IMPROVEMENT IN MULTIPLEX TELEGRAPHS
Year: 1877

page_text: LETTERS PATENT to Edward Griffith Brewer, of Chancery Lane, London, for
the Invention of IMPROVEMENT IN MULTIPLEX TELEGRAPHS." A com-
munication from abroad by George Bartlett Prescott, of the City and State of
New York, United States of America.
Sealed the 9th March 1877, and dated the 15th January 1877.
PROVISIONAL SPECIFICATION left by the said Edward Griffith Brewer at the
Office of the Commissioners of Patents on the 15th January 1877.
EDWARD GRIFFITH BREWER, of Chancery Lane, London. "IMPROVEMENT IN
MULTIPLEX TELEGRAPHS." (A communication from abroad by George Bartlett
Prescott, of the City and State of New York, United States of America.)
This Invention relates to that class of telegraphs in which two messages can be sent
over one wire simultaneously from one station to a distant station, or one from cach
end station, or two messages can be sent from each end station to the other simulta-
neously, such telegraphs being known as duplex, quadruplex, or multiplex telegraphs.
These telegraphs have been arranged so that one outgoing signal is made by the
rise and fall of electric tension, the other by reversal of the polarity.
The pulsations sent do not operate the receiving instruments at the sending
station, but they are operative in the receiving instruments at the distant station.
In telegraphs of this character that are operated over long lines, there is some-
times a false signal or pulsation in the receiving instrument that operates by rise
and fall of tension if the polarity of the current is changed during that signal or
pulsation.
The object of the present Invention is to ensure more perfect signals in the
receiving instruments and to lessen the risk of any false signals.
At the transmitting end are two keys or equivalent transmitters, and the only
conditions that can exist are,-
1st. Keys 1 and 2, both open.
2nd. Key 1 closed, key 2 open.
3rd. Key 2 closed, key 1 open.
4th. Keys 1 and 2, both closed.
The electric connections are made through a circuit preserving lever moved by an

page_text: electro-magnet in a local circuit of the key No. 1, and an oscillating reverser operated
by a magnet in a local circuit of the key No. 2.
When keys 1 and 2 are both open the line is connected to the ground, but neither
sections of the battery are to the line.
When key 1 is closed and 2 open, the circuit is closed upon ground through lever
of key 1, smaller battery through the double helices of the receiving relays to the
line and to the artificial lines, and the current is balanced in the said relays, but
operates with a positive or + current to the distant station.
When key 2 is closed and key 1 is open, the rocking reverser is moved, and the
smaller battery is connected to the line, but reversed, so that the negative or pole
is to line.
-
When keys 1 and 2 are both closed the larger main battery is connected to the
line and the circuit of the smaller battery broken.
The receiving instruments are made of differential relay electro-magnets with
double helices, the wires branching off to opposite helices, and the polarized
armatures are placed between the poles. The outgoing currents are neutral, the
incoming currents from the distant station act in one electro-magnet by reversal of
polarity, and in the other by rise and fall of tension, and the respective armatures
open and close local circuits in which are sounders or other receiving instruments.
In some instances I arrange the two batteries, so that when both keys are open
the circuit to the earth is completed through the smaller battery, the closing of
key 1 takes this battery off the line, the closing of key 2 connects the larger battery
to the line and reverses the polarity, and when both keys are closed the larger
battery is disconnected and the smaller connected with its polarity reversed. In
these connections the relay magnets are arranged so that the polarized armatures
break the local circuits when the positive of the small battery is connected to the
line, and one relay closes to the sounder when there is no current; hence responding
to key 1 the other polarized electro-magnet responds when key 2 connects the
negative of the larger battery to the line, and when both keys are closed both relays
respond, the one by the negative of the smaller battery, and the other in con-
sequence of the current not being sufficient to overcome the spring that closes the
local circuit.
The circuit connections may be reversed, so that the relay magnets and sounders
respond to negative currents under circumstances where positive are named in the
foregoing and the reverse.
In some instances there is one battery and an intermediate branch connection to
separate a section thereof, so that when key 2 is closed and key 1 open, the section
only will be on the line; when both keys are open the entire battery will be upon
the line as or positive, and when key 1 is closed and key 2 open the entire
battery will be upon the line as or negative, and when both are closed the
or negative.
-
-
section only will be on the line, as
At the receiving portion of the instrument the polarized relay is sometimes placed
in the bridge, and the differential relay at the junction of the bridge, earth, and line
wires; a condenser and magnet in a local circuit, connecting at each side of a
rheostat in the bridge, serve to counteract any false movement of the armature of
the differential relay that sometimes arises in the charging and discharging of the
line and artifical line, and also to intensify the action of the incoming current on
the armature of the diffential magnet.
In all instances rheostats or resistances are employed for the artificial line, and to
adjust the currents, and condensers are used to neutralize the static charge and
discharge.
These improvements allow the multiplex telegraph to be operated over longer

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Edward Griffith Brewer in the Great Seal Patent Office on the 13th July
1877.
EDWARD GRIFFITH BREWER, of Chancery Lane, London. "IMPROVEMENTS IN
MULTIPLEX TELEGRAPHS." A communication from abroad by George Bartlett
Prescott, of the City and State of New York, United States of America.
This Invention relates to that class of telegraphs in which two messages can be
sent over one wire simultaneously from one station to a distant station, or one
from each end station, or two messages can be sent from each end station to the
other simultaneously, such telegraphs being known as duplex, quadruplex, or
multiplex telegraphs.
These telegraphs have been arranged so that one outgoing signal is made by the
rise and fall of the electric tension, the other by reversal of the polarity.
The pulsations sent do not operate the receiving instruments at the sending
station, but they are operative in the receiving instruments at the distant station.
In telegraphs of this character that are operated over long lines, there is some-
times a false signal or pulsation in the receiving instrument that operates by rise
and fall of tension, if the polarity of the current is changed during that signal or
pulsation.
The object of the present Invention is to ensure more perfect signals in the
receiving instruments, and to lessen the risk of any false signals.
The first part of this Invention consists in an improved arrangement of the
transmiting apparatus in reference to the batteries, whereby the required com-
binations of currents are transmitted without at any time interrupting the main
circuit. It further consists in the employment of two separate and independent
polarized arinatures, each of which operates its own receiving instrument by means
of an independent local circuit, and in the arrangement of a receiving instrument in
combination with a relay armature, whose movements are capable of being con-
trolled by changes of polarity in the line current, and a supplementary contact
lever, by means of which the difficulties which have heretofore been encountered in
working apparatus of this kind upon long circuits are entirely overcome.
In the accompanying Drawing Fig. 1 is a general plan of the Invention, showing
both the transmitting and receiving instruments with their various connections.
Fig. 2 is a diagram intended to illustrate the manner in which electric currents
are modified by transmission through long lines; while Figs. 3, 4, and 5 represent
certain inodifications in the details of the apparatus.
In order that two communiations may be simultaneously transmitted in the
same direction over the same conductor, it is necessary to make use of two
independent transmitting instruments or devices at the sending station, and also of
two independent receiving instruments at the receiving station.
For the purposes
of this description it will be assumed that the method of telegraphic transmission
known as the "Morse system" is used, although any other electro-magnetic system
may be substituted therefor.
The transmitting devices are preferably operated by connecting them either
mechanically or electrically with the levers of common Morse keys.
The operation of two independent transmitters or keys, when arranged in this
manner, gives rise to four distinct electrical conditions of the line, as follows:-
First. First and second keys both open.
,Second. First key closed and second key open.
Third. Second key closed and first key open.
Fourth. First and second keys both closed.
The manner in which these four different electrical conditions of the line are
brought about by the operation of two transmitters will now be explained.
In Fig. 1 t is a lever capable of a slight vertical movement upon its axis in one-

