure to simulate a shorted wire. This time we also connect the black connection on the signal generator to the structure (wich previously wasn't connected).
We connect it all to a H-beam.
wire shorted to ground

This is the way it is now connected.

So the signal anywhere in the loop is received fine.
good reception

So also in the wire from the red test lead towards the H-beam.
reception in the loop

Closer to the H-beam.
find the wire

When we then move the tracer over to the wire leading away from the closed loop the reception gets significantly weaker.
weak reception

And half a meter down is completely gone.
no reception

This tool is pretty handy if u are looking for a broken wire and with a less accurate degree also to find a shorted wire.