|Colossus Mark 1|
|| EXIT | Colossus Mark 1| Introduction ||
Colossus was developed to break the coded messages which were generated by the German Lorenz SZ42 cipher machine, during the second world war. The encrpyted messages from the Lorenz were originally sent as morse code over the radio. The messages were intercepted by allied radio operators who would write down the morse code, which was later punched as Baudot teleprinter code, and fed into Colossus as a paper tape loop to be read by optical detectors at 5000 charaters per second!
Only two years after assembing the racking, by 1996 the Rebuild Team was able to demonstrate the basic working functions of a Mark 1 Colossus, but only at a 2 bit level, out of the five parallel bits coming from the paper tape reader. However, this was achieved without the J or K racks being fully wired and so it took almost another three years to devise the circuits and complete the very complex wiring.
Tony Sales writes "Now I turned to the paper tape reader and got that working on all five tracks, but not very reliably. So by 1999 we had repeated the 1996 results, but with signals now correctly routed through the switches on the J rack."
Thus by late 1999 the rebuild more closely resembled an original machine.
Towards the end of 1999, a sign above the rebuild declared "Colossus is Year 2000 Compliant"!
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