Year: 1886

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I ABNER MULHOLLAND ROSEBRUGH of 121 Church Street in the City of Toronto
in the Province of Ontario Canada Surgeon do hereby declare the nature of this
Invention to be as follows:-
According to my Invention for facilitating the employment of a metallic circuit
for telephones working ordinarily on a grounded circuit to an exchange the metallic
circuit arrangement being required when communicating through the exchange to
some station connected therewith by any suitable arrangement for the purpose
I employ an insulated line or circuit wire which runs round to the stations of the
different subscribers in simple circuit arrangements being made (automatic or
otherwise) to switch the subscribers instruments from the grounded connection to
the aforesaid insulated circuit wire.
By giving the subscriber a double installation the instruments of one installation
being differentially wound the subscriber is enabled to communicate through the
same lines to two different exchanges or to two different sets of subscribers at
pleasure each exchange or set of subscribers being independent of the other.
Thus it will be seen that by giving each subscriber a return wire and specially
wound telephonic apparatus several important points are gained as for instance
firstly either a single wire or a metallic circuit may be used for communicating
with the Central Office or with subscribers of the same Exchange secondly a
metallic circuit may be used for communicating with subscribers of a distant
Exchange and thirdly a double wire between two exchanges may be used simul-
taneously by two subscribers and by an operator at each Exchange-In the latter
case however differentially wound transmitters and receivers would be used by the
operator at the Exchange. Offices as well as by the subscribers.

page_text: тирrоvешения и толерного кустошь
! I ABNER MULHOLLAND ROSEBRUGH of 121 Church Street in the City of
Toronto in the Province of Ontario Canada Surgeon do hereby declare the nature
of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:—
According to my Invention for facilitating the employment of a metallic circuit.
for telephones working ordinarily on a grounded circuit to an exchange the
metallic circuit arrangement being required when communicating through the
exchange to some station connected therewith by any suitable arrangement for
the purpose I employ an insulated line or circuit wire which runs round to the
stations of the different subscribers. By giving the subscriber a double installation
the instruments of one installation being wound differentially to that of the other
the subscriber is enabled to communicate through the same lines to two different
exchanges or to two different sets of subscribers at pleasure each exchange or set
of subscribers being independent of the other.
Thus it will be seen that by giving each subscriber a return wire and specially
wound telephonic apparatus several important points are gained as for instance
firstly either a single wire or a metallic circuit may be used for communicating
with the central office or with subscribers of the same exchange secondly a
metallic circuit may be used for communicating with subscribers of a distant
exchange and thirdly a double wire between two exchanges may be used simul-
taneously by two subscribers and by an operator at each exchange. In the
latter case however differentially wound transmitters and receivers would be used
by the operators at the exchange offices as well as by the subscribers.
In the accompanying Drawings Figs. 1. 2 & 3. represent the combination of a
metallic circuit, two ground wires and differentially wound telephonic apparatus,
and Figures 45 and represent the combination of two metallic circuits with
differentially wound telephonic apparatus.
I premise that I do not limit myself to the particular construction of apparatus
represented in the drawings. In Figures 1. 2 & 3 B¹ and A¹ are duplex or
differentially wound telephone transmitters and B₁ and A¹¹ are duplex or
differentially wound telephone receivers. In Figure 1, B' is transmitting and
B is receiving, and in Figure 2, A¹ is transmitting and A" receiving. N° 1 and
N° 2 are the two wires of the metallic circuit and G and G¹ are ground wires.
The transmitters B¹ and A' are provided with a primary wire and with two
secondary coils on a soft iron core, while the receivers B1 and A" have two coils,
preferably on a soft iron core magnetized by a permanent magnet.
The coils a, a¹ a¹¹ and all are in circuit with N° 1 wire, while the coils b, b¹ b¹¹
and bare in circuit with N° 2 wire. The coils p and p¹ are primary coils and
are in circuit with a local battery L. B. and a microphone M. Following No 1 wire
from the point c, in the direction of the arrows from left to right, it will be seen
that the wire enters the coil a, by the outside terminal marked +, and makes its
exit by the inside terminal marked ; the connection is the same with a¹ all
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and all; and on tracing the connection of the wire No 2 from the point o' to o, it'
will be seen that the coils 611 and b, are connected from the outside to the inside
(to) while the coils 61 and 61, on the contrary, are connected from the
inside to the outside, (- to +)-Referring to Figure 1, it will be seen that upon
operating the microphone M, the soft iron core will generate secondary currents
in the coils, a and b, presumably of equal strength; and as the outside or + wire
of coil a, is connected with the inside or wire of coil b, and on corresponding
ends, the current from a, will reinforce the current from b, and a current will be
generated in the metallic circuit in the direction indicated by the arrows: The
current in No 1 wire, moving in one direction and the current in No 2 wire
moving in the opposite direction. It will also be seen that from the peculiarity of
the connection of the coils at A¹ and A¹¹ the currents in coil a¹ will neutralize the
currents in 61, and the currents in coil all will neutralize the currents in 6111;
whereas, on the contrary, the currents in coils all and b¹¹, will reinforce each other.
Hence, the receiver B₁ will respond to the transmitter B¹, while the receiver A"
will be neutral thereto.
"
Again, reference being made to Figure 2, it will be seen that by operating the
microphone M, independent secondary currents will be generated in coils a¹ and 61
and will move toward the point c, on, wires 1 and 2 and in the same direction, as
indicated by the arrows. At the point c, these currents meet, and were it not for
the ground wire G, they would neutralize each other, whereas, on the contrary
they reinforce each other on wire G, and proceed to "ground" and from "ground
to G and to c', where they redivide and return to a¹ and b¹ by the wires 1 and 2.
As the coils all and 6'11 are similarly connected and the currents traverse the
two wires in the same direction, receiver A will respond, and as the coils a¹
and bare similarly connected the receiver A¹, will also respond on the contrary,
as the coils B¹ and B", are dissimilarly connected these receivers will remain
neutral. Hence when B¹ transmits to B", A¹ and A" are neutral; and when A¹
transmits to A¹¹, B¹ and B¹¹ are neutral. In the former case the currents traverse
the two wires of the metallic circuit in opposite directions, and, in the latter case,
the currents move on the two wires in the same direction, the circuit being
completed by means of the ground or by a return wire. It is to be understood of
course that the transmitters need not necessarily be of the form represented at B¹
and A'. It will be obvious also that an ordinary transmitter inserted in wire G,
would operate the receivers A¹ and A' in a manner similar to that of transmitter M.
In Figure 3 is represented another form of duplex transmitter. Mis a microphone
which operates the two induction coils a and b, the former being in circuit with
N° 1 wire, and the latter with N° 2 wire.
The two primary coils p³, p³, are connected with a local battery L. B. and
microphone M and may be connected either in series or in multiple are. By keeping
the connections of the primary coils and the connections of one of the secondary
coils permanent, it is obvious that the direction of the currents by the two
secondary coils combined, will depend upon the manner in which the connections
of the other secondary coil is "connected up." Thus, the currents generated in
coil a would move to the left, and the currents in coil 6 would move to the right;
whereas, if the connections of say coil 6* were reversed, the currents from both
coils would then move to the left. In the former case receiver B¹ would respond
while receiver A¹ would be neutral, and in the latter case A¹ would respond
while B¹ would be neutral.
By this arrangement two operators may both receive and transmit independently
at each end of the line without interference. It will be seen that a current
generated in only one of the wires of the metallic circuit would divide at the
terminal points and a portion of the current would escape through the grounded
receiving instruments, when, however, the electric currents are generated in both
wires of the metallic circuits simultaneously as in the case where the two coils,
one in each circuit, are charged by one battery and one microphone, and the coils
are connected so as to reinforce each other, the tendency is for these currents to

