The audio-visual handbook (1942)

Record Details:

Title:
The audio-visual handbook
Date:
1942
Publisher:
Chicago : Society for Visual Education, Inc.
Volume:
The audio-visual handbook
Leaf #:
000161
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Niles Essanay Silent Film Museum
Sponsor:
Media History Digital Library
Coordinator:
Media History Digital Library
Description:
Date Added:
March 21, 2024
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Types of Sound Aids for Schools 143 when and as needed. This equipment ranges in price from SI 10 to $150, complete. Also, special record-playing attachments are available for use with radio receiving sets, public-address equipment, and sound motion-picture projectors. Photo Courtesy RCA Manufacturing Co., Inc. Two-Speed Phonograph An explanation of the difference between phonograph records and transcriptions (radio recordings) seems to be in order at this point. The standard phonograph record is recorded on a recording wax which revolves at the rate of 78 revolutions per minute. As the wax revolves at this rate, the sound is registered in undulating lateral waves in spiral grooves of which there are approximately 100 to the inch. The average ten-inch phonograph record can accommodate a maximum of approximately three minutes and fifteen seconds of recording on one side. A twelve-inch record can be used for a recording period of approximately five minutes. The process of making a transcription record is approximately the same, except that the transcription wax revolves at the rate of 33 1/3 revolutions per minute, making it possible to record for fifteen minutes on one side of a sixteen-inch disc or for ten minutes on one side of a twelve-inch disc. In either case, pressings are made after due processing and the resulting records, or transscriptions, must be played on instruments which revolve the record