Year: 1886

page_text: Date of Application, 14th Sept., 1886.
Complete Left, 10th June, 1887.
Complete Accepted, 12th July, 1887.
I ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Engineer, do hereby declare the nature of this invention to be as follows:-
In this present invention I make use of intermittent pulsations of electricity, in
contradistinction to undulatory currents of electricity for the transmission of sounds,
musical, vocal, articulate, simple or compound; and I employ a method and apparatus
for causing makes-and-breakes in an electric circuit, whereby are sent into the circuit
intermittent pulsations of electricity, having all the qualities essential for the
reproduction of articulate speech.
All sounds are the effect of the vibrations of a sonorous body, and there is no
essential difference between articulate and musical sounds; for musical sounds however
the vibrations forming them follow each other at regular intervals, whereas the
intervals between the vibrations composing words are unequal.
"
For the transmission of articulate speech by means of electricity it is not necessary
that there should be a continuity of an electric current passing through a closed
circuit connecting a transmitter with a receiver; all that is necessary is that the
intermittent impulses of electricity which follow each other in the circuit should
correspond in number to those of the vibrations of the air which the voice has
produced at the transmitting end; that their varying intensities should correspond to
the varying force of the vibration of the air and that the intervals between them should
be equal to the intervals between the vibrations of the air. Under these conditions,
which are
fulfilled by this method and apparatus, articulate speech in all its
modifications can be transmitted electrically and be reproduced by an electro-magnetic

page_text: telephone receiver placed in the electric cirauit.
Some electricians have claimed and
others have denied that transmissions of articulate speech by means of electricity can
be affected only by means of instruments constructed specially to cause variations of
intensity of a continuous current in a closed circuit.
It is obvious that the variations of the intensity of a continuous current in a closed
circuit are confined within a very narrow range and must bear a very small proportion
to the maximum intensity of the initial current, whereas when intermittent pulsations
of electricity are sent into a line the variations of the intensity of the current are the
maximum variations; consequently the variations of the magnetic force of the magnet
of the telephone receiver in the circuit are the maximum variations.
The intercalation of the primary wire of an induction coil in the battery circuit with
the secondary wire in the line circuit increases greatly the intensity of the current in
the line, and as the intensity of an induced current depends directly upon the rapidity,
suddenness and extent of the variations of the electric condition of the primary wire,
it necessarily follows that intermittent impulses of electricity produce greater intensity
in the induced currents than do undulatory currents. By this apparatus the action of
the air waves upon the tympan closes the circuit momentarily by the impact of an
air wave, and simultaneously a pulsation of electricity passes into the line and the
tympan having thus been moved from its normal position returns by kinetic energy,
and two other forces act simultaneously upon it in the same direction namely the force
of the rebound after its contact with the electrode and the force of the condensation of
the air after it has passed round to the other side of the tympan, and an interruption
of the circuit takes place. The number of pulsations of electricity is equal to that of
the vibrations of the air wave and the varying intensities of the pulsations of electricity
are in proportion to the varying force which the tympan exerts in making the contacts
which momentarily close the circuit and it necessarily follows that the intervals
between the pulsations of electricity are equal to the intervals between the air waves.
In this apparatus two fundamental properties of air are utilized; Firstly equality of
the pressure of air when in motion in all directions; and secondly increase of pressure
in proportion as the density of the air is increased.
The air waves on entering the case through the mouthpiece do not fall at right
angles upon the tympan and therefore there do not occur rebounds of the air which
materially interfere with following air waves, and prevent the tympan from vibrating
in accord with the air waves.
.
In this apparatus the air waves pass into the case nearly parallel with the tympan
and as they reach the narrowest part of the air chamber the density is greatly increased
and consequently the pressure of the air on the tympan is also greatly increased and
the tympan is forced against the opposite electrode, this contact is immediately severed
by the united forces of kinetic energy of the rebound and of the pressure of the
condensed air; the movement of the tympan begins gradually, and increases in force
as the density of the air increases, and consequently the varying intensity of the electric
current is in proportion to the gradually increasing and decreasing pressure which the
tympan makes upon the electrode.
There is always a period during which a current upon closing a circuit increases in
intensity, as there is a period of decreasing intensity upon opening a circuit.
This
varying intensity of the electric current produces upon the magnet of the receiving
telephone variations of the magnetic force corresponding faithfully to the varying
intensity of the electric current.
It is preferable to employ a block of wood within which is a passage way having an
entrance with a mouth piece and an exit at one side of the case or other convenient
place. Within the passage way is a tympan with an electrode which is adapted to
make and break contact with a fixed electrode whose position may be adjustable.
Instead of one of the electrodes being placed upon the tympan it may be carried on
the longer arm of a lever whose shorter arm is connected with the tympan.
The second electrode may if desired be carried on an arm or pendulum so that it also
may vibrate.

