IMPROVEMENTS IN APPARATUS FOR TRANSMITTING MUSICAL VIBRATIONS OR SIGNALS BY MEANS OF ELECTRICITY
Year: 1875

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention
of "IMPROVEMENTS IN APPARATUS FOR TRANSMITTING MUSICAL VIBRATIONS
OR SIGNALS BY MEANS OF ELECTRICITY."-A communication from abroad
by Elisha Gray, of Chicago, County of Cook, State of Illinois,
United States of America.
ealed the 26th May 1875, and dated the 16th March 1875.
Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman, send greeting.

page_text: ELECTRICITY," and have petitioned Her Majesty to grant unto me, my
executors, administrators, and assigns, Her Royal Letters Patent for
the same, and have made solemn Declaration that the said Invention is
communicated to me from abroad by Elisha Gray, of Chicago, County of
Cook, State of Illinois, United States of America.
NOW KNOW YE, that I, the said John Henry Johnson, do hereby|
declare that the following Complete Specification, under my hand and
seal, fully describes and ascertains the nature of the said Invention, and
in what manner the same is to be performed in and by the following
statement:-
This Invention relates to apparatus for transmitting musical vibrations
by means of electricity from a distance, which apparatus is known as
the telephone, and the Invention consists in the method of and apparatus
for transmitting and receiving simultaneously, or otherwise, on a single
circuit two or more musical tones of different pitch.
It also consists in the combination of apparatus operating in the
above-named manner with a series of Morse sounders or printing
telegraph apparatus, each operated in its own local circuit, whereby it is
rendered possible to transmit two or more messages simultaneously on a
single main circuit.
And in order that the said Invention may be fully understood I shall
now proceed more particularly to describe the same, and for that purpose
shall refer to the several Figures on the annexed Sheet of Drawings,
the same letters of reference indicating corresponding parts in all the
corresponding Figures.
Figure 1 of the accompanying Drawings is a view in elevation of the
instrument used for transmitting; Figure 2 is a plan view of the same
showing the connections with the local and main circuits.
Figure 3 is a view in elevation of the instrument used for receiving,
and Figure 4 is a plan view of the same, also showing the connection
with the main and local circuits.
And Figure 5 is a Diagram showing the transmitting and the receiving
instruments connected in a single main circuit, and the arrangement of
the keys, sounders, and local circuits at the transmitting and receiving
stations, whereby two messages may be transmitted simultaneously.

page_text: In the Specification of Letters Patent dated July Twenty-ninth, One
thousand eight hundred and seventy-four, No. 2646, granted to me on
behalf of the said Elisha Gray, there is described a method of trans-
mitting musical tones of any desired pitch by sending in series of
electrical impulses corresponding in number per second to the number
of audible vibrations per second in the musical tone which it is desired
to produce through an electro-magnet, whereby the same is made to
vibrate in correspondence with the impulses, and consequently gives forth
the tone desired. This method of transmitting musical vibrations is
employed in carrying the present Invention into effect.
This Invention is also based upon the law that every vibrating string
or bar of definite thickness, length, and tension has a certain definite
rate of vibration per second at which it will always vibrate with the
production of a certain definite musical note when in motion, which note
is known as the fundamental of the bar or string.
I will now describe the construction and operation of the transmitting
and receiving apparatus employed according to this Invention, from
which description the manner in which this law of vibrating strings is
applied and utilized will be made evident. These receiving and trans-
mitting instruments are similar in their construction, but differ in the
arrangement of their electrical connections.
A is the supporting base; B, B', are two columns of metal supported
in the base; and C is a brass bar connecting these two columns. F is a
frame of metal suspended under the bar C and attached thereto, and I
is an electro-magnet supported in the frame F, whose poles extend
through the bar C. The electro-magnet on the receiving instrument
is wound with finer wire than that on the magnet in the transmitting
apparatus. D is a thin bar of steel which is stretched above the bar C
between suitable supports on the same, and has attached thereto a screw
and head L by means of which its tension may be regulated at will.
This steel bar is over the projecting poles of the electro-magnet but does
not come in contact with the same. M, M³, N, N¹, are binding screws,
by means of which connection is made with the local and main circuits.
The connections are different in the transmitting and receiving instru-
ment, and I will first describe the connections of the former, which are
shewn clearly in the plan view in Figure 2. Figure 1 shews an upright
projection H from the bar C having a contact point i therein which is

