Telepherage.
An electric transportation system, hitherto only used for the carrying
of ore, freight, etc. Its characteristic feature is that the electric
conductors, suspended from poles, supply the way on which carriages
provided with electric motors run. The motors take their current
directly from the conductors.
There are two conducting lines, running parallel with each other,
supported at the opposite ends of transverse brackets on a row of
supporting poles. At each pole the lines cross over so that right line
alternates with left, between consecutive pairs of poles.
The cars are suspended from pulleys running on one or the other of the
conductors. A train of such cars are connected and the current is taken
in near one end and leaves near the other end of the train. These
current connections are so distant, their distance being regulated by
the length of the train, that they are, for all but an instant at the
time of passing each of the poles, in connection with segments of the
line which are of opposite potential. To carry out this principle the
distance between contacts is equal to the distance between poles. Owing
to the crossing over of the lines the contacts are in connection as
described and thereby the actuating current is caused to go through the
motors.
Cars running in one direction go on the electric conductors on the one
side, those running in the other direction go on the other conductor.
A great many refinements have been introduced, but the system has been
very little used.
Telephone.
An instrument for the transmission of articulate speech by the electric
current. The current is defined as of the undulatory type. (See Current,
Undulatory.)
The cut shows what may be termed the fundamental telephone circuit. A
line wire is shown terminating in ground plates and with a telephone in
circuit at each end. The latter consists of a magnet N S with a coil of
insulated wire H surrounding one end. Facing the pole of the magnet is a
soft iron diaphragm D, held in a frame or mouthpiece T. Any change of
current in the line affects the magnetism of the magnet, causing it to
attract the diaphragm more or less. The magnet and diaphragm really
constitute a little electric motor, the diaphragm vibrating back and
forth through an exceedingly short range, for changes in the magnetic
attraction.
The principle of the reversibility of the dynamo applies here. If the
magnet is subjected to no change in magnetism, and if the diaphragm is
moved or vibrated in front of its poles, currents will be induced in the
wire bobbin which surrounds its end. If two such magnets with bobbins
and diaphragms are arranged as shown, vibrations imparted to one
diaphragm will send currents through the line which, affecting the
magnetism of the distant magnet, will cause its diaphragm to vibrate in
exact accordance with the motions of the first or motor diaphragm. In
the combination one telephone represents a dynamo, the other a motor.
If the vibrations of the diaphragm are imparted by the voice, the voice
with all its modulations will be reproduced by the telephone at the
distant end of the line.