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

ELECTRIC CIRCUITS AND MANIPULATION. 321
simultaneously the two needles upon the same letter. It has
sufficed for this, to prevent the circuit from being closed in the
apparatus at the first station, 1, producing the same results in
effect. The circuit also rests open in the apparatus of the
second station, 2; and neither of the two armatures will be
attracted until the mechanism of apparatus 1 is permitted to
close the circuit.
When the key of the first apparatus is pressed upon, the
escapement wheel is stopped precisely in the middle of the
movement which it was about to make, under the action of the
spring, and the circuit cannot be again closed, until the operator has removed the obstacle by the withdrawal of the finger.
During this time, nothing prevents the escapement of the apparatus of station 2, by its mechanism, from closing the circuit;
but, inasmuch as the circuit is open at station 1, the armature
will not be again attracted, and the indicator of the apparatus,
at station 2, will stop over the desired letter, after the key is
pressed corresponding to the same letter upon the apparatus
at station 1.
In time of repose, when it is not desired to correspond, the
circuit between the two stations, 1 and 2, is formed merely by
the conducting wire, the earth, and the two spools or coils of
the alarum bell. When the operator of station 1 wishes to
communicate with the operator of station 2, he withdraws his
bell apparatus from the circuit, and replaces it by a battery and
his apparatus for telegraphing. Immediately, the bell of the
station 2 gives the alarum, but the telegraph apparatus of that
same station remains motionless. It may appear somewhat
surprising, that two similar apparatuses, the telegraph and that
of the bell, can be in the same circuit, the one operating and
the other not operating. This effect is obtained by the unequal
tension of the springs. Suppose, indeed, two apparatuses to be
placed in the same circuit, the recoil spring of the one A is
much stronger, or more tightly stretched than the apparatus
n, thus, when the armature of B shall have been attracted, the
electro-magnet A will not have acquired the force necessary to
counterbalance the action of the spring. This result is owing
to the difference as to tension in the recoil springs, the one being more susceptible and elastic than the other. The armature
of A will remain firm and motionless, and the circuit constantly
closed on that side. The apparatus B will alone move. It will
be understood, then, that, from what actually takes place, the
springs of the bell alarums are feebler than those of the telegraph. The bells will be sounded at each station, by the action of the battery of the other station, while the telegraphs will
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