[Asterisk-Dev] Zap gain changing patch

[Denis Smirnov]

When I set rxgain/txgain to very small, then calls from PRI to PRI very
silent (users complain).

When I set txgain/txgain to bigger values, users hear echo when call from
SIP to PRI.

I want to set different gain levels when call from PRI to PRI, and for
other calls.

How I can do it?

What function called when trying to calling, and has information about:
 - rxgain/txgain levels in config
 - is connected channels PRI-interfaces
and has access to functions for setting gain levels
?