File:The Bell System technical journal (1922) (14755703322).jpg

Identifier: bellsystemtechni06amerrich (find matches)
Title: The Bell System technical journal
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company
Subjects: Telecommunication Electric engineering Communication Electronics Science Technology
Publisher: (Short Hills, N.J., etc., American Telephone and Telegraph Co.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

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Fig. 5—Portable analyzer unit inferred, frequency distortion is a departure of the wave form of theelectrical output from that of the acoustic input due to the fact thatthe transmitter does not respond equally to acoustic forces of the samemagnitude over the frequency range under consideration. Non-lineardistortion is the distortion produced by the fact that the voltage acrossthe transmitter at any particular frequency is not a linear function ofthe magnitude of the impressed acoustic force. This type of distor-tion usually manifests itself by the production of frequency componentsin the electrical output which are not present in the acoustic input.The analyzer may be used for quantitative determinations of this non-linear distortion and in such measurements high frequency discrimina-tion and ability to measure frequency components of widely differentmagnitudes are very valuable. 224 BELL SYSTEM TECHNICAL JOURNAL
Text Appearing After Image:
in tuO ANALYZER FOR THE VOICE FREQUENCY RANGE 225 A number of other uses of the analyzer in acoustic measurementsmight be cited; for instance, the output of a transmitter at one partic-ular frequency may be measured in the presence of room noises or otherdisturbing sounds. In general its high selectivity, convenience ofoperation and portability make the analyzer an extremely valuable in-strument in a wide variety of acoustic and electrical measurements. Appendix Inasmuch as the incorrect operation of the modulator could givefalse indications of frequency components in the wave to be analyzed,it may be of interest to take up some of the more important aspects ofthe theory of the vacuum tube plate current modulator as applied tothis.analyzer. In general, the output of a vacuum tube is of the form I,=Ao + AiE + A^E^ + AsE + A^E + etc., (1) where E is the voltage applied between the cathode and grid of thetube and the coefficients Ao, Ai, A^, A3, etc., depend upon the averagepotential of

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