[Asterisk-Users] PSTN line quality

[Chris Mason (Lists)]

I'm looking for some input from someone with real experience of 
telephony. I am having problems with the sound quality on our PSTN line 
calls. Our channel banks are Adtran 600 and 750 and I spent a lot of 
time on the phone with Adtran trying to work out the problem.
We are getting hum and noise and very low volume on calls. I can 
increase the gain in zapata.conf but that increases the echo also.
I acquired a Line Test Set and talked to the telco about access to a 
MilliWatt generator. They did not have one active, but they worked on it 
and activated the MilliWatt Generator on the exchange for me.
I measured my lines and also the lines at another location I am having 
the same problem. The line levels were -20dbm at my office and -21.4dbm 
at the other location. My question is, how does this compare, what is 
the norm, and what is the recourse? Do I have the root of the problem or 
should the system be able to handle this loss of level?

-- 
Chris Mason