The Davisson Cathode Ray Television Tube Using 

 Deflection Modulation 



By A. G. JENSEN 



The paper describes a cathode ray television receiving tube incorporating sev- 

 eral unique features. The tube was designed and constructed by Dr. C. J. Davis- 

 son and was used in some of the early demonstrations of television transmission 

 over the coaxial cable. 



THE 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.^ 



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, occupy- 

 ing a bandwidth of about 800 kilocycles. 



From this same period came the well known work of Dr. Davisson in tHe 

 field of electron diffraction. ^ 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. Ives should 

 discuss with Dr. Davisson the possibility of designing a cathode ray tube 

 capable of adequately displaying a picture from the television signals speci- 

 fied above. The outcome of these discussions was that Dr. Davisson, with 

 the close and able collaboration of C. J. Calbick, undertook to design and 

 construct the tube described in the following pages. In this connection it 

 should also be mentioned that the first experimental samples of the tube 

 were built by G. E. Reitter, while the later engineering for limited produc- 

 tion was carried out by H. W. Weinhart. 



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