Improvements in Multiplex Telegraphy.
Year: 1890

page_text: Date of Application, 11th Nov., 1890-Accepted, 31st Jan., 1891
COMPLETE SPECIFICATION.
Improvements in Multiplex Telegraphy.
I, CHARLES ADOLPH GISBORNE of 7 St. Paul's Churchyard in the City of
London Gentleman do hereby declare the nature of this invention a communication
to me from abroad by David Herbert Keeley of Ottawa in the County of Carleton
Province of Ontario Canada Electrician and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement :-
This invention consists in a new arrangement of signalling apparatus adaptable to
any synchronous system that is designed to provide for the rapid transference of a
line wire from one set of apparatus to another simultaneously at all stations with
which it is connected.
It is well known that by such means a multiplication of circuits is obtainable in
a single telegraph wire.
Hitherto the operation of the several circuits so obtained has been attempted by
means of intermittent currents of one polarity, or by irregularly reversed currents,
applied at the transmitting end alone and the apparatus employed has not been well
adapted for the purpose intended. The consequence of which has been that the
operations have been confined to terminal stations, and the signalling capacity of a
telegraph wire has not been even fairly developed.
The invention herein described provides for the accommodation of intermediate
as well as terminal stations and utilizes the capacity of a telegraph wire for the
transmission of electrical effects to the fullest extent.
Figure 1 shows the signalling apparatus and plan of operation.
Figure 2 shows the same arranged in conjunction with a spring-jack switch.
Figure 3 shows a detail of the brush contracts.
Figure 4 shows the arrangements for three stations on a line of ordinary length.
Figure 5 shows the apparatus and connections for a terminal station on a long
line, and
Figure 6 shows the same in conjunction with spring-jack switches.
For my purpose the synchronous mechanism with which my signalling apparatus
may be associated revolves the main line brushes about the circle of contacts con-
nected with the signalling apparatus, at all of the stations in circuit with at
least sufficient frequency to put the line in contact with each of the corresponding
sets of apparatus once in every of a second, and it also rotates a commutator of
a sufficient number of segments to produce at least 24 reversals per second of the
main line battery connected with it at each terminal station.
-
The batteries, according to this invention, are reversely connected with the com-
mutators, consequently presented to line at one end is met by presented at the
other end; the currents combine in the line; and as they are alternated by the
revolving commutators, the line is traversed by regularly recurring + and
pulsations.
-
The passage of the main line brush over the contract plate connected with the
signalling instruments is concurrent with the transmission to line of any one phase
+ or - of the main line current hence if two equi-distant contacts are provided for
each set of signalling instruments, as shown in Figure 1, one contact plate will
regularly receive the + and the other the pulsations, or if but one contact is pro-
vided for each set of instruments as shown in Figure 5 it will receive the + and -
currents alternately. It will be understood from the context that the expression
one contact comprehends any number of equi-distant points in a circle, electrically
connected and similarly the expression two equidistant contacts comprehends
11
-

page_text: any number of equi-distant points of which the alternations are electrically
connected.
In transmission by the means herein described, the receiving instruments are
operated by the batteries at both terminal stations conjointly.
On lines of ordinary length the apparatus is arranged as in Figures 1, 2 and 3,
according to which the keys at the intermediate and terminal stations operate to
interrupt the continuity of the circuit thus preventing the passage of the currents
otherwise obtaining.
On a very long line the apparatus at the terminal stations is arranged somewhat
differently for it is elsewhere herein shown that at the receiving end of any one of
the multiple circuits + and currents are alternately presented to line while at the
sending end the path for the current + or might, according to the position of the
transmitting key be interrupted. This interruption so far as the line is concerned
only exists during the passage of the line brush over a single contact in each of the
series in the cycle of its revolutions it is therefore very brief. And on a very long
line the current presented at the distant end during this brief period of interruption
of the circuit at the transmitting end, will electrify or charge the line sufficiently to
affect the receiving instruments at the end where the charge obtains. Now this
charge at the distant end does not obtain where, instead of an interruption of the
circuit at the transmitting end, a reversed current is put to line in the interval
corresponding to an interruption of the path for a given current, because when like
poles are opposed the potential is nil. In order therefore to obviate the above
described electrification or charge the apparatus at the terminal stations is arranged
for operation on a long line as shown in Figures 5 and 6. When the apparatus is
arranged in this way the superfluous charge at the distant end is foiled and obviated
as the keys at the transmitting end in this case operate to determine (by the
presentation of a like or unlike pole to line) whether a current of one phase or the
other shall or shall not pass over the line from the distant end.
