IM- PROVEMENTS IN DUPLEX AND MULTIPLEX TELEGRAPHS
Year: 1875

page_text: LETTERS PATENT to Thomas Alva Edison, of Newark, in the State of
New Jersey, United States of America, for the Invention of "IM-
PROVEMENTS IN DUPLEX AND MULTIPLEX TELEGRAPHS."
Scaled the 25th March 1875, and dated the 2nd February 1875.
PROVÍSIONAL SPECIFICATION left by the said Thomas Alva Edison
at the Office of the Commissioners of Patents, with his Petition,
on the 2nd February 1875.
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 DUPLEX AND MULTIPLEX TELEGRAPHS," to be
as follows:-
The objects of this Invention are,—
1st. To enable two operators, one at each terminal station, to transmit
simultaneously over one wire, and two other's, one at each of such
stations, to receive such messages; and in this respect my Invention is
an improvement in duplex telegraphs.
Price 8d.1

page_text: αν Caca
transmit signals, and four other operators, two at each terminal station,
to receive the messages, without either interfering necessarily with the
other, and to use only one line wire in so doing. This portion of my
Invention is designated a quadruplex or multiplex telegraph.
3rd. To allow either operator to signal the distant station so that the
message may be repeated to rectify any inaccuracies or omissions.
4th. To repeat a message received over one wire by either the duplex
or quadruplex telegraph into another circuit to send the same to another
or distant station.
I remark that the duplex and quadruplex telegraphs can be used
by the number of persons named, or they can be used singly by one
operator at each end; and furthermore, that by bearing in mind the
general principles of operation herein set forth the details of the arrange-
ments of the batteries and metallic circuit connections will be apparent
to an electrician.
One of the persons sending a message employs a key that is con-
structed so that it does not break the circuit, but that it connects more
or less of the battery to the line; thus one operator works a distant
instrument by a rise and fall of the electrical tension or energy, The
other operator has a key that is made to reverse the circuit connections
without breaking the continuity of circuit, and thus his message is
indicated by a change in the polarity of the current sent regardless of
the tension or energy of the battery power. These keys of the sending
station are either operated directly by hand or preferably by an electro-
magnet, a local circuit and a finger key for each, and both ends of the
line are similarly provided with two transmitting keys, batteries, and
circuit connections, and also with the receiving instruments next
specified; but I remark that the receiving instruments are also capable
of use in duplex telegraphy under systems of transmission heretofore
employed, wherein the rise and fall of tension produce the respective
indications at the two receiving instruments.
The instrumentalities at each end for receiving the messages consist,
1st, of a receiving magnet; 2nd, of a polarized receiving magnet; 3rd,
of an artificial line; 4th, of adjustable rheostats or resistances; and
5th, of local circuits containing batteries and electro-magnets forming

page_text: 66
the instruments for receiving the message by sound by a Morse
receiver," or in any other convenient manner.
The instruments that are required for either the quadruplex or the
duplex system of receiving are selected and arranged with reference to
the transmitting devices employed. With the duplex system operated
by rise and fall of tensiou, as aforesaid, the polarized relay will not be
required, but the receiving magnet is to be placed at a point that is
neutral to the message sent from that station but where it will be
influenced by the message received. To this end the artificial linc
composed of a rheostat preferably with a condenser in a shunt around
the reheostat is arranged so that its discharge may compensate the static
discharge from the line, and this artificial line is at one side of the
receiving instrument or instruments, and the line connection at the
other; and the pulsations sent from the home station will be balanced
in the receiving instrument at that station, but such receiving instru-
ment will respond to the pulsations from the distant station because the
distant pulsations are unbalanced.
The receiving magnet is sometimes made with two helices on one
core, and one helix is in the artificial line and the other in the main
line, and they are so wound as to oppose each other, and hence the care
is not magnetized by the outgoing current, but it is by the current from
the distant station operating in the one helix. The polarized receiving
magnet employed in the quadruplex telegraph is similarly arranged and
positioned so as to be uninfluenced by the current sent, but to respond
to the change of polarity in the current received; and when made with
four helices around the two cores the instrument becomes a differential
polarized relay or magnet.
When the condenser is used in a shunt around the reheostat, either in
the artificial line or between the receiving instrument and main line,
its charge and discharge as the circuit is opened or closed neutralizes or
compensates for the effect of the static charge and discharge that takes
place at that same time, because the condenser is arranged so as to
discharge in opposition to the static discharge.
In the receiving, instruments aforesaid when arranged for the quadru-
plex telegraph it is preferable to arrange the local circuit that is worked
by such receiving instrument, so that the sounder is operated by the
unbalanced force of a second local battery when the first local circuit is

