[Asterisk-Users] WCTDM-24xxp woes

[Rich Adamson]

Andrew D Kirch wrote:
> I am currently running Asterisk 1.2.8, on an AMD Sempron 3100+ (ASUS K8N
> Nforce based board).  I am using a Digium wctdm24xxp to terminate 8 (2x
> quad) FXO lines.  Using ztmonitor (From zapata) I cannot see that there is
> any registerable incoming volume from these lines.  I've been running them
> at rxgain = 25 (zapata.conf) to make the audio audible, however this
> creates poor call quality issues (static and distortion) on most calls,
> and audio garble in voicemails.   Fxotune fails for every line with "Could
> not fill input buffer"
> I've tried changing PCI slots, played with echo settings, and done
> everything else I can think of to make this card play nice to no avial.
> 
> Anyone with solutions or ideas, your input will be greatfully appreciated.

As others have already noted, start with rxgain & txgain set to 0. And, 
check the lines with an analog phone to ensure you don't have weak audio 
from the pstn line to start with.

If you do have weak audio (as in a very long pstn line), you're not 
likely to get the TDM400 or TDM2400 card to compensate for the loss 
without seriously impacting the s/w echo canceler.

For high loss pstn lines, ztmonitor will not provide any useful indication.

If you approach the problem from a professional perspective, you would 
use a transmission test set to measure the loss of the pstn line by 
dialing into the central office milliwatt generator (no asterisk 
involvement). If that measured pstn loss is anything greater then about 
7db to 10db, I'd contact your pstn provider to see if there is anything 
they can do to improve it. (Most US telco's can install repeaters in the 
central office that will boast the audio levels. Repeaters have been in 
use by telco's for at least 20 years, and are typically used on long 
rural pstn lines.)

If the analog audio is reasonable (or your measured pstn loss is less 
then about 7db), then you've got something wrong with the TDM2400 
installation. That "could" be something like a mis-wired TDM2400-to-pstn 
line connections, etc. It will have nothing at all to do with the pci 
bus, interrupts, etc.