The Fluke Networks TS19 Test Set combines all the essential test set features at an affordable price. This test set was specifically designed for in-house telecom technicians. Its high impedance monitor prevents accidental disruption of service from clipping onto a data line while in monitor mode, thus ensuring the integrity of critical data lines. Features such as tone (DTMF) or pulse operation, talk/monitor capabilities, polarity test button and last number redial make this test set the perfect combination of features and price.The TS19 telephone test set, available with various line cord connectors to suit specific applications, is designed for in-house testing of telephone lines to detect dial tone and polarity, make and receive calls, monitor lines without disrupting service, and redial the last number called up to 18 digits, retaining the number for up to 15 minutes after disconnecting from a working telephone line. The test set provides tone or pulse operation and can be used to locate short and open circuits, and to verify continuity. It has an LED that lights red to indicate line polarity, and passes a 3.28-foot (1 m) drop test. The keypad has 12 standard dialing keys including star and pound, and a three-position slide switch allows selection of HI-Z mode for high-impedance monitoring without disrupting service, ring mode for low-impedance monitoring and detecting ringing voltage, and talk mode for dialing and talking. A belt clip at the base of the unit provides a secure hold on belt loops and D-rings. Additional specifications include various environmental operating conditions. Telephone test sets, also called butt sets, are used by telecom technicians to troubleshoot and maintain copper-wire voice-subscriber lines.