IMPROVEMENT IN TELEPHONE RECEIVERS
Year: 1884

page_text: IJ ENSIGN FULLER of Chicago in the County of Cook and State of Illinois,
one of the United States of America electrician do hereby declare the nature of
my invention for IMPROVEMENT IN TELEPHONE RECEIVERS and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement :-
My invention consists of a multipolar magnet composed of several pole pieces of
a given polarity arranged in a group around a central re-entrant pole piece of
opposite polarity, said first mentioned pole pieces being attached to or integral"
with a disc or base, or arms radiating from a common center, which forms the base
of the re-entrant pole.
The object of my invention is to obtain more powerful magnetic action in a
telephone receiver than has heretofore been secured by other magnets whatever their
size or construction, and thereby greater amplitude of vibration in the diaphram.
Distinctness and clearness of the sounds reproduced is of the greatest importance,
and these I secure by my instrument so that vocal or musical sounds are readily
heard and understood even when the listener is several feet removed from the;
instrument. The loudest sounds as well as mere wispers are reproduced with equal
distinctness, the sounds received varying only in degree.
This function of my instrument I consider of the greatest advantage and
practical utility because it permits persons to carry on conversation in any tone of
voire the circumstances may require.
In the drawings similar letters of reference indicate like parts.
Fig. 1, is a sectional perspective view of my instrument showing the arrangement
of the several parts.
Fig. 2, is a top view of the magnet with the case remove !.
A, A, is the outside casing or box enclosing the entire apparatus. O, is the
orifice through which the sound waves reach the ear. b, b, b, b, b, b, are pole pieces
of given polarity.together forming one pole of the magnet, and b, is the other pole,
re-entrant or extended up inside of the other pole pieces, and .attached to or
integral with the base, from which it is extended upward. H, is the helix
or coil attached to the re-entrant pole piece, and having wires f, f, leading to
the line and ground. C, is a thin vibratory disc or diaphragm resting on pole
pieces b, b, b, b, b, b.

page_text: When the disc, C, is placed upon the upper end of the pole pieces, b, b, b, b, b, b;
said disc becomes one pole of the magnet and the magnetism of said pole pieces is
concentrated directly over the re-entrant or extended pole. piece b', of opposite
polarity.
•
By thus bringing the poles of the magnet opposite to each other, and in close
proximity greater magnetic strength is secured as well as greater amplitude in the.
vibrations of the diaphragm.
I am aware that multipolar magnets in telephones consisting of a series of
separate U, magnets arranged circumferentially and forming a compound central or
re-entrant pole have been used either with or without a central bar, and I do not
claim such magnet as my invention.
I am also aware that magnets' constructed substantially like mine, have been
used in telephones, but in such cases the diaphragm was not magnetized by
contact with the circumferential pole pieces which is an important feature of my
invention.
The essential feature of my invention is a multipolar magnet, in which the pole
pieces arranged on the periphery of a circle are attached to or made integral with
a base or disc, or to arms radiating from a common center, with a single central
pole piece extending the opposite polarity of all of said pole pieces up to a point
slightly below a line drawn across the upper ends of such pole pieces.
The advantage gained by my one re-entrant pole piece is that the opposite polarity
is thus centered in the smallest space possible beneath the diaphragm or other pole
and the diaphragm is acted upon at its absolute physical center.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. In a telephone receiver a multipolar magnet consisting of a number of pole
pieces of given polarity attached to or integral with a base or disc or arms radiating
from a common center carrying a plate or diaphragm and a re-entrant pole piece of
opposite polarity extending upward from said base or common center, substantially
as described.
2. In a magneto telephone the combination of a multipolar magnet having
circumferentially arranged pole pieces of one polarity projecting from a disc and a
single pole piece of opposite polarity projecting from the center of the same with
a diaphragm resting upon the circumferential pole pieces, and in inductive proximity
to the central pole piece substantially as described.
3. In a magneto telephone the combination of a multipolar magnet having
circumferentially arranged pole pieces of one polarity attached to or integral with
arms radiating from a common center and a single pole piece of opposite polarity
secured to such common center or integral therewith, with a diaphragm resting
upon the circumferential pole pieces, and in inductive proximity to the central
pole piece substantially as described.
Dhan 1884