page_text: The tympan may be of any materials possessing elasticity either naturally inherently
or else having it imparted to it by external conditions such as would be in the case of
a limp membrane such as a piece of bladder which is strained and held by its edges.
I prefer to use mica for the tympan.
The electrodes can be of carbon or metal but platinum or molybdenum is preferred.
One of the electrodes should be flat presenting a surface of about one quarter of an
inch more or less in measurement and the other electrode is preferably rhomboidal.
The passage for the air waves is contracted towards the centre of the tympan on
both sides thereof, so that the air waves from the mouth piece are caused to act
powerfully upon one side of the tympan, and then such air waves passing around in
the passage way are condensed against the other side of the tympan by the narrow
passage through which it must pass; and then such air waves pass out through the
exit opening.
1000

page_text: I, ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex, M.I.M.E.
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:
In this invention use is made of intermittent pulsations of electricity in contra-
distinction to undulatory currents of electricity for the reproduction of sounds, musical,
vocal, articulate, simple or compound, by a method and apparatus for causing
$6 'makes and breaks" in an electric circuit whereby are sent into the circuit
intermittent pulsations of electricity having all the qualities essential for the
reproduction of articulate speech.
All sounds are the effect of the vibration of a sonorous body and there is no
essential difference between articulate and musical sounds; for musical sounds however
the vibrations forming them follow each other at regular intervals whereas the intervals
between the vibrations composing words are unequal.
For the reproduction of articulate speech by means of electricity it is not necessary
that there should be a continuity of an electric current passing through a closed
circuit connecting a transmitter with a receiver all that is necessary is that the
intermittent impulses of electricity which follow each other in the circuit should
correspond in number with those of the vibrations of the air which the voice has
produced at the transmitting end; that their varying intensities should correspond to
the varying force of the vibrations of the air and that the intervals between them
should be equal to the intervals between the vibrations of the air. Under these
conditions which are fulfilled by this method and apparatus articulate speech in all its
modification can be reproduced by an electro-magnetic telephone receiver placed in
the electric circuit.
It is obvious that the variations of the intensity of a continuous current in a closed
circuit are confined within a very narrow range and must bear a very small proportion
to the maximum intensity of the initial current whereas when intermittent pulsations
of electricity are sent into a line the variations of the intensity of the current are the
maximum variations; consequently the variations of the magnetic force of the magnet
of the telephone receiver in the circuit are the maximum variations.
The intercalation of the primary wire of an induction coil in the battery circuit
with the secondary wire in the line circuit increases greatly the intensity of the current
in the line and as the intensity of an induced current depends directly upon the
rapidity, suddenness and extent. of the variations of the electric condition of the
primary wire it necessarily follows that intermittent impulses of electricity produce
greater intensity in the induced currents than do undulatory currents.
By this

