psb21381 Infineon Technologies Corporation, psb21381 Datasheet - Page 153

• Manufacturer Part Number: psb21381
• Description: Siemens Codec With S/t Transceiver
• Manufacturer: Infineon Technologies Corporation

Figure 82
Speech Comparator at the Line Side
The Gain of the Line Echo (GLE) directly corresponds to the echo return loss of the link.
Generally, it is specified to 27 dB. However, the worst case loss can be estimated to
10 dB. This means, the echo returns at least attenuated by 10 dB.
Similarly to the acoustic side, GDLE at the line side features the reserve above GLE
which is necessary to control the echo via the decrement PDLE. GDLE and PDLE are
interdependent. Exactly
must be at least GLE to prevent clipping.
Two pairs of coefficients are available: GDSLE/PDSLE while speech is detected and
GDNLE/PDNLE in case of noise. This offers the possibility to control separately the far-
end echo during speech and the near-end echo while noise is detected. However, this
requires an attenuation between the speech detectors SDX and SDR: If the SDX does
not recognize any speech, the SDR must not detect speech due to the far-end echo.
Note, that LIMX and LIMR are also influencing the sensitivity of the speech detection.
ETLE [ms] after the final speech detection the parameter sets are switched. If both sets
are equal, ETLE has no meaning.
Data Sheet
t
[ms] after the end of RX-speech the level enhancement VLE
143
PSB 21381/2
PSB 21383/4
2001-03-12
Codec