Electricity for public schools and colleges . form ofgalvanometer in oppositedirections, we can give tothe needle deflexions inopposite directions respec-tively. On this principleis constructed the com-mon needle telegraph,of which one form isshown in fig. iii. Herethe coils and the needleare both vertical, andthe motion of the needleis limited by two ivorystops. In fig. iv. we seeat the base of the instru-ment the commutating key by means of which the current canbe made or broken, and sent in either direction. The currentpasses first through the sending instrument, deflecting its needlein one
Electricity for public schools and colleges . form ofgalvanometer in oppositedirections, we can give tothe needle deflexions inopposite directions respec-tively. On this principleis constructed the com-mon needle telegraph,of which one form isshown in fig. iii. Herethe coils and the needleare both vertical, andthe motion of the needleis limited by two ivorystops. In fig. iv. we seeat the base of the instru-ment the commutating key by means of which the current canbe made or broken, and sent in either direction. The currentpasses first through the sending instrument, deflecting its needlein one or the other direction. It passes thence through the linewire, and afiects in a corresponding manner the needle of thereceiving instrument. • By means of a suitable code both this and the last instrumentare used to transmit verbal messages. § 3. Telegraphic Alphabets.—In all those instruments thatare in extensive use there are only two elementary signals : the dot^to which we agree to consider a deflexion to the left to be the £ £ 2. Fig. iv. 420 ELECTRICITY CH XXV. corresponding signal in the needle instrument ; and the dash, towhich corresponds the deflexion to the right of the needle. The signals answering to the letters of the alphabet are variouscombinations of the above elements, the only principle observedbeing that simple signals shall represent constant recurring letters. se;gt:e SKGra PKrvTDTG. >1XDLE. PETNTCCG. ^?EEDIE. A _ .. s/ N /. B As^ 0 I/I C AA p Jls D As Q l/J E - N R Js F uA S WS G /A T 1 H WW U .si I -- \\ V sssi J J// w sll K Is/ X IssI L _ sL Y A// M II Z /An This system is .called, from its inventor, the Morse code. Thereader will notice how readily this code, intended originally fordots and dashes in the Morse instrument described in § 5, adaptsitself to other methods of signalling ; as by the needle instrument,by the voice, by flashes of light, by flags, &:c. § 4. The Needle System of Telegraphy.—\\& will now de-scribe briefly the simple
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Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjectelectricity
