IMPROVEMENTS IN THE ELECTRICAL TRANSMISSION OF SPEECH
Year: 1884

page_text: COMPLETE SPECIFICATION.
CHARLES ELMER ALLEN of Adams Birkshire Co. State of Massachusetts U.S.A.
Electrician do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE ELECTRICAL TRANSMISSION OF SPEECH" and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:-
My Invention relates to the reproduction of articulate speech by means of
electrical variations produced in an electric circuit by sound waves, and it has for
its object to produce in an electric circuit strong and powerful electric variations
for the above purposes..
It also has for its object to overcome the disturbing effects ordinarily apparent in
the receiving instruments caused by electrical disturbances produced by other means
than the sound waves which are to be reproduced.
It also has for its object to enable the reproduction of sound waves at great
distances by the aid of strong and powerful eléctrical variations.
It is a well known fact that in the ordinary transmitters it is impracticable to
use a heavy current without producing breaks and sparks between the electrodes,
which has the effect to produce a disagreeable rattling sound in the receiver and
to injure the electrodes, thereby hindering the perfect transmission and reception of
articulate speech.
On account of the comparative weakness of the electric currents than can be
used with the ordinary transmitters, the induced currents sent to line are so small
that external induction, leakage, retardation and earth currents produce such serious
effects upon them as to impair their proper action upon the receivers necessary to
produce good articulation and more especially is this apparent where it is attempted
to use such instruments in transmitting variations produced by sound waves over
long lines.
I avoid these objections by the use of my instruments by which I am enabled to
send very powerful currents to line which are enough stronger than the external
disturbing currents and influences to allow such an arrangement of the receiving
instruments that they will act as a sieve, so to speak, or in other words be operated
by the stronger variations only, the weaker variations not appreciably affecting the
diaphragm of the receiver.

page_text: The transmitting apparatus consists of a number of pairs of electrodes so arranged
that the current from a powerful battery passes through them in multiple arc and
thence through the primary of a large induction coil.
The secondary of the said induction coil forms part of the main line containing
tho receiving instrument.
The relations of these electrodes to each other, is controlled by variations in
electro magnets operating the same, the said magnets being situated in a local
circuit including a transmitter of the ordinary construction.
The receiving apparatus consists in general of a helix having a core made up of
soft iron wire located in the main line, and another similar helix and corc, located
in proximity to the first and adapted to be adjusted to and from the same and
including in its circuit an ordinary receiving telephone.
It will be apparent that the variations in the relations of the electrodes, arrangod
so that the main battery current will pass through them in multiple arc, will be an
enlarged reproduction of the variations in the circuit in which the ordinary
transmitter is located, said circuit being controlled by the action of the electrodes
arranged in multiple arc. By the particular manner in which these electrodes are
mounted and acted upon by the magnets, as will be more particularly hereinafter
described, I also produce a mutual action between them, which greatly aids in
avoiding detrimental breaks and sparks in the circuit when powerful currents are
used.
It will be seen that the receiving instrument proper derives its operative current
by induction from the helix and core in the main line and that by properly
adjusting the relation of the two helices a point can be reached where the
externally induced currents will be unable to operate tho receiver, while the more
powerful currents transmitted over the line and controlled by the sound waves
will operate the receiver.
Referring to the accompanying Drawings:
Fig. 1 is a side elevation of one form of the contact operating mechanism.
Fig. 2 is a plan of the same.
Figs. 3 and 4 are side and plan views of the means for adjusting the magnets.
Figs: 5 and 6 aro details.
Figs. 7 and 8 are detail views showing one modified form of the contact levers.
Fig. 9 is a diagram showing an arrangement of my instrument in a circuit for
communicating between distant stations.
Fig. 10 is a section of one form of seive or receiving apparatus.
* Figs. 11 and 12 are side and detail views of the same.
Figs. 13 and 14 show respectively a sido and plan view of a modified form of my
Invention and
Fig. 15 is a diagram showing the arrangements of the circuits.
Fig. 16 and 17 are respectively plan and side views and
Fig. 18 is a detail view of another form of my Invention.
A metal base piece A having standards B, B, is provided with a longitudinal
slot a having a recessed block 6 secured at its center.
Passing through the slot a is a right and left hand screw rod c, having a disk d
secured at or near its middle which disk is fitted into the recess in the stationary
block b.
Fitted to slide in the slot a and screw threaded for the reception of the screw
rod c are two right angled standards cc to the upper ends of which are secured the
electro magnets D D.
In the lower part of each of the standards B B are fitted two screws E E and
insulated therefrom, by proper means. The ends of these screws E E are recessed
so as to form bearings for the pivot rods ee which are rigidly fastened to the lower
extremities of two crossing levers F F. To the upper parts of these crossing levers
are secured the armatures ff in such a position as to be directly opposite the cores
of electro magnets D D.

