A Touch-Tone caller for station sets
J. H. Ham, F. P. West · IEEE Transactions on Communication and Electronics · 1963
The Touch-Tone caller is a dual-frequency oscillator capable of the generation of any one of 16 combinations of two frequencies under the control of a pushbutton actuated switching mechanism. Initial telephone sets for ordinary services will supply only ten signals. The oscillator design procedure is given and the mechanism is described. The characteristics of special components are discussed. Satisfactory performance of the new caller has been demonstrated in laboratory tests and field trials.