An Experimental Polytonic Signaling System

The need in future telephone systems for a signaling method of significantly higher speed that that provided by the familiar dial or even by the intertoll multifrequency system 1 has led to a research program in high speed signaling. The program has resulted in laboratory models of several experimental systems based on different principles. This paper describes one of these systems, based on the concept of orthogonal functions. Several different frequencies are used, in combinat ions, to transmit signal information. The means of generating and recognizing these frequencies represent a departure from present practice; in order to distinguish this experimental system from the multifrequency system, the term polytonic was coined. It is hoped that this paper provides an interesting illustration of the way a mathematical conception may be transformed, through successive stages, to a physical system. 1 C. A. Dahlbom, A. W. Horton and D. L. Moodv, Application of Multifrequency Pulsing in Switching, Trans. A . I . E . E . , 68, pp. 392-396, 1949.