Improvements in Switch Board Systems for Telephone Exchanges.
Year: 1892

page_text: Date of Application, 5th Mar., 1892
Complete Specification Left, 3rd Dec., 1892-Accepted, 7th Jan., 1893
PROVISIONAL SPECIFICATION.
Improvements in Switch Board Systems for Telephone Exchanges.
I, JOHN EDWARD KINGSBURY, of 79 Coleman Street, in the City of London,
Manager, (a communication to me from abroad by The Western Electric Company,
of Chicago, Illinois, United States of America,) do hereby declare the nature of
this invention to be as follows
This invention relates to multiple switch board systems for telephone exchanges.
Its several objects are: first, to provide circuits and mechanism whereby the
individual annunciator of a line shall be automatically reset or replaced by the
operation of making a connection to the line, and whereby it shall be rendered
unresponsive to signalling currents during said connection: second, to provide an
annunciator to respond to the signal for disconnection, and means for automatically
resetting the same: third, to provide suitable means for testing at any board to
determine whether a line is already in use or not; and, fourth to avoid all
connections and branches common to the different lines of the exchange.
The invention may be generally described as comprising: first, an annunciator
having two magnets or helices, one adapted to operate an indicator when energized,
and the other adapted to reset or restore said indicator to its normal position when
energized and to retain it in such position during its energization, circuit
connections including the first mentioned helix in the ine circuit or in a branch
therefrom, and other circuits including the second helix with a source of electricity
in a normally open local circuit adapted to be closed by the act of making connection
to the line; second, in a similar two coil annunciator having its operating helix
included in circuit with the connecting cords used for establishing connections
between different lines, and its restoring coil in a local circuit including a source of
electricity and normally open at contact points adapted to be closed by the
operation of connecting the operator's telephone to the cord circuit; third, in the
arrangement of parts and circuit connections whereby the operation of closing
the local circuit of the annunciator of a line serves also to alter the electrical
condition of the test pieces of the jacks of that line, enabling an operator at
another section of switchboard to determine whether the line is already in use
or not.
The invention is capable of being variously modified as to details, but a form
thereof which is well adapted to practical use may be constructed and arranged as
follows-The spring jacks may each consist of two line-springs of different
lengths, a test-ring insulated therefrom, and a contact piece between the line-springs
and the testing common to all the jacks.
Said spring jacks are distributed upon the different sections of switch board, one
spring jack for each line upon each switch board. An individual annunciator is
provided for each line upon some one of the boards. This annunciator is constructed
with two magnets or electro-magnetic helices one of which is adapted to operate an
indicator when it is energized, and the other of which is arranged to restore the
indicator to its normal position and to retain it inoperative while its coil is energized.
The former of these coils I designate the "operating coil" of the annunciator, and
the latter the "restoring coil."
The substation apparatus may be of the usual character. Each substation is
connected by suitable circuits, which may be either metallic or grounded, with its
particular switches upon the different switch boards, and with its individual
annunciator. The different sides of the line circuit are connected to the different
line-springs of the spring jacks, similar line-springs being connected to the same
side of line. A branch or bridge connection extends between the two sides of line,

page_text: and includes the operating coil of the individual annunciator of that line. The
test rings of each line are connected together and by a branch through the restoring
coil of the individual annunciator of that line, and through battery to earth.
The common contact pieces are connected together throughout the exchange and
to earth.
Connecting plugs are employed cach having three separate contact pieces com-
prising a tip adapted to make contact with the shorter line spring of the spring
jack into the plug which may be inserted, a short sleeve adapted to make contact
with the longer line spring of the jack, and a longer metallic sleeve adapted to
cross together the test thimble and the extra or common contact pieces of the jack.
Thus a signalling current sent from the substation will find circuit through the
operating coil of the individual annunciator of that line, but the insertion of a
connecting plug into a spring-jack of the line closes together the grounded extra-
contact-piece and the test rings of the line, thereby closing the local circuit
including the battery and the restoring coil of the annunciator; whereby the
indicator of the annunciator is restored to its normal position, and any subsequent
signalling current sent from the substation, as the clearing-out or disconnection
signal, will fail to operate the individual annunciator of the line.
A suitable number of connecting plugs are provided at each section of multiple
switch board, connected in pairs in the usual manner: that is, those contact pieces
of the two plugs which are adapted to engage with the two line springs of the jack
are connected together by conductors, like contact pieces of the two plugs being
joined. Calling keys of well known construction may be included in the conductors
joining the two plugs whereby both line contacts of either plug may be disconnected
from those of the other, and connected to a suitable source of electric current, to
send calling signals to a substation.
To respond to or receive the clearing-out or disconnection signals a clearing-out
annunciator is provided of construction similar to that of the individual annunciators.
The operating coil is included in a bridge connection between the different cord
strands joining the two plugs. Upon the operator's listening key, which is other-
wise of ordinary construction and adapted to connect the operator's telephone set
also in a bridge connection between the different cord strands, an additional contact
spring and a contact point are provided so disposed that they shall be closed
together when the key operated to connect the telephone set to the cord circuit.
These contact pieces are included in a local circuit containing the restoring coil of
the clearing-out annunciator and a source of electricity; thus by the operation
of closing the telephone set to the cord circuit, the clearing-out annunciator
is reset.
To enable the operator to test a line to determine whether it is already in use or
not a connection is provided preferably from the centre of the coil of the operator's
telephone receiver in the usual manner. Upon applying the tip of one of her
plugs to the test ring of the line which she desires to test, if the line is not in use,
she will perceive a click in the telephone due to a current from the battery in the
local circuit of which the test rings form one terminal sending current through the
tip of the plug and a portion of the telephone coil to earth. If, however, the line
he in use, the local circuit is closed directly to earth from the test ring by the long
sleeve of the plug by which the connection is established at some other 'spring
jack of the line, and hence no difference of potential will exist between the test
rings and the earth and no current will flow through the telephone.
The invention is illustrated in the accompanying drawing, wherein two sub-
stations are shown each connected by lines with two spring jacks upon two
sections of multiple switch board and with an individual annunciator at one of
the boards, connected together into a continuous circuit by a pair of plugs and
cords, and also a pair of plugs and cords in the position for testing a spring jack
of one of the lines.
..
The substation apparatus at station 1, at the left of the drawing, is of the
well known character, and consists of a calling 'generator a, and signalling bell'a

page_text: in one branch from line b, and telephone receiver a² and transmitter a³ in another
branch from the same line, and the gravity switch a connected to the other
side of line, and adapted to connect the signalling apparatus and the telephone
apparatus alternately into the line circuit, as the telephone receiver is removed
from or placed upon the switch hook.
The lines are connected respectively to the line springs cc of spring
jacks d upon two sections of switch board e e¹. A self restoring individual
annunciator is provided at the board el having its operating coil included in a
bridge between the lines. This annunciator consists briefly of the two coils ggt,
the former of which is adapted to actuate an armature provided with a catch g³
engaging with the upper edge of the soft iron disc g which is pivotted below and to
one side of its centre of gravity, whereby it tends to fall outward. This soft iron
disc is arranged to act as armature to the restoring coil ; a light shield go is
suspended immediately before the disc and is pivotted at its upper edge.
When the catch is raised, the armature is released, falling outward to a
slight distance, and in its fall pushing the shield into a nearly horizontal
position when the coil becomes energized it attracts its armature of restoring
it to its normal position, that shown in the drawing, and thus allowing shield g
to assume its normal position concealing the face of the disc g* and the number
which may be painted thereupon.
The spring jacks d and are provided with common contact pieces connected
to earth as described, and with insulating test rings i connected together and by a
branch conductor through the restoring coil g¹ of the annunciator and a battery k
to earth.
The connecting plugs as e, are constructed each with a tip e¹ making contact
with the shorter line spring c and short sleeve e making contact with the
longer line spring, and a third sleeve crossing together the test ring and
the common piece h. The tip of the two plugs of the pair are joined by
conductors in m and the shorter sleeves e by conductors m² m². Ringing keys n
are included in these conductors each adapted to disconnect the contacts e¹e of
one plug from the corresponding contact pieces of the other plug and to connect
them to wires o o' which form the terminals of the calling generator p.
A listening key is provided having three contact springs q' 9' 7' adapted to
be forced outward by the depression of the plunger q and contact pieces 9° 9°
and adapted to make contact with the three springs respectively when said
plunger is depressed. Of these, contact pieces 96 and 7 are connected to the
conductors m and m³ respectively; the springs q and g³ form the terminals of
the operator's telephone set which is thus connected in a bridge wire between
the cord strands m and m¹ when the said plunger is depressed. The spring 9³
is connected directly to earth, while the contact forms one terminal of the
branch extending through the restoring coil s¹ of the clearing out annunciator s
and thence through a battery to earth, the operating coils of the annunciator s
is connected in a bridge connection between the cord strands m and m². A
ground connection is attached to the centre of the coil of receiver in the well
known way for testing purposes.
I will now trace in detail the operation of the system shewn in the diagram.
Suppose that subscriber at station 1 wishes to communicate with a subscriber
at another station as, for example, station 2. The switch a being down, the
subscriber at station 1 operates his generator a thus sending calling current over
lines and through the operating coil g of his individual annunciator f. The
annunciator is thereby operated and the attention of the operator is directed to the
calling line. The operator then inserts a plug as e into the jack d' of that line at
her board e, and depresses the plunger of her listening key, whereby her telephone
is connected in a loop circuit with the lines bb². As soon as the plug e is inserted
into the jack d', the circuit of the battery k is closed through the restoring coil gl
of the annunciator f, through the test ring i and contact piece of jack d¹ to earth;
and the coil g being thus energized attracts its armature 9' and restores the

page_text: annunciator to its original position. The operator having learned from subscriber
at station 1 the number of the line with which he desires connection, proceeds to
test that line by applying to the test ring at her board the tip of the other
connecting plug of the pair, her telephone being still connected in the cord circuit.
