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New York, American Telephone and Telegraph Company, 1927. 8vo. Original full green cloth. Volume VI, 1927 of The Bell System Technical Journal. Library stamp to front free end-paper and title page. Minor bumping to extremities. A nice and clean copy. Pp. 560-603. [Entire volume: (6), 754 pp.]. First edition of the influential paper on television signals. Gray was highly influential in the development of television and conducted pioneering research in this field. "The design of a television system, once the fundamental principles are understood, involves a detailed consideration of the methods by which the several important functions are to be performed.(1) In the present system the initial signal wave is obtained by sweeping a spot of light over the subject in parallel lines completely scanning it once every 18th of a second. The light reflected is collected by large photoelectric cells which control the transmitted current." (From the introduction to the present paper)."A spotlight scanning method was adopted (in the present paper) to illuminate the subject, the beam of light being obtained from a 40A Sperry arc. Three photoelectric cells of the potassium hydride, gas-filled type were specially constructed and utilised to receive the reflected light from the subject. At that time they were probably the largest cells that had ever been made and presented and aperture of 120 square inches." (Burns, R. W. Communications: an international history of the formative years, 2004, p. 497). Other papers of interest contained in the present volume:John Carson:1. Electromagnetic Theory and the Foundations of Electric Circuit Theory. Pp. 1-17.2. Propagation of Periodic Currents over a System of Parallel Wires. Pp. 495-545.E. C. Molina:1. Application of the Theory of Probability to Telephone Trunking Problems. Pp. 461-494.…