The Special Fish Report
Albert W. Small (December 1944)
Codes and Ciphers
TOP SECRET Special Fish Report Page 106
Rectangling was originally done on Garbo by setting the typewriter
to the width of the smaller of the two wheels involved, and recording the Z tape
(or K tape, or etc.) line after line until completing one product cycle of the
two wheels; then setting the paper back in the typewriter to just below the
original starting point and recording the second cycle position by position
just below the equivalent parts of the first cycle. A tally sheet resulted.
Results of this tally sheet, in excesses of crosses or dots, had to be
written diagonally on a rectangle sheet in accordance with standard procedure
for forming rectangles.
The present Garbo method results in a similar tally sheet, but
the cycles have been combined in groups of five so that there are less tallies
in each cell to contend with. Suppose a Delta Z1&2 rectangle is desired
from 11,000 letters of Z. A Z1&2 tape is made on Mrs. Miles (a machine to
be described) showing the 11,000 Zl&2 characters divided into 5 levels:
Level 1 1 2 . . . . . . . 1271 . . . . . . . . 2542
Level 2 2543 2544 . . . . . . . 3813 . . . . . . . . 5084
Level 3 5085 . . . . . . . . 6355 . . . . . . . . 7626 < - Z1&2 text
Level 4 7627 . . . . . . . . 8897 . . . . . . . . 10168
Level 5 10169 . . . . . . END(11,000) .
(5*1271) < (11,000 < 2*(5*1271) so the tape is 2*1271 long.
If the text length is expressed as k.5.1271, the tape will be k.1271 long.
The above tape is now passed through Garbo which deltas it as it
goes through, and prints:
If Delta Z1<2 = Value printed:
/ (no crosses) - zero
E,4,9,3,T (1 cross letter) -l
two cross letters -2
three cross letters -3
4 cross letters -4
8 (5 crosses) -5