The Newmanry History

Part of the General Report on Tunny (1945)

Page 349

Tony Sale's
Codes and Ciphers

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53M Page 349
(iv) The short wheel-breaking run 3+/1.2. It is not worth while to use multiple
test for one-wheel runs, unless the tape is very long, as it may be in chi-
breaking. For the reason why 3+1 is switched to cross see 25A.(b) R1 R2 R3 R4 R5
are switched into counters 5,4,3,2,1 so that scores shall be printed An the
correct order [53L (c)].

(a) The principle of Colossus Rectangling.

To render the gadget more intelligible the how and why of Colossus

Suppose that the Chi 1, Chi 2 triggers each contain one cross, that Q = X ;
and that Q is switched : Q1 = x, Q2 = x. This will select a set of places all of
which are opposite a particular character of chi1, ands also opposite a particular
character of chi 2, i.e. they will belong to the same cell of the rectangle.

Plug Delta-Z1 + DeltaZ2 = .

Throw the lower stepping switches, so that chi 1 (down) steps fast and
controls chi 2 (up).

Chi 1 will step, producing a row of the rectangle : when Chi 1 reaches the
setting plug, chi 2 will step one.

Chi 1 then step again, producing the next row, and so on.