The original Tunny machine was simply a functional reproduction of the
German Tunny machine, operated electrically instead of largely mechanically. It
way intended primarily for straight forward decoding. It was developed in two
(i) as a decoding machine improvements were effected and gadgets added for
ease of operation, not for versatility.
(ii) as an aid to Newmanry setting and breaking, much more versatile models
There were several versions of each, some of the early ones being very
awkward in operation e.g. patterns were set up by means of U-shaped pins, and
wheels were reset by stepping each uniselector switch by hand, one position at a
tine, and forwards only. Only the later models will be described.
A weakness common to all Tunnies is that the five impulses of each letter of
Z are sent through the machine successively though by different routes, and can be
added or permuted only with the aid of remembering circuits. This restriction
does not apply to the wheels.
56K THE (NEWMANRY) TUNNY MACHINE (Fig 58(xxv)).
(a) General description of operation.
The tape is fed into an auto-transmitter: chi, psi, unless cut out, are
added automatically, and the sum appears on another tape, letter by letter. At
each letter the current settings of all wheels are exhibited.
Each wheel has two rows or jacks, in which shorting plugs can be inserted.
The upper row represents the pattern; the lower row determines the initial
setting. Each wheel has also one row of indicator lamps to show its current
The "display" shows not the wheel settings but the number of positions
through which the wheels have moved: the three rows of figures correspond to Chi,
(with Z and Mu61), Mu37, Psi. Each row has a cut-out switch.
Switches K P B ( for X2oneback , P5twoback , PSI1'oneback,) one or more
being thrown determine the limitation.
The characters of PSI1'oneback , P5twoback , P5oneback , which are just
before the start of Z can be preset by spring switches: P5twoback. P5oneback are
set simultaneously by switch positions: .. , .x, x., xx .