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Posted by JoeBloe on 01/05/07 13:31
On Fri, 05 Jan 2007 01:23:06 -0800, Tim Smith
<reply_in_group@mouse-potato.com> Gave us:
>In article <gparp2t4rbmfg2952ucgiqcq4853263cc5@4ax.com>,
> JoeBloe <joebloe@thebarattheendoftheuniverse.org> wrote:
>> >Too bad that the market didn't go for the "needle and groove" video
>> >disk that RCA tried to make work, eh?
>> >
>>
>> That's not what it was.
>>
>> It was a capacitive pick up stylus. No needle at all. No groove.
>>
>> http://en.wikipedia.org/wiki/SelectaVision
>
>From that page (underlining added):
>
>======
>SelectaVision used a special medium known as a Capacitance Electronic
>Disc (CED). The VideoDisc was a 12 in (305 mm) platter housed in a
>special caddy. The video and audio signal is stored on the Videodiscs
>via peaks and valleys in the grooves, similar but not exactly like a
> ==============
>phonograph record, of both sides of the discs. To play a Videodisc, you
>inserted the caddy into the player and the platter would be extracted.
>A keel-shaped needle with a titanium electrode layer would ride in the
> ================== ====
>groove with extremely light tracking force, reading the electrical
>======
>signal from the groove where it is decoded back into its FM state.
>
>Unlike a phonograph record, where physical movement (vibration) of the
>stylus in the groove of the platter led to an audio signal, the stylus
>in a SelectaVision player slid along the crests of the groove, at a
> ===================================
>constant rotational speed of 450 rpm. The varying undulations of the
>peaks and valleys in the groove provided differing amounts of
>capacitance between the stylus and the conductive carbon loaded PVC
>disc. This varying capacitance was measured by the player circuitry,
>providing an audio/video signal.
>======
You have proven that you can read, as well as cut and paste.
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