The UT 682D works acoustically to find voltage-free lines in the installation, to test telephone lines and to identify individual cables/wires or to carry out a continuity test. The transmitter/sound generator modulates a carrier signal onto an electrical conductor, which you can listen to using the receiver/amplifier with integrated loudspeaker or via a headphone connection. You can also adjust the sensitivity using a rotary dial on the receiver. When connected to a telephone socket via the RJ-11 plug, the LED on the transmitter indicates the status of the active telephone line between free/busy/ringing. The device has a continuity test, where the LED lights up brightly when there is continuity and dims when there is greater resistance. Product features: