Improvements in Microphones.
Year: 1899

page_text: Date of Application, 10th Mar, 1899
Complete Specification Left, 28th Nov., 1899-Accepted, 3rd Mar, 1900
Date of Application, 1 Mar, 050
Complete Specification Left, 28th Nov., 1899-Accepted, 3rd Mar, 1900
PROVISIONAL SPECIFICATION.
Improvements in Microphones.
I, PIERRE GERMAIN, of Fontenay aux Roses, Department of Seine, in the
French Republic, Inspector of Telegraphs, do hereby declare the nature of this
invention to be as follows:
This invention relates to certain improvements in the construction of micro-
phones, which improvements enable telephonic transmission to be effected under
special conditions as regards intensity thereby allowing reception in a loud
tone by a magnetic receiver of the ordinary type. These improvements consist
on the one hand of a body or substance of special composition intended to
replace the carbon, and on the other hand, of the application of heat to improve
the transmission.
The body or substance intended to replace the carbon ordinarily employed
is characterised by its being a very intimate mixture of carbon preferably
baked or prepared at a high temperature and of tenuous metallic particles;
it is in short metallized in the mass; it possesses a great conducting power and
affords great intensity and clearness of transmission, especially in granulate
microphones.
I will now set forth the method according to which I proceed to manufacture
this semi-conducting body for microphones.
I form a mixture as intimate as possible of powder of carbon such as that
ordinarily employed for microphones, or preferably of graphited carbon, and
of a metallic oxide the metal of which possesses preferably a coefficient of high
electrical conductivity as well as a high fusing point. What I term graphited
carbon is gas coke or gas-coal (charbon de cornue) baked or prepared at a
very high temperature by means of the electrical furnace.
I heap up this mixture and heat it to a red-heat, moulding it to the desired
shape-rods, lozenges or blocks intended to be granulated or pulverised.
If the metallic oxide entering into the composition of this substance, which
oxide can be incorporated either directly as an oxide or as a corresponding salt
of the metal, cannot be reduced at the time of such baking or preparation, I
afterwards reduce it by any suitable reduction method. I might also incorporate
the metal directly under the form of metallic particles; for certain metals,
this incorporation under the form of metal, may be indispensable.
I do not limit myself to any particular metal nor to any particular physical
state of the metal nor to any state of particular combination for its mixture,
with the carbon this mixture of the metal may be direct in the metallic state
or under the form of an oxide or under the form of this metal, which com-
positions are afterwards reduced by any suitable means.
It must be understood that I may employ this semi-conducting substance
for the manufacture of powder, of granulate, of rods, of lozenges or of carbon of
other shapes, intended for all carbon microphonic systems in which it may
advantageously replace the carbon.
The other improvement in telephonic transmission is that during such trans-

page_text: mission heat the semi-conducting bodies or substances of the microphone.
That is very important and I thus obtain results quite remarkable as to power
and intensity of transmission; this raising of the temperature can be effected
by any convenient means and I do not restrict myself io any special source
of calorific energy: I can obtain this from the microphonic current itself, from
a special current supplied by a primary or secondary battery, or from any
suitable heating device.
This process
for increasing the force of transmission is particularly
advantageous when applied to a microphone constructed with a semi-conducting
substance in the granulate state prepared in the manner I have above described,
but I may apply it to all granulate microphones, those with rods or others,
having either ordinary carbon or having the semi-conducting substance pre-
pared as I have above explained.
I wish to state that I do not limit the application of the foregoing improve-
ments to any particular microphone but I will describe a transmitter of my
invention working according to these improvements and which affords excellent
transmission.
Such transmitter consists of two lozenges of semi-conducting material con-
nected by a flexible wall or wrapper of incombustible tissue; the receiver thus
formed is filled with granulate of semi-conducting substance..
This whole is solidly secured to a vibrating diaphragm, which preferably is
of glass, one of the lozenges being fixed to this membrane. The whole is
enclosed within a box or casing: a bell or trumpet-mouth is arranged in front
of the membrane and between this latter and the trumpet-mouth is a recess
belled out from the neck of the latter up to the vibrating diaphragm.
The two wires of the circuit are connected to the two lozenges to which they
are jointed or soldered, these lozenges being metallized exteriorly (by means of
electro-deposition.)
As already explained I describe this microphone only by way of example, as
an apparatus working very effectively and fitted with the improvements which
I have above described: but I reserve the application of these to all kinds of
microphonic transmitters.
Improvements in Microphones.
I, PIERRE GERMAIN, of Fontenay aux Roses, Department of Seine, in the
French Republic, Inspector of Telegraphs, 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:-
This invention, relates to certain improvements in the construction of micro-
phones, which improvements enable telephonic transmission to be effected under
special conditions as regards intensity thereby allowing reception in a loud
tone by a magnetic receiver of the ordinary type. These improvements consist
in the first place. of a body or substance of special composition, intended to
replace the carbon, and, in the second place, in the application of heat to improve
the transmission."