page_text: ;
direction by the attraction of the electro-magnet T, and in the other direction by
the retractile spring 8. The lever with its appendages constitutes the first or
single point transmitter, and is operated by means of a key K³ and a local battery t
in a manner well understood. One end of a flat metallic contact spring b is fixed to
an insulating support, which is mounted upon the extremity of the lever t¹, while
its free end by its own elasticity presses against the projection c, formed upon
the extremity of the lever t¹, and is therefore in electrical contact therewith
when however the key K¹ is depressed, the attraction of the electro-magnet T₁ for
its armature elevates the opposite end of the lever t¹, which carries with it the
The further move-
contact spring b, and presses the latter against the fixed stop a.
ment of the lever t¹ in the same direction causes the spring b to yield, and the
projection c is separated from it. Thus the effect of closing the key K¹ is to first
form an electrical contact between the spring b and stop c, and then to break
almost at the same instant the previously existing contact between the spring b
and lever t¹. As the electric circuit passing through the spring b is by this
arrangement never interrupted, being at all times continuous either through a or c,
or both, it may be termed a continuity-preserving transmitter. The second or
double-point transmitter is preferably constructed substantially in the form shown
in Fig. 1, and consists of a quadrangular plate E composed of some suitable insulating
material, which is mounted upon an axis passing through its center in such a manner
as to be capable of receiving an oscillating motion from the arm e, which is rigidly
attached to its axis. By means of a spring e¹ the arm e is caused to press upon a
roller fixed upon one end of the lever d, which pressure forces the other end of this
lever against the stop d². The lever d carries the armature of the electro-magnet T,
which, like the single-point transmitter, is connected with and operated by a local
battery and key K². The oscillating plate E is provided with four metallie contact
pieces f, g,f,g', fixed upon its four angles, as shown in the Figure. Two contact
levers F and G are situated one at each end of the plate E; these are mounted upon
axes, and tend to press against the respective ends of the oscillating plate E by the
action of springs 81, 82. In the normal position of the transmitter, as shown in the
Figure, the contact lever F rests against the contact piece f, and the contact lever G
against the contact piece f³, and the parts are retained in this position by the action
of the spring el. If now the electro-magnet T2 becomes active in consequence of the
closing of the key K2, its armature is attracted, the tension of the spring e¹ is over-
come, and the arm e is raised, causing the plate E to turn upon its axis so as to
cause the contact piece g to press against the lever f, and g¹ against G.
It will be observed that during the movement of the plate E upon its axis the
lever F must necessarily be constantly in contact either with for with g, and the
lever G with f¹ or gl, and thus precisely the same action takes place in this arrange-
ment as in the single point transmitter first described, except that it is duplicated,
there being two sets of contact points instead of one.
The effect produced upon the electrical condition of the line by the different posi-
tion of the keys at the transmitting station will next be described.
1st. When the First and Second Keys are Both Open.-This is the position of
the apparatus represented in Fig. 1. Disregarding for the present the receiving
instruments and their connection with the line, the circuit may be traced as
follows: From the earth plate G through wires 9 and 8, contact spring b, lever t¹,
wire 7, contact piece f¹, contact lever G, wires 6 and 5, through the receiving instru-
ment to the line wire L. The line wire is connected to the earth without passing
through either battery. In this position of the keys there is no current upon
the line.
2nd. When the First Key is Closed and the Second Key Open.-The route is the
same as before from the earth at G to the contact spring b; from this point it now
diverges through the contact point a and wires 10 and 11 to f, thence through
contact lever F, wires 12 and 13, and battery B to wire 7, and thence to the line L,
as before. In this position the battery B is placed in circuit with its positive or +
pole to the line.

page_text: 3rd. When the Second Key is Closed and the First Key Open.-The route of the
circuit is as follows:-From the earth at G through wires 9 and 8, contact spring b,
and lever t', as in the first instance, thence through battery B and wires 13 and 12
to g¹, thence through contact lever G and wire 6 to 5, and through the receiving
instrument to the line L. In this case the same battery B is placed in circuit with
its negative or pole to the line.
-
4th. When Both the First and Second Keys are Closed.-The route of the circuit
is as follows: From the earth at G by wires 9 and 8 to contact spring b, thence by
contact point a and wire 14 to battery 3 B, thence by wire 15 through g to contact
lever F, wire 12, and g¹ to contact lever G, and, finally, through wires 6 and 5 to
the line L. In this case the battery 3 B, which should be much more powerful than
battery B (consisting of, say, three times as many cells), is placed in circuit with its
positive or pole to the line.
The receiving apparatus consists of two sounders or other suitable receiving instru-
ments S and S, which are controlled by two relays R' & R2 (see Fig. 1).
It is obviously necessary that the sounder S¹ should respond to the movements of
the key K¹, and the sounder S to the movements of the key K2, while both sounders
should in like manner respond when both keys are depressed. The manner in which
this is accomplished will now be explained.
The line wire L on entering the receiving station passes through the helices of the
respective relays R2 and R¹, and thence to the earth. The relay R₁ is preferably
constructed with two electro-magnets m, m³, arranged with their poles facing each
other, and provided with a polarized, that is to say, a permanently magnetized arma-
ture n mounted between the opposite poles of the electro-magnets, as shown in the
Figure.
The circuit of the line L entering the relay R2 passes through the wire 2 and helix
or coil ³ of electro-magnet m, and thence through the helix ³ of electro-magnet m²,
and these helices are arranged in a manner well understood, so that a negative
current (for example) passing through both helices will cause the polarized
armature n to be attracted by the magnet m¹ and repelled by m, while with a
positive current precisely the opposite effect will take place. It is remarked that
there are many different methods of constructing relays with polarized armatures
by which this effect may be produced, and although it is preferred to make use of
the arrangement herein described, yet others may be made use of.
The armature of the relay R¹ is provided with a retractile spring r¹, and operates
the sounder S by means of a local battery l¹ in the ordinary manner. The relay R²
like the relay R¹, consists of two electro-magnets p and p¹ placed opposite each
other, and provided in like manner with a polarized armature o having a retractile
spring 2. These armatures may be composed of hardened steel and permanently
magnetized, which is the arrangement shown in the Drawing, or they may be of
steel or soft iron, polarized either by contact with a permanent magnet or by a helix
through which the current of a constant local battery is made to circulate. The
relay R² differs materially, however, from relay R' in the arrangement of its local
circuit connections, by means of which the sounder S3 is operated.
The polarized armature O instead of being held against a fixed stop by the tension
of the spring rests against the free end of a movable contact lever r, the opposite
end of which moves upon a pivot. The contact lever r is in turn held against the
fixed stop 7 by the tension of a spring g', which tension should be considerably
greater than that of the spring 2 This the normal position when no current is
traversing the helices of the relay. The local battery w is placed in the wire 22
leading from the contact lever r to the sounder S. The sounder S2 is preferably
constructed with differential helices, so that an equal portion of the current of the
local battery w flows through each of the two coils (when the circuits of wires 22
and 24 are both closed) but in opposite directions, and thus the sounder will only
act when one of the two latter circuits is interrupted. The local circuit of the
relay R² may also Le arranged in the manner shown in Fig. 4.

