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Installation Instructions
Noise Reduction Module
Model A121
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 or SPEAKER/MICROPHONE (speaker
used as both a speaker and a 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
OSM (speaker used as both a
speaker and a microphone at
the menu sign/post)
JMP2
* C960 Intercom C5000 Intercom
Note: * Indicates factory default settings
Table 1. 3M Noise Reduction Module Jumper Settings
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