The plug at board e is shewn in the act of making such a test. In case the line
tested is already in use, as the line to station 2 is in the drawing, the test rings i of
that line are short circuited to earth through the sleeve e³ and contact pieces of
the jack at which connection already exists and no effect will be produced in the
telephone of the operator testing. If, however, the line were not in use, the test
rings of the line would be disconnected from earth and hence a difference of
potential would exist between them and the earth due to the electro-motive force of
the battery and a ground test plug applied to the test ring would receive current
which would cause a click in the telephone included in circuit with it; hence an
operator testing a line and perceiving a click in her telephone at each application
of the testing plug to the test ring of the line, will conclude that the line is not in
use. We will assume that the operator at board e' finds line to station 2 not in use;
she then inserts the other pluge of her pair into the jack d³ of the lines to station 2
at her board, whereby the stations 1 and 2 are looped together in a continuous
circuit, which may be traced as follows:-
C
From the telephone at station 1 by line to the line spring c of jack, thence
through the tip of plug e, through the contacts of the ringing key to tip of
plug, to line spring of jack d³ of line 2, thence by line to station 2 returning,
over line to line spring e¹ of jack d³, thence through sleeve e² of plug e, contacts
of ringing key n', conductor m' m', contacts of ringing key n, to the sleeve e of
plug e, thence to line spring e' of jack d, thence returning over line to station 1.
The operator at board e now depresses the plunger of her key n disconnecting
the springs thereof from the conductors m³ m and connecting them to the poles 00
of the generator p thereby sending a calling current to station 2 and operating the
signal bell at that station.
Having ascertained that the subscribers have engaged in conversation, the
operator allows the plunger 7 of her listening key to rise, thereby disconnecting
her telephone set from the conductors m m.
C
When the subscribers have completed their conversation, one or both of them,
we will consider only subscriber at station 1, may send a clearing-out or disconnec-
tion signal; the signalling current will divide at the line springs ce' of jack d', a
portion passing through the operating coil y of annunciator: this annunciator
will, however, not be operated since the restoring coil g' is energised and retains the
armature preventing its movement. Another portion of the signalling current
will reach the conductors mm² where it will again divide, a portion passing through
the operating coil 2 of the clearing-out annunciator s. The local circuit containing
restoring coils of this annunciator is open, the operator's telephone set being
disconnected, and hence its armature is unattracted and falls, indicating the
disconnection signal to the operator. Another portion of the current will escape
through the conductors mm² and a portion of the conductors 626 through the
operating coil
of the annunciator, but the local circuit of its restoring magnet is
also closed through the sleeve of the connecting plug in the jack d³, and
hence this individual annunciator also will be unresponsive.
In response to the clearing-out signal, the operator at board e¹ may again bring
her telephone set into connection with the cord strands mm' to assure herself that
the conversation between the subscribers has been finished. The contact pieces g³ g'
upon the key are thus closed together, completing the local circuit through the
restoring coils and restoring clearing-out annunciator to its normal position. It is
not, however, necessary that the operator should connect her telephone to the lines
at this stage, since she must of necessity do so when she receives another call, and
will thereby reset the clearing-out annunciator of that pair of coils.
Having ascertained that the subscribers have completed their conversation, she
removes the connecting plugs from the spring jacks.

page_text: The number of operations or movements which the operator is required to make
in establishing and severing connection between the two subscribers and restoring
the apparatus to its normal position is by this system materially reduced, the special
annunciators being automatically restored to their normal positions by the act of
connecting the subscribers.
Moreover since the operator is not required to reset the aununciators manually
they may be placed above the switch board, and the space upon the face of the
switch board which is ordinarily occupied by annunciators, may be utilized for
spring jacks, thereby increasing the capacity of the switch board.
It will be observed that when metallic circuits are employed in this system, no
connections common to the different lines are required. The restoring circuits and
the test circuits are wholly local and are entirely disconnected and insulated from
the line circuits.
A modification of the invention which may be especially adapted to the conditions
of some exchanges, consists in such a disposition of the battery in the test or
restoring circuit that the test signal, the click in the operator's receiver shall be
given when the line is in use, no signal being given when an idle line is tested, as in
the test systems in ordinary use. In order to accomplish this, battery k is placed in
circuit between the common contact pieces and earth, and ground restoring
coils g' of the individual annunciators directly. With this arrangement, the test
rings of the idle line will not be electrified, but when a connecting plug is inserted
in any spring jack of the line the electrified contact pieces are crossed with the
test ring thereby electrifying the latter; thus a grounded plug applied to the test
ring will receive current therefrom and the signal will be given in the operator's
telephone.
I do not wish to limit myself to the employment of restoring annunciators only,
I sometimes employ annunciators such as the following:
1
The annunciator is simply provided with two coils or magnets arranged to act
differentially upon an armature common to both, which armature is adapted to
operate an indicator when actuated in a certain direction. The magnet or helix
which tends to release or operate the indicator is termed the "operating coil" and
the other, which is adapted to counteract the influence of the operating coil and to
render the annunciator unresponsive when the operating coil is energized, is termed
the retaining coil." When this annunciator is employed in connection with this
system, the operating coil is included as in the present instance in the branch circuit
between the two sides of the line, and the retaining coil is placed in the local
circuit instead of the restoring coil of the self-restoring annunciator. In the
system, thus modified, the advantages other than the self-restoring feature remain
unimpaired.
$
Dated this 5th day of March 1892.
