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21 Tyer, Edward
[br]b. 6 February 1830 Kennington, London, Englandd. 25 December 1912 Tunbridge Wells, England[br]English railway signal engineer, inventor of electric train-tablet system for the operation of single-line railways.[br]Use of the electric telegraph for the safe operation of railways was first proposed by W.F. Cooke in the late 1830s, but its application to this purpose and the concurrent replacement of the time-interval system of working, by the block system, comprised a matter of gradual evolution over several decades. In 1851 Tyer established a business making electrical apparatus for railways, and the block instruments invented by him in 1855 were an important step forward. A simple code of electric-bell rings (for up trains; for down trains, there was a distinctive gong) was used by one signalman to indicate to another in advance that a train was entering the section between them, and the latter signalman then operated a galvanometer telegraph instrument in the box of the former to indicate "train on line", holding it so until the train arrived.Even more important was the electric train-tablet apparatus. During the 1870s, single-line railways were operated either by telegraphed train orders, misuse of which led to two disastrous head-on collisions, or by "train staff and ticket", which lacked flexibility since no train could enter one end of a section while the train staff was at the other. At the request of Currer, an official of the Caledonian Railway, Tyer designed and produced his apparatus, in which a supply of discs, or "tablets", was contained in two instruments, one located at each end of a section, and linked electrically: only one tablet at a time could be extracted from the instruments, serving as an authority for a train to enter the section from one end or the other.[br]Bibliography1855, British patent no. 2,895 (block instruments). 1861, British patent no. 3,015 (block instruments). 1878, British patent for electric train-tablet apparatus.Further ReadingC.Hamilton Ellis, 1959, British Railway History, Vol. II: 1877–1947, London: George Allen \& Unwin, p. 199 (describes the development of the tablet apparatus).P.J.G.Ransom, 1990, The Victorian Railway and How It Evolved, London: Heinemann, pp. 157–8 and 164 (describes the block instruments and tablet apparatus).PJGR
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