Radio Telephony Device

Radio Record, Volume IV, Issue 21, 5 December 1930, Page 29

Radio Telephony Device

To Prevent Eavesdropping -- ECAUSD of criticisms concerning the absence of privacy in long-dis-tance radio telephony conversations, an interesting device has been perfected which prevents any intelligible reception of the signals by unauthorised persons. By the system adopted, the component parts of speech are split up intq portions by an electrical device, and transmitted in a mixed arrangement which conveys nothing intelligible until the parts have been rearranged in their correct form at the distant.end. This system is now in use on most of the inter-continental radio telephony services of to-day.