page_text: broken by the armature of such receiving instrument, thereby the
sounder will be more distinct in its response to the pulsation on the
line.
The main battery of the line is subdivided into two portions of
unequal power for the object hereiu-before named, and one portion is
always upon the line and the other portion is applied or removed by the
key of one of the operators to increase or lessen the electrical energy.
With this battery it is preferable that a resistance be inserted in a branch
passing around the battery to the key, arranged to present the same
resistance to currents from the distant station that that portion of the
battery itself presents when it is connected into the circuit so as to
maintain equality of resistance. Either an induction coil or else cups
of acidulated water with similar poles may be used in place of the con-
denser before named when the devices are positioned, so that the
discharge from the coil or the cups on the opening of the circuit opposes,
compensates for the effect of, or neutralizes the static discharge of the
line.
Where two helices are used upon one core and the line and artificial
lines pass through those helices as aforesaid there may be a third helix
on the same core between the said two helices, and this third helix will
operate the receiving instrument by the induced current in the said
third helix.
A compound differential and polarized magnet may be made use of in
the quadruplex telegraph. In this instrument there are two armatures,
one to respond to change of polarity and the other to change of electrical
tension or energy from the distant sending station, as aforesaid.
When the duplex or quadruplex receiving instrument is arranged to
act as a repeater to send the message on to another station the polarized
magnet is delicately adjusted so that the magnetized tongue is energized
to respond to delicate changes in the polarity of the cores, and this
polarized tongue opens and closes the circuit for the relay and operates
the same either diretly or through an electro-magnet and armature with
circuit closing or reversing springs to act in the relay circuit. These
circuit connections are arranged so that on long lines the duplex
telegraph may repeat the messages into another duplex telegraph to
another distant station, or the quadruplex telegraph may be made to

page_text: At
operate automatically at an intermediate station as a relay to and from
a distant station on long lines, the principles of operation as aforesaid
being borne in mind, the receiving instruments being made to operate
the relay instruments and circuits instead of acting upon a sounder.
the intermediate or relay station switches will generally be used to
facilitate the adjustment of the line and to throw in or out the relay
connections so as to work from or to either end, or to allow the end
stations to communicate with each other by the relay on long lines.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Alva Edison in the Great Seal Patent
Office on the 31st July 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
ALVA EDISON, of Newark, in the State of New Jersey, United States of
America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Second day of February, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth 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 veud, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, au Invention for
"IM.
PROVEMENTS IN DUPLEX AND MULTIPLEX 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 inonths next and immediately after
the date of the said Letters Patent.

page_text: 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 Drawings hereto
annexed, and to the letters and figures marked thereon (that is to say):-
The objects of this Invention are,—
First. To enable two operators, one at each terminal station, to
transmit simultaneously over one wire, and two others, one at each of
such stations, to receive such messages, and in this respect my Invention
is an improvement in duplex telegraphs.
Second. To enable four operators, two at each terminal station, to
transmit signals, and four other operators, two at each terminal station,
to receive the messages without either interfering necessarily with the
other, and to use only one line wire in so doing. This portion of my
Invention is designated a quadruplex or multiplex telegraph.
Third. To allow either operator to signal the distant station so that
the message may be repeated to rectify any inaccuracies or omissions.
Fourth. To repeat a message received over one wire by either the
duplex or quadruplex telegraph into another circuit, to send the same to
another or distant station.
I remark that the duplex and quadruplex telegraphs can be used by
the number of persons named, or they can be used singly by oue
operator at each end; and furthermore, that by bearing in mind the
general principles of operation herein set forth, the details of the arrange-
ments of the batteries and metallic circuit connections will be apparent
to an electrician.
One of the persons sending a message employs a key that is con-.
structed so that it does not break the circuit, but so that it connects.
more or less, of the battery to the line; thus one operator works a
distant instrument by a rise and fall of the electrical tension or energy ;
the other operator has a key that is made to reverse the circuit connec-
tions without breaking the continuity of circuit and thus his message.is
indicated by a change in the polarity of the current sent, regardless of
the tension or energy of the battery power. These keys of the sending
station, are, either operated directly by hand, or preferably by an electro-
magnet, a local circuit, and a finger key for each, and both ends. of the

