IMPROVEMENTS IN MICROPHONE TRANSMITTERS FOR TELEPHONIC PURPOSES to be as follows
Year: 1884

page_text: I, WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake and Co, Patent Agents,
Southampton Buildings, London in the County of Middlesex do hereby declare
the nature of said invention for "IMPROVEMENTS IN MICROPHONE TRANSMITTERS
FOR TELEPHONIC PURPOSES to be as follows :-
"
My invention relates to telephone transmitters of the class usually termed
microphones and is designed to improve the construction and operation of the
same.
In carrying my said invention into practice I employ two or more microphonic
contacts in such a manner that the electric current from a battery or other source
of electricity will pass through all of the said contacts simultaneously. I prefer
to arrange these contacts in combination with a single diaphragm, that is to say,
to fix one half or part of each of the contacts to the said diaphragm. The other
halves or parts of the said contacts I suspend like a series of pendulums from a bent
arm or piece fixed to the box or casing of the instrument. These pendulum contact
pieces may be of equal length or of different lengths, and of equal or different
weight. The diaphragm which I employ is fixed to the frame at only one point of
its circumference, and is in some cases, suspended like a pendulum, and may or
may not be adjustable by means of a set-screw. One or more springs are fixed to
the frame and arranged to bear upon the diaphragm to regulate its vibration; these
springs are sometimes provided with an adjusting screw.
The apparatus above described may be combined with one or more induction-
coils and condensers.
My improved apparatus may be conveniently and advantageously described as
follows, that is to say :-
I fix to a block or piece of wood or other suitable material which may form the
front of a box or case, an arm or piece carrying three pendulums at the ends of
which electrodes or contact pieces are secured in such a manner as to bear against
electrodes or contact pieces secured to the diaphragm. This diaphragm is

page_text: surrounded by a soft india-rubber ring, and is fastened to, and in metallic
connection with, the frame by means of a screw. Two springs are fixed to the
frame and bear upon the diaphragm near its centre to regulate its vibration.
These springs can be adjusted either by simply bending them to a certain curve or
by means of adjusting screws passed through their free extremities. A mouthpiece
is fixed to the said block or piece of wood which has an aperture in front of the
diaphragm. This mouthpiece may be made of any suitable form and material.
The conducting wires from the battery or other source of electricity are connected,
one to the arm or piece carrying the pendulums and the other to the frame and
through the said frame to the diaphragm.

page_text: 1, WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake & Co, Patent Agents,
Southampton Buildings, in the County of Middlesex do hereby declare the nature
of my invention for "IMPROVEMENTS IN MICROPHONE TRANSMITTERS FOR
TELEPHONIC PURPOSES" and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:—
My invention relates to telephone transmitters of the class usually termed
microphones and is designed to improve the construction and operation thereof.
In carrying my said invention into practice, I provide a telephone transmitter
with two or more microphonic contacts, through which the electric current from a
battery or other generator will pass simultaneously, that is to say, I employ two
or more pendent contact-pieces in combination with a corresponding number of
contact-pieces firmly attached to the diaphragm. These contact-pieces may consist
of carbon or similar material; they are held in contact by gravitation, and
connected to the battery or other generator as hereinafter set forth.
The diaphragm is, in some cases, fixed at only one point of its circumference,
and in other cases it is suspended in any suitable manner; and I prefer to provide
one or more adjustable springs for regulating or controlling the vibration of the
diaphragm.
I sometimes combine my improved apparatus with one or more induction coils or
with one or more condensers.
My improvements are illustrated in the accompanying drawing, in which
Figure 1 is a rear elevation shewing one form of my transmitter.
Figure 2 is a section on the line x, x, Figure 1.
Figure 3 is a rear elevation of my transmitter with some of the parts removed,
and shewing a slight modification of my invention.
Figure 4 is a section on the line y, y, Figure 3.
Like letters indicate corresponding parts in the several Figures.
a is a block or piece of wood or other insulating material, which may form the
front of the box or case of the instrument. This block or piece is made with an
aperture wherein is fitted a mouthpiece al of any desirable form and material.
b is the diaphragm, which may be of steel, iron, brass, zinc, wood, ebonite,
vulcanized fibre, or other suitable material, and to which are attached the contact-
pieces c. d is a bracket rigidly secured to the block or piece a, and carrying three
arms e, in the ends of which are fitted the contact-pieces f. These arms e are
pivotted to the said bracket so that the pieces f are suspended, and maintained,
by gravitation, in contact with the pieces c, and form therewith the microphonic
contacts. The arms e of these pendent contact-pieces may be of equal or unequal
length and weight, as desired.
The diaphragm 6 is surrounded by a soft india-rubber ring g, which prevents the
passage of air between it and the frame h. The said diaphragm is preferably
secured to the frame h at only one point of its circumference by means of the
screw i, as shewn. This screw forms a metallic connection between the said frame
and the diaphragm.
In order to regulate or control the vibration of the diaphragm 6 and prevent
excessive vibration thereof, I provide one or more springs j secured to the frame h
and so arranged that their inner or free ends bear upon the said diaphragm near
its centre. These springs can be adjusted, to cause them to act with greater or
less pressure upon the diaphragm, either by simply bending them to the desired
extent or by means of adjusting screws k passed through their free extremities as
shewn in Figures 3 and 4.

page_text: The conducting wires from the battery or other generator of electricity are
connected, one to the bracket d carrying the pendent contact-pieces, and the other
to the frame h, the connection between the generator and the diaphragm 6 being
completed through this frame and the screw i
Instead of securing the diaphragm b to the block or piece a by a screw as above
described, I sometimes suspend it in any suitable manner.
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
First. In a microphone, the employment of two or more pendent contact-pieces
in combination with a corresponding number of contact-pieces attached to the
diaphragm, substantially as, and for the purpose, set forth.
Second. The modification of my invention wherein the diaphragm is suspended,
or is secured only at one point of its circumference, as above specified.
Third. The improved microphone consisting of the parts constructed and
combined substantially as described with reference to Figures 1 and 2 or to
Figures 3 and 4 of the accompanying drawing.
Fourth: The combination of my improved apparatus with one or more induction
coils or with one or more condensers.
The Toit