[Asterisk-Users] zaptel and low ring voltage

[Jim Van Meggelen]

asterisk-users-bounces at lists.digium.com wrote:
> Hi all,
> 
> Several months ago we built an * box with a quad-FXO tdm400p
> (REV e/f).
>> From the get-go, there has been a problem where occasionally
> (2-3 times
> a week) zaptel/* will not detect the ringing on a line.  (The
> call will ring through to telco voicemail).
> 
> The problem is not specific to a single line or FXO port on the
> tdm400p. 
> 
> I have 2 theories:
> 
> #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.


> #2 - the tdm400p card is bad
> 
> Assuming #1, can the zaptel driver be tweaked to be more sensitive to
> ringing? 
> 
> Any other ideas or experiences?
> 
> Running asterisk/zaptel v1.0.2
> 
> Thank you,
> 
> 
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