I have 2 sets of signal source tracers, aka Tone Generator and Probe Kit , Tone Tracing and Cable Tester for Telephone Line, I also used them for trouble shooting signals on HF radio circuit boards

[HANDY TOOL] Inductive Amplifier is widely used for cable and wire maintenance. The measurement area includes line tracking, short circuit test, and clear/busy/ringing identification. [HIGH ACCURACY] With optional continuous or adjustable generator, the method is simple and the test results are accurate. [CLAMP MODE] For non-terminal cables, clamp mode can be used for direct measurement, as well as for telephone and network line measurement. [ABOUT DETAILS] The gain is norminal 30dB, the input impedance is nominal 100M Ohm, [AVOID SHORT CIRCUIT] Built-in speaker tube on the probe, insulation probe and built-in loudspeaker can effectively avoid short circuit of conductor and make it safer to use. I have a 30 year old set and a newer 20 year old set 125$ for the older set 100$ for the newer set