This cable detector works acoustically and offers a quick and inexpensive solution to find voltage-free lines in the house installation, to test telephone lines, to identify individual cables / wires or to carry out a continuity test. With the transmitter / sound generator, a carrier signal is modulated onto an electrical conductor, which you can track with the receiver / amplifier and the integrated speaker or via a headphone. You can also adjust the sensitivity using a rotary wheel on the receiver in order to carry out the best possible identification. When connected to a telephone socket via the RJ-11 connector, the LED of the transmitter indicates the status of the active telephone line between “free”, “busy” or “ringing”. In addition, the transmitter has a continuity test, which lights up when passing through and weakens as the resistance increases.