[vcf-midatlantic] talk at VCF-East on audio cassettes for data

Herb Johnson hjohnson at retrotechnology.info
Thu May 3 15:11:23 EDT 2018

I've agreed to give a casual talk at VCF-East, on the use of audio 
cassettes and recorders for program storage on first-generation (1970's) 
vintage computers. I'll describe how a "TTL logic gate" can create audio 
waveforms and interpret them, with little more than software and 
hardware. I'll try to point to early Altair/IMSAI class S-100 computers, 
early COSMAC (RCA 1802) computers, possibly others. I'll try to 
reference the earliest efforts to create various standards. And I'll 
point to current recovery work on some old cassettes.

I'll likely point to various Web pages for details and images - no 
PowerPoint presentations, no exciting videos. Maybe one wailing audio 
tape. Some stuff I won't know - I have an idea about that.

So why do this? There's recent and successful efforts, to recover 
programs today from COSMAC tapes 40 years old now - that's interesting. 
Many period micros are operated today, with MPEG music players acting as 
the audio source; so it's still in use that way. I mentioned the techie 
bits of cassette storage and retrieval - I'll draw some schematics. And 
unfortunately, experience with audio cassettes is becoming "lost" - a 
generation of young adults have NEVER handled such a thing. (shrug) so 
it's a teaching moment for those folks.

Unaccustomed as I am with public speaking (snort!), I'll welcome some 
discussion from the audience.  I'm sure some attendees to VCF-East will 
know more than I, about some part of vintage-time use (or modern use) of 
audio cassettes for data. So people with an interest or experience, may 
want to think in advance about what they might say, bring props, 
whatever; but keep to the point and be brief.

I'm simply making a point, that cassettes-as-storage was a REAL THING 
that mattered with first-gen microcomputers; it wasn't that hard; and 
these things are surviving pretty well.

One thing I'd like to hear from others about, was the volume of 
cassettes available for 1980's video-gaming "systems", for instance the 
Timex/Sinclair 1000. Early Apple IIs and TRS-80's used cassettes. Those 
systems weren't on my radar at that time.  My impression is that a lot 
of little companies, computer clubs, individuals, distributed bunches of 
those program cassettes in the period. If anyone remembers cassettes for 
their system, consider speaking up at the talk.

If you are so moved about some notions on the subject, email me via my 
retrotechnology.com site. A Web search of my domain will find plenty of 
cassette material, but it might spoil any surprises from my talk! ;)

Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net

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