# The Newmanry History

## Part of the General Report on Tunny (1945)

### Page 377

Tony Sale's
Codes and Ciphers

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(d) Wheel switches.

Each wheel has a separate switch. Unless a wheel is switched in, it has no
effect whatever, e.g. if X2 is not in, the limitation will be incorrect and the
psis will move incorrectly [ c.f. Para (e)].

The chi, psi master switches merely determine whether the wheels move or
remain stationary.

 In normal operation the motion of the psis depends on some or all of Z, Chi, Psi, Motor, but only Z, Chi, Psi are added in the resultant tape. It is sometimes desirable to modify this in various ways, e.g. in a total motor tape Mu37 and the limitation are involved in the resultant tape; Z, Chi, Psi are not to be added to it, but Z, Chi, Psi (or X2 at least) cannot be switched out [compare para (d)] because they determine the limitation. To each or the five impulses corresponds a column of jacks (see diagram : where no suffix is shown, that corresponding to the column is to be assumed). It will be seen that Psi, X2oneback, Mu, P5twoback have each an "in" jack and an "out" jack. Anything put into "in" appears at "out" with the appropriate impulse added to it. Chi has no in jack being normally connected to "IMP", which is in effect, "Z out". Xoneback PSIoneback have no out jacks being permanently connected to PSI X2 respectively. Chi and psi are normally connected both up and down (dotted lines) but a plug inserted in one of their jacks automatically breaks the normal connection to that Jack. Wheels may be transferred from one column to another, but Z cannot. There are a few common jacks.

(f) Stop setting.

Decade switches reading 0-9999 can be set so that the machine stops after so
many letters of Z.

(g) Contraction.

Because Robinson psi-setting required a de-chi tape contracted by the
omission of letters against total motor dots [52 (d)], several Tunnies included a
facility for making such tapes.

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