as Tutte's "1+2 break in". It involved calculating the following Boolean function:
:::and counting the number of times it yielded "false" (zero). If this number exceeded a pre-defined threshold value known as the "set total", it was printed out. The cryptanalyst would examine the printout to determine which of the putative start positions was most likely to be the correct one for the chi-1 and chi-2 wheels.

This technique would then be applied to other pairs of, or single,