IMPROVEMENTS IN CIRCUITS FOR ELECTRICAL APPARATUS
Year: 1883

page_text: "
LETTERS PATENT to Herbert John Allison, of the firm of Allison Brothers,
Patent Agents, of Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN CIRCUITS FOR ELECTRICAL APPARATUS communicated to
him from abroad by Charles Elmer Allen, of Adams, Massachusetts, United
States of America, Electrician,
PROVISIONAL SPECIFICATION left by the said Herbert John Allison at the
Office of the Commissioners of Patents on the 18th December 1883.
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents, of
Southampton Buildings, London, "IMPROVEMENTS IN CIRCUITS FOR ELECTRICAL
APPARATUS," a communication to me from abroad by Charles Elmer Allen, of
Adams, Massachusetts, United States of America, Electrician,
My present invention is an improvement in circuits for electrical apparatus.
It consists, essentially, of a main line circuit arranged with reference to central.
offices of an extended exchange system, which offices have each several local circuits
branching therefrom and returning thereto, in which are several subscribers'
instruments arranged in such a way that a circuit may be made up from ground of
any one individual station or any local in any central office of any exchange to the
ground of any desired individual station of any line in any of the central offices,.
from parts of return portions of said locals and main line in which telephones and
transmitters of the stations may be thrown in for conversation, the leading portions
(in which are controlling magnets of the signalling devices) being temporarily cut
off from their return portions thereby relieving the circuit to be talked through of
such resistance.
I have been for some time engaged in experimenting upon the present system of
telephoning and have succeeded in producing a telephone exchange system
consisting of an automatic central office and certain improvements in signal boxes
so constructed and located, with reference to a system of circuits, that in their use
any subscriber in the exchange can by the manipulation of his signal box, ring the
bell of any other subscriber and place himself in independent telephonic connection'

page_text: with him without the aid of any one at the central office and without ringing the
bells of other subscribers.
The system referred to is not limited in its results to a single exchange and the
offices and subscribers associated there with but it is calculated to embrace two or
more exchanges located upon a main line circuit so that an individual subscriber in
any of the exchanges may signal and communicate with any other subscriber in
his or any other exchange connected with main line, secretly and independently
of all stations except the two intended to be engaged.
To make the connections at the central offices I employ the ordinary cross-bar-
plug-switch boards but in a future patent I propose to secure an automatic central
office machine to be used in lieu of the said switch-boards.
At the initial central office is a heavy battery for the main line, one side of
which is grounded and the circuit from the other side runs through a relay, switch,
bar, and main line wire out thence to a main line of another office, through a relay,
switch, switch bar, main line wire and on to main line wire connected to another
office, thence through relay at the terminal central office, switch, and bar to a main
line return wire, thence to main line return wire of the intermediate station and
thence to main line return wire of the initial or starting station, terminating on a
bar of the switch-board at said station and leaving the main line normally open.
A bar of the switch-board of the initial station is in connection with the earth
through a wire, a switch, secondary of induction coil in transmitter and telephone.
Certain bars in the intermediate and terminal central office switch-boards are in
connection with the return of main line by suitable branches.
From the remaining perpendicular bars of each central office switch-board local
circuits extend, one each of which takes in several subscribers' stations, and
returning each of said circuits occupies two bars of the switch-board, the exit
wires being connected to local batteries. The wires not connected to batteries
constitute the return wires of the circuit.
All of the local circuits are similar and one of them starting and terminating
with a central office may be described as follows:-One pole of a battery, which has
its opposite pole grounded, runs through an annunciator, a switch and a bar to the
local line wire which takes in switches and relay magnets of several local stations
and then returns to its central office terminating on a bar and leaving said local
circuit normally open. In its return the said local circuit passes through the said
local circuits in an opposite direction, at any of which it may be grounded through a
branch circuit by pressing a spring key which is also normally open or through the
secondary of transmitter and telephone by closing a switch which is also normally
open. I employ a relay at the local stations, the lever of which, when a current is
passed through the controlling magnet closes the bell circuit in which a battery is
located causing a bell to ring.
All the plugs of the switch-board except one are located ready for use, in the
lowest horizontal row of holes. The bar to which this plug belongs is normally
plugged at its intersection with a corresponding horizontal bar.
