The Davisson Cathode Ray Television Tube Using Deflection Modulation

HE present day coaxial cable broad-band transmission system was developed during the early 1930's, and was originally conceived as a means for multi-channel telephone transmission. During the same period the rapidly developing television art was producing video signals requiring wider and wider frequency bands. It was very soon realized, therefore, that this coaxial system would also lend itself admirably to the transmission of such wide band television signals. The early development culminated in the installation of a coaxial cable route from New York to Philadelphia. This system was designed to provide 240 telephone channels or a single 800 kc television channel, and both types of transmission were successfully accomplished during a series of demonstrations in 1937.1 The scanning equipment used for producing the television signals for these demonstrations was developed under the direction of Dr. H. E. Ives at the Bell Telephone Laboratories. It was designed to scan standard 35 mm motion picture film and consisted of a six-foot steel disk rotating at 1440 rpm and having 240 lenses mounted around the periphery. It thus produced a television signal of 240 lines and 24 frames per second, occupying a bandwidth of about 800 kilocycles. From this same period came the well known work of Dr. Davisson in the field of electron diffraction.2 This work had resulted also in important advances in electron optics and in the development of the sharply focussed, well defined electron beam. It was natural, therefore, that Dr.