to
The arrangements for a way station on a short line or a long one are uniformly
as shown at B in Figure 3 and in the transmission the keys merely operate
interrupt the passage of the currents conjointly emanating from the terminal stations,
the instruments in circuit are therefore always operated by the terminal batteries.
The operation of the apparatus will be readily understood by an examination of
Figure 1 which represents the connections for one circuit in a line of ordinary
length in detail.
As all of the circuits in a multiplex system of this kind are identical, the
explanation of one will suffice. In the figure the apparatus is connected with two
main line contact plates 4+ and 4 - placed at diametrically opposite points of a
circle, whose periphery is for convenience of explanation laid flat or lengthwise as
shown at Figure 1ª. I is an induction coil of any suitable form p. p. represents
the primary wire and s the secondary R is a polarized relay normally resting on its
back stop.
Tis a transmitter such as is used in duplex telegraphy, and is
operated by the electro-magnet Tm, key K and battery T.. in the usual
way.
The front contact o of the transmitter is connected by wires w f. we, to the main
line plate 4+ and the back contact n is connected by wire w d, to the main line
plate 4
S is a switch disposed in the same manner as the circuit closer on an
ordinary Morse key and serves to bridge the contracts o, and n, of the transmitter,
by the lug c, in connection with the wire rod and the arm a in connection with the
wire we. The primary wire p p. of the induction coil I is included in the main line
circuit which when the switch S is open is traced from earth at G by brush B
battery M B commutator C brush B wire to g, primary p p. wire we to transmitter
spring d thence when the key K is closed and the lever Tr is depressed by con-
tact o and wires wf, we, to plates 4+, or when the key K is open and the lever T
is upraised by contact n and wire w d, to plate 4-. And when the switch S is
closed (as shown in the figure) by contact n wire w d, to 4 or via lug c, arm a
and wire we to 4 + or by contact o wires wf, we to 4 + or via the arm, a, lug c
and wire w d, to 4-.

page_text: -
And
The main line brush M passes over the + series of plates concurrently with the
passage of a + section of the commutator C, under the brush B. And the brush M
passes over the series, when a - section of the commutator C, is under the
brush B. This action occurs regularly and uniformly. Hence when the switch S
is open the path for the pulsations of one polarity or the other, determined by the
position of the transmitter, will be interrupted. Thus, if the key K is depressed
and the transmitter is thereby actuated putting the spring d in contact with the
point o, the circuit will be complete for the passage of the + currents when the
line brush M passes over a + plate while the contact is broken at n and no path is
afforded for the pulsations when the line brush M passes over a
- plate.
if the key K is upraised and the transmitter rests with the spring d, in contact
with n the circuit will be complete for the currents, while the contact is broken
at o thereby interrupting the path for the + pulsations. The position of the keys
therefore determines the circulation of + or - currents in the circuit. When the
switch S is closed the + and pulsations pass by way of the plates 4+, and 4
regularly to line. The arrangement of the receiving instruments is as follows:-
The secondary wire S, of the induction coil I, is in local circuit with the polarized
relay R, the plates 4a and the brush L, are the terminals of the local circuit, it is
traced from 4 u, by wire wb, to S, thence by wire wa, through R, and by wire w,
to L. The plates 4 a, are connected together and are the accompaniment of the
main line plates 4+ and 4-. The arrangement of these plates is clearly shown
in Fig. 1a. The brushes M and L, are exactly parallel and travel together. The
local plates are fixed a little in advance of the main line plates, consequently the
brusli L, will be ou 4u, and close the local circuit (in which the secondary wire S,
of the induction coil, and the relay R, are included) before the main line brush M
will be in the contact 4 or 4+ and L will leave 4 a and open the local circuit
before M will have left 4 or 4+.