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Switch Board Systems for Telephone Exchanges.
1, JOIN EDWARD KINGSBURY, of 79 Coleman Street, in the City of London,
Manager, (a communication to me from abroad by The Western Electric Company,
of Chicago, Illinois, United States of America,) 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 invention relates to multiple switch board systems for telephone exchanges.
Its several objects are first, to provide circuits and mechanism whereby the
individual annunciator of a line shall be automatically reset or replaced by the
operation of making a connection to the line, and whereby it shall be rendered
unresponsive to signalling currents during said connection: second, to provide an

page_text: annunciator to respond to the signal for disconnection, and means for automatically
resetting the same: third, to provide suitable means for testing at any board to
determine whether a line is already in use or not: and, fourth to avoid all
connections and branches common to the different lines of the exchange.
The invention may be generally described as comprising: first, an annunciator
having two magnets or helices, one adapted to operate an indicator when energized,
and the other adapted to rest or restore said indicator to its normal position when
energized and to retain it in such position during its energization, circuit connections
including the first mentioned helix in the line circuit or in a branch therefrom, and
other circuits including the second helix with a source of electricity in a normally
open local circuit adapted to be closed by the act of making connection to the line;
second, in a similar two coil annunciator having its operating helix included in
circuit with the connecting cords used for establishing connection between different
lines, and its restoring coil in a local circuit including a source of electricity and
normally open at contact points adapted to be closed by the operation of connecting
the operator's telephone to the cord circuit; third, in the arrangement of parts and
circuit connections whereby the operation of closing the local circuit of the
annunciator of a line serves also to alter the electrical condition of the test pieces
of the jacks of that line, enabling an operator at another section of switchboard to
determine whether the line is already in use or not.
The invention is capable of being variously modified as to details, but a form
thereof which is well adapted to practical use may be constructed and arranged as
follows-The spring jacks may each consist of two line springs of different
lengths, a test ring insulated therefrom, and a contact piece between the line-
springs and the test ring common to all the jacks.
Said spring jacks are distributed upon the different sections of switch board, one
spring jack for each line upon each switch board. An individual annunciator is
provided for each line upon some one of the boards. This annunciator is con-
structed with two magnets or electro-magnetic helices one of which is adapted to
operate an indicator when it is energized, and the other of which is arranged to
restore the indicator to its normal position and to retain it inoperative while its coil
is energized. The former of these coils I designate the "operating coil” of the
annunciator, and the latter the "restoring.coil."
The substation apparatus may be of the usual character. Each substation is
connected by suitable circuits, which may be either metallic or grounded, with its
particular switches upon the different switch boards, and with its individual annun-
ciator. The different sides of the line circuit are connected to the different line-
springs of the spring jacks, similar line-springs being connected to the same side
of line. A branch or bridge connection extends between the two sides of line,
and includes the operating coil of the individual annunciator of that line. The
test rings of each line are connected together and by a branch through the restoring
coil of the individual annunciator of that line, and through battery to earth. The
common contact pieces are connected together throughout the exchange and to
earth.
Connecting plugs are employed each having three separate contact pieces com-
prising a tip adapted to make contact with the shorter line spring of the spring
jack into which the plug may be inserted, a short sleeve adapted to make contact
with the longer line spring of the jack, and a longer inetallic sleeve adapted to
cross together the test thimble and the extra or cominon contact pieces of the jack.
Thus a signalling current sent from the substation will find circuit through the
operating coil of the individual annunciator of that line, but the insertion of a
connecting plug into a spring jack of the line closes together the grounded'extra-
contact piece and the test rings of the line, thereby closing the local circuit
including the battery and the restoring coil of the annunciator, whereby the
indicator of the annunciator is restored to its normal position, and any subsequent
signalling current sent from the substation, as the clearing-out or disconnection
signal, will fail to operate the individual annunciator of the line.

page_text: A suitable number of connecting plugs are provided at each section of multiple
switch board, connected in pairs in the usual manner: that is, those contact pieces
of the two plugs which are adapted to engage with the two line springs of the
jack are connected together by conductors, like contact pieces of the two plugs
being joined. Calling keys of well known construction may be included in the
conductors joining the two plugs whereby both line contacts of either plug may be
disconnected from those of the other, and connected to a suitable source of electric
current, to send calling signals to a substation.
To respond to or receive the clearing out or disconnection signals a clearing-out
annunciator is provided of construction similar to that of the individual annunciators.
The operating coil is included in a bridge connection between the different cord
strands joining the two plugs. Upon the operator's listening key, which is
otherwise of ordinary construction and adapted to connect the operators telephone
set also in a bridge connection between the different cord strands, an additional
contact spring and a contact point are provided so disposed that they shall be closed
together when the key is operated to connect the telephone set to the cord circuit.
These contact pieces are included in a local circuit containing the restoring coil of
the clearing-out annunciator and a source of clectricity thus by the operation
of closing the telephone set to the cord circuit, the clearing-out annunciator is
reset.
To enable the operator to test a line to determine whether it is already in use or
not a connection is provided preferably from the centre of the coil of the operator's
telephone receiver in the usual manner. Upon applying the tip of one of her
plugs to the test ring of the line which she desires to test, if the line is not in use,
she will perceive a click in the telephone due to a current from the battery in the
local circuit of which the test rings form one terminal sending current through the
tip of the plug and a portion of the telephone coil to earth. If, however, the line
be in use, the local circuit is closed directly to earth from the test ring by the long
sleeve of the plug by which the connection is established at some other spring jack
of the line, and hence no difference of potential will exist between the test rings
and the earth and no current will flow through the telephone.
The invention is illustrated in the accompanying drawing wherein two sub-
stations are shown each connected by lines with two spring jacks upon two sections
of multiple switch board and with an individual annunciator at one of the boards,
connected together into a continuous circuit by a pair of plugs and cords, and also
a pair of plugs and cords in the position for testing a spring jack of one of
the lines.
The substation apparatus at station 1, at the left of the drawing, is of the well
known character, and consists of a calling generator a, and signalling bell a' in one
branch from line b, and telephone receiver a' and transmitter a³ in another branch
from the same line, and the gravity switch at connected to the other side 6 of line,
and adapted to connect the signalling apparatus and the telephone apparatus alter-
nately into the line circuit, as the telephone receiver is removed from or placed upon
the switch hook.
The lines are connected respectively to the line springs cc of spring
jacks d d' upon two sections of switch board E. E.
A self restoring individual
annunciator is provided at the board e' having its operating coil g included in a
bridge between the lines b b¹. This annunciator consists briefly of the two
coils g g', the former of which is adapted to actuate an armature 9' provided with
a catch engaging with the upper edge of the soft iron disc g* which is pivotted
below and to one side of its centre of gravity, whereby it tends to fall outward.
This soft iron disc is arranged to act as armature to the restoring coil g; a light
shield is suspended immediately before the disc g' and is pivotted at its upper
edge. When the catch g' is raised, the armature g is released, falling outward to à
slight distance, and in its fall pushing the shield 9 into a nearly horizontal position;
when the coil g' becomes energized it attracts its armature grestoring it to 'it's

page_text: normal position, that shown in the drawing, and thus allowing shield go to assume
its normal position concealing the face of the disc g' and the number which may be
painted thereupon.
The spring jacks d and d¹ are provided with common contact pieces h connected
to earth as described, and with insulating test rings i connected together and by a
branch conductor through the restoring coil g¹ of the annunciator fand a battery k
.to earth.
The connecting plugs as e are constructed each with a tip e¹ making contact with
the shorter line spring c and short sleeve e making contact with the longer line
spring, and a third sleeve e³ connecting together the test ring and the common
contact piece h. The tip of the two plugs of the pair are joined by conductors mm
and the shorter sleeves e² by conductors m² m². Ringing keys n n' are included in
these conductors each adapted to disconnect the contact e¹³ of one plug from the
corresponding contact pieces of the other plug and to connect them to wires o o¹
which form the terminals of the calling generator p.
A listening key q is provided having three contact springs q' 7³ q* adapted to be
forced outward by the depression of the plunger q and contact pieces qª 9º and q'
adapted to make contact with the three springs respectively when said plunger is
depressed. Of these, contact pieces 75 and 9° are connected to the conductors m
and m respectively the springs q and g² form the terminals of the operator's
telephone set which is thus connected in a bridge wire between the cord strands m
and m' when the said plunger is depressed. The spring is connected directly to
earth, while the contact forms one terminal of the branch extending through the
restoring coil s¹ of the clearing out annunciator s and thence through a battery/x
to earth the operating coil 2 of the annunciator is connected in a bridge connection
between the cord strands m and m³. A ground connection is attached to the centre
of the coil of receiver in the well known way for testing purposes.
I will now trace in detail the operation of the system shewn in the diagram.
Suppose that subscriber at station 1 wishes to communicate with a subscriber at
another station, as for example, station 2. The switch at being down, the subscriber
at station 1 operates his generator a thus sending calling current over lines b' and
through the operating coil g of his individual annunciator f. The annunciator is
thereby operated and the attention of the operator is directed to the calling line.
The operator then inserts a plug as e into the jack of that line at her board E',
and depresses the plunger of her listening key, whereby her telephone is connected in
a loop circuit with the lines bb. As soon as the plug e is inserted into the jack ',
the circuit of the battery k is closed through the restoring coil g¹ of the
annunciator, through the test ring i and contact piece of jack d¹ to earth, and
the coil g¹ being thus energized attracts its armature g₁ and restores the annunciator
to its original position. The operator having learned from subscriber at station 1
the number of the line with which he desires connection, proceeds to test that line
by applying to the test ring at her board the tip of the other connecting plug of
the pair, her telephone being still connected in the cord circuit. The plug e at
board e is shewn in the act of making such a test. In case the line tested is already
in use, as the line to station 2 is in the drawing, the test rings i of that line are short
circuited to earth through the sleeve e and contact pieces of the jack at which
connection already exists and no effect will be produced in the telephone of the operator
testing. If, however, the line were not in use, the test rings i of the line would be
disconnected from earth and hence a difference of potential would exist between
them and the earth due to the electro-motive force of the battery k and a ground
test plug applied to the test ring would receive current which would cause a click
in the telephone included in circuit with it; hence an operator testing a line and
perceiving a click in her telephone at each application of the testing plug to the
test ring of the line, will conclude that the line is not in use. We will assume that
the operator at board E¹ finds line to station 2 not in use; she then inserts the other
pluge of her pair into the jack d³ of the lines to station 2 at her board, whereby

page_text: the stations 1 and 2 are looped together in a continuous circuit, which may be traced
as follows:-
From the telephone at station 1 by line to the line spring c of jack d', thence
through the tip of plug e through the contacts of the ringing key n to tip of plug e,
to line spring c of jack d³ of line 2, thence by line to station 2 returning over
line & to line spring c¹ of jack d, thence through sleeve e of plug e, contacts of
ringing key n', conductor m' m², contacts of ringing key n, to the sleeve e of pluge
thence to line spring e¹ of jack d', thence returning over line & to station 1.