page_text: The relation of the magnets to the armatures may be adjusted by turning the
screw c by means of the thumb nut c¹ the right and left hand threads thereon
operating to cause both magnets to approach and recede from the armatures
equally and when the proper adjustment is attained the standards may be secured
in place by the set screws g I.
•
In the upper ends of standards B B are fitted two thumb screws h h having lock
nuts ii and their inner ends are provided with soft rubber tips jj adapted to bo
brought into contact with the upper ends of crossing levers F F.
On the inner sides of the levers F F and below their point of crossing are secured
the electrodes preferably composed of a carbon disk and a platinum point
mounted upon suitable supports.
At each corner of the base and properly insulated therefrom, is secured a
binding post 1 and 2 of which are connected with the local circuit containing the
ordinary transmitter and the coils of the electro magnets D D and 3, 4, which
are in circuit with the electrodes k k are connected with and form a branch of tho
multiple arc circuit.
From this construction and arrangement the operation will be as follows:
Sound waves are produced in the vicinity of the transmitter T which is preferably
used without an induction coil and produce electrical variations in the local circuit
connected with the coils of the electro magnets D D the cores of which act upon
the armatures of the cross levers F F and cause them to vary the relations of the
electrodesk in accordance with the variations of the electric current. Theso
variations of the electrodes produce corresponding variations in the current from
the large local battery which passes through the electrodes and the primary of the
largo induction coil I the secondary of which forms part of the main line.
It will be seen by this that when several of these instruments are connected with
their controlling magnets in series with the transmitter T and the electrodes in
multiple are with a heavy battery and the primary of the induction coil I very
strong and powerful electric variations may be sent to line without danger of
sparks or undue breaks as the strong current divides and portions of it pass
through separate sets of electrodes all operated upon and controlled in unison by
the variations produced by, the transmitter T and operating with mutual action
towards each other.
Such an arrangement of instruments is shown diagramatically in Fig. 9, in which
T is the ordinary transmitter in the local circuit connected in series with the electro
magnets D, D, the cores of which operate upon the crossing levers F F to which
the electrodes karo connected the current from the main battery M B passing
through the various sets of electrodes in multiple arc and through the primary of the
induction coil I.
One end of the secondary of the induction coil is grounded while the other goes
to the distant station and the receiving instrument in the main line circuit.
In order to receive the powerful variations sent to line by my improved
transmitting instruments, and at the same time avoid receiving these variations
produced by causes other than the sound waves to be reproduced, I have devised an
improved receiving apparatus, shown in detail in Figs. 10 11 and 12.
A box or cylinder M of hard rubber or similar material contains two helices O P
the former of which is secured to the bottom of the box and has its terminals
connected with the binding posts 5, 6. The other helix P is suitably connected
with the top N of the box M which is adapted to screw in or out of the end of the
box, I have shown a connecting rod Q which is provided with a lock nut q, and a
washer q', secured in a recess in the cover N so that the cover may be turned
without turning the helix P, a pin p, attached to the side of the box operating in a
alot or recess p¹, in the helix-bobbin. The terininals of the helix P are secured to
binding posts 7, 8.
Cores of soft iron wire may be provided for the helices O and P.
:
From this construction it will appear that if one of the helices is connected with
the line wire by means of its binding posts and the other is connected with a
b

