14C Page 31
SIXTA (non-morse) - Mr. Uzielli's section - read the unciphered chat between German Operators (which was intercepted at Knockholt), and studied Fish wireless procedure from the Logs of intercept stations and decodes. In particular Sixta supplied information about Retransmissions, daily times of QZZ, and any change of machine (and limitation) used.
This section gives four examples of the passage of a message through the two sections in various circumstances. The examples are typical but clearly not exhaustive. The methods referred to are defined in Section 12B.
(a) 1st method. Setting.
The Tape arrives in Room 11; is passed to the Ops. Registry; sent by the Tapes Registrar to Tunny Room to be prepared for Colossus and returned; sent by the Runs Registrar to Colossus for chi-setting and returned. If set, a de-chi is ordered by the Tapes Registrar and returned. Tapes, de-chi, and chi-settings are then sent from the Ops. Registry to Room 12.
De-chi with RF and chi-settings is sent by Room 12 to Room 41 for psi setting, passed on to Room 40 for motor settings, and on to the Decoding Room. The decode is passed to the Cribs Watch who route it to the appropriate intelligence section via Room 12.
(b) 2nd method. Setting.
The tape arrives in Room 11; is passed to the Ops. Registry; sent by the Tapes Registrar to Tunny Room to be prepared for Colossus and returned. Sent by the Runs Registrar to Colossus for setting on all wheels and returned. If set, tapes and settings are sent to Room 12.
RF and settings are sent from Room 12 to the Decoding Room - then as in (a).
(c) 1st method. Wheel-breaking.
The tape arrives in Block H; is passed to H-Registry; thence it is EITHER sent to Room D for Rectangling on Garbo and returned, OR sent to Room D to be prepared for Colossus and then to Colossus for rectangling and returned. The rectangle is sent to the computers for convergence.
If significant, Tapes and Rectangle go to Colossus for chi-breaking and, if successful, tapes and chi patterns are sent to the Ops. Registry via the H-Registry. A de-chi is ordered from Tunny Room (F) by the Tapes Registrar and returned, and tapes, dechi and chi patterns sent from the Ops. Registry to Room 12.
De-chi with RF and chi patterns is sent by Room 12 to Room 41 for psi-breaking, passed on to Room 40 for motor-breaking, and on to the Decoding Room - then as in (a).