Improvements in Microphones.
Year: 1894

page_text: Date of Application, 10th Apr., 1894
Complete Specification Left, 10th Jan., 1895-Accepted, 10th Apr., 1895
Improvements in Microphones.
I, HENRI CARBONNELLE, of No. 24 Rue Rogier, Brussels, in the Kingdom of
Belgium, Electrician, do hereby declare the nature of this invention to be as
follows:-
The main objects of my improvements are first to construct a microphone of
great sensitiveness and comparatively great resistance, so as to enable communi-
cations to be exchanged at great distances, without the assistance of an induction
coil, whereby the subscribers of telephone companies may dispense with the
batteries which have heretofore been fitted up on their premises, such batteries
being, instead, arranged at the central office or station; and second to enable any
desired direction to be given to the microphone.
Another, secondary, object of the invention is to enable the improved
microphone to be simply and readily substituted for other microphones, while
retaining the battery and the induction coil, as before, in the subscriber's house;
the important advantage resulting from such substitution being, that the quantity
of electrical energy expended in the operation of the line is materially reduced.
The microphone consists of a thin and flexible india-rubber tube, the orifices of
which are closed by means of conducting tablets made of carbon or any other
suitable material. The hollow space thus provided is filled with coke, or other
material in a granulated or reduced condition. The microphone is free at one end,
while the other end is connected to a vibrating membrane or diaphragm through
the medium of a second india-rubber or other elastic tube, narrower and shorter
than the first. The microphone diaphragm is made of any suitable substance or
material, such as cardboard, sheet-metal, ebonite, or the like. The microphone is
enclosed in a case supported by a rod which terminates in a metal ball. The rod
consists of two portions, insulated from each other electrically; and the ball also
consists of two insulated portions. The whole arrangement is placed upon a plate
or board made of a non-conducting substance, wherein is provided a hollow space
for the reception of the ball. A spiral or other spring placed at the bottom of the
said hollow space or recess presses the ball against a metal washer whereby it is
prevented from leaving the recess. The supporting table or board carries two
binding posts or screws, one of which is connected with the main or "line" wire,
and the other with the earth or the return wire. The arrangement of the electrical
connections is such that the "line" wire, through the medium of one part of the
ball, is connected to one of the tablets of the microphone, while the return wire, or
the earth, is connected to the other tablet through the medium of the other half of
the ball; the two tablets being electrically connected with each other by the
granulated coke or like material.
This arrangement enables rotary movements to be imparted to the microphone,
or admits of its being inclined at any desired angle without necessitating or causing
any interruption of the electrical connections.
The invention comprises a supporting plate or table, having a cavity or recess at
the bottom of which is located a spiral or other spring which constantly presses a
ball against a metal washer. The ball consists of two parts each of which is

page_text: electrically insulated from the other and both, respectively, terminating in a rod
and a tube, concentric with, but insulated from, each other. A case fixed to the
tube carries the membrane or diaphragm of the microphone, such diaphragm being
retained in position by a ring which also serves to support a funnel or trumpet.
To the centre of the diaphragm is cemented a hollow india-rubber tube to which is
secured a carbon or other conducting tablet. A thin and flexible india-rubber
tube is fitted on or round the said tablet while the other end of such tube is closed
by a second tablet. The cavity or recess in the tube is filled with granulated
coke or other material of medium conducting power. A. conducting strip or plate
connects the tube to the lower tablet electrically, through the medium of a wire,
soldered to a metal stud insulated from the diaphragm by a small non-conducting
plate. Another metal strip similarly connects the tube to the upper conducting
tablet through the medium of the case and a wire. The table or board carries
two binding posts or screws electrically connected with the metal washer and the
case through the medium of two wires, and the spring underneath the ball.
The operation is as follows:
(a.) Without an induction coil, the source of electricity being arranged at the
central station.
To the binding post is connected the "line" wire. A battery or other current,
sent from the central office flows through the wires, spring, lower part of ball aud
thence to the lower tablet of the microphone tube, traverses the layer of granulated
material in the tube and in doing so undergoes the variations of resistance resulting
from the vibrations of the diaphragm. On leaving the granulated substance the
current travels from the top tablet through the apparatus to the opposite binding
screw. Thence it either goes to earth or returns to the central station, if the
line have a double wire.
(b.) With an induction coil and the source of electricity arranged on the
premises of the subscriber. The operation in this case is exactly the same as that
of any other microphones. Instead of connecting the binding posts or screws to
the "line" wire and to the earth, or the return wire, the said binding posts serve
for fixing the ends of the wires of the primary circuit of an induction coil of
suitable resistance and of the battery.
The main advantages of the invention may be stated as follows:
:
The microphone constructed as above described, has a comparatively great
resistance, say about 400 ohins for the type described. The vibrations of the
diaphragm causes its resistance to vary, whereby are also caused very considerable
changes in the intensity of the current. The apparatus is extremely sensitive,
such sensitiveness being mainly due to the method by which the microphone proper
is suspended or secured in place viz. through the medium of a tube of elastic
material secured between the diaphragm and the conducting tablet. This sensi-
tiveness enables the improved apparatus to operate at very large distances without
the aid of an induction coil and with only one battery-cell; so that no battery need
be arranged at the subscriber's house, and all the current generating elements or
cells, necessary for distributing current to the network of wires or lines, may be
localized and kept under immediate control at the central station. This arrange-
ment also, in a very large proportion, reduces the quantity of electrical energy
expended in its operation, whether with or without an induction coil, the saving
thus realised being ascertainable by Ohm's method of calculation, and being
proportionate to the increase of the resistance of the circuit.
Dated this 10th day of Anril 1804

