The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

WHEATSTONE'S MECHANICAL TELEGRAPH. 209
to the difficulties to be encountered, and to avoid all kinds of
hindrances, the telegrapher had to devise many ingenious contrivances.
WHEATSTONE'S MECHANICAL TELEGRAPH.
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The next important improvement was the mechanical telegraph, invented by Prof. Wheatstone, in the autumn of 1839.
It was an escapement apparatus, with one magnet and two
wires, founded upon the principle of giving signals by a revolving dial fixed on the arbor of an escapement wheel, which was
moved by a maintaining power on the removing of an alternating escapement detent, by the alternate attractive force of a
magnet, and the reaction of a spring. Also, moved by the
alternate attractive force of a magnet and reaction of a spring,
without maintaining power, adapted for domestic use. Also,
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