page_text: The manner in which the receiving instruments operate in each of the four con-
ditions of the line herein-before mentioned is as follows:-
1st. No Current.-The local circuit of the sounder S₁ is kept open by the action
of the spring on the armature n, and it remains inactive. The opposing branch
circuits 23 and 24 of the sounder S are both closed by the relay R2, as shown in
the Figure, which renders this sounder also inactive.
2nd. Positive Current from Battery B.-The relay R' which is operated by
positive currents of any strength closes the local circuit of sounder S¹. The relay R²
attracts its armature in such a manner as to cause it to press more strongly against
the contact lever r, but this pressure is not sufficient to overcome the considerable
tension of spring q', and sounder S2 is therefore not affected.
3rd. Negative Current from Battery B.-The armature of relay R¹ is attracted in
the same direction as the tension of its spring 1, and therefore sounder S' is not
affected. The polarized armature of relay R² overcomes the tension of its spring 72,
breaking the local circuit of wire 24 between the armature O and contact lever ?"
and permitting the opposing local circuit in wires 22 and 23 to operate the
sounder S².
4th. Positive Current from Battery 3 B.-The armature of R¹ operates as in the
2nd condition. The more powerful positive current of 3 B overcomes the tension of
spring q¹ in relay R2, and breaks the local circuit of wire 23, permitting the current
in wires 22 and 24 to operate the sounder S². Thus the positive current of 3 B
operates both sounders.
In the herein-before described arrangement it will be observed that in case the
key K2 at the sending station is depressed a negative current will be transmitted
and the sounder S2 will be actuated. Now, if the key K¹ at the sending station be
also depressed the line current is instantly changed from negative to positive in
order to operate the sounder S¹, as before explained, but it is also necessary that the
reversal of the current (which passes through the relay R2) should not cause a break
in the signal which is being given at the same moment upon the sounder S2. The
occurrence of this break is a difficulty which has always been experienced in the use
of previous Inventions for simultaneous double transmission in the same direction,
and it increases in proportion to the length of line which separates the transmitting
from the receiving apparatus. This is owing to the fact that when a reversal of
the polarity of the line current takes place at the sending station the negative
current succeeds the positive, or vice versa, without an appreciable interval between
them.
In traversing a long conductor the successive waves of alternately opposite polarity
tend to neutralize and destroy each other, and when they arrive at the distant
station the interval between them is increased by the shortening of the waves them-
selves. This is shown by the action of the current upon chemically prepared paper
in the following experiment:-It is well known that when an iron pen is used the
decomposition necessary to form marks upon the paper can only be produced by the
positive current. Therefore, if two of these pens be arranged at the receiving station,
resting upon a moving strip of prepared paper, and one pen be connected to the line
and the other to the earth, as shewn in Fig. 2, that when a positive current is sent
over the line, the pen connected with the line will mark, while with a negative
current the pen connected with the earth will mark. Now, if the positive and
negative currents succeed each other without appreciable interval and are of uniform
strength the paper will be marked with two sets of lines, as shown in Fig. 2, the
commencement of one line coinciding exactly with the termination of the preceeding
one. This is the case on a circuit of moderate length, say, of fifty to one hundred
miles. If this distance is increased to, say, three hundred miles, the lines upon the
paper are modified, as shown in Fig. 2 A. Each line begins and ends in a blunt
point, indicating that each clectric wave does not instantly attain its full strength,
but that a portion of the electricity of each wave combines with and neutralizes a
portion of the adjacent wave of opposite polarity. This effect is still more apparent

page_text: at a distance of, say, five hundred miles, the points of the marks becoming more and
more acute in proportion as the circuit is lengthened. The breadth of the mark
indicates the strength of the current. When this falls below a certain minimum it
becomes insufficient to operate an electro-magnet; thus at a distance of five hundred
miles there exists an appreciable interval after the positive wave, for example, has
become too weak to actuate an electro-magnet before the succeeding negative wave
becomes strong enough to influence it. The effect of this is to increase the length
of the period during which the action of the current upon the electro-magnet
becomes null at each reversal of the polarity.
By the arrangement of the contact lever V, in connection with the armature lever
o of relay R2, and the local circuits, as herein-before described, and shown in Fig. 1,
the reversal of the polarity of the line current in the relay R² takes place without
interrupting the signal upon the sounder S, for the reason that when the armature
o moves, it passes directly over from one extreme position to the other without
stopping at the intermediate position long enough to affect the sounder S³, not-
withstanding that there may be a considerable interval between the successive
currents.
In order to adapt the apparatus afore mentioned to the simultaneous transmission
of four communications upon the same wire, two in each direction, it is only
necessary to use it in connection with some suitable method of duplex telegraphy.
It is preferred to make use for this purpose of the method illustrated in Fig. 1 of
the
accompanying Drawings. To this end an additional helix or coil is placed
upon both the electro-magnets of each of the relays R1 and R2, as shown at h¹, h²,
and h2, 2, which contain the same length of wire, and the same number of con-
volutions, as the helices h, h, and h³, h³, but exert an opposing or neutralizing effect
upon the cores of the electro-magnets. The helices h¹, h, and h2, h3, are included in
the circuit of an artificial or branch line diverging at the point 5, and leading by
way of 16, 17, 18, 19, 20, and 21 to the earth at G. This circuit is made to pass
through a resistance x, which is capable of adjustment, so that the strength of the
current in the artificial line may be made equal to that in the main line. When
this has been done, the outgoing currents are divided between the main and artificial
line, and do not affect the action of the relays R¹ and R². A condenser C is made
use of for the purpose of compensating the return or static charge of the line. A
rheostat is inserted between the said condenser C and the relays R1 and R2, in
order to somewhat retard the discharge of the former, so that it will reach the
relays at precisely the same instant as the discharge from the line. The duplex method
known as the "bridge method" may be used instead of the differential plan shown
in Fig. 1, if preferred, or instead of either of these methods, it is sometimes preferred
to employ a combination of the two, as illustrated in Fig. 3, in which the relay R¹ is
placed in the bridge wire 25, 26, and the relay R² is composed of a double set of
electro-magnets provided with differential helices, acting in conjunction with each
other upon a single armature lever common to all, the different sets of differential
helices being arranged in the sides of the bridge, as shown in the Figure.
The relays R¹ and R2 may be interchanged, R² being constructed like R¹ in Fig. 3,
and placed in the same position if preferable.
Instead of making use of two separate relays, as shown in Fig. 1, a relay having
a single pair of cores may be employed, arranged with curved pole pieces at each
end, between which the polarized armatures n and o are mounted. Fig. 4 re-
presents one end of such a relay, and Fig. 5 the opposite end of the same relay.
In Figs. 6 and 7 an arrangement is shown of the transmitting keys or devices in
reference to the main batteries, whereby a certain pre-arranged combination of
currents is caused to traverse the line in consequence of the different relative
positions of the keys; by this arrangement the receiving apparatus is simplified,
and communications can be transmitted with greater facility and certainty through
long circuits. The relay at the receiving station is provided with a polarized
armature and supplementary contact lever, and is used in connection with an

