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Re: [OM] OM-1/2 VSOE ?

Subject: Re: [OM] OM-1/2 VSOE ?
From: Jay Maynard <jmaynard@xxxxxxxxxxx>
Date: Sat, 18 Dec 1999 08:40:35 -0600
On Sat, Dec 18, 1999 at 08:14:32AM -0500, Chuck Norcutt wrote:
> I would hope so.  Remember older television sets with their horizontal
> and vertical hold controls?  I haven't seen (or needed) such controls
> for a very long time.  I assume that modern resistors and capacitors
> still age and change value like their predecessors so it must be
> possible to build circuits that are somehow self compensating.  Perhaps
> one of our EE listees will enlighten us.

Well, I'm no EE, but I'll take a shot at it...

The point of vetical and horizontal hold controls in a TV is to make the
set's scan rates match those of the incoming signal. Newer sets (and not all
that new, either) use a circuit called a phase locked loop to perform this
function. The PLL has the ability to adjust itself to match an input signal,
and track changes in it. Changes in component values can affect the range of
frequencies the PLL can lock to, but not usually so much as to keep it from
working.

This kind of thing doesn't help when there's no known input to compare
against, unfortunately.

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