Improvements in Apparatus or Devices for Switching or Diverting Electric Currents, more Especially Intended for use with Tele- phonic Circuits.
Year: 1889

page_text: Date of Application, 3rd June, 1889
Complete Specification Left, 3rd Mar., 1890-Accepted, 3rd May, 1890
PROVISIONAL SPECIFICATION.
Improvements in Apparatus or Devices for Switching or Diverting
Electric Currents, more Especially Intended for use with Tele-
phonic Circuits.
I, ALFRED GRAHAM of 109 Farringdon Road in the City of London, Electrician
do hereby declare the nature of this Invention to be as follows:-
My Invention has more especially for its object to provide an arrangement of
switching board and devices for telephonic circuits whereby they can be used for
switching or diverting the currents whatever the arrangement of the circuits may be,
that is, they can be used for instance for connecting up as desired double wire
circuits, single wire circuits or combinations of both double and single wire circuits
led to and from one switch board. According to my Invention the plugs which are
inserted into the orifices in the switch board are made with two conducting portions
the one insulated from the other. They are arranged in pairs and the corresponding
conducting portions of the plugs of each pair are connected together by means of
wires preferably arranged in one cable and passing through openings in a support on
the switch board on which support they rest when not in use the cable forming loops
below the support in which loops are suspended weights which keep the plugs in
position on the seat. One of each pair of these weights when in the lowest position
may pass between contact springs or pieces so that the said weight serves to complete
the circuit through the operators telephone at the central station where the switch
board is situated. The switch board is provided with a contact bracket and a contact
spring and annunciator for each line the bracket being electrically connected with a
metallic bushing in the orifices in the switch board into which the plugs are inserted.
When a plug is inserted into an orifice in the switch board the one conducting portion
of the said plug presses the spring out of contact with the bracket and makes contact
between the said spring and the said conducting portion of the plug the other con-
ducting portion of the plug making contact with the metallic bushing of the orifice.
The operator can thus communicate with any subscriber as the telephone at the central
station is connected to the wires leading from the two portions of the plugs. When
it is desired to establish communication between two subscribers the other plug of the
pair of plugs is inserted into the orifice appertaining to that subscribers circuit. The
circuits in the case of double wire circuits are arranged so that the one wire leads
through the annunciator and thence by the spring and bracket to the metal bushing
of the orifice and the other wire is attached to the said bushing and thence out to the
return wire. The single wire circuits are similarly arranged except that instead of
the second wire attached to the bushing there is a wire to earth which is in electrical
connection with the bushings of all the orifices.
I prefer to arrange the connections so that when the plugs are placed in the orifices
for conversation between subscribers those subscribers annunciators are cut out of
circuit and a single annunciator is placed in the circuit.
I have described the invention as applied to telephone circuits from which its
application to other analogous uses will also be understood.
Dated this 3rd day of June 1889.

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus or Devices for Switching or Diverting
Electric Currents, more Especially Intended for use with Tele-
phònic Circuits.
1 ALFRED GRAHAM of 109 Farringdon Road in the City of London Electrician 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 :-
My Invention has more especially for its object to provide an arrangement of
switching board and devices for telephonic circuits whereby they can be used for
switching or diverting the currents whatever the arrangement of the circuits may be
that is they can be used for instance for connecting up as desired double wire circuits
single wire circuits or combinations of both double and single wire circuits which may
be led to and from one switch board. According to my Invention the plugs which
are inserted into the orifices in the switch board are made with two conducting
portions c and d the one insulated from the other by the insulating material q as illus-
trated by Fig. 1 of the accompanying drawings which shews one of the plugs in
section resting in position on the support on the switch board whilst in Fig. 1 the
arrangement of cords and weights is diagramatically illustrated. The plugs are
arranged in pairs and the corresponding conducting portions of the plugs of each pair
are connected together by means of wires (e el el ell) preferably arranged in one
cable or cord and passing through openings in a support (X Fig. 14) on the
switch board on which support they rest as shewn when not in use the cable or
cord forming loops below the support in which loops are suspended weights (W_W¹)
which keep the plugs in position on the seat. One of each pair of these weights
when in the lowest position may pass between contact springs or pieces (F F¹)
so that the said weight serves to complete the circuit through the operators
telephone at the central station where the switch board is situated.
The switch board is provided with a contact bracket and a contact spring and
annunciator for each line the bracket being electrically connected with a metallic
'bushing in the orifices in the switch board into which the plugs are inserted.
Fig. 1 shews a section of the metallic bushing with the plug removed and Fig. 1º
with the plug inserted in one of the orifices in the switch board B being the
bushing 6 the spring and 6¹ the bracket. When a plug is inserted into an orifice in
the switch board the one conducting portion (d) of the said plug presses the
spring (b) out of contact with the bracket (61) and makes contact between the
said spring and the said conducting portion (d) of the plug the other conducting
portion (c) of the plug making contact with the metallic bushing (B) of the orifice.
The operator can thus communicate with any subscriber as the telephone at the
central station is connected to the wires leading from the 2 portions of the .plugs.
When it is desired to establish communication between two subscribers the other plug
of the pair of plugs is inserted into the orifice appertaining to that subscriber's
circuit. The circuits in the case of double wire circuits are arranged so that the one
wire leads through the annunciator and thence by the spring and bracket to the metal
bushing of the orifice and the other wire is attached to the said bushing and thence
out to the return wire. The single wire circuits are similarly arranged except that
instead of the second wire attached to the bushing.there is a wire to earth which is
in electrical connection with the bushing of all the orifices. I prefer to arrange the
connections so that when the plugs are placed in the orifices for conversation between
subscribers those subscribers annunciators are cut out of circuit and a single annun-
ciator is placed in the circuit.
The switchboard as described can be used where the double line plug hole con-
nections are connected to trunk wires and the single line plug holes are connected by
wires to plug holes on the ordinary exchange switchboard.
"

