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From: fish@ihlpa.UUCP
Newsgroups: sci.electronics,misc.consumers
Subject: Re: info on clocks using battery backups
Message-ID: <4323@ihlpa.ATT.COM>
Date: Fri, 19-Jun-87 17:22:23 EDT
Article-I.D.: ihlpa.4323
Posted: Fri Jun 19 17:22:23 1987
Date-Received: Fri, 26-Jun-87 01:53:32 EDT
References: <3622@cisunx.UUCP>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 17
Xref: utgpu sci.electronics:754 misc.consumers:1819
Summary: Battery backups not accurate

In article <3622@cisunx.UUCP>, nf165636@cisunx.UUCP writes:
> 
> How do the clocks (and clock radios) that run on main power (110/60 Hz)
> count the time ? Especially those that use battery backups. In this case
> do they use a quartz crystal ? Does that mean that these can be used
> on 110/50 Hz or any other frequency ? Any info will be appreciated.

Most cheap digital clocks and clock radios with battery backup use the
line frequency as a primary time base, and have an internal oscillator
as the backup.  The oscillator is not crystal-controlled, and will drift
considerably, causing the clock to lose or gain several minutes in a day.
However, they are usually accurate enough to maintain the correct time
during brief power outages.
-- 
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/  \				Bob Fishell
\__/				ihnp4!ihlpa!fish