page_text: apparatus the action of the air waves upon the tympan closes the circuit momentarily
by the impact of the air wave and simultaneously a pulsation of electricity passes into
the line, and the tympan having thus been moved from its normal position returns
by kinetic energy; and two other forces act simultaneously upon it in the same
direction namely, the force of the rebound after its contact with the electrode and the
force of the condensation of the air after it has passed round to the other side of the
tympan and an interruption of the circuit takes place. The number of pulsations of
electricity is equal to that of the vibrations of the air waves and the varying intensities
of the pulsations of electricity are in proportion to the varying force which the tympan
exorts in making the contacts which momentarily close the circuit; and it necessarily
follows that the intervals between the pulsations of electricity are equal to the intervals
between the air waves.
In this apparatus two fundamental properties of air are utilized; firstly, equality
of the pressure of air when in motion in all directions; and secondly increase of
pressure in proportion as the density of the air is increased.
In this apparatus the air waves on entering the case through the mouthpiece do not
fall at right angles upon the tympan and therefore there do not occur rebounds of the
air which materially interfere with following air waves and prevent the tympan from
vibrating in accord with the air waves.
To prevent these rebounds the air waves pass into the case nearly parallel with the
tympan and as they reach the narrowest part of the air chamber the density is greatly
increased, and consequently the pressure of the air on the tympan is also greatly
increased and the tympan is forced against the opposite electrode this contact is
immediately severed by the united forces of kinetic energy of the rebound and of the
pressure of the condensed air; the movement of the tympan begins gradually and
increases in force as the density of the air increases and consequently the varying
intensity of the electric current is in proportion to the gradually increasing and
decreasing pressure which the tympan makes upon the electrode.
There is always upon closing a circuit a period during which a current increases in
intensity as there is a period of decreasing intensity upon opening a circuit. This
varying intensity of the electric current produces upon the magnet of the receiving
telephone variations of the magnetic force corresponding faithfully to the varying
intensity of the electric current.
The passage for the air waves is contracted opposite to the centre of the tympan on
both sides thereof so that the air waves from the mouth piece are caused to act
powerfully upon one side of the tympan and then such air waves passing around in
the passage way are condensed against the other side of the tympan by the narrow
passage through which they must pass and then such air waves pass out through the
opening provided therefor.
In the accompanying drawings:
Fig. 1 represents a mid-horizontal section of an instrument in which the tympan is
connected by an electrode on each side thereof to one pole of the battery, and placed
between two electrodes electrically connected to the other pole of the battery and
arranged to be vibrated between these two electrodes and to make contact alternately
on each of these electrodes; in this manner closing and opening the circuit twice as
rapidly as when the tympan makes contacts on only one electrode on one side of it.
Fig. 2 is a transverse view of Fig. 1 on line x-x and fig. 3 is a diagrammatic view
thereof showing the method of intercalating the primary and secondary wires.
In a block of wood or other suitable material A, A there is a passage-way BBB
having an entrance with a mouthpiece M. and an exit at E on one side of the block or
at any other convenient place; a tympan T is placed in the air chamber B B so that
it will lie at an angle with the entrance hole M; the frame F holding the tympan
closes the air chamber B at the top bottom and side near to the entrance M leaving
the passage-way B B open at the back thereof so that the air waves entering the
mouthpice M fall upon the tympan T and pass around said tympan and find their exit
at the hole E. On each side of the centre of the tympan is an electrode C, C¹¹

page_text: connected to one pole of a battery, opposite, very close to, but not touching either of
the electrodes C, C are two electrodes P P¹ both directly connected or through the
primary wire of an induction coil to the other pole of the same battery. It may
sometimes occur that the electrode C may get out of its proper adjustment and make
a slight contact on the electrode P-or the electrode may from the same cause
make a slight contact on the electrode P¹-In either of these cases the efficiency
of the instrument is not impaired because the impact of the air waves will instantly
sever those contacts and the tympan must continue its vibration in response to the
vibrations of the air waves thus closing or opening, or opening and closing the circuit ;
when the tympan is forced against the opposite electrode P this contact is immediately
severed by the united forces of kinetic energy, of the rebound and of the pressure of
the condensed air; and these united forces press the tympan back beyond its normal
position of rest and cause it to make a contact on the electrode P¹.
F is the frame, T the tympan which is secured to the frame by the ring R by means
of screws. C is a small disc of any hard material which will conduct electricity
attached to the centre of the tympan and is connected by a conductor d to one pole of
a battery G the other pole being conducted to one end of the primary wire of an
induction coil I. A bridge D spanning the centre of the tympan is attached to the
frame at its two ends by two supports and at the centre of the bridge a screw passes
through carrying at its end P a material which will conduct electricity and is connected
by the wire K to one end of the primary wire of an induction coil I; a similar disc ("
and bridge D¹ and screw P¹ are placed similarly on the opposite side of the frame F.
TT represents the tympan; P P¹ two electrodes connected together to one end of
the primary wire of an induction coil; C C₁ two electrodes on the tympan connected
together to one pole of a battery the other pole being connected to the primary wire;
S the secondary wire connected to the ground; S¹ the other end of the secondary wire
connected to the telephone.
Fig. 4 is a section of this improved telephone representing one of the electrodes C
at the centre of the tympan and the other electrode P in the form of a screw which is
adjustable into proximity with the electrode on the tympan from the outside of the
case A. Fig. 5 is a similar view with a lever L the short arm of which is connected
to the centre of the tympan and the long arm carries the electrode P the electrode C
being fixed in the frame F. Fig. 6 is a section of this transmitter with one electrode P
at the end of a pendulum P".
The invention is not limited to this particular arrangement as there are many ways
in which a tympan and electrodes may be arranged.
The tympan may be of any materials possessing elasticity but preferably of cork,
glass or mica.
The tympan should not be clamped tightly around its circumference because when
so clamped it bulges out more or less on one side or on the other side, thereby greatly
impairing its true vibratory movement; in order to avoid this evil the edge of the
tympan may be placed between two rings of soft paper, felt or soft india rubber the
said rings to be clamped together so as not to interfere with a lateral movement of the
tympan nor to cause any straining of its molecules.
The electrodes may be of carbon, metals or alloys. Molybdenum or hard gas retort
carbon is preferable for the reason that it resists the wear produced by the contacts
better than any other kind of carbon does.
Carbon has been used in microphones since April 1877 and it is generally believed
to be the best material for varying the current in a closed circuit without interrupting
it and that it is the worst and most inefficient for contact points of electrodes of an
intermittent circuit breaker. A long series of experiments has demonstrated that in
an instrument for sending into a conductor very rapid intermittent impulses of
electricity it is very advantageous to use carbon for one or both of the electrodes or
contact points when the contacts of the electrodes are caused by the force of air waves
as in the instrument herein described.
The superiority of carbon in an instrument in which the contacts are made very