page_text: line are similarly provided with two transmitting keys, batteries, and
circuit connections, and also with receiving instruments next specified,
but I remark that the receiving instruments are also capable of use in
duplex telegraphing under systems of transmission heretofore employed,
wherein the rise and fall of tension produce the respective indications at
the two receiving instruments.
The instrumentalities at each end for receiving the messages consist,
first, of a receiving magnet; second, of a polarized receiving magnet;
third, of an artificial line; fourth, of adjustable rheostats or resistances;
and fifth, of local circuits containing batteries and electro-magnets
forming the instruments for receiving the message by sound by a
"Morse receiver," or in any other convenient manner.
The instruments that are required for either the quadruplex or the
duplex system of receiving are selected and arranged with reference to
the transmitting devices employed. With the duplex system operated
by rise and fall of tension as aforesaid, the polarized relay will not be
required, but the receiving magnet is to be placed at a point that is
neutral to the message sent from that station, but where it will be influ-
enced by the message received. To this end the artificial line composed
of a rheostat, preferably with a condenser in a shunt around the rheostat,
is arranged so that its discharge may compensate the static discharge
from the line, and this artificial line is at one side of the receiving
instrument or instruments, and the line connections at the other, and
the pulsations sent from the home station will be balanced in the
receiving instrument at that station, but such receiving instrument will
respond to the pulsations from the distant station because the distant
pulsations are unbalanced.
The receiving magnet is sometimes made with two helices on one core,
and one helix is in the artificial line, and the other in the main line, and
they are so wound as to oppose each other, and hence the core is not
magnetized by the outgoing current, but it is by the current from the
distant station operating in the one helix. The polarized receiving
magnet employed in the quadruplex telegraph is similarly arranged and
positioned so as to be uninfluenced by the current sent, but to respond to
the change of polarity in the current received, and when inade with
four belices around the two cores, the instrument becomes a differential
polarized relay or magnet.

page_text: When the condenser is used in a shunt around the rheostat, either in
the artificial line or between the receiving instrument and main line, its
charge and discharge, as the circuit is opened or closed, neutralizes ör
compensates for the effect of the static charge and discharge that takes
place at that same time because the condenser is arranged so as to
discharge in opposition to the static discharge.
In the receiving instruments aforesaid, when arranged for the quadru
plex telegraph, it is preferable to arrange the local circuit that is worked
by such receiving instrument so that the sounder is operated by the
unbalanced force of a second local battery when the first local circuit is
broken by the armature of such receiving instrument, thereby the
sounder will be more distinct in its response to the pulsations on the
line.
The main battery of the line is subdivided into two portions of unequal
power for the object herein-before named, and one portion is always upon
the line, and the other portion is applied or removed by the key of one of
the operators to increase or lessen the electrical energy; with this battery
it is preferable that a resistance be inserted in a branch passing around
the battery to the key, arranged to present the same résistance to
currents from the distant station that that portion of the battery itself
presents when it is connected into the circuit so as to maintain equality
of resistance. Either an induction coil or else cups of acidulated
water with similar poles may be used in place of the condenser before
named, when the devices are positioned so that the discharge from the
coil or the cups on the opening of the circuit opposes, compensates for
the effect of, or neutralizes the static discharge of the line.
Where two helices are used upon one core, and the line and artificial
line pass through those helices as aforesaid, there may be a third helix
on the same core between the said two helices. and this third helix will
operate the receiving instrument by the induced current in the said
third helix.
A compound differential and polarized magnet may be made use of
in the quadruplex telegraph. In this instrument there are two armatures,
one to respond to change of polarity, and the other to change of electrical
tension or energy from the distant sending station, as aforesaid.
When the duplex or quadruplex receiving instrument is arranged to
act as a repeater to send the message on to another station the polarized

page_text: magnet is delicately adjusted, so that the magnetized tongue is energized
to respond to delicate changes in the polarity of the cores, and this
polarized tongue opens and closes the circuit for the relay, and operates
the same either directly or through an electro-magnet and armature,
with circuit closing or reversing springs to act in the relay circuit.
These circuit connections are arranged so that on long lines the duplex
telegraph may repeat the messages into another duplex telegraph to
another distant station; or the quadruplex telegraph may be made to
opérate automatically at an intermediate station as a relay to and from a
distant station on long lines, the principles of operation as aforesaid
being borne in mind, the receiving instruments being made to operate
the relay instruments and circuits instead of acting upon a sounder. At
the intermediate or relay station switches will generally be used to
facilitate the adjustment of the line, and to throw in or out the relay
connections so as to work from or to either end, or to allow the end
stations to communicate with each other by the relay on long lines.
The essential instrumentalition

