Improvements in Microphones.
Year: 1893

page_text: Date of Application, 3rd May, 1893
Complete Specification Left, 16th Jan., 1894-Accepted, 7th Apr., 1894
PROVISIONAL DIEULEVATION.
Improvements in Microphones.
We, ERNEST JULES PIERRE MERCADIER and JOSEPH MICHEL ANIZAN
both of 16 Rue Drouot, Paris, France, Engineers, do hereby declare the nature of
this invention to be as follows:-
This invention has reference to microphones.
According to our invention we employ a vibrating plate of a homogeneous
substance and of dimensions calculated so as to avoid the natural vibrations of the
plate; we employ a plurality of carbon pencils; we have isochronism of the
vibratory movements of all the pencils by using a single contact block or bar fixed
at only one point of the vibrating plate and in its centre and we improve the
mobility of the pencils.
Our microphone is composed of a circular plate of homogeneous glass placed
vertically. The dimensions of this plate are calculated in such manner that its
fundamental sound is higher than Doh 5, that is to say that of the upper limit of
the height of the sounds of the human voice. We thus prevent the natural
vibrations of the plate from mixing with those which have been communicated to
it by the voice and thereby altering the timbre. This plate the edges of which
are held all round has always in the middle a centre of vibration. We fix at this
centre a pencil-carrying block or bar which is itself of carbon.
In front of the glass plate, that is to say between the mouth of the person who
speaks into the microphone and the vibrating plate, we place wire gauze or a metal
or other grating which protects the glass plate from breakage, but the special
object of which is to diminish what may be called the explosive effects of certain
articulations b, k, p, t, v, which, predominating over the others in articulated speech
near a membrane, contribute much to alter the timbre.
The block or bar for the microphonic contacts which is itself of carbon has the
form of a rectangular parallelopipedon. It is perforated at right angles to its axis
and in its middle with a quadrangular hole. This bar is fixed at the centre of the
glass plate by a metallic rod of square section terminated by a threaded part upon
which a nut is screwed. A washer or piece of ebonite or other suitable material
separates the bar from the glass plate so that the connection between the glass
plate and the block or bar for the microphonic contacts is made at a single point
and by the single surface of the separating washer. We form on the lower face of
the block or bar four cavities to receive the upper ends of the carbon pencils.
If the metallic rod above described be sufficiently long and be covered with an
insulating coating we can place several blocks or bars one bebind another and by
suitably arranging several rows of pencils we can obtain on the same vibrating
plate several microphonic groups which can have their special induction coils and
batteries. The secondary circuits of the induction coils would be arranged in
series or in surface. We can thus have on the same induction coil a common
secondary wire and several primary wires wound parallel.
The carbon pencils are each mounted on a metal tube terminated at its lower
end by a metal plug in which a conical cavity is formed. The carbon pencils can
be of circular or polygonal section and the cavities in the contact block or bar
may be of circular or other form.
The pencils above described rest by their lower conical cavity on metal pins
which are fixed on bars likewise metallic. These bars rest on the frame of the
microphone and not on the vibrating plate; this plate therefore supports only the
weight of the contact block or blocks. In this manner we prevent simultaneous

page_text: microphonic vibrations at the two ends of the carbon pencils, because it is
impossible to prevent these two movements, although synchronous, from having a
difference of phase, which may interfere with a good reproduction of the timbre of
the voice.
Each row of carbons has a special pin-carrying bar which allows of two rows of
pencils being grouped either in series or in surface. We can alternatively terminate
the metallic mounting of the pencils in the form of a pin which would rest in a
corresponding cavity of the bar, but the first mode of mounting is preferable
because it gives more stability to the carbon pencils.
As a simple and practical means of changing the contacts of the pencils we
adopt the following arrangement:
On one side of the frame which carries the vibrating plate is a flat or coiled
spring and a rigid bar. On the inner surface of the other side of the frame is a
rigid bar terminated by a rod which passes through the frame and has a ring
outside the apparatus. Between the two bars are silk or other elastic threads or
cords the length of which is such as to pass round the mounting of the two pencils
corresponding with each row and to remain slack when at rest. When the ring is
pulled in the one direction the silk threads are tightened, nip the pencils and move
them slightly in the one direction. When the spring is left to itself the pencils
which always turn on their supporting points, turn in the opposite direction. From
numerous trials we have found that the second action of the carbons is more active
than the first and that the initial point of contact of the carbons changed. The
silk threads being slack when at rest have no action on the vibrations of the
carbons.