The operator at board E now depresses the plunger of her ringing key n¹
disconnecting the springs thereof from the conductors m m and connecting them to
the poles o o of the generator p thereby sending a calling current to station 2 and
operating the signal bell at that station.
Having ascertained that the subscribers have engaged in conversation, the
operator allows the plunger 7 of her listening key to rise, thereby disconnecting
her telephone set from the conductors m m.
When the subscribers have completed their conversation, one or both of them, we
will consider only subscriber at station 1, may send a clearing out or disconnection
signal, the signalling current will divide at the line springs e c¹ of jack d', a portion
passing through the operating coil g of annunciator f; this annunciator will however
not be operated since the restoring coil is energized and retains the armature g
preventing its movement. Another portion of the signalling current will reach the
conductors m m where it will again divide, a portion passing through the operating
coils of the clearing out annunciator s. The local circuit containing restoring
coils of this annunciator is open, the operator's telephone set being disconnected,
and hence its armature g¹ is unattracted and falls indicating the disconnection signal
to the operator. Another portion of the current will escape through the con-
ductors m m' and a portion of the conductors 62 63 through the operating coil g of
the annunciator, but the local circuit of its restoring magnet is also closed through
the sleeve of the connecting plug in the jack d³ and hence this individual
annunciator also will be unresponsive.
In response to the clearing out signal, the operator at board E' may again bring
her telephone set r into connection with the cord strands mm² to assure herself that
the conversation between the subscribers has been finished. The contact pieces q³ q²
upon the key are thus closed together, completing the local circuit through the
restoring coils and restoring clearing out annunciator to its normal position. It
is not, however, necessary that the operator should connect her telephone to the
lines at this stage, since she must of necessity do so when she receives another call,
and will thereby reset the clearing out annunciator of that pair of coils.
Having ascertained that the subscribers have completed their conversation, she
removes the connecting plugs from the spring jacks.
The number of operations or movements which the operator is required to make
in establishing and severing connection between the two subscribers and restoring
the apparatus to its normal position is by this system materially reduced, the
special annunciators being automatically restored to their normal positions by the
act of connecting the subscribers.
Moreover since the operator is not required to reset the annunciators manually
they may be placed above the switch board, and the space upon the face of the
switch board which is ordinarily occupied by annunciators may be utilized for
spring jacks, thereby increasing the capacity of the switch board.
It will be observed that when metallic circuits are employed in this system, no
connections common to the different lines are required. The restoring circuits and
the test-circuits are wholly local aud are entirely disconnected and insulated from
the line circuits.
A modification of the invention which may be especially adapted to the conditions
of some exchanges, consists in such a disposition of the battery in the test or
restoring circuit that the test signal, the click in the operator's receiver, shall be
given when the line is in use, no signal being given when an idle line is tested, as in
B

page_text: the test systems in ordinary use. In order to accomplish this, battery is placed
in circuit between the common contact pieces and earth, and ground restoring
coils g of the individual annunciators directly. With this arrangement, the test
rings of the idle line will not be electrified, but when a connecting plug is inserted
in any spring jack of the line the electrified contact pieces h are crossed with the
test ring thereby electrifying the latter; thus a grounded plug applied to the test
ring will receive current therefrom and the signal will be given in the operator's
telephone.
I do not wish to limit myself to the employment of restoring annunciators only,
I sometimes employ annunciators such as the following:
The annunciator is simply provided with two coils or magnets arranged to act
differentially upon an armature common to both, which armature is adapted to
operate an indicator when actuated in a certain direction. The maguet or helix
which tends to release or operate the indicator is termed the "operating coil" and
the other which is adapted to counteract the influence of the operating coil and to
render the annunciator unresponsive when the operating coil is energized, is termed
the "retaining coil." When this annunciator is employed in connection with this
system, the operating coil is included as in the present instance in the branch
circuit between the two sides of the line, and the retaining coil is placed in the
local circuit instead of the restoring coil of the self restoring annunciator. In the
system thus modified the advantages other than the self restoring feature remain
unimpaired.
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
1. The combination of two electro magnets mounted heel to heel the armatures
of said magnets and the hook or latch extending from one armature to normally
engage with the armature of the other to hold the same from falling, and circuits
through the different magnets; whereby when current is sent through the magnet
baving the latch or hook, the armature of the other magnet is released, said
armature being restored when current is sent through the electro magnet thereof.
