Cinematographic annual : 1930 (1930)

Record Details:

Title:
Cinematographic annual : 1930
Date:
1930
Publisher:
Hollywood : The American Society of Cinematographers, Inc.
Volume:
Cinematographic annual : 1930
Leaf #:
000416
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
{"Media History Digital Library","Richard Koszarski","Jeff Joseph"}
Coordinator:
Media History Digital Library
Description:
Date Added:
March 21, 2024
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396 CINEMATOGRAPHIC ANNUAL of the bridge is pure resistance D with an impedance equal to the impedance of the capacity and inductance at 720 cycles, hence the ratio of the resistance D to C and L is unity at this frequency. The other two arms of the bridge circuit is the primary of FIGURE 11 T4 divided at its half tap. A 720 cycle potential is supplied from a small alternator when it is driven at 1200 R.P.M. This alternator is directly connected to the shaft of the main driving motor. When the speed is less than 1200 R.P.M. the applied potential across the bridge circuit is less than 720 cycles, hence the current in C is leading due to the predominance of the condenser, and if the frequency goes over 720 cycles, the current is lagging due to the predominance of inductance. Hence with a change of speed there is a change of 180° phase from less than 1200 R.P.M. to more than 1200 R.P.M. This shift of phase changes the potential of the grid of V4 relative to the plate from negative to positive or vice versa, and thereby causes a