about five hundred vibrations per second by an auxiliary battery. Its
vibrations were broken by means of a telegraph key into long and
short periods, representing Morse characters, which were transmitted
inductively from the train circuit to the pole line or vice versa, and
received by the operator at the other end through a high-resistance
telephone receiver inserted in the secondary circuit of the
induction-coil.

The accompanying diagrammatic sketch of a simple form of the system, as
installed on a car, will probably serve to make this more clear.

An insulated wire runs from the metallic layers on the roof of the car
to switch S, which is shown open in the sketch. When a message is to be
received on the car from a station more or less remote, the switch
is thrown to the left to connect with a wire running to the telephone
receiver, T. The other wire from this receiver is run down to one of
the axles and there permanently connected, thus making a ground. The
operator puts the receiver to his ear and listens for the message, which
the telephone renders audible in the Morse characters.

If a message is to be transmitted from the car to a receiving station,
near or distant, the switch, S, is thrown to the other side, thus
connecting with a wire leading to one end of the secondary of
induction-coil C. The other end of the secondary is connected with the
grounding wire. The primary of the induction-coil is connected as shown,
one end going to key K and the other to the buzzer circuit. The other
side of the key is connected to the transmitting battery, while the
opposite pole of this battery is connected in the buzzer circuit. The
buzzer, R, is maintained in rapid vibration by its independent auxiliary
battery, B<1S>.

When the key is pressed down the circuit is closed, and current from
the transmitting battery, B, passes through primary of the coil, C, and
induces a current of greatly increased potential in the secondary.
The current as it passes into the primary, being broken up into short
impulses by the tremendously rapid vibrations of the buzzer, induces
similarly rapid waves of high potential in the secondary, and these
in turn pass to the roof and thence through the intervening air by
induction to the telegraph wire. By a continued lifting and depression
of the key in the regular manner, these waves are broken up into long
and short periods, and are thus transmitted to the station, via the
wire, in Morse charact