This instrument is designed to identify and trace wires or cables without damaging the insulation, you can also use it to check for short circuits locate open circuits, and so on. In addition, it can also be used to identify some states of telephone lines so that it is more convenient to install, debug, and maintain telephone lines, There are a Sender and a Receiver included in the instrument. Provides an adjustable volume control. Compatible with all common tracing tone sources. Easy cable connection with either RJ-45 jack, patch cord, or alligator clips. Features: Test the continuity of cables or wires. Trace the cables or wires and diagnose the breakpoint. Identify the state of the working telephone line. Transmit a single or alternating tone across cables or wires and receive a signal with a tone probe. Adjustable audio on tone probe. Includes RJ11 jack for telephones and alligator-style clips for wires. Heavy-duty design for years of trouble-free use. Specifications: Testing polarity of phone lines. Tracing a wire. Finding wires buried behind drywall. Test whether a cable is interrupted. Find interrupts in cableuit. Power: 9V battery (Not Included). Package Included: 1 x Cable Emitter(battery not included) 1 x Cable Receiver(battery not included) 1 x RJ11 Cable 1 x RJ45 Cable 1 x Instruction Manual Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.