[Asterisk-Users] Poor pstn line quality

[Tom]

I just installed a new asterisk box with a wctdm with 4 FXO modules.  The lines
in the office have terrible static (using standard analog phones) and this
static can obviously be heard through the asterisk box on the sipura sip phones
we installed.  This by itself would not be a problem as the office is used to
and doesn't mind (I don't know how) the static.

However it appears that this really bad line quality is causing the fxo ports to
drop calls.  We tested all of the FXO ports in our office before we took the
box to install it, and it worked just fine... Here are the problems we are
seeing:

1) Incoming calls, although immediate=no is set in zapata.conf the caller hears
one ring, and then when asterisk starts the simple switch, the caller hears
static and dead air, as if asterisk had done an "answer()".  The caller doesn't
hear any more rings.  It takes asterisk about 3 seconds before it even rings
the internal sip phone, and then while the sip phone is ringing, until it is
answered the caller hears static and dead air. It seems as if the call has been
disconnected, or at least it will be very confusing for the customers of this
business, at any rate its unacceptable.

2) Outgoing and incoming calls: call quality is bad because of the static, but
randomly the zap channel that the call is on will hang up even though neither
side has hung up.  It seems like the poor line quality is somehow simulating a
"hangup" signal from the CO, and the fxo line is dropping the call.

has anyone seen poor line quality cause the digium fxo modules to have strange
errors such as these?

Thanks in advance for any replies/ideas/solutions (besides obviously calling the
phone company and telling them they suck)
Tom Christensen