IMPROVEMENTS IN ELECTRIC TELEPHONY
Year: 1885

page_text: I, JAMES GRIEVE LORRAIN, of 3 Vernon Chambers, Southampton Row, in the
County of Middlesex, Consulting Engineer, do hereby declare the nature of my
invention for IMPROVEMENTS IN ELECTRIC TELEPHONY to be as follows:-
My invention which relates to Electric Telephony, has for its object the trans-
mission and reproduction of speech and of other sounds by means of Electricity;
and consists of an instrument capable of acting either as a transmitter, for pro-
ducing, under the influence of sound waves, rapid variations of current in a
conductor or system of conductors, or as a receiver for producing, under the
influence of such variations of current, mechanical vibrations of the air similar to
and uniform with those which actuate the transmitter.
In carrying my invention into effect, I may employ an instrument consisting
essentially of two conductors arranged in proximity and suitably disposed with
regard to one another, and of a moveable screen of suitable material so arranged
and disposed with respect to the said conductors that when the instrument is
acting as a transmitter the said screen may vibrate under the influence of sound
waves in such manner that the inductive influence of the one conductor upon the
other may vary with such vibrations, and when the instrument is acting as a
receiver the said screen may vibrate under the influence of the variations of
current in such manner as to produce sound waves or air pulsations.
Instead of having the screen moveable and capable of vibration, it may be fixed,
and one or more of the conductors so arranged and disposed as to be moveable and
capable of vibration in such manner, when the instrument is acting as a trans-
mitter, as to vary the inductive influence of the one conductor upon the other by
varying the proportion of the conductors screened from or exposed to each other:
and, when the instrument is acting as a receiver, capable of vibrating under the
influence of the variations of current received from the transmitter, and in 80
vibrating causing sound waves or air pulsations.
To increase the said inductive action, or to act the part of a brake upon the said .
vibrations or upon the variations or pulsations of current, I may employ a core or

page_text: cores or mass or masses of iron or other magnetic material or a magnet or magnets
suitably arranged and disposed.
In order to concentrate or increase the effect of the sound waves upon the
vibrating part or parts of the transmitter, and to concentrate or increase the effect
of the vibrating part or parts of the receiver upon the air so as to produce sound
waves or air pulsations, I may employ a plate, or diaphragm or its equivalent.
To gain increased effect I may multiply or increase the number of parts of the
instruments.
It will be readily understood that instead of actuating the transmitter by sound
waves, it may be actuated by tapping or pressing, for the purpose of transmitting
signals.

page_text: I, JAMES GRIEVE LORRAIN, of Norfolk House, Norfolk Street, London, W.C.,
Consulting Engineer, do hereby declare the nature of my invention for IMPROVE-
MENTS IN ELECTRIC TELEPHONY and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement:-
My invention, which relates to Electric Telephony, has for its object the trans-
Inission and reproduction of speech and other sounds by means of electricity. It
consists of an instrument capable of acting either as a transmitter or as a receiver.
When acting as a transmitter it fulfils the usual function of a transmitter in
telephony, namely that of producing under the influence of sound waves rapid
variations of current in a conductor or system of conductors; and when acting as
a receiver it fulfils the usual function of a receiver in telephony, namely that of
producing under the influence of variations of current mechanical vibrations of
the air or sound waves similar to and uniform with those which actuate the
transmitter.
In carrying my invention into effect I employ an instrument, being that above
referred to, which consists essentially of two conductors and a screen. The two
conductors are arranged in proximity to one another, and the screen occupies a
position between them. In one form of my instrument the two conductors are
fixed, and the screen is movable. In another form the screen is fixed, and the two
conductors are movable. In a third form the screen and one of the conductors are
fixed, and the other conductor is movable. In a fourth form one of the conductors
is fixed, and the other conductor as well as the screen is movable.
I prefer to attach the movable part or parts of the instrument to a diaphragm
serving the usual purpose of a diaphragm in telephony, that is in order to con-
centrate or increase the effect of the sound waves upon the said movable part or
parts when acting as a transmitter, and when acting as a receiver to concentrate
or increase the effect of the movable part or parts upon the air so as to produce
sound waves or air pulsations. The said conductors may be arranged in any
convenient manner. One convenient manner of arranging them is in spirals or
coils, and such spirals or coils may be flat straight or annular. The several parts
of the instrument are so disposed with regard to one another that when in action
the extent of surface of one conductor exposed to or screened from the other will
vary according to the vibrations of the movable part or parts.
When used as a transmitter I connect up my instrument in such manner that
one of the two conductors shall be in circuit with a battery, or other source or
reservoir of electricity, so that a current shall pass through this conductor: and
the other conductor I connect to the main circuit. When used as a receiver
I connect up my instrument so that one of the conductors is in connection with
the main circuit and the other conductor I close upon itself by putting its two
ends in electrical connection with each other. For convenience of description
I call in the case of the transmitter that conductor the primary one through which
the current from the battery or other source or reservoir of electricity is passed,