page_text: .
ordinary receiving instrument and local circuit, whereby the auxiliary relays and
local circuits or differential receiving instruments are dispensed with.
It is to be understood that the arrangement of devices, shown in Figs. 6 and 7, is
to accomplish the same object as that set forth with reference to Figs. 1, 2, 3, 4, 5,
viz., to transmit two distinct communications simultaneously over one telegraph
conductor in the same direction, or when combined with any suitable method of
simultaneous double transmission in opposite directions to transmit two distinct
communications in each direction simultaneously over a single conductor.
Referring to Figs. 6 and 7, the transmitting key t is precisely the same as the
one shown in Fig. 1. The second or double point transmitter is preferably con-
structed substantially in the same manner as the single point transmitter t¹, except
that a three armed lever 2 is employed in order to accomodate two continuity
preserving circuit springs N and O, which are mounted on insulating supports upon
the lever t, and when the transmitter is at rest, the springs N and O rest upon the
-stationary contact points n and o.
When the key K² is depressed, the electro-magnet T2 attracts its armature and
draws down one end of the lever t², in consequence of which contacts are formed
between the respective springs N and O and the insulated contact points n¹ and o¹,
while the previously existing contacts n and o are broken. This action takes place
simultaneously in case of both springs N and O, and is the same in principle as that
which occurs when the single transmitter is operated as described with reference to
Fig. 1.
The effect produced upon the electrical condition of the line by the different
positions of the keys at the transmitting station will next be described.
1st. When the First and Second Keys are both Open.-This is the position of the
apparatus represented in Fig. 6. Disregarding for the present the receiving in-
struments and their connection with the line, the circuit may be traced as follows:-
From the earth plate G through wire 1, spring b, lever t¹, wires 2 and 3, contact
point o, spring O, wires 4 and 5, battery B, wires 6 and 7, contact point n, spring N,
and thence by wire 8 through the receiving instruments to the line L. In this
position of the keys the smaller main battery B is in circuit with its positive or
+pole to the line.
2nd. When the First Key is Closed and the Second Key Open.-The route is
from the earth at G by wire 1 and spring b to the contact point a, wires 12 and 7,
and thence by the same route, as in the first case, to the line L. The battery B is
now thrown out of circuit, and there is no current upon the line.
3rd. When the Second Key is Closed and the First Key Open.-The route is
from the earth at G by wire 1, spring b, and lever t¹, wires 2 and 13, large main
battery 3, B, wire 14, contact point o³, spring O, wires 4 and 15, contact point n¹,
spring N, and wire 8 to line L. In this case the large main battery 3B, is in
circuit with its negative or
pole to the line.
-
4th. When both the First and Second Keys are Closed.-The route is from the
earth at G by wire 1, spring b, contact point a, wires 12 and 6, small main battery
B, wires 5 and 15, contact point n', spring N, and wire 8 to line L. In this case
the smaller battery B is in circuit with its negative or pole to the line.
-
The receiving apparatus consists of two sounders or other suitable receiving
instruments, 8¹, and 82, which are controlled by two relays, r¹, and 7², see Fig. 6.
The sounder s¹ responds to the movements of the key K¹, and the sounder 8² to
the movements of the key K2, while both sounders respond when both keys are
depressed. This is accomplished in the following manner:-The line wire L, on
entering the receiving station, passes through the helices of the respective relays
2, and, and thence to the earth. The relay is preferably constructed with
two electro magnets m, m³, arranged with their poles facing each other, and
provided with a polarized armature h, mounted between the opposite poles of the
electro-magnets.
The circuit of the line L, entering the relay ², passes through the helix or coil

page_text: h of electro-magnet m', and thence through the helix h³ of electro-magnet m, and
these belices are arranged in a manner well understood, so that a negative current
(for example) passing through both helices will cause the polarized armature h to
be attracted by the magnet m,. and repelled by m', while with a positive current
precisely the opposite effect will take place.
The armature of relay R2 is provided with a retracting spring 2, and operates
the sounder s, by means of the local battery P, in the ordinary manner.
The relay R' consists of two electro-magnets, p, and p', and is provided with a
polarized armature j, having a retracting spring ¹. The armatures h and may be
of hardened steel and permanently magnetized, or they may be of steel or soft
iron, polarized either by contact with a permanent magnet, or by a helix through
which the current of a constant local battery is made to circulate. The polarized
armature j, when no current is passing, rests against the free end of a contact lever
r, which moves upon a pivot. The contact lever is in turn held against the fixed
stop q by the tension of a spring q', which tension should be considerably greater
than that of the spring ; the normal position of the apparatus, when neither key
at the transmitting station is depressed, is that shown in Fig. 6.
The manner in which the receiving instruments operate in each of the four con-
ditions of the line last above mentioned is as follows:-
1st. Positive Current from Battery B.-The local circuit of sounder S¹ is kept
open by the action of the positive current upon the polarized armature ; of the
relay R¹ (which is sufficient to overcome the tension of the spring r¹), and it
remains inactive. The local circuit of the sounder S2 is kept open by the action of
the positive current of the line upon the polarized armature h of the relay R2, and
also by the tension of the spring, and therefore it also remains inactive.
2nd. No Current. The armature ; of relay R¹ is drawn by the tension of
the spring over against the contact lever r, thus completing the local circuit of
the sounder S, and actuating it, while the armature h of relay R2 remains in the
same position as before, in consequence of the action of the spring, which holds
it against the insulated stop whenever there is no current traversing the helices of
the relay, and therefore the sounder S2 is not affected.
3rd. Negative Current from Battery 3 B.-In this case the action of the more
powerful negative current is sufficient to press the polarized armature j against
the movable contact lever ?, with sufficient force to overcome the tension of the
spring q, and thus, although the local circuit is still closed between the armature
jand contact lever r, it is now broken between the latter and the fixed stop q, and
hence the sounder S₁ is not actuated. On the other hand the negative current
causes the armature h of relay R2 to be moved to the left, closing the local circuit
and actuating the sounder S
4th. Negative Current from Battery B.-The negative current from the smaller
battery is not sufficiently powerful to overcome the tension of the spring q¹, and
therefore the contact lever r remains in contact with stop q, and the armature j
with the contact lever also, thus completing the local circuit of sounder S¹, and
operating it. Relay R², which is so arranged as to close its local circuit by negative
currents of any strength, actuates the sounder S² precisely as in the third position.
By this arrangement of the apparatus the difficulties which inevitably arise from a
reversal of the polarity of the line current while a signal is being given upon one
of the receiving instruments, which difficulties have hitherto seriously interfered
with the use of multiple telegraphs, especially upon long circuits, are entirely
avoided, for the reason that in the apparatus shown in Fig. 6, the reversal of the
polarity always takes place either at the beginning or at the end of a sigual, and in
no instance during the continuance of one, as in the apparatus heretofore employed
for this purpose.
Fig. 7 represents another arrangement of the transmitters and their connections
which may be employed in lieu of that herein-before described and shown in Fig. 6,
and by means of which the required combination of currents may be obtained from

page_text: a smaller number of cells of battery. The single point transmitter is the same as
the one shown in Fig. 6. The double point transmitter may be constructed as
shown in Fig. 6, or, if preferred, in the modified form shown in Fig. 7, in which,
the circuit springs N and O are replaced by contact levers F and G, these being
pressed against opposite sides of the oscillating circuit changer E by springs 81, 8².
The circuit changer E is constructed and operates precisely the same as the one
marked E in Fig. 1, and by tracing the connections shown in Fig. 7 it will be seen
that the currents sent to the line in the various positions of the keys are relatively
the same as in Fig. 6, the only difference being that in the second method the
strength of the more powerful current is limited to twice that of the less powerful,
while in the first method the strength of the more powerful current may be
increased to any extent by simply increasing the battery 3 B.
To adapt the apparatus described in Figs. 6 and 7 to the simultaneous transmission
of four communications upon the same wire, two in each direction, a duplex telegraph
method may be employed similar to that described in connection with Fig. 1. To
this end an additional helix or coil is placed upon both the electro-magnets of each
of the relays R1 and R2, which helices contain the same length of wire and the same
number of convolutions as the helices h¹, h¹, and h², he, but exert an opposing or
neutralizing effect upon the cores of the electro magnets, and which are included in
the circuit of an artificial or branch line, as usual.
In making use of the method described in Figs. 6 and 7 in combination with the
duplex methods for the purpose of transmitting four communications simultaneously
over one wire, it is requisite that the resistance interposed between the line and the
earth at the sending station should always be the same whether the batteries are in
circuit or not. This is effected by the insertion of compensating resistances
and y, x being equal to the resistance of battery B, and y being equal to the
battery 3 B.
Another portion of this present Invention relates to an improved double acting
receiving instrument or relay which is placed at the receiving station and is com-
posed of an electro-magnet which acts upon a single armature. The said armature
is capable of being placed by the action of the electro-magnet in four different
positions, corresponding to the four possible positions of the two keys at the sending
station. By means of suitably arranged contact levers, two independent local
circuits are brought into action by the same armature in its different positions,
which circuits, in turn, actuate two independent sounding or recording instruments.
This Invention further consists in an improved combination or arrangement of
the keys or transmitters, with reference to the batteries at the transmitting station,
and also in certain improvements in the construction of the pole changing trans-
mitter.
Fig. 8 is a plan view of the improved receiving instrument or relay which forms
an important part of this Invention. Fig. 9 is a front elevation and Fig. 10 a trans-
verse vertical section of the same taken in the plane of the dotted line x, x, in
Fig. 8.
Fig. 11 is a front elevation of the double current or pole changing transmitter.
Fig. 12 is a skeleton diagram showing the connections and mode of operation of
the improved apparatus when arranged to transmit two messages simultaneously in
the same direction from one terminal station to another.
Fig. 13 shows the apparatus as arranged upon the differential plan at one
terminal station, for the purpose of simultaneously transmitting two communi-
cations to the distant station, and receiving two others from that station.
Fig. 14 is a modification of the arrangement shown in Fig. 13.
Figs. 15 and 16 show different methods of arranging the apparatus at way
stations, and Fig. 17 shows the apparatus at a terminal station arranged upon the
bridge plan.
The construction and mode of operation of the improved receiving instrument or
relay will first be described, and afterwards the manner in which it may be com-

