12" Floppy Disks
Paul Koning
paulkoning at comcast.net
Tue Sep 15 09:48:45 CDT 2015
> On Sep 15, 2015, at 4:39 AM, Adrian Graham <binarydinosaurs at gmail.com> wrote:
>
> Morning folks,
>
> I've been contacted by a teacher who's looking for any information about
> 12" floppies. Am I imagining that they really existed? I'm sure I've seen
> one or seen adverts for them, maybe at Bletchley Park. Others he's
> contacted think he's getting confused with 12" laser discs but I'm not so
> sure.
The PLATO IV terminals (the hardwired Magnavox ones, not the later microprocessor based ones) had an optional "Audio player". That used a floppy disk of about that size, storing analog audio snippets (in analog form, not digitized -- remember, this was around 1972). Seek was done by a pneumatic D/A converter, essentially. There were 128 tracks, each with 32 sectors.
Those disks had no sleeve -- you'd just slide the bare magnetic disk into the player mechanism.
paul
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