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From: paul@kuhub.cc.ukans.edu
Newsgroups: comp.protocols.time.ntp
Subject: Potential time sync in the home
Message-ID: <1991Apr5.121745.29484@kuhub.cc.ukans.edu>
Date: 5 Apr 91 12:17:45 CST
Organization: University of Kansas Academic Computing Services
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Newsgroups: rec.video
Subject: Setting Clocks
Message-ID: <9104021909.AA17060@cwns1.INS.CWRU.Edu>
From: ac365@cleveland.Freenet.Edu (Todd Donovan)
Date: 2 Apr 91 19:09:30 GMT
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>Or, better yet:
>
>	Have the television networks send out the time of day in addition
>	to the signals currently sent out during the vertical blanking
>	interval.  (The current signals include information for fine
>	tuning the color, and close captioning.)  Of course, this will
>	not help devices that do not have a TV tuner, such as alarm clocks.
>

I know that NBC already does send out the time of day during the
vertical blanking, and I have to believe that the other networks also
provide this information. Keep in mind that each part of the country
is on a slightly different power frequency and this will cause 
cummulative errors in clocks. This and the fact that cheaper clocks tend
to easily get off, caused NBC to implement a "network clock" so that all
affiliates had exactly the same time. Since the human factor in master
control of most stations is being eliminated, and automation
introduced, there is no one to simply look at network feeds and know
what should be on the air. Since the television day is broken
down to the second, there is no room for slippage when local stations
insert commericals or simply just link-up with the network. Thus the
need for over 200 syncronized clocks...updated each second.

As of yet, I know of no easy way for the home user to decode these
signals and use them for the setting of clocks. 



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