[time-nuts] GPS Outage..

[Mark Spencer]

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 <kb8tq at n1k.org> wrote:
> 
> Hi
> 
>> On Feb 26, 2016, at 8:01 PM, Majdi S. Abbas <msa at 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
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