Year: 1892

page_text: Date of Application, 20th Jan., 1892-Accepted, 20th Feb., 1892
Fig. 3 is a front view of the apparatus with the transmitter and the gong
removed for the purpose of shewing the arrangement of the bell magnet. The
flexible tube and the receiver being also removed to avoid unnecessary complexity
of the figure.
Fig. 4 is a detail plan view of part of the transmitting instrument which will be
hereinafter described and explained.
Fig. 5 is also a detail shewing the transmitting instrument and part of the tube
in vertical section with the gravity switch in place.
Fig. 6 is a detail longitudinal section on an enlarged scale shewing the form of
gravity switch which is preferably used.
A is a metal base plate by which the telephone may be secured to a wall. B is
an insulating plate composed of vulcanite or other suitable material. Secured to
the plate B is a frame C which carries an electric belle of ordinary construction
enclosing an operating electro magnet D. The bell e is insulated from the metal
frame C by an insulating sleeve but is in connection through a bracket d with
one pole of a battery D'.
The transmitting instrument is provided with a concave metal month piece E of
the ordinary type which screws upon a disc F composed of vulcanite or other
suitable insulating material. The diaphragm G is held in position between the
cap E and the disc F, which disc is fitted with an axial screw f by which it is
secured to and contact is made with the metal frame C. The head y of the screw f
is of disc form (see Figs. 2 & 4) and between it and the diaphragm G is placed a
microphone (see Fig. 4), of any approved construction, it being preferably
composed of granulated carbon. The under surface of the diaphragm G and the
upper surface of the disc g forming the contact surfaces of the microphone should
be coated with plumbago, graphite, or other suitable form of carbon, in order that
the microphone may be gripped between two nou-oxidisable surfaces. Metallic
contact is made between the cap E and the bell c by means of a metal spring e
which is held between the disc F and the bell c. The frame C is put into connexion
with the earth. It will now be seen by referring to Fig. 2 that one pole of the
battery is in metallic communication with the earth through the bracket d,

page_text: gong spring e, cap E, diaphragm U, microphone 7, axial screw and the Dell
frame C.
J is a flexible tube secured to and pendent from the base plate A and it carries
at its free end the receiving instrument. This receiving instrument consists of a
short iron cylinder or shallow box K provided with a central adjustable iron pin k
which is surrounded by a bobbin of covered wire L and thus forms the core of an
electro magnet (see Fig. 5). The diaphragm M of the receiver rests upon and is
in metallic contact with the edges of the cylinder or box K and it is retained in
position by means of a cap k¹, which also retains the ear piece N in position. One
end of the wire of the electro magnet L is in contact with the box K while the
other end of the wire terminates in a contact point in connection with a gravity
switch O (see Fig. 6). The gravity switch O consists of a short glass tube scaled
at both ends and containing a small quantity of mercury o. The line wire is passed
through the tube from end to end and the end of a wire, leading through the bell
magnet coil to earth, is inserted in one end of the glass tube, whilst the end of
another wire leading to the coils of the magnet of the receiving instrument is
inserted in the other end of the glass tube.
When a current is caused to pass through the wire of the electro magnet Lit
will also pass through the diaphragm M which will thus form one pole of the
magnet, the free end of the core forming the other pole, thereby rendering the
diaphragm highly susceptible to the variations in the current.
The receiver will hang pendent from the base plate A as shewn in Fig. 1 when
the telephone is not in use and the mercury o in the gravity switch O will close the
circuit with the line, and with the earth, through the bell magnet D, as shewn in
Fig. 6. But when the receiving instrument is raised to the car, for the purpose of
receiving a message, the mercury o in the glass tube of the gravity switch will fall
to the opposite end and the circuit will be closed from the line to the earth through
the receiving instrument, the battery D', and the transmitting instrument.
The flexible tube J which is preferably composed of a helix of wire serves
as a conductor from the receiver magnet to the battery. Other forms of gravity
switch may be used but the form of switch shewn in the drawing is considered the
best adapted for the purpose.
Fig. 8 is a diagram shewing the circuits. When the instrument is at rest the
circuit is closed from the line, through the bell, to earth and when the receiving
instrument is raised, to receive a message, the mercury in the gravity switch will
close the circuit from the line through the receiving instrument, battery D', and
transmitter to earth. The apparatus at each end of the line should be provided
with a battery.
Fig. 7 shews a modification of the above described arrangement of telephone
which is specially adapted for use at an office table or desk so that the user may be
in a position to employ the telephone without leaving his seat. In order to meet
the exigencies of such a case the transmitting instrument is attached to one end
of a rigid curved metal tube P, the receiving instrument being attached to the
opposite end of a curved tube. The relative positions of the transmitter and the
receiver should be such, that when the transmitter is placed opposite the mouth of
the speaker, the receiver should lie close to his ear. When the instrument is not
in use it should be hung upon a hook carried by the base plate A the receiver
remaining pendent as in Fig. 1. In Fig. 2 the transmitter is in circuit through
the conducting pieces d, and the bell frame C, but in the arrangement shewn in
Fig. 7 conducting wires Q are used the wires being laid up in the form of a cord.
Allowing for the slight modification of the arrangement of conductors the action
of the apparatus is precisely similar to that previously described.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by my
foreign correspondent, I declare that what I claim is :-
1. In telephones a transmitter superposed upon a gong or call bell and provided

page_text: with a stem or screw such as f and a spring piece such as e such screw and
spring piece e forming conductors whereby the circuit is closed through the
transmitter microphone as specified.
2. In telephone transmitters coating the contact surfaces between which the
microphone is placed with a film of carbon whereby oxidation is minimised as
specified.
3. In telephones the flexible tube or helix of wire, such as J, whereby the
receiver is supported and connected to the main body of the telephone as herein set
forth.
4. In telephones a receiver provided with a gravity switch and supported by
means of a flexible connection, in combination with a transmitter call battery
whereby when the receiver is raised or lowered the necessary circuits shall be
closed as herein set forth.
5. In telephone receivers a shallow iron box, preferably of circular form,
provided with a central core, a solenoid or electro magnet, and an iron diaphragm
which rests upon and is in metallic contact with the sides of the box as and for the
purposes herein set forth.
6. In telephones a curved tube or connection, at one end of which is placed the
transmitter and at the other end the receiver, their relative, positions being such
that when the receiver is placed to the ear the transmitter shall be opposite the
mouth, in combination with a gravity switch whereby the act of raising the receiver
to the ear closes the necessary circuits as specified.
Dated this 20th day of January 1892.
NEWTON & SUN,
Agents for the Applicant.