Now let us suppose a subscriber, say C', of the terminal exchange wants a
subscriber C³ of the intermediate exchange. The subscriber at O' first signals the
terminal central office by pressing the proper key at his station which completes
the circuit of a battery causing the tag of the annunciator to drop. He now opens
the switch at his station to open the exit portion of the line, closes another switch
which completes the battery circuit at C¹ through the primary wire of the
transmitter, then closes another switch to ground the return of circuit of the line
last mentioned, through the secondary of transmitter and telephone and then puts
the telephone to his ear. As soon as tag of annunciater drops the operator at the
terminal central office opens a switch and removes a pin in a bar to the next hole
above putting the said bar in connection with other bars, and ground through the
transmitter and telephone of said central office thereby putting said transmitter and
telephone in circuit with those of station C¹ through a portion of the return
circuit. The operator at the terminal central office now signals or calls the

page_text: individual at station C¹ and the latter responds telling him whom he wants to
communicate with. The operator at said terminal central office now removes the
plug from one bar to the next bole above and plugs it in connection with a
horizontal bar and then opens the switch of central transmitter and removes the
plug from bar to the next hole above and plugs it in connection with the horizontal
bar having the proper electrical connections for the end in view. The desired
intermediate central office is now signalled by pressing a key at the terminal
central office. It will be seen that by pressing this key the bells of the several
central offices will be caused to ring by giving ground to the return portions of the
main line circuit, which completes the circuit of the main line battery through the
bell relays.
Each central office has a certain signal ascribed to it, say for instance the signal
for the initial central office is one ring, for intermediate two rings, and for terminal
three rings.
The operator at the terminal central office gives the intermediate office signal by
pressing the key the proper number of times. As soon as the operator at the
intermediate central office bears his signal he opens a switch to open the leading
portion of the main line circuit. He then removes the plug from the lower hole in
the upright bar to the next hole above and plugs said bar into connection. The
branch circuit of the return portion of the main line is now in connection with the
earth at the intermediate central office through the secondary of transmitter and
telephone. As soon as the operator at the terminal central office signals the
operator at the intermediate central office, he, the former, closes and opens the
proper switches and plugs bis bar in the manner just described for the intermediate
central office and then the two central offices are in connection with each other
through their branch circuits and a portion of the return main line circuit. The
operator at the terminal central office now tells the operator at the intermediate
central office to get C. The latter operator opens the switch and removes and.
changes the position of the plugs and signals C by pushing the key the proper
number of times to sound the C³ signal. C' now hearing his signal opens receiving
switch and closes the transmitter switches and listens through the telephone. He
then responds to the operator's call, the latter informs him that he is wanted and
properly plugs his switch-board to make connection between C and C¹ who can
then converse. Their circuits are as follows:-From ground at C' through the
telephone and transmitter of said station, switch, to return portion of local line,
through terminal central office and return portion of main line to and through
intermediate central office and return portion of local line to the instruments of Č³,
and through them to ground. All the relays, signalling magnets and batteries are
cut out of the circuit while conversation is being held, said apparatus lying in the
lead portions of the circuits. It is evident that the circuit is thus freed of much
resistance.
The transmitters and telephones may be arranged according to any of the usual
methods so as to be looped in to the return portion of the main line circuit for the
purpose of interviewing parties who are connected to ascertain when they have
finished talking or for the purpose of giving instructions.
It may be observed that the return portions of the local circuits instead of
returning through the several subscribers' instruments may be so run as to return
direct to the central office from which they started and have branches extending
from them to the several subscribers' instruments and ground may be given to the
return at any station by grounding the branch either through the press key or
through the telephone and transmitter.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Herbert John Allison in the Patent Office on the 18th June 1884.
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents, of
Southampton Buildings, London, "IMPROVEMENTS IN CIRCUITS FOR ELECTRICAL
APPARATUS," a communication to me from abroad by Charles Elmer Allen, of
Adams, Massachusetts, United States of America, Electrician,
My present invention is an improvement in circuits for electrical apparatus.
It consists, essentially, of a main line circuit arranged with reference to the central
offices of an extended exchange system, which offices have each several local
circuits branching therefrom and returning thereto, in which are several subscribers'
instruments, arranged in such a way that a circuit may be made up from ground
of any one individual station or any local in any central office of any exchange to
the ground of any desired individual station of any line in any of the central
offices from parts of return portions of said locals and main line in which telephones
and transmitters of the stations may be thrown in for conversation, the leading
portions (in which are controlling magnets of signalling devices) being temporarily
cut off from their return portions thereby relieving the circuit to be talked through
of such resistance.
I have been for some time engaged in experimenting upon the present system
of telephoning and have succeeded in producing a telephone exchange system
consisting of an automatic central office and certain improvements in signal boxes
so constructed and located, with reference to a system of circuits, that in their
use any subscriber in the exchange can by the manipulation of his signal box,
ring the bell of any other subscriber and place himself in independent telephonic
connection with him without the aid of any one at the central office and without
ringing the bells of any other subscribers.