page_text: The body or substance intended to replace the carbon ordinarily employed
is characterised by its being a very intimate mixture of carbon preferably
prepared at or heated to a high temperature and of minute metallic particles;
it is, in short, metallized in the mass; it possesses a great conducting power
and affords great intensity and clearness of transmission, especially in granulate
microphones. I may employ any suitable metal; I generally use silver or
copper on account of their high efficient of electrical conductivity.
I will now set forth the method according to which. I proceed to manufacture
this semi-conducting body for microphones.
I form a mixture as intimate as possible of powder of carbon such as that
ordinarily employed for microphones, or preferably of graphited carbon, and
of an oxide of a metal, which metal-possesses preferably a coefficient of high
electrical conductivity as well as a high fusing point. What I term graphited
carbon is gas coke or gas-coal ("charbon de cornue") baked or prepared at a
very high temperature by means of the electrical furnace.
I heap up this mixture and heat it to a red-heat, moulding it to the desired
shape rods, lozenges or blocks intended to be granulated or pulverised.
If the metallic oxide entering into the composition of this substance, which
oxide can be incorporated either directly as an oxide or as a corresponding salt
of the metal, cannot be reduced at the time of such baking or preparation, I
afterwards reduce it, by any suitable reduction method. I might also incorporate
the metal directly under the form of metallic particles; for certain metals,
this incorporation under the form of metal, may be indispensable. When
the metal is incorporated under the form of a salt, I take a sulphate for copper
and an azotate for silver. As regards the proportions, they may
average 6 parts of carbon to one of metal.
be on
an
I do not limit myself to any particular metal nor to any particular physical
state of the metal nor to any state of particular combination for its mixture
with the carbon; this mixture of the metal may be direct in the metallic state,
or under the form of an oxide or under the form of this metal, which com-
positions are afterwards reduced by any suitable means.
It must be understood that I may employ this semi-conducting substance
for the manufacture of powder, of granulate, of rods, of lozenges or of carbon or
other shapes, intended for all carbon microphonic systems in which it may
advantageously replace the carbon.
The other improvement in telephonic transmission is that during such trans-
mission I heat the semi-conducting bodies or substances of the microphone.
That is very important and I thus obtain results quite remarkable as to power
and intensity of transmission: this raising of the temperature can be effected
by any convenient means and I do not restrict myself to any special source
of calorific energy; I can obtain this from the microphonic current itself, from
a special current supplied by a primary or secondary battery, or from any
suitable heating device.
This process for increasing the force of transmission is particularly
advantageous when applied to a microphone constructed with a semi-conducting
substance in the granulate state prepared in the manner I have above describes,
but I may apply it to all granulate microphones, those with rods or others,
having either ordinary carbon or having the semi-conducting substance pre-
pared as I have above explained.
I wish to state that I do not limit the application of the foregoing improve-
ments to any particular microphone but I will describe a transmitter of my
invention working according to those improvements and which affords excellent
transmission.
Fig. 1 of the annexed drawings is a sectional side elevation of a transmitter,
and Fig. 2 is a rear view of the same.
This microphonic transmitter contains as a means for modifying the electric
current, a box or chamber formed of two carbon lozenges a ỗ connected together

page_text: by a flexible wall of woven material the space within being filled with semi
conducting granulated this box or chamber is fixed by means of one of the
carbon lozenges at e to a vibrating membrane or diaphragm f; the whole is
placed in a casing h furnished with a bell-mouth intended to direct the sound-
waves upon the membrane: the chamber filled with granulate is interposed
within the electric circuit which by means of two wires gg is connected to the
lozenges and 7.
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. A semi-conducting substance for the formation of granules, powders, blocks,
lozenges and rods of microphones, composed of a mixture of carbon preferably
baked at a high temperature and of metal in a divided state, this metal being
mixed with the carbon either directly or in the form of oxides or salts, and
the mixture then baked, substantially as described.
2. In combination with microphone transmitters of any system and particularly
with those arranged with the semi-conductive bodies which form the object of
my first claim, the use of any method of heating to raise the temperature of
the semi-conductive bodies of the microphone which affect the electric current,
as described and illustrated in the annexed drawing.
3. A microphone comprising two lozenges a b joined by a flexible wall or
wrapper & the chamber so formed being filled with granules, the coil so formed
being in one with the vibrating diaphragm f and the whole being arranged
in a casing with a bell or trumpet i substantially as described and illustrated
in the annexed drawing.