F. H. Richardson's bluebook of projection (1935)

Page scan 000488 from F. H. Richardson's bluebook of projection

Record Details:

Title:
F. H. Richardson's bluebook of projection
Date:
1935
Publisher:
New York : Quigley Publishing Company, Inc.
Volume:
F. H. Richardson's bluebook of projection
Leaf #:
000488
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
{"Media History Digital Library","Jeff Joseph"}
Coordinator:
Media History Digital Library
Description:
Date Added:
August 01, 2024
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CHAPTER XXIV THE A C TRANSMISSION LINE (1) When a. c. is transmitted over a pair of wires, one of the most important requirements of the circuit is that the impedance (see Page 468) of the apparatus from which the current comes shall match the impedance of the apparatus to which the current is led. (See CO/L COIL A Figure 106 3 Impedance Match Figure 106 represents a very simple a. c. transmission line, in which we assume that the source of the current is coil A. Coil A may be, and in sound equipment usually is, the secondary winding of a transformer. Coil B may be the speech winding of a loud speaker or the primary winding of an input transformer or other apparatus. In any case, the impedances of A and B should be identical. There are a very few exceptions, none of which need concern the projectionist. (2) We can most easily understand the necessity for impedance match between A and B by assigning numerical values to their action. Let us assume that A has an impedance of 1000 ohms and that it is the secondary of a transformer developing 100 volts. Now assume that the impedance of B also is 1000 ohms. Let us calculate the amount of power transferred from A to B. The total voltage of this circuit is 100, of which 50 470