[Asterisk-Users] Poor pstn line quality

[Tom]

Thanks for your help Rich,
I think it was a combination of poor line quality and shared IRQs and a couple
setup mistakes (oops), we set busydetect=no in zapata.conf (it wasn't there
before), and that seemed to clear up the 1 ring problem, then we got the fxo
card on its own IRQ, and that cleared up the dropped call problem, the call
quality is still lacking, (lots of static as I said thats just on the line) but
we fixed the drop call problems, and the funny incoming call problem.. So they
now have a working system that sounds the same as their old analog phone
solution, so good job on your diagnosis!  I had heard of the shared IRQs
causing bad quality (popping, etc), but not dropped calls as I saw here.
Thanks again!
Tom

Quoting Rich Adamson <radamson at routers.com>:

> > 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)
>
> >From your description, it sounds more like a shared interrupt problem
> (cat /proc/interrupts) then it does a pstn line problem.
>
> If it really is a pstn line problem, then plug the line into a ordinary
> analog phone set and listen. If the pstn line is bad, you'll hear
> the same noise on the analog set.
>
>
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