The US 6812 Division Bombe Report Eastcote 1944 Page 62

Tony Sale's Codes and Ciphers

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- 50 - TOP SECRET-T

subsidiary chain all entries back onto the main chain must result in a
confirmation, otherwise there is an illegal contradiction and the stop is
wrong. The checker inspects the steckers and marks the legal contradict-
ions. In the example there are three legal contradictions on steckers S, W
and F. A summary is made of the total number of self steckers, legal
contradictions and confirmations for the stop and these are written at the
bottom of the stecker column.

In checking stops the checker will always give preference to the

first stop on a new wheel order so that the operator will have a good stop
checked for each bank as soon as possible.

C.S.K.O. In checking CSKO menus the checker must make sure no

consecutive steckers are obtained. To do this, the two letters which are
the consecutive steckers of each letter on the menu are written down just
to the left of the column of menu letters. As each stecker is obtained, the
checker verifies that it is one of the two consecutive steckers shown
opposite the menu letters. If it is a consecutive stecker the normal
procedure for reporting wrong stops is followed. Remember that A is not a
consecutive stecker of Z and vice versa. All other letters have 2
consecutive steckers.

DOUBLE RELAY STOPS. The menu is checked completely with each stecker

of the input (each relay), giving two complete stories for the stop. When
valuing the stop, the checker first considers each story separately to see
if either will stand alone. If neither will stand alone they will be valued
together to see if it is a boxing stop. (Note: If one story will stand
alone and not the other it cannot be a boxing stop. A boxing stop usually
will have confirmations between the two stories. A double relay stop can be
the right stop to bring up the job using one of the stories given by the
stop. The checker will inform the IC OPS that it is a double relay stop and
say which of the two steckers is the one for the good stop. A boxing
stop is right from the machine point of view but cannot be the stop to
bring the job up.

PHANTOM LINKS. In checking phantom links the checker will put the

letters of the phantom links at the bottom of the column of menu letters.
To the left of each phantom letter he will put the abbreviation PH. Legal
contradictions involving the stecker of a phantom letter are treated the
same as legals on outlying links in the analysis of the stop. However an
illegal contradiction is also allowable on the phantom link, provided it is
the only contradiction on the stop when it is phoned to the IC OPS.

STOP CHECKS AS GOOD.

A correct stop is one that confirms all closures and has no legal

contradictions from a machine point of view. In the square at the top of
the column the checker puts a check mark for a correct stop and a cross for
a wrong stop. The checker will sign his name at the bottom of the stecker
column for the first stop he checks and initial all subsequent stops he
checks. Certain stops, referred to as Hut 6 stops, are marked in the square
at the top of the column by the letters MC in addition to the check mark,
and are phoned to the IC OPS as soon as they are completely checked. These
are:

1. Any correct stop, excepting a check stop, having no legal
contradiction.
2. Any correct stop, except a check stop, with one legal
contradiction, provided one of the two letters involved is on an
outlying link.
3. Any correct stop, excepting a check stop, in which you reach the
subsidiary chain twice by two different steckers from the main
chain giving two different steckers for each subsidiary chain
letter provide one or both of the main chain steckers are on out-
lying links.




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