Improvements in Telephone Switchboards or Switching Apparatus for Telephone Stations.
Year: 1898

page_text: Date of Application, 16th Dec., 1898-Accepted, 18th Mar., 1899
:
COMPLETE SPECIFICATION.
Improvements in Telephone Switchboards or Switching Apparatus
for Telephone Stations.
A communication by THOMAS F. AHERN, of the City of Detroit, in the County
of Wayne and State of Michigan, United States of America, Electrical
Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both
in the County of Lancaster, 118, New Street, Birmingham, in the County of
Warwick, and 322, High Holborn, in the County of Middlesex, Civil Engineer,
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: —
This machine relates to telephone switchboards, or switching apparatus for
telephone stations, and has for its object a division of labour on the switchboard,
so that the work of the operators is very much simplified, the liability of errors
very much decreased, and a construction of switchboard permitted which will
accommodate a much larger number of subscribers than those ordinarily in use.
It consists in improved means for connecting any two subscribers' lines for con-
versation, to make the "busy test" by the operator for answering the subscriber's
call, and in having the subscriber's call transferred from the operator at one
division of the switchboard to the operator at another division of the switchboard,
who connects with the called subscriber; also, in improved means for discon-
necting and ringing off when subscribers are through talking. It also consists
in various other combinations, all of which are hereinafter specified and claimed.
The system hereinafter described is designated as a duplex switchboard system,
and its general features consist of two separate series or banks of jacks, one of
which is termed the answering division, and the other the connecting division.
Each subscriber's line enters the board and terminates in a pair of jacks one in
each section of the board. There is also a local jack in each section corresponding
to each subscriber, such pair of local jacks being connected by trunk lines. In
addition thereto there are annunciators in each division peculiar to each sub-
scriber's line; so that in each division each subscriber has a terminal jack to his
line-a local jack and an annunciator with appropriate switches, connections, and
wiring, all as hereinafter more fully described.
There have heretofore been attempts to divide the labour between operators, one
set answering calls and another set connecting called subscribers; but in none of
these has the necessity of using common, independent, line-connecting, speaking
telephones between the operators on each of these divisions been avoided. By
this apparatus the operator is enabled on the answering division not only to
attract the attention of the operator on the connecting division, but to indicate to
such operator by one and the same signal the subscriber called for.
In the drawings,

page_text: Figures 1 and 2, Sheets 1 and 2, taken together, constitute a diagrammatic view
of the two divisions of this improved switchboard, together with the connections,
the two lines being placed as though they were joined at the right hand of Sheet 1
and at the left hand of Sheet 2, and the figures being enlarged for purposes of
clearness and convenience. Figure 1 represents the spring jacks of the answering
division," and Figure the spring jacks of the "connecting division."
Figure 3 is a detailed sectional view of an elastic plug, and so much of a spring
jack as shows its operation.
"
Figure 4 shows the same plug in a slightly different position in the spring
jack from that of Figure 3.
Figures 5 and Gare enlarged views of the relays and annunciators upon the con-
necting division of the board. In these figures no attempt has been made to show
their mechanical construction, only so far as is necessary to indicate the mode of
operation.
Figures 7 and 8, taken together, illustrate the application of the invention in
a switchboard embodying several sections.
Similar letters refer to similar parts.
In the drawings, Figures 1 and 2, illustration is made of only so much of the
switchboard and its sections as would indicate the common lines, trunk lines, and
the lines of one calling and one called subscriber, with sufficient duplication to s
illustrate this invention and its mode of operation with any number of sub-
scribers, as it will be understood that the apparatus can be expanded by duplica-
tion to any assignable degree. No attempt is made to show specific features of
mechanical construction which are common to all switchboards, annunciators,
telephones, etc., as they do not in themselves constitute any portion of this inven- 2
tion, and the detail construction of these elements is fully understood by
electricians.
In the drawings, T (Fig. 1) represents the telephone set of the calling sub-
scriber, and T (Fig. 2) the telephone set of the called subscriber. T2 is a
telephone of the receiving operator on the answering division, by means of which
she communicates with the calling subscriber. T is a transmitter on a local
battery circuit, of which L is the local battery in which a primary coil P actuates
the secondary of an induction coil P₁ in the circuit of the operator's telephone in
the usual manner, the whole constituting what is commonly known as the
operator's set. L, in Figure 2, is a common generating battery, yielding power to 3
a common line L².