-
-
-,
This action is clearly illustrated in Figure 3 (a) (b) (c). The consequence of
this action is that the induced effect due to the introduction of the main line current
into the primary of the induction coil will be communicated to the relay R and the
induced effect due to the withdrawal of the main line current (after L has left 4 a)
will be obviated. IIence the induced currents that operate in the secondary circuit
alternate in polarity in accordance with the currents that are introduced into the
primary of the induction coil I.
It follows therefore that if the switches S in a given circuit throughout the line,
were closed, thus affording paths for the currents + and as has been explained the
main line currents and alternately would be transmitted to any given polarized
relay R, and the lever thereof would oscillate between its back and front stops;
whereas if at any station the switch S, were opened, only the currents of one
polarity dependent upon the position of the transmitter could circulate in the
circuit, and all of the relays simultaneously in circuit would be actuated in
response to it. The interchange of signals is therefore readily and casily
accomplished.
A
As in a multiplex system of this kind, the length of time during which the
main line brushes are in contact with a given set of contact plates at the several
stations is extremely brief, it has been found desirable to effect a discharge of the
line before cach reversal, so as to secure the greater efficiency of the signalling
current. In systems operated by irregularly reversed currents, narrow segments
connected to earth are inserted between the successive plates for this purpose.
similar, arrangement is shewn at Figure 1a its function is however somewhat
different, as only currents of one polarity occur during the passage of the main line
brush over a given series of the contracts, and between each series an earth plate E
as large as may be desired is provided whereby the line is effectually discharged
after each + or - phase of the current has traversed it. The space occupied by
the earth plate E is also made sufficiently large when required to accomodate the
contact plates for the correcting devices of the synchronous system with which the
apparatus is associated. The object of the narrow segments placed between

page_text: the contact plates and connected with the earth plate, is to check the current in its
tendency to rise when traversing several closed circuits in succession the result of
which would be to charge the line to such an extent that the brief interruption
caused by the opening of any one circuit, would be insufficient to produce the effect
properly due to it.
-
The use of the transmitter Tr. secures continuity of connection between the
receiving instruments and the contact plates in the + and divisions of the circle
traversed by the main line brush, thus obviating the partial loss of a current
pulsation that could otherwise occur during the transition of an ordinary key or its
equivalent between its back and front contacts.
The use of induction coils employed in the manner indicated secures a more
rapid production of the transmitted signals that can be effected in the receivers
when these are placed directly in circuit. It is found that in the latter case three
successive impulses of the current are requisite to actuate a given relay, whereas
with the induction coil intervening a single impulse is sufficient. The explanation
appears to rest in that on the one hand the self-induction in the relay coils opposes
the brief energizing current to such an extent that only a very small degree of
magnetism is developed by each impulse; and, on the other hand, the convolutions
of the primary wire of the induction coil are not necessarily so numerous as those
of the relay, the self-induction in the primary is therefore not so great and the
energizing current has more power in it, while in the secondary circuit the self-
induction (which is in the same direction as the energizing current in the primary)
opposes the induced current and in a measure counteracts the tendency of the latter
to neutralize the energizing effect of the primary current, whence the effect is
enhanced and prolonged; as is evidenced in the relay to which it is communi-
cated.
In Figure 2, the apparatus of Figure 1, is represented in conjunction with a
triple-spring-jack switch S. J, the object of which is to render the signalling
instruments and circuits interchangeable. The several parts and connecting wires
are similarly lettered so that the tracing of the circuits in both is identical. The
upper contacts of all of the two outer spring-jacks are electrically connected with
the wire wg already mentioned in Figure 1. Their lower contacts and are
connected respectively with the wires we and w d. The upper contacts y' of the
middle spring-jack is connected with wire ; and its lower contact y with wire w b.
The contact plates on the knife F are connected with the correspondingly lettered
wires leading to the instruments, as can be readily seen.
Figure 4, shows a line with three stations, terminals A, C, and way station B.
