A miniature microphone for transistorized amplifiers

A new magnetic microphone has been developed for use in hearing aids and communication and similar equipment which requires a small, light, medium-impedance microphone. The new microphone has a diameter of 1 inch and a thickness of 3/8 inch, and i t weighs 9 grams. The sensitivity is high enough to override the relatively high noise level of transistors in the frequency range most useful for voice transmission.