Year: 1886

page_text: Date of Application, 13th Aug., 1886.
Complete Left, 8th June, 1887.
Complete Accepted, 22nd July, 1887.
I, JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of this Invention to be as follows:-
The object of this Invention is to increase the working capacity of and render more
efficient metallic telephone circuits in which either two or more telephone subscribers
or a telephone subscriber and a telephone operator at each end of a metallic circuit
may communicate with each other simultaneously.
This I accomplish by firstly connecting a branch line with each end of the metallic
circuit and connecting said branch line to either a ground wire or to a return wire
or wires and using differentially wound telephone apparatus in the metallic circuit
which may be done as described in the Specification of the application for Patent 4231
of 1886 dated 15th August 1885 and secondly by using a telephonic repeater and a
switching device at each end of the metallic circuit, and thirdly by using a con-
pensating device between parallel metallic circuits or between a metallic circuit and a
grounded circuit.
To explain the Invention I refer to the accompanying drawings.
In Figure 1 No. and No. 2 are the two wires of a metallic circuit at one of two
central stations and G is a branch line for grounding said metallic circuit, R is a
repeater arranged as a duplex or differential repeater, D and F are two subscribers
lines. Subscriber F is represented as being connected with the duplex repeater and
subscriber D with the branch line G while K and L represent the ordinary central
office telephone switch. I is a special switch for the branch line. G and J is a special
switch for the duplex repeater. The repeater is divided into two parts one on each
side of the branch line G the wire of one part p being connected with No. 1 wire
and the wire q on the other part being connected with No. 2 wire. The wires and
P
forming one side of the repeater are continuous with the metallic circuit 1 and 2
q

page_text: while the wires p' and q' forming the other side of the repeater are connected at
one end with the ground wire E and at the other end with the switch J.
The principle of a telephone repeater is well known. A simple form is that of
an induction coil with or without a soft iron core, the primary being in one electric
circuit and the secondary coil being in an independent electric circuit so that an
impulse generated'in one circuit will affect the other circuit by induction.
In the duplex repeater the subscribers line at each telephone office is brought
within the inductive influence of both branches of the metallic circuit No. 1 and
No. 2 in such a manner that the induction into and from the two branches shall
be equal. Any form of repeater may be used so long as the inductive action
between said repeater and the two branches of the metallic circuit, and on each
side of the branch line is equal, and so long as said repeater does not cause
retardation of the telephone current either by high resistance or by self induction.
I preferably construct the duplex repeater as follows-Referring to Figure 2 a
cable with two insulated wires is used, one wire p q being continuous with the
metallic circuit and the other p¹ ql with the subscriber's line.
No. 1 and No. 2 are the two wires of the metallic circuit connecting two central
offices each wire being continuous with one of the insulated wires of the repeating
cable, R is the repeater and p q are the repeating wires passing through the cables
and being continuous with the metallic circuit, while p¹ q' are the wires of the
cable which connect with the subscribers line. Figure 3 is an enlarged view of
the repeating cable.
By this arrangement when the transmitter at D, is used the current divides
equally and passes into the two branches of the metallic circuit No. 1 and No. 2 and
in so doing passes through the two sides of the repeater, which it affects by induction
but in opposite directions and the one side neutralizes the other and the subscriber
at F, does not overhear what is being said. When the subscriber at F is to be
placed in communication with another subscriber at the distant station the switches L
and J are connected with such subscribers line and the duplex repeater and the line
wires act as a metallic circuit as hereinbefore explained and repeat into the subscribers
line at the distant station, and when subscriber D, communicates with the subscriber
at the distant station the lines No. 1 and No. 2 act as a double conductor and thus the
two messages will not interfere with each other as already fully explained. Hence the
two subscribers at D and F may communicate with two subscribers at the distant
station by means of a metallic circuit without interference.
In case the line wires are not electrically balanced this may be compensated for in
the duplex repeaters by making the terminal cables or coils of unequal length or by
making them adjustable with relation to each other in a manner well understood.
Dated this 13th day of August 1886.

