7774th Signal Battalion
(Source: Jack Emanuelson, 1954)
I have a couple of pictures of some of the crypto devices that we used to use. The first (below) is the SIGABA/AFSAM-1/M-134-C/CSP2900. The shot shows an operator with two machines in tandem. Probably one for encryption and one to decryption, using a cable between the two. The machines are on display at the Cryptologic Museum outside of Fort Meade, Maryland, that is open to the public.