[Asterisk-Users] Qs about FXO/FXS cards

[Andrew Kohlsmith]

On January 1, 2005 06:24 pm, Steven Critchfield wrote:
> > 1.  Power alarms.  WTF does that mean?  Wish I had some support docs.
> >
> > 2.  On bootup, "Excessive leakage module x, ProSLIC failed Auto
> > Configuration".  Again, WTF?  Reboot and it's ok.  But, just a reboot
> > after driving 100+ miles to the client site is not a good option.
> >
> > 3.  On bootup, a LED won't light.  When zapata gets to it, it can't find
> > the channel.  Usually means a complete power cycle to get it to work.
>
> Those first 3 all sound like you have a problem with power supply and
> consistency. You don't mention what modules you have in the cards, but I
> bet you have FXS ports and have too light of a power supply for the
> job.

Everyone keeps coming back to this "light power supply" and I just do not buy 
it.  Period.  I'm sorry, Steven, but it's bullshit.  I'm speaking as an 
electronics design engineer and as someone who's been playing with this kind 
of stuff for the better part of a decade.  "light power supply" is like 
"irritable bowel syndrome" -- it's what you call the problem when you haven't 
been able to isolate the cause and the patient is demanding to know what's 
wrong with him.

Xeon 2.4GHz system, triple-redundant power supplies, Supermicro server 
motherboard, hot-swap everything.  +5 and +12V lines are within +/- 40mV of 
their target voltages, measured with a 100MHz DSO -- it is *not* a power 
issue.  P3-700 with 12 IDE drives in it, 350 or 450W (but decent make) power 
supply: Power quality is slightly lower but still what I would call 
acceptable.

I get the issue where two of the three FXS modules will be seen.  modprobe 
pauses for a good 5-6 seconds when the third module "disappears" -- 
unload/reload and it will find it, or not.  unload/reload until it finds all 
three and you're good to go.  

... Except that I can't receive faxes through it.  I can send them just fine 
(there are two different fax machines connected up to 2 of the 3 ports, and 
both exhibit the problem.) Use a T100P+Adit600 FXS channel bank and my fax 
rate (in and out) is 100%.  (this is IAX2 to a PRI connected to another 
system in the same location, btw, so it's not a FOIP issue.)  Unplug the 
T100P+channel bank and swap in TDM430P...  can't receive worth a shit, and 
that's all that's changed.  I'm using app_rxfax right now instead of 
Dial()'ing the fax machine on the TDM port, and my rx rate is 100%.  Weird, 
eh?

Perhaps *some* of the TDM issues are power issues but the more I read and 
experience with them on my own the more unlikely I think it is.  Truth be 
told there isn't a hell of a lot of power required to ring a goddamned phone.  
we're talking 20mA loops here and 85VAC.  There is something more insidious 
at work than just bad power.

-A.