In Figure 1, 1 and 2 represent answering jacks upon the answering division,
connected (as will be seen by tracing the lines to the subscriber's set) on a metallic
circuit. 3 and 4 are local spring jacks, also located upon the answering division,
and, as will hereinafter be described, constitute the switching means by which
connection is made with the connecting division.
The answering division of the switchboard, therefore, is comprised of two series
of jacks, and those called "answering jacks" communicating with the subscriber's
line, and those called "local jacks" communicating with the other division of the
switchboard. 5 and 6 are spring jacks on the connecting division, and also form 4
terminals of lines from the subscriber's set, corresponding in this division to the
spring jacks 2 and 1 in the answering division. 7 and 8 are local jacks in the
connecting division, corresponding with the local jacks 4 and 3 in the answering
division. It will be noted that all of these jacks are connected between the
answering and the connecting divisions by the lines represented. It is 5
preferred not to give designating numbers or letters to the lines, but to describe
them by letter by reference to circuits, and as the circuits may vary through the
same line, the line might be designated by different letters. By following the
same letters through circuits, any particular circuit can be understood.
In the answering division, it will be noted that the calling subscriber's set T 5;
ends in the answering jack 1, and the called subscriber's set T ends in the
answering jack 2.

page_text: A and A¹ are annunciators placed in the circuit of each subscriber's line
respectively, and located upon the answering division of the switchboard. A³
and A3 are diagrammatic views of drop annunciators, called local annunciators,
in the circuit between the two divisions, and indicated upon the connecting
division of the board.
In Figure 1, on the answering division, B is the answering plug; B₁ the local
connecting plug. The answering plug B is constructed as shown in Figures 3
and 4, and will be hereinafter described. There is, however, nothing new about
the plug in itself. Double lines connect the two plugs B and B₁, which form at
times parts of different circuits, to be hereinafter described. One line connects
the tip of the plug with the collar of its companion; the other line connects the
collar of the first plug with the tip of its companion; it being understood that the
collars and tips are insulated, and are adapted to make contacts in the usual
manner in the spring jacks. In one of the lines connecting the two plugs is a
test relay B2, which is of the usual construction, and actuates an armature B³.
By means of this test relay, the operator's set is thrown in in parallel with a
circuit to be hereinafter described, and enables the operator's telephone to transmit
the "busy test" to the operator in a manner to be hereinafter described. B' is a
local calling plug, and B a local connecting plug, upon the connecting division.
These plugs are also connected by double lines from the tip of one to the collar
of the other, and vice versa. A is a relay, located in line with a local drop
annunciator A³. A is a corresponding relay located in line with the local drop A
A and A are galvanometer indicators, connected and operating as described.
L' is an independent local common battery to energize the connecting lines of a
local portion of the two divisions of the switchboard. The solid lines between
the parts specified indicate connecting wiring. Lines which have no terminals
simply indicate continuations and duplications of the like parts of the switchboard.
In Figures 3 and 4, 1 indicates a spring jack; 1" the frame holding the same;
1b a sectional view of the plug inserted in the spring jack in Figure 3, and an
outline view of a slightly different position when it is so inserted in Figure 4.
1 is the tip of the plug forming a metallic contact with the lower spring 15; the
black portions 1°, 1 are insulating blocks; 1' is a metallic portion constituting
the body of the plug. It will be noted that the tip 1° is continued through and
forms a continuation of the cord 1, and the body of the plug is continued by
connection in the cord 1. Surrounding the body portion of the plug is a
collar 1. This is loosely fitting, and adapted to slide reciprocally, but is held
forward by means of a coiled spring 1", which also surrounds the body of the
plug, and fits in a recess from inside of a casing 1º. This spring has sufficient
resiliency to withdraw the plug in the position shown in Figure 3, from a position
shown in Figure 4. It will be observed that the collar 1", in Figure 4, is com-
pressed back against the casing 1P, so that no contact is made with the tip of
ine plug by the springs in the spring jack. The springs, however, are forced
outwardly until contacts are made at 10 and 11, as shown also in Figure 1.
The mode of operation of this spring-collared plug would therefore be, that
when the operator pressed it home, as hereinafter described and as shown at
Figure 4, contacts 10 and 11 would be made; but immediately upon withdrawing
the pressure forcing the plug inward, the spring collar would automatically
retract it, thus making the contacts with the tip and the collar of the plug, as
shown in Figure 3.
