The Geheimschreiber (secret teleprinter) was used in World War II at the command level of the German Navy and Air Force. The T52b encrypts the 5-bit Baudot code of the teleprinter. The 10 reels are moved irregularly and generate pseudo-random numbers, which are cleared by the plaintext. A scrambler circuit then swaps the 5 encrypted bits around. The T52b was cracked in 1940 by Swedish cryptologists; the British codebreakers only partially succeeded.