page_text: COMPLETE SPECIFICATION.
Improvements in Telephonic Systems and Apparatus.
I, JAMES YATE JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of this Invention which Invention has been
communicated to me from abroad by Abner Mulholland Rosebrugh of 121 Church
Street in the City of Toronto in the Province of Ontario Canada Surgeon and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The object of this Invention is to increase the working capacity of and render
more efficient metallic telephone circuits in which either two or more telephone
subscribers or a telephone subscriber and a telephone operator at each end of a
metallic circuit may communicate with each other simultaneously,
This I accomplish by firstly connecting a branch line with each end of the metallic
circuit and connecting said branch line to either a ground wire or to a return wire or
wires and using differentially wound telephone apparatus in the metallic circuit which
may be done as described in the Specification of the application for Patent 4231
of 1886 dated 15th August 1885 and secondly by using a telephonic repeater and a
switching device at each end of the metallic circuit and thirdly by using a
compensating device between parallel metallic circuits or between a metallic circuit
and a grounded circuit.
To explain the Invention I refer to the drawings accompanying my provisional
Specification.
In Figure 1 Number 1 and Number 2 are the two wires of a metallic circuit at one
of two central stations and G is a branch line for grounding said metallic circuit. R is
a repeater arranged as a duplex or differential repeater, D and F are two subscribers
lines. Subscriber F is represented as being connected with the duplex repeater and
subscriber D with the branch line G while K and L represent the ordinary central
office telephone switch. I is a special switch for the branch line G and J is a special
switch for the duplex repeater. The repeater is divided into two parts one on each
side of the branch line G the wire of one part p being connected with Number 1
wire and the wire q on the other part being connected with Number 2 wire. The
wires and q forming one side of the repeater are continuous with the metallic
circuit 1 and 2 while the wires p¹ and q forming the other side of the repeater are
connected at one end with the ground wire E and at the other end with the switch J.
The principle of a telephone repeater is well known. A simple form is that of
an induction coil with or without a soft iron core, the primary being in one electric
circuit and the secondary coil being in an independent electric circuit so that an
impulse generated in one circuit will affect the other circuit by induction.
In the duplex repeater the subscribers line at each telephone office is brought
within the inductive influence of both branches of the metallic circuit Number 1 and
Number 2 in such a manner that the induction in to and from the two branches shall

page_text: be equal. Any form of repeater may be used so long as the inductive action between
said repeater and the two branches of the metallic circuit and on each side of the
branch line is equal, and so long as said repeater does not cause retardation of the
telephone current either by high resistance or by self induction.
I preferably construct the duplex repeater as follows. Referring to Figure 2 a
cable with two insulated wires is used, one wire p q being continuous with the metallic
circuit and the other p³ q¹ with the subscribers line.
Number 1 and number 2 are the two wires of the metallic circuit connecting two
central offices each wire being continuous with one of the insulated wires of the
repeating cable. R is the repeater and p q are the repeating wires passing through
the cables and being continuous with the metallic circuit while p¹ q' are the wires of
the cable which connect with the subscribers line. Figure 3 is an enlarged view of
the repeating cable.
By this arrangement when the transmitter at D is used the current divides equally
and passes into the two branches of the metallic circuit Number 1 and Number 2 and
in so doing passes through the two sides of the repeater which it affects by induction
but in opposite directions and the one side neutralizes the other and the subscriber at F
does not overhear what is being said. When the subscriber at F is to be placed in
cominunication with another subscriber at the distant station the switches L and J are
connected with such subscribers line and the duplex repeater and the line wires act as
a metallic circuit as hereinbefore explained and repeat into the subscribers lines at
the distant station and when subscriber D cominunicates with the subscriber at the
distant station the lines Number 1 and Number 2 act as a double conductor and thus
the two messages will not interfere with each other as already fully explained. Hence
the two subscribers at D and F may communicate with two subscribers at the distant
station by means of a metallic circuit without interference.
In case the line wires are not electrically balanced this may be compensated for in
the duplex repeaters by making the terminal cables or coils of unequal length or by
inaking them adjustable with relation to each other in a manner well understood.
Having now particularly described and ascertained the nature of my said Invention
and in what manner the same, is to be performed I declare that what I claim is :-
First In metallic telephone circuits the combination of a branch line differentially
wound telephone apparatus, a telephonic repeater and switching device at each end of
the circuit and a compensating device substantially as hereinbefore described.
Second: In telephones the arrangement illustrated in and described with reference
to Figure 1 of the accompanying drawings.
Third: In or for telephones the arrangement of duplex repeater as illustrated in
and described with reference to Figures 2 & 3 of the accompanying drawings.
Dated this 7th day of June 1887.