The Transatlantic Telephone Room

TheTransatlantic Telephone Room, Cabinet War Rooms

The Transatlantic Telephone Room, to which the computer sized scrambler 'Sigsaly' was connected, created the original hot-line allowing Churchill and the American president to conduct their vital strategic discussions in complete security. Like all the rooms in the complex, this originally had a more humble purpose - it was once a store for brooms and domestic equipment. It was adapted in mid-1943 to house a particularly secret installation.

'Sigsaly' was the code name assigned to the equipment which was developed by the American Bell Telephone Laboratories. 'Sigsaly' was a new version of the relatively easily tapped telephone scrambler.

'X-Ray', codename for the London terminal, was so large it had to be installed in an annexe basement of Selfridges department store in Oxford Street.

Partially enciphered telephone conversations were transmitted by cable from the 'hot-line' to the Selfridges site where it was finally enciphered and sent by radio waves to the President in Washington.