To this construction of the plug no claim is laid in this application. Its general
features are well known to all electricians, and its features of construction and
mode of operation are utilized in effecting the tests and making and breaking
connections that are peculiar to this divisional switchboard, and therefore describe
it with sufficient particularity so that it will be readily seen how its automatic
action varies the connections.
The relays and annunciators are shown enlarged on Figures 5 and 6, Figure 5
showing the shutter P closed and held by the bell crank armature Z of the relay A²,

page_text: and also showing contact 15 closed. The electric circuit derived from the common
line L passes through the arm % of the armature of the relay A, contact 16
being closed, energizes the relay A2, and thence passes to the spring-actuated
bar P¹, through contact 15, to line leading to spring-jack 7. But the instant
energization of the relay A³ actuates the bell crank armature Z, allowing the
shutter to fall, this shutter, mechanically coming in contact with the spring
actuated bar P, breaks contact 15. Thus, while indicating the station called for,
it breaks the corresponding line, and no further impulse can be sent through the
relay A². It will be noticed that this action, therefore, of the relay A² is
momentary.
Figure 6 shows the relay A³ and annunciator A3 of the supposed calling line,
in its relation to the relay and annunciator of the called line (Figure 5) where the
entry of the plug in jack 1 makes contact 26, thus putting relay A on a line
leading to common line L³, or in the circuit D³ which passes through the relay
and by way of the pivot of its armature. The energizing of the relay actuates the
armature and breaks contact 27, or the circuit from the common line L³--D³
through the annunciator A³, preventing the actuating of the shutter P so long
as contact 27 is open.
In describing the operation of this apparatus, it will only be necessary to
describe and trace out the mode of operation on (1) the calling of one subscriber
by another, (2) placing the two in connection, and discontinuing the special
connection and restoring the normal connections after communication is closed;
(3) intermediately effecting a "busy" test to ascertain if a subscriber is busy.
Involved in these operations are the simultaneous cutting out of the subscribers'
lines from all other lines on the switchboard during the time they are in use, and
restoring them to normal conditions on the ceasing of communication, together
with the operation of the indicators and indicator circuits.
Assuming that the calling subscriber at T calls the operator through the sub-
scribers' circuit D D', this circuit, if traced out, will, when in a normal condition,
pass through the annunciator A, and operate the shutter which will drop and
expose the number of the calling subscriber, as shown in Figure 1. Thereupon,
the operator inserts the answering plug B into the spring jack 1, which belongs
to that of the calling subscriber. She pushes it home against the force of the
spring collar, making contacts 10, 11. This, by means of the circuit F F, puts
the operator's telephone or set in line with the calling subscriber, which circuit
is parallel to that through the annunciator A, there being sufficient impulse
diverted by reason of the resistance of the annunciator to operate the operator's
set. The office of the plug and spring jack in making these two connections 10
and 11 is purely mechanical. So long as its corresponding plug B' of the pair
is not in connection, there can be no passage of current through the plug or its
special connections. Through her set the operator ascertains the number of the
called subscriber, which we will assume to be No. 2, with set T. After ascer-
laining the called subscriber, she releases the answering plug, which, by the
elasticity of the coiled spring 1" and the collar 1, shown in detail in Figures 4
and 5, is withdrawn from the extreme position to that shown in Figure 1, thereby
breaking the contacts 10 and 11, making a contact with the tip of the plug at 12,
and with the collar at 13, preparatory to effecting a communication with sub-
scriber's set T. The dotted lines in the plug show the continuation of the
circuit D and D¹. The circuit D would therefore be continued on the lines con-
necting the plug to the local connecting plug B', the return circuit
D being also provided with and continuous through a test relay B.
The first thing the operator has to do, after ascertaining the called
subscriber's number, is to ascertain if the line of that called subscriber
is busy, or to make a "busy" test. By reference to Figure 2, it will be noticed
that the common line from the common battery L¹ is connected at S (on Figure 1)
with the line of the calling subscriber, and at ST with the line of the called

page_text: subscriber; and also, by the continuation L³ at S5, with the local jack of the
called subscriber in the connecting division of the switchboard on Figure 2.
