Baille, Jean Baptiste Alexandre, b. 1841, Armstrong, John W., ed · New York, Scribner, Armstrong, and co. · leaf 66
IN TELEGRAPHY. 47 that a message is about to be delivered. It istherefore necessary to call his attention by somemeans, when a despatch is about to be sent. Forthis purpose an alarm bell is employed. As earlyas the year 1837 bells were used for this purposein the first system of telegraphy… … The Bell. this difficulty led to the invention of relays. Thereare now as many different kinds of bells as thereare systems of telegraphy. But the alarm bell isthat which is most frequently made use of, espe-cially in France. It consists of an ordinary electro-magnet, the armature of which…
Electricity
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
![An illustration from [Electric engineering.] (1902)](https://img.insideoutlibrary.com/img/200/ia-electricengineer02inte-261-135.webp)
