General Report on Tunny

14C Page 32

(d) 3rd method.    Wheel-breaking from Depth.

Printed texts of the alleged depth are teleprinted to Room 11 and passed to Room 41. If the alleged depth is read successfully, wheel-breaking from Key starts at once by hand in Room 41, but the key is also sent to Block H where it is perforated and rectangled in Room D, a combined flag being then made by the computers. If significant the partial chis from the flag are passed to the key-breaker in Room 41.

If chis and psi patterns are broken successfully they are passed with Key and RF to Room 40 for Motor-breaking, then on to the Decoding Room and as in (a).

Tapes on which setting and wheel-breaking are abandoned are returned to Room 12 and T-Registry respectively.

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