2. The combination, with the armature of an electro magnet, of a curtain or target
pivoted in front of the same, said armature serving as the drop of an annunciator,
and being of greater weight than the curtain, the armature when released being
adapted to fall against the curtain near the pivotal axis thereof; whereby the
curtain is moved a greater distance than the armature, substantially as specified.
3. The combination, with the operating electro magnet, its armature and
armature lever hook, of the restoring electro magnet and its armature provided
with a latch, with which latch the hook is adapted to engage, circuits through the
different magnets and switching devices, whereby on closing the circuit through
the operating magnet, the armature of the restoring magnet is released to act as an
annunciator drop, said armature being attracted and restored to its engagement
with the hook when circuit is closed through the restoring magnet, substantially as
specified.
4. The combination, with a drop shutter of soft iron pivoted below and to one
side of its centre of gravity, of a shield or apron placed near to and parallel with
said drop shutter pivoted at its upper edge, the upper edge of said drop shutter
engaging with said shield near its pivotal point, whereby said apron is pushed
outwardly by the movement of said drop shutter, substantially as described.
5. The combination, in a spring jack, of two line springs of different lengths, a
test ring in front of the presented ends of said line springs and insulated from them,
and an extra-contact-piece insulated from both the line springs and the test ring
but adapted to be crossed with said test ring by the insertion of the plug into the
jack, substantially as specified.
6. The combination with a spring jack having two line springs of different
lengths, a test ring insulated from said line springs, and an extra contact piece, of a

page_text: connecting plug inserted in the spring jack having a tip making contact with the
shorter line-spring thereof, a sleeve making contact with the longer line spring
thereof and another sleeve or contact piece crossing together the test ring and said
extra contact piece of the jack substantially as described.
7. The combination with a telephone circuit extending from a substation to a
central station, of spring jacks at the central station each having four contact
pieces insulated from each other, similar contact pieces of the different spring
jacks being connected together, two different contact pieces of one jack of the
group being connected to the different sides of line respectively substantially as
described.
8. In a test system for multiple switch boards the combination with a telephone
circuit extending from a substation to a central station of spring jacks at the central
station each having four contact pieces insulated from each other, similar contact
pieces of the different spring jacks being connected together, and two different
contact pieces of one spring jack of the group being connected to the different
sides of line respectively, and a conductor joining one series of the remaining
contact pieces directly to earth and another conductor joining the other series
of remaining contact pieces through a source of electricity to earth, substantially
as described.
9. In combination, a telephone line extending from a substation to a central
station, spring jacks at the central station each having four contact pieces insulated
from each other, like contact pieces of the different spring jacks being electrically
connected together, two of the different groups of contact pieces being connected
to the different sides of the line circuit respectively, one series of the remaining
contact pieces being connected directly to earth and the other series of contact
pieces being connected through a source of electricity to earth, a connecting plug
inserted in the spring jack having three contact pieces two of which make contact
with the line contacts of the jack and the remaining contact pieces of which cross
together the remaining contact pieces of the jack into which it is inserted, and
means for determining the electrical condition of any one of the connected groups
of spring jacks, substantially as described.
10. The combination with a telephone circuit extending from a substation to a
central station, connected at the central station to spring jacks each having two
line springs connected respectively to the different sides of line, a test ring insulated
from the line springs, and an extra contact piece normally insulated from both the
test rings and the line springs, like contacts of all the spring jacks being connected
together, the extra contact piece being grounded directly and the test rings being
grounded through a battery, of the connecting plug adapted to be inserted into any
one of said spring jacks, provided with three contact pieces two of which are
adapted to make contact with the different line springs respectively of the jack and
the remaining contact piece to cross together the test ring and the extra contact
piece of the jack whereby the electrical condition of all the test rings of the line
is altered by the insertion of said connecting plug into any spring jack of the group,
substantially as described.
11. The combination with a telephone circuit extending from a substation to a
central station, connected at the central station to spring jacks each having two
line springs connected respectively to the different sides of line, a test ring insulated
from the line springs, and an extra contact piece normally insulated from both the
test ring and the line springs, like contacts of all the spring jacks being connected
together, the extra contact piece being grounded directly and the test rings being
grounded through a battery, of the connecting plug adapted to be inserted into any
one of said spring jacks, provided with three contact pieces two of which are
adapted to make contact with the different line springs respectively of the jack and
he remaining contact piece to cross together the test ring and the extra contact
piece of the jack, and a testing plug connecting through a suitable responsive
levice to earth whereby it may be determined by applying said test plug to the

page_text: test ring of any spring jack whether a connecting plug is inserted in some spring
jack of the group or not, substantially as described.
12. The combination with a telephone line extending from a substation to a
central station, of spring jacks at the central station each having four contact
pieces insulated from each other, like contact pieces being connected together, two
groups of contact pieces being connected to the different sides of line circuit
respectively, an individual annunciator having two electro magnets one of which is
adapted to actuate a suitable indicator when energized, the other of which is
adapted to prevent the operation of such indicator when energized, the first
mentioned of such coils being included in the line circuit or in a branch thereof,
and circuit connections including the remaining magnet of said indicator with a
source of electricity in a local circuit of which the two remaining groups of contact
pieces form normally separated terminals, substantially as described.