This makes a circuit C (Figure 2) through the armature of the relay A, through
contact 16 and the local drop annunciator A2, and a contact 15 (when closed, but
shown open) with local jack No. 7, Figure 2; thence through on the line C in
Figures 1 and 2, to contact 14, local jack 4, when the local connecting plug B₁
has its tip presented to the opening of the local jack No. 4; and thence through
the test relay B to the collar of the answering plug B.
If the contact 15 is open, no action will take place in the test relay, and the
operator will get no response. If the contact 15 be closed so as to make this
circuit just described, the test relay B2 will be energised, drawing the armature B³
so as to make contact 17. This, it will be noticed, puts the operator's set in con-
nection on circuit C back to the common line L2, and its instantaneous action gives
a click in the operator's telephone at the same moment. This constitutes the test
indicating to the operator that the line of the called subscriber is not busy, while
the absence of the click indicates that the contact 15 is open, and hence that the
line is busy. The action of current, however, through the circuit C energises the
annunciator of the local drop A², withdraws the catch from the shutter in the
usual manner, and its dropping downward longitudinally actuates a plunger pl,
and opens the contact 15, as shown in the drawing, Figure 2, at the same time
indicating to the operator on the answering division, by the exposed number, that
the corresponding subscriber is called for. Hence, after the call, from whatever
source, as these lines are trunk lines connected to the common battery, the
contact 15 is open while the shutter exposes the number and the subscriber's line
is busy.
To return to the function of operator No. 1 for the moment: As soon as she has
indicated to the operator of the connecting division, by opening the shutter of
annunciator A2, she manually replaces the shutter of the annunciator A, which
is then ready to act as a disconnecting or ring-off signal, as hereinafter described.
On so ascertaining that the line of the called subscriber is not busy, the operator
on the receiving division proceeds to insert the plug B into the local jack No. 4,
Figure 1, and in doing so breaks the contact 14, making the contact 18 with the
collar of the plug, as indicated by the dotted line, and contact 19 with the tip of
the plug, as also indicated by the dotted line. Thus, the circuits I) I are con-
tinued, ending in the local jack No. 7 upon the connecting division. In the mean-
time, on ascertaining that the subscriber is called for, the operator upon the
connecting division takes one of a pair of plugs B, which are connected by two
lines in the usual manner, one having connection with the collar, and the ether
with the tip, and vice versa, and inserts it into the calling jack belonging to the
called subscriber and marked upon the diagram as calling jack No. 5. This, it
will be noted, corresponds to the called subscriber's answering jack 2 in the
answering division, Figure 1. Contact is made at 20 with the tip of the plug.
as shown by dotted line connecting the two points, and at 21 with the collar of
the plug, also shown by connections in dotted line. The opposite one of the pair
of plugs, called a local connecting plug B, is inserted into the local jack No. 7
upon the answering division as shown by the connecting dotted lines. This
insertion makes a contact 22 with the tip of the plug, and continues circuit ])¹
through the collar of a local connecting plug B, becomes circuit D¹ through the
test relay and to the answering plug B. This continues on circuit D' as marked,
to the calling subscriber's telephone set. Circuit D is continued to the called
subscriber's telephone set T and circuit 1' back to contact 21 on calling jack 5.
Thus, the two subscribers are put in connection through the circuit D D¹ as
described.
When the calling plug B is pushed home against the force of the spring collar
thereon (it being constructed like the plug shown in (Figures 3 and 4), it pushes
out the springs on the spring jack, making contacts 24 and 25, creating a circuit

page_text: energised by the generator G, placing the generator current on the called sub-
scriber's circuit, and indicating to the subscriber at his set that he is called.
Contacts 20, 21, and 30 are at that instant broken, but the retraction of the plug,
by its automatic withdrawal, due to the action of the spring collar, restores the
connections 20 and 21, and breaks contacts 24 and 25. Contact 30 remains open,
which cuts out the annunciator A¹ of the called subscriber, and as this contact
is not restored by the retraction of the plug, it remains out so long as the plug
is in the spring jack; therefore, the called subscriber cannot be again called by
any other person while he is talking with the calling subscriber.
The two subscribers then communicate. While they are communicating, the
operator on the answering division having restored the drop of the annunciator A,
as already stated, an impulse given by either subscriber (as it is now on the circuit
of both subscribers) drops it the second time, which indicates that they are through.
The circuit through the annunciator A being bridged between the circuits D
and D', a sufficient impulse passes through this bridge to actuate the annunciator,
the operator's set on the answering division being during this division cut out by
the breaking of contacts 10 and 11.
