General Report on Tunny
25D Page 164
consider only scores too large to be explained by random variations in R+ throws away evidence, for in fact R can be found at each settings; but in long subsequent runs such as 4=5=/1=2 it may be necessary to consider only scores which are reasonably good on this basis. In a break-in run, as a little consideration will show, the variation of R is usually negligible.
When two messages have each produced a wheel (generally from a rectangle, or especially, 
) these can be set by a direct comparison of the (incomplete) wheels. See 24Y(c) R1 pp 53, 76, 79, 83, 97; R2 p 29. For application of corrected excess to wrongly set messages (never used) R3 p 91.
(c) Spanning for message slides.
This is particularly important in wheel-breaking: as soon as the rectangle message is on Colossus the 1+2/ score is checked and spanned. If a message slide is found, the remainder of the message is set by slide runs (23F(d)) after which the tape may be doctored so that its parts are in the correct relative position.
Every supporting message set should at once be spanned and possibly doctored.
Doctoring requires only the removal or insertion of sprocket holes. A hole is quickly removed by covering it with opaque paper. Inserting a hole is done by copying and takes time; meanwhile wheel-breaking should proceed on a slide - free portion: if this portion is most of the message, doctoring may not be worth while.
Note. To decide whether to remove or insert a hole imagine that each place on the tape is marked with the corresponding position of (say) chi 1
 |
setting before slide 04 | |
| setting after slide 06 | ||
| slide here | ||
(d) Spanning for changes in ΔP characteristics.
The character of P and hence of ΔP may change considerably during the same 'message' (meaning transmission or QKP), for it may contain several messages, possibly from different originators; hand passages, tables of figures, list of names, etc. will have abnormal characteristics.
+ The standard deviation for this is 
, for the meaning of which (21(n); R4 p4, 11, 12, 17.)
Back to General Report on Tunny. Contents.