An elementary book on electricity and magnetism and their applications . Samuel F. B. Morse (1791-1872J. An American artist and inventor, was born at Charlestown (now part of Boston),Massachusetts, was graduated at Yale College in 1810, and in 1832 inventedthe commercial telegraph and the dot-and-dash alphabet known by his 1844 by the aid of a 830,000 grant from Congress he built the first com-mercially successful telegraph line between Washington and Baltimore. ELECTRON AGNET1SM 103 ARMATURE CONTACTPOINTS ELECTRO MAGNET. Fig. 61. — Telegraph relay. many turns of fine wire on their mag
An elementary book on electricity and magnetism and their applications . Samuel F. B. Morse (1791-1872J. An American artist and inventor, was born at Charlestown (now part of Boston),Massachusetts, was graduated at Yale College in 1810, and in 1832 inventedthe commercial telegraph and the dot-and-dash alphabet known by his 1844 by the aid of a 830,000 grant from Congress he built the first com-mercially successful telegraph line between Washington and Baltimore. ELECTRON AGNET1SM 103 ARMATURE CONTACTPOINTS ELECTRO MAGNET. Fig. 61. — Telegraph relay. many turns of fine wire on their magnets. Thus they may besatisfactorily operated on as little current as eight or tenmilliamperes.* These in-struments are called relays(Fig. 61). Reading signals directlyfrom a relay is not usuallyattempted, as the motionof its armature is so deli-cate that it makes verylittle sound, but the arma-ture and one of its stopsare arranged as a part of a local circuit which contains a sounderand a couple of gravity cells (Fig. 62). As the relay armature moves back and Line forth it makesand breaks thelocal circuit andreproduces in itthe signals whichpass over themain line. Thesounder in thelocal circuit givesthe signals ex-actly as theypass over theline. The tele-graph circuitsused in thiscount ry are keptclosed when not in use. Therefore closed-circuit cells,that is, cells with continuous depolarizing qualities, must be * A milliampere is one one-thousandth of an ampere.
Size: 2098px × 1191px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
