IMPROVEMENTS IN TELEPHONE RECEIVERS
Year: 1880

page_text: LETTERS PATENT to Robert Minturn Lockwood and Samuel Hubbard Bartlett,
of the City, County, and State of New York, in the United States of North
America, for an Invention of "IMPROVEMENTS IN TELEPHONE RECEIVERS.”
COMPLETE SPECIFICATION filed by the said Robert Minturn Lockwood
and Samuel Hubbard Bartlett at the Office of the Commissioners of Patents
on the 15th June 1880.
ROBERT MINTURN LOCKWOOD and SAMUEL HUBBARD BARTLETT, of the City,
County, and State of New York, in the United States of North America.
"IMPROVEMENTS IN TELEPHONE RECEIVERS."
In telephone receivers as heretofore constructed flexible diaphragms of metal have
been employed in combination with a magnet arranged out of contact with but in
such near proximity to the magnet as to be capable of producing an induction
current by its vibrations towards and away therefrom.
We propose to form the diaphragm upon or attach it to a reduced arm forming
an extension of one pole of a single bar magnet, which shall so support the diaphragm
as to make it constitute a sounding board, to which the disturbances in the current
are conveyed by molecular action or by difference in degree of polarity in different
parts of the pole, to which it is connected rather than by mechanical vibration of
the diaphragm due to its attraction to and repulsion by the magnet as in the usual
construction, for it will be apparent that if the diaphragm or sounding board is an
extension of the pole it cannot be attracted or repelled by said pole, and the magnet
being in the form of a single straight bar the sounding board is of course removed
from the influence of the opposite pole of the magnet, and can only be affected by
disturbances in the current in the pole of which it is thus made to form a part.
In the accompanying Sheet of Drawings Figure 1 represents our improved
receiver for telephones or vocal sound telegraphs in section; Figure 2 is a like view
showing a modification in the manner of connecting the diaphragm with the
magnet; Figure 3 is a perspective view showing the diaphragm and the end of the
magnet with which it is connected under the construction shown in Figure 1;
and Figure 4 is a similar view of the end of the magnet and the U shaped extension
shown in Figure 2.

page_text: A represents the handle or body of the receiver, made preferably of wood,
cylindrical or tubular in form, with an enlargement at one end forming the head A',
to which the ear piece C, of any usual or preferred form, is secured. The handle is
perforated longitudinally to receive the straight bar magnet D, the perforation in
the head part A' under the ear-piece being enlarged into a socket or chamber for
the reception of the helix E surrounding the end of the magnet projecting into said
socket. The magnet may be made in a single piece, but for convenience in forming
the reduced extension or arm hereinafter described we prefer to make it of a
number of thin plates or bars, secured to each other side by side, as represented in
Figuro 4, one of which is extended beyond the others in the form of a laterally
projecting arm d, recurved upon itself at d' until its end overhangs the other
parts or that end D' of the body of the magnet from which it is projected.
Where the magnet is in a single piece it will of course be drawn out and reduced
in size until it forms a U shaped spring, as shown, and its free end may be so
expanded as to form the disk or diaphragm B, shown in Figure 3, or the
diaphragm may be riveted or otherwise firmly secured thereto, as shown by the
construction in Figures 2 and 4. Where the diaphragm is formed on the U shaped
spring arm the loop part of said arm passes out through an aperturo in the
head A', so as to bring the diaphragm over and make it cover the entire end of said
head, where it is clamped in place by the ear pieco. Where the diaphragın is in a
separate piece riveted or otherwise secured to the arm d, d³, said arm can be
shortened up and secured within the chamber in head A', as shown in Fig. 2.
Where the latter construction is employed it may sometimes be found desirable to
adjust the tension of the diaphragm B, and to facilitate this the lower or small end
of the handle A has a cap plate a secured to it, and a thumb screw a' passing
through a perforation therein engages with the lower end of the magnet, as shown,
and by its adjustment or rotation the magnet can be moved towards or away from
the diaphragm for regulating its tension as desired, and inasmuch as we do not
depend upon the attraction and repulsion of the diaphragm by the polo of the
magnet said diaphragm may be made of parchment, strong paper, thin wood, brass,
or other non magnetic material, such as is suitable for a sounding board; and very
satisfactory results have been obtained by the use of such materials. In the use of
these the adjustment for regulating the tension of the diaphragm becomes important
in order to secure the best results. The wires from the helix E pass out through
perforations in the head or body of the telephone, and are connected with the
line wires either directly or through binding posts F, as shown, the latter con-
struction being preferred as facilitating the detachment of the receiver when
desired. For the purpose of destroying the induced current from the helix, and
making the direct or battery current stronger and more susceptible of disturbance
we place a metal sleeve G over the helix in the socket in the head A', as shown in
Figure 1, the effect of which is to obviate the injurious action of the induced current
upon a receiver employing a strong battery current and to produce a marked
improvement in the articulation of the receiver.
"
Under the construction and arrangement of parts shown and described it will be
seen that the spring arm d, d³, forms an extension of the pole D¹ of the magnet
reduced in size, and that as a consequence its normal condition will be one of rest
in relation thereto. Thus, supposing the current in the helices to be represented by
one," then the amount of magnetism in the magnet at D' will be "one," and that
in the arm d' will also be "one," and the latter will be at rest. But the body of
the magnet lies within the helix, and is more quickly affected by it, and constitutes
as it were a reservoir, from which the small arm d, d', is supplied. Now, supposing
the current in the helix to be disturbed or suddenly increased to "two" the end or
pole D¹ becomes "two" in advance of the arm d', and for the instant attracts the
¡latter until it also becomes "two," when it is instantly repelled; then its normal
condition as a part of pole D' being restored it returns to its normal position of rest 5
until it is again attracted or repelled through another disturbance of the current in
the helix. Thus for each disturbance in the curront there would be three distinct

page_text: movements of the arm and of the diaphragm B connected therewith as
follows:-First it is drawn down toward end D, then it is repelled beyond its
normal position, and, finally, the equilibrium being restored it moves back to its
normal position of rest. It will thus be seen that the diaphragm is operated
by disturbances or differences in degree of polarity or attraction and repulsion
in different parts of the pole to which it is connected, and of which it forms a
part.
The construction of the magnet may be varied materially from the particular
form shown so long as the diaphragm is directly connected with one pole thereof by
means of an arm or arms of reduced size as compared with the pole of the magnet,
of which said arm forms an extension, and is upheld over the magnet thereby in
such manner as to make it form an effective sounding board. In the explanation
given of the theory of the action upon the diaphragm or sounding board it is not
intended to assert that the action of the diaphragm is such as is there described,
as it is probable that its action is due to molecular disturbance to which the
sounding board gives articulation; but one thing is manifest, viz., thatthe diaphragm
being connected with or made a part of one pole of the magnet, and being removed
as it is from the influence or control of the opposite pole, is not subject to the
induced current referred to, is free from the objectionable rattling or snapping
incident to the presence of such current, and can be used in connection with a
direct or battery current of any desired power without endangering its being
grasped and held by the magnet, thereby adapting it to be applied to long circuits
and to operate with the same precision as the ordinary telegraph instead of being
dependent upon the weather, and more uncertain induced current as in the case of
ordinary telephone receivers. Having now described our Invention, what we claim
is,-
1st. The hereinbefore described method and means for receiving sound waves in
receivers for telephones; 2d, in a telephono receiver, the diaphragm or sounding
board formed upon or secured to a reduced or spring extension of the pole of
the magnet; 3d, the curved or U shaped arm made in one piece with and forming
a reduced extension of one pole of the magnet, and having the diaphragm formed
on or secured to it; 4th, the diaphragm connected with one pole of the magnet by
means of the reduced arm or spring extension of and arranged relatively to said
pole, as described; 5th, the combination with the diaphragm or sound board of a
telephone receiver of a magnet having its helix provided with the metallic enclosing
sleeve, for the purpose set forth; 6th, the combination in a telephonic receiver of a
magnet having the diaphragm secured to or formed upon a reduced extension
of one of its poles, a helix, and a metallic sleeve surrounding said helix, as specified.
In witness whereof, we, the said Robert Minturn Lockwood and Samuel
Hubbard Bartlett, have hereunto set our hands and seals, this Fifteenth
day of June, in the year of our Lord One thousand eight hundred and
ROBERT MINTURN LOCKWOOD. (1.S.)
SAMUEL HUBBARD BARTLETT. (L.S.)