Installation
Adjusting Potentiometers
MC3000 Digital Deskset Operator and Installation Manual 2-21
(6880309L15-A)
Handset Microphone (mouthpiece) to the TX Line
The audio level is factory set, but if the sensitivity of the handset microphone requires
adjustment, this can be done using potentiometer R90 on the main board.
To adjust the Handset (mouthpiece) Microphone:
1. Use a multi-meter to measure the resistance between point A and B of R90:
2. Adjust R90 to increase or decrease the gain as measured by the multi-
meter.
The lower the resistance value, the higher the gain. The default value for R90 is
approximately 2.85 K ohms.
Desk Microphone to the TX Line
The audio level is factory set, but the sensitivity of the external deskset microphone
requires adjustment, this can be done using potentiometer R57 on the main board.
To adjust the Desk Microphone:
1. Use a multi-meter to measure the resistance between point A and B of R57:
2. Adjust R57 to increase or decrease the gain as measured by the multi-meter.
The lower the resistance value, the higher the gain. The default value for R57 is
approximately 10.5 K ohms.
Headset Microphone to the TX Line
The audio level is factory set, but if the sensitivity of the external headset microphone
requires adjustment, this can be done using potentiometer R61 on the main board.
To adjust the Desk Microphone:
1. Use a multi-meter to measure the resistance between point A and B of R61:
2. Adjust R61 to increase or decrease the gain as measured by the multi-
meter.
The lower the resistance value, the higher the gain. The default value for R61 is
approximately 18.9 K ohms.
Audio from Parallel Desksets (IC or RCU)
The audio level is factory set at 80 mV
RMS
, but if the received audio from parallel desksets
requires adjustment, this can be done using potentiometer R12 on the main board.
To adjust R12:
1. Use a multi-meter to measure the resistance between point A and B of R12:
2. Adjust R12 to increase or decrease the gain as measured by the multi-
meter.
A
B
A
B
A
B
A
B
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