[QuadList] Servo Modes

[sgw1009]

This is somewhat reminiscent of the AVR-1 and its startup procedure.  When
rolled, the AVR-1 would near-instantly start playing the tape at full speed
(possible because of its vacuum columns and low-inertia pancake capstan
motor).  During this brief period it would look for a reference pulse from
the tape.  Once it retrieved a reference pulse from the playing tape, it
would then know how far ahead or behind the tape was from house reference.
It would then (generally) accelerate the tape the amount (and duration)
needed to make the next reference pulse coincident with house reference.
The wide-window TBC took care of the rest.  This resulted in virtually an
instant roll, although in reality it was about 2 to 3 frames.  This was not
noticeable or objectionable (to the home viewer) during normal program
content, but you could hear the servo working to align the tape reference
with house reference when rolling a tape containing bars and tone.  That is
to say you would hear normal tone, followed briefly by tone that was an
octave higher (sync phase), followed again by normal tone.  Pretty amazing
stuff !!

 

Steve Walton

 

  _____  

From: quadlist-bounces at quadvideotapegroup.com
[mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of Norman Hurst
Sent: Thursday, August 23, 2012 8:04 PM
To: Quad List
Subject: Re: [QuadList] Servo Modes

 

The Dischert invention was demoed to lock in less than 6 frames from the
time you pushed play.  That's 200 ms.  It was amazing.

 

The figure on the first page of the patent shows the acceleration profile
relative to house reference.  

 
<http://www.google.com/patents?id=K043AAAAEBAJ&printsec=abstract&zoom=4#v=on
epage&q&f=false>
http://www.google.com/patents?id=K043AAAAEBAJ&printsec=abstract&zoom=4#v=one
page&q&f=false

 

 

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