Proskit Telephone Butt Set Phone Tester Lineman Tool Cable Set MT-8001Built in amplified speaker provides three audio levels for hands free listening. Functional tone and pulse mode applied to most telephone system. Store up to twelve, 16 digit telephone numbers in speed dial. Pre dialing and last number redial operation save up to 32 digit telephone number Advanced PBX pause function easily inserted between digits of a stored number High impedance monitor mode design provides minor noise output while operating.