User manual

Chapter 3: Configuration
channel = 5-8
Users of Digium's hardware echo cancellation module, the VPMOCT032,
should set the echocancel option to "yes." The module will automatically
configure itself to run at full capacity, 1024 taps (128ms), on each
channel.
Users without the VPMOCT032 using open source echo cancelers
included with DAHDI should configure echocancel to the values 128
(16ms) or 256 (32ms). Setting "yes" will default the option to 128 (16ms).
Users who have not purchased an 800 Series card with the hardware echo
cancellation module are encouraged to take advantage of Digium's High
Performance Echo Canceler software. This commercially licensed
software, which is made available at no charge to in-warranty Digium
analog interface card customers, provide toll quality echo cancellation,
performed on the host CPU, at up to 1024 taps (128ms) per channel. For
further details about HPEC, please refer to the Digium website here:
http://www.digium.com/en/products/software/hpec.php
When HPEC is enabled, users may set the value of the echocancel
parameter to any of the following values:
128 - 16ms
256 - 32ms
512 - 64ms
1024 - 128ms
Note: Higher values will result in dramatically increased CPU
consumption. In order to optimize system performance, users are
encouraged to choose the minimum value required to cancel their
echo.
Digium, Inc. Page 44