Decoding Resources consisted of a Supervisor; 13 machines 10 operators and 3
engineers on each watch. There were occasional interchanges of staff with
The Supervisor registered messages to be decoded, and issued them to
machines, which had to be set up so that messages could be dealt with, with
suitable priority. The supervisor verified from the decodes on their return, that
the machines had been set up correctly on all impulses.
Operators needed to be touch-typists and to be able to recognise P and to be
trained sufficiently in Tunny to solve minor breakdown problems. Major breakdowns
were passed back to Room 40.
In the later stages, tape decoding was introduced. It was found to be much
faster than hand decoding on long messages, but slower on short ones. Corrupt
messages were better dealt with by hand methods.
Rewrites of poor or unreliable cipher text could be obtained through the
C.O. from Knockholt, and when necessary a slide run on approximate chi-settings
could be done in the Newmanry.
In the early days decoding had to be interrupted for short periods while
repairs and adjustments were carried out.
The number of machines steadily increased to the final total of 13 and
during the last 12 months or so, it was possible to have the engineers working on
the machines which were not actually required for current work.
The Cribs Watch was created, to read decoded material "en passant", and
contained 5 German linguists covering three shifts.
Its duties were:
(i) To pick out possible retransmissions from incomplete decodes still on
the machines, to assist operators in correcting breakdowns by suggesting
probable clear text, and to expedite the issue of particularly urgent
(ii) To check the general accuracy of completed decodes, and to route the
different messages found in each decode, to the appropriate actions.
(iii) Later, to reread the duplicate copy of each decode (returned from Room
12) with the object of marking any information of interest to Sixta and of
informing Mr.Page's section of any possible cribs.
(iv) To sort amended and typed decodes from Hut 3 and extract and file
examples of routine messages for the benefit of Room 41.