> On Jul 21, 2017, at 2:30 PM, Chuck Guzis via cctalk <cctalk@classiccmp.org>
> wrote:
>
> On 07/21/2017 10:37 AM, Adrian Graham via cctalk wrote:
>
>> I have a Facit9911 2 11/16” (or 70mm in new money) microfloppy drive with a
>> mahoosive interface module which google turns up precisely nothing about.
>> I’m pretty sure I’ve mentioned it here before but even a search of the
>> archive turns up nothing.
>>
>> See pic - http://www.binarydinosaurs.co.uk/facit9911MicroFloppy.jpg
>
> Even before flexible magnetic disks were used to record digital
> information, they found use in audio equipment. E.g. the Telefunken DT-600:
>
> http://vintage-technics.ru/Eng-Telefunken_600.htm
Interesting. Another example, slightly later, is the audio unit of the PLATO
IV terminal (1974 or thereabouts). It uses a rather large disk, perhaps 10
inches diameter, brown oxide, no grooves. It's a random access device, with
128 tracks. Each track has 32 sectors; a given audio clip can be up to 127
sectors long (though I'm not sure what happens if it's more than 32 sectors --
does it switch tracks? Seems unlikely).
The track seek is done with a binary encoded pneumatic cylinder assembly, 7
cylinders -- low order stroke is one track pitch, next is 2 tracks, next is 4
tracks, etc. So the binary track number would select 7 air valves which would
feed supplied "shop air" to one or the other side of each piston, moving the
read/write head to the correct track.
These terminals also had a back-protection setup for the plasma panels (the
"slide projector", actually more like a microfiche projector). Same sort of
setup, but with X and Y both done by binary weighted sets of 4 air cylinders
each.
paul
