The cabinet contains material for two telegraph sounders and keys
which will enable the user to establish a short telegraph line with a
single cell of battery. The armature, m, may be lifted from its pivot
so as to permit of slipping one of the coils, A, on to the round
magnetic core of the sounder. The armature is then replaced, as shown
in Fig. 14, and the small retractile spring at the rear of the
instrument is arranged to draw down the shorter arm of the armature
lever. One of the terminals of the coil, A, is connected with the
turned up pivoted end of the telegraph key, o, on the same base. The
other terminal is connected with one pole of the battery and the
contact point of the key is connected with the other pole of the
battery, as shown. By swinging the key laterally, so as to remove it
from the contact point, it will be found that every touch of the key
produces a movement of the sounder lever. To connect the two
instruments together upon a line, it is only necessary to connect the
two keys with one wire and the terminals of the two coils with another
wire, cutting one of these wires and inserting the battery.
[Illustration: FIG. 15.--MAGNETIC FIGURES.]
As soon as the operator ceases to work his instrument he should place
the key in contact with the contact point, and cause it to remain
there by slipping the end of the key under the head of the screw
provided for that purpose. The other operator can then proceed to send
his message.
Those who desire to practice telegraphy should learn the Morse
telegraphic code.