> On Sep 15, 2015, at 4:39 AM, Adrian Graham <binarydinosa...@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
