Applications of touch-tone calling
M. L. Benson, Floy L. Crutchfield, H. F. Hopkins · Electrical Engineering · 1962
“Touch-Tone Calling,” a system for initiating telephone calls by means of voice-frequency tones controlled by actuating buttons, is now in service on a trial basis. The resultant marked improvement in speed and ease of use appeal strongly to telephone users. Results of field tests of system feasibility are discussed