page_text: opposed to a contact piece on the bar D. O shows a contact point under
and almost in contact with the bar D, which contact point is attached to
a bar K, shown in Figure 2.
The connections are as follows and are shown in Figure 2-From the
local battery the current passes to binding screw N, then by wire c to
the projection H, then by contact point i to bar D, then by the
column B to the wire b, then through the magnet I and wire a to the
binding screw N¹. The main current enters at the screw M, then passes
by the wires e and d to arm K and contact point O to the bar D, then
by column B and wire f to the screw M. When the local circuit is
closed by means of a key in the usual manner the magnet will be excited
and the bar D will be attracted, this will break the circuit at the point i,
the spring bar D will then be released and the circuit will be again
closed through the magnet. This automatic breaking and closing will
continue as long as the circuit is closed at the key, and the result will
be that the bar will be thrown into vibration a certain number of times
per second, and will produce a tone of a pitch determined by the thick-
ness, length, and tension of the bar, and containing exactly the same
number of audible vibrations per second as these closures of the circuit
at the point i. The main circuit is closed at the point O every time the
bar D is attracted, and a series of electric impulses are consequently
transmitted to the main circuit corresponding in number to the audible
vibrations in the fundamental tone of the vibrating bar.
At the receiving instrument shown in Figures 3 and 4 the main circuit
enters at the point N, passes by wire a to the electro-magnet I, then by
the wire b to the point N¹, and thence to ground. If there is a local
circuit it passes from screw M by wire e to bar H, and the contact point
to bar D, and by wire ƒ to screw M³. When the succession of electric
currents pass through the magnet I of the receiving instrument it will
be thrown into vibration on the principle before explained, and will give
forth a musical tone of the same pitch as that given by the vibrating bar
at the transmitting instrument. If the tone given by the magnet is
the same as the fundamental of the bar D stretched above it this bar D
will be thrown into sympathetic vibration and will also give the same
tone, and during its vibration it will come against the point H and close
the local circuit. If an electro-magnet is placed in this circuit its
armature will be attracted, and as the interruptions in the local circuit

page_text: are so short as not to permit the demagnetization of the magnet and the
consequent release of the armature the latter will remain down.
Figure 5 is a diagram representing two transmitting and two receiving
instruments at opposite stations, connected by a single main circuit.
The vibrating steel bars d and e of the transmitting instruments are
tuned to a different fundamental, and the steel bars e¹, d¹, of the receiving
instruments correspond to each of these respectively. The bar e gives
the note D, C, of the scale, and the bar d the note D. Each of these
transmitting instruments has its independent local battery, which by the
electro-magnet of each instrument is operated, and each instrument is
connected as shewn in branches with the single main circuit at the
points L, M, and L³, M'.
At the receiving station the main circuit passes through the electro-
magnets of both instruments; and each instrument is connected at the
points H, N, and H', N¹, with a local circuit passing through a sounder.
The method in which the apparatus operates is as follows:-If the
local circuits be closed by depressing the key K, K¹, the bars e and d
will be vibrated, as before explained, and a series of impulses of electricity
from the main battery will be transmitted per second to the line, the
instrument C transmitting the same number of impulses as these audible
vibrations to the note C, and the instrument D transmitting the same
number of impulses as there are audible vibrations in the note D. These
electric impulses will all pass through the magnets I, I', of both the
instruments C¹, D¹, at the receiving station, and will cause them to
vibrate, but inasmuch as the bar e¹ above the electro-magnet I can
vibrate at a certain rate only it will give forth only its fundamental
note C, and the bar d¹ above the electro-magnet I will give forth only
its fundamental note D which corresponds with the tone produced at the
transmitting station. In this manner the two notes are produced
simultaneously at the receiving station.
There may be as many transmitting instruments and independent
local circuits as there are tones and semi-tones in two or more octaves,
and each vibrating bar may be tuned to different notes on the scale.
The instruments may be placed side by side, and then respective local
keys are arranged like the keys of a piano, so that a tune consisting of
notes and chords can be easily played; or the transmitting instruments
may be separated at any distance from each other. At the receiving

