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BELL SYSTEM TECHNICAL JOURNAL 



which rotates the cams in the direction of the arrow. After a pre- 

 determined amount of film has been advanced, cam 3 rebiases the line 

 relay and restores it to the original non-operated condition (unless the 

 disturbances on the line continue beyond this time). This releases 

 relay SR but the cams continue to turn because the contact operated 

 by cam 1 is in parallel with that on the relay, which allows the motor 



Fig. 15 — Schematic arrangement of continuous-film oscillograph with sequence 

 switch, line-relay, and clock, arranged for automatic operation. 



to run during one complete revolution of that cam. When the line- 

 relay is restored the film stops and the lamp circuit is opened. After 

 cam 3 stops the recording and resets the line-relay, cam 2 operates the 

 camera shutter which photographs the clock on the film at the end of 

 the oscillograms. As the cam shaft continues to revolve, cam 4 

 operates the magnetic clutch for a short time without lighting the lamp. 

 This advances the film far enough so that the beginning of the next 

 record will not be superposed on the image of the clock. When the 

 cam shaft has completed one revolution, cam 1 stops the sequence 

 switch motor by opening the contact associated with it. 



After this sequence of operations everything is exactly the same as 

 before except that a certain length of film has been advanced into the 

 used-film magazine and a complete record made up on it. The length 

 of the record may be adjusted by an adjustment of cam 3. 



In case the disturbance lasts until after the amount of film allotted 



