IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING 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 26th August 1881.
ARTHUR FRENCH ST. GEORGE, of 40, Southampton Buildings, in the County of
Middlesex. "IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING
AUDIBLE SIGNALS BY MEANS OF ELECTRICITY."
My present Invention relates to apparatus used for the purpose of acoustical
electric telegraphy or telephony, and it has for its objects novel methods of con-
struction and arrangement of such apparatus, so that it is more simple and
effective, and at the same time cheaper in manufacture and working than
apparatus for such purpose as heretofore ordinarily constructed and used.
The first part of my Invention relates to novel methods of constructing and
arranging apparatus for the purpose of transmitting to a distance sounds con-
stituting audible signals through an ordinary electric conducting wire or wires
forming the circuit, and consists in the employment of iron or steel wire in such
apparatus and combining it with the circuit in such manner as to influence the
latter by inductive action; or, on the other hand, in such manner that the circuit
itself shall influence the apparatus either directly or by induction.
I arrange the
iron or steel wire in connection with a resonant surface of the kind hereinafter
described so that any sound, such for instance as the human voice when made to
impinge upon the resonant surface, causes the latter to vibrate in such manner in
relation to or in combination with the iron or steel conducting wire as to cause
corresponding electric currents or variations in the circuit, and thus produce
corresponding sounds at the place or places where they are to be received and
recorded.
In order to put this part of my Invention in operation, I take a straight or
horseshoe shaped soft iron bar, circular or of other suitable shape, in cross section,
and upon its pole or poles I arrange a coil or coils of insulated wire in the usual
way. Opposite to the pole or poles of the bar upon which the coil or coils are fitted
as described and in close proximity I adjust a coil or bundle of insulated iron or
steel conducting wire attached to or otherwise suitably connected with a vibrating
diaphragm of wood, so that any vibrating motion imparted to such diaphragm
causes the coil of insulated iron or steel wire to move in a similar manner, or vice
versd, that any such movement imparted to the coil causes the diaphragm to move
in a similar manner. The iron or steel wire coil may be either attached rigidly

page_text: directly to the diaphragm, or it may be connected to the latter by one or more
rigid bars or links or other connections.
Surrounding the coil of insulated iron or steel wire arranged as described, but
preferably in contact neither with the coil nor with the diaphragm, I arrange and
fix a second outer coil of insulated wire, which I prefer should also be iron or
steel, and through this outer coil I pass a constant local current of electricity from
a battery or other generator of any convenient kind. The constant current of
electricity thus passing through the outer coil produces magnetic polarities in the
various sections of the iron or steel wire which form the inner coil, and the latter
is thus rendered extremely sensitive to inductive action, and capable of very rapid
and clearly defined electric or magnetic pulsations or variations when used for the
purpose of electric telephony.
I sometimes also pass a constant local current of electricity through the inner coil
of insulated iron or steel wire from a battery or other suitable generator connected
to it in such manner as not to interfere with its vibrations. The current of elec-
tricity so passing through it assists its magnetization, and imports a certain amount
of heat to the coil, thus adding to its sensitiveness; and sometimes I connect the
inner coil with a suitable condensing apparatus of the ordinary kind, by which
the rapidity of working is increased.
I prefer to make the coil or coils of insulated wires surrounding the pole or
poles of the soft iron bar as first described of iron or steel, and I connect them
with the main line wire through which the pulsations or variations are transmitted
which constitute the audible signals, either directly or with a separate wire circuit,
arranged in such a position as to be influenced by the main line wire by induction.
I prefer that the different coils of insulated wire arranged as above described
should be constructed in the method described in the Specification of former
Letters Patent granted to me, dated August 27th, A.D. 1880, and numbered 3473,
in which the coils of insulated wire are saturated with melted paraffin wax, shellac,
or other suitable insulating material or composition, so that the solid coil requires
no bobbin to hold it intact.
Instead of making the straight or horseshoe shaped bar of soft iron as described,
I sometimes make it a permanent steel magnet. Or it may be of soft iron
converted into an electric inagnet by electricity, passing through a coil or coils of
insulated wire surrounding it. Sometimes I use the apparatus constructed and
arranged as described, but I omit the outer fixed coil of insulated wire; and some-
times I wind both the inner and outer coils together, so-as-to-form-a-singlo-coil,
the insulated wires either being laid parallel or being first twisted together.