page_text: station there will be a corresponding number of instruments, and they
may be side by side or also separated from each other by any distance.
The transmitting instruments may be connected with an induction coil,
by which means induced currents instead of ordinary currents may be
sent to the wire.
Inasmuch as the vibration at each instrument affects the bar of the
receiving instrument only, which is tuned to the same fundamental as
the transmitting instrument corresponding to it, and as the main circuit
passes through all the magnets and is therefore never broken unless all
the instruments at the transmitting station are out of action, it is known
that the interruption of one tone by opening the key corresponding
thereto will cause the cessation at the receiver of that tonc alone,
and that the other instruments will be unaffected, so that in this manner
two or more signals may be transmitted simultaneously. These signals
may be given by short and long interruptions in a continuous tone, or
by means of a Morse sounder, which is placed in a local circuit connected
with each receiving instrument, as shewn at S, S', in the diagram.
As long as the bar vibrates the local circuit through the magnet will
close, but when these vibrations cease in obedience to the movement of
the key at the transmitting station the local circuit will open and the
armature lever will make a back stoke.
Printing instruments may be placed at these local circuits instead of
Morse sounders, which will be operated on the interruption of the local
circuit, and may be arranged in any manner which will occur to any
person familiar with the method of telegraphing and the construction of;
telegraph instruments.
Instead of receiving the vibrations upon electro-magnets, as shewn,
they may be received upon a plate of metal by the method described in
the Specification before mentioned, and by the use of resonators or organ
pipes, each tuned to a certain fundamental, any desired simple tone may a
be selected from the clang or compound tone which is produced by the
vibrating plate.
Instead of automatic circuit breakers operated electrically, mechanical
circuit breakers may be used, or the circuit may be broken by means
of platina points in the reeds of organ pipes.
This Invention admits of being carried into effect in many different
3

page_text: pertains.
Having now described and particularly ascertained the nature of tho
said Invention, and the manner in which the same is or may be used
or carried into effect, I would observe in conclusion that what I con-
sider to be novel and original, and therefore claim as the Invention
secured to me by the herein-before in part recited Letters Patent is,―
First. The method of transmitting two or more musical tones of
different pitch simultaneously or otherwise through a single line wire by
means of two or more circuit interrupters, each acting independently
but connected in the same main circuit to the line, and each transmitting
to the line a succession of impulses of electricity of equal length, the
number of impulses transmitted per second by cach circuit interrupter
being different but equal for each circuit interrupter to the number of
audible vibrations per second in a musical tone of a certain pitch, in
combination with a vibrating or resonant instrument at the receiving
station, which instrument is connected to the line, is a conductor of
clectricity, and is thrown into vibration by the impulses of electricity
transmitted through it so as to give forth a musical tone, as and for the
purposes herein-before described.
Second. In combination with two or more circuit interrupters, each
acting independently but connected in the same main circuit to the line,
and each transmitting to the line a succession of impulses of electricity
of equal length, the number of impulses transmitted per second by each
circuit interrupter being different but equal for each to the number of
audible vibrations per second in a musical tone of a certain pitch, a
vibrating and resonant receiving instrument which is a conductor of
electricity, and which is thrown into vibration by the impulses of
electricity transmitted through it so as to give forth a musical tone, and
two or more resonators, or analyzers, or organ pipes, each of which will
vibrate to a certain fundamental tone only, substantially as and for the
purpose herein-before described.
Third. In combination with two or more circuit interrupters, each
acting independently but connected in the same main circuit to the line,
and each transmitting to the line a succession of impulses of electricity
of equal length, the number of impulses transmitted by each circuit
interrupter per second being different, but equal for each to the number
of audible vibrations per second in a musical tone of a certain pitch, two

page_text: or more receiving instruments which are in the same main circuit, and
are each provided with a vibrating bar or its equivalent which is pitched
to a certain fundamental and gives forth a musical tone when the
number of electrical impulses transmitted through the receiver per
second are equal to the number of audible vibrations in the tone to
which the bar or its equivalent is pitched.
Fourth. In combination with two or more circuit interrupters, each
acting independently but connected on the same main circuit to the
line, and each transmitting to the line a succession of impulses of
electricity of equal length, the number of impulses transmitted per
second by each circuit interrupter being different, but equal for each
circuit interrupter, to the number of audible vibrations per second in a
musical tone of a certain pitch, two or more receiving instruments con-
nected in the same main circuit and each provided with a vibrating bar
or its equivalent, which bar is tuned to a certain pitch and gives forth a
musical note when the impulses of electricity transmitted through the
receiving instrument correspond in number to the audible vibrations in
the note produced by the said bar, and two or more local circuits through
sounders or printers, each of which circuits is connected to a corre-
sponding vibrating bar, and is closed when said bar is thrown into
vibration, substantially as and for the purposes herein-before described.
Fifth. A transmitting instrument consisting of the combination of the
magnet I, frame B, B', C, F, vibrating bar D, contact points O and i,
and circuits a, b, c, d, e, f, substantially as herein-before described and
illustrated by the Drawings.
Sixth. A receiving instrument consisting of the combination of the
electro-magnet I, frame B, B, C, F, vibrating bar D, contact point H,
and circuits a, b, e, f, substantially as herein-before described and
illustrated by the Drawings.
In witness whereof, I, the said John Henry Johnson, have to this
my Complete Specification set my hand and seal, this Ninth day
of March, One thousand eight hundred and seventy-five.