page_text: the distant stations, hence two, four, six, or eight persons can operate
over one wire, half of them being engaged in sending and the other half
in receiving.
Having thus defined the general principles of operation, the details
will be easily understood by reference to the Figures of the Drawing
successively.
1
The keys K and R, K, Figure 1, may be operated directly by hand,
but I prefer that the operator use the finger keys a and b, batteries a¹, b,
local circuit wires and electro-magnets c and 'd, with armatures to move
these keys K and R, K, respectively. The main battery B has a
wire 10 from the key K that divides the battery into a larger portion 11
'and a smaller portion 12. When the key K is at rest the battery 12 is
connected to the line'L through the connections 5, 6, 7, 13, 14, and R¹,
and to the earth through the connections 10, K, 2, wire 16, 8, R, K, A,
and 17. When the key K is depressed the entire battery 11 and 12 is
placed on the line by connecting from 3 to earth G through 2, 16, 8,
R, K, 4, and 17. Now if the key R, K, is operated either at the same
time as K or separately the polarity is reversed, whether the electrical
tension is high or low. Suppose the current aforesaid was positive to
line and negative to earth, then if R, K, is depressed 4 will be separated
from R, K, and 7 from '6, and the positive current will go from 5 to
earth & through 4 and 17, while the negative will be connected to the
line L from 3 or K by spring 2, wire 16 by 8, 7, 13, and 14, and R¹ to
line L.
It is to be understood that the instruments at the distant station are
the counterparts of those shown in Fig. 1; and having now described
how the pulsations of different polarity and of rise and fall of electrical
tension are sent it will be apparent that they will at the distant station
operate the magnet M or the polarized magnet D; M, the currents
passing from the line L by 20, M, 21, D, M, R³, 23, R², 15, 13, to earth
through R, K, and its connections; a portion however passes by R¹
and 14, and also a portion by R4 to earth, according to the relative
résistances of the various routes.
It is now necessary to describe why the pulsations sent do not operate
the receiving instruments at the home or sending end of the line.
The instruments M and D, M, are at a neutral point to the pulsations
sent, because the electric current divides half going by¨ 1'4, the other
.

page_text: half by 15, the rheostats R2 and R4 being adjusted to offer the same
resistance as the rheostat R¹ and the line and distant instruments, hence
between 20 and 23 what is known as a 66
bridge" is formed and the
electric forces of the outgoing current opposing each other equally the
instruments M and D, M, are not affected. The rheostat R³ serves to
divert a portion of the current passing between 20 and 23 into the con-
denser C, and upon the principles known to electricians the condenser
reacts or sets up a reverse current when the current is lessened or
augmented, thereby the effect in the instrument of the static charge and
discharge due to the passage of the distant signalling current over such
line are neutralized by the counter-discharges from the condenser.
A secondary battery S, B, Fig. 16, composed of two or more cups
containing acidulated water and poles of the same materials may be
used in the "bridge" to effect the same object of neutralizing static
discharge from the line of the of the incoming current by an opposing or
counter current set up when the electrical condition is changed. The
condenser C arranged around the extremities of the rheostat R4 which
forms the artificial line is for the purpose of generating an inductive
current to balance that due to the static induction of the line. The
rheostat R5 is for the purpose of regulating (by increasing and decreasing
the resistance) the length and strength of the inductive current from C²
to enable perfect compensation to be obtained on various wires and
especially upon long circuits.
The functions performed by the condenser C³ will be equally as well
performed by inserting an electro-magnet C¹ in the circuit 15, as shown
in Fig. 16. The rheostat R6, Fig. 1, is adjusted to afford the same
resistance as the battery B, hence when the operators at one station are
balancing the outgoing currents upon the receiving apparatus M. and
D, M, at that station by the adjustment of R4 and R the switch 13 at
the distant station which is in connection with the line is to be turned to
the right so as to disconnect the battery B from the line and allow the
earth connection to pass through R6; thus the battery at the distant
station will not interfere with the proper balancing of the outgoing
current.
The receiving instruments M and D, M, may be observed by the
receiving operators and the message read either by sound or in any other
known way, but usually it will be best to use these as the relays to the
receiving instrument proper, and they are so shown. The magnet M

