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

378 FROMENT'S ALPHABETICAL AND WRITING TELEGRAPH.
Fig. 10.
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through an angle proportional to the length of the helix comprised between the two keys, which have successively stopped
the movement.
Fig. 11.
< a A
In this way, if the arbor A bears an electric interrupter, or
circuit-breaker, which opens and closes the circuit every time
that a tooth of the ratchet-wheel passes, the effect produced by
this mechanism upon an electrical current, will be identical to
that produced by the rotation of a telegraphic dial, having as
many signals as there are keys in this apparatus, but with very
perceptible advantages.
The rotations of the arbor A being uniform, are regulated according to the greatest velocity that the receiving apparatus is
capable of executing. When a uniformity is once established,
between the transmitting and the receiving apparatus, it will
continue indefinitely to exist, independent of any irregularity
in touching the keys; provided, of course, that the needle is
allowed time to pass over the divisions of the dial, and this time