I was wondering how the allied (America and England, since France was occupied by the Nazis) communicated securely with each other in 1943. I know that the SIGSALY existed, but I am most interested in how Roosevelt's and Churchill's telegrams were encrypted. Did they use the British Typex or the American SIGABA?
The communications between national leaders are normally conducted through the embassies. I.e., Churchill would send a Typex-encrypted telegram to the British Embassy in Washington, DC, it is decrypted there, and delivered in person to the White House. Similarly, Roosevelt would send a SIGABA-encrypted message to the US Embassy in London, it is decrypted there and delivered in person to Number 10. (Cold War required faster decision making, necessitating Moscow-Washington hotline).
The direct communications between the militaries were conducted via Combined Cipher Machine starting 1943-11-01.
The machine looked like a typewriter (all of them did, including Enigma) and was operated by a technician.