Shop name:Chong Qing Shuo Yue Ke Ji You Xian Gong Si This instrument is used to identify and trace wires or cables without damaging the insulation. It can also be used to test for short circuits and locate open circuits. It can also be used to identify phone line conditions to simplify phone line installation, debugging, and maintenance. The instrument includes a transmitter and a receiver an adjustable volume control with all common tracking audio sources RJ-11 sockets, jumpers, or clips for easy wired connection Check the continuity of cables or wires Trace cables or wires and diagnose breakpoints Identify the status on the work phone line Transmit single or alternate audio over cables or wires and audio probes to receive signals Adjustable audio on sound probes Including RJ11 socket for and clip for cables Durable design for many years, -free Battery: 2 * 9V battery (without battery) Color yellow Material: ABS Size: 255 x 120 x 36 mm Package contents: 1 * cable transmitter 1 * cable receiver Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.