3M A125 User Manual

Noise Reduction Module

Model A125

Installation Instructions

Description

The 3M A125 Noise Reduction board (3M part number 78-9236-6453-2) improves the inbound intelligibility of an
intercom system by reducing environmental background noise from vehicles, airplanes, noisy intersections, wind,
etc.

System Requirements

The 3M A125 Noise Reduction Module requires a 3M model C921BA or C922AA Base Station.

Installing the Noise Reduction board into the 3M Base Station

1. Remove the right-hand and left-hand top covers from the 3M base station. Be careful that the main circuit
board does not fall out of the plastic base.

2. See ***Important installation notice*** on next page before performing this step.
Plug the A125 ribbon cable onto connector J8, located at the top of the left side of the circuit board. Be careful
to support the rear side of the base station circuit board when plugging in the A125 ribbon cable.

3. Position the holes near the edge of the A125 circuit board over the plastic standoffs on the base station.

4. Attach the left-hand base station cover after configuring the A125 board, and performing the Final Checkout
Procedure.

Install the A125 board here

Figure 1. Mounting the A125 to the C921BA Base Station

***Important installation notice***

Starting with serial number 125002477, the A125 Noise Reduction Module, Internal has a wider ribbon
cable plug. A limited number of these Noise Reduction Modules have two individual ribbon cable plugs.
The wider ribbon cable plug(s) are too wide to fit into the blue 20-pin base station receptacle. The
receptacle on the wireless base station board must be trimmed and the ends opened. Use a sharp razor
knife and make four vertical cuts. Fold the ends of the blue receptacle down as shown below.

Caution - Be careful to not cut any components or circuit traces on the base station circuit board.
Caution - Be careful to pull only on the ribbon connector plug. Pulling on the ribbon cable itself may

cause it to separate from the plug.

Instructions for trimming and opening the base station receptacle:

1. Make a vertical cut at each corner of the blue 20-pin receptacle on the base station circuit
board.

2. Fold the short end sides down as shown

3. Carefully insert the ribbon cable plug(s) into the blue receptacle. The locking tab will not
engage and should not be a problem.

2