page_text: bined with other well known apparatus in order to effect the simultaneous trans-
mission and reception of two communications in the same or in opposite directions,
or both, upon one conductor.
In Figs. 8 and 10, n, s, is an angular bent permanent magnet, preferably of
hardened steel, magnetized to saturation, the south pole 8 of which is made broad
enough transversely to form a bed, the grooved upper surface of which supports two
soft iron carriages m, m', see Fig. 10. To a lug projecting upward froin each of
these carriages is screwed the soft iron core of an electro-magnetic coil or helix, as
seen at M and M¹. The respective poles of the two cores are arranged so as to face
each other upon opposite sides of a soft iron or steel armature a which is pivoted
at n within a slot formed in the north end of the permanent magnet n, 8. The
poles projecting from the helices M, M¹, may be adjusted at any required distance
from the arinature a by moving the carriages m, m³, horizontally in either direction,
as required, and securing them in the desired position by the check-nuts d, d. The
coils M and M are included in the same electric circuit. When no current is
passing the armature a receives north magnetic polarity from the upper end of the
permanent magnet n, 8, while the cores on each side of it in like manner both
receive south polarity from the lower end thereof. It will therefore be attracted
indifferently by either pole with a strength depending upon its distance therefrom.
The effect of a positive current traversing the helices M, M', will be to strengthen
the south magnetism in the core of helix M and weaken or neutralize that in M¹,
thus causing the armature a to be attracted towards the former with a force pro-
portional to the strength of the current traversing the helices. The effect of a
negative current will, of course, be precisely the reverse of the foregoing, and the
armature will be attracted toward the coil M¹.
It is here remarked that although the combination of permanent and electro-
magnets which has been thus far described and which it is preferred to employ is
similar to that contained in the well known Siemen's relay, yet owing to the
peculir arrangement of the electro-magnetic helices and their cores with reference to
the armature, the heavy movable pole pieces of Siemen's arrangement are dispensed
with, whereby the cores themselves are rendered capable of being charged and dis-
charged with increased rapidity whenever the polarity of the current is reversed.
In any case the Siemen's relay might be used in place of the modification thereof,
which has been described without departing from the principle of this Invention.
The armature a controls the local circuits which operate the sounding or recording
instruments by means of two contact levers N and Ñ¹, Figs. 9 and 12. These con-
tact levers turn freely upon suitable fulcrums at their lower ends, while their upper
free ends, when at rest, are held against the adjustable contact points q, q', by the
tension of the adjustable springs r,; o is a contact point upon the upper extremity
of the contact lever N, and o¹ is an insulated stop occupying a corresponding
position upon the lever N¹. The contacts q, q¹ are so adjusted as to allow the
arm a', which is rigidly attached to the armature a to play between the stops o
& o upon the contact levers, which limit its notion in each direction except at
such times as the armature a moves with sufficient power to overcome the retractile
force of the springs 7, ¹, in which case the lever N or N¹ is pressed away from the
contact q or q until it strikes against the adjustable stop por p¹.
To the above described receiving instrument two independent sounding or
recording instruments S1 and S2 are connected in the manner shown in Fig. 12.
Each of the two local batteries and has one of its poles connected to the contact
lever N. The remaining pole of is connected through the sounder 8¹ to the
armature a, and the remaining pole of through the sounder s² to the contact
lever N. A connection is also made between the stops q and ql, as shown by the
dotted line.
The transmitting devices are preferably operated by connecting them either
mechanically or electrically with the levers of common Morse keys, in a manner
well understood.
The operation of the two independent transmitters or keys at the sending station

page_text: gives rise to four different electrical conditions of the line according to their
respective positions with reference to each other as follows:-
First. First and second keys, both open.
Second. First key closed and second key open.
Third. Second key closed and first key open.
Fourth. First and second keys, both closed.
The manner in which the four electrical conditions of the line are produced by
the operation of two transmitters will now be explained.
In Fig. 12 the double point transmitter is operated by the electro-magnet T¹
and local battery and key K'. The function of the double point transmitter is to
reverse the normal polarity of the main battery in respect to the line and ground
wires whenever the key K¹ is depressed, and this is effected by means of contact
springs fand g, Figs. 11 and 12, which tend to press against the adjustable stops h
and and make contact therewith, except when prevented from so doing by the
action of the lever t¹. In its normal position with the key K¹ open, the end of the
lever which acts upon the springs is depressed, as shown; thus the spring g is
separated from the stop i although it remains in contact with the lever t. The
spring on the contrary rests against the stop ht, and is separated from the lever t¹.
When the key K' is closed the position is precisely the reverse of this. The stops h
and i should preferably be so adjusted that when the lever t¹ moves up and down it
will make contact with one spring before breaking contact with the other. As the
two poles of the main battery are connected to the respective springs fand g, the
line wire to the stops h, i, and the earth to the lever t¹, it is obvious that at each
movement of the lever the polarity of the current upon the line will be reversed.
In the arrangement adopted the contact springs are not mounted upon the lever t¹,
as heretofore, but upon an independent stationary support. This mode of con-
struction simplifies the apparatus and renders it much more convenient to adjust it
properly by means of the contact screws h, i, see Fig. 12.
The single current transmitter 2 is operated by an electro-magnet T2, local
battery and key K2, and serves to determine the strength of the current going to line
without reference to its polarity; it is of well known construction and requires no
further description.
The effect produced upon the electrical condition of the line by the several
positions of the keys at the transmitting station will next be described.
It is remarked that in the arrangement about to be described two main batteries B
and 3 B are made use of, the latter being say three times the strength of the former.
1st. When the First and Second Keys are both Open.-This is the position of the
apparatus represented in Fig. 12. Disregarding for the present the receiving instru-
ments and their connection with the line the circuit may be traced as follows:-
From the earth plate G through wire 1, transmitter lever t, spring g, wire 2,
spring b, contact point c, transmitter lever t, wire 3, main batteries 3B and B,
wire 4, spring f, contact point h, thence over the line wire 6 to the helices M, M, of
the receiving instrument at the distant station, and thence by wire 7 to the earth
at G¹. In this position of the keys both main batteries are in circuit, sending to
line a negative or - current of 3B-B: = 4 - B.
2nd. When the first Key is Closed and the Second Key Open.-The route in this
case is from the earth at G by wire 1, lever t¹, spring f, wire 4, main batteries B
and 3 B, wire 3, lever t², contact point c, spring b, wire 2, spring g, contact point h,
and thence by the line 6 to the distant station as before. In this position both
main batteries are also in circuit, sending to line a positive or + current of
3B+B 4 B.
-
3rd. When the Second Key is Closed and the First Key Open.-The route in
this case is from the earth at G by wire 1, lever t¹, spring g, wire 2, spring b
contact point e, wire 8, main battery B, wire 4, spring f, contact point h and wire 6,
thence over the line to the distant station. In this position the sinaller of the two
main batteries only is in circuit, sending to line a negative or
current of a
strength of - B.
1

