A miniature tuned reed selector for high sensitivity and stability

This paper describes a selective contacting device that is responsive only to sustained frequencies in a discrete narrow band and is insensitive to speech and noise interference. It is of small size suitable for use in a pocket carried radio receiver and is sufficiently stable to permit 33 discrete resonant frequencies, spaced 15 cycles apart in less than an octave between 517.5 and 997.5 cycles per second. It has a threshold sensitivity of about 35 microwatts and other operating characteristics that are essential in large capacity systems.