The US 6812 Division Bombe Report Eastcote 1944 Page 40

Tony Sale's Codes and Ciphers

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- 35 - TOP SECRET-T
contradictions since it does not use a diagonal board. A stop is considered
good if it has one contradiction either legal or illegal. Assume the
following menu:




Fig. 31. Plugging for Dummy Letter Menu in Fig.30.


There is no diagonal board available for the 4th chain - hence all patching
is made as if all letters were query letters and commoning plug-jacks are
patched together directly to avoid the use of cords and common jacks.

When a relay appears on the third alphabet it may be a stop on either

the 3rd or 4th input. In order to determine to which bank it belongs turn
off the carry and the 4th chain. If the relay returns the stop must be on
the 3rd bank. When sending stops to the checker on the dummy bank, the
operator must label each stop D.L. , because since the menu is not plugged
to the diagonal board, all the stops with illegal contradictions will be
correct (providing the stop goes round all the closures). Although illegal
contradictions are permitted on the dummy bank, the right stop cannot
contain legals or illegals.

Query Letter Menus. - Sometimes the enemy operator encodes his wheel
position twice as ART UXG ART ZET. Hence ART is the point at which to set
the wheels and decode UXG to get the wheel setting for the message. UXG
represents encodement at positions ZZA,ZZB,ZZC while ZFT represents
encodement of the same indicator at

Hand-written Note: 10/NOV/44 (A recent notice from BP states that if a query
letter menu marked SSO is being checked, only stops which have a different
(unreadable) including those on (unreadable) links should be sent.)


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