We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
AMPLIFIER COMPONENT PARTS 269
functioned quite satisfactorily under extraordinary conditions of temperature, pressure, and acceleration.
The war also brought about the development of rugged glass-envelope vacuum tubes capable of withstanding 20,000 g linear acceleration and 5000 g radial acceleration*; these were used in tremendous quantities in the manufacture of the proximity fuze — a shell fuze that contained a miniature radio transmitter and receiver for controlling the detonation of the shell. Many of these war-learned lessons have been carried over into peace-time manufacture.
For most ordinary purposes, it is considered desirable but not necessary for sound-film recording equipment to meet the rigid performance requirements set for military amplifiers and the like. The latter was excellent in performance consistency ; it was, however, quite costly and quite bulky. Engineers all agree that it is ' ' the right way to build equipment, ' ' but their sales engineers feel that a competitive market is not prepared to pay the high prices that its construction involves. Unfortunately, too, the quantity in which 16-mm sound-film recording equipment is built is minute when compared with the quantity of military equipment built during the war. On a comparative basis, accordingly, recording equipment will be less reliable and less consistent as well as more costly per pound, because of the absence of the economies resulting from mass production.
Noise may originate in a number of sources in component parts. The first source to be suspected is a defective tube ; hum may also be present because of insufficient filtering of the high or low-voltage supply, but it may also be due to magnetic induction caused by stray magnetic fields " sprayed" by transformers, reactors, motors, and the like. In good equipment, power transformers and reactors are designed to operate at low flux densities and with special features of magnetic circuit design to reduce stray flux to a minimum. Special magnetic shields made of nickel-iron alloys such as permalloy, Allegheny metal, Mu metal, Nu metal, Hipernik, etc., are placed around audio transformers and other inductive circuit components such as reactors and equalizer coils to minimize the voltages induced by stray fields that may occur. Generally speaking, the stray fields produced by alternating current motors (such as the motor on the sound-recording machine) are the worst offenders in "spraying" stray flux about; reactors and power transformers come
* The term " g," when used in connection with acceleration, refers to the acceleration of gravity: vis., 32.2 ft. per second per second (ft./sec.2).