APPARATUS FOR THE TRANSMISSION OF SOUNDS BY ELECTRICITY THROUGH WIRES OR OTHER CONDUCTORS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by James Alfred Ewing and Fleeming
Jenkin at the Office of the Commissioners of Patents on the 22nd November
1877.
JAMES ALFRED EWING, Engineer, residing at 22, India Street, Edinburgh, and
FLEEMING JENKIN, Professor of Engineering in the University of Edinburgh,
residing at 3, Great Stuart Street, Edinburgh. " APPARATUS FOR THE TRANSMISSION
OF SOUNDS BY ELECTRICITY THROUGH WIRES OR OTHER CONDUCTORS."
The object of this Invention is to produce a telephone which shall be simple and
powerful, and which shall also be suited for the transmission of two or more
simultaneous messages in either direction along the same wire or part of the saine
wire.
The transmitting and receiving instruments are similar in construction; they
consist in one form of the instrument of a wire or wires, capable of vibrating to
definite musical notes, and so stretched with or without resonators in a magnetic
field, as to vibrate when in action across the lines of magnetic force. The tele-
graphic circuit consists of these wires, the line, and the earth; the circuit is never
interrupted. The wires are tuned so that one wire or one group of wires at each
end is in unison with one wire or one group of wires at the other. The electrical
currents caused by vibrations of one wire or group pass along the line, and give rise
to corresponding vibrations in one wire or group at the receiving end. When one
wire or group is made to vibrate at the sending end, the wire or group tuned in
unison will vibrate at the other end, but the other wires or groups will remain
practically silent. By having a number of pairs or groups, means are afforded of
transmitting independently a number of audible signals at the same time along
the same line without interference.
The vibrations of the wires at the sending end may be produced either directly
by blows or otherwise, or indirectly by causing sounds to be made in their neigh-
bourhood. The telegraphic circuit is constant; the sending and receiving wires
are both included in the circuit, and no magnet has its magnetism sensibly changed
by the sending of signals.
A second form of the Invention is an inversion of the arrangement described
above. Instead of a wire or wires vibrating across the lines of magnetic force of a
fixed magnet, a magnet in the form of a fork or plate may be caused by a blow or

page_text: sound in the neighbourhood to vibrate like a tuning fork, and in such a manner as
to carry its lines of force across a wire or wires, fixed and forming part of the circuit.
The electrical currents produced in this manner are conveyed to the other end of the
line where they pass through an apparatus similar to that at the sending end, and
so produce corresponding vibrations of a magnet in the form of a plate or fork at
the receiving end.
Several instruments may be in circuit at each end of a single line; one magnet at
each end being tuned so as to vibrate in unison with one magnet at the other end.
By this means several independent sets of signals may be transmitted simultaneously,
as by the form of the apparatus previously described.
Either form of apparatus may also be used for the transmission of articulate
sounds by the use of only one instrument at each end, and by supporting the wires
or magnets of that instrument so that they do not vibrate freely and have no
special musical note of their own.