Iм- PROVEMENTS IN ELECTRIC TELEGRAPHS
Year: 1873

page_text: LETTERS PATENT to Thomas Alva Edison, of Newark, in the State of
New Jersey, United States of America, for the Invention of "Iм-
PROVEMENTS IN ELECTRIC TELEGRAPHS.”
Sealed the 5th August 1873, and dated the 25th April 1873.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison
at the Office of the Commissioners of Patents, with his Petition, on
the 25th April 1873.
I, THOMAS ALVA EDISON, of Newark, in the State of New Jersey,
United States of America, do hereby declare the nature of the said
Invention for " IMPROVEMENTS IN ELECTRIC TELEGRAPHS," to be as follows:-
In cables and long telegraph lines there is a limit to the speed with
which perfect signals can be transmitted and received, whether the
receiving instrument consists of an electro-magnet, a galvanometer, a
relay, or a chemical telegraph instrument. This limit in speed arises
from the fact that the moment the line or cable is charged by the
battery being connected a static charge is instantly set up which is in an

page_text: opposite direction to the dynamic charge, and the tendency is to defer
the reception of the signal at the distant station, and at the moment of
breaking the battery connection the static charge disperses by dividing
at the centre of resistance and going in both directions, one part going
to the ground at the transmitting station in a direction opposed to the
battery, and the other part going towards the receiving instrument in
the same direction as the previous current from the battery. This
electrical condition is of sufficient duration to render the signals unin-
telligible at the receiving instrument after a certain speed is attained.
The time of discharge is directly proportioned to the resistance at the
points of discharge at the ends of the line, and the result is that the
speed of the instruments is limited to the speed with which the line will
free itself through the channels aforesaid.
My Invention relates to the discovery of a method of neutralizing the
effects of the static charge in any length of line or cable by balancing
the electric forces, and the discovery of a point of no electric tension or
zero as regards the static charge, so that the receiving instrument when
located at that point will be operated by the rise of tension produced by
a pulsation that is connected at such receiving instrument and made as
instantly and definitely operative as the pulsation given at the trans-
mitting station. I obtain this point of no tension by forming at the
receiving end an artificial line, having an equal resistance and electro-
static capacity or capacity for producing static charges as that of
the cable or land line, and connect this with the line or cable, and
place between the cable and the artificial line the receiving instrument,
which hence is in the centre of resistance and static accumulation; when
this balance is obtained the signals are received perfect, and the rapidity
is governed only by the strength of the battery. The artificial line is
made with an adjustable rheostat; liquid in a tube is preferable.
I connect between the receiving instrument and the earth one or more
condensers or other accumulators of static electricity, which are made
adjustable by having them in sections, and bringing one or more sections
in or out by a switch so as to increase or decrease the static charge from
the artificial cable; it may also be done by placing a very high adjustable
resistance coil between one leaf of the condenser and the artificial linc.
I maintain a very low resistance between the line and the ground at the
transmitting station so as to discharge the static current at this end as
rapidly as possibly.

page_text: The mode which I prefer is to keep my transmitting battery in circuit
at all times, and include in the same circuit another battery of equal
power with opposite poles, so that when both are in there is no current
generated, and the resistance of the wire to earth is no more than the
resistance of the battery.
The transmission of a pulsation is made when the circuit is closed
through the perforation in the paper, or otherwise, so as to short circuit
or shunt the neutralizing battery and send a current upon the line.
The current at receiving paper is shunted through a resistance so as to
preserve a constant and equal resistance which the chemical receiving
paper does not give, owing to being more damp in one place than
another. In balancing the resistance and static current the resistance
of the instrument is to be added to the line, and the resistance of the
two equalized by the same amount of resistance in the artificial cable or
line.
If the receiving instrument is out of the centre of resistance towards
the line the pulsations will be weakened by the static charge acting
against the pulsation; but if the instrument is towards the artificial
cable on the other side of the zero point the signals or characters will be
slightly prolonged owing to the static charge discharging in the samė
direction as the current. It is at this point that I prefer to place the
instrument, because by placing an electro-magnet in the shunt of the
receiving instrument I obtain enough counter discharge from that magnet
to cut off this prolongation locally, and this discharge from the magnet
will not interfere with the line that has only a local effect on the
receiving instrument to prevent tailing on the chemical paper.

page_text: .
Lord One thousand eight hundred and seventy-three, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Thomas Alva Edison, Her special licence that
I, the said Thomas Alva Edison, my executors, administrators, and
assigns, or such others as I, the said Thomas Alva Edison, my executors,
administrators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel.
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN ELECTRIC
TELEGRAPHS," upon the condition (amongst others) that I, the said Thomas
Alva Edison, my executors or administrators, by an instrument in
writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Alva Edison, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being made to the Drawing here-
unto annexed, and to the letters and figures marked thereon (that is to
say) :—
This Invention is for increasing the speed of transmission and
neutralizing the effect of static electricity at the receiving instrument.
An artificial line is employed at the opposite side of the receiving
instrument to the cable or main line, hence between such instrument
and the earth connection. This artificial line is made with a rheostat.or
resistance, and with a condenser or other accumulator of electricity, and
the artificial line is so adjusted as to resistance and static charge as to
equal the line or cable; the consequence is that the receiving instrument
is placed at a neutral point or zero as regards electric tension and static
charge, from which the static charges will discharge or equalize itself
both ways, and the message will be received with great rapidity and
reliability, according to the pulsations from the transmitting station.
In the Drawing Figure 1 illustrates my Invention in the form that I
find most generally available. The batteries a and b are connected in

