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From: Mills@udel.edu
Newsgroups: comp.protocols.time.ntp
Subject: Re:  Potential time sync in the home
Message-ID: <9104052140.aa16435@huey.udel.edu>
Date: 6 Apr 91 02:40:04 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: inet
Organization: The Internet
Lines: 42

Todd,

Darn, another station heard from. Do we get to send news briefs via SMTP now?
Have you a suggested MIB for your station equipment? As a former engineer and
combo man for a motley crew of radio and tv stations in and around Ann Arbor
and Detroit, things must have changed a lot over the last twenty years. And
still the network programs start one second late, which the affiliates try
to fill with expanding promos...

First, I don't know where NBS gets the time. At the Detriot NBC affilitate
(call letters used to be WWJ) the time came down the wire (remeber the
bing-bing-bong?) and then the buttons got pushed. [we all studio buzzards
were hams, so our intercom was a Morse key and buzzer - worked great]. The
reason it was done that way was that the Western Union clock clunkers 
introduced their time corrections just before or on the hour, which led
to a clear violation of the Principle of Least Astonishment.

On your comment on mains frequency. For all of the US except Texas and
west of the Rockies, the mains are synchronized to the same frequency
and phase, as established by a WWVB receiver somewhere in Ohio. Texas
has their own system established I am told by reason of oil depletion
allowance regulations or some similar silly reason. West of the Rockies
frequency control is closed-loop and maintained automatically. On
our side the loop is apparently closed only in paw-to-knob mode. I don't
know if your reference to frequency implies you genlock to local power,
which means you could have up to a frame-jitter (do the even and odd
fields have individual timestamps (gawd)?) from true tick.

You can, of course, readily detect the timecode using a delayed-sweep
display on an oscilloscope, but, while I have not looked in a while,
the resolution of the code does not appear to be much better than 
a second anyway.

Having said all this, and aware that all three tv networks have rubidium
standard in New York which where once upon a time proposed as a ubiquitous
dissemination method for NBS time (genlock and local frame storage killed
that idea), independent WTTG in Washington still ticks the atomic second
and USNO still publishes their offsets weekly (weakly?). That's in fact
very useful if you want nanosecond time and you happen to live within
the coverage area.

Dave