Ecloud ShopUS Telephone Phone Line Butt Test Tester Lineman Tool Set Three kinds of exterior line plug head. This set offers Last number redial, On/Off and hangup buttons, so the lineman can check your telephone line fault. FSK/DTMF double standard Caller ID display. The function of receiving line and the function of redialling the last group number. Easy for the lineman to check your telephone line fault.