From: bill@bilver.uucp (Bill Vermillion)
Subject: Re: Seeking info on a 10 year old video disk player
Organization: W. J. Vermillion - Winter Park, FL
Distribution: usa
Date: Fri, 11 Sep 1992 03:18:07 GMT

In article <4032@vidiot.UUCP> brown@vidiot.UUCP (Vidiot) writes:
>In article <1992Sep8.153900.28030@bilver.uucp> bill@bilver.uucp (Bill Vermillion) writes:

>[long article deleted]
>
><And boy am I glad that NEVER happened.  I own a pair of CED players,
><and have many disks, but when the last of my favorites appears on LD,
><I'll put the machine on a shelf as a museum piece - and remember that I
><really enjoyed it for things it gave me.

>Thanks for the info.  Much appreciated.  Until now, I'be only heard really
>bad things about the CED units.  To me, anything that uses a needle instead
>of a laser is asking for trouble.  I know the "needle" is different than a

The 'needle' concept in the CED, and JVC's capacitance system VHD
really took a drumming from the laser crowd.  "Needlevision" was one
name.

But actually the concept was good.  And the needle didn't wear
significantly because it was not used to pickup information the same
was a phonograph record does.

The signals were actually pits beneath the grooves and the changes in
capacitance were what chreated the signal.

RCA's concept was similar to that used in the linear tracking
turntables.  The groove was used only to guide the pickup, and did not
contain the information, the area under the groove did that.

The needle would engaged the groove - the rotation of the disk, 450
rpm, would force the pickup away from a true tangential position. This
would be sensed and the pickup carrying arm would be moved into a
tangential position.

This eliminated a servo control mechanism such as in the LD system.

JVC's capacitance system used two embeded capacitance track beneath the
surface of a smooth disk.  Their pickup was more of a 'sled' design.
One track carried the signal and the other carried a servo control
track.

LD's position themselves by keeping over the center of the pits.

The JVC got one hour on a 10" disk of vinyl based material.  It was a 4
channel design.   And the channels could be audio or video.   One demo
I saw had three channels of audio and one of video.  If used in a
multi-media presentation format you could have 3 video channels and one
audio.

Capacitance systems advantages were not using laser circuitry which was
more expensive at that time, and in those days it was mostly gas tube
lasers, not the solid state units we have today.

Mechanical devices can define a much smaller area than the commercial
solid state lasers so that was an additional plus.

RCA had the technology to put between 3 and 4 hour per side on a disk.
JVC got one hour on a 10 inch disk, and going to 12 inches would
probably have gotten them 3 hours.

As I said in the earlier article I am glad the RCA didn't survive
because of the limited resolution.  The VHD did get use in educational
circles in Japan, from what I have heard.

The LD, as we know it today, is the survivor of the SIX different video
disk processes that were developed, if you consider the first one to be
Baird's device for recording and playing back the original circular
scanning devices in the late 1920's.

The Teldec system made it to production as a video jukebox.  They were
just about 10 years to early considering the state of music video
today.  I guess that happens to too many of the pioneers, a great idea,
but just too early to be successful.

The Thompson-CSF units were laser units too, but they were transmissive
units, and not reflective.  You just refocused the laser to read the
other side.   I don't think these were ever used in a video environment
however, and were being pushed for WORM data storage.    You could
access twice the amount of data as a conventional reflective device
because you could read through the disk.

Thomson just gave up on that about 2 years ago.  The only one I saw was
about 4 or 5 years ago, and I think I still may have some literature
stashed away on that in one of numerous file boxes.

The history of audio/visual media is fascinating with all the different
approaches that have been tried over the years.  I even saw a 'jukebox'
for cylinder records once.  Held 6 cylinders.  And locally I have seen
a 'music box' that holds several disks.

I felt I had to comment on the CED because as time goes on history
tends to get changed by people passing on legends/rumors/??.   

-- 
Bill Vermillion - bill@bilver.oau.org  bill.vermillion@oau.org
                - bill@bilver.uucp 
                - ..!{peora|ge-dab|tous|tarpit}!bilver!bill