It is understood that when the plugs are removed, the lines are restored to their
normal position, the operator on the answering division again restoring the
annunciator shutter at A.
Considering the line in its normal position, and that the calling subscriber has
called as herein before stated, and that the answering plug B has been inserted in
spring jack 1 as herein before stated, and the test for "busy" having already been
made as stated, the further insertion of the local connecting plug into the spring
jack 4 (Figure 1) makes a connection 27 with circuit 12, which is continued on
the diagram, Figure 2, to an independent local common wire, and to an inde-
pendent local common battery L*. The circuit D2 then continues to a galvano-
meter indicator A', this indicator being of the usual, form of such indicators.
Through this the circuit D returns on Figure 1 to contact 27, this circuit being
energised by the local battery LA. The office of this battery is to energise
galvanometer indicators for each subscriber, as is shown at A and A8, they being
typical of all of them. It will be noted that this circuit returns upon the same
path as the circuit D' through a portion of the line.
The passage of the current through the indicator A7 shifts the needle from the
word "off," where it should be in a normal position, to the word "
on," and
thus affords a continuing indicator to the connecting operator, in addition to that
of the local drop A2, the office of the galvanometer indicator being to indicate at
all times the fact that the connections are made in the local jack 4 by the insertion
of a local connecting plug B¹, and that the line of the called subscriber is thus
continually in operation. The withdrawal of local connecting plug B₁ would of
course break the connection at 27, and at once the indicator would respond, and
thus, by the word "off," indicate to the operator in the connecting division that
the line was no longer in use. So long, therefore, as the subscribers remain in
connection, the galvanometer indicates the facts by the indicator finger pointing
to the position on." The operator at the answering division withdraws the plugs,
which action indicates to the operator at the connecting division, by means of
the galvanometer, which changes to "off," that she is also to withdraw the
plugs B B and restore the line to the normal position. The operator on the con-
necting division also closes the local drop P to its original position, which restores
contact 15, by virtue of a spring connection, forcing the plunger pl forward until
the contact is made.
The original insertion of the answering plug B into spring jack 1 makes
contact 26 in a circuit, which will be marked D³. This circuit passes through
relay As, Figure 2, and on common line L2 on Figure 1, (where it is also
marked D³) through contact 26 in spring jack 1, and on Figure 2 to common
line L³, the circuit being energized by the battery L¹. This circuit is in operation

page_text: while the plug B is inserted; on the withdrawal of the plug it is broken. This
circuit energizes relay A5, which then withdraws the armature from contact 27,
thus cutting off the relay A³. This relay A³ in Figure 2 is the relay belonging
to the calling subscriber. Therefore, the entering of the inserting plug B on the
answering division, Figure 1, operates to cut out this subscriber's local drop in
the connecting division, Figure 2, so that, while he is in conversation, no signal
from any other bank of the switchboard that such subscriber is wanted, can be
sent to the operator on the connecting division and, as already heretofore
described, any other operator in any other bank on the connecting division,
Figure 2, will be unable to plug in and interfere with the talking subscribers;
and, at the same time, by virtue of the test circuit being open, the absence of
the click to the answering operator of Figure 1 would indicate to that operator
that the calling subscriber was busy. Thus, the mistakes which are always
inadvertently made on switchboards do not annoy the talking subscribers, as
both of their lines are cut out from all others on the board when they are com-
municating.
Figures 7 and 8 represent three sections of a switchboard constructed on this
plan, and thus representing an indefinite extension of the same to as many
sections as may be, in practice, desired.
In these drawings, 01, 02 and 03 represent three sections on the answering
side of the board; and 01, 02b, and 03 represent corresponding sections on the
connecting side of the board (Figure 8); T, T and T represent three telephone
station lines respectively, each line being double with a metallic circuit, the
lines T ending in section O¹, lines T ending in section 02, and lines T ending
in section 03. These lines, of course, are representative of any number that may
enter the sections. All of the lines entering in the board are grouped so that
a convenient number enters each section, and there terminate in the answering
jacks 1, 2, 2. Annunciators are bridged across the lines as already described.
Lines D, D', D³ connect the answering and connecting divisions 01, 0 already
described. These are duplicated for each telephone line entering on each section,
the connections being readily traced by reference to Figures 1 and 2. As already
stated, as many lines enter each section of the board (each comprising the two
duplex divisions described) as may be desired; each of the lines T¹, T, Ts, being
representatives of those comprising the groups.