page_text: 4th. When both the First and Second Keys are Closed.-The route in this case is
from the earth at G through wire 1, lever t, spring f, wire 4, main battery B, wire 8,
contact point e, spring b, wire spring g, contact point h, and thence over the
line 6. In this position the smaller battery only is in circuit, sending to line a
positive or current of a strength of B. The apparatus at the receiving station
consists of the double-acting receiving instrument before described, and shown in
Figs. 8, 9, 10, 11, & 12, to which are connected two independent sounding or
recording instruments S1 and S2. It is obviously essential that one sounder should
respond solely to the movements of the key K (for example S), and the other
sounder S2 in like manner to the movements of the key K, while both should
respond when both keys are depressed.
The manner in which this result is accomplished will be understood by reference
to the following explanation of the effect of each of the last mentioned electrical
conditions of the line, and to Fig. 12 of the Drawings.
1st. Negative Current from both Batteries (-4B:).-The local circuit of
sounder S₁ is open between the point O and the armature a, and that of S² between
the lever N¹ and the stop q¹, because the action of the current upon the polarized
armature a tending to attract it toward M¹ is strong enough to overcome the
tension of the spring r¹ and force the lever N¹ against the stop p¹.
2nd. Positive Current from both Batteries, (+4B:).-The local circuit of sounder
S¹ is closed at the point of contact between arm a¹ and contact lever N, but that of
sounder S² is broken betwen the contact lever N and the stop q because the strength
of the current upon the line is so great as to overcome the tension of the spring
and force the lever N against the stop p.
3rd. Negative Current from Battery B only (- B:).-The local circuit of the
sounder S is broken between the arm a¹ and the contact o on the lever N, but
that of sounder S2 remains closed, because the power of the current upon the line,
though sufficient to move the arm a¹ away from the stop o, is not able to over-
come the spring and separate the lever N¹ from the stop q
4th. Positive current from Battery B only (+B:).-The local circuits of both
sounders S¹ and S2 remain closed, because the strength of the positive current is
sufficient to bring the arm a¹ into contact with the stop o upon the contact lever N,
but is not enough to overcome the tension of the spring r, and thus separate the
lever N from the stop g. Thus it will be understood that the armature a is caused
to assume four different positions corresponding to the four different conditions of
the line. When the armature is in either of its extreme positions the local circuit
of the sounder S2 is broken. When the armature passes directly over from one
extreme position to the other it, of course, closes the local circuit for an instant as
it passes the middle point, but not long enough to produce any effect whatever
upon the sounder S which remains inactive.
In order to adapt the apparatus above described, and shown in Fig. 12, to the
simultaneous transmission of four communications upon the same wire, two in
each direction, it is only necessary to combine it with some suitable known method
of simultaneous transmission in opposite directions. The combined apparatus for
this purpose is shown in Fig. 13, in which the helices M, M', of the receiving
instrument are each composed of two divisions having an equal number of convolu-
tions, and so arranged as to exert equal and opposite magnetic effects upon the
cores. The outgoing current through the wire 14 divides into two equal portions,
one going to the main line L and the other to the artificial line A, in which is
inserted a rheostat R corresponding in resistance to the main line. The main line
current passes from the transmitting apparatus through the wires 14 and 15, right-
hand division of helix M, wire 10, right-hand division of helix M', and thence
to the line L, while the current of the artificial line goes from the wire 14, by wire
17, to the left-hand division of helix M', wire 18, and left-hand division of helix M
to A, and thence through rheostat R to the earth at G. Condensers C' and C² are
connected to the artificial line A in the manner shown in Fig. 13, and are used for
the purpose of compensating the static discharge of the line.

page_text: In order to equalize the time of the discharge from the condensers and render it
of the same duration of that from the line, it is preferred to arrange them in such a
manner that the discharge is made to pass through adjustable rheostats v¹, v². An
independent condenser Č is arranged with one set of its plates in connection with
the main line L, and the other set with the artificial line A. No effect is produced
by this condenser upon the outgoing current, as the potential of the latter is sub-
stantially the same on each side. The incoming current from the distant station,
meeting with the resistance of the helices M, M', flows into and charges the con-
denser, which remains charged until a reversal of the current takes place upon the
line, when it instantly discharges itself and sends a momentary pulsation through
the electro-magnets M & M by the way of wires 15, 16, 17, and 18. This tends
to hasten the action of the receiving magnet upon its armature at each reversal,
and thus improves the signals upon long lines.
The effective action of this condenser may be much increased, if desired, by
augmenting the resistance of the helices M, M¹, or by inserting additional re-
sistances between these and the junction of the wires leading to the condenser on
each side.
Fig. 14 shows the receiving apparatus adapted to another method of transmission
in which the four positions of the keys K1, K2, produce the following electrical
conditions of the line. First key and second key both open, (+ B); first key
closed and second key open, (- 3 B); second key closed and first key open, (O);
first key and second key both closed; (- B). The arrangement of the receiving
instrument, local circuits, and sounders in this case is precisely the same as that
shown in Fig. 12 except that care must be taken to adjust the coil M' a little
nearer the armature a than in the other case, so as to give it a bias toward that
side. The same effect may be produced by attaching a slight spring to the arm a¹,
which will be sufficient to hold it against the insulated stop o¹ when no current is
passing.
Fig. 15 shows a terminal station arranged in precisely the same manner as that
already described and shown in Fig. 13, and also an intermediate station. A
switch is provided at each station, by turning which to the right the main
batteries are removed from the main line circuit, and a rheostat having a re-
sistance equal to the combined internal resistance of both batteries, inserted in
their stead, which enables each station to adjust or balance its apparatus without
interference from the batteries of any other station.
By means of the arrangement shown in Fig. 15 either terminal station may send
two simultaneous communications to the way station or to the other terminal
station, or to both; or it may send two and receive two simultaneous communi-
cations while corresponding with either the way or the other terminal station, but
not both at the same time.
Fig. 16 shows an arrangement well adapted to the transmission of press reports
or other matter which is to be transmitted from one station and received simul-
taneously at a number of other stations; for example, let two stations in Fig. 16
represent Baltimore and Philadelphia, the terminal stations at Washington and
New York being arranged in precisely the same manner as the terminal station in
Fig. 15. By this arrangement two simultaneous communications may be sent say
from Washington, each of which may be received independently at Baltimore,
Philadelphia, and New York, while either of these stations may interrupt the
senders at pleasure by operating their pole changing transmitters t¹, t¹.
Fig. 17 shows a method of combining the improved receiving apparatus with the
bridge duplex method. In this case either the arrangement of the batteries and
transmitting apparatus, shown in Figs. 12 and 13, or that shown in Fig. 14 may
be employed. The wire 36 leading from the transmitting apparatus divides into
two branches 37 and 38, the former leading to the main line L through the
rheostat V, and the latter to the artificial line A through the rheostat V¹.
The arrangement of the rheostat R and condenser C¹ in connection with the
artificial line is well known and therefore need not be further described. In this

