Scientific research applied to the telephone transmitter and receiver

Improvements in the transmitter and receiver, instruments basic to the telephone art, continually have led to a higher grade of service and further economies. Research work has made possible predetermination of performance by calculation; the effect of studies of speech sounds, hearing, materials, and testing methods on the development of instruments giving high quality for conversation is shown by this article, which is based on one of three Iwadare lectures^∗ delivered in 1937.