page_text: operates by its armature lever, the local circuit from the battery ƒ, in
which is placed the electro-magnet g, and this in turn operates a second
local circuit from the battery f¹, in which is the receiving instrument g³,
which will usually be a sounder; the circuit off will close when M
ceases to attract its armature, and the circuit of f" will close when gis
demagnetized, hence the receiving instruments g₁ and M will pulsate
exactly in harmony, and as the armature of g is not so delicately
adjusted as the armature of M there will not be any false pulsation
reach gas sometimes occurs in M, when the polarity of the current is
reversed.
The same effects will be produced by the circuits shown in Figs. 2, 3,
and 4. In Fig. 2 the battery f will be short circuited through the
armature of the magnet M when the current does not act in M, and
hence the battery will not act in g, but when the armature of M is
attracted the circuit is broken and the battery / has no other route, but¹
is obliged to act in g, hence the armatures of 7 and M respond simul-
taneously.
- If the batteries f and be both connected to the receiving magnet
g, as shown in Fig. 3, and in reverse, so that they balance each other
when the circuits of the two batteries are closed the electro-magnet g
will not be energized, but this electro-magnet g will respond to 'the
battery f simultaneously with the magnet M, because when the arma-
ture of M is attracted the circuit of the battery / is opened, and said
battery f. ceases to neutralize the effect of the battery fl. The same
effect will be produced by connecting the battery f to the wire between
the helices of the magnet g, as seen in Fig. 4, and winding those helices'
so that the battery current 'dividing and acting in both helices will
produce similar polarity of the cores, hence the magnetism will be
neutralized, while both circuits from the battery fare closed, but when"
one circuit is broken by the movement of the armature of M the battery
current acts in only one helix and attracts the armature at the same time
as the armature of M moves. The polarized tongue of the electro-
magnet D, M, is shown in Fig. 1 as acting as a relay to the local circuit.
containing the battery h and receiving magnet or sounder k, and in..
Fig. 5 this electro-magnet k acts a relay to the second local circuit
and battery 1, in which is placed the receiving magnet or sounder n.
·
In Fig. 6 the differential, polarized magnet D, M, instead of being.
in the same bridge 20, 23, with the receiving magnet M as before is.

page_text: made as a compound differential polarized mágnet, in which there are
four helices so wound that the outgoing current from 14 will operate in
the helices 61, 62, while that from 15 will act in the helices 63, 64; and
these helices being wound in opposite directions the cores passing
through 61, 63, and 62, 64, respectively, will not be magnetized, the
magnetizing actions being opposed to each other, hence the polarized
tongue between the corês will not be moved one way or the other, but
the incoming current from the distant station will pass from L through
62, 61, to 14, thence through the bridge wire containing M, and also
through R¹ and R² to earth through the transmitting keys; owing to
the great resistance of R* (which should be equal to the line) a very
small portion of the distant currents passes to earth by this route. The
distant current in passing through the helices 62 & 61 gives th>
respective cores a polarity to attract the tongue i one way or the other
so that the tongue responds to the change of polarity resulting from
operating the key R, K, (Fig. 1) at the distant station.
In Fig. 7 the same arrangements of transmitting keys, as in Fig. 1,
are shown, and the compound polarized magnet D, M, described in con-
nection with Fig. 6, is introduced near the dividing points of the wires 14
and 15, and the electro-magnet M is made compound, having two helices
wound in opposite directions, so that the outgoing currents neutralize
each other in their tendency to magnetize the soft iron core, passing.
through both helices; thereby magnetism is not produced by the out-
going current, but the current coming from the distant station, passing
in one direction through the helix 26 and back in the other direction
through the core 27 produces magnetism in the core, so that the
armature of M responds to the rise and fall of electrical tension of the
current sent by the key K at the distant station, and the polarized
tongue i of the differential magnet I), M, responds, as aforesaid, to the
reversal of the circuit connections by the key R, K, at the distant
station.
"
The rheostats and condensers in Figs. 6, 7, 8, and '9, are introduced
for the same purpose, and are adjusted to act in the same manner as the
same instruments shown and described in connection with Fig. 1,
marked with the same letters of reference.
and
A modification in the construction of the magnet is shown in Fig. 9,
in which the coils ör helices 61, 62, 63, and 64, connected with the
wires 14 and 15 act, as described in connection with Figs. 6 and 7, to

