Firecom 3000C Installation & Operation Manual page 32

A D V A N C E D T R O U B L E S H O O T I N G
30.
5. If no fault can be found, then the fault must lie in the Intercom Unit. Contact
Firecom for a Return Authorization to return the Intercom Unit for repair.
J) THE RADIO DOESN'T KEY
1. Check the affected headset location for faulty connections or components. See
"Troubleshooting a Headset Location" (Page 25).
2. If the headset location checks good, verify proper connection of radio interface
pins 3 & 4.
4. Try swapping the Intercom Unit with a known good one (if one is available). If the
problem persists, the problem is in the radio or the Mobile Radio Interface wiring.
5. If no fault can be found, then the fault must lie in the Intercom Unit. Contact
Firecom for a Return Authorization to return the Intercom Unit for repair.
K) ALTERNATOR AND/OR STROBE NOISE IS PRESENT IN TRANSMIT
AUDIO ONLY
1. Verify that the radio interface pins 1 & 2 are connected properly and that all
connections are clean and tight.
2. Check adjustment of the Transmit Audio. See "Intercom Adjustments" (page 14).
Too much gain here will cause excessive background noise to be transmitted along
with the voice. In the worst case, the voice will be somewhat distorted when
transmitting from a quiet place, and will become unintelligible in the presence of
background noise.
3. Using a voltmeter, measure the incoming power to the intercom, looking for an
AC signal. There should be less than 300mV AC present on the power lines.
L) ALTERNATOR AND/OR STROBE NOISE IS PRESENT IN ALL
INTERCOM AUDIO
1. Check for proper positioning of the mic in relation to the speaker's mouth. See
"Microphone Placement" (page 19). Improper mic positioning will defeat the
noise canceling characteristics of the mics.
2. Inspect the headset microphones, making sure that all slots on both sides of the
mic are clean an unobstructed. Obstruction of these slots will hamper or defeat the
noise canceling characteristics of the mics.
3. Disconnect any exterior headset locations. If the noise stops, inspect that location
for water or other contamination. If contamination is present, contact Firecom for
a Return Authorization for repair of the unit.
M) ENGINE NOISE AND SIRENS ARE PRESENT IN TRANSMIT AUDIO
1. Review the set up and operation of the intercom volume and squelch controls. See
"Intercom Controls" (page 20). Possibly the intercom volume is set too high.