Secret Radio-telephony


    A SCIENCE SERVICE Mail Report dated May 28 states that Dr. S. Chiba, of the Tokyo Electric Co., has developed a secret method of radio-telephonic communication. According to the description, the sending installation employs a microphone so constructed that the speech current is inverted with respect to frequency, so that it is unintelligible to the listener on an ordinary receiver. At the receiving end of the communication channel an equipment is used to turn the speech back to normal. From these brief details, it would appear that the system is similar to the inverted-speech method employed by the British Post Office for securing secrecy, as an alternative to the speech-scrambling method which has also been developed and used by the Post Office in long-distance radio-telephonic communication.

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    Secret Radio-telephony. Nature 134, 58–59 (1934).

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