IMPROVE- MENTS IN TELEPHONES AND TELEPHONIC CALL MECHANISM
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by John Lawton Haddan at the Office
of the Commissioners of Patents on the 20th June 1878. A communication
from abroad by Abnor Mulholland Rosebrugh, of Toronto, in the Dominion of
Canada, Doctor of Medicine.
JOHN LAWTON HADDAN, of the Firm of Herbert and Company, Solicitors of
Patents, of 67, Strand, in the City of Westminster, Civil Engineer. "IMPROVE-
MENTS IN TELEPHONES AND TELEPHONIC CALL MECHANISM." A communication
from abroad by Abner Mulholland Rosebrugh, of Toronto, in the Dominion of
Canada, Doctor of Medicine.
This Invention has for its object the combination of an improved telephone and.
a signalling apparatus in one instrument, and it consists of one or more permanent
magnets which are used in common for the purpose of magnetizing the cores of the
telephone electro-magnets, and also to magnetize the cores of moveable coils or
electro-magnets used for the production of induced currents for signalling purposes.
The telephone is constructed as follows:-To a diaphragm, which is connected
with a mouth-piece in the usual way, and which is made of any suitable material,
one or more cylindrical pieces of magnetized steel are attached, say one-quarter of
an inch in diameter and one inch in length. The free end expands suddenly near
the end to, say, one-half inch diameter. This magnetized cylinder passes loosely
through the centre of the core of an electro-magnet, which is secured to a plate,
which plate is, say, one-quarter of an inch from and parallel with the telephone
diaphragm.
The core of the electro-magnet is made of soft iron. A space is enclosed between
the diaphragm and the plate, to which the electro-magnet is attached, and from
which a tube leads to an elastic tube, which terminates in an ear-piece, and is used
for listening.
The free end of the magnetized steel projects, say, one-quarter of an inch beyond
the core of the electro-magnet, and the extremity is adjusted to very near one pole
of fixed permanent magnet, the pole being of opposite polarity to that of the free
end of the magnetized steel cylinder.

page_text: The action of the telephone is as follows:-When the diaphragm is vibrated
either by the voice or otherwise, the vibrations are communicated to the magnetized
steel, the free end of which is in close proximity to the fixed magnet; this varies
the magnetization of the core of the electro-magnet, and an undulatory current of
induced electricity is developed in the coil and through the circuit of which it
forms a part.
If the diaphragm is composed of soft iron it should be adjusted near to the core
of the electro-magnet; the induced current in the coils is strengthened, and the
telephone can be used on a line of higher resistance.
During conversation both surfaces of the diaphragm are utilized, the tube from
its posterior surface being constantly kept to the ear.
If a horse-shoe magnet is used two electro-magnets and also two small magnets
attached to the diaphragm may be used.
The signalling apparatus is constructed as follows:-On the side of the large
magnets opposite to that of the telephone electro-magnets one or more electro-magnets
or induction coils are made to rotate or to move to and fro by suitable mechanical
means.
These induction coils are made to move very near the poles of the magnets in such
a manner that their cores will alternately be magnetized and demagnetized so as
to cause induced currents in the coils and the line with which they are connected.
A single or double pair of electro-magnets are added, and provided with an
armature vibrating between the poles of the electro-magnets, and connected with a
striker or provided with an adjusting spring to oppose the action of the electro-
magnets.
The armature may be magnetized steel, or the electro-magnets may be polarized.
The induction coils are also provided with a commutator or an automatic current
changer, which may or may not be used at pleasure.
The transmitting and receiving instruments are made alike, and are connected in
the usual way; when the induction coils are rotated or moved to and fro near the
polls of the magnet, the induced current affects the signalling coils, and the bells are
rung both in the transmitting and in the receiving instruments.
By breaking the current by means of a press button and again closing it, and
repeating a definite number of times, a definite signal can be given.
By using the automatic interrupter, a signal can be given on the receiving
telephone diaphragm.
The instrument is also provided with a switch for shunting the signal while
speaking, and the telephone while signalling, and also a press button for interrupting
the current while signalling.