3M C960, Service Information

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Installation Instructions
Model C760AA/C960AA
Headset Intercom System
3.5-Inch Duplex Microphone
(78-6911-4476-6)
Microphone Installation Instructions
1.
Determine the type of speaker post and
cut the microphone shield to the
required size.
Determine the microphone shield dimensions for
the type of speaker post present at the installation
location. A typical installation in a speaker post
is shown in Figure 1.
Mark the dimensions on the microphone shield.
Using a razor blade or scissors, cut the shield to
the required size.
2.
Clean the inside of the microphone grill.
Remove any existing foam from the inside of the
grill.
Clean the grill to ensure good tape adhesion. Use
alcohol to remove dirt and oil.
3.
Attach the microphone behind the grill.
Remove the backing from the foam tape and press
the microphone and shield in place behind the
grill. Be sure that the tape adheres well to
provide a good acoustic seal. (The entire grill
area must be blocked by the microphone shield.)
On posts with two cavities, mount the
microphone in the upper cavity and the speaker in
the lower cavity.
Strip the microphone leads and connect them to
the microphone cable from the building. Solder
and tape is recommended. Do not ground the
microphone ground lead to the post.
4.
Fill the hollow area behind the
microphone.
Fill the hollow area behind the microphone with
fiberglass insulation to decrease any echo effect.
Allow at least four inches of clearance around the
light bulb. Use only unfaced (without paper
backing) insulation.
Do not pack the insulation into the cavity. Two to
three feet of insulation - cut to the width of the
cavity - is sufficient.
(continued)