page_text: and that the secondary one which is connected to the main circuit: whilst in the
case of the receiver I call that conductor the primary one which is in connection
with the main circuit, and that the secondary one which is closed upon itself. By
the term "main circuit "I mean the circuit connecting the two stations between
which telephonic communication takes place, and which may consist of any of the
usual forms of circuit such for example as a metallic circuit or a line and earth
circuit.
The action of my invention is as follows:-Let us take the case where the two
conductors are fixed and the screen, in this case attached to a diaphragm, is
movable. The sound waves impinging on the diaphragm of the transmitter will
cause the screen to vibrate in such manner as to vary the amount of surface of the
secondary conductor exposed to the inductive influence of the current in the
primary conductor, and so vary the energy of the induced current transmitted
through the main circuit. The variations of current passing through the primary
conductor of the receiver will cause variations in the current induced in the
"secondary conductor, and these variations will cause the screen to move in unison
with such variations and so cause vibrations in the diaphragm which will produce
sound waves similar to and uniform with those which actuate the transmitter.
From this description the action of my invention in the case of the other forms
of instrument hereinbefore referred to will be readily understood. In all these
forms the effect is the same whichever parts are fixed and whichever movable-
the amount of the one conductor screened from the other will vary with the sound
waves in the case of the transmitter, and with the electric undulations or variations
of current in the case of the receiver.
To increase the inductive action of the one coil upon the other I sometimes
employ a core or cores or mass or masses of iron or other magnetic material, (but
preferably iron); and such a core or mass I shall hereinafter refer to by the term
" intensifier."
To gain increased effect I sometimes multiply the several parts of the
instruments.
For the purpose of transmitting signals, instead of actuating the transmitter by
means of sound waves, sometimes actuate it by tapping on the diaphragm where
such exists. Where no diaphragm exists I effect this by tapping on the screen
itself.
In order that my invention may be the better understood I shall now proceed
to describe it with reference to the diagrams on the accompanying sheets of
drawings.
.
Figures 1 and 2 show diagrammatically one form of my invention. The primary
coil A. and the secondary coil B are formed of thin ribbons of metal wound each in
a flat spiral as shown. C is a vibrating diaphragm having attached to it the
screens c₁, which interpose more or less between the primary and secondary coils
as the diaphragm vibrates. I sometimes in this form of instrument dispense with
the second screen and replace it by a fixed strip of iron acting as an intensifier.
Figure 1 is a sectional plan on line X, and Figure 2 a section on line Y. These
figures here show my instrument as a transmitter. For the sake of clearness
I have not continued the lines X and Y across the whole width of the figures.
Figures 3 and 4 show diagrammatically another form of my invention. A is
the primary coil wound spirally in annular form, and B is the secondary coil
wound in a similar manner. C is a diaphragm carrying the screen c₁ which
interposes more or less of its surface between the primary and secondary coils
when C is vibrated, and so varies the inductive influence of the one coil upon the
other. When I employ intensifiers with this form of instrument I generally place
them inside the convolutions of the coils A and B. Figure 4 is a plan and Figure 3
a section on line Z.
Figures 5 and 6 show diagrammatically another form of my invention. A is a
primary coil and B a secondary coil in this case both wound in a straight form.
C is a diaphragm carrying a perforated screen c₁. D is a similar perforated screen

page_text: fixed to the case E. When the diaphragm C vibrates the perforated screen c₁ acting
in unison with it partially opens or closes the perforations in the fixed screen D,
and so varies the inductive influence between the coils. Figure 5 shows an
elevation, and Figure 6 a section of this form of apparatus. When I employ an
intensifier with this form of instrument I generally place it outside the coil B and
make it form a tubular lining to the case E.
I wish it to be understood that though in the description of these Drawings I
call A the primary coil and B the secondary, yet B may be the primary coil and A
the secondary, whenever such an arrangement is most convenient, the connections
being altered accordingly as will be readily understood.
In practice I prefer to use two instruments at each station, one connected up as
a transmitter, and the other as a receiver: but I sometimes use only one instru-
ment at each station; and when this is the case I employ a switch, which, when
the instrument is to be used as a transmitter, places the primary conductor in
circuit with the battery herein before referred to, and connects the secondary
conductor with the main circuit; and which, when the instrument is to be used as
a receiver, places the primary conductor in connection with the main circuit, and
closes the secondary conductor upon itself.
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. The improvement in Electric Telephony consisting of the transmitting
instrument substantially as set forth.
2. The improvement in Electric Telephony consisting of the receiving instrument
substantially as set forth.
3. In a telephone transmitter the combination of two conductors and a screen
either with or without a diaphragm and either with or without an intensifier
arranged and acting substantially as set forth.
4. In a telephone receiver the combination of two conductors and a screen
either with or without a diaphragm and either with or without an intensifier
arranged and acting substantially as set forth.
1000