3M 478DA (D-15) - Manual (Page 12)

Technician Troubleshooting Guide Model 479 (D-30)
Problem Possible Cause Correction
No outbound audio:
•
Power Indicator Light
(green) is ON.
•
TALK Indicator Light
(red) is ON when TALK
SWITCH is pressed.
Defective menu speaker,
menu mic, or wiring. Check and replace menu
speaker, menu mic, or wiring.
Defective analog board. Check and replace analog
board.
With car on loop, VEHICLE
Indicator Light (yellow) is
ON, but vehicle detection tone
does not sound. Vehicle Detect-to-Main
signal too low. Adjust R6 to increase signal
level.
Defective analog board. Check and replace analog
board.
With car on loop, VEHICLE
Indicator Light (yellow) is
OFF, and vehicle detection
tone does not sound. Defective logic or analog
board. Check and replace logic or
analog board.
Outbound audio distorted. Defective analog board. Check and replace analog
board.
Defective internal
microphone. Replace microphone.
Defective menu sign
speaker. Replace menu sign speaker.

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