15 - Running the Bombe
The Bombe was designed to find the three essential parts of the original Enigma setting used for a particular network for a 24-hour period set up by the German operator, who used a ‘key sheet’ broken down into daily settings for a month. There were hundreds of these networks, although only about 50 were operational at any time.
The Bombe sought to find for each stop:
Wheel order
Ring setting
One stecker pair
Three banks of 12 drums each were set up on the Bombe each day. The ring setting for the stop was each drum, found from the indicator drums, relative to ZZZ. Typically, ten pairs of letters were plugged up or ‘steckered’ on the Enigma plugboard as part of the daily key setting, and a Bombe stop would suggest one of these pairings.
(c) John Jackson
