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BELL SYSTEM TECHNICAL JOURNAL 



the electrical control of an impractical amount of light. The picture 

 current itself is distributed by a commutator to successive elemental 

 areas of a large neon lamp. This lamp, as shown in Fig. 9, consists 

 of a single, long, neon-filled tube bent back and forth to give a series 

 of fifty parallel sections of tubing. The tube has one interior electrode 

 and 2500 exterior electrodes cemented along the back side of the 

 glass tubing, Fig. 10. A high frequency voltage applied to the 



Fig. 12 — Details of the distributor. The bars are arranged in four rows each 

 displaced with respect to the other three. The sliding brush is a strip of thin 

 sheet metal. 



interior electrode and any one of the exterior electrodes will cause 

 the tube to glow in front of that particular electrode. The glow 

 discharge actually passes to the inside wall of the glass tubing and 

 the high frequency current flows by a capacity effect out through the 

 glass wall to the exterior electrode. The high frequency voltage is 

 commutated to the electrodes in succession from 2500 bars on a dis- 

 tributor, Fig. 11, with a brush. Fig. 12, rotating synchronously with 

 the disk at a transmitting station. Consequently, a spot of light 

 moves rapidly and repeatedly across the grid in a series of parallel 

 lines one after the other and in synchronism with the scanning beam 

 at the transmitting station. With a constant exciting voltage the 



