IMPROVEMENTS IN APPARATUS FOR RECEIVING AND TRANSMITTING AUDIBLE SIGNALS BY MEANS OF ELECTRICITY
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Arthur French St. George at the
Office of the Commissioners of Patents on the 13th June 1881.
ARTHUR FRENCHI ST. GEORGE, of 40, Southampton Buildings, in the County of
Middlesex. "IMPROVEMENTS IN APPARATUS FOR RECEIVING AND TRANSMITTING
AUDIBLE SIGNALS BY MEANS OF ELECTRICITY,"
My present Invention has for its objects improved methods of constructing and
arranging the parts of apparatus used for receiving and transmitting audible
signals by means of electricity, so that such apparatus is more effective and
economical in its operation than apparatus for the like purposes as ordinarily
heretofore constructed and used.
In order to construct apparatus for the purpose of receiving such signals, I take
a thin circular disc of soft iron, or steel, or a tympan, armature, or other equivalent
device arranged in the ordinary well known way, so that by its vibration it
produces audible signals. Round the outer edge of the disc so arranged, and as
near as possible to one of its faces, I arrange an annular coil of insulated wire
through which a constant local current of electricity is made to pass from a
galvanic battery of any suitable kind or from any other convenient source.
The electricity in its passage through the insulated wire magnetizes or imparts
magnetic polarization to the disc.
At or near the centre of the disc, so as to be at such a distance from the annular
coil of insulated wire already described as not to be affected by the current of
electricity passing through the latter, I arrange one or more electro-magnets,
preferably horse-shoe-shaped, of iron, as soft as possible. The poles of these electro
magnets are arranged in close proximity to the disc, and are fitted with coils of
insulated wire, the ends of which are in connection with the main line wire of the
telephone system to which the apparatus is applied.
When signals consisting of undulating or intermittent currents of electricity are
passed through the insulated wires surrounding the electro-magnet, corresponding
audible signals are induced by the vibration of the disc.
The electro-magnet being of soft iron, instead of steel, magnetized permanently,
or soft iron magnetized by a constant current of electricity passing through its

page_text: coils, causes very much less retardation to the undulatory currents so passing
through its coils from the transmitting apparatus which influences the line circuit
through which telephonic messages are being transmitted.
The retardation caused to the undulatory currents being reduced in the manner
described, as compared with ordinary telephonic receiving instruments, the currents
received are capable of actuating two or more receiving instruments of the novel
kind described, and one or more of such instruments may if desired be put in
communication, by means of flexible or other tubes, with the ears of the person
receiving the message, and the clearness and distinctness of the latter are thus
increased without any correspondingly increased expenditure of electricity.
The coils of insulated wire round the electro-magnet or electro-magnets in the
receiving instrument of the kind hereinbeforo described, instead of being included
in the main line circuit, may be connected to a separato circuit influenced by the
main line circuit by induction. Any suitable form of telephonic transmitting
apparatus may be included in such main line circuit, or in an independent or local
circuit influencing the main line circuit by induction, in such manner that any
electrical pulsations or signals produced when desired, in such local circuit by the
transmitting apparatus, induce corresponding pulsations or signals in the main line
circuit which are transmitted to the receiving instrument in the manner already
described, and are there observed or recorded.
An annular coil of insulated wire may be arranged upon each side of the disc
instead of upon one side only, as first described, and one or more single bar electro-
magnets suitably connected together may be used instead of or in combination
with the horse-shoe-shaped electro-magnets described, and the soft iron bar or bars
constituting the electro-magnet may consist of a solid bar or bars of any desired
shape in section, or of parallel soft iron wires.
Any suitable form of transmitting apparatus may be used. prefer to use
microphones of the kind ordinarily used, in which one or more bars or pencils of
carbon or other suitable semi-conducting material capable of vibration are made to
rest loosely in suitable sockets. I prefer to actuate such microphones, used for the
electrical transmission of speech or other sounds in the way ordinarily known and
practised, by means of resonant tubes of a novel form. For this purpose I take a
tube of sufficient size, of wood or other suitable material, having its ends closed
and a mouthpiece inserted into one such end, so that when sounds produced by the
voice or other means are made at the mouthpiece, the tube is set in corresponding
vibration, and I arrange one or more carbon bars or pencils loosely in sockets
attached to the inner or outer surface of the tube. The wires through which the
electrical variations which cause the signals are to be produced are connected with
the sockets in which the carbon bars rest, and by the vibration of the sides of the
tube and of the carbon, corresponding variations or undulations are produced in
the electrical currents passing through the wires.