General Report on Tunny

14B Page 30

The TUNNY ROOMS housed copying machines as described in the last chapter. Tunny Room (Block F) undertook the preparation and copying of tapes for setting and the making of printed de-chis (i.e. printed copies of the D-stream for sending to the Testery). Room D (Block H) undertook the preparation and copying of wheel-breaking and crib tapes and the making of printed rectangles.

COLOSSI in Block F were used for setting, those in Block H primarily for wheel-breaking and Rectangle-making and the residue for setting. When ROBINSONS were used for setting these were housed in Block F but improved ("super") Robinsons - used mainly for Cribs - were installed in Block H.

Details of Tunny Room and Colossus jobs were left to the operators concerned but the jobs were ordered by the REGISTRARS and returned to them on completion. The OPS. REGISTRY in Block F (Ops.) consisted of the RUNS REGISTRARS who issued setting jobs to Colossi (previously to Robinsons), the TAPES REGISTRARS who issued jobs to the Tunny Room (Block F), and the LOGS REGISTRAR who kept in touch with Room 12 and kept track of all tapes sent up by them for setting. In Block H there was a single K-REGISTRY which kept track of all wheel-breaking tapes and ordered any Tunny Room or Colossus jobs.

In addition to these departments, Block H housed the computers and (Newmanry) Cribs section.

COMPUTERS, under the direction of the RECTANGLES REGISTRAR converged rectangles and did other paper work on Key Rectangles and Flags.

The (Newmanry) CRIBS Man and Registrar selected suitable messages for crib jobs with the help of Sixta and (Testery) Cribs Watch, and itself organised and ordered the necessary tape-making and Robinson Runs. In addition to this, they were responsible for any other (routine or experimental) Robinson jobs.

Maintenance of machines was the responsibility of the engineer in charge.

(c) Major Tester's Section.

Room 41 contained registrars, and cryptographers for psi-breaking and setting (by hand) from de-chis, reading of depths, and wheel-breaking from Key (by hand). DRAGON - though in a different room - was fed and operated by members of Room 41. The head of Room 41 was in general charge of all work in Major Tester's section on his shift.

De-chis on which psis were broken or set at some point in the message were passed to ROOM 40. ROOM 40 were responsible for Motor breaking and setting, and for finding settings for all wheels as near the start of the message as possible. It also dealt with decoding breakdowns.

Messages set on all wheels were passed to the supervisor of the Decoding Room who issued them to decoding machines as soon as possible, and checked them on return.

Decodes were read by the (Testery) CRIBS watch who routed them to the correct intelligence section and looked out for items of cryptographic importance or of wireless importance (for Sixta) and in particular for possible retransmissions which might serve as cribs.

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