The Klein Tools VDV500-123 Probe-PRO Tracing Probe traces non-active wiring when used with Toner-Pro Tone Generator (VDV500-063, sold separately). It features a responsive, durable, replaceable non-metallic, conductive tip and a work light for use in dark spaces. A headphone jack allows for headphone (not included) use in extreme noise environments. The terminal block confirms the toned pair has been located.