3M A121 Noise Reduction Module Installation Instructions

3M A121 Noise Reduction Module enhances the clarity of intercom systems by reducing background noise from traffic, airplanes, and other sources. Compatible with most dynamic microphones and speaker/microphone assemblies, it can be configured for various noise reduction levels and features echo reduction for full-duplex systems. With separate controls for microphone gain and output level matching, the A121 is easy to set up and use, providing a clear and intelligible audio experience in noisy environments.

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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

JMP1

Position A Position B

JMP2

* Separate microphone

& speaker at menu sign/post

* 3M Intercom

Do not use this position

HME Intercom

Note: * Indicates factory default settings

Table 1. 3M Noise Reduction Module Jumper Settings

Mode Configuration

The 3M Noise Reduction Board can be configured in several different modes by setting DIP switch, SW2.

Following is a brief description of each mode and a DIP switch setting table.

Noise Reduction: With SW2 number 1 ON, the inbound microphone voice signal is digitized. The noise is digitally removed from the voice and converted back to an analog voice signal. The analog voice signal is then sent to the microphone input of the intercom.

Echo Reduction: With SW2 number 2 ON, echo is reduced for full-duplex intercom systems. Set SW2 number 2 OFF for half-duplex systems.

Restaurant/Truck Stop Noise Reduction Level: With SW2 number 3 OFF, the A121 is set for restaurant noise reduction level. With SW2 number 3 ON, the A121 is used for truck stop noise reduction level, which provides more noise reduction with slightly more voice degradation.

Hi Frequency Equalization: With SW2 number 4 ON, the higher-end frequencies are increased by 3 dB. This should be set to the customer’s preference.

SW2

Number

ON Position

1 *Noise Reduction ON

(Normal Mode)

2 *

Echo Reduction ON

Truck Stop Noise

Reduction Level

Hi Frequency Equalization

OFF Position

Test Mode

(Factory use only; do not change.)

Echo Reduction OFF

Restaurant Noise

Reduction Level

Hi Frequency Equalization OFF

5 Not Used Not Used

Notes: * Indicates factory settings.

Must be ON for 3M, HME, and Panasonic Full Duplex Systems

Set to customer preference.

Table 2. 3M Noise Reduction Module SW2 Settings

Status Indication Table

The condition of the red LED on the 3m Noise Reduction Module indicates the current status of the unit. The LED can be off, blink at defined intervals, or be constantly lit Table 3 illustrates the status indicated by the LED.

Status LED

Power OFF

Normal Mode

LED off.

LED blinks once per second.

Test Mode

Fault Condition

LED blinks three times per second.

LED is solid red (constantly illuminated).

Table 3. 3M Noise Reduction Module Status Indication

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 Possible Correction

1. Status fault indicated. Inbound audio exceeded maximum level.

Switch A121 off for one second.

2. No inbound audio.

3. No outbound audio.

4. Loud audio in 3M headset when headset user talks.

5. Excessive echo

Mode setting is incorrect.

Wiring is incorrect.

Inbound audio on 3M base station too low.

Excessive feedback from menu speaker to menu mic.

Check mode configuration.

Check wiring.

Increase MENU MIC SENS potentiometer. Headset user should then reduce the headset audio volume.

Add extra acoustic insulation to menu mic chamber.

Table 4. A121 Noise Reduction Module Troubleshooting

Wiring Diagrams

3M Base Station

MIC OUT

MIC

SHIELD

MENU SPKR

AUDIO OUT

ALT ALERT

VEH DET

ALERT OUT

MENU

MIC IN

2 MIC IN

3 SHLD

SPKR

INTERCOM

MIC OUT 1

MIC OUT 2

SHLD 3

SPKR

Menu Post

MIC

SPKR

12V UNREG

A121 Noise Reduction Module

Figure 1. Wiring for 3M C760/960/1060 Base Station

Figure 2. Wiring for 3M C760/960/1060 Base Station with Interconnect Module

3M Base Station

MIC

SHIELD

MENU SPKR

A121 Noise Reduction Module

MENU

MIC IN

2 MIC IN

3 SHLD

SPKR

INTERCOM

MIC OUT 1

MIC OUT 2

SHLD 3

SPKR

Menu Post

AUDIO OUT

ALT ALERT

MIC OUT

SHLD

COM

SPKR

SHLD

SPEAKER

VEH DET

VEH DET MIC IN

MIC

ALERT OUT

COM

AUDIO IN

MIC IN

12V UNREG

3M Audio-Level Control

To Vehicle Detector

Figure 3. Wiring for 3M C760/960/1060 Base Station with 3M Audio-Level Control Module

