. The Bell System technical journal . 1 1 60 100 200 500 1000 FREQUENCY IN KILOCYCLES PER SECOND Fig. 15—Phase delay of New York-Philadelphia television circuit. which shows the phase delay characteristics of the line, repeaters andequalizers, and of the overall circuit at the frequencies used for trans-mission. Noise or interference is very annoying in television transmission;and pattern, or single frequency interference, is particularly objection-able. The permissible noise or interference depends on the amplituderange of the reproduced picture. During these experiments, it wasfound that a s
. The Bell System technical journal . 1 1 60 100 200 500 1000 FREQUENCY IN KILOCYCLES PER SECOND Fig. 15—Phase delay of New York-Philadelphia television circuit. which shows the phase delay characteristics of the line, repeaters andequalizers, and of the overall circuit at the frequencies used for trans-mission. Noise or interference is very annoying in television transmission;and pattern, or single frequency interference, is particularly objection-able. The permissible noise or interference depends on the amplituderange of the reproduced picture. During these experiments, it wasfound that a substantially linear response could be obtained over asignal current range of about 20 db—a brightness ratio of 10 to 1. 456 BELL SYSTEM TECHNICAL JOURNAL The actual reproduced pictures considerably exceeded this range; infact a brightness ratio of 50 or 100 to 1 was realized. In these testsit was found desirable to hold random interference down about 40 dbbelow the maximum signal, and pattern interference down at least15 db Fig. 16—Photograph of a two million cycle amplifier under development forexperiments on the coaxial cable. The engineers who worked on the system, and outside experts whoobserved it, expressed the opinion that the reproduced pictures inPhiladelphia were substantially the same as those seen on a similarreceiving device in New York, thus showing that the cable systemitself introduced no appreciable distortion. COAXIAL CABLE SYSTEM FOR TELEVISION TRANSMISSION 457 Conclusion As a result of the experimental transmission of the pictures over thecoaxial cable from New York to Philadelphia it has been proved thatwide-band signals of the type required for television can be satis-factorily transmitted over a coaxial cable system, and that in suchtransmission the distortion introduced by the wire line circuits can bemade so small as to be inappreciable, in its effect on the receivedpicture. The work on these very wide-band systems has only begun andrepeate
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