The 420 is a remote audio monitoring substation with a unique design that includes a microphone and electronic preamplifier mounted on a (3) gang plate. The station is ideal for security intercom and audio monitoring applications such as hospital CAT scan rooms. The microphone, preamplifier and speaker provide excellent sensitivity and voice quality for clear, hands-free, two-way communication to a 410 master. The 20 will operate with the GS-400 one-to-one intercom system.