The terminals are represented with five circuits (any number might have been
represented), all connected with spring-jack switches; signalling instruments are
included in the circuits I and 4. All of the parts are identical, and lettered to
correspond with those represented in Fig. 2. To avoid confusion in the drawing,
the way station B, is represented with connections for only the two circuits 1 and 4,
with instruments included in the circuit 1. The remainder of the circuit contacts
are represented as being in electrical connection "through." The brushes and
contact plates are duplicated, and, as shown, the signalling apparatus is put in
circuit between the two sets; ground plates gp, are also provided. The object of
this arrangement is to afford independent communication on either side of the
station at pleasure. It will readily be seen that the arrangements are exactly
similar for any number of circuits. Any number of intermediate stations like B,
could be put on the line, but as the arrangements at all of them would be identical,
the representation of one will be sufficient for explanation.
In the figure (4) the main batteries M B, M B¹, at the terminal stations A, C,
respectively, are concurrently in circuit and reversed not less than 24 times per
second; and, as already explained, these supply the working currents to the line.
There is no main line battery at the way station B. The drawing represents
station A sending to B and C, on circuit 1, with key closed at A; and A sending
to C, on circuit 4, with key open at A. These two conditions cover the whole of

page_text: what takes place in the operation, and from the explanation given in connection
with Figure 2, the parts being similarly lettered throughout, the connections can
be readily traced and the operation clearly understood. The only parts unexplained
in detail are the triple spring-jacks duplicated at the way station B. In these the
upper contacts,, of the two outer spring-jacks, under W, the (unplugged)
ground switch plate g, p, and the upper contacts a, 2 of the two outer spring-
jacks, under E a, are connected together. The remaining contacts under W, are
connected as follows:-
with Figure 2, the parts being similarly lettered throughout, the connections can
be readily traced and the operation clearly understood. The only parts unexplained
in detail are the triple spring-jacks duplicated at the way station B. In these the
upper contacts,, of the two outer spring-jacks, under W, the (unplugged)
ground switch plate g, p, and the upper contacts, 21 of the two outer spring-
jacks, under E a, are connected together. The remaining contacts under W, are
connected as follows:-
Lower & by wire we to plate 1x of the West side main;
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w d
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23
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Upper y¹
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20 to brush L
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local ;
Lower y
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w b to plate I a
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The contact under Ea are connected as follows;
Lower a by wire ce to plate IX of the East side main ;
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22
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2
w d
I
22
32
Upper y¹
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w to brush L
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Lower y
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wb to plate I
a
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local ;
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The spring-jack connections for circuit + are precisely the same. No instruments
are, in the figure, introduced into this circuit. When the main brushes M (w)
and M (Ea) are on the plates 4+, 4-, respectively, the circuit is traced from 4+;
by wire we to under W, X to Z, through gp to land, under Ea, z wire w, d
to plate 4 it is therefore completed "through" and uninterrupted.
The instruments inserted in circuit 1 are connected to the spring-jack knife in
the way described in Figure 3, the parts are correspondingly lettered.
Figure 5, shows the arrangements for a terminal station on a long line, where it
becomes necessary to obviate the effects of charge from the battery at the distant
end during the interval when a given key at the transmitting station operates to
interrupt the circuit. The induction coil, polarized relay, local contact plates, and
brushes, are arranged as already described.
A single series of main line contacts, or the double series, connected in
diametrically opposite pairs, is sufficient for my purpose in this case.
The main line brush M, makes contact with the apparatus, as before, not less
than 24 times per second, and the commutator C, presents an equal number of
reversals concurrently. Two transmitting batteries M B, M B', are employed at
each terminal station. Taking circuit 4, for example, in the normal condition of
the apparatus with the switches S. 4 on the contact a the currents alternately
presented to the brush B, by the commutator ( will pass by wire w, contact a,
switch arm S, by wire st, through the primary wire of the induction coil 1,
wire to plate 4, thence to line. The plate 4, is touched by the brush M, once
during the existence of each succeeding phase, and of the current; the alternate
currents are therefore uniformly and regularly presented to line. The same
condition obtains at the distant terminal station. The currents combine in the line
and affect the receiving instruments arranged for operation as already fully
explained in the other figures. When the switch is closed as represented at S' in
the circuit 1: the connection between the commutator brush B and the main line
plate is broken, the circuit in this case depends on the position of the lever T
which is operated by the electro magnet T m, key K, and battery T, and takes
the place of the duplex transmitter shown in the other figures. When the key K
is open, and the lever T is on the contacte as shown in the figure, the
from the battery M B', is presented steadily to line: the circuit being traced
from M B by wire wa, contact r, lever T, wire contact c, switch arm S¹
wire s, through the primary wire pp, of the inductor g' and wire w, b, to the plate L
thence to line. This being the case, a + pulsation presented to line, at the distant
terminal station will combine with the here presented and will operate, say, to
-
current

page_text: -
-
-
-
open the relay connected in circuit; whereas a current presented at the distant
end will oppose, and be opposed by, the current here presented, hence no effect
will be produced in the circuit and the relays will remain open. Likewise when
the key is closed and the lever is depressed as shown in circuit 3, the + current
from battery M B is presented steadily to line the circuit being from M B +, by
wire wh, contact o, lever T3 wire ³ contact c, switch arm S³ wire, through the
primary wire p, p by wire q³ to plate 3 thence to line. In this case if a + current
is presented to line at the distant terminal no effect will be produced in the circuit,
and the relays will remain open; but if a current is presented at the distant
end, the two currents will combine in the line, and will operate to close the relays.