3M D15/D30 Intercom

MIC

SHIELD

A121 Noise Reduction Module

MENU

MIC IN

2 MIC IN

3 SHLD

SPKR

INTERCOM

MIC OUT 1

MIC OUT 2

SHLD 3

SPKR

SPEAKER

Menu Post

MIC

SPKR

Figure 4. Wiring for 3M D15/D30 Intercom

C921AA Base Station

MIC

SHIELD

MENU SPKR

MON SPKR

COM

AUDIO IN

AUDIO OUT

ALT ALERT

VEH DET

ALERT OUT

COM

12V UNREG

A300 Audio Greeter

INTERCOM SPKR

COM

INTERCOM MIC

MENU SPKR

COM

MENU MIC

J10

TIMER TRIG

COM

MSG4 TRIG

VEH DET-

VEH DET+

COM

MUSIC

COM

_____

TALK

AUDIO OUT

COM

VEH DET

AUDIO IN

MENU SPKR

MIC

MENU SPKR

MIC OUT

Optional Service Timer

A121 Noise Reduction Module

MENU

MIC IN

2 MIC IN

3 SHLD

SPKR

INTERCOM

MIC OUT 1

MIC OUT 2

SHLD 3

SPKR

Menu Post

SPKR

MIC

VEHICLE

DETECTOR

Figure 5. Wiring for 3M C760/960/1060 Base Station with A300 Audio Greeter

Menu Post

MENU MIC

MENU SPKR

A121

Noise Reduction Module

MENU INTERCOM

1 MIC IN MIC OUT 1

2 MIC IN

3 SHLD

SPKR

MIC OUT 2

SHLD 3

SPKR

Panasonic WX-C510/WX-C1010

Base Station

GND

COM

GND

Figure 6. Wiring for Panasonic WX-C510/WX-C1010 Base Station

HME SYS2500/DS/DSL

Base Station

MIC/SPKR

SHIELD

A121 Noise Reduction Module

MENU

MIC IN

2 MIC IN

3 SHLD

SPKR

INTERCOM

MIC OUT 1

MIC OUT 2

SHLD 3

SPKR

OUTSIDE SPKR

* Needed for HME

"Hands Free" system

Menu Post

MIC

SPKR

Figure 7. Wiring for HME SYS2500/DS/DSL Base Station

INTERCOM SPKR

COM

INTERCOM MIC

MENU SPKR

COM

MENU MIC

J10

3M A300

Audio Greeter

TIMER TRIG

COM

MSG4 TRIG

VEH DET-

VEH DET+

COM

MUSIC

COM

_____

TALK

AUDIO OUT

** Note:

Set A300 vehicle detector trigger polarity to negative (set

SW2 number 3 OFF and

JMP1 to Position B).

Terminals 6 and 9 may also be used for a contact-closure connection.

VEH DET SIG

VEH DET GND

10 WHITE

9 GREEN

SHLD

BLACK

RED

MENU SPKR

MIC OUT

VEHICLE

DETECTOR

MENU INTERCOM

1 MIC IN MIC OUT 1

2 MIC IN MIC OUT 2

3 SHLD

SPKR

SHLD 3

SPKR

GND

OUTPUT

3M A121 Noise Reduction Module

Menu Post

MIC

SPKR

HME

SYS2500D/DS/DSL

Base Station

SHLD

BLACK

RED

SPKR/MIC

VEH DET SIG

VEH DET GND

RED

BLACK

WHITE

GREEN

OUTSIDE

SPEAKER

Figure 8. Wiring for HME SYS2500D/DS/DSL Base Station with 3M A300 Audio Greeter

VEHICLE

DETECTOR

HME MR100A

Message Repeater

MENU SPKR

GND (SHIELD)

MENU MIC

BASE SPKR CONN

GND (SHIELD)

BASE MIC CONN

VEH DET IN

VEH DET OUT

ENABLE/DISABLE

EXT PLAY CANCEL

GND

MENU SPKR

9 MIC OUT

MIC OUT 10

11 WHITE

12 GREEN

SHLD

14 RED

15 BLACK

16 VEH DET SIG

20 VEH DET GND

GND

OUTPUT

HME

SYS2500D/DS/DSL

Base Station

SHLD

BLACK

SPKR/MIC

RED

VEH DET SIG

VEH DET GND

RED

BLACK

WHITE

GREEN

OUTSIDE

SPEAKER

Menu Post

MIC

SPKR

MENU

1 MIC IN

2 MIC IN

3 SHLD

SPKR

INTERCOM

MIC OUT 1

MIC OUT 2

SHLD 3

SPKR

3M A121 Noise Reduction Module

Figure 9. Wiring for HME SYS2500D/DS/DSL Base Station with HME MR100A Message Repeater

Food Services trade Department

3M ©

St. Paul, MN 55144-1000

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