Instead of one coil only of insulated iron or steel wire, attached or connected to
the vibrating diaphragma as described, I sometimes use two or more such coils
upon the surface of the diaphragm, and each such coil may have an outer coil
round it, or a double coil with the insulated wires wound upon it as last described,
and one or more soft iron bars or magnets with their coils may be used in con-
juction with such diaphragm coils. And sometimes instead of the soft iron bar
surrounded with a coil or coils, I use a fixed coil of insulated iron or steel con-
ducting wire arranged opposite to the coil attached to the diaphragm as described,
and an outer coil may be arranged round either or both such coils, so as to
magnetize in the way already hereinbefore described either the fixed coil or
the vibrating diaphragm coil, or both. And either one or more such stationary
coils may be used in conjunction with one or more coils attached to the diaphragm,
and one or more of such diaphragm coils may have an outer coil or coils to
magnetize it or them; or one or more of the stationary or fixed coils may have an
outer coil or coils to magnetize it or them. The wires of the different coils so used
may be arranged so as to form double coils, as already described, the wires being
wound either parallel or first twisted together.
Sometimes I insert the fixed coil used as described in the place of the soft iron
bar, either directly in the main line wire circuit, or in a circuit influenced by
or influencing the main line wire by induction; and sometimes, instead of or in

page_text: combination with such method of arrangement, I connect the outer coil of such
fixed coil with the main line wire.in a similar mauner.
Or sometimes I surround both the single fixed coil and the coil attached to the
diaphragm with a single separate coil of insulated wire.
Or sometimes I connect the coil attached to the diaphragm to the main line
wire, or to a wire influencing or influenced by the main line wire by induction.
I make the diaphragm preferably of wood, but I sometimes make it of other
non-metallic body capable of sufficient audible vibration; or in some cases, and in
some of the methods of arrangement described, it may be made of metal, such as
iron or steel.
Another part of my Invention consists of novel methods of constructing and
arranging apparatus, by means of which electrical currents or variations are
transmitted so as to produce audible signals by means of corresponding sounds,
such as the human voice, acting upon the apparatus.
Electrical currents or variations so produced in the novel apparatus which I will
now describe are converted, after passing along the main line wire circuit, into
audible signals by means of the novel apparatus already described, or other
suitable apparatus of the kinds already known and used.
For the purpose of so transmitting electrical currents or variations I employ
pieces of semi-conducting material, such as carbon, through which the currents pass
and are made to vary by means of the vibration of such pieces induced by sound,
as in the apparatus well known as the microphone. I take one, or preferably more
bars or pieces of such semi-conducting material, preferably carbon, and I make
some or all of such pieces hollow, so that each contains within it a column or body
of air, and I arrange these pieces parallel, or in other convenient positions
relatively to each other, and loosely supported at their ends in carbon or other
blocks connected with the wire circuit in which the currents or variations are to be
produced in such manner that the hollow bars form part of the circuit. Opposite
to the open ends of the hollow bars so arranged is a column or columns of air
confined in corresponding tubes or passages in a suitably shaped mouthpiece, at the
outer end of which the sound, such as the human voice, is made by which the
electrical currents or variations are to be produced.
When such sounds are made into or in the neighbourhood of the mouthpiece,
the column or columns of air confined in the latter, as described, are set in
vibration, which vibration is communicated directly to the corresponding columns
of air in the hollow carbon bars, and the latter are themselves made to vibrate in
their supports, and thus to cause corresponding currents or variations in the
electricity passing from any suitable battery or generator through the carbon bars
and through the wire circuit with which the latter are in connection. The outer
ends of the hollow carbon bars may be closed. In order to increase the capacity
of the apparatus just described, or other transmitting apparatus, to overcome the
resistance of the main line wire in which electrical currents or variations are to be
produced, and also the effectiveness of the receiving apparatus, and through which
it is often found necessary or advisable to maintain a constant current of electricity
from a battery or other generator, which current passes through coils in the
receiving apparatus for the purpose of producing magnetism, instead of using a
single induction apparatus, I arrange the transmitting apparatus in connection with
a constant current of electricity passing through the primary coil of each or all of
two or more such induction coils arranged separately or conjointly, and I connect
the secondary or other coils surrounding them all or some in parallel circuit with
each other, and these coils arranged in parallel circuit I insert in the main line wire
in which I desire to induce currents by the action of the primary wires.