The Fluke Networks TS30 telephone test set, available with various line cord connectors to suit specific applications, detects dial tone and polarity; places and receives calls; monitors lines without disrupting service; and retains one 23-digit redial number for about eight minutes. It provides tone or pulse operation. A pair of LEDs on the front of the unit indicates line polarity when off hook. The test set passes a 20-foot (6 m) drop test and is Ingress Protection certified IP54 for protection against dust and splashed water. The keypad has 12 standard dialing keys including star and pound, and function keys to mute, check polarity, redial a number, and pause for accessing a second dial tone when dialing through a PBX (private branch exchange). A two-position switch allows selection of monitor mode for high-impedance monitoring without disrupting service, and talk mode for dialing and talking. The test set is made of high-impact polycarbonate that provides excellent insulating properties. Its contoured hand grip rests on the shoulder to enable hands-free operation. A spring-loaded 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.