[NJARC] Video Disc Player

[David R Sica]

On Tue, 3 Jan 2006 21:08:07 -0500 (GMT-05:00) Nick Senker
<ns539 at earthlink.net> writes:
> _______________________________________________
> I came across and old (1970?) video disc player and some RCA discs.  
> These appear to be an enclosed cartidge type (12") which slide into the
player.  
> I guess this was a foreunner to todays DVDs.  I remember seeing
something 
> called 'Laser Discs' for sale long ago but they were not encased in a
rigid cover 
> like the ones I have.
> I'm curious about the laser technology (?)  used to read/play the 
> discs (were diode lasers availble then?) and also about the RCA
technology/involvment 
> (ALex?).  Are these of any particular interest to anyone?
> Any comments would be of interest.  Nick Senker

Nick,

What you have is almost undoubtedly a CED (Capacitence Electronic Disk)
system video player. Lots of info at
http://www.cedmagic.com/selectavision.html. I think Alex has a prototype
stashed in the back room, which I've been hoping to find out a little
more about.

The CED was to a laser disc what the Edison cylinder player is to an
audio CD. (Well, not quite, but close!)  In one way it's not unlike the
old Edison vertical cut phonograph system. 
It uses a "needle" (capacitance pickup) in a "groove" to play the video,
but it doesn't physically track the signal in the way a phonograph stylus
physically is moved by the grooves to generate an electrical analog of
the music. The pickup does physically track the groove, but it reads the
signal as a difference in capacitance as the pickup ends up closer or
farther away to the surface becuase of the peaks and valleys embossed in
the vertically modulated groove.

That about exhausts my technical understanding of the system. I have a
couple of these players and a bunch of discs; they're still in the
"highly unwanted" category, kinda like 78 rpm records were in the
sixties, but I fell in love with them since they already seemed amusingly
(and amazingly) retro for something as recent as the ninteen-eighties!

--Dave