Year: 1886

page_text: I EMILE BERLINER of Boston, Massachusetts, United States of America do
hereby declare the nature of this invention 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 that class of microphones or telephonic transmitters in
which a small quantity of granulated conducting material is included in the electric
circuit, causing the current to vary in conformity with the number and strength
of the sound waves.
!
In combination with the granulated conducting material, I employ a vibratory
plate or diaphragm preferably of carbon and a small carbon block which latter is
plunged into the granulated material I also employ a curved conical sound funnel
of soft india rubber or other suitable material.
The carbon plate is pierced with holes which are not large enough to allow the
granulated material to pass out but will permit of the passage of the sound waves
which impinge against the plate.
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The granulated material is enclosed in a box of somewhat smaller diameter than
the diaphragm and the edge of this box is fitted with a ring of some soft material
which cushions against the diaphragm but is not attached thereto.
The apparatus is fitted so as to slide up or down guide rods included in the
electric circuit in order to permit of its ready adjustment to suit the convenience
of the user, thus rendering the use of flexible conductors unnecessary.
In order more clearly to explain the nature of my invention I have shown at
Fig. 1 in the accompanying drawing a transverse vertical section of the receiver,
and its several component parts in detail, and at Fig. 2 a front elevation of the
instrument mounted on its guide rods.
In all the figures the same letters indicate corresponding parts.
B is a box of wood, caoutchouc, metal or other suitable material, closed by
a cover B. Upon the rim of the box B is fixed in any suitable manner a metal
ring M to which is attached one of the conducting wires. D, is a diaphragm
preferably formed of hard carbon, this plate is pierced near its centre with a less
or greater number of holes o, o, according to circumstances.
K is a box or cap
which may be formed either of conducting or of non-conducting material and on
the inside of this box is secured the hemispherical electrode C formed of hard

page_text: carbon and secured in place by the screwed rod L and nut E the rod and nut
serving at the same time as a binding screw for one of the conducting wires. To
the edge of the box or cap K is fitted a ring F of some soft and flexible material
such as felt or india rubber which rests in contact with the diaphragm D but is
not attached thereto. The screwed rod L is also prolonged by a short tubular
piece G of flexible material which rests in like manner against the plate D and
serves the purpose of deadening the vibrations of the plate. The box K is packed
full of the granulated conducting material such as graphite or carbon.
His a short tubular neck screwed into the cover B₁ to which neck is fitted the
curved funnel S of india rubber or some similar flexible material.
P P (Fig. 2) are two guide rods upon which slide two short tubes R R¹ and to
these short tubes the apparatus above described is attached.
The tube R is electrically connected by the binding screw E to the hemispherical
-carbon block and R' is also electrically connected to the brass ring M and by it
to the diaphragm D. The ends of the rods P and P are connected together by
means of cross bars N N but are insulated therefrom, and binding screws V and Vi
serve to connect the rods with the line wires.
The form of the electrode C may be varied if thought desirable in the manner
indicated, by way of example only, in the detached views C and C².
I do not consider it is essential that the electrode should be formed in one piece
as it may in some cases be desirable to form it in two or more pieces, electrically
connected together.
For microphones fitted with induction coils it will be necessary to provide four
guide rods in place of the two as above described, two of the rods serving to carry
the primary current and two the secondary current.
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 microphone the employment of a suspended electrode partly or entirely
buried in a small heap of granulated conducting material.
2. The employment in a microphone of a box filled with granulated conducting
material, in combination with a ring of felt, flannel, caoutchouc or other flexible
material which bears freely against a diaphragm or other vibrating body.
3. The employment in a microphone of a perforated vibratory plate in com-
bination with a small heap of granulated conducting material resting upon the
.said plate.
4. The combination, in a microphone, of a vibratory and conducting surface,
against which rests a heap of granulated conducting material, of a suspended
electrode, partly or entirely plunged in the said heap of granulated conducting
material through which viz the conducting surface, the heap of granulated
conducting material, and the carbon electrode, the electric current passes.
:
5. The employment in a telephone of a curved trumpet shaped mouthpiece of
soft elastic material to receive the sound waves.
6. The combination of a telephone with two or more guide rods included in the
electric circuit and which permits of the raising and lowering of the apparatus as
and for the purpose set forth.