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2020-11-19 23:23:03
Shannon, Claude E
Memory Requirements in a Telephone Exchange
New York: Bell Telephone Laboratories, Inc, 1950. First Separate Edition. Wraps. Fine. First Separate Edition. 1-7, [1-blank] pages. 21.3 x 27.5 cm (8 3/8 x 10 7/8 inches). Stapled wrappers, printed in grey, light blue, and black. 5 hole punched at the spine, as issued. The first separate edition. A bright clean copy. Wraps. This is the first separate edition, published in the Bell Telephone System Technical Publications Monograph series, #1758. The research paper was first published in the Bell System Technical Journal, Vol 29, July, 1950, pages 343-349."The basic function of an [ telephone ] exchange is that of setting up a connection between any pair of subscribers. In operation the exchange must 'remember' in some form which subscribers are connected together until the corresponding calls are completed. This requires a certain amount of internal memory, depending on the number of subscribers, the maximum calling rate, etc." (first paragraph)Shannon derives a formula M = 2S log N and interprets it in terms of information theory (utilizing his seminal paper 'A Mathematical Theory of Communication'). Today we might wonder why knowing how much memory a telephone exchange needs was important. In the 1950s central office telephone switches (the machines that ran the telephone network in cities or large companies) were mostly mechanical or electromechanical. Their electrically connected components (look up Strowger or Crossbar switches for more information) allowed just basic call connections.Shannon's paper created the theory that enabled engineers to properly siz … [Click Below for Full Description]
Bookseller: Kuenzig Books, ABAA [United States]
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