My first experience with fixing an electromechanical device, and perhaps an explanation for my entire career, came when a friend and I broke the punch card reader at school. We felt obliged to fix it, since it was 3 AM and we weren’t supposed to be in the computer lab in the first place. So while my panicked friend watched, and kept watch, I took the damn thing apart, cleaned out the shredded cards, and put the machine back together. One of us was not surprised when we plugged it back in and it worked (I’ll leave it to you to figure out who was surprised.)
What sparked this memory? This blog entry from Laura at Ypsi-dixit which references a discussion on an email board run by a SF club in Michigan; I was pointed to Laura’s post by a note on Dave Farber’s Interesting People mailing list.
The posters figure out how many punch cards it’d take to read a 3-minute mp3. Answer?
“Assuming a non-Hollerith encoding with eight bits per column, and an MP3 file encoded at 128kbps CBR, there would be 36,864 cards in that deck, and the card reader would need a throughput of 205 cards per second. It might be wise to include an 8-column sequence number, however, so that a misordered deck can be repaired by a card sorter; with 72 data columns per card, the total is precisely 40,960 cards (40K cards), requiring a 228 card/second throughput.”
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