The Bell System Technical Journal, 1929, Vol. 8: A Journal Devoted to the Scientific and Engineering Aspects of Electrical Communication (Classic Reprint) - Softcover

Inhaltsangabe

Excerpt from The Bell System Technical Journal, 1929, Vol. 8: A Journal Devoted to the Scientific and Engineering Aspects of Electrical Communication

N 1923 the mile Of standard cable was replaced in the Bell System by a new unit for expressing telephone transmission efficiencies and levels. At that time the generic term transmission unit was taken to designate this new unit, since it was considered desirable to defer the adoption Of a more distinctive name until this unit had been given further consideration by others who would have use for a unit Of this type. This new unit is defined by the statement that two amounts Of power differ by one transmission unit when they are in the ratio of 10-1, and any two amounts Of power differ by N transmission units when they are in the ratio Of In accordance with this, the number Of transmission units corresponding to the ratio of any two powers is ten times the common logarithm Of that ratio.

For a unit Of this kind, it is evidently desirable to have universal use. Accordingly, the Bell System, prior to its adoption Of the transmission unit, discussed this matter with various foreign telephone administrations, and suggested their consideration Of the use' Of the proposed transmission unit. A number of these administrations expressed a favorable attitude towards this unit.

In 1924 there was organized the International Advisory Committee on Long Distance Telephony in Europe. The purpose of this commit tee, which is composed Of representatives of the various telephone administrations of Europe, is to recommend standards and practices for the development of telephone service between the European coun tries. One Oi the early considerations of this committee was this proposal Of the universal standardization of a unit for telephone trans mission work. This brought forth a difference Of view, since some Of the countries represented on this committee wished to continue their use of a unit based on naperian or natural logarithms, for which the basic power ratio is 62. The characteristics Of the unit based on decimal logarithms and that based on natural logarithms and their relative merits were discussed in a number. Of papers which were published at that time and so need not be rehearsed here.

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