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BELL SYSTEM TECHNICAL JOURNAL 



In the theater projector, the sound gate is located 14.5 inches 

 below the picture gate, in order to project the sound record at a 

 point where the film is in continuous motion. Therefore in the 

 printing it is arranged to print the sound negative displaced along 

 the length of the positive enough to bring the sound 14.5 inches ahead 



RUNNING 



direction 

 [emulsion up] 



NOTE: 

 in printing, the sound 



is displaced 14.5" AHEAD 

 OF THE PICTURE WITH WHICH 

 IT IS SYNCHRONIZED. 



243" 



IOO"SOUND TRACK 



LIGHT BEAM WIDTH .OSOU 

 THICKNESS .001 " 



CENTER LINE OF 

 APERTURE PLATE 



098"TENSION PAD 



APERTURE PLATE 



Fig. 5 — Picture and sound track dimensions of synchronized sound film for standard 

 35 mm. positive stock. 



of the corresponding frame. The printer apertures are chosen to 

 give a dark no man's land 17 mils wide between picture and sound 

 track; the latter at the outside is separated 4 mils from the inner 

 perforation edge. 



Fig. 5 exhibits the present practice for the finished positive. It will 

 be seen that the sound track covers 100 mils clear, and is illuminated 