page_text: circuit including an ordinary receiver by its binding posts, the relations of the twọ
helices may be so adjusted that the variations in the electric current produced by
external disturbances in the one will not be able to appreciably affect the receiving
instrument in the circuit of the other, while the stronger and more powerful
variations sent to line by the transmitting instruments described will appreciably
affect the receiver and produce the desired vibrations only.
The instrument therefore acts as a "sieve" or screv taking up the desired
variations which predominate in strength over those produced by external causes.
It is evident that an ordinary receiver can be so adapted as to have the relation
between its diaphragm and magnet so adjusted as to accomplish the same result.
The advantages of these instruments will be seen to be in fact that they produce
such strong and powerful variations in the line that the light induced or other
currents caused by disturbing influences practically have no effect upon the receiver
as it may be adjusted in such a manner as not to be affected materially by such
currents and at the same time it will be operated by the heavy and powerful
variations sent to line by the transmitting instruments, so as to reproduce the
sound waves distinctly.
It will also be seen that by using a large battery and induction coil and a large
number of electrodes such powerful currents may be sent to line that they may be
made to traverse long distances and effectually reproduce the sound waves.
By using the ordinary transmitter in the arrangement above described the
variations produced thereby may be said to form a pattern of which the powerful
variations produced by the aggregate effect of the electrodes in-the-main-battery-
circuit are a fac-simile enlargement, and by passing these through the induction
coil they are converted into alternate positive and negative variations.
It is evident that without departing from the spirit of my Invention the induction
coil can be omitted and the main battery current thrown directly to line, if desired,
also that the controlling electro magnets may be connected in multiple arc instead
of series and that the transmitter T, may be provided with an induction coil, and
the magnets in circuit with the secondary thereof, or the armatures therefor may be
polarized either one of them or both; also that the main line battery may be
connected for quantity instead of for intensity as shown.
It is also evident that the instruments of this system of transmission may bo
arranged so as to successfully be used in telephonic repeating at intermediate
stations over long lines.
The currents from the main battery may be made to include coils arranged so as
to act upon the levers carrying the clectrodes, and these coils may be either in
series or multiple arc. In this arrangement I obtain what is known as the reaction
of the current upon the electrodes.
In Figs. 13, 14, and 15, I have shown such an arrangement, upon the base A¹ are
fixed the supports B¹ B¹ and CC and the standard D' to which the
levers E E E E are pivoted upon insulating bearings on a rod supported in
standards D' D¹.
Levers E and E2 and E³ and E' are respectively connected by the armatures e¹
and e² and e³ and e' for the magnets F1, F¹, and G¹ G¹. These magnets are in the
form of an ordinary horse shoe with short cores and the yokes are provided with
studs H, H¹, having adjusting nuts upon their ends and surrounded by coiled.
springs and are sustained in recesses in the supports C¹ C¹ and their position in
relation to the, armatures is regulated by the adjusting nuts and springs bearing
upon the sides of the supports B¹ B' through holes in which the stems H' of the
magnets pass.
At or near the top of the levers are attached cross pieces I¹ I¹ against which
bear adjusting screws JJ having rubber or other elastic tips as shown and near
the lower ends of the levers are secured the cross bars K¹ K¹ one of which carries
an extended block of carbon L¹ and the other being provided with a series of
platinum tipped screws M¹. Binding posts suitably connected to the various parts
are attached to the base and insulated therefrom.

page_text: The lower set of magnets F¹ F, are in the circuit including the transmitter,
while magnets G¹ G₁, are in a local circuit including the electrodes K¹ L' and the
primary of an induction coil, the secondary of which goes to line.
From this arrangement it will be evident that the variations in the primary
current passing through the coils and magnets F¹. F¹ will cause variations in the
circuit passing through the electrodes and magnets G', G', which variations will
cause said magnets to reach upon the electrodes through the levers in a well known
manner.
°
In the Figures above referred to the platinum electrodes act conjointly in multiple
arc upon the strip of carbon, it is evident that. these platinum electrodes may be
insulated from each other and act upon separate carbon electrodes also insulated
from each other and that these electrodes may be connected in series, multiple are
or any desired manner.
In Fig. 15, I have shown several such instruments diagramatically, supposing
each instrument to have a single pair of electrodes.
The local battery, including the transmitter, is connected to the lower set of
magnets in series and each pair of electrodes is connected in a local circuit having.
its individual battery and including the upper or reacting magnets and the primary
of an induction coil, the secondary of each induction coil being connected in
multiple arc with the main line, which is provided with a heavy battery which may
be connected for quantity of intensity.
Instead of having separate batteries for each circuit as shown, a single battery
may supply each electrode circuit. When the form of instrument shown in
Figs. 13 and 14 is used the currents after passing through the electrodes in multiple
arc and jointly through the reacting magnets may then pass through the primaries
of several small induction coils, in series of one large induction coil or several
instruments of this kind may be arranged in combination as shown in the diagram
Fig. 15.
".
In Figs. 16, 17 and 18 is shown another form of instrument embodying this
Invention. Upon the base A' aro mounted in standards D', two sets of permanent
magnets B, to which are attached soft iron cores surrounded by helices C*. These
magnets are made adjustable by suitable means as shown. Upon the pivot screws
88 of a standard S, is mounted a bar or armature of soft iron or steel to one
end of which is secured a projection G* of brass or other non-magnetic material.
Upon a standard H is mounted a metal plate I supporting a resistance varying
device of any suitable construction, the one shown consisting of a carbon disk f
upon which is a platinum foil disk g, connected to a binding screw and upon
the foil rests a glass disk * having a button of any suitable material. A metal
ring is supported upon insulating material d' enclosing the resistance varying
medium.
Suitable adjustable springs at attached to screws b' in posts c' regulate the initial
pressure of the projection G upon the button.
One of the coils or helices C is in the secondary circuit of an induction coil, the
primary of which contains the primary transmitter and the other helix C* is in the
circuit including the resistance varying medium.
The operation of the device is apparent from what has been said—the alternating
currents from the induction coil of the transmitter passing through the coil C
causes variations in the pressure of the projecting arm G', upon the resistance
varying medium, which will cause variations in the circuit passing through it and
the other helix C, and these variations will react upon the resistance varying
medium through the armature F in a manner well understood.
It is evident that the various modifications suggested are applicable to this form
of device and that the resistance varying medium or electrodes may be multiplied
and arranged in various ways as above indicated, it being preferable however, to
use an induction coil in connection with the primary transmitter, so as to send
reverso currents to the polarized magnets cores..

