Selective Gain Reduction, "Ducking - Tech Works CI Series System Planning Manual

The "ALERT" is a selectable sum (OR) of several keying signals options
The Monitor Audio may always be present, or may be Keyed
Keyed Audio is useful for Simple Logging/Monitor Devices, Audio is only present when desired
The PA-BUSS, ALERT Signal may be configured to interrupt the "Music" when it's appropriate
For example, when the Microphone is active, to avoid music bleeding into the microphone
Feedback Prevention:
Selective Gain Reduction, "Ducking" is used to determine how much to turn down the sound.
Many intercommunications systems require full Duplex Operation. That is, several users may be listening
and talking at the same time. This introduces many acoustic feedback paths
When a user enables their microphone, the PA-BUSS, Monitor Speaker may have its output reduced
Thus lowering the around the loop feedback gain, and Reducing Feedback
Example: To appreciate the concept, consider the PA-BUSS Output of the MSI-22
ALWAYS
CI-BUSS ALERT
TALK SW
PA-BUSS IN ALERT
ALC (MIC)
PA-BUSS INPUT
MASTER INPUT
SLAVE INPUT
TALK SW
CI-BUSS ALERT
This is even simplified; "Ducking", Feedback Suppression, also has configuration Jumpers!!!
10/29/2019 Tech Works CI-Series Systems Planning & Installation Manual
LOGIC
KEYING
SOURCES
AMP
"LISTEN
LEVEL"
NONE
LOW
MED
MUTE
DUCK
OR
SUM
"LISTEN DUCK
LEVEL"
PA-BUSS INPUT AUDIO
(+)
ALERT
OR
PAIR
(-)
AMP
ALWAYS
SELECT
MUX MUX
ALERT
PA-BUSS
OUTPUT
AMP AUDIO
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