The pin-carrying bars, that is those which support the pencils, being fixed on
the frame of the apparatus the vibrating plate only carries the block for the
microphonic contacts. This arrangement allows of regulation, not by the inclination
of the vibrating plate as has hitherto been done, but by the inclination of the
carbons; it is effected by moving the pin-carrying bars in or out.
These can
further be separated from the frame by layers of caoutchouc, felt or other suitable
substance for deadening the vibrations which might be transmitted through the
frame to the pencils.
The connections of the primary circuit of our microphone are for each group of
microphonic contacts the same as those of other microphones. But we place at
will at two points of the primary circuit a shunt of determined electric resistance
which allows of diminishing the intensity of the telephonic effects. By this means
a microphone constructed to communicate at a great distance can, owing to the
action of an interrupting commutator, serve at will either for the long distance or
for urban or domestic communications.
We also find that with the employment of the shunt we diminish the loudness of
the voice on the most sonorous syllables, which has hitherto prevented the appli-
cation of micro-telephonic apparatus as domestic stations. This shunt can be
placed either where the communications of the pencils take place or at the binding
screws of the primary circuit of the induction coil, or both at the pencils and at
the primary circuit of the induction coil. We thus obtain a certain result by
shunting the secondary circuit of the induction coil.
We obtain a nearly analogous result by employing instead of the shunt a suitably
calculated resistance which we place in the primary microphonic circuit. When
with a powerful microphone we wish to communicate at a long distance we put the
interrupting commutator upon the contact; we consequently suppress by the short
circuit the effect of the resistance. When with the same microphone we wish to
communicate at a short distance we open the interrupting commutator and the
resistance introduced into the primary circuit weakens the intensity of the current
and the telephonic effects are weakened. It will therefore be seen that the working
of the interrupting commutator is inverse according to whether the shunt or the
resistance is employed. In order to diminish the intensity of the telephonic effects
it is necessary to put the interrupting commutator upon the contact when the shunt

page_text: is employed. It is necessary on the other hand to break the contact if the
resistance is employed.
When we employ several microphonic contact blocks placed one behind another
and corresponding rows of pencils we can utilize induction coils having several
primary circuits and one common secondary circuit. In this case each primary
circuit has a set of microphonic contacts, a special battery and a special shunt.
The handle of the interrupting commutator is arranged so as to close or open at
will all the shunt circuits at once.
This system is quite distinct from those in which the simultaneous and opposite
effects of the microphonic contacts are utilized. In what is known as the Freeman
microphone for example two resistances are alternately increased and diminished,
but our invention is entirely different. We unite on the same membrane two or
more different microphones the effects of which instead of being opposed are
parallel and become added to each other without change of phase.
Dated this 3rd day of May 1893.
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent.
Improvements in Microphones.
I, ERNEST JULES PIERRE MERCADIER and JOSEPH MICHEL ANIZAN both
of 16 Rue Drouot, Paris, France, Engineers, 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 has reference to microphones.
According to our invention we employ a vibrating plate of a homogeneous
substance and of dimensions calculated so as to avoid the natural vibrations of the
plate; we employ a plurality of carbon pencils; we have isochronism of the
vibratory movements of all the pencils by using a single contact block or bar fixed
at only one point of the vibrating plate and in its centre and we improve the
mobility of the pencils.
Our microphone is composed of a circular plate of homogeneous glass, placed
vertically-see V in Figures 1 and 2 of the accompanying drawings. The
dimensions of this glass plate are calculated in such manner that its fundamental
sound is higher than Doh 5, that is to say that of the upper limit of the height of
the sounds of the human voice. We thus prevent the natural vibrations of the
plate from mixing with those which have been communicated to it by the voice and
thereby altering the timbre. This plate the edges of which are held all round has
always in the middle a centre of-vibration. We fix at this centre a pencil-carrying
block or bar which is itself of carbon.
