1838 __ [The first] Acoustic Telegraph
‣ Comment : Def. an instrument in which code is communicated by sound rather than visually by needles or in print. The earliest was Wheatstone’s magnet and bell of 1841, with a magneto worked by a lever. The American and needle galvanic telegraphs could also receive by sound alone as they made distinctive “dot” and “dash” or “left” and “right” noises. Bright’s Bell of 1858 and the American sounder of about the same date were specifically designed to receive acoustically. (Steven Roberts, “Distant Writing - A History of the Telegraph Companies in Britain between 1838 and 1868”, 2010) — « Nothing is more remarkable among the rage of inventions for communication than the neglect of signs by sound. A few years ago some experiments were made by Biot and Arago, in France, by which they ascertained that the sound by means of tubed could be propagated with almost infinite rapidity ti any distance to which the tube extended. The experiments were made on tubes joined together to upwards of the length of a mile; and, so far as they could discover, if the tubes had been a thousand miles long, the sounds would have been articulated through them with the same immeasurable rapidity. This contrivance may yet be perfected, and we shall have communications passing through the bowels of continents as eaisly as they now pass from a taylor’s counter to his shop-board in the attic. The speaking-trumpet is the only portable contrivance of the kind, but it is a remarkably rude and limited instrument. An attempt at improvement has been lately made in Austria. It is called an Acoustic Telegraph, and is a tube externally resembling a speaking-trumpet, but which is six feet five inches long, and carries the sound to about twelve thousand feet. ». (In Blackwood’s Magazine, 1838) — [In the 1840s], The [Electric Telegraph] Company also offered Wheatstone’s “magnet-and-bell” device to railways and others, such as factories and mines. This consisted of a large finger-pedal or key that worked a horseshoe-shaped magneto; pressing the key produced a single pulse of electricity. The distant receiving instrument was an electro-magnet that attracted the spring-loaded striker of a brass bell. Each stroke of the key had the bell sound once. It was the first commonly used magneto-telegraph, that is one without galvanic batteries, and the first acoustic telegraph. The magnet-and-bell was manufactured until the 1870s for signalling in mines. (Steven Roberts, “Distant Writing - A History of the Telegraph Companies in Britain between 1838 and 1868”, 2010)
‣ Source : Blackwood’s Magazine (1838), In “The Mechanics Magazine, Museum, Register, Journal and Gazette”, Vol. XXVIII, October 7th, 1837 - March 31st, 1838, London : Published by W.A. Robertson, Mechanic’s Magazine Office, Peterborough Court, 1838, p. 198.
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