Application of Touch-Tone calling in the Bell system

A new system of initiating telephone calls employing voice-frequency tones, controlled by actuating buttons, and known as “Touch-Tone Calling” is now in service on a trial basis. The resultant marked improvement in speed and ease of use appears to appeal strongly to telephone users. This system is described and the engineering and psycho-physical steps necessary to its development are outlined. Field tests of system feasibility and results obtained are discussed. Three companion papers present technical features of the system components.