page_text: circulate only in the metallic circuit, consequently there is little tendency for these
currents to escape to a grounded wire.
Hence, it will be obvious that two duplex transmitters and two duplex receivers
and a ground wire at each end of a metallic circuit can be connected in such a
manner (and as described), that two operators at one end may communicate with
two operators at the other end without interference.
In Figure 4, 1 and 2 are the two wires of a metallic circuit and 3 is a return
wire. By means of the switches S, and S¹, the two subscribers D, and D¹, may
either use a ground wire or a metallic circuit return wire at pleasure. To this end
the subscriber is supplied with either a special return wire to the telephone office
or with its practical equivalent such for instance as a common ungrounded wire
extending from the Central Office to the different subscribers in addition to the
grounded line of each subscriber. A, B, and A¹ B¹ represent the duplex or
differentially wound telephonic apparatus in the metallic circuit. In this arrange-
ment N° 3 return wire or trunk line may be used as a way" wire and
intermediate stations connected therewith as indicated at D1 and Di
In Figure 5 the arrangement is the same as in Figure 4 but the two wires Nos 3
and 4 are used as a common return wire. A, B, and A¹, B' are duplex telephonic
apparatus in N° 1 and N° 2 metallic circuit, and A* B* and A and B are duplex
apparatus in N° 3 and 4 metallic circuit.
"
In Figure 6 the branch line G, G, is also represented as being duplexed A'B'
representing duplex telephonic apparatus in said branch line. In this latter arrange-
ment it would be seen that with two metallic circuits, three operators and a subscriber
at each end of a line may communicate with each other simultaneously without
interference.
My invention is susceptible of a great variety of changes in detail of arrangement
by those skilled in the art, and without attempting to recite all those I have tried,
I wish it distinctly understood that I do not limit myself to the details of con-
struction or arrangement set forth above but intend to cover under this Patent all
well known equivalent means of carrying my Invention into effect.
Having now described and particularly ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is,
In a multiplex telephone system the combination substantially as herein setforth
with a metallic circuit including differentially wound telephone instruments of a
branch line connecting the ends of the metallic circuit and telephone instruments
located in said branch line.