[asterisk-users] Obtaining high voice quality in dahdi channel

[jg]

Asterisk uses "echo cancellation" to enhance audio. EC can be done in 
soft- or hardware. All major card manufacturers have variants of their 
cards with hardware echo cancellation support. Searching the internet 
gives a lot of information about this topic.

If you install a Sangoma card without HWEC, then you do get the default 
software canceler. Depending on your needs, switching to the OSLEC 
canceler might or might not be a better choice. Generally, a card with 
HWEC gives the best results, especially when you also have a lot of 
facsimile messages.

jg