The Fluke Networks TS54 TDR test set, available with various line cord connectors to suit specific applications, incorporates a TDR, tone generator, and telephone test set into one tool for testing VDV cabling as well as POTS quality on live DSL lines without disrupting data services. The TDR (time-domain reflectometer) measures cable length and locates faults on virtually all types of cable including twisted pair, coaxial, and parallel conductors, finding the distance to open and short circuits in up to 3,000 of cabling. It has an adjustable VOP (velocity of propagation) setting to optimize the accuracy of fault location and cable length measurements. The analog tone generator sends a signal through wires for locating and tracing wires with a probe (sold separately), and has five distinct SmartTone cadences for isolating individual wire pairs. The telephone test set is designed for outside plant use to detect dial tone and polarity, place and receive calls, indicate line voltage and current, and verify caller ID and call waiting caller ID services; has a two-way, adjustable-volume speakerphone for hands-free conversation during testing; monitors lines without disrupting service; locks out off-hook testing when high-speed data is detected; and stores up to nine 23-digit telephone numbers which can be speed-dialed via the keypad. It provides tone or pulse operation. The test set has two basic modes of operation: talk mode for off-hook operations including verifying dialing and receiving calls, and monitor mode for on-hook operations including checking for an idle line, listening for line noise, measuring DC voltage on the line, and capturing DTMF (dual-tone multi-frequency) tones to check for proper signaling. In monitor mode, the test set provides a high impedance coupling to monitor lines without disrupting service. When switching to talk mode, the data lockout feature tests the line for high-speed data signals and remains on hook and beeps if such signals are detected. The lockout can be overridden to pull dial tone from a noise line. Telephone test sets, also called butt sets, are used by telecom technicians to troubleshoot and maintain copper-wire voice-subscriber lines such as POTS (plain old telephone service) lines. TDRs are used by network and telecom technicians and installers to troubleshoot, maintain, and optimize performance of VDV (voice, data, and video) cabling.