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Date:      Wed, 19 May 1999 23:02:44 +1200
From:      Joe Abley <jabley@clear.co.nz>
To:        Ladavac Marino <mladavac@metropolitan.at>
Cc:        Matthew Dillon <dillon@apollo.backplane.com>, Joe McGuckin <joe@monk.via.net>, hackers@FreeBSD.ORG, jabley@clear.co.nz
Subject:   Re: GPS receivers for xntpd (off-topic)
Message-ID:  <19990519230244.B133@clear.co.nz>
In-Reply-To: <55586E7391ACD211B9730000C1100276179609@r-lmh-wi-100.corpnet.at>; from Ladavac Marino on Wed, May 19, 1999 at 12:30:38PM %2B0200
References:  <55586E7391ACD211B9730000C1100276179609@r-lmh-wi-100.corpnet.at>

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On Wed, May 19, 1999 at 12:30:38PM +0200, Ladavac Marino wrote:
> 	[ML]  Back to my olden telco days some 10+ years ago when SDH
> was on paper only and ATM was on benches, this sounds like 2MHz H1*
> clock synchronized to GPS.  Since transmission does not need the time of
> day info (at least it did not need it last time I had any contact with
> it, ages ago), I don't think there is any time of day info in that clock
> output which would make this particular GPS receiver useless for NTP
> purposes.  Unless, of course, there is another output on the receiver
> which provides the time of day info as well.

I had kind of assumed the same thing; however, I was hoping I could
T off a feed from the GPS antenna to a new receiver with different
outputs, which we would purchase to provide time-of-day synchronisation
rather than 1/2000 second synchronisation.

It seems that there are a number of receivers that will do the job, but
people are mentioning async interfaces and ethernet interfaces, and I am
confused :)

More random off-topic questions: a GPS synchronised clock is stratum-2,
right? The caesium clock which provides synchronisation to the GPS is
stratum-1?

Sorry for the wasted bandwidth. Feel free to divert me privately to
a FAQ on this, rather than cluttering up -hackers (I looked but couldn't
find one).

> 	[ML]  * I think it's H1 I'm talking about: 30+2 channels of
> 64kbps.  European equivalent of T1.  Approx. 2MHz.

E1.


Joe



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