page_text: rapidly and are caused by the action of air waves is due to the fact that no oxidation
of the points of contact takes place and consequently its capacity for conducting
electric currents remains constant according to the pressure of the electrodes against
each other.
It is well known that carbon is composed of perfectly homogeneous molecules and
this molecular condition although it is an imperfect conductor prevents the evil effects
which are liable to be produced at every change of potential in imperfect conductors
whose molecules are not homogeneous. My correspondent has discovered that
molybdenum is composed of homogeneous molecules and being a much better conductor
than carbon it presents great advantages for electrodes where rapid intermittent
impulses of electricity are required.
My correspondent is aware that carbon has been used in a microphone which is
essentially a closed circuit and the results are produced by variations of pressure of
the two electrodes against each other whereas this instrument works on a principle
exactly the reverse namely by "makes and breaks" in an open circuit. But he is
not aware nor does he believe that either carbon or molybdenum has been used or
described in any printed book in any country for one or both electrodes in an
in a conductor.
instrument made to produce "makes and breaks
It is necessary that the tyimpan should be made of a material which is not liable
to be affected by moisture or heat and it is found that glass and mica are the best
materials for a tympan in an instrument where rapid "makes and breaks" of the
current are to be made because of the very great elasticity of them.
My correspondent is aware that all of these materials have been used in a microphone
the essential elements of which are that the electrodes should always be in contact and
that the variations of the current shall be produced by more or less pressure of the
electrodes against each other but he is not aware nor does he believe that
glass or mica has been used nor been described in any printed book in any country
for a tympan in an instrument made to produce actual makes and breaks in a
conductor.
Having now particularly described and ascertained the nature of the said invention
as communicated to me by my foreign correspondent, and in what manner the same
is to be performed, I declare that what I claim is
1. The combination in a telephone transmitter of an air chamber having inlet and
exit openings and a continuous passage around the tympan, and a tympan located
therein at other than a right angle to the path of the air waves substantially as
set forth.
2. The apparatus herein described consisting of a tympan situated in an air
chamber and arranged to be acted upon on both sides successively by the same
air waves and electrodes or contact points controlled thereby substantially as
set forth.
3. The combination of the tympan with a case having an air passage extending
around the tympan so that the air waves will act first on one side of the tympan and
afterwards on the opposite side of it substantially as set forth.
4. The method herein specified of controlling the vibrations of the tympan in a
telephonic transmitter consisting in directing the air impulses against one side
of the tympan and then returning the same so that such air impulses act in the
opposite direction upon the other side of the said tympan substantially as specified.
5. The combination with the tympan and electrodes in a telephonic transmitter
of a case having a return passage way that concentrates the air waves first on one
side of the tympan and then on the other side substantially as set forth.
6. The combination in a telephone, of a tympan having on the centre of each
side thereof an electrode of the same pole of a battery opposite to each of which
electrodes is an electrode of the other pole of the battery substantially as specified.
7. In a pneumatic instrument for sending intermittent impulses of electricity into
a conductor by means of rapid "makes and breaks" of the circuit caused by the
action of air waves the use of electrodes of carbon.

page_text: 8. In a pneumatic instrument for sending intermittent impulses of electricity
into a conductor by means of rapid "makes and breaks" of the circuit caused
by the action of air waves the use of one electrode of carbon and the other electrode
of metal.
"
9. In a pneumatic instrument for sending intermittent impulses of electricity into a
conductor by means of rapid "makes and breaks of the circuit caused by air waves
the use of electrodes of molybdenum.
10. In a pneuumatic instrument for sending intermittent impulses of electricity into
a conductor the employment of a tympan made of glass.
11. In a pneumatic instrument for sending intermittent impulses of electricity into a
conductor tympan made of mica.