This lets you find the other end of a cable even in a large tangle of wires. Handy for telephone connection panels, for example. An audio-frequency signal is fed to one end and the test probe is used to find where the signal is leaking out. The tracing measurement is performed without galvanic contact.

The audio signal generator also includes an LED-display continuity tester.

Both devices operate on a 9V snap battery (included). A zippered storage pouch is also included.