Wiring Diagrams - 3M c960 Service Information

Final Checkout Procedure
1. Turn the ON/OFF switch of the A121 ON. The red LED should blink slowly. Listen for a reduction in the
background noise.
2. If the A121 is in a half-duplex system, set SW2 number 2 OFF and proceed to step 3.
If the A121 is in a full-duplex system set SW2 number 2 OFF. Speak into the headset mic or intercom mic.
The echo should increase. Turn SW2 number 2 back ON. The echo should decrease.
3. Set SW2 number 3 for appropriate level of noise reduction. Set SW2 number 3 OFF for restaurant mode.
Set SW2 number 3 ON for truck stop mode.
4. Set SW2 number 4 (Hi Frequency Equalization) to customer's preference.
Troubleshooting
Problem
1. Status fault indicated.
2. No inbound audio.
3. No outbound audio.
4. Loud audio in 3M
headset when headset user
talks.
5. Excessive echo

Wiring Diagrams

3M Base Station
MIC
MIC
SHIELD
MENU SPKR
MENU SPKR
AUDIO OUT
ALT ALERT
VEH DET
ALERT OUT
12V UNREG
Possible Cause
Inbound audio exceeded maximum
level.
Mode setting is incorrect.
Wiring is incorrect.
Wiring is incorrect.
Inbound audio on 3M base station too
low.
Excessive feedback from menu
speaker to menu mic.
Table 4. A121 Noise Reduction Module Troubleshooting
MIC OUT
MIC OUT
MENU SPKR
MENU SPKR
A121 Noise Reduction Module
Figure 1. Wiring for 3M C760/C960 Base Station
Switch A121 off for one second.
Check mode configuration.
Check wiring.
Check wiring.
Increase MENU MIC SENS
potentiometer. Headset user should
then reduce the headset audio volume.
Add extra acoustic insulation to menu
mic chamber.
MENU INTERCOM
1 MIC IN MIC OUT 1
2 MIC IN MIC OUT 2
3 SHLD SHLD 3
MENU MENU
4 4
SPKR SPKR
MENU MENU
5 5
SPKR SPKR
3
Correction
Menu Post
MENU
MIC
MENU
SPKR