Greenlee TM-500 butt set, pos. Luminescent (glow-in-the-dark) keypad. Can be used safely on a dsl enabled line. High impedance monitor for monitoring line without disrupting existing traffic. Over voltage and over current protection. Tone and pulse dialing for versatility on old and new phone lines. Polarity test with LED indicator. 32 Digit last number redial and pause. 10 number speed dial. Adjustable volume control plus mute. Pause. Flash to generate a timed break recall. Line powered, No battery needed. Headset (included) for hands free operation. Rj11 socket.