Secraphone Secure Phone

Scrambler telephone handset for privacy unit (later known as Secraphone), c.1941, first developed for government and military use as a secure telephone system and issued by the General Post Office (GPO) in the UK around 1937. British Prime Minister Winston Churchill used this telephone system, later known as Secraphone, during the Second World War for secret communications within the British government and military. This scrambler telephone was first developed for government and military use as a secure telephone system and issued by the General Post Office (GPO) in the UK around 1937. This telephone set was used in combination with a large external box known as a privacy unit. The privacy unit used electronic circuits and radio valves to scramble outgoing telephone calls and unscramble incoming calls. Early privacy units suffered from reliability and security problems and could only deter a casual listener. The design was improved and made more secure later in the war.