page_text: In this case the single line plug holes are provided with tablets or numbers corre-
sponding to the part or section of the board it is in connection with.
The operator on receiving a call on a double circuit line calls up the particular
section of exchange board by placing the plug in the corresponding single line plug
hole in connection with the section of the switch board to which the required sub-
scribers line is connected the operator at this section of the board makes the necessary
connection between the subscribers and this plug hole.
And in order that my said Invention may be perfectly understood I will more
particularly describe it with reference to the several diagrams of the accompanying
drawings the same letters and figures of reference indicating corresponding parts in
all the Figures.
Figure 1. is a diagram showing one mode of making the connections according to
my Invention.
Figures 2. 3. 4 and 5 are diagrams shewing the connections so that when the plugs
are placed in the orifices for conversation between subscribers those subscribers
annunciators are cut out of circuit and a single annunciator is placed in the circuit
made in accordance with my Invention.
Figure 6 shews a switchboard with double or metallic circuits and single line
circuits combined.
Figure 7 shews a combined switchboard which is used in conjunction with an
ordinary single line circuit switchboard to connect any subscriber on the exchange
system with trunk or double circuit lines.
In Figure 1. a. a¹ represent the two terminal connectors for the double line or
trunk wires A the annunciator in connection therewith B the plug hole provided
with a metal bushing, the line spring and the metal angle piece on which the
spring
rests when not in use as herein before described.
The terminals al and all are used for connecting the single circuit line wire or
the wire which is connected to the ordinary single line circuit switchboard A¹ is the
annunciator B¹ the plug hole with metal bushing is the line spring and ba
metal angle piece on which the spring brests. c. c¹ are the outer metal casings of
the plugs used for making the connections with the plug holes or metal bushings B
and B' d and d' are the central pins of the plugs used for making connection with
the line springs band b¹ W, W shew the weights attached to the cords e. e¹ and
elle Fare metal springs between and in contact with which the weight Wis
situated when the plug is not in use G is a circuit closing key; H is the generator
or battery and I is the operators telephone.
When a call is received on the annunciator A the operator in order to answer the
call takes the plug c¹ and places it in the hole B the circuit is then made with the
line wire to terminal a to annunciator drop A line spring 6 middle part of plug d¹
cord espring F' weight W spring F to the operators key G and telephone I or
when the key G is depressed with the generator H the outer metal casing of the
plug c and thence to the metal bushing B terminal a¹ and return wire. Should the
operator wish to call a subscriber the connections are made in the same way as that
described with the double line circuit but when the call or answer is made on the
single line circuit the connection passes to earth at the terminal a¹¹. The operator.
after answering the call takes the same plug 'c' and places it in the orifice in con-
nection with the subscriber of the number required. After a reply is received the
operator takes the plug c and puts it in the plug orifice in connection with the sub-
scriber that first called. The connections are then as follows:-Line to terminal-a
annunciator A line spring centre of plug d cord e cord e¹¹ centre of plug d'line
spring annunciator A line terminal a¹¹ to line and through the teleplone at the
other end of this line to earth the return circuit being made with the earth plate J
terminal a plug hole bushing B₁ the outer metal casing of the plug c cord e¹¹
cord el plug outer metal casing of the plug c and plug hole bushing B to the ter-
minal a and thence along the return wire.
i
The operator withdraws the two plugs when the conversation is finished.
Figure 2 shews the connections arranged so that the line annunciator drops"
.«

