536 



■D- 



E 



^ 



Fi9 7a DRUM SPEED TIMING DEVICE 



To solenoid on camera 

 1 1 



0005pF Milliommcter 



=!^-*-l2CV 



AC -I6V 



Mains 



Fig 7 b ELECTRICAL CIRCUIT FOR INDICATING FREQUENCY OF 

 VOLTAGE PULSES 



