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TI cassette sound in Transformers: DOTM


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In the beginning of the movie when you see a NASA guy look at some oscilloscope, you hear a TI-99/4A cassette data loading sound. Shit you not. It's a Kansas city standard(so I read in Wikipedia), but was unusual to hear in 2011 movie.


It's there! I swear!

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While I do not rely upon Wikipedia as a definitive tomb of wisdom, the TI is missing from the Wikipedia list of home computers using the KCS. Is this the format we actually use?


I thought it was Kansas. Could be wrong. I was just one day reading up about computers on cassette & stumbled upon the Kansas city standard. It sure sounded a lot like the TI format.

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This doesn't look like the TI tape system in use. I've never seen this standard referred to in any documentation about the TI before, though (never even heard of it before!)


As usual, just visit Thierry Nouspikel's page for the answer: http://nouspikel.group.shef.ac.uk//ti99/cassette.htm


Bits are encoded by output level changes. With a 3 MHz console, the output toggles every 725.3 microseconds. To encode a 1, invert the output in the middle of this time period... This results in frequencies of 689.37 Hz for a space (0) and 1379 Hz for a mark (1) which is well within the audio range, thus suitable for a tape player.


KCS uses 1200hz and 2400hz tones with specific cycle counts, the TI uses phase changes which result in completely different frequencies, and cycle counting is not used.

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