By using the switch position e' the X, PSI trigger e can be used in a
different way as a "special pattern" or "doubting" trigger. Similarly g' is the
special pattern Mu trigger.
e' in not added into Q (see Q panel: 53J (a) ).
g' does not motorize the PSI's.
Indeed these patterns appear nowhere except in the seven special pattern
jacks on the plug panel, and to have any effect they must be plugged.
These are used in addition to an ordinary trigger.
(c) Wheel-breaking Panel
On wheel-breaking Colossi there is the inestimable boon of a panel on the
front of the machine, carrying an ordinary X trigger and a special pattern X
trigger: in place of U-shaped pins, easily inserted plugs are used: they are so
much easier that they are often used for setting. Each of the 5 X wheels has its
ordinary and special patterns adjacent and each is controlled by a 3-way switch
whose positions are
( down: ordinary and special patterns in,
( normal: all out,
( up: single cross in the last position of the
(d) Motorization and Limitation determiner switches
The motion of Mu37 and the PSI's is not uniform, but simulates that of the
corresponding wheels of the German Tunny machine.
On Colossus the extension of the Mu37 pattern by Mu61 is fixed. The
extension of the PSI pattern is naturally adjustable to suit the limitation. The
appropriate switches are near the bottom of the selection panel viz
PSI1oneback, X2oneback, PSI5twoback: if one or more of these switches are
either up or down the corresponding impulses are added and used as the limitation.
At the beginning of the text these, since they refer to places one or two back,
are indeterminate: the up and down positions of these switches and of P5twoback
impose an arbitrary dot or cross, in these places.
BM C/o is the basic motor cut-out. When it is used the total motor is
53D STEPPING AND SETTING
The setting of a wheel is that character of the wheel which corresponds to
the first sprocket hole of Z.
All wheels can be given assigned settings, simultaneously, by putting plugs
in the appropriate setting jacks and depressing the switch SU. The setting jacks
are arranged below the control panel in 12 rows which correspond to the 12 wheels.