[Asterisk-Users] zaptel and low ring voltage

[Ryan Courtnage]

On Thu, 2004-02-12 at 06:55 -0600, Rich Adamson wrote:
> > > #1 - the ring voltage for some calls is below acceptable levels
> > 
> > Possible, but also possible that there is too much loss on the circuit.
> > 
> > You can test the ringing voltage with a meter, it needs to be between
> > 90V and 110V.
> > 
> > Beyond that you may need to use a transmission test set (such as a
> > Wilcom T136B). I got mine for $20 bucks on eBay. Using a butt set and
> > the test set you'll need to call a 1004Hz source from TELUS and then
> > check that you're within the following specs:
> > Loop mA:		23 or better (too hot is no good either, but I
> > doubt that's your problem)
> > Circuit loss:	between 0 and -8dB. 0 is really too hot, -3 to -6 is
> > nominal, -8.5 is pushing it, but still within spec.
>  
> Not likely the above is the root-cause as that implies the pstn line
> is 'changing' characteristics on almost a daily basis (highly
> unlikely). Also, the spec's for the 3050 chip (on the tdm fxo module) 
> indicates it will detect ringing voltage down to 40v (or lower on some 
> some specific configurations).


I wasn't aware of this spec.  If this is the case, then looking for
zaptel tweaks or even circuit loss may prove to be fruitless.


> If you search through the archives you'll see others have also had
> issues with the tdm using fxo modules. Lots of references relative
> to stop/restart asterisk, unload/reload wctdm & zaptel, reboots, 
> hear nothing but white noise, can only reload zaptel so many times
> before a machine reboot is necessary, etc. Seems there has been
> (maybe still are) issues that are driver related, kernel related,
> and/or possibly distro related.


I've deployed several of these cards, and have done my fair share of
griping about them (on the alias) in the past.  From experience in these
cases, when the card/module stops 'working', it will not service any
incoming/outgoing calls until module reload.  This is not at all the
case with this current implementation.
  
Thanks
Ryan