> >***** Moderator's Note *****
> >
> >Good point: of course, TDM switches need a very accurate _timing
> >source_, but that's a separate issue. Verizon timing is mostly
> dervied
> >from GPS these days, and I assume other ILECs are using it too. > >
> >The question, though, is if the _time of day_ settings in the COs are
> >being derived from a common source, or if they're still being set > >locally.
>
> Why wouldn't they have a routine to automatically convert the GPS UTC > to
> local time?
>
> Also, using GPS, the switch always knows where it is. ;-)
>
>
> ***** Moderator's Note *****
>
> I don't know if they do, but _if_ they do, it would probably be from a
> different source than the GPS or Stratum 1/2 clocks that provide
> digital pulse timing. The software inside the switches is proprietary
> to the vendors, and I'm asking if it was ever modified to use GPS or
> other time references.
>
> Bill Horne
> Temporary Moderator
BITS reference carries nothing more than an accurate synchronization signal, generally delivered as an AMI T1 (that part is definitely standard). There's a SSM that can be delivered on that T1 that allows nothing more advanced than "I'm out of sync, don't use me as a source", or "I am in sync, go ahead".
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In short, think switch and network timing to be more of a metronome than a clock. The metronome tells you the beat, but doesn't tell you the song, or where in the song you are.
For the record, I've been told by reliable sources that the audiochron unit in Detroit, before it was decommissioned, was occasionally synchronized to the CO tech's watch, as the WWV reciever had been broken for years.
-Paul