Kansas City standard cassette recording

From: Don Maslin <donm_at_cts.com>
Date: Mon Dec 4 18:05:37 2000

A tad over two years ago, there was some dialogue about the Kansas City
standard for cassette recording of microcomputer files, and a chap named
Heinz W. Wiggeshoff provided some information via
alt.folklore.computers, and offered both images of programatic nature and
circuit information on request. (See following.)

If anyone obtained those images and circuit information, please respond
to philpem_at_btinternet.com with Cc to me.

Many thanks.
                                                 - don

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From: ab528_at_FreeNet.Carleton.CA (Heinz W. Wiggeshoff)
Newsgroups: alt.folklore.computers
Subject: Re: Kansas City cassette recording format
Date: 9 Dec 1997 19:00:30 GMT
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Stephen Crane (jsc_at_outoften.doc.ic.ac.uk) writes:
> Anyone out there got any technical information about this? I have
> some cassettes of varying age and quality whose information I'd like
> to retrieve, preferably using my PC's audio card. Ideally, someone
> will have written a program for Linux which does this but, given the
> info, I'll have a bash at it over Xmas.

   From Microprocessor Interfacing Techniques by
   Austin Lesea and Rodnay Zaks (whatever happened to him?)
   c/r 1978 SYBEX Inc.
   ISBN 0-89588-003-2
   p. 128


      In order to use these inexpensive recorders in the hobby market,
   a standard was proposed and adopted by hobbyists. Using frequency
   shift keying techniques, and frequency double frequency [sic] modem
   techniques, this standard is easy to use. The drawback is the data
   rate of 30 characters per second.
      The system takes standard serial RS-232C data ... and converts
   each bit to either 8 cycles of 2400 hertz (a "1") or 4 cycles of
   1200 hertz (a "0"). To generate this, only a few flip-flips [sic]
   are required along with a quad NAND gate. Shown in Fig. 4-55 is the

      [Image sent on request]
      [Circuit function, ditto]

      The demodulator must detect whether 1200 hertz or 2400 hertz
   tones are present. There are many ways of doing this; however a
   common one is to detect zero crossings of the input signal. This
   will generate either 2400 or 4800 pulses per second.
   [Circuit details sent on request]
      The circuit for the demodulator appears in Fig. 4-56. The de-
   modulator timing appears in Fig. 4-57. Note how one gets back what
   one started with, along with the necessary clock information.
      If the tape speed varies, the data may still be recovered as the
   clock information will insure the UART receives the proper timing
      No special software is needed as this interface makes the cassette
   look like a paper-tape, punch-reader combination to the computer.

      [Images sent on request]

   (This format is found between the KIM cassette interface, and the
   One Chip Digital Cassette controller using the NEC UPD371D.)

   (Surprisingly, the documentation for my Heathkit ETA-3400 only
   mentions the frequencies, not the details of the encoding.)
Received on Mon Dec 04 2000 - 18:05:37 GMT

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