Polycom SoundStructure C16 Design Manual page 45

The SoundStructure telephony cards have been designed to meet various regional telephony requirements
through the selection of a country code from the user interface. For each telephony interface card, the signal
processing is listed in the following table and shown in the following figure.
The telephony transmit path includes dynamics processing, 10 bands of parametric equalization, up to 1000
milliseconds of delay, a fader with gain control from +20 to -100 dB, and a line echo canceller. There is also
a tone generator that is used to create DTMF digits and other call progress tones that may be sent to the
telephone line and also played into the local room.
SoundStructure SR-Series Telco Processing
Telco Processing
Line echo cancellation, 80-3300Hz, 32msec tail-time
Dynamics processing: gate, expander, compressor, limiter, peak limiter on telco
transmit and receive
Up to 8th order highpass and lowpass filters
1st or 2nd order high shelf and low shelf filters
10-bands of parametric equalization on telco transmit and receive
Call progress detection
Signal fader gain: +20 to -100 dB
Automatic gain control: +15 to -15dB on telco receive
Signal delay on telco transmit and receive: up to 1000 msec
Noise cancellation: 0-20dB noise reduction on telco receive
On the telephony receive path, the processing includes up to 20 dB of noise cancellation, automatic gain
control, dynamics processing, 10-band parametric equalization, fader, and audio delay. In addition there is
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