It doesn't help at all, since you are talking rubbish. Try to keep track
of the subject matter. We are discussing modems, where not slipping is
vital.
Regards,
Steve
Rich Adamson wrote:
It doesn't make any difference. The pcm data that arrives from the telco
is buffered in the zaptel and/or asterisk code, and sent out the second
T1 card as soon as it can. That buffering reduces (or eliminates) the
need to sync one T1 card to another. However, if the clock on the second
card were "way off" frequency, there could be a missed pcm frame from
time to time. The missed frame would not even be noticed by users in
most cases. (There was some discussion about how great of an impact
that really has several months ago. Personal opinion plus experience
says its a non-issue other then on some very extreme cases where a clock
is way off frequency. That tends not to happen with today's electronics.)
If you think about the variable delays that occur because of contention
for the pci bus, interrupt latency, etc, there are likely larger swings
in dropped packets resulting from that then there would be from multiple
T1 cards not having the exact same clock frequency.
The bigger issue with multiple T1's occurs with the Quad T1 cards, where
a single on-card clock is used with all four T1's. Syncing that clock
"to the pstn" is the only correct way (timing=1), making all other
downstream T1's (eg, channel banks, pbx's, other * boxes) subservant
to it (timing=0).
If you had multiple asterisk boxes located in several cities, and each
of those asterisk boxes had a pstn T1, then you better read and understand
T1 clock syncing very well as it will make a signifcant difference how
each box obtains clock sync since there is a potential for a circular
timing loop if one doesn't think that process through very carefully.
Hope that helps...
Rich
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