In addition to the answering jacks on the answering division of each section
for the group of lines entering that section, there are local jacks, 4, 4, on each
section for all the lines entering the board; while each connecting section of each
division contains local jacks 9, 9, corresponding to the connecting jacks 7, 7, 7b.
The local jacks 4, 4, on the answering divisions of each section are respectively
connected, one in each section, by trunk lines 4, 4b, 4º, each trunk line being
double to correspond with the metallic return.
It will be observed, therefore, that each connecting, division of a section has
grouped upon it; first, the connecting jacks of the lines grouped in the section;
second, local jacks (9, 9); third, local annunciators (PP) corresponding thereto;
and, fourth, a set of galvanometer indicators also corresponding to the numbers
of the group.
If, therefore, we assume that line T desires connection with some line not
entering on section 0¹, but upon any other section, as 03-say line T on
section 03, 03-the operator would insert the plug B into the jack 4 corre-
sponding to and connecting, through the trunk line 4, with the corresponding
jack on the connecting division in which line 1 entered, which in the case
supposed would be division 03 of section 03. The local annunciator P of that
section would fall and indicate that line T was desired, whereupon the con-
necting operator would connect jacks 9 and 7 in the same manner, and with the
result of connecting T with T as already explained with regard to the connection
of lines in one section only. In the case just supposed, the connection would be
over the trunk line 4°.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is:-
1. In an electrical switchboard, the combination of two divisions, an answering
division and a connecting division, each division having an independent line jack
for each subscriber's line circuit and permanently connected therewith, and each
division having a companion local jack for each subscriber's line, said local jacks
being permanently connected between the divisions by trunk lines through which
the talking circuit is made; and means for electrically connecting the line jacks
and the local jacks; substantially as described.
2. In an electrical switchboard, the combination of two divisions, an answering
division and a connecting division, each division having an independent line jack
for each subscriber's line circuit and permanently connected therewith, and each
division having a companion local jack for each subscriber's line, said local jack
being permanently connected between the divisions by lines through which the
talking circuit is made; means for electrically connecting the line jacks and the
local jacks; and an annunciator corresponding to and for each subscriber, located
in the connecting division, and adapted to be operated from his corresponding local
jack in the answering division; substantially as described.
3. In an electrical switchboard, comprised of an answering and a connecting
division; lines permanently terminating in two jacks, one in each division; an
additional local jack for each line in each division, said pair of local jacks being
electrically connected; a relay for each line, which relay is electrically connected
and operated by a plug when connected to the line jack on the answering division
whereby the operated line is broken by said relay, and is restored by withdrawing
the said plug from said line jack; substantially as described.
4. In a divisional switchboard having an answering and a connecting division,
the combination of lines ending in and permanently connected to line jacks, one
in each division; local jacks corresponding to the line jacks, one in each division,
said pair of local jacks being permanently electrically connected; local drop
annunciators in the connecting division, one for each line; and means for ener-
gising the annunciators; substantially as described.
5. In a divisional switchboard having an answering and a connecting division,
the combination of lines ending in and permanently connected to line jacks, one
in each division; local jacks corresponding to the line jacks, one in each division;
local drop annunciators in the answering division, one for each line,
said local annunciators being normally electrically connected to the corre-
sponding line jack in the connecting division; substantially as described.
6. In a duplicate switchboard system for telephones and analogous devices, the
combination of a multiplicity of outlying station lines entering therein, cach
line being permanently connected to a pair of jacks, one in an answering and
one in a connecting division of said board; a pair of local jacks corresponding
to and for each line, one in each division of said board, said jacks being per-
manently connected together, but normally disconnected from any operative
circuit; and means for connecting any one of the terminal jacks and any one
of the local jacks upon each division of the board for completing the talking
circuit; substantially as described.
7. In a duplex switchboard system for telephones and analogous devices, the
combination of a multiplicity of outlying station lines entering therein, each
line being permanently connected to a pair of jacks, one in an answering and
one in a connecting division of said board; a pair of local jacks corresponding
to and for each line, one in each division of said board, said jacks being per-
manently connected together, but normally disconnected from any operative
circuit; means for connecting any one of the terminal jacks and any one of
the local jacks upon each division of the board for completing the talking circuit;
and suitable switches actuated by such means, for cutting out and isolating said

page_text: talking circuit when the same is formed, and for restoring it to its normal con-
nections when said talking circuit is disconnected; substantially as described.
