TELOS TWOX12 USER’S MANUAL
DETAILED CONFIGURATION & REFERENCE
CHAPTER 7 141
7.5.3 Duplex “Ducking” System
The ducking functions occur on both the send and caller audio. This function is
important for several reasons:
• Provides an “aesthetic” control over the caller that many programmers prefer.
When the announcer speaks, the caller is ducked, or reduced in volume
dynamically. This is particularly true when the caller is “carrying on” and the
programmer wishes to get a “word in edgewise” so the show can continue.
• Reduces feedback when a loudspeaker is necessary. Because the ducking
system operates on both audio paths, and because we designed it to be
symmetrical in its gain reduction action, the “feedback gain” is kept constant
and is reduced by the amount of the ducking level selected.
• In the loudspeaker case, reduces audibility of the caller signal that couples
through the acoustic path, into the microphones, and is returned the caller
resulting in a more natural sound for the caller.
The duplex system inserts a controlled loss (ducking) into whichever audio path
(send or receive) is not active at the moment. When the caller is speaking, this loss is
inserted in the announcer path, when the announcer is speaking the loss is inserted in
the caller gain is reduced. The effect is somewhat “seesaw-like” with the total loss
always being constant.
As a guideline, you will need a lower DuplexLevel setting when using open speakers.
This helps reduce the occurrence of feedback and also reduces the chances of the
caller hearing themself via the speaker to mic path which has an “unnatural” quality
and can be disturbing. In a “morning zoo” type of scenario the setting should be even
lower as there will be multiple mics used with open speakers. Fortunately, this
scenario coincides with a more duplex style of operating – where pre-recorded “bits”
may be played to callers and must be heard without interruption. The default setting
is 10.
You may choose how much of this effect you prefer, from HALF (0) which keeps
the system which makes the system operate like a “one way at a time” speakerphone
to FULL (16) which disables ducking. A typical value for many applications would
be in the range of 8-12.
7.5.4 Feedback Control
We’ve carefully designed the TWOx12 so that problems with feedback should be
rare. However, despite excellent trans-hybrid loss and a number of other features, you
can probably induce feedback if you try sufficiently hard (try cranking up your studio
monitors). Some suggestions for what you should do if feedback does occur follow:
• Adjust the DuplexLevel selection in the Audio Menu to a higher setting
• When mic processing is used, connect the hybrid in such a way that it gets an
unprocessed mic signal. Our Omnia ToolVox microphone processor has an
output just for this purpose.
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