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.
