psb21391 Infineon Technologies Corporation, psb21391 Datasheet - Page 144

• Manufacturer Part Number: psb21391
• Description: Siemens Codec With Upn Transceiver
• Manufacturer: Infineon Technologies Corporation

Data Sheet
For reasons of physiological acceptance the AGCX gain is automatically reduced in case
of continuous background noise e.g. by ventilators. The reduction is programmed via the
NOlSX-parameter. When the noise level increases the threshold determined by NOISX,
the amplification will be reduced by the same amount the noise level is above the
threshold.
A programmable Loudness Gain Adjustment stage (LGAX) offers the possibility to
amplify the transmit signal after the speech detector SDX. If a lower signal range in front
of the SDX is necessary to determine between speech and echo a part of the transmit
signal amplification can be transferred to the LGAX. It is enabled with the bit GCR.SP.
Note: Even if the AGCX is disabled in speakerphone mode the LGAX remains enabled.
If the speakerphone is in receive mode, the AGCX is not working; instead the last gain
setting is used and regulation starts with this value as soon as the speakerphone returns
into transmit mode again. For transmission measurements with this transient behavior it
is recommended not to use a continuous sine wave signals but some kind of synthetic
speech (e.g. switched noise or Composite Source Signal CSS). The sweep range of the
switchable attenuation ATT (see chapter 4.4.1) is affected by the AGCX.
If the automatic gain control enlarges the signal level, the sweep range will be increased
accordingly in order to obtain a constant over-all gain in transmit and receive direction
(constant TCL, constant echo return loss).
The initial gain (AGIX) is used immediately after enabling the AGCX to allow a fast
settling time of the AGC.
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PSB 21391
PSB 21393
2001-03-07
Codec