Patent specification 148,582 . . . improvements in ionic relays

Patent for the Flip-Flop Circuit, the Basis for Electronic Memory Eccles, William Henry (1875-1966) and Frank Wilfred Jordan (1882- ). Patent specification 148,582 . . . improvements in ionic relays. [Redhill: Printed for His Majesty’s Stationery Office by Love & Malcomson, Ltd., 1920.] 5pp. Folding plate. Errata slip tipped to first leaf. 267 x 195 mm. Unbound. Light wear along gutter margin and fore-edge, but very good. Stamps of the Belgian Bureau voor den Industrieelen Eigendom Bibliotheek. First Edition. On June 21, 1918 British physicists William Henry Eccles and Frank Wilfred Jordan, professors of engineering at London’s City and Guilds Technical College, filed a patent for "Improvements in Ionic Relays"—the first flip-flop circuit. The device, originally called the Eccles–Jordan trigger circuit, consisted of two active elements (vacuum tubes). The schematic drawing illustrating Eccles and Jordan’s patent shows two flip-flops, "one drawn as a cascade of amplifiers with a positive feedback path, and the other as a symmetric cross-coupled pair" (Wikipedia). The patent specification, no. 148,582, was first published in 1920. Early flip-flops were known variously as trigger circuits or multivibrators. A flip-flop circuit has two stable states and, as Claude Shannon pointed out in his Mathematical Theory of Communication (1948), can be used to store one bit of information. Flip-flop circuits operate using Boolean algebra (AND, OR, NOT). Prior to the invention of electronic computing Eccles and Jordan viewed their invention as a "method of relaying or magnifying in electrical circuits for use in telegraphy and telephony." However, with the invention of electronic computing that used vacuum tubes as switches, flip-flops became the basic storage element in sequential logic used in digital circuitry, and the basis for electronic memory. In September 1919 Eccles and Jordan described the flip-flop in a brief one-page paper, "A trigger relay utilizing three-electrode thermionic vacuum tubes" (The Electrician, 83, [September 19, 1919], p. 298). However, the patent, filed the previous year and consisting of 5 pages plus illustration, remains the first description of this invention. Very rare. .…