page_text: move the magnetized tongue i by the change of polarity; but there is
an armature M added, the spring of which is adjusted so that the
armature responds to rise and fall of electrical tension, thus dispensing
with the magnet M and making the one compound magnet, shown in
this Fig. 9, respond to the change of polarity or electrical tension, or
both, at the distant station; but this compound magnet is uninfluenced
by the currents sent out at that station because they are balanced iu
their actions therein, as before described. Electro-magnets 0, 0¹, placed
in branch or shunt circuits around the receiving magnet, set up counter
secondary currents to neutralize the secondary or induction discharge of
the electro-maguet D, M.
In Fig. 8 a modification of the circuit wires is shown. The magnet M
and differential magnet D, M, are the same as in Fig. 7, but there are
two artificial lines with rheostats R4, R³, and condensers C², and these
are separately connected to the respective magnets and to earth, so that
the outgoing currents can be balanced in their action in D), M, by one
artificial line to G and balanced in the electro-magnet M by the other
artificial line to G¹ independent of each other.
In Fig. 10 connections are shown that correspond to those shown in
Figs. 1 and 5, so far as the receiving portion of the apparatus; the
transmitting keys K and R, K, are somewhat differently arranged. The
battery is compound, part being opposed to the other part. The
key R, K, in a position of rest is open, and the key K is closed, hence
the portions 30 and 32 of the battery are short circuited through K and
do not go upon the line, and the batteries 31 and 33 still act in the line,
but 31. overpowers and more than neutralizes 33, so that the pre-
ponderating force from 31 on the line is negative, the earth being
connected to positive; now, if the key R, K, be closed the portions 30
and 31 of the battery are short circuited, allowing the portion 33 to act
and reverse the polarity of the current, as the positive pole of 33 is to
the line. If the key K is depressed the short circuits of 30 and 32 are
broken, and these portions 30 and 32 of the battery act in the line, but
30 contains a large excess in the number of cells and acts with 31 to
neutralize 32 and 33 and produce a rise of electrical tension on the line;
hence by this arrangement the rise and fall of tension and the reversal
of the polarity of the currents are attained without the peculiar keys
shown in Figs. 1 and 7. D, M, Fig. 11, is a polarized relay having the

page_text: line wire L attached to the cross wire connecting the two spools together.
The other ends are connected, one to a resistance coil R6 and the other
to an ordinary electro-magnet o. The resistance of o is equal to R6.
Now when the current is made to circulate permanently through
the two coils of the polarized relay D, M, and through
aud R6,
its effect is balanced in the polarized relay M, as it passes in
opposite directions through its two coils, but the magnet o is
charged. Now, if the current be interrupted or suddenly decreased in
strength the iron cores of o set up an induced current in the helices
surrounding it, and this current circulating within the circuit formed
of O), R and the coils of the polarized relay D, M, passes in the proper
direction through D, M, to make its cores magnetic, and the tongue is
thrown to one side. If now the circuit be closed or the strength of the
current increased the magnet o will in the act of charging set up another
induction current, which now circulates in the opposite direction, and
throws the tongue of the polarized relay in the opposite direction. The
tongue is to be adjusted so that the weak current from battery 12 at the
distant station will not produce sufficient induced current by its passage
through o to affect the tongue of D, M, but only when the battery 11 is
put to line; hence the polarized relay will respond only to currents
transmitted from a strong battery 11. M is a double coil relay, which
works by the weak current from 12. The main current passes through
the coil 27 in one direction, and if the transmitter K is quiet works the
lever, and the message is received. I use a repeating sounder y to
repeat the signals to the receiving sounder g¹ for the reason that in
signalling with battery 11 the armature lever of M receives a forward jerk,
and would give a false signal were it not for the repeating sounder g,
which owing to sluggishness, and having to be fully charged, &c., does
not repeat the false signal on g.
I will now describe the method by which I prevent the battery 11 from
affecting M. Suppose the battery 12 is disconnected, and the battery 11 is
put to line by the key K, the polarized relay responds and the lever of M
would also, were it not for the fact that owing to the rapidity with which
the polarized tongue i moves, a second circuit is closed which contains a
resistance coil R7 and a battery hadjusted in such a manner that a
current passes through the second coil 26 of M equal to that passing
through 27 from the battery 11; hence the effect of the strong current
from the battery 11 is balanced in M. Within this equating circuit is