As the and currents are put to line at the distant terminal at least 24 times
in a second, which is faster than any manipulation can be effected it follows that
the relays in a given circuit will promptly respond to the key at the transmitting
station no matter how long the line may be on which this apparatus is operated.
In Figure 6, the apparatus of Fig. 5 is also represented in combination with
triple spring-jack switches for the convenient interchange of the signalling
instruments and circuits. The several parts and connecting wires are similarly
lettered so that the tracing of the circuits in both is identical. The jaws of the
third jack in each instance are permanently insulated; all of their upper
contacts etc., are connected by wire wa to the battery M B¹, and all of
the lower's by wire wb to the battery M B. The upper contacts are connected
by wires etc. to the line plates; and the lower 's are connected by
wire w, to the commutator brush B. The upper contacts y¹, y², etc. are connected
by wires d', d, etc. to the local contacts plates 1 a, 2 a, etc. and all of the lower y,
are connected by wire with the brush L.
The description of my apparatus is now complete.
Having now particularly described and ascertained the nature of my said
invention as communicated to me by my foreign correspondent I declare that
what I claim is :-
First. The combination of induction coil with the polarized relays, and the
arrangement of the local contact plates 1 a, 2 a, etc., and brush L, for completing
and interrupting the circuit embracing the relays and secondary wires of the
induction coils whereby only one induced effect is communicated to the relays
from each pulsation + or - transmitted.
Second. In multiplex telegraphy the combination with continuity preserving
duplex transmitters of two sets of main line contacts arranged to receive the
plus and minus currents respectively.
Third. In multiplex telegraphy, commutators at both ends of the line operating
to present currents to line concurrently plus at one end and minus at the other,
and the reverse, alternately, in combination with an arrangement of keys and
transmitters whereby when the keys are depressed the path to line for the
currents of one polarity is interrupted, while the path for the currents of opposite
polarity is established, and when the keys are upraised the reverse effect is
produced.
Fourth. In multiplex telegraphy commutators and batteries at both ends of
the line arranged normally to concurrently send to line, from both ends,
alternately reversed currents, and the arrangement of keys and transmitters in
combination therewith operating when the keys are depressed to send a current
of one polarity uniformly to line, and when the keys are upraised to send a
current of opposite polarity to line, to combine with or to oppose the currents
emanating under the normal condition from the distant terminal stations.
Fifth. In multiplex telegraphy, an apparatus located at an intermediate station
operated by means of currents conjointly emanating from the terminal stations
or from stations on either side thereof.
Sixth. The connections of the apparatus at the terminal and intermediate

page_text: stations in combination with spring-jack switches whereby a given set of
apparatus may be introduced into any one or other of the several operating
circuits at pleasure.
Seventh. The arrangement and connections of the apparatus at the intermediate
stations in combination with duplicate contact plates and brushes, and duplicate
spring-jack switches and earth plates, whereby the line may be grounded in any
one or more of the multiplex circuits without interference with the others, and the
signalling instruments may be introduced into any circuit on either side of the
ground plate at pleasure thus rendering each and every circuit independently
available and adaptable as an ordinary single circuit Morse line, all substantially as
set forth.
Dated this 11th day of November 1890.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.