566 BELL SYSTEM TECHNICAL JOURNAL 



With this large collecting area and the strong light intensity that 

 can be used for the transient illumination, the cells give an electrical 

 output that, though still extremely small, is safely above the noise 

 level of an amplifier system. 



Fig. 5 — Television transmitting apparatus. Sweeping beams of light pass out 

 through the tunnel-like opening in the photoelectric cell case; light reflected from 

 the subject is collected by three large photoelectric cells behind the screened openings. 



A photograph, Fig. 5, shows the details of a television transmitting 

 station as it is operated in the field. The arc, rotating disk and 

 photoelectric cells are contained in separate cabinets and aligned as 

 shown in the photographs. The three photoelectric cells and first 

 stages of amplification are mounted in a shielded, sound-proof case. 

 The slender, sweeping beam of light coming from the disk cabinet 

 passes through the tunnel-like opening in the photoelectric cell case 

 and scans the subject seated in front of it. The apparatus sees the 

 person from light reflected back into the three large cells located 

 just behind the screened openings in the case. 



The variations of the feeble picture currents delivered from these 

 photoelectric cells are highly amplified and transmitted over a wire 

 or radio channel of communication by circuits described elsewhere in 