page_text: Improvements in Microphones.
I, HENRI CARBONNELLE, of No. 24, Rue Rogier, Brussels, in the Kingdom of
Belgium, Electrician, 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:-
The main objects of my improvements are first to construct a microphone of
great sensitiveness with comparatively great variations in the resistance, so as to
enable communications to be exchanged at great distances, without the assistance
of an induction coil, whereby the subscribers of telephone companies may dispense
with the batteries which have heretofore been fitted up on their premises, such
batteries being, instead, arranged at the central office or station; and second to
enable any desired direction to be given to the microphone.
Another, secondary, object of the invention is to enable the improved microphone
to be simply substituted for other microphones, while retaining the battery and the
induction coil, in the subscriber's house; the important advantage resulting from
such substitution being, that the quantity of electrical energy expended in the
operation of the line is materially reduced.
The microphone consists of an elastic tube forming a pellicular wall, flexible,
the orifices of which are closed by means of conducting tablets made of carbon or
any other suitable material.
The hollow space thus provided is filled with granulated coke, or other semi-
conducting material. The microphone is free at one end, while the other end is
connected to a vibrating membrane or diaphragm through the medium of a second
elastic tube, narrower and shorter than the first.
The microphone diaphragm is made of any suitable substance or material, such
as cardboard, sheet-metal, ebonite, or the like.
The microphone is enclosed in a case supported by a rod which terminates in a
metal ball. The rod consists of two portions, insulated from each other electrically;
and the same is the case with the ball, each of the parts of the rod communicating
with one of the parts of the 'ball.
The whole arrangement is fixed upon a plate or board wherein is provided
hollow space for the reception of the ball. A spiral or other spring placed at
the bottom of the said hollow space or recess presses the ball against a metal
washer whereby it is prevented from leaving the recess.
The table or board carries two binding posts or screws, one of which connected
with the main or "line" wire, and the other with the earth or the return wire.
The arrangement of the electrical connections is such that the "line" wire,
through the medium of one part of the ball, is connected to one of the tablets of
the microphone, while the return wire, or the earth, is connected to the other
tablet through the medium of the other half of the ball; the two tablets being
electrically connected with each other by the granulated coke or like material.
This arrangement enables rotary or inclining movements to be imparted to the
microphone, without interrupting the electrical connections.
In the accompanying drawing
Figure 1 is a central section of one form of my invention and
Figure 2 is a similar view of a modified form of the said invention.
A is the supporting plate or table, having a cavity or recess B at the bottom of
which is located a spiral or other spring R which presses a ball DEE against a .
metal washer F, F.
The ball D, E, E consists of two parts represented in Figure 1. Each of these
parts is electrically insulated from the other, and the two terminate respectively
in a rod D' and a tube E¹, concentric with, but insulated from each other.