page_text: placed a relay, which operates a receiving magnet n, from which the
signals of the polarized relay 1), M, are copied.
It is obvious that the current from the battery 11 will pass through
the coil 27 on magnet M before the equating circuit can be closed, and
the effect is to give the lever of the relay armature a quick forward
movement, but the effect of this is neutralized by employing the repeating
sounder before described.
In Fig. 13 the polarized relay is dispensed with, and two separate
relays used, both of which respond to the heavy battery, while C responds
only to the weak battery. M and D are both adjusted with high tension
of armature spring. One message received upon M is indicated by the
sounder g, while the other message is received upon M¹ and sounder n¹.
The magnet D is used to close the balancing circuit to balance the effect
of the large battery within the coils of M. The magnet M' might be
taken out of the main line, and inserted in the balanced circuit h, R7,
and produce the same effect.
Another modification is shown in Fig. 12. D is adjusted to respond
to the strong currents when the armature lever is away from the magnet.
The main circuit is completed which first passes through the coil of D,
then to the earth through a resistance of several hundred ohms in R4.
Another route to the earth is through shunt wire u to armature lever
of 1), thence through point c to the coil M on the relay. In this
position the relay responds to the weak currents from the distant station.
The tension on the retractile spring of the armature of D being great,
and the cores some distance from its armature does not so respond, but
when the strong battery is put to line the lever of D is attracted, and
the strong current instead of passing through the coil M now passes
through the resistance R² and coil k; the effect of its passage through
the coil R² is to weaken the total current nearly as much as it was
increased by addition of battery power, so that the electro-magnet M
does not respond to strong currents.
Fig. 14 shows a plan, and Fig. 15 is a perspective view of devices
for magnetizing the tongue of the differential magnets D, M, and
adjusting the polarity of this tongue . This tongue is connected at
one end to the iron standards, and contiguous to this standards is a
magnet t ; said magnet may be a permanent bar magnet, as in Fig. 15,.
or an electro-magnet polarized by a local battery u³, and the magnetism

page_text: i
passes from
by induction throughs to the tongue i, and hence the
tougue can be more or less strongly magnetized by adjusting the
magnet t nearer to or farther from the standard s, or by adjusting the
rheostat R.
Fig. 17 shows connections similar to those shown in Fig. 1, with the
exception of the magnet M and the electro-magnet M, X, R, for
balancing the effect of the static charge and discharge. The magnet M
is provided with an extra magnet X acting on the opposite side of the
armature lever, but with a tendency to move the lever in the same
direction as M. This magnet X is placed in the condenser circuit and
receives momentary magnetism at the moment when the current from
the distant station is increased, decreased, or changed in the direction of
the flow. The object of this extra magnet is to produce a more powerful
compensation for the effect of the static charges and discharges upon
the waves, as they pass over the wire from the distant station and
through M.
When the line is very long and of high resistance and great electro-
static capacity, the first portion of a dash from the distant station will
be very weak owing to the static current of the line. The effect of the
condenser acting both within the triangular circuit as well as through
the magnet X is to supply as it were the current lost of the static
phenomenon of the line. M, X, and M'. X', are two electro-magnets of
equal size, resistance, and power arranged in 14 and 15 in place of R¹
aud R2, as in Fig. 1. Opposite M', X', is placed another magnet R, X,
which may, by the adjusting device p, be made to approach or recede
from M, X¹. This magnet R, X, is placed in a second artificial
circuit. When the battery at that station is augmented or reversed the
magnet R, X, becomes powerfully charged, and this magnetism acting
upon the cores of M', X¹, sets up a strong momentary induction current
within the triangular circuit in a direction, as regards the receiving
instruments M, and D, M, contrary to that of the static current from the
line, hence a balance is obtained and the instruments remain unaffected
by the outgoing current. M, X, is used for the purpose of preventing
the two angular wires from being unequal, and thus setting up inductive
currents on the passage of the distant current.
It is obvious that if the line be very long and of great electro-static
capacity, that the resistance of R³ may be made so small, that a very