The system referred to is not limited in its results to a single exchange and the
offices and subscribers associated therewith but it is calculated to embrace two or
more exchanges located upon a main line circuit, so that an individual subscriber
in any of the exchanges, may signal and communicate with any other subscriber
in his or any other exchange connected with said main line, secretly and
independently of all stations except the two intended to be engaged.
As this application relates to the system of circuits in which my central office
machines and signal boxes are to be placed, I have omitted to show or describe
said apparatus at this time, but in order to illustrate the subject of the present
claims, I have shown in my several diagrams the ordinary cross-bar-plug-switch-
boards and the ordinary switch connections and at each individual station I have
represented the ordinary electric vibrating bell and the well known hand switches
and press keys.
In my drawings I show switch boards, several individual stations and their
relation to the circuits which form the subject of this application.
Referring to the drawings we may understand for purposes of illustration that
the three exchanges represented by the capitals W BP are respectively Washington,
Baltimore and Philadelphia.
At the Washington central office is a heavy battery A. for the main line, one
side of which is grounded and the circuit from the other side runs through relay e³,
switch 6, bar 2, main line wire, out thence to main line wire on Figure 2,
through relay e switch b switch bar 2b, main line wire and on to main line
shown in Figure 3, thence through relay e¹ at "P" central office, switch 68, bar 2°
main line return wire; thence to main line return wire of Figure 2 and thence to
main line return wire of Figure 1, terminating on bar 3ª leaving the main line
normally open,

page_text: Bar 1 of the "W" switch board is in connection with the earth through
wire a, switch c, secondary of induction coil in transmitter 6 and telephone H.
Bars 3b and 3° in the "B" and "P" centrals are in connection with the return
main line by branches 8 8¹.
From the remaining perpendicular bars of each central office switch board, local
circuits extend, one each of which takes in several subscribers' stations, and
returning each of said circuits occupies two bars of the switch board as shown,
the exit wires being connected to local batteries. The wires not connected to
batteries are the return wires of the circuits.
All of the local circuits are similar and one of them starting and terminating
with a central office may be described as follows:-One pole of battery A' which
has its opposite pole grounded, runs through annunciator a switch be, bar 4ª, to
local line wire E, which takes in switches c relay magnets m, of stations C4 C5
and then returns to central office "W" terminating on bar 5*, leaving said local
circuit normally open.
In its return the said local circuit passes through
stations C5 C at either of which it may be grounded through a branch circuit f
by pressing the spring key c³, which is also normally open, or through the secondary
of transmitter T and telephone H by closing switch c which is also normally open.
R is a relay the lever of which, when a current is sent through magnet m closes
the bell circuit in which battery A' is located, causing the bell I to ring.
All the plugs of the switch board except that of bar 1ª are located ready for
use in the lowest horizontal row of holes. Bar 1ª is normally plugged at its
intersection with its corresponding horizontal bar 1**.
Now let us suppose a subscriber, say 017, of the "P" exchange, wants a
subscriber, C, of the "B" exchange. The subscriber at C₁7 first signals the
central office "P" by pressing the key c³ at said station which completes the
circuit of battery A7, causing the tag of annunciator a to drop. He now opens
switch c at his station to open the exit portion of the line L*; closes the switch c
which completes the battery circuit at C" through the primary wire of the
transmitter, then closes switch c² to ground the return of circuit L' through the
secondary of transmitter and telephone and then puts the telephone to his ear.
As soon as the tag of the annunciator a drops, the operator at central office "P"
opens switch 60 and removes the pin in bar 5° to the next hole above putting it
in connection with horizontal and perpendicular bars 1cx 1°, and ground through
the transmitter and telephone of said central office, thereby putting said transmitter
and telephone in circuit with those of station C7 through a portion of the return
circuit L. The operator of central office "P" now calls to the individual at
station C7 and the latter responds telling whom he wants to cominunicate with.
The operator at the central office "P" now removes the plug from the bar 5° to
the next hole above and plugs it in connection with horizontal bar 2* and then
opens switch c' of the central transmitter and removes plug from bar 3° to next
hole above and plugs it in connection with horizontal bar 1°.
The desired central office "B" is now signalled by pressing the key d of central
office "P." It will be seen that by pressing this key the bells of the several
central offices will be caused to ring by giving ground to the return portions of
the inain line circuit which completes the circuit of the main line battery A
through the bell relays.
Each central office bas a certain signal ascribed to it, say for instance the signal
for "W" is one ring, for "B" two rings and for "P" three rings.
