The Compandor - An Aid Against Static in Radio Telephony

W H E N the original New York-London long-wave radiotelephone circuit was designed, it was recognized that radio noise would often limit transmission, especially for the weaker voice waves. Accordingly provision was made for manually adjusting the magnitude of the speech waves entering the radio transmitters to such a value as to load these transmitters to capacity.1 While this treatment was very effective in improving the average speech-to-noise ratio and in preventing the strong peaks of speech from overloading the transmitter, it was, of course, unsuitable for following the rapidly varying amplitudes of the various speech sounds. The total range of significant intensities applied to the circuit is in the order of 70 db, an energy ratio of 10 million to one. The manual adjustments referred to above were succesful in reducing this range to about 30 db. To further reduce this residual range an interesting Published in * Presented at S u m m e r Convention of A. I. E. E., June, 1934. Electrical Engineering, J u n e , 1934. 315