page_text: case it is preferred to construct each of the helices M, M³, of the receiving instru-
ment in two divisions, the left hand division of M and the right hand division of M¹
being included in the circuit of the bridge wire 39, 40. A rheostat R2 is placed in
the bridge wire between the receiving instrument and the artificial line. The
incoming current, being partially obstructad by the rheostat R2, flows through the
wires 42 and 41 and charges the condenser C. At the instant a reversal takes
place the condenser is discharged through the wires 41 and 42, passing through
the right hand division of the helix M and the left hand division of the helix M',
and thus hastening the action of the reverse current from the distant station upon
the armature a, by which means the signals, especially upon long lines, are materially
improved.
Another portion of this Invention consists in the peculiar construction and
arrangement of a differential receiving instrument, operated by changes in the
strength of the current in combination with a condenser which is charged and
discharged by the current traversing the bridge wire, by means of which combi-
nation the mutilation of the signals upon this instrument, resulting from the
reversal of the polarity of the line current, which has hitherto formed a serious
obstacle in working long lines, is more effectually prevented.
It is to be understood that this last-mentioned feature of Invention is to be used
with that class of telegraphs in which two receiving instruments are employed at
each terminal station, one being operated by changes in the polarity of the line
current without reference to its strength, and the other by changes in the strength
of the current without reference to its polarity.
In Fig. 18 P represents a polarized relay or receiving instrument which is
operated solely by changes in the polarity of the current, and R represents a neutral.
relay which is operated solely by changes in the strength of the current. In some
instances this relay is also provided with a polarized armature.
The main magnet
of the receiving instrument R is provided with two equal and opposing helices m, n,
preferably arranged in the manner shown, although this precise arrangement is not
'very material. The rheostats or resistances A and B, which form the first and
second sides of the bridge, are preferably made equal to each other, and this being
the case, the resistance x should of course be made equal to the resistance of the
line. When the respective resistances are thus arranged the bridge wire 3, 5,
polarized receiving instrument P, and condenser C, will be in a neutral position in
respect to outgoing currents. The receiving instrument R is provided with an
auxiliary magnet r, which acts upon the same armature lever with the main
magnet m, n. This auxiliary magnet is inserted in a wire 7 which is connected to
the bridge wire 3, 5, and through which the condenser C is charged and discharged.
The charging and discharging of the condenser is effected as usual by means of a
rheostat D placed in the bridge wire between the point of junction of the wire 7
and that of the wire 8, which is attached to the opposite pole of the condenser.
The outgoing currents without regard to their strength or polarity pass over the
wire 1 to the point 2, where they divide into two equal portions, one portion going
to line by way of A, 3, m, and 4, and the other to earth by way of B, 5, n, x,
and 6. The bridge wire 3, 5, being neutral in respect to outgoing currents the
instrument P will not be affected, nor will the instrument R, for the reason that
the currents traversing the opposing helices m, n, are necessarily equal to each
other. For the purposes of this explanation it is only necessary to take into
consideration the effects of such incoming currents as are of sufficient strength to
actuate the receiving instrument R. In this arrangement the full strength of the
incoming current, whatever may be its polarity, passes unopposed through the
helix m of the instrument R, and thence to the point 3 where it divides, one portion
going to earth by way of A, 2 and 1, another portion by way of 5, B, 2, and 1, and
the remainder by way of 5 through the other coil n of the receiving instrument R
(its direction now being such as to assist the action of the other helix m), and thence
through the rheostat x to the earth.
The incoming current traversing the bridge wire from 3 to 5 being partially,

page_text: obstructed by the rheostat D, a portion of it flows through the wire 7 and charges
the condenser C. If now the polarity of the current upon the line be suddenly
reversed for the purpose of operating the polarized receiving instrument P the
armature of the instrument R tends to fall off momentarily while the change of
polarity is taking place, but this action is prevented by the discharge of the con-
denser C through the wire 7, which occurs at the same instant, and-acting upon the
auxiliary magnet r retains the armature lever a in its place.
Another portion of this Invention relates to that 'class of duplex telegraphs by
means of which two separate communications are made to traverse the same wire
at the same time, one series of signals being transmitted by changing the polarity
of a constant current, and the other series of signals by changing the strength of
the same current, and the improvements consist in placing the receiving instrument,
which responds to changes in the strength of the current, in such a position that
the polarity or direction of the current which traverses its helices is always the
same, and in attaching a local circuit and a sounding or recording instrument to the
key, which transmits signals by opening and closing a shunt which passes around a
rheostat included in the main circuit.
Fig. 19 is a diagram showing the application of the Invention to the simultaneous
transmission of two communications in opposite directions; Fig. 20 shows the
method of attaching a local circuit and sounder to the key or transmitter; Fig. 21
shows the manner in which an intermediate station may be arranged for simul-
taneous correspondence with the terminal stations; and Fig. 22 shows a modification
of the Invention, by which two communications in one direction, or in opposite
directions, may be transmitted simultaneously.
In Fig. 19 t is the lever of a double current or pole-changing transmitter, which
is operated by an electro-magnet T¹, local battery, and key K¹." The office of this
transmitter is to reverse the poles of the main battery E, in respect to the line L,
and the ground G, each time that the key K¹ is depressed by the operator at
station A. The construction and operation of this transmitter has been already
described.
At station B a receiving instrument R¹, having a polarized armature, is placed in
the circuit of the line, and in consequence of the polarity of its armature will
respond to each reversal of the current upon the line produced by the movements
of the double-current transmitter t¹, and will open and close the local circuit of the
sounder S¹, giving signals corresponding to the movements of the key K¹. The line
at station B, after passing through the receiving instrument R¹, is conducted to the
earth at G. A rheostat a is inserted, preferably, between the receiving instrument R¹
and the earth, the resistance of which may be, say, from twice to four times as
great as that of the line. A key K2 is connected with the line in such a manner as
to shunt the rheostat x by a circuit of practically no resistance each time it is
depressed. At station A a receiving instrument R2, which may be provided with a
neutral armature and an adjustable spring, is placed in one of the wires leading
from the battery E to the double-current transmitter. The armature of the receiving
instrument R2 opens and closes the local circuit of the sounding or recording
instrument S2 in the ordinary manner.
The retracting spring of the receiving instrument R² should be strained up to a
sufficient tension to withstand the attraction of the electro-magnet when the
rheostat X is in circuit at the other station, while it will be easily overcome by the
increased force of the line current, which results from the shunting of the rheostat ✗
and the consequent removal of its resistance from the circuit whenever the key K²
is depressed.
By placing the receiving instrument R² in one of the wires leading from the
battery to the pole-changing transmitter t¹ the direction or polarity of the current
traversing its coils is never changed, and consequently its armature has no tendency
to fall off when the current is reversed upon the line.
In order that the operator at station B. may be able to hear his own signals it is
preferred to arrange the apparatus at that station in the manner shown in Fig. 20. The

