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

FRENCH TELEGRAPH-RECEIVING INSTRUMENT. 327
THE RECEIVING INSTRUMENT.
This apparatus comprises almost always two similar systems, so as to be able to operate with two needles.
D G E, D/ C/ E, fig. 1, are the two indicating needles,
made of mica, blackened on the side which marks the signal.
They are fixed by simple friction on the axis c and c'. G
and G' are squares which correspond to the little barrel, and
serve to wind up the clockwork. F and F' the axis of the
pulleys, which are turned by means of little keys II and I', to
tighten the recoil spring.
A and B, B/ and A/, are the knobs to which are attached
the wires by which the current enters and passes off. The
internal arrangement of this instrument will be seen by figure 2.
Fig. 2.
-4'IT
01 L
The electro-magnet I, instead of being at the upper part,
as in a dial-plate apparatus, rests on the bottom of the case,
and is held by two vertical rods, and a horizontal bar of copper. The soft iron of the electro-magnet may be advanced or
drawn back by means of the screw K. The armature Q M,