13. The combination, with a telephone line circuit, extending from a substation
to a central station, connected with spring jacks at the central station each of
which spring jacks is provided with two line springs, a test ring insulated from
both the line springs, and an extra contact piece insulated from both the test ring
and the line spring, like contact pieces of all the spring jacks being connected
together, the different groups of line springs being connected with the different
sides of line respectively, of an individual annunciator provided with two electro
magnets one of which is adapted to actuate a suitable annunciator when energized,
and the other of which is adapted to prevent the operation of such indicator when
energized, the said electro magnets being included in the line circuit or in a branch
therefrom, local circuit connections including the remaining magnet of said
annunciator with a source of electricity in a local circuit of which the group of
test rings and the group of extra contacts upon the spring jacks form normally open
terminals, and a connecting plug having three contact pieces, inserted in one of
said spring jacks, two of said contact pieces making contact with the different line
springs respectively of the jack into which it is inserted and the remaining contact
piece crossing together the test ring and the extra contact piece of the jack,
whereby the said local circuit is closed and the indicator of the individual
annunciator is rendered unresponsive, substantially as described.
14. The combination with two connecting plugs each having two different contact
pieces, and conductors joining the like contact pieces of the two plugs, of the
operator's telephone and a key adapted to connect the same in circuit between the
different contact pieces of the plugs, a clearing out annunciator having two electro
magnets, one, the operating coil, of which annunciator is adapted to actuate a
suitable indicator when energized, and the other, the restoring coil, of which is
adapted to restore the said indicator to its normal position, said operating coil being
included in a circuit between the different contact pieces of the connecting plugs,
insulated contact pieces upon the aforesaid key so disposed as to be closed together
by the operation of connecting the operator's telephone set in circuit between the
connecting plugs, and circuit connections including the restoring coil of the
annunciator with a source of electricity in a local circuit of which the contact
pieces upon the key form normally open terminals, whereby the indicator of the
clearing out annunciator is restored to its normal position by the operation of
connecting the operator's telephone set to the connecting plugs, substantially as
described.
15. In combination, two telephone line circuits extending from their respective
substations to a central station, each being connected to a group of spring jacks at
the central station each of which spring jacks comprises two line springs which are
connected respectively to the different sides of the line circuit, a test ring insulated
from the line springs and an extra contact piece insulated from both the line
springs and the test ring, the like contact pieces of all the jacks of each group
being connected together, and cach line circuit being completed through the
operating coil of an individual annunciator having two electro-magnets, of which

page_text: one, the operating magnet, is adapted to actuate a suitable indicator when energized,
and the other, the retaining coil, is adapted to prevent the operation of said
indicator, circuit connections for each line circuit including the retaining coil of
its particular individual annunciator with a source of electricity in a local circuit
of which the group of test rings and the group of extra contact pieces of its
particular group of spring jacks form normally open terminals, a connecting plug
inserted into one jack of each group, the said connecting plug having three contact-
pieces, of which two, the line contacts, make contact with the different line springs
respectively of the jack into which it is inserted and the remaining contact piece
crosses together the test ring and the extra contact piece of the jack, the line
contacts of the two plugs being connected together by suitable conductors, and a
clearing-out annunciator in a circuit between the different line contacts of the two
connecting plugs, whereby the two line circuits are joined into a continuous loop
circuit, the focal circuits of both lines are closed, and their annunciators prevented
from operating; a suitable indicating device being provided in their place to operate
in response to the signal for disconnection, substantially as described.
16. In combination, two telephone line circuits extending from two substations
to a central station two groups of spring jacks at the central station, each spring
jack of which is provided with two line-springs, a test-ring insulated from the line-
springs and an extra contact piece insulated from both the line springs and the test
ring, like contact pieces of each group of spring jacks being connected together, and
the line springs being connected to the different sides of the line circuit respectively
of one of the lines, two individual annunciators each having an operating coil and
a restoring coil, the said operating coil being included in a circuit between the
different sides of line of its particular line circuit and said restoring coil being
included with a source of electricity, in a local circuit of which the group of test
rings and the group of extra contacts of its particular group of spring jacks form
terminals, connecting plugs each having three contact pieces of which two, the
line contacts, are adapted to make contact with the line-springs of the jack into
which it may be inserted, and the remaining contact piece is adapted to cross
together the test ring and the extra contact piece thereof, one plug being inserted
in a spring jack of each group, conductors joining like line contacts of the two
plugs; an operator's telephone set and a key adapted to connect the same in circuit
between the different contact pieces of the plugs and a clearing-out annunciator
having an operating and a restoring coil, the operating coil being included in a
circuit between the different contact pieces of the plugs, the restoring coil being
included with a source of electricity in a local circuit terminating in two normally
separate contact pieces upon said listening key adapted to be closed together by
the operation of connecting the telephone set to the plugs whereby the different
annunciators of the system are automatically restored to their normal positions by
the necessary operations in establishing connection between the two lines,
substantially as described.
Dated this 3rd day of December 1899