Our three channel FM wireless intercom system allows a choice of three channels to talk to or monitor any number of rooms or offices. The FM-300A simply plugs into any AC outlet. It features a lock button, which allows for continuous talk. It is capable of up to a 1500 ft range. The intercom has adjustable volume control with low, middle and high levels, and even a call feature when not in lock mode. This model replaces the FM-300. This intercom is also available in a two channel version undermodel number FM-200A. FM-300A Technical Specifications Channels 3 Power Source 120V AC Carrier Frequency Channel A 230 kHz, Channel B 260 kHz, Channel C 290 kHz RF Output Power 100 mW Audio Output Power 500 mW Modulation Method Frequency Modulation (FM) Transmission and Reception Phase Locked Loop (P.L.L.) Dimensions 5"L x 7 1/4"W x 1 1/2"H (1 unit) Weight 1 lb (1 unit)