The Extech CT20 is an electronic tool for electricians, alarm, cable installers and others who routinely need to check circuits for continuity and also identify cables and wires. It allows a single user to quickly identify and label two wires even when the wire ends are located in different rooms. It can accommodate test wire lengths up to 10,000-feet (3,000 meters), 26-gauge minimum. The Extech CT20’s Remote Continuity mode allows the user to check continuity and to identify two or more cables/wires simultaneously.