page_text: powerful current will pass through R, X. The exact balance can also be
obtained by moving the magnet R, X, to or from M', X¹.
In Fig. 18 the same parts are shown as in Figs 1 and 10, except that
the tongue
i works to close a circuit from the battery to either of the
electro-magnets k or n, and these move the reversing key R, K, similar
to that shown in Figs. 1 and 7. The battery B is connected with this
reversing key similarly to that before described, hence a change of.
polarity in D, M, moves the key R, K, first one way and then the other,
and thus the message is relayed or repeated into a new circuit, the object
of this being to use the duplex or quadruplex systems before described
on as long lines as convenient, and then to make the magnets D, M,
and M, repeat the messages automatically into new circuits extending
still further.
The entire apparatus and connections for repeating as aforesaid are
shown in the diagram, Fig. 19, which although it appears complicated is
very simple, one line L for instance comes from New York to one set of
instruments at an intermediate station, say, Buffalo, and the other line
L, L, extends to the distant instruments, say at Chicago, in the other
direction.
The keys and instruments are duplicated and exactly the same as
shown in Figs. 1 and 5, only there are two distinct set of instruments.
Suppose that a message over the wire L acts by rise and fall of
tension in the relay magnet M, and that the message is repeated into
the sounder or receiving instrument g¹, as before described, if the
switch 40 in the local circuit of the battery f' is closed the message
goes no further, but if the switch 40 is open the circuit of the battery f¹
extends to the electro-magnet c, the switch of the key a being closed;
thereby the message received at M. on one line is repeated by c and K
into the next line. So in like manner the message received from New
York in the differential magnet D, M, and repeated in the sounder n will
go no farther if the switch 42 is closed, but if the switch 42 is open the
message will be repeated to Chicago at the key 6 by the magnet d
and key R, K; that reverses the circuit in the same manner as if the
finger key. 6 were operated. Of course by closing the switch 41 the
message coming over the line L, L, from Chicago and received in M
will be repeated to new York, and the same thing will occur in
relation to the message received in D, M, from Chicago if the

page_text: switch 43 is closed. Thus, one or more messages may be automatically
repeated in long lines without interfering with the working of the other
portions of the quadruplex instruments in either direction from the inter-
mediate station.
i
In Fig. 20 the polarized magnet D, M, and circuit wires are the same
as have before been described, but the magnet M that responds to rise
and fall of electrical tension is slightly varied. The armature 84 is
polarized, and swings between the cores of the electro-magnet M, and at
the outer end the tongue is between the springs 82 and 83, and these
springs are strong enough to hold the tongue stationary, except when
the electro-magnet M is highly energized by increase of current from
the sending station; when at rest the current from the battery 85 passes
by the springs 82, 83, and block 86 back to the battery, but when the
current is increased enough to draw the armature 84 towards the
spring 82 that is moved away from 86 the short circuit through 86 is
broken, and the current directed through the receiving magnet g, and it
returns through spring 83 to the battery, and if the polarity of the
current is changed and the strength of current remains the armature 84
flies over against 83, and moves it so suddenly that the magnet g will
not have time to demagnetize by the momentary contact of both the
short circuit springs with the block 86.
is,
What I claim as my Invention and desire to secure by Letters Patent
-
First. The combination in telegraph circuits of keys that produce a
rise or fall of the electrical tension, keys that change the polarity of the
current connected with the line, receiving magnets operated by rise and
fall of electrical tension, and polarized magnets that operate by change
of polarity of the electrical current, substantially as set forth.
Second. The combination with electro-magnets operated by rise and
fall of electrical tension of relay circuits, batteries, and electro-magnetic
receiving instruments or sounders, substantially as set forth.
Third. The combination with a polarized relay magnet operated in the
telegraphic circuit by change of polarity of the current of relay circuits,
batteries, and receiving electro-magnet or sounder, substantially as set
forth.
Fourth. In a telegraph arranged to operate by rise and fall of tension
and change of polarity of the electrical currents the use of condensers,

page_text: rheostats, or induction coils to neutralize the static charges and dis-
charges, substantially as set forth.
Fifth. In a quadruplex repeater the combination of the two receiving
instruments in one circuit with the two magnets and transmitting device
in the other circuit, connected so that signals made in one circuit will
be repeated to the receiving instruments in the other circuit, and vice
versa.
Sixth. In a quadruplex telegraph a main line circuit divided and
provided with local batteries and circuits that operate the repeating
instruments, substantially as set forth.
Seventh. The combination in a quadruplex repeating telegraph of
switches or circuit connections for dividing the local circuits to allow
each quadruplex line to work independently, substantially as set forth.
In witness whereof, I, the said Thomas Alva Edison, have here-.
unto set my hand and seal, this Sixth day of July, A.D. 1875.
THOMAS ALVA EDISON. (L.S.)
Witnesses.
CHAS. H. SMITH, 121, Nassau St., New York.
HAROLD SERRELL,
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