[Asterisk-Users] sidetone noticeably loud on analog handsets on T100P

[john lawler]

Hi guys,

I've run into a problem that I can't figure out on a bunch of handsets I 
have running into a Rhino Equipment 24-port FXS channel bank hooked up 
to a T100P and running asterisk-0.9.0 and the associated stable Zaptel 
release.

The sidetone (your own voice that you hear in your handset, built in for 
comfort) is noticeably louder than it should be, and it doesn't seem to 
make any difference if I adjust the rx/txgain in zapata.conf (on either 
the inside Zap channels [handsets] or the external [POTS lines] ones 
(which are routed through another channel bank [Carrier Access AB I] and 
a separate T100P card).  What's also strange is that when I place a call 
from inside, the callee hears my voice fine and I can hear their voice 
with very little difficulty, but the my own sidetone is always too loud.

We've got regular analog handsets running into the Rhino channel bank 
and they seem to work fine for everything else, we've experimented with 
volume controls on the handsets themselves as well as on some 
Plantronics headsets that are plugged into them (but have also of course 
tested this scenario without the headsets for isolation).  The analog 
phones are known good by themselves and do not exhibit this behavior 
when directly plugged into a POTS line.

Has anyone experienced this?  I did some googling on it through the 
archives of course, but don't see much discussion of sidetone issues 
with analog handsets.

I'm wondering if there's some way I could be adjusting the sidetone in 
Asterisk or should I be looking at my FXS channel bank?

Thanks,

John Lawler