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
* 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
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 Cause
Correction
1. Status fault indicated.
Inbound audio exceeded maximum
level.
Switch A121 off for one second.
2. No inbound audio.
Mode setting is incorrect.
Wiring is incorrect.
Check mode configuration.
Check wiring.
3. No outbound audio.
Wiring is incorrect.
Check wiring.
4. Loud audio in 3M
headset when headset user
talks.
Inbound audio on 3M base station too
low.
Increase MENU MIC SENS
potentiometer. Headset user should
then reduce the headset audio volume.
5. Excessive echo
Excessive feedback from menu
speaker to menu mic.
Add extra acoustic insulation to menu
mic chamber.
Table 4. A121 Noise Reduction Module Troubleshooting
Wiring Diagrams
3M Base Station
MIC OUT
MIC OUT
MIC
MIC
SHIELD
MENU SPKR
MENU SPKR
MENU SPKR
MENU SPKR
Menu Post
MENU
INTERCOM
1
2
3
4
5
MIC IN
MIC OUT
1
2
3
4
5
MENU
MIC
MIC IN
SHLD
MIC OUT
SHLD
AUDIO OUT
ALT ALERT
VEH DET
MENU
SPKR
MENU
SPKR
MENU
SPKR
MENU
SPKR
MENU
SPKR
ALERT OUT
12V UNREG
A121 Noise Reduction Module
Figure 1. Wiring for 3M C760/960/1060 Base Station
3
Figure 2. Wiring for 3M C760/960/1060 Base Station with Interconnect Module
4
A121 Noise Reduction Module
MENU
INTERCOM
3M Base Station
1
2
3
4
5
MIC IN
MIC OUT
1
2
3
4
5
MIC IN
SHLD
MIC OUT
SHLD
MIC
MIC
MENU
SPKR
MENU
SPKR
SHIELD
MENU
SPKR
MENU
SPKR
MENU SPKR
MENU SPKR
Menu Post
MIC OUT
MIC OUT
SHLD
COM
MENU
SPEAKER
MENU
SPKR
AUDIO OUT
ALT ALERT
VEH DET
SHLD
VEH DET
COM
MIC IN
MIC IN
MENU
MIC
ALERT OUT
COM
AUDIO 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
MIC
SHIELD
A121 Noise Reduction Module
MENU
INTERCOM
1
2
3
4
5
MIC IN
MIC OUT
1
2
3
4
5
SPEAKER
SPEAKER
MIC IN
SHLD
MIC OUT
SHLD
MENU
SPKR
MENU
SPKR
MENU
SPKR
MENU
SPKR
Menu Post
MENU
MIC
MENU
SPKR
Figure 4. Wiring for 3M D15/D30 Intercom
5
A300 Audio Greeter
Optional Service Timer
C921AA Base Station
12
MIC
MIC
TIMER TRIG
11
COM
10
MSG4 TRIG
SHIELD
COM
9
VEH DET-
MENU SPKR
VEH DET
8
VEH DET+
7
MENU SPKR
MON SPKR
6
COM
5
MUSIC
COM
AUDIO IN
4
MUSIC
3
AUDIO OUT
COM
_____
TALK
2
ALT ALERT
VEH DET
ALERT OUT
COM
AUDIO IN
1
AUDIO OUT
J9
10
MENU SPKR
INTERCOM SPKR
9
MENU SPKR
INTERCOM SPKR
12V UNREG
8
COM
A121 Noise Reduction Module
7
MIC
MIC
INTERCOM MIC
6
INTERCOM MIC
Menu Post
MENU
INTERCOM
5
4
3
2
1
MENU SPKR
MENU SPKR
MENU SPKR
MENU SPKR
COM
1
2
3
4
5
MIC IN
MIC OUT
1
2
3
4
5
MENU
SPKR
MIC IN
SHLD
MIC OUT
SHLD
MIC OUT
MIC OUT
MENU MIC
MENU
SPKR
MENU
SPKR
MENU
MIC
MEJNU10MIC
MENU
SPKR
MENU
SPKR
VEHICLE
DETECTOR
Figure 5. Wiring for 3M C760/960/1060 Base Station with A300 Audio Greeter
6
Panasonic WX-C510/WX-C1010
Base Station
H
C
GND
C
H
H
A121
C
Noise Reduction Module
Menu Post
H
MENU
INTERCOM
1
2
3
4
5
MIC IN
MIC OUT
1
2
3
4
5
COM
GND
AC
MENU MIC
MIC IN
SHLD
MIC OUT
SHLD
MENU
SPKR
MENU
SPKR
AC
MENU SPKR
MENU
SPKR
MENU
SPKR
Figure 6. Wiring for Panasonic WX-C510/WX-C1010 Base Station
HME SYS2500/DS/DSL
Base Station
MIC/SPKR
MIC/SPKR
SHIELD
OUTSIDE SPKR
A121 Noise Reduction Module
OUTSIDE SPKR
MENU
INTERCOM
1
2
3
4
5
MIC IN
MIC OUT
1
2
3
4
5
MIC IN
SHLD
MIC OUT
SHLD
*
Needed for HME
"Hands Free" system
*
MENU
SPKR
MENU
SPKR
*
MENU
SPKR
MENU
SPKR
Menu Post
MENU
MIC
MENU
SPKR
Figure 7. Wiring for HME SYS2500/DS/DSL Base Station
7
VEHICLE
DETECTOR
** Note:
Set A300 vehicle detector
trigger polarity to negative (set
SW2 number 3 OFF and
JMP1 to Position B).
