The gentleman from Barth International bought a Barth that had almost all red wiring, as I sure most of you know, and had the job of IDing wires like we all do at some point. He bought a tone and probe kit which you can get on Amazon for $50 and prices go up from there. Basically you clamp on the toner at what ever point and then go to whereever like your wiring cabinet and start touching the probe until you get the tone and then you know you have the right wire. Used extensively in telecom where you see all of that bell wire on cross-connect frames. FWIW.