Computer Audio Tape Formats

From: Matthew Sell <>
Date: Tue Dec 17 16:44:39 2002


I believe that many different computers used the same or very similar
method to record data to cassette.

I'm pretty sure that the Atari 8-bit and the Commodore VIC-20/C-64 tape
recorders used the same method (FSK).

Weren't the same frequencies used for FSK/Teletype ? The Commodore
"Datasette" used 300 baud as the rate (I'm pretty sure).

The Atari cassette recorders put a pause between data packets - it was very
noticeable when you listened to the audio. I don't remember the Commodore
format putting in the long delay.

Just some food for thought....

         - Matt

At 01:50 PM 12/17/2002 -0800, you wrote:
>I am looking for information regarding how various computers wrote
>information to audio tapes.
>For example, the Tandy Color Computer wrote ones and zeros to audio tape
>in the following format:
>'one bit': one sinusoidal cycle _at_ 2400 Hertz.
>'zero bit': one sinusoidal cycle _at_ 1200 Hertz.
>The bit rate is variable on a CoCo tape. But averages to about 1500 bits
>per second.
>I am contemplating creating an audio tape anaylzer to help me recover
>some data. I would like to make the program useful to thoes outside the
>Color Computer community. But first I need to understand all of the
>different methods used to put data on audio tape.
>tim lindner

Matthew Sell
On Time Support, Inc.
(281) 296-6066

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