[Coco] Dorsett Educational Tapes

[Melanie and John Mark Mobley]

Link: https://archive.org/details/TRS-80ColorComputerDorsettEducational

I have reviewed one of the Dorsett Educational tapes on Tomas Edison.
It should be a mono (not stereo) file.  The data and the voice/audio is on
the same track.  Apparently no special hardware was required to read this
file, when it was new.  The program can use motor on/off and audio on/off to
prevent the data portion for playing out the speaker.

The XRoar emulator can load a digital audio file, such as a wave file.

The file has too much noise and/or too little signal strength.
I think the file uses Frequency-Shift Keying for modulation of the data.  I
think the CoCo makes one sine wave cycle for each bit.  I think the CoCo
hardware measures the time between zero-crossings in order to demodulate the
audio stream.  Does this should correct?

If I could make a 7Hz band pass software digital filter for each of the
frequencies of interest then I could clean up the files.
Perhaps a software Schmitt trigger like comparator could be used to clean up
the zero crossing and make the files readable again.  Any thoughts on these
ideas?

-John Mark Mobley