The FOX (PN 3380) is a small, multi-function, hand-held instrument for testing telephone lines. In addition, when used in conjunction with an Inductive Amplifier, like the Triplett HOUND or HOUND 2, the FOX can be used for identifying, locating, or tracing wires inside of or behind surfaces that are electrically non-conductive (like drywall). When used for tracing wires, the FOX can be used with non-energized electrical power wiring, alarm wiring, speaker wiring, coax, cable harnesses, and numerous other wires and cables. For more complete information, see the HOUND or HOUND 2 Instruction Manuals.

To facilitate testing, the FOX uses two alligator clips and a modular plug. These allow the FOX to be quickly connected to stripped wires, terminal panels, or a standard RJ-11 modular jack (single line). Two selector switches set the test function of the FOX, while an LED acts as a visual indicator. By setting the selector switches appropriately, the FOX generates three distinct tracer tones, which, as previously mentioned, can be used for locating wires or cables with an inductive amplifier such as the Triplett HOUND2 or HOUND 3.