page_text: key K2 is provided with a spring contact arm k, which, when the key is depressed, is
brought in contact with the stop j, thus shunting the rheostat x and giving the signal at
station A, in the manner herein-before described. The ordinary contact point of the key
at or nearly at the same time strikes upon its anvil, and closes the circuit of the local
battery e through the sounder t, and thus duplicates the signal sent to the other station.
In Fig. 21 the connections of the key K2 at station B, and of the receiving
instrument R at station A, are reversed, so that signals are transmitted from B to A
by increasing the resistance of the line, the rheostat x being thrown into circuit
when the key K2 is depressed, and the signal being recorded at A by the falling off
of the armature of the receiving instrument R². This arrangement is very con-
venient when it is desired to place one or more way stations upon the line, as, for
example, station C in Fig. 21.
It is obvious that a communication may be sent by means of key K³, and received
at station A upon the receiving instrument R2, while at the same time a com-
munication may be sent in the other direction by the key K₁ and received upon the
polarized receiving instruinent R³.
It is also obvious that any desired number of receiving instruments similar to R¹
and R³ may be placed in the circuit, and that they will all respond to the signals
given by the key K²
Fig. 22 shows a modification of the Invention, which is so arranged as to be
capable of either transmitting two communications simultaneously from A to B, or
one in each direction, at pleasure. If the keys K¹ and K are operated at the same
time the former will control the polarity and the latter the strength of the current
going to line from the battery E. At station B a receiving instrument is made use
of, the construction of which has been fully herein-before described. The polarized
armature a plays between two contact levers N and N', which are held against the
stops q, q, by springs 1, 2, these springs being strained up to a tension sufficient to
resist the electro-magnetic action of the weak current which traverses the line when
the rheostat x is put in circuit by the depression of the key K, but which will
readily be overcome by the stronger current which passes when the rheostat is cut
out. Under these circumstances it will be seen that the sounding or recording
instrument S¹ will respond each time the key K' is depressed, while in like manner
the sounding or recording instrument S will respond each time the key K' is
depressed. In order to transmit communications in opposite directions at the same
time the operator at station A will use the key K₁ and the operator at station B
the key K2, and in this case the latter operator will hear his own signals upon the
sounder S, and those of the distant operator upon the sounder S'.
What is claimed and to be secured by Letters Patent is,-
First. In a duplex or multiple telegraph two transmitters connected with the same
line wire, one having a device so constructed and arranged as to close one branch
of the circuit before opening another, and the other provided with two separate and
simultaneously acting devices of like construction and arrangement, in combination
with two independent batteries, so that one battery may be made to send to line.
either a positive or a negative current, and the other a current of one determinate
and invariable polarity, without in any case interrupting the main circuit, sub-
stantially as and for the purposes specified.
Second. The oscillating double circuit changer E, F, G, (Fig. 1), in combination
with an electro-magnet local battery and key, substantially as specified.
Third. A compound differential relay consisting of a permanently polarized
armature, so arranged as to be impelled in one direction or the other, according to
the polarity of the magnetizing current by the attraction and repulsion of two or
more separate electro-magnets, and provided with differential helices simultaneous
brought into action by the said current, substantially as herein specified.
Fourth. A receiving instrument or sounder and a local battery in combination
with a relay consisting of one or more electro-magnets provided with an armature
or armatures capable of being moved from one extreme position to the other by a
R

page_text: change of polarity in the line current, and one supplementary contact lever, so
arranged in reference to the said armature that the receiving instrument will be
actuated when the armature is at rest in either of its extreme positions, but not
when at rest in an intermediate position, substantially as specified.
Fifth. A receiving instrument having a differential electro-magnet, the opposing
coils of which are included in separate local circuits, or in separate branches of a
common local circuit in combination with a relay, so arranged that when its polarized
armature is moved in one direction by the action of a positive current traversing
the main line it will open one, and when moved in the opposite direction by a
negative current it will open the other of the two opposing local circuits, and in
either case the receiving instrument will be actuated.
Sixth. Two keys or transmitters and one or more main batteries at one station
in combination with a line wire, and with one or more receiving instruments at
another station, when so arranged that a current of one polarity will traverse the
line when both keys are depressed, and a current of equal strength, but of opposite
polarity, when both keys are elevated, substantially as and for the purpose
specified.
Seventh. Two keys or transmitters and one or more main batteries at one station
in combination with a line wire, and with one or more receiving instruments at
another station, when so arranged that a current of a given strength and polarity
will traverse the line when both keys are at rest, which current will be diminished
or interrupted by the depression of one key, while it will be increased and its
polarity reversed by the depression of the other key, substantially as and for the
purposes specified.
Eighth. A receiving instrument or sounder and a local battery in combination
with a relay consisting of one or more electro-magnets provided with an armature
or armatures capable of being moved from one extreme position to the other by a
change in polarity in the line current, and a supplementary contact lever so arranged
in reference to said armature that the receiving instrument will be actuated when
the armature is at rest in an intermediate position, but not when at rest in either
of its extreme positions, substantially as herein specified.
Ninth. A receiving instrument having one arinature so arranged as to respond to
changes in the strength and in the polarity of the line current either or both
in combination with two independent sounding or recording instruments.
Tenth. Two independent keys or transmitters in combination with a receiving
instrument having one armature, so arranged as to respond to changes in the strength
and in the polarity of the line current, either or both, and two independent sounding
or recording instruments.
Eleventh. Two independent keys or transmitters so arranged with reference to
each other and to a main battery or batteries that their separate and combined
action is capable of producing four distinct electrical conditions in the main line,
differing from each other in respect to the strength or polarity of the current, or
both, in combination with a receiving instrument having one armature so arranged
as to be capable of being placed in four different positions corresponding respectively
to the four electrical conditions of the main line and two independent sounding or
recording instruments.
Twelfth. A key or device for transmitting signals by changing the polarity of the
line current, and an independent key or device for transmitting signals by changing
the strength of the line current in combination with a receiving instrument having
one armature so arranged as to respond to changes in the strength and in the
polarity of the line current, either or both, and two independent sounding or recording
instruments.
Thirteenth. A key or device arranged to transmit signals by reversing the
polarity of the normal main line current in combination with a second key, which
when depressed transmits a signal by diminishing or weakening the normal current
irrespective of the polarity of said current.

page_text: Fourteenth. In a receiving instrument a polarized armature acting upon two
movable contact levers one of which presents a contact point and the other an
insulating point to the said armature or its extension in combination with stops
which serve to limit the movement of each of the said contact levers in each
direction.
Fifteenth. The vibrating lever t' of a pole changing transmitter in combination
with the contact springs and g mounted upon a fixed support, and the adjustable
stops and i, substantially as and for the purpose specified.
Sixteenth. A receiving instrument composed of a differential magnet whose
opposing coils are respectively included in the circuit of the main and of the
artificial line, in combination with an auxiliary magnet so arranged as to be operated
by the charge or discharge of a condenser.
Seventeenth. A receiving instrument provided with two electro-magnets acting
upon the same armature lever, one a differential magnet, whose opposing coils are
respectively included in the circuit of the main and of the artificial line, and the
other so arranged as to be actuated by the charge or discharge of a condenser in
combination with a rheostat inserted in the bridge wire to effect the charging of
said condenser, substantially as and for the purpose herein specified.
Eighteenth. A pole changing key or transmitter and a battery in combination with
a receiving instrument placed between the said battery and the key or transmitter,
substantially as specified.
Nineteenth. A pole changing key or transmitter, a battery, and a receiving
instrument placed between the key and the battery, so constructed as to respond to
changes in the strength of the main line current in combination with one or more
receiving instruments which respond to changes in the polarity of the current
irrespective of its strength, and one or more keys or transmitters which transmit
signals by increasing and decreasing the strength of the current.
Twentieth. A rheostat in the main line circuit, and a key which transmits
signals by breaking and closing a shunt passing around said rheostat in com-
bination with a sounding or recording instrument and a local battery, the circuit of
which is opened and closed by the movements of the key when transmitting signals
upon the main line.
In witness whereof, I, the said Edward Griffith Brewer, have hereunto set my
hand and seal, this Thirteenth day of July, in the year of our Lord One
thousand eight hundred and seventy-seven.
E. G. BREWER. (L.S.)