The US 6812 Division Bombe Report Eastcote 1944 Page 36

Tony Sale's Codes and Ciphers

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- 31 - TOP SECRET-T



The operator is instructed by this menu to use BSP as the setting of the
drums on link BS for all wheel orders except those ending in 1, in which case
he is to use the setting BRP. Similarly for the link SX BRF shall be used as
the setting for all wheel orders except those ending in 2, in which case BSF
is to be used. The checker must observe these same instructions. Samples of
the checking of the above menu will be found in fig.26. In this message it is
probable that the enemy operator did not change his indicators after each 250
letters of the message. Therefore the wheel settings are based on the
reference point for the beginning of the message. Hence,BSA,BST,&.

Phantom Links. - When the crib includes a letter and link which would make
the menu too strong (give less than one stop per wheel order, and require the
removal of more than one link to get a check stop) it is customary to include
the letter and link in the menu but indicate it as a phantom. This is done by
enclosing the link and letter in parentheses and marking it "phantom", in
this fashion >E(-zc/PH- L) |When a phantom is included in the menu it is
disregarded by the bombe operator but is used in checking. In checking the
letters of phantom links are placed at the bottom of the column of menu
letters. To the left of each phantom letter is put the abbreviation PH. Legal
contradictions involving the stecker of the phantom link letter are treated
the same as legals on outlying links in the analysis of the stop.
The checker, should he get a HUT 6 stop, then checks the phantom to see
whether it gives a legal contradiction. If it does and if the stop already
included a legal contradiction, the stop becomes a bad stop. If the stop did
not already include a legal contradiction ,and the phantom contributes only
one legal contradiction, it is still considered a HUT 6 stop. However an
illegal contradiction is also allowable on the phantom link, and provided it
is the only contradiction on the stop it should be sent to HUT 6. It is
customary to use from i to 3 phantoms.

Self Steckered Menus. - When a key is being used a second day it is only
necessary to determine the wheel order and ringstellung for the second day.
This is done by making a menu out of the known self steckered letters. The
following would be a typical menu.



The circles around the letters means that they are self-steckered, and only
stops where these letters are steckered to themselves are wanted. It can
easily be seen that one such letter will decrease the number of stops by 25-1
because normally the machine will stop when it is steckered to any of the 26
but if we are only interested


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