[Asterisk-Users] Softphone vmail indicator and TDM400P woes

[Rich Adamson]

> 2) I have 2 TDM400Ps installed in a system. I need the audio on the
> analog phone (FXS modules) to be amplified somewhere between 10 and
> 15db so I set rxgain and txgain to 15 for the FXO interfaces and FXS
> interfaces. When a call comes in on the FXO at this setting, the call
> sometimes has about 20 seconds of loud noise that sounds like it might
> be music in the background. The problem is intermittent. Any ideas on
> how to solve this one? What settings should I use so that everything
> is at default gain (0.0) except the volume on the analog phone sounds
> louder? I'm guessing txgain=10.0 (or whatever value) on the FXS
> module?

Just a couple of comments on setting the gain controls....

You don't mention why you might need 10 or 15 db gain, but keep the
following in mind.
 - the gain settings for any fxo pstn connections are intended to 
   compensate for the loss associated with that connection, and should
   be set to allow pstn calls to hit your asterisk box as close as
   possible to 0 db. (0db is not realistic for analog pstn links
   via a TDM card with fxo modules, but get as close as possible.)
 - the gain settings for the fxs phone modules are intended to 
   compensate for the loss associated with the cabling going to the
   attached phone plus any losses associated with the phone itself.

Adjusting the fxs module gains to compensate for audio level problems
associated with fxo modules will very likely cause other level problems
(as you've probably already observed). The two module types (fxs and fxo) 
are totally indpendent and have nothing to do with the fact that both 
modules happen to be on the same TDM card.

There is no logical reason that I can think of where an fxs module
would need to be set at anything different then about 0 db.

If you don't know what the analog pstn cable loss is between your
asterisk box and the telco, then find that out _first_, and set the
fxo gains to about 2 db less then that loss. (Example: if that loss
is -8db, then set the rxgain & txgain to about 6db.) The specific
number will be a trade off between echo and being able to hear
normal voice.) Your telco technical folks _might_ be able to tell 
you what that loss happens to be if you don't have the skills or
tools to determine it for yourself. 

Once the fxo module gains are set to reasonable values, then muck
with the fxs gains to help improve volume.

If you don't follow the above, you will end up with one or more of
the following:
 - calls from a sip phone to an fxs phone (with high gain settings)
   will be too loud and/or distorted
 - calls from the pstn to your asterisk system that roll to voicemail
   will be difficult (or impossible) to hear from any phone
 - calls to/from any itsp from your fxs phone will be too loud
   and/or distorted

Think through the above before mucking with those gains. If the above
doesn't make a lot of sense, search through the hundreds of postings
that already exist on the topic and read more via the wiki.