Operation Colossus computer

colossus selection panel showing selections amongst others, of far tape on bedstead, , input algorithm: Δz, Δ



χ


{\displaystyle \chi }

, Δ



ψ


{\displaystyle \psi }

.

the newmanry staffed cryptanalysts, operators women s royal naval service (wrns) – known “wrens” – , engineers permanently on hand maintenance , repair. end of war staffing 272 wrens , 27 men.

the first job in operating colossus new message, prepare paper tape loop. performed wrens stuck 2 ends using bostik, ensuring there 150-character length of blank tape between end , start of message. using special hand punch inserted start hole between third , fourth channels 2½ sprocket holes end of blank section, , stop hole between fourth , fifth channels 1½ sprocket holes end of characters of message. these read specially positioned photocells , indicated when message start , when ended. operator thread paper tape through gate , around pulleys of bedstead , adjust tension. two-tape bedstead design had been carried on heath robinson 1 tape loaded whilst previous 1 being run. switch on selection panel specified “near“ or “far” tape.

after performing various resetting , zeroizing tasks, wren operators would, under instruction cryptanalyst, operate “set total” decade switches , k2 panel switches set desired algorithm. start bedstead tape motor , lamp and, when tape speed, operate master start switch.