I'd be curious to know how many carriers have a reference source other than GPS for their "data line sync."
A few decades ago when I worked with long haul data circuits for a living the use of in non GPS timing references still seemed fairly common in my view. Yes I agree that some systems can run from "line timing" but a reference source is still needed some where. In my experience there was a common assumption made that the carriers had an accurate reference source for the timing that customers would pull "data line sync" from. Later when I entered the time nuts hobby I saw lots of ex Telecom timing gear for sale on the usual auction site. All the best Mark Spencer > On Feb 27, 2016, at 4:51 AM, Bob Camp <kb...@n1k.org> wrote: > > Hi > >> On Feb 26, 2016, at 8:01 PM, Majdi S. Abbas <m...@latt.net> wrote: >> >> On Fri, Feb 26, 2016 at 05:56:59PM -0500, Bob Camp wrote: >>> Cell phones since they first came out have *never ever* been setup >>> to run on anything other than GPS. Retrofitting them to use something >>> else would take a decade or more. We didn’t “destroy the backup”, there >>> never was one. Pretty much all of our surplus gizmos are cell tower >>> surplus (like 99.99%). >> >> Bob, >> >> It depends. >> >> We're used to thinking of those GPS and oscillator packages >> as the only timing for a cell site, but that was not the case until >> fairly recently. >> >> In many of those sites, there was also transport gear that >> would take line timing from a CO or other site upstream that >> typically had diverse reference clocks available. It might even >> have provided a backup BITS T1 as a frequency reference to cell >> equipment. >> >> Even without a local transport node, prior to the last few >> years (where things seem to be going Ethernet), most cellular equipment >> was still taking TDM handoffs, and could revert to taking line timing >> off its transport circuits, thereby indirectly getting it from >> practically anything upstream if its local reference failed. > > Again, the context of the question is an external to the system timing > source. In other words Loran-C or something similar. Even today, the network > sync to the backbone does not come from the GPS. That comes from the > carrier’s data line sync. > > Bob > > >> >> Certainly, the surplus device pool is all GPS, but that's >> because of the number of additional devices deployed, not necessarily >> representative of the full footprint of LORAN and other methods that >> used to be available as indirect backup references for the sites. >> >> Of course, that's not going to be an option going forwards. >> I, for one, welcome our new Ethernet overlords. >> >> --msa >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.