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

318 SEIMENS AN-D HALSM1E S:GERMANIC TELEGRAPH.
the plate P1. Each key pressed down, becomes an insurmounltable obstacle to the rotation of the needle, the wheel stops,
and with it the indicator of the dial, as well as the leverarm L Li.
It will be seen, by the preceding, that, at the moment when
the letter indicator attains the middle of a space, the lever-arm
L T. goes toward el, the hook t, places itself in the interval of
the two succeeding teeth. If, then, the indicator is to be
placed before a letter, the lever-arm L L1 must be stopped in its
return toward e, before the nut m arrives in contact with a',
and also before the indicator has reached the middle of the
space at which it ought to stop. For that purpose, the needle A1
is prolonged and inclined, so that it presses against the rod,
sunk by the lowering of the key, before the nut m touches a,,
and before the indicator on the dial has reached the signal at
which it ought to stop. If the finger is taken off the key, the
rod rises, the needle A2 is no longer stopped, the spring detaches
the armature, the nut m presses against a,, a, arrives in contact with e, the current circulates again, and the armature recommences its oscillations.
THE ALARUM BELL APPARATUS.
The alarum bell is represented, in part, by fig. 4. It is comiposed of a new electro-magnet, as seen in fig. 1, E' E',, having
also its armature in the form of an nm reversed.A' a'1, moveable around an axis; this axis bears the lever-arm La' which
Fig, 4,
partakes of the to-and-fro movement of the armature. A
metallic plate, P3, serves as a support to a little foot, upon
which a shuttle n' n' rests, its form being different from that of