Use this wire tracer kit to quickly find cables, determine if a line is broken, and test telephone wires. Connect transmitter to wires using the alligator clips or insert the RJ11 plug directly into a telephone jack. Insulated probe protects cables under test from shorting. Built-in speaker with adjustable volume/sensitivity audibly alerts you when the correct cable is found. Green, yellow and red LEDs light up steadily, flicker, or dim and brighten in response to different wiring conditions and tests.