[ntp:questions] offline machines' time synchronization

David J Taylor david-taylor at blueyonder.co.uk.invalid
Fri May 25 05:44:42 UTC 2012

"Dave Hart" <hart at ntp.org> wrote in message 
news:CAMbSiYBLnxaj_x4vch3eNDqwUDX+d5sGcHyr8zBe3Jh0C2K=yg at mail.gmail.com...
> On Thu, May 24, 2012 at 4:24 PM, Chris Albertson
> <albertson.chris at gmail.com> wrote:
>> Lots of good discussion here but I found an easy way to stay "on-time"
>> while the Internet is down and GPS is not available.  There are some
>> people on eBay selling Rubinium oscillators for about $40.  They have
>> a pulse per second output.    These Rb clocks will keep NTP within
>> reasonable specs for a LONG time.  It does required some effort to set
>> up.  Just wanted to point out one more option.
> ntpd requires reference clocks provide time, not just frequency.  How
> do you discipline the Rb PPS to occur at the top of the UTC second (or
> a fixed offset from the top)?
> Cheers,
> Dave Hart

Agreed, Dave.  The way I read the message was for /temporary/ coverage, 
not a fully disconnected solution.  For US $40 (or somewhat more) you 
could easily get a secondary GPS reference such as:

  Trimble Resolution SMT Timing GPS OEM board
  eBay 290696970497  (price has gone up, though)

  Sure Electronics GPS evaluation board

  Garmin GPS 18x LVC

and use these to provide backup servers to cover the outage.


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