Sun Mar 22 18:23:17 UTC 1987
I am unaware of any master clock in AT&T used for sync. I do know
that it's quite common for the clock in each central office to run
at a significantly different rate. The symptom of this is that when
you dial 1200 baud from one CO to another, you get a burst of noise
on a regular basis - the frequency depends on how close the clocks are.
Each time it slips one full tick, there's a phase shift, and with
212 protocol a phase shift turns into a garble. The problem occurs
with the newer ESS switches.
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