The corrected or doctored tape was compared with the first version by
hand and the corrected length verified on a hand counter. It was marked
CORRECTED TAPE or DOCTORED TAPE in block capitals.
35D PREPARATION OF MESSAGE TAPES
(a) For Colossus
Tapes were copied (on Angel) if sufficient copies were not available,
or if available copies had not sufficient blanks at either end. Tapes issued were
stuck into closed circuits as shown, and stop and start signs punched with a
special metal gadget. An overlap of two sprocket holes was allowed at the join;
the join had to be made with smooth edges and the end ( as opposed to the
beginning) of the tape on the outside of the circuit.
The text length was measured before the tapes were returned to the
Registrar and if it failed to agree with the Knockholt estimate, Knockholt were
If the text length was below 1500, copied tapes were made on which the
text was followed by RYRY... till the total length of text exceeded 1500. This
was done by feeding a tape reading RYRY.. into the Angel input as soon as the real
text had been copied.
For issue to Colossi with short bedsteads very long tapes were stuck
in parts of text length 10172 with an overlay of 4 between each part ( 1-10172,
10169 - 20340, 20337 - end) [see 53B(b)]
(b) For Robinson
Message tapes were prepared for Robinson as for Colossus except that a
mixture of Bostick and benzene was used for sticking. The tape to be stuck was
inserted between two electrically heated plates ( a 'hot sticker' ) and the
benzene was evaporated.
35E MAKING OF DE-CHIS
(a) Without Colossus check
The settings and wheels for the de-chi were written on the chit by the
Tapes Registrar with a hand check of the first 41 letters of the de-chi. The
dechi was made on a Tunny machine twice, and if both makes agreed one make was
stuck for Colossus or Robinson and returned to the Registrar. The Tunny was not
stopped during either make.
If the Delta-D count on the de-chi tape checked with that on the Z
tape, the dechi tape was returned to the Tunny Room for printing (on Garbo) in
rows of 31 with double spacing. To check the print the de-chi tape was marked at
positions 1,621,1241 etc.