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Noise Reduction Module
Model A121
Installation Instructions
Description
The 3M Noise Reduction Module (3M part number 78-9236-6403-7) improves the inbound intelligibility of an
intercom system by reducing environmental background noise from vehicles, airplanes, noisy intersections, etc.
Additional Material Required
• 18 - 22 AWG twisted - shielded pair audio wire
• 2 mounting screws and appropriate wall anchors
Important: The 3M Noise Reduction Module should be mounted no more than 3 feet from the intercom or base
station.
System Requirements
The 3M Noise Reduction Module requires a system with a separate outside microphone and speaker. The A121 will
not function with an intercom system configured to use a single speaker as both the microphone and speaker. The
A121 will work in conjunction with most dynamic microphones and speaker/microphone assemblies.
System Configuration
The 3M Noise Reduction Module configuration is controlled by two jumper switch (JMP1 and JMP2) settings.
JMP1 is used to set the appropriate gain for the MENU MICROPHONE.
JMP2 is used to match the A121 output level to the input of the intercom system.
Jumper
Position
Position A Position B
JMP1
* Separate microphone
& speaker at menu
sign/post
Do not use this position
JMP2
* 3M Intercom HME Intercom
Note: * Indicates factory default settings
Table 1. 3M Noise Reduction Module Jumper Settings