page_text: opposite positions, the positive poles being towards each other, and the
negative poles connected to the ground g and line respectively. The.
transmitting instrument c is in a circuit d to the battery 6, in which
circuit d is a resistance e. When the circuit d is broken, the two
batteries a, b, neutralize each other, and there is no charge sent on the
line, but when the circuit d is closed through a perforation in the paper
or by a finger key or otherwise, the battery 6 is short circuited, and
the battery a being unbalanced sends a pulsation on the line. The
artificial line between the receiving instrument f and the earth glis
made by introducing a resistance or rheostat at r, preferably a tube con-
taining liquid with adjustable points. This rheostat is made to balance,
or equal or nearly equal the resistance of the line 7, and the instrument f
and the condenser 8 or other accumulator of static electricity is of a
capacity to about equal that of the line, hence the receiving instrument
will occupy a zero or neutral point in regard to the static charge from
which the static charges will discharge both ways to g and 9. The,
condenser or accumulator s should be in sections to bring in a greater or.
less number of sections by switches..
When the receiving instrument is chemical, the paper is preferably
prepared by dipping it in a solution of at least one pound of iodide of
potassium in one gallon of water, to which has been added a small
quantity of flour. This paper cannot be maintained at uniform moisture,
hence its resistance to the passage of electricity varies; this is com-
pensated for by the shunt circuit t, in which is a resistance u sufficient
to direct the necessary amount of electricity to the paper to make the
mark and allow the remainder to pass to the artificial line, thus the
varying condition of the paper does not change the resistance of the
line.
;
a
When an electro-magnet is energized and the circuit broken, a
pulsation is set up in the opposite direction to that passing into such
magnet; I avail of this to prevent. tailings upon the chemical paper by
so applying the electro-magnet that its discharge will aid in restoring
the line or instrument to a normal condition instantly, and at v I have
shown an electro-magnet for this purpose. It will be seen that this.
electro-magnet will discharge itself within a short local circuit containing.
the receiving instrument, and that the reactionary current therefrom
moving in the opposite direction to the main current frees the receiving.
instrument from any tailings caused by the discharge of static electricity,

page_text: and this magnet v may be employed in many places to effect the object
before named even when there is not an artificial line.
In some instances with very long lines there may be intermediate
artificial lines arranged as aforesaid, or reactionary magnets with branch
circuits to the earth to either receive drop copies in such branch circuits i
or to free the line of static electricity, and aid in obtaining the signals
perfectly at the last receiving station with the greatest rapidity.
Figs. 2 and 3 represent the same parts as before described, but in
Fig. 2 only a single battery is shown, and the resistance e is between
the line and the earth to regulate the proportion of electricity sent over 1
the line by adjusting such rheostat to prevent too great return to the
battery through such rheostat.
From the foregoing it will be understood that what is to be attained
is the instant restoration of the line at the receiving instrument to a
normal electric condition after it has been disturbed by the passage of a 1
pulsation of electricity, so that the speed will not be lessened by false or
reactionary currents, and that the chemical paper will only be marked
with a dot or dash when the transmitting instrument is operative. In
some lines this condition is promoted by the devices shown in Figs. 3
and 4, and these are preferably used in addition to the balanced circuit a
at the receiving end, as shown in Fig. 3, or may be used separately
therefrom as represented in Fig. 4. The transmitting instrument c,
circuit d, from the battery a, and the rheostat e are as before mentioned,
and the battery may be arranged with either its positive or negative to
the line, and there is a condenser h, Fig. 3, or one or more induction
coils or electro-magnets h, Fig. 4, connected in the shunt d at both
sides of the rheostat e. The effect of this is that when the circuit is
opened through the perforation of the transmitting paper the current
passes upon the line and also through the magnet or condenser / back to
the other pole of the battery, the rheostat e diverting the required
quantity. As the circuit d is broken by the intervening paper, the
reactionary discharge or condition of opposite polarity takes place from
the magnet or condenser, and acting in the opposite direction either
neutralizes the static discharge of the line or becomes a path for its
return to the earth connection of the battery, so that tailings or pro-
longations of the marks on the chemical paper at the receiving instru-
ment are effectually prevented. In long lines an electro-magnet or

page_text: resistance may be introduced in a branch circuit f to the earth to
react upon the line to effect the same object, and a small battery may be
introduced in said branch with its poles opposed to the main current
that would pass over that branch, and thereby aid the reactionary effect
of the magnet in clearing the line, and lessen the tailings upon the
chemical paper.
'
First. The artificial line on the opposite side of the receiving instru-
ment to the line or cable for positioning the receiving instrument at a
neutral point for the purposes set forth.
Second. An electro-magnet or condenser positioned in relation to the
receiving or the transmitting instrument, substantially as set forth, so
that the reactionary discharge from said magnet shall aid in restoring
the normal condition of the line cable or receiving instrument.
In witness whereof, I, the said Thomas Alva Edison, have hereunto
set my hand and seal, this Sixteenth day of September, A.D.
1873.