Answer:
Toner probe
Explanation:
A Toner probe is a useful device for the installation of electrical cabling of any type, it can be used as Probe and Tone Tool: it enables someone in finding individual leads among a large number in a cable trunk, without having to either connect or strip the remote end.
Its major use is to trace wires or cables by sending a signal from one end of a wire down its entire length. This is typically done to track the spot of a cut or missing door, window, or other alarm wire.
