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From: 9212mhm@hou2a.UUCP (M.MORTENSEN)
Newsgroups: net.dcom
Subject: Re: post-Bell System DDS clocking
Message-ID: <518@hou2a.UUCP>
Date: Fri, 22-Mar-85 16:49:47 EST
Article-I.D.: hou2a.518
Posted: Fri Mar 22 16:49:47 1985
Date-Received: Sat, 23-Mar-85 03:38:46 EST
References: <842@amdcad.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 15

Yes, there is a currently a single source for clocking in
the country.  The old BSRF (formerly Bell System Reference
Frequency, now called the Basic Service Reference Frequency,
or some such) is still working.  The Local Exchange Carriers
do indeed take their DDS timing from the AT&T-C network,
both for DDS as well as for digital facilities and digital
switches.  I have heard that some other interexchange
carrier(s) may in the future be setting up their own
reference sources.  In that case, we will have a number of
networks that are plesiochronous.  Will it cause problems?
It depends on how good the reference clocks are, whether the
networks really worry about inadvertent timing loops, etc.
			Mark Mortensen
			AT&T-Bell Laboratories HR