[41339] in North American Network Operators' Group
Re: 220v/50hz power rig
daemon@ATHENA.MIT.EDU (Alex Bligh)
Thu Sep 6 14:55:07 2001
Date: Thu, 06 Sep 2001 19:49:31 +0100
From: Alex Bligh <alex@alex.org.uk>
Reply-To: Alex Bligh <alex@alex.org.uk>
To: Sean Donelan <sean@donelan.com>, alex@alex.org.uk
Cc: nanog@merit.edu, Alex Bligh <alex@alex.org.uk>
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--On Thursday, 06 September, 2001 10:47 AM -0700 Sean Donelan
<sean@donelan.com> wrote:
> Actually, its not being clever, its being cheap.
Some do both (or their spec sheets lie). I was about
to recommend a unit to Randy, until I downloaded the
PDF and thought 'how the hell do you set the frequency'.
Further investigation revealed something very like:
Input frequency: 47Hz-53Hz, or 57Hz-63Hz
Output frequency: 50Hz +/- 0.1%, 60Hz +/- 0.1%, autosensing
I guess that has a crystal with two dividers, a PLL,
and no obvious way to turn the autosense off.
Most units have some reasonably accurate oscillator
or it makes regenerating the output hard when there
is no input to sync to :-) Some good ones have a PLL to
minimize cutover disruption if you take the electronics
out of band.
--
Alex Bligh
Personal Capacity
