[asterisk-users] TDM analog cards, volume, echo, fxotune, ztmonitor and HPEC

[Stephen Bosch]

Hi:

Tzafrir Cohen wrote:
> Just a partial answer:
> 
> On Sat, Mar 24, 2007 at 10:24:18AM -0600, Stephen Bosch wrote:
>> Hi, everyone:
<snip>
>> Now, standard analog sets have a varistor circuit to compensate for
>> these variations in signal level, but it would appear that the TDM cards
>> don't incorporate this kind of dynamic gain control.
>>
>> Zaptel allows you to control the transmit and receive gain at the
>> interface card, but isn't that what fxotune is supposed to do? Tune
>> those gains so that the echo is minimized? I don't want to play with
>> gain only to undo the echo tuning done by fxotune.
> 
> No, this is not Zaptel. This is Asterisk's chan_zap (Asterisk zaptel
> channel). 

Gain can be *set* in zapata.conf -- but aren't those adjustments made at
the driver level?

> fxotune, however, runs directly with zaptel. Thus it cannot be affected
> by whatever gain settings you have in zapata.conf.

Doesn't fxotune make gain adjustments? If gain adjustments are part of
the echo optimization process, then wouldn't changing the gain levels in
zapata.conf impact echo and undo part of what fxotune has set?

>> Similarly with ztmonitor: Is tinkering with the gain using ztmonitor
>> going to undo the tuning done by fxotune, or can I do both?
> 
> tinkering with the gain with ztmonitor?

Well, using ztmonitor to measure signal levels and adjusting gain
accordingly. The directions for this process may be found at

http://lists.digium.com/pipermail/asterisk-users/2004-November/064312.html

Now, this post is more than two years old, and I think it precedes the
changes made to fxotune; I don't know of many people using it to deal
with echo -- but my echo is okay, I need to adjust the gain now.

(There's another post dealing with gain and ztmonitor here:

http://lists.digium.com/pipermail/asterisk-users/2005-March/089437.html

)

-Stephen-