The US 6812 Division Bombe Report Eastcote 1944 Page 34

Tony Sale's Codes and Ciphers

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- 29 - TOP SECRET-T

C.S.K.O. (Consecutive Stecker Knock Out). - It has been observed that some
enemy encoders have a rule not to use consecutive letters for steckers, e.g.
they would not use either A or C is a stecker for B. In breaking such
traffic, stops which include such consecutive steckers can be thrown out.
This is done automatically by the use of the CSKO jack which causes the
bombe to reject such stops and continue testing. The CSKO jack is located
in the column of COMMONS jacks just below the INPUT COMMONS and is painted
red. To make the feature effective a short circuiting plug is inserted in
the CSKO jack. This is the last plug put into the bombe when setting it up
and is the first to come out when stripping. It's circuit is as follows:



The condition for a stop is that one point on each row of the diagonal
board has no current flowing through it. Let us assume we get a stop and
find, by checking, the following steckers:


MENU STECKER
F E"
E F"
D B"
C (C)
B D"
A (A)


We do not want the bombe to stop under this condition, as E is a consecutive
stecker for F and vice versa, This will be accomplished through the CSKO
jack which ties e on F and f on E to 2 points on each horizontal row. Since
25 points on each row will have current on them (only 1 point per row will
not), this jack feeds current to c on F and f on E and rejects the stop.

Cilly Settings. -Certain enemy operators show a tendency to use stereotyped
settings for the indicators at the beginning of their messages. They
sometimes use the last position of the previous message as one of the
indicators for this purpose. This practise gives the person breaking the
message an insight into the probable settings for different links. The
following is a typical menu taking advantage of this tendency:


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