isd-t360sb ETC-unknow, isd-t360sb Datasheet - Page 48

• Manufacturer Part Number: isd-t360sb
• Manufacturer: ETC-unknow

ISD-T360SB
ECHO CANCELLATION
Echo cancellation is a technique used to improve
the performance of DTMF detection during
speech synthesis, tone generation, and OGM
playback. For echo cancellation to work properly,
HW AGC must not be active in parallel. Thus, to
take advantage of echo cancellation, the micro-
controller must control the HW AGC, if exists, (i.e.,
disable the HW AGC during PLAY, SYNTHESIS and
TONE_GENERATE states and enable it again after-
wards). If HW AGC can not be disabled, do not
use echo cancellation.
The microcontroller should use the CFG com-
mand to activate/deactivate echo cancellation.
NOTE
2.3.3
The VoiceDSP processor detects busy and dial
tones, constant energy level, and no-energy
2-12
Normally, a HW AGC is not required with
The ISD-T360SB, since SW AGC is optional
for the VCD algorithm, DTMF detection and
the speakerphone module.
0
–10
–20
–30
–40
TONE AND ENERGY DETECTION (CALL
PROGRESS)
0
Figure 2-1: Busy and Dial-Tone Band-Pass Filter Frequency Response
200
400
600
800
Frequency (Hz)
1000
(VOX). This enables call progress tracking. Detec-
tion is active throughout the operation of the
VoiceDSP processor. Detection can be config-
ured using the SDET (Set Detectors Mask) com-
mand, which controls the reporting of the
occurrence of tones, and the RDET (Reset Detec-
tors) command which resets the detectors. The
accuracy of the tone length, as reported by the
tone detectors, is ±10 ms.
TUNABLE PARAMETERS
Tunable parameters control the detection of busy
and dial tones, constant energy level (in the fre-
quency range 200–3400Hz), and no-energy.
These parameters should be tuned to fit the sys-
tem hardware. In addition, changes may be re-
quired to the tunable parameters according to
the setting (On or Off) of the HW Automatic Gain
Control (HW AGC), if exists. For more information
refer to Table 2-7 and Table 2-8 of the Command
Description section.
1200
1400
1600
Voice Solutions in Silicon
1800
2—SOFTWARE
2000
™