## Transmission of Information in Bell System Technical Journal 7, 1928, pp. 535-563

New York: American Telephone and Telegraph Co, 1928. 1st Edition. FIRST EDITION OF RALPH HARTLEY'S FOUNDATIONAL PAPER ON INFORMATION THEORY -- work that was "the single most important prerequisite" for Shannon's theory of information" (Wikipedia). Shannon acknowledged his debt to Hartley in the first paragraph of his landmark 1948 paper "A mathematical theory of communication," -- the paper in which Shannon introduced a qualitative and quantitative model of communication that solved the problem of reproducing at any given point a message originating at another point. Hartley had a way of thinking philosophically about the transmission of information, a habit that led to his unconventional method of formulating the problem of communication. Hartley "regarded the sender of a message as equipped with a set of symbols (the letters of the alphabet for instance) from which he mentally selects symbol after symbol, thus generating a sequence of symbols. He observed that a chance event, such as the rolling of balls into pockets, might equally well generate such a sequence" (Pierce, An Introduction to Information Theory, 39). "Hartley distinguished between psychological and physical considerations -- that is, between meaning and information. The latter he defined as the number of possible messages independent of whether they are meaningful. He used this definition of information to give a logarithmic law for the transmission of information in discrete messages: H = K log sn where H is the amount of information, K is a constant, n is the number of symbols in the message, s is the size of the set of symbols and therefore sn is the number of possible symbolic sequences of the specified length n. Hartley had arrived at many of the most important ideas of the mathematical theory of communication: the difference between information and meaning, information as a physical quantity, the logarithmic rule for transmission of information, and the concept of noise as an impediment in the transmission of information" (Origins of Cyberspace 316). Hartley's research led him to formulate the law upon which Shannon built, "that the total amount of information that can be transmitted is proportional to frequency range transmitted and the time of the transmission" (Wikipedia). Together with Shannon's work, the law became known as the Shannon-Hartley theorem. Item #314

CONDITION & DETAILS: New York: American Telephone and Telegraph Company. Bell System Technical Journal 7, 1928, pp. 535-563. Illustrations throughout. The Hartley paper includes 7 illustrations, two photos and five figures. Full volume. Quarto. (9 x 6.25 inches; 225 x 156mm). Solidly and tightly bound in dark blue cloth; gilt-lettered at the spine. "P. Caporale" appears in small gilt in the lower right corner of the front board. Very slight scuffing around the edge tips; clean and bright inside and out. Very good condition.

Price: \$850.00