Fox - Hound, Cable Tracers, Signal Tracers, Line Tracers - whatever you want to call them
Updated August 30, 2002
(Best if viewed in 1024X768)

This is the device that allows you to trace wires over a distance where multiple wires exist. The phone company uses such a device as do network installers and cable installers. One part of the unit is clipped to a wire and ground or the other of the pair. When turned on, it puts a strong, rich two-tone square wave howl into the wire. The other part of the device is a sensitive audio amplifier and speaker. Slowly waving this device over a group of wires will enable you to detect the correct cable run. Commercial units run about US$75 +/- US$20 or you can build your own from junk box parts for less than US$20. A well stocked junk box and you can probably build it for almost no outlay of funds.

If you want to just buy one, check here:
I have also seen a more heavy duty, industrial grade unit at a well stocked hardware store too. The one at Ideal Industries, is probably the best. Go to their Products link and search part number 62-160 and 62-164 for the product. Around US$80 for each unit.

I built mine in two used metal boxes. Plastic enclosures will work too. Each uses a 9 volt battery. The fox (generator) uses a spst toggle switch and the hound (detector) uses a push button spst switch.

Fet is any N channel JFET such as 2N2457 of MPF102

Fox and Hound - note RJ11 and Alligator clips                                  With covers off, board placement - note toggle & pb switch

Tone generator board                                   Sniffer board - note pb power switch and DB 9 for probe input.
                                                                     I used an existing DB connector. Any connector could be used.

I just hot glued the boards and batteries in place.

If you have an HP compatible Laser Printer, you can download and unzip the following files to print your own boards shown circuit side:

Fox and Hound 1:1 in zip format

Fox and Hound 2:1 in zip format

Unzipping each file to will generate FOX1.PRN or FOX2.PRN
Open a DOS prompt and type [type fox1.prn >lpt1]

Email Rick if you have any comments or questions about this unit.