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11728Re: Cassette tapes

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  • joshbensadon
    Dec 5, 2012
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      Hi Herb,

      Surely you must have heard of the Kansas City Standard?
      I read an article on it in the 70's. Some guys that met in Kansas City decided to make a standard to encode bits on cassette. I don't recall the standard exactly, but it's goal is to have 1's and 0's to occupy the same amount of tape. So they did something like 4 cycles of 2400Hz for logic 1 and 2 cycles of 1200Hz for logic 0. These numbers might not be the actual values, but you can google it.

      I think I scanned this article from Popular Electronics... let me try finding it. It would be on Rich Cini's web site.

      Regards,
      Josh


      --- In cosmacelf@yahoogroups.com, "thinkpast" <hjohnson@...> wrote:
      >
      >
      >
      > --- In cosmacelf@yahoogroups.com, "Chris" <cwardell2000@> wrote:
      > >
      > > Herb,
      > >
      > > The files section contains a "Giant Board HTML" folder that has the Netronics documentation for the "Giant Board" which is what added cassette I/O to the ELF II. You will find the schematic which includes the cassette circuits and the binary code for the monitor program that includes cassette read and write routines.
      > >
      > > C.W.
      > >
      > I'm on it! Thanks. Now I have to figure out how fast the ELF II ran instructions, as that sets the rate for the 1's and 0's the cassette interface produced or reads. The docs with the Giant Board mention "like the Kansas City standard" but that may mean "an apple is a fruit like a banana". I'll add some docs and annotated code to the page linked below, maybe someone with more clues than I can help on this?
      >
      > http://www.retrotechnology.com/restore/cass_super.html
      >
      > Herb
      >
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