AB-120 Announcer Console
2.3.1
Front Panel
Interrupt
Non-Interrupt
AB-120
Announcer Consol e
Interrupt
Level
Control
Non-Interrupt
Level
Control
Mute
Indicator
Mute
Button
Talk Back
Indicator
Talk Back
Button
AB-120 Front Panel Controls
Selecting Microphone Amplifier Gain
The microphone preamplifier and the output line drive amplifier have selectable gains allowing
the user to tailor the gain structure to the type of microphone being used and the desired
output level. As shipped from the factory, microphone gain is set for a dynamic mic and the
output level is set for -10 dBu.
Microphone Preamplifier Gain
The microphone preamplifier gain must be set to provide proper operation of the limiter circuit
used in the talkback system. The preamplifier can be set for gains of 40, 50, and 60 dB.
Dynamic microphones have a nominal output level of approximately -60 dBu. Electret mic
typically have an output level of -40 dBu. Internal jumpers JP9 and JP10 allow selecting the
preamplifier gain to 40, 50, and 60 dB.
INPUT LEVEL
JP 9
JP 10
-60 dB (dynamic microphone)
1-2
1-2
-50 dB
2-3
1-2
-40 dB (Electret microphone)
2-3
2-3
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