The operator at "P" gives the "B" signal by pressing his key a proper number
of times. As soon as the operator at "B" central office hears his signal he opens
bis switch b to open the leading portion of the main line circuit. He then removes
the pin from the lower hole in upright bar 3b to the next hole above and plugs
bar 3b into connection with bar 1x. The brauch circuit of return portion of the
main line is now in connection with the earth at central office " "B" through
secondary of transmitter T and telephone H. As soon as the operator at "P"
signals "B," he, the "P" central office operator, closes his switches c, opens his

page_text: switch 6 and plugs his bar in the manner just described for central office "B," and
then the two central offices are in circuit with each other through their branch
circuits and a portion of the return main line circuit. The operator at "P" now
tells the operator at "B" to get C".
"B" central office operator opens switch c¹ removes plug in bar 3b one hole
higher and removes plug from bottom hole in the bar 5b to the bar 1bx and
signals C by pushing key d at the "B" central station, the proper number of
times to sound the C signal. Pushing the key d, the proper number of times,
gives the proper signal for station C. by giving ground to return of said circuit.
C" now hearing his signal opens switch c and closes the transmitter
switches c¹ c² and listens through the telephone. He then responds to operator
at "B" central office and the latter informs him that he is wanted and removes the
plug in bar 5b to the hole above and plugs bar 5b in connection with the same
horizontal bar 2bx that he plugged bar 3b with. Subscribers or individuals at C¹¹
and C are now in communication with each other their circuits being as follows:-
From ground at C17 station through the telephone and transmitter of said station,
switch to return portion of local line L. The lead portion of this line having
been opened by the opening of switch c, the circuit is necessarily through the
return portion of bar 5° at central office "P;" through a portion of the horizontal
bar 2x into perpendicular bar 3 through branch s¹ of "P" central office, to return
portion of main line, through this into branch 8 of the "B" central office,
perpendicular bar 3b, through a portion of horizontal bar 2bx into perpendicular
bar 5b, return of local circuit L to station C¹¹; through switch c² of C1 subscriber,
his transmitter and telephone to ground. It will thus be seen that all of the relays,
signalling magnets and batteries are cut out of the circuit while conversation is
passing between two stations. By this arrangement the line is freed of much of
the resistance which would tend otherwise to interfere with conversation between
any two points of communication.
Transmitters and telephones as represented may be arranged according to any
of the usual methods so as to be looped into the return portion of the main line
circuit for the purpose of interviewing parties who are connected to ascertain when
they have finished talking or for the purpose of giving instructions.
It may be observed that the return portions of the local circuits instead of
returning through the several subscribers' instruments, may be run so as to return
direct to the central office from which they started, and have branches extending
from them to the several subscribers' instruments, and ground may be given to the
return at any station by grounding the branch either through the press key or
through the telephone and transmitter.
Having thus described my invention what I claim as new is :-
1. The main line circuit starting from one pole of a main line battery (the other
pole being grounded) and running so as to take in several central offices on going
out and returning to the same central from which it started in such a way that the
return portion may be grounded at any of the central offices and the end terminating
at the said central office from which it started in such a way as to leave the said
battery circuit open until closed by giving ground to the return portion of said
circuit as and for the purpose set forth.
2. A circuit starting at one pole of a battery (of which the other pole is grounded
at the central office) and running through the controlling magnets of several
subscribers' instruments but in such a way that said return portion of circuit may
be grounded at each subscribers' station and the end at the central office terminating
so as to leave the local circuit open until ground is given to the return wire through
branches at subscribers' stations or by grounding the terminating end of the return
wire at the central office as and for the purpose specified.
3. The combination with the main line circuit of several central offices each
having several local circuits branching therefrom and returning thereto (on which
are situated several subscribers' instruments) arranged in such a manner that a
circuit may be made up from any ground at any one individual station of any local

page_text: line in any of the exchanges, from parts of return portions of said local and main
line in which the telephone and transmitter of the station. may be thrown in for
conversation, the lead portions, in which are the controlling magnets of the signalling
devices, being temporarily cut off from their return portions, thereby relieving the
circuit to be talked through of much resistance.
4. A battery or generator with one of its poles grounded and the circuit from the
other forming a loop (not grounded) upon which are situated several stations each
with its signalling or controlling magnets situated in the leading portion of the
loop and provided with suitable means for opening and closing said portion of
loop circuit, and with suitable devices for giving ground to the return portions of
the loop either directly or through communicating instruments, as and for the
purpose set forth.
5. One or more generators and main line loop circuits arranged as described, their
stations being central offices, at each of which are situated several other generators
with loop circuits and stations extending therefrom, and means at each central
office and station by which a circuit may be made up from parts of return
portions of the main line loop circuit and any of the local loop circuits, substantially
as set forth.
In witness whereof, I, the said Herbert John Allison, have hereunto set my hand
and seal, this eighteenth day of June, in the year of our Lord one thousand eight
hundred and eighty-four
HERBERT. J. ALLISON (L.S.)