page_text: A case G fixed to the tube E' carries the membrane or diaphragm m of the
microphone, such diaphragm being retained in position by a ring H fixed to or
forming part of a funnel or trumpet C.
To the centre of the diaphragm m is cemented an india-rubber tube L to which
is secured a carbon or other conducting tablet P'. A thin elastic tube M is fitted
on the said tablet P¹, while the other end of such tube M is closed by a second
tablet P'.
The cavity or recess in the tube M is filled with granulated coke or other
material of medium conducting power.
the tablet P' electrically,
grain O insulated from
Another metal strip N'
A conducting strip or plate N connects the rod D¹ to
through the medium of a wire fl soldered to a metal
the diaphragm m by a small non-conducting plate S.
similarly connects the tube E¹ to the conducting tablet P through the medium
of a wire f*.
The table or board A carries two binding posts or screws a and b, a being
electrically connected with the metal washer F by a wire d, and 6 being electri-
cally connected with the ball D by a wire e, and the spring R below the said ball.
The operation is as follows:
(a) Without an induction coil, the source of electricity being arranged at the
central station.
To the binding post b is connected the "line" wire l. A battery or other
current, sent from the ceutral office flows through e R, D, D', N¹, O, f¹ and P¹,
traverses the layer of granulated material in the tube M, and in doing so
undergoes the variations of resistance resulting from the vibrations of the
diaphragm m. On leaving the granulated substance M, the current travels
through P, N², G, E¹ E, F, d and a. Thence it either goes through t to earth,
or returns to the central station, through t if the line has a double wire.
(b) With an induction coil and the source of electricity arranged on the premises
of the subscriber.
The operation in this case is exactly the same as that of other microphones.
Instead of connecting the binding posts or screws a and b to the "line
wire and
to the earth, or the return wire, the said binding posts serve for fixing the ends of
the wires of the primary circuit of an induction coil of suitable resistance and of
the battery.
The apparatus shown in Figure 2 does not differ in any way as regards the
internal arrangement, from that shown in Figure 1. The difference is entirely
external in the sense that the apparatus shown in Figure 1 is pivoted at D, that is
to say, is enabled to turn in any direction, by means of what is usually termed a
ball and socket joint, whereas the apparatus shown in Figure 2 is the same kind
except that in this arrangement the current is reversed so that instead of starting
from the left side of the apparatus as in Figure 1, it starts from the right passing
through the wire to the tablet P3 through the granules M, to the tablet P¹ and
through wire, to the point of contact S and finally returning through the
conducting strip N¹.
The main advantages of the invention may he stated as follows:
The microphone constructed as above described, has a comparatively great
resistance. It is about 1000 ohms for the type described. The vibrations of the
diaphragm causes its resistance to vary, from 5000 to 6000 ohms and consequently
very considerable changes in the intensity of the curreut which traverses it. The
apparatus is extremely sensitive, such sensitiveness being mainly due to the method
by which the microphone proper is suspended or secured through the medium of a
regulating tube of elastic material secured between the diaphragm and the con-
ducting tablet. This sensitiveness enables the improved apparatus to operate at
very large distances without the aid of an induction coil and with only one battery-
cell; so that no battery need be arranged at the subscriber's house and all the
current generating elements or cells necessary for a distribution may be placed at
the central station. This arrangement also in a very large proportion, reduces

page_text: the quantity of electrical energy expended, whether with or without an induction
coil. This saving is ascertainable by Ohm's method of calculation, and being
proportionate to the increase in the resistance of the circuit.
Having now 'particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what [
claim is :-
First. The employment of a microphone free at one of its extremities, the other
being fixed to the membrane by means of a tube of india-rubber (or any other
elastic material) which serves to amplify the variations in the resistance commu-
nicated to the microphone by the vibrations of the membrane by diminishing the
compression of the granules during one period, but by augmenting so much
more the separation of the granules or microphonic contacts during the other
period.
Second. The employment of a pellicular tube of india-rubber or any other
elastic material very flexible and extensible serving to form a wall for containing
the granules.
Third. The mounting of the microphone above specified upon a ball forming a
joint and contact, enabling the apparatus to be turned in any direction and the
sagging of the granules to be obviated by the rotary or inclining movements
which are imparted to the system, the whole as described and represented in
Figure 1.
Fourth. The mounting of the microphone above described upon a grooved rod
serving for obtaining the contact enabling the apparatus to be turned about an
axis and the sagging of the granules to be thus obviated, the whole as represented
in Figure 2, the current passing through D¹, N' O, f¹ P¹, MP, f' G, E.
Fifth. The employment of the constructional forms based on the principles
hereinbefore set forth with reference to the apparatus shown in Figures 1 and 2 or
other constructional forms of the said apparatus having the effect of varying the
resistance and sensitiveness.
Dated this 9th day of January 1895.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.