page_text: are cut out of circuit and a single annunciator is placed in the circuit with the plugs
when they are in use; a a¹ are the terminals connected to the double metallic circuit
or trunk wires bline spring 6 metal angle piece on which the spring d rests
A annunciator drop B metal plug. bushing, the plug e in this plan is made of a
different colour to that of c¹ or they are formed or marked in some way to distinguish
them from each other the plug c being used for answering a call and the plug c¹
being used for calling up K K' are contact keys used for making contact with the
generator and operators telephone the key K having contact studs 00' and the
key K' contact studs p p also an upper contact stud 9 and a contact spring r insu-
lating material being interposed at z to prevent contact between the springs kand
contact and studs, L is a trigger or cam used for disconnecting the circuit from
the contact studs and 7" and the springs m m³n n'. T is the annunciator drop
which is placed in circuit by means of the plugs.
Figure 2 shews the connections and positions of the various parts when the switch
board is not in use the circuit on the double line or trunk wires being made to line
terminal a spring b metal angle piece bannunciator A terminal a¹ and to return
wire. On the single line circuit the connections are made from single line wire to
terminal a line spring 611 metal angle piece 6111 annunciator A¹ to terminal a to
earth plate or connection.
Figure 3 shows the plug c in position for answering a call on the double line circuit.
The connections are made as follows-a to b, centre of plug c and cord e to key K. In
this case the wire e is connected to the key spring m³ so that when either of the keys
are pressed on to the studs o and o¹ for ringing or speaking the circuit is completed
with the stud o' through the wire and generator or battery H or through the stud o
wire t¹ operators telephone I wire u stud l cord e¹ to outer metal casing of plug c
plug bushing B and to terminal a'. In this circuit there is now no annunciator
drop.
Figure 4 shews the method of calling with the plug c¹. The connections are as
follows: Fron the terminal all to line spring 61 centre pin of plug d¹ to cord e¹¹
and to key K' the operator then calls up by pressing the key on to the contact stud P¹
the circuit being completed through the generator or battery H wire u stud l¹ spring n
cordell to outer casing of plug c plug bushing B¹ to terminal a to earth plate or con-
nection. When the operator releases the key from the stud P' he waits for an answer
to his call which will be shewn by the annunciator drop T falling-the circuit
being made from the line terminal a to the key K' through the top contact
stud as last described and spring r studs annunciator drop T to spring n
stud and stud spring a wire ell to outer casing c¹ of plug-metal bushing B¹
to terminal a to the earth connection or plate J. When the annunciator drop T
falls the operator immediately moves the cam or trigger L down which disconnects
the contact springs m and n n from the studs, and at once connects together
the springs m and n and also the springs m¹ and n¹.
Figure 5. shews the connections thus made-A current enters by terminal a passes
to line spring & plug pin d, cord e contact key K to spring m¹ and spring n³ through
annunciator drop T studs spring r stud 9 key K cord el plug pin d' line spring 6"
terminal all to line wire, through the instrument at the other end of the line and to
earth and returns by way of the earth plate J terminal all metal plug bushing B¹ to
the plug casing ccord e spring n to spring m cord e¹ outer plug casing c metal plug
bushing B to the terminal a' and thence to the instrument at the other end of the
line.
It will be observed that the two annunciators are out of circuit aud one only is
now in circuit with the two lines. When conversation is finished the drop T falls-
the cam or trigger is moved to its upright position and the two plugs withdrawn and
the annunciator drop shutters replaced.
This method of connection is applicable to a single as well as double line circuit
system.
In figure 6 the combined switchboard is shewn the connections being made as
described in Figure 2.

page_text: Figure 7 shews a combined switchboard which is used in conjunction with an
ordinary single line circuit switchboard to connect any subscriber on the Exchange
system with trunk or double circuit lines.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
First. The arrangements for connecting double or metallic circuits with single
wire circuits substantially as hereinbefore described.
Second. In telephone or other electric circuits arrangement of connections and
switching appliances for operating substantially as and for the purposes herein-
before described and shewn in Fig. 1. of the accompanying drawings.
Third. In telephone or other electric circuits the arrangement of connections and
switching appliances for operating substantially as and for the purposes hereinbefore
described and illustrated in Figures 1 to 5 of the accompanying drawings.
Fourth. The combination of double circuit plug and orifice with parts in connection
therewith for making contact with the two conducting parts of the plug substantially
as and for the purpose hereinbefore described and illustrated.
Fifth. The combination with an ordinary exchange switch board of an additional
double and single wire switch board constructed and arranged substantially as and for
the purpose hereinbefore described with reference to Fig. 7 of the accompanying
drawings.
Datad this 3rd day of Norah EXUA
Laran
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W C., Agents.