## Captain Walter Fried's Fish Notes March 1944 to January 1945## Page 3 |
Tony Sale's Codes and Ciphers |

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- 3

- D = de-chi Z + X = P + Psi

a = proportion of crosses in MT

b = proportion of crosses in Delta P

p(.) = probability of dot

p(x.) = probability of crosses

p(.) in Delta(Psi)ij = b^2 + (1 - b^2)

p(.) in Delta(Psi)'ij = (1 - a) + [b^2+ (1 - b^2)]

for eadh of the Psi wheels. Furthermore, a and b are Invariably selected

so that their product is aproximately equal to one-half. Therefore -

- p(.) in Delta(Psi)'ij = b

- P(.) in Delta Pij = 1/2 + lambda

- p(.) in Delta Dij = (1/2 + lambda)b + (1/2 - lambda ) (1 - b)

- = lambda(2b - 1)

cornpiled.

Walter J. Fried

Capt. Signal Corps.

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