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1 General
This Operating Instruction describes the features, components, installation, and operation for the Setcom System
900 and 900E Intercom/Radio Mixers. Prior to commencing installation, read this manual completely through and
check the components ordered against those received. Prior to installation, the radio, alternator, and vehicle
battery should be in good working order. Any pre-existing receive or transmit problems with the radio should be
corrected prior to installation of the intercom.
2 System Description
2.1 IM-900
The Setcom System 900 is a vehicular intercom/radio mixer designed specifically for fire apparatus and other
emergency response vehicles. It provides noise-attenuating dual-speaker headsets with a Noise Reduction
Rating of 24dB for hearing conservation. It improves communications in-route by providing radio interface through
a noise-canceling boom-mounted microphone. An intercom system for communications between crewmembers is
also incorporated. The system is protected from radio frequency interference and vehicle-induced electronic noise
related to sirens, strobe lights, ignition system or alternator. The system provides two radio transmit circuits, this
allows for the Driver and an Officer to access the radio with the Pump Panel Station wired in parallel with the
Driver’s circuit. This means there can be a radio capable headset either at the Driver’s Station or at the Pump
Station, but there should not be a headset plugged into both stations at the same time. If two headsets are
plugged into the same circuit it will reduce the transmit level of the radio transmission and introduce background
noise from the second headset.
NOTE: These two ports are in parallel.
This means that a headset should not be
plugged into both ports at the same
time. Doing so will double load the
transmit circuit and may significantly
reduce the transmit signal level.
Use an IM-900E for vehicles requiring
more than two radio transmit circuits
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