12" Floppy Disks

[Paul Koning]

> 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