5
HME
3M A300
Audio Greeter
6
SYS2500D/DS/DSL
Base Station
GND
7
OUTPUT *
8
12
Terminals 6 and 9 may also
be used for a contact-closure
connection.
TIMER TRIG
9
11
COM
10
11
12
13
14
10
MSG4 TRIG
** VEH DET SIG
9
VEH DET-
8
SHLD
VEH DET+
7
BLACK
SPKR/MIC
VEH DET GND
6
RED
COM
J1
5
MUSIC
4
MUSIC
4
3
COM
_____
TALK
5
2
VEH DET SIG
VEH DET GND
RED
6
1
AUDIO OUT
J9
7
8
10
9
WHITE
BLACK
INTERCOM SPKR
INTERCOM SPKR
GREEN
9
WHITE
OUTSIDE
SPEAKER
10
8
7
6
5
4
3
2
1
SHLD
3M A121 Noise Reduction Module
COM
INTERCOM MIC
INTERCOM MIC
MENU SPKR
MENU SPKR
COM
GREEN
J7
BLACK
Menu Post
MENU
INTERCOM
RED
1
2
3
4
5
MIC IN MIC OUT
1
2
3
4
5
MENU SPKR
MENU SPKR
MENU
MIC
MIC IN MIC OUT
SHLD
SHLD
MENU
SPKR
MENU
SPKR
MIC OUT
MIC OUT
MENU
SPKR
MENU MIC
MENU
SPKR
MENU
SPKR
MEJNU10MIC
Figure 8. Wiring for HME SYS2500D/DS/DSL Base Station with 3M A300 Audio Greeter
8
VEHICLE
DETECTOR
5
HME
HME MR100A
Message Repeater
6
SYS2500D/DS/DSL
Base Station
GND
7
OUTPUT
8
6
MENU SPKR
MENU SPKR
MENU SPKR
MENU SPKR
GND (SHIELD)
MENU MIC
9
7
10
11
12
13
14
8
MIC OUT
MIC OUT
WHITE
9
10
11
12
13
14
SHLD
MENU MIC
BLACK
SPKR/MIC
RED
J1
BASE SPKR CONN
GREEN
BASE SPKR CONN
SHLD
RED
GND (SHIELD)
BASE MIC CONN
4
15
16
BLACK
BASE MIC CONN
VEH DET IN
VEH DET SIG
5
VEH DET SIG
VEH DET GND
RED
6
17
18
19
20
VEH DET OUT
7
ENABLE/DISABLE
8
BLACK
EXT PLAY CANCEL
GND
9
VEH DET GND
WHITE
OUTSIDE
10
SPEAKER
GREEN
J7
Menu Post
MENU
INTERCOM
1
2
3
4
5
MIC IN
MIC OUT
MIC OUT
SHLD
1
2
3
4
5
MENU
MIC
MIC IN
SHLD
MENU
SPKR
MENU
SPKR
MENU
SPKR
MENU
SPKR
MENU
SPKR
3M A121 Noise Reduction Module
Figure 9. Wiring for HME SYS2500D/DS/DSL Base Station with HME MR100A Message Repeater
3M Commercial Care Division
Food Services trade Department
3M Center
© 3M 2006 May
St. Paul, MN 55144-1000
78-6912-0699-5 Rev. E
9
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