Here they were used to building office calculators and sorters in which relays performed simple logical functions such as adding and recognising.
It was now their task to make relays perform the switching job required for the Bombe to 'recognise' the positions in which consistency appeared, and stop.
Here again, Alan was the right person to see what was needed, for his unusual experience with the relay multiplier had given him insight into the problems of embodying logical manipulations in this kind of machinery.
Perhaps no one, in 1940, was better placed to oversee such work than he.
Yet Alan had not seen that a dramatic improvement could be made to his design.
Here it was Gordon Welchman who played the vital part. He had moved into the Enigma cryptanalytic group with a remarkable achievement to his credit:
he had re-invented the perforated sheets method by himself, entirely ignorant of the fact that the Poles had worked it out and that Jeffries already had the production in hand.
Then, on studying the Turing Bombe design, he saw that it had failed to exploit Enigma weakness to the full.
Returning to the illustration of the Turing Bombe, we notice that there are other implications which were not followed up, as indicated by the heavier lines: