The US 6812 Division Bombe Report Eastcote 1944 Page 17

Tony Sale's Codes and Ciphers

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- 12 - TOP SECRET-T

It is often specified that non-crashing wheel orders be used. It is
the practise of enemy encoders not to use crashing wheel orders on
successive days. For instance if wheel order 523 has been used on the
first of the month, the wheel order for the second of the month must
not include a 5 for the first wheel, a 2 for the second wheel, or a 3
for the third wheel. For example 415 would be a non crashing wheel
order which could be used on the second of the month. When all w/os
n/c are requested there will be 32 w/os to run. The abbreviated
request will read n/c 321 which means that you will run all w/os not
beginning with a 3, or with a median 2, or a final 1. N/c. 321 & 452
indicates that all w/os will be run that do not begin with a 3 or 4,
or with a median 2 or 5, or a final 1 or 2. Other W/os an preferences
would be as follows.



CHECKING BOMBE STOPS.

Each stop obtained from the bombe is verified on a checking

machine. This machine has 4 enigma wheels, keys and lamps and is
the equivalent of the enigma machine minus the stecker board. When a
stop is obtained from the bombe, the operator supplies the following
data to the checker, -Stop No., wheel order, Ringstellung setting,
and Stecker of input letter. The checker prepares a checking sheet as
shown in figure 17, filling in the details called for at the top of
the sheet. He writes the alphabet across the top of the sheet and
circles the letters on the main chain. A tadpole (wavy line) is drawn
below the letters on the subsidiary chain. The letters of the menu
are written down in the narrow column at the left of the sheet,
starting with the input letter and following consecutively around the
menu so as to check through closures first.
There are 3 squares at the top of each column on the checking sheet.
When a stop is received, write down the serial number in the second
square, wheel order and letters of the stop in the bottom square, and
the relay letter opposite the input letter. The top square is left
blank until after the stop is checked. The extreme left hand drum
should have the Ringstellung (revolving disc) set with Z at the spot
on the drum and the drum is set so that the pointer points to B. This
setting makes the wiring of the drum The equivalent of the current
enemy uncle walter. Set up the letters of the stop on the other three
drums by the desired letter on the revolving disc to the spot on the
drum. Set the letters of the stop from left to right on the three
drums. Revolve the three drums so that


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