In front of the glass plate that is to say between the mouth of the person who
speaks into the microphone and the vibrating plate we place wire gauze G or a
metal or other grating which protects the glass plate from breakage, but the
special object of which is to diminish what may be called the explosive effects
of certain articulations b, k, p, t, v, which, predominating over the others in articulated
speech near a membrane, contribute much to alter the timbre.
The block or bar for the microphonic contacts which is itself of carbon has the
form of a rectangular parallelopipedon. It is perforated at right angles to its
axis and in its middle with a quadrangular hole. This bar is fixed at the centre of
tle glass plate by a metallic rod of square section (Figure 1) terminated by a
threaded part upon which a nut is screwed. A washer or piece of ebonite or other
suitable material separates the bar from the glass plate so that the connection
between the glass plate and the block or bar for the microphonic contacts is made

page_text: We form on
at a single point and by the single surface of the separating washer.
the lower face of the block or bar four cavities to receive the upper ends of the
carbon pencils.
If the metallic rod above described be sufficiently long and be covered with an
insulating coating we can place several blocks or bars one behind another and by
suitably arranging several rows of pencils we can obtain on the same vibrating
plate several microphonic groups which can have their special induction coils and
batteries. The secondary circuits of the induction coils would be arranged in series
or in surface. We can thus have on the same induction coil a common secondary
wire and several primary wires wound parallel.
The carbon pencils are each mounted on a metal tube terminated at its
lower end by a metal plug in which a conical cavity is formed (see Figure 3).
The carbon pencils CC₁ can be of circular or polygonal section (see Figures 5
and 6) and the cavities in the contact block or bar may be of circular or other
form (see Figures 7 and 8).
The pencils above described rest by their lower conical cavity on metal pins
which are fixed on bars likewise metallic. These bars rest on the frame of the
microphone and not on the vibrating plate; this plate therefore supports only
the weight of the contact block or blocks (Figures 1 and 2). In this manner we
prevent simultaneous microphonic vibrations at the two ends of the carbon pencils
because it is impossible to prevent these two movements although synchronous from
having a difference of phase which may interfere with a good reproduction of the
timbre of the voice.
Each row of carbons has a special pin-carrying bar which allows of two rows
of pencils being grouped either in series or in surface. We can alternatively
terminate the metallic mounting of the pencils in the form of a pin as seen in
Figure 4 which rests in a corresponding cavity of the bar, but the first mode of
mounting is preferable because it gives more stability to the carbon pencils.
.
As a simple and practical means of changing the contacts of the pencils we adopt
the arrangement shown in Figures 9 and 10. On the left hand side of the frame
which carries the vibrating plate is a flat or coiled spring and a rigid bar t₁ t'₁-
On the inner surface of the right hand side of the frame is a rigid bar t, t', to
which is attached a rod which passes through the frame and has a ring N outside]
the apparatus. Between the two bars t₁ t, and t₂ t', are silk or other elastic threads
or cords the length of which is such as to pass round the mounting of the two
pencils corresponding with each row and to remain slack when at rest. When the
ring N is pulled from left to right the silk threads are tightened, nip the pencils
and move them slightly from left to right. When the spring is left to itself the
pencils which always turn on their supporting points, turn in the opposite
direction. From numerous trials we have found that the second action of the
carbons is more active than the first and that the initial point of contact of
the carbons is changed. The silk threads being slack when at rest have no action
on the vibrations of the carbons. Figure 10 shows the arrangement of two carbon
pencils only.
The pin-carrying bars, that is those which support the pencils, being fixed on
the frame of the apparatus, the vibrating plate only carries the block for the
microphonic contacts. This arrangement allows of regulation not by the inclination of
the vibrating plate as has hitherto been done but by the inclination of the carbons;
it is effected by moving the pin-carrying bars in or out. These can further be
separated from the frame by layers of caoutchouc, felt or other suitable substance
for deadening the vibrations which might be transmitted through the frame to the
pencils.
The connections of the primary circuit of our microphone are for each group of
microphonic contacts the same as those of other microphones. But we place at
will at two points of the primary circuit a shunt of determined electric resistance
which allows of diminishing the intensity of the telephonic effects. By this means
a microphone constructed to communicate at a great distance can, owing to the

page_text: action of an interrupting commutator I Figure 14 serve at will either for the long
distance or for urban or domestic communications.
