The Newmanry History
Part of the General Report on Tunny(1945)
Codes and Ciphers
53H Page 339
(h)"Letter Count" (LEC switch on control panel)
is for making counts at fixed settings. It stops the machine after printing
a batch of scores: without it the same count would be repeated. Whilst one batch
of scores is being printed, the next batch can be switched.
(i) Printer Cut Out (PC switch on control panel)
prevents Colossus from sending impulses to the printer, so that stepping
ceases [ cf. storage if scores in para. (c) above].
(j) Reset (switch on control panel)
clears all scores in storage: in particular if PCO is in use it allows
stepping to be resumed.
(k) The Printer
The printer is an electromatic typewriter.
It can be operated manually for the insertion of data (e.g. sigma , S.T.
span) not printed by Colossus.
Single, double and triple line feed are available.
The inexplicably assorted founts are not intended for cryptography, but
this seems to be no handicap: sigma has appeared as £, @, $ .
is a device whereby Colossus counts only over a selected stretch of the
There are three groups of decade switches (Fig 58(xvi)) above the plug panel
each reading 0000 - 9999 labelled
START COUNTERS , START PSIS , END OF SPAN.
If "start counter" is set to m. where m is not 0000, "end of span" to n ,
Colossus counts only from the (m+1)th to nth places on the tape, inclusive.
If "start counter" is set to 0000, spanning is ineffective, the first place
on the tape cannot be included in a span.
(b) The settings
The settings on Colossus refer to the start of the tape, not the start of
Motorizing of the PSI's begins at the place to which "start psis" is set:
normally this is 0000, the start of the tape.
(c) On Colossi with long bedsteads
there is a rudimentary 5th decade in the bottom row of the selection panel.
Switches are thrown down for