page_text: t
The main line may be arranged to react upon the electrodes instead of the main
local current.
An additional main battery may be inserted in the line containing the secondary
of the induction coil.
It is also evident that each set of electrodes may be connected in circuit with the
primary of a separate and individual induction coil, the secondaries of which may
be connected in multiple are or series circuit or multiple arc series. Or each pair
of electrodes may be connected with a separate local circuit having its own battery
and embracing the primary of a separate and individual induction coil, it being
understood that the variations in these local circuits are controlled by variations in
the circuit which is acted upon by the sound waves.
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. In the art of telephony, the method substantially as herein set forth of
obtaining great variations of a powerful current in the line which consists in
causing variations in a local battery circuit to reproduce enlarged variations of
a more powerful current in another circuit.
2. In the art of telephony the method substantially as herein set forth, which
consists in producing great variations in the powerful currents in the line and
adjusting the receiving apparatus so that it will respond only to such strong
variations thereby practically freeing the apparatus from the disturbances produced
by extraneous influences.
3. In the art of telephony the method substantially as herein set forth of avoiding
the disturbances produced by extraneous influences in the receiving instruments,
which consists in screening the variations caused by extraneous influences and
causing only the greater variations in the powerful currents sent to line to
appreciably affect the receiving apparatus.
4. The combination substantially as herein set forth with pivoted supports
carrying electrodes of electro magnets adapted to operate said supports in 3
accordance with variations in the current passing through said coils.
5. The combination substantially as herein set forth with the pivoted support
carrying electrodes included in one circuit of electro magnets included in another
circuit adapted to operate the said levers so as to cause variations in the circuit
including the electrodes in accordance with the variation in the said electro 3
magnets.
6. The combination substantially as herein set forth with a local circuit including
a transmitter and a series of magnet coils of another circuit including a series of
electrodes and the electrode supports, the arrangement being such that variations
in the current of the first circuit produced by the transmitter therein will cause 40
enlarged variations in the more powerful current of the second circuit.
7. The combination substantially as herein set forth with a local circuit including
a transmitter and a series of magnet coils, of another circuit including a series of
electrodes, and the primary of an induction coil, and a receiving instrument in the
main line forming the secondary of the induction coil the arrangement being such 45
that variations in the local circuit caused by the transmitter will cause enlarged
variations in the more powerful currents of the second circuit and the receiver is
so adjusted that it will respond to these latter variations only.
8. The combination substantially as herein set forth with a local circuit including
a transmitter and a number of magnet coils arranged in series, of another circuit 50
including a battery, a number of pairs of electrodes arranged in multiple arc and
the primary of an induction coil, and a main line including the secondary of the
induction coil and a receiver.
9. The combination substantially as herein set forth with a primary circuit
including a transmitter and a number of coils, of another circuit including a 55
battery, a number of electrodes and a number of coils and the primary of an

page_text: induction coil and a main line inducing the secondary of the induction coil and a
receiver, the arrangement being such that variations in the primary circuit shall
operate to produce variations in the second circuit which latter variations are
caused to react upon the electrodes in said circuit, thereby sending greater variations
to line.
10. The combination substantially as herein set forth with a main line over
which powerful currents are sent, of a receiving apparatus consisting of two coils,
one of which is included in the main line and the other is adjustable in relation
thereto, whereby the disturbing currents produced in the main line may be screened
and only the more powerful currents will be rendered appreciable in the receiver.
Dated this 25th day of March 1884.
CHARLES ELMER ALLEN,
By his Agents,
W. P. Thompson & Boult.