8. A duplex switchboard system for telephones and analogous devices, con-
sisting of a multiplicity of lines leading in from outlying stations, each station
line terminating in a divisional switchboard in two line jacks to which said line
is permanently connected, one being in an answering division and one in a
connecting division of said board; an annunciator visible upon the answering
division and normally forming a part of the circuit leading from and returning
to the corresponding outlying station, but adapted to be disconnected at the corre-
sponding line jack upon the connecting division; a pair of connected local jacks,
one in each division, corresponding to and for each entering station line, but
normally disconnected therefrom; a connected pair of plugs in each division
adapted to connect the line jacks and the local jacks therein, but normally dis-
connected therefrom; and means for energising the circuits; substantially as
described.
9. In a duplex switchboard system for telephones or analogous instruments,
the combination of outlying station lines entering therein, each station line
terminating in a divisional switchboard in a pair of line jacks to which said line
is permanently connected, one jack in an answering division and one in a con
necting division of said board; a corresponding pair of connected local jacks for
each line, one in the answering and one in the connecting divisions; an annun-
ciator upon the connecting division corresponding to each line; said annunciator
being located in a line connecting a common battery line and the corresponding
local jack on the answering division, and adapted to be operated from said local
jack; means normally disconnected from but adapted to connect the line jack
and a local jack on the answering division and complete a circuit therethrough;
and means connected with said annunciator whereby on completing said circuit
it simultaneously operates a signal on the connecting division and breaks its
own circuit; substantially as described.
10. In a duplex switchboard for telephones and analogous devices, the com-
bination of a multiplicity of station lines entering therein, each line being per-
manently connected to a pair of jacks, one in the answering and one in the con-
necting division of said board; a pair of permanently connected local jacks
corresponding for each line, one in each division of said board, but normally
disconnected from any operative circuit; means for connecting any one of the
terminal jacks and any one of the local jacks upon each division of the board
for completing the talking circuit; an annunciator on the connecting division
for each station line, located on a line leading from a battery common line to the
line connecting the local jacks; a relay in a line connecting said annunciator
line and the corresponding line jack upon the answering division, but not
normally connected thereto; and means whereby said relay is adapted, on being
energised, to break the circuit from the said common line to the local jack
line; substantially as described.
11. In a switchboard divided into a receiving division and an answering
division, the combination and arrangement of answering jacks and local jacks on
the receiving division corresponding to subscriber's lines; answering plugs
adapted to enter the answering jacks on the answering division, each answering
plug having connected therewith a local plug by a double line as described; a
test relay located in one of the lines, a circuit between the plugs; an operator's
set on a line between a common line and the test relay; a local relay and a
local drop in series with the armature of a local relay in the answering division;
means for energising the lines through the test relay, whereby the entry of the
answering plug in the answering jack, and the touch of the tip of a local plug to
the local jack, energise for an instant the test relay, and close contact there-
through with the operator's telephone in parallel with the circuit through the
answering jack, thus indicating to the operator that the line is not busy; sub-
stantially as described.

page_text: 12. In a telephone switchboard, the combination of an answering division;
a connecting division; a local relay, normally closed, located in the connecting
division; a line connecting the divisions through the local relay; means for
energising the same; a spring jack in the answering division; a plug adapted
to enter the same and mechanically make a contact, whereby the circuit is closed
through the local relay in the connecting division; a local drop in a series with
the local relay; lines normally connecting the same; and a contact adapted to
be broken by the action of the armature of the local relay when the contact is
effected by means of the plug in the receiving division; substantially as described.
13. In a divisional telephone switchboard having an answering division and a
connecting division, the combination and arrangement of answering jacks and
local jacks corresponding to subscribers' lines; plugs adapted to enter the
answering jacks on the answering division, each answering plug having connected
therewith a local plug by a double line; a local relay, and a local drop in series
with the armature of the local relay on the answering division, means whereby
the actuating of the local drop breaks connections and opens the line to the local
jack when the line is closed by contact with the local plug on the answering
division, whereby the subscriber called is disconnected from the means energising
the lines, so that another call cannot be made while his line is "busy," sub-
stantially as described.
Dated this 15th low of Desember 1900
WM. P. THOMPSON & Co.,
Agents.