We also find that with the employment of the shunt we diminish the loudness
of the voice on the most sonorous syllables which has hitherto prevented the
application of micro-telephonic apparatus as domestic stations. This shunt can be
placed either where the communications of the pencils CC' take place (see Sh
Figure 11) or at the binding screws of the primary circuit 1-1' of the induction
coil (see Figure 12) or both at the pencils and at the primary circuit of the
induction coil (see Figure 13). We can also obtain a certain result by shunting
the secondary circuit 2-21 of the induction coil, but it is well to place the shunt
as in Figure 11 because the disagreeable effects produced when for any reason
there is interruption in the contacts of the pencils are avoided.
не
When
We obtain a nearly analogous result by employing instead of the shunt a
suitably calculated resistance R Figure 15 which we place in the primary
microphonic circuit. When with a powerful microphone we wish to communicate
at a long distance we put the interrupting commutator I upon the contact;
consequently suppress by the short circuit the effect of the resistance R.
with the same microphone we wish to communicate at a short distance we open
the interrupting commutator I and the resistance R introduced into the primary
circuit weakens the intensity of the current and the telephonic effects are weakened.
It will therefore be seen that the working of the interrupting commutator I is
inverse according to whether the shunt Sh Figure 14 or the resistance R
Figure 15 is employed. In order to diminish the intensity of the telephonic effects
it is necessary to put the interrupting commutator I upon the contact when the
shunt is employed. It is necessary on the other hand to break the contact if the
resistance R is employed.
When we employ several microphonic contact blocks placed one behind another
and corresponding rows of pencils we can utilize induction coils having several
primary circuits and one common secondary circuit. In this case each primary
circuit has a set of microphonic contacts, a special battery and a special shunt Sh
(see Figure 16). The handle of the interrupting commutator is arranged so as to
close or open at will all the shunt circuits at once.
This system is quite distinct from those in which the simultaneous and opposite
effects of the microphonic contacts are utilized. In what is known as the
Freeman microphone for example two resistances a and b Figure 17 are alternately
increased and diminished; but our invention is entirely different.
We unite on
the same membrane two or more different microphones the effects of which instead
of being opposed are parallel and become added to each other without change of
phase.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim in respect of microphones is :-
1. In a microphone, microphonic contacts obtained between carbon blocks or
bars having the form of a rectangular parallelopipedon with a quadrangular hole
at right angles to their axes and in their middle, the said blocks or bars being
fixed at a single point to the centre of the vibrating plate, and carbon pencils
held in metallic fittings and supported at their lower end by metal bars through
the intermediation of metal pins entering conical cavities, substantially as herein-
before described.
2. In combination with the microphonic contacts referred to in Claim 1 of the
following, either together or separately, and all substantially as bereinbefore
described, that is to say :-
(a) As vibrating plates, plates of homogeneous glass of circular form and of
such dimensions that their fundamental sound is higher than Doh 5, with or
without wire gauze or a grating in front of the plate to prevent or diminish
the explosive effects of certain articulations of the voice.

page_text: 3) Means of changing the contacts comprising elastic threads or cords which
pass round the pencils and enable by a simple movement the microphonic
contacts of the pencils with their blocks or bars to be displaced.
) A shunt introduced at will by means of an interrupting commutator
between two points of the primary microphonic circuit or fixed at the
binding screws of the secondary circuit of the induction coil to enable the
apparatus to be used either for communicating at a great distance or for
urban or domestic transmissions.
7) In lieu of a shunt and to weaken at will the intensity of the telephonic
effects, a resistance introduced or not in the primary circuit and opening or
closing an interrupting commutator.
) When several blocks or bars are placed one behind another and several
rows of corresponding pencils are employed, induction coils having several
primary circuits and one common secondary circuit, each primary circuit
having in this case a set of microphonic contacts, a special battery and a
special shunt, the handle of the interrupting commutator. being arranged so
as to close or open at will all the shunt circuits at once.
ated this 15th day of January 1894.
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent.