Improvements in Telephone Systems.
Year: 1895

page_text: Date of Application, 13th June, 1895
Complete Specification Left, 13th Mar., 1896-Accepted, 18th Apr., 1896
PROVISIONAL SPECIFICATION.
Improvements in Telephone Systems.
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 telephone systems and provides improved means for.
the transmission of signals from the substation of a telephone line to the telephone
switch board at an exchange and improvements in the switchboard apparatus and
methods, also the adaptation of the switchboard improvements to the existing
methods of signalling with a magneto generator at the substation.
The invention involves the use of annunciators or signals which are adapted to
be operated or excited by a predetermined normal current, but to remain inert
when traversed by a current materially less, as for example by half of the normal
current. In practice incandescent lamps are found to be suitable signals of this
type, being illuminated by a suitable current but remaining unlighted when
traversed by half of this current.
Two such signals are according to this invention arranged in parallel branches
of a local circuit, and the continuity of one of the branches is controlled by a relay
responding to currents in the telephone line. The signal in the branch controlled
by the relay is designed to act as an individual signal and is permanently associated
with a particular line; the other signal may be associated with one of the plug
circuits provided for uniting different telephone lines, and the branch including it
may be normally open, terminating in a contact piece in the connecting plug
adapted to complete the branch while the plug is in use in a springjack.
In the normal condition of the apparatus at the switchboard the individual
signal is free to respond to currents in the corresponding line circuit caused by the
completion or interruption of the line circuit at the substation, and thus by its
display may indicate an initial or call signal from the substation. When, however,
in response to such a signal, connection has been made with the line, the other of
the two branches is closed through the clearing out or disconnection signal,
whereby the indication of the individual signal is effaced, the clearing out signal
remaining inert. The signals remain in this condition until the relay, responding
to an altered condition of the line circuit, opens the branch including the individual
signal, whereby the clearing-out signal is excited.
In one form of apparatus arranged according to this invention the substation of
each telephone line is provided with a switch, preferably an automatic telephone
switch, by which the normally open line circuit may be closed during the use of the.
telephone at the substation; and in the switchboard at the central station a relay
and a source of current are included in the line circuit, the contact points of the
relay being adapted, when the relay is excited, to complete the branch of the
before mentioned local circuit which includes the individual signal corresponding
to the line. The interrupted portions of the other branch of the local circuit
terminate, respectively, in a contact piece in each of the springjacks of the line,
and in a corresponding contact piece upon the connecting plug which is designed
to be inserted in the springjack to establish connection with the line. The source
of current in the local circuit is common to the different pairs of plugs in the

page_text: switchboard, and these are, therefore, interchangeable with respect to their use in
different springjacks; hence any plug may be used in connection with any
springjack without interfering with the operation of the associated clearing out
signal.
In a switchboard system thus organized the removal of the telephone from the
switch hook at a substation causes the excitement of the relay in that line at the
central station, and thus operates or excites the corresponding individual signal in
the switchboard. The operator thereupon inserts a plug into the springjack,
effacing the indication of the individual signal; the clearing-out signal still
remains inert, since the current in the local circuit is divided between the two
signals. When, however, the telephone at the substation is replaced upon its
switch hook, the circuit of the line is interrupted, the relay is no longer excited
and it interrupts the branch of the local circuit including the individual signal,
thus diverting the full current through the clearing-out signal and causing the
latter signal to be displayed.
If a connecting plug be inserted in a line which is free, that is, which is not
already in use, the clearing out signal remains excited until the substation
telephone is brought into use, since the circuit through the individual signal of the
corresponding line is interrupted until that time; but if a plug be inserted into a
springjack of a line whose telephone is already in use, or with which a connection
already exists, either one or two branches of the local circuit will have been
already completed, so that the clearing-out signal of the plug last inserted into a
springjack of the line will remain iuert. The condition of the clearing-out signal
therefore constitutes a "test which signifies the free or "busy" condition of the
line with which connection is made. In a multiple switchboard the test thus
becomes automatic and is indicated by a suitable visible signal.
In Figure 1 two substations A and B are shown, each connected through line
conductors with springjacks upon different sections of a multiple switchboard, and
with a relay controlling an individual signal. The apparatus at the substations
comprises a receiving telephone c and a transmitting telephone c¹, a signal bell c²,
and an automatic switch arranged to close the line circuit alternately through
the telephonic and signalling appliances.
C
The apparatus of substation A is connected by line conductors 1 and 2 with two
springjacks d and d' upon different sections e and e¹ of a multiple switchboard at
the central station-the different line conductors terminating in different line
contacts and ¹, respectively, in each of the springjacks. The conductor 1 of
the line is extended through an impedance coil g to one pole of a battery h, while
conductor 2 is connected with the other pole of battery h, a line relay i being
included in the conductor. The battery h and relay i are so adjusted to the
resistance in the line circuit that when the circuit is closed through the bell c²,
which should be of high resistance, the relay is not appreciably excited; while
when the circuit is closed at the substation through the telephone the relay shall
attract its armature.
The contact points k of relay i are included in a branch 3 of the local circuit 3, 4,
of a battery 1, a resistance coil m being connected in the local circuit. The branch 3
includes also the individual signal lamp n which is associated with the springjack d
in the switchboard. Each springjack is provided with a contact ring 2, the
different contact rings being connected together through a wire 5 which is
connected with the conductor 4 of the local circuit.
Connecting plugs o and o¹ are provided for looping different telephone lines
together by means of their springjacks. Each plug contains two contact pieces p
and p' which are adapted to make connection with the line contacts f and fof the
springjack, and another contact piece p² which is arranged to connect with the
ring of the springjack. The contact pieces p of the two plugs are connected
together through a conductor 6, and the pieces p' by another conductor 7. Each
of these conductors includes a condenser, the condensers being designated q and q¹
respectively. The conductors 6 and 7 extend through the switch contacts of a

page_text: calling key r, by means of which a generators of signalling current may be looped
into connection with the plug o'; and branches from them are led to the switch
springs of a listening key t for connecting the operator's telephone u with the plug
circuit.
The contact piece p² of plug o coustitutes the terminal of a conductor 8 including
the clearing out signal lamp v which is associated with that plug; contact piece p³ of
plug o similarly constitutes the terminal of another conductor 9 including lamp
signal associated with plug o¹. Conductors 8 and 9 extend directly to the local
battery l.
The drawing represents the apparatus in its normal or idle position. The
telephones at the substations rest upon their switch hooks, so that the line circuits
are closed only through the high resistance signal bells c². The relays are
therefore not excited and the individual signal lamps remain unlighted.
Assume, to illustrate the operation of the system, that subscriber at station A
wishes to communicate with subscriber at station B. He removes his telephone
receiver c from its switch hook. Current theu finds circuit from battery h through
relay and the telephone at the substation; the relay draws its armature forward,
thus closing the branch circuit 3 and illuminating signal lamp n.
The operator
perceives this signal and inserts plug o' into the corresponding springjack d', at the
same time connecting her telephone set u with the plug circuit 6, 7, by means of
listening key t. The operator is thus placed in telephonic communication with the
subscriber at station A, the circuit being through line conductors 1 and 2,
contacts ff of the springjack, and portions of the conductors 6 and 7 of the plug
circuit. She is thus in position to learn his order for the connection required.
By the insertion of the plug into the springjack the contact piece p² is brought
into connection with the contact ring f2 of the springjack, thus closing together
conductor 5 terminating in the springjack and conductor 8 terminating in the plug,
and completing the circuit through the signal v. The two conductors 3 and 5-8,
including the individual signal n and the clearing-out signal v, respectively, are thus
brought into parallel connection with each other in the local circuit including
conductor 4 and resistance coil m. The current through the resistance coil, which
is sufficient to light a single lamp, is now distributed to the two lamps so that
neither of these is illuminated. That is, when the plug is inserted into the spring-
jack, the individual signal is extinguished, while the clearing-out signal remains.
still unlighted.
When the operator has learned the order of subscriber at station A, she inserts
plug o into the springjack 2 of line to station B. The branch 9 terminating in
plug ol is now closed to the conductor 5 terminating in springjack d², and the local
circuit is completed through the lamp signal vl. It will be noted, however, that the
line-circuit 10-11, of this line includes only the signal bell at station B, the
telephone receiver being still on the switch hook; so that relay of that line is not
excited and the circuit through its individual signal is not complete. Hence the
signal receives its full normal current and is illuminated. If the circuit were
closed through the telephone at the substation, the branch circuit 3 through the
individual. lamp signal would be closed and lamp would of course not be.
illuminated. It may be noted here also that if a connection already existed with
the same line-as for example. if a plug were inserted in springjack d³ at section e of
the switchboard-a branch 9 through a clearing-out signal would be already
connected to conductor 5 terminating in the springjack d³ so that when the operator
inserted plug o¹ into jack d the necessary condition for preventing the illumination
of the lamps would be fulfilled-that is, two branches including lamp signals would
be placed in parallel connection. Thus the lamp signal would remain unlighted
neither of two events, namely, if the subscriber at substation B had already
emoved his telephone from its switch hook, or if a connection already existed
vith the line at another section of the switchboard, whether the substation
pparatus were in use or not. The illumination of the signal lamp al upon the
nsertion of plug o' into jack d' thus constitutes an automatic test signal and signifies

page_text: "
to the operator that the line is not in use. The line,tests," busy to operators,
desiring to make connection with it from the moment the subscriber removes his
telephone from, its switch hook, while the required connection exists with the line,
and until the connecting plug is finally withdrawn from the springjack.
Assuming that the operator finds the line to station B free, she manipulates the
calling key r and thus transmits to station B a signalling current which rings the
bell c². When the subscriber at that station, in response to this signal, removes its
telephone from its switch hook, the signal v is extinguished. The operator is thus
assured that the calling subscriber is in communication with his correspondent at
station B, without the necessity of making any oral inquiry.
When either subscriber-as subscriber at station A-replaces his telephone upon
its switch hook, the line relay in the corresponding line releases its armature and
thus interrupts the branch 3 through the individual signal. The full current
through conductor 4 is now diverted through conductors 5 and 8 and the clearing-
out signal vis illuminated. In practice the operator does not disturb the connection
until both clearing-out signals and v¹ have become thus illuminated, which indicates
that the subscribers have completed their conversation and both have replaced their
telephones. She then removes the connecting plugs from the springjacks of the
united lines.
•
It is obvious that numerous other arrangements of the signal lamps might be
made by which they could be brought into parallel circuit with each other during
connection with the line and by which one or the other should be caused to give
a signal.
'
In Figure 2 the invention is illustrated with some modifications from the
foregoing description.
The resistance R¹ R2 at the respective substations is added to the ringer circuit
instead of the ringer itself being of high resistance.
In the central office apparatus a cord switch is provided for the testing plug
controlling the connection of the operator's telephone with the listening key whereby
an operator is enabled to answer a number of calling subscribers one after the other
quickly and taking their orders and completing the connections successively at her
convenience. It will be clear that with the cord switch as shown in the diagram,
the listening key may be left in position to connect the telephone with the plug
circuit, but the connection between the telephone and the plug circuit will be
completed only when the testing plug is raised.
In the arrangement shewn at Figure 2 each lamp is mounted in a small tube, in
the front of which a plano-convex lens of opal glass is placed. This lens serves two
purposes: one is, to disperse the light from the lamp, so that the signal can be seen
from the side as well as from the front; the other is, to prevent the red glow of
the filament when both lamps are in parallel from being seen and mistaken for a
signal.
The tube is mounted in a rubber strip carrying contact springs in such a way
that any tube with its lamp can be quickly removed and replaced by another in
case of failure of the lamp.
It is preferred to place each line lamp over the corresponding answering jack,
the answering jacks being mounted teu on a strip; the two clearing out signals
belonging to a pair of plugs are placed in the key shelf'in front of and in line with
the plugs which they represent..
The relay is a tubular magnet with a disc armature which is brought to an edge
at its periphery, the disc resting on this edge in an angular groove formed between
the end of the tubular magnet and a shoulder in the cap. When the armature is
attracted it closes against an insulated contact stud which projects from the end of
the magnet core. The resistance of the relay is about five. hundred ohms. It is
preferred to branch it from one side of the line to ground, and to balance the line
with an impedance coil of about the same, resistance in a ground branch from the
other line conductor. The impedance coil and the relay magnet may be enclosed in
the same tubular shell, making the shell longer to accommodate both, and separating

page_text: them by an iron partition. The relays are to be placed at any convenient point
outside or in the switchboard.
A condenser is connected in one strand of the cord circuit, the strand which.
unites the sides of the lines from which the relays are branched-to render the two
lines independent of each other as far as continuous currents in their circuits are
concerned; that is, to prevent the replacement of the telephone at one substation:
from operating both line relays.
The operation of the system may be briefly traced as follows:- -The subscriber,
at a station removes his telephone from its switch, whereby the lamp signal over the;
answering jack is lighted, the operator inserts an answering plug in the answering
jack, by which the line lamp signal is extinguished, the clearing-out signal
corresponding to the plug remaining unlighted. She lifts the testing plug, whereby
her telephone is connected with the plug circuit, and receives the subscriber's
order; she tests in the usual way and inserts the testing plug into the springjack of
the subscriber called for, and simultaneously rings and disconnects her telephone.
by means of the key. When the testing plug was inserted into the called,
subscriber's line jack, the clearing out signal associated with the testing plug was
lighted because the line relay of the called subscriver had not closed the circuit
through his line lamp. Then the called subscriber, responding to the ring, removes
his telephone from the hook, the clearing out signal associated with the test plug is
extinguished. As long as conversation is carried on both clearing-out signals.
remain unlighted. When either telephone is hung up the corresponding signal
lights; when both telephones have been replaced on their switches both signals are
illuminated and the operator, understanding that conversation has been terminated,.
removes the connection.
In Figure 3 a modification is shewn in which the system of automatic signalling:
at the exchange is utilised whilst the substation apparatus at present in general use.
is left unchanged, with its ordinary polarised bell and generator. The line relay
which is connected with the circuit at the exchange in place of the self restoring
drop has a small coil on it which is connected in circuit with the line lamp signal.,
When the generator is operated, the armature of the relay is attracted, and closes
the local circuit including the line lamp signal and the auxiliary low resistance coil
on the relay core. The relay is then permanently excited and holds its armature
until the line resistance coil and the lamp are shunted by inserting a plug in the
springjack. A single clearing out signal is connected with the plug circuit; this
signal is a lamp controlled by a relay constructed like the line relay and operated
by the "ring off" current from the generators. The local circuit of the lamp is
closed only while the plugs are in use by a cord switch controlled by the answering
plug.
This system provides apparatus which can readily be changed over, from, a
magneto system with lamp signals to an automatic signalling system with lamp
signals; the springjacks, relays, lamps, plugs, keys and cord switches all remaining
the same.
71.
.
J. E. KINGSBURY.
Improvements in Telephone Systems.
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 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 telephone systems and provides improved means for the

page_text: transmission of signals from the substation of a telephone line to the telephone
switch board at an exchange and improvements in the switchboard apparatus and
methods, also the adaptation of the switchboard improvements to the existing
methods of signalling with a magneto generator at the substation.
The invention involves the use of annunciators or signals which are adapted to
'be operated or excited by a predetermined normal current, but to remain inert
when traversed by a current materially less, as for example by half of the normal
.current. In practice incandescent lamps are found to be suitable signals of this
type, being illuminated by a suitable current but remaining unlighted when
traversed by half of this current.
Two such signals are according to this invention arranged in parallel branches.
of a local circuit and the continuity of one of the branches is controlled by a relay
responding to currents in the telephone line. The signal in the branch controlled
by the relay is designed to act as an individual signal and is permanently associated
with a particular line; the other signal may be associated with one of the plug
-circuits provided for uniting different telephone lines, and the branch including it
may be normally open, terminating in a contact piece in the connecting plug
adapted to complete the branch wbile the plug is in use in a springjack.
In the normal condition of the apparatus at the switchboard the individual
signal is free to respond to currents in the corresponding line circuit caused by the
completion or interruption of the line circuit at the substation, and thus by its
display may indicate an initial or call signal from the substation. When, however,
in response to such a signal connection has been made with the line, the other of
the two branches is closed through the clearing out or disconnection signal, whereby
the indication of the individual signal is effaced, the clearing out signal remaining
-inert. The signals remain in this condition until the relay, responding to an
-altered condition of the line circuit, opens the branch including the individual.
signal, whereby the clearing out signal is excited.
In one form of apparatus arranged according to this invention the substation of
each telephone line is provided with a switch, preferably an automatic telephone
switch, by which the normally open line circuit may be closed during the use of
the telephone at the substation; and in the switchboard at the central station a
relay and a source of current are included in the line circuit, the contact points of
the relay being adapted, when the relay is excited, to complete the branch of the
.before mentioned local circuit which includes the individual signal corresponding to
the line. The interrupted portions of the other branch of the local circuit
terminate, respectively, in a contact piece in each of the springjacks of the line,
and in a corresponding contact piece upon the connecting plug which is designed
to be inserted in the springjack to establish connection with the line. The source
of current in the local circuit is common to the different pairs of plugs in the
-switchboard, and these are, therefore, interchangeable with respect to their use in
different springjacks; hence any plug may be used in connection with any spring-
jack without interfering with the operation of the associated clearing out signal.
In a switchboard system thus organized the removal of the telephone from the
switch hook at a substation causes the excitement of the relay in that line at the
central station, and thus operates or excites the corresponding individual signal in
the switchboard. The operator thereupon inserts a plug into the springjack,
effacing the indication of the individual signal; the clearing-out signal still remains
inert, since the current in the local circuit is divided between the two signals.
When, however, the telephone at the substation is replaced upon its switch-hook,
the circuit of the line is interrupted, the relay is no longer excited, and it interrupts
the branch of the local circuit including the individual signal thus diverting the
full current through the clearing-out signal and causing the latter signal to be
-displayed.
If a connecting plug be inserted in a line which is free, that is, which is not
already in use, the clearing-out signal remains excited until the substation telephone
is brought into use, since the circuit through the individual signal of the corre-

page_text: sponding line is interrupted until that time; but if a plug be inserted into a spring
jack of a line whose telephone is already in use, or with which a connection
already exists, either one or two branches of the local circuit will have been.
already completed, so that the clearing-out signal of the plug last inserted into a.
springjack of the line will remain inert. The condition of the clearing-out signal
therefore constitutes a "test" which signifies the free or "busy" condition of the
line with which connection is made.
In a multiple switchboard the test thus becomes automatic and is indicated by a:
suitable visible signal.
In Figure 1 of my Provisional Specification two substations A and B are shown,.
each connected through line conductors with springjacks upon different sections of
a multiple switchboard, and with a relay controlling an individual signal. The
apparatus at the substations comprises a receiving telephone c and a transmitting
telephone c', a signal bell c³, and an automatic switch c³ arranged to close the line.
circuit alternately through the telephonic and signalling appliances.
The apparatus of substation A is connected by line conductors 1 and 2 with two-
springjacks d and d¹ upon different sections e and e' of a multiple switchboard at.
the central station-the different line conductors terminating in different line
contacts fand, respectively, in each of the springjacks. The conductor 1 of the
line is extended through an impedance coil to one pole of a battery h, while
conductor 2 is connected with the other pole of battery i, a line relay i being:
included in the conductor.
The battery and relay i are so adjusted to the resistance in the line circuit.
that when the circuit is closed through the 'bell c', which should be of high
resistance, the relay is not appreciably excited; while when the circuit is closed at.
the substation through the telephone the relay shall attract its armature.
The contact points of relay i are included in a branch 3 of the local circuit 3, 4,.
of a battery 1, a resistance coil m being connected in the local circuit.
The branch 3 includes also the individual signal lamp n which is associated with.
the springjack in the switchboard. Each springjack is provided with a contact.
ring 2, the different contact rings being connected together through a wire 5 which.
is connected with the conductor 4 of the local circuit.
Connecting plugs o and of are provided for looping different telephone lines.
together by means of their springjacks. Each plug contains two contact pieces p.
and p' which are adapted to make connection with the line contacts and f1 of the
springjack, and another contact piece p³ which is arranged to connect with the
ring of the springjack. The contact pieces p of the two plugs are connected
together through a conductor 6, and the pieces p' by another conductor 7. Each.
of these conductors includes a condenser, the condensers being designated q and q¹
respectively. The conductors 6 and 7 extend through the switch contacts of a.
calling key r, by means of which a generator s of signalling current may be looped
into connection with the plug o', and branches from them are led to the switch.
springs of a listening key t for connecting the operators telephone u with the plug.
circuit.
The contact piece p² of plug o constitutes the terminal of a conductor 8 including
the clearing-out signal lamp v which is associated with that plug; contact piece p².
of plug o similarly constitutes the terminal of another conductor 9 including lamp.
signal associated with plug o'. Conductors 8 and 9 extend directly to the local
battery 1.
The drawing represents the apparatus in its normal or idle position. The
telephones at the substations rest upon their switch hooks, so that the line circuits
are closed only through the high resistance signal bells c. The relays i are there-
fore not excited and the individual signal lamps remain unlighted.
Assume, to illustrate the operation of the system, that subscriber at station A.
wishes to communicate with subscriber at station B. He removes his telephone
receiver c from its switch-hook. Current then finds circuit from battery h through.
relay i and the telephone at the substation; the relay draws its armature forward,

page_text: thus closing the branch circuit 3 and illuminating signal lamp n. The operator
perceives this signal and inserts plug o into the corresponding springjack d¹, at the
same time connecting her telephone set u with the plug circuit 6, 7, by means of
listening key t. The operator is thus placed in telephonic communication with the
subscriber at station A, the circuit being through line conductors 1 and 2,
contacts ff of the springjack, and portions of the conductors 6 and 7 of the
plug circuit. She is thus in position to learn his order for the connection required.
By the insertion of the plug into the springjack the contact p³ is brought into
connection with the contact ring 2 of the springjack, thus closing together
conductor 5 terminating in the springjack and conductor 8 terminating in the plug
and completing the circuit through the signal t. The two conductors 3 and 5-8,
including the individual signal n and the clearing out signal v, respectively, are thus
brought into parallel connection with each other in the local circuit including
conductor 4 and resistance coil m. The current through the resistance coil,
which is sufficient to light a single lamp, is now distributed to the two lamps
so that neither of these is illuminated. That is, when the plug is inserted into
the springjack, the individual signal is extinguished while the clearing out signal
remains still unlighted.
When the operator has learned the order of subscriber at station A, she inserts
plug o into the springjack d² of line to station B. The branch 9 terminating in plug ol
is now closed to the conductor 5 terminating in springjack d² and the local circuit is
completed through the lamp signal v¹. It will be noted, however, that the line
circuit 10-11 of this line includes only the signal bell cat station B, the telephone
receiver being still on the switch hook; so that relay of that line is not excited
and the circuit through its individual signal is not complete. Hence the signal v
receives its full normal current and is illuminated.
If the circuit were closed through the telephone at the substation, the branch
circuit 3 through the individual lamp signal would be closed and lamp would of
course not be illuminated. It may be noted here also that if a connection already
existed with the same line-as for example if a plug were inserted in springjack d³
at section e of the switchboard a branch 9 through a clearing-out signal would be
already connected to conductor 5 terminating in the springjack d³ so that when the
operator inserted plug o! into jack d² the necessary condition for preventing the
illumination of the lamps would be fulfilled that is two branches including lamp
signals would be placed in parallel connection. Thus the lamp signal would
remain unlighted in either of two events namely, if the subscriber at substation B
had already removed his telephone from its switch hook or if a connection already
existed with the line at another section of the switch board whether the substation
apparatus were in use or not. The illumination of the signal lamp v¹ upon the
insertion of plug e¹ into jack d² thus constitutes an automatic test signal and
signifies to the operator that the line is not in use. The line tests "busy to
operators desiring to make connection with it from the moment the subscriber
removes his telephone from its switch hook, while the required connection exists with
the line, and until the connecting plug is finally withdrawn from the springjack.
Assuming that the operator finds the line to station B free, she manipulates the
calling key r and thus transmits to station B a signalling current which rings the
bell c³. When the subscriber at that station, in response to this signal removes its
telephone from its switch hook, the signal is extinguished. The operator is thus
assured that the calling subscriber is in communication with his correspondent at
station B, without the necessity of making any oral enquiry.
"
When either subscriber-as subscriber at station A, replaces his telephone upon
its switch hook, the line relay in the corresponding line releases its armature and
thus interrupts the branch 3 through the individual signal.
The full current
through conductor 4 is now diverted through conductors 5 and 8 and the clearing
out signal vis illuminated. In practice the operator does not disturb the connection
until both clearing out signals v and v¹ have become thus illuminated which indicates
that the subscribers have completed their conversation and both have replaced.

page_text: their telephones. She then removes the connecting plugs from the springjacks of
the united lines.
It is obvious that numerous other arrangements of the signal lamps might be
made by which they could be brought into parallel circuit with each other during
connection with the line and by which one or the other should be caused to give a
signal.
In Figure 2 of my Provisional Specification the invention is illustrated with
some modifications from the foregoing description.
The resistance R' R' at the respective sub stations is added to the ringer circuit
instead of the ringer itself being of high resistance.
In the central office apparatus a cord switch is provided for the testing plug
controlling the connection of the operator's telephone with the listening key whereby
an operator is enabled to answer a number of calling subscribers one after the
other quickly and taking their orders and completing the connections successively
at her convenience. It will be clear that with the cord switch as shown in the
diagram, the listening key may be left in position to connect the telephone with
the plug circuit, but the connection between the telephone and the plug circuit
will be completed only when the testing plug is raised. As the drawing shews the
testing plug when out of use and placed into its resting socket holds open spring
contacts in the circuit to the telephone but when the test plug is withdrawn from
its resting socket then the circuit of the telephone is completed through the
listening key.
If the operator cannot at once attend to the order received she can restore the
test plug to its resting socket without altering the listening key contacts and
afterwards complete the connection required when able to do so.
The listening key having been left in position so as to bring the line. contact
spring into connection with the telephone circuit the act of putting the test plug
into or withdrawing it from its resting socket controls the putting of the operator's
telephone into or out of circuit with the line.
In the arrangement shewn at Figure 2 each lamp is mounted in a small tube, in
the front of which a plano convex lens of opal glass is placed. This lens serves
two purposes; oue is, to disperse the light from the lamp, so that the signal can be
seen from the side as well as from the front; the other is to prevent the red glow
of the filament when both lamps are in parallel from being seen and mistaken for
a signal.
The tube is mounted in a rubber strip carrying contact springs in such a way
that any tube with its lamp can be quickly removed and replaced by another in
case of failure of the lamp.
It is preferred to place each line lamp over the corresponding answering jack,
the answering jacks being mounted ten on a strip; the two clearing out signals
belonging to a pair of plugs are placed in the key shelf in front of and in line with
the plugs which they represent.
Figures 4, 5, 6 and 7 shew the lamp on a larger scale and also the rubber strip
by which a number of the lamps are carried. a is the rubber strip, a contact
springs carried by the strip. yy are the lamps each fitting into a socket in the
strip. is a groove cut in the strip, this allows of hooks or catches at the ends
of spring arms of a tool such as shewn at Figure 8 being made to catch below the
head of any lamp to facilitate the withdrawing of any lamp from its socket.
The relay shewn in Figure 2 is a tubular magnet with a disc armature which is
brought to an edge at its periphery, the disc resting on this edge in an angular
groove formed between the end of the tubular maguet and a shoulder in the cap.
When the armature is attracted it closes against an insulated contact stud which
projects from the end of the magnet core. When not attracted it drops away by
gravity from this contact. The resistance of the relay is about five hundred ohms.
It is preferred to branch it from one side of the line to ground, and to balance
the line with an impedance coil of about the same resistance in a ground branch
from the other line conductor. The impedance coil and the relay magnet may
B

page_text: be enclosed in the same tubular shell, making the shell longer to accommodate both,
and separating them by an iron partition. The relays are to be placed at any
convenient point outside or in the switchboard.
A condenser is connected in one strand of the cord circuit, the strand which
unites the sides of the lines from which the relays are branched-to render the
two lines independent of each other as far as continuous currents in their circuits
are concerned; that is, to prevent the replacement of the telephone at one
substation from operating both line relays.
The operation of the system may be briefly traced as follows:-The subscriber
at a station removes his telephone from its switch, whereby the lamp signal over the
answering jack is lighted, the operator inserts an answering plug in the answering
jack, by which the line lamp signal is extinguished, the clearing out signal
corresponding to the plug remaining unlighted. She lifts the testing plug, whereby
if the listening key contacts are properly placed, her telephone is connected with
the plug circuit, and she receives the subscriber's order; she tests in the usual
way and inserts the testing plug into the springjack of the subscriber called for,
and simultaneously rings and disconnects her telephone by means of the key.
When the testing plug was inserted into the called subscriber's line jack, the
clearing out signal associated with the testing plug was lighted because the line
relay of the called subscriber had not closed the circuit through his line lamp.
Then the called subscriber, responding to the ring, removes his telephone from the
hook, the clearing out signal associated with the test plug is extinguished. As
long as conversation is carried on both clearing out signals remain unlighted.
When either telephone is hung up the corresponding signal lights; when both
telephones have been replaced on their switches both signals are illuminated and
the operator, understanding that conversation has been terminated, removes the
connection.
In Figure 3 of my Provisional Specification, a modification is shewn in which
the system of automatic signalling at the exchange is utilised whilst the sub-station
apparatus at present in general use is left unchanged, with its ordinary polarised
bell and generator. The line relay which is connected with the circuit at the
exchange in place of the self restoring or other drop hitherto used has a small coil
on it which is connected in circuit with the line lamp signal. When the generator
is operated, the armature of the relay is attracted, and closes the local circuit
including the line lamp signal and the auxiliary low resistance coil on the relay
The relay is then permanently excited and holds its armature until the line
resistance coil and the lamp are shunted by inserting a plug in the springjack.
A single clearing out signal is connected with the plug circuit; this signal is a lamp
controlled by a relay constructed like the line relay and operated by the "ring
off"
current from the generators. The local circuit of the lamp is closed only
while the plugs are in use by a cord switch controlled by the answering plug.
core.
This system provides apparatus which can readily be changed over, from a
magneto system with lamp signals to an automatic signalling system with lamp
signals; the spring-jacks, relays, lamps, plugs, keys and cord switches all remaining
the same.
Figure 9 shews an arrangement substantially the same as Figure 3 except that
no cord switch is operated by the test plug and the relays are different in form.
In the arrangement shewn at Figure 9 the mechanism provided at the
subscriber's station comprises the usual telephone receiver and transmitter, signal
bell, and generator of signalling current a³, together with a switch arranged to
support the telephone and constructed to close the circuit alternately through the
telephone instruments and the signalling appliances. The line circuit, consisting
of direct and return conductors 1, and 2, connects this apparatus with springjacks b
and in a multiple telephone switch board of two sections, and includes the
helix" d of a relay e located at the central station. The armature d' and contact
anvil of this relay control the continuity of a local circuit 3, which extends
serially through an auxiliary magnet helix d³ on relay e, a signal-lamp f, a resistance
line

page_text: coil g, and a battery h. The signal-lamp ƒ is located in any convenient position in
the switchboard where it may be under the supervision of the attendant, preferably
near the springjack 6' of the line on section c¹ of the switchboard. A. suitable
lamp may have a resistance of ten ohms. The resistance of magnet helix d³ should
be comparatively low, in order to avoid waste of energy in the local circuit, five
ohms being sufficient. The resistance of coil g may also be ten ohms. The electro-
motive force of battery h should of course be sufficient to cause the illumination of
signal-lamp when the relay contacts are closed.
The springjack which constitutes the terminal of the line in each section of the
switchboard is of well known construction. It comprises two springs i and i', which
are connected with line conductors 1 and 2, respectively, and a contact ring or
thimble. The thimbles of the different springjacks are united by a conductor 4,
which is connected with the local circuit 3 at a point intermediate of the lamp and
the resistance coil.
The connecting plug employed is constructed with three contact pieces k, kl,
and 2, which are adapted to register with the different contact pieces i, 1, and 2,
of a springjack into which a plug may be inserted. The contact pieces k and the
contact pieces of two plugs and are united by two conductors 5 and 6 which
constitute the "plug circuit." These conductors include the switch-contacts of a
calling key m, which is adapted to disconnect the plug from plug 7 and to loop
into circuit with the former a source of calling current n, for the purpose of signal-
ling a subscriber. Conductors 5 and 6 are connected with the switch-contacts of a
listening key also, which acts, when depressed, to bridge the operator's telephone
set p across the plug circuit. A conductor 7 is led from the central point of the
resistance in the magnet helix of the telephone receiver p' to a point on circuit 3
intermediate of the battery h and the resistance coils g, to provide means for testing,
as will be hereafter described.
The line coil d of a "clearing-out relay" g is permanently connected in a bridge &
between conductors 5 and 6. The switch contacts d¹ d² of this relay control the
continuity of another local circuit 9, which likewise includes an auxiliary magnet d³
on the relay, a signal-lamp r, and a battery. The same battery his employed, the
local circuit 9 being placed in parallel with the local circuit 3 about the battery.
The continuity of this circuit 9 is further controlled by a plug-seat-switch s in the
resting socket of plug 1, the plug-seat-switch being arranged to close the circuit
when the plug is withdrawn from its socket. The contact pieces ³ of the two plugs
are grounded through conductors 10 and 11, respectively.
In the normal condition of the apparatus, the telephones at the different sub-
stations rest upon their switch hooks, and no currents exist in the line circuits.
The armatures of the relays are retracted from their contact points. The local
circuits are open, and the different line-signals are inert or unilluminated.
plugs of the different pairs of cords provided for each operator rest in their sockets
whereby the different circuits 9 are interrupted.
The
+
To illustrate the operation of the system, assume that subscriber at station A
desires to have his line connected with station B. The subscriber at the former
station operates his generator a³ of signalling current in the usual way, thus creating
in the line circuit 1-2 a current which traverses the line magnet d of relay e.
The relay is excited and closes the local circuit 3. The current of battery h of this
local circuit illuminates the signal lamp f associated with the springjack of that
line ou switchboard c, and at the same time further excites the relay e; so that
after the cessation of the signalling current in the line circuit the relay still holds
its armature and maintains the illumination of lampf. The attendant at section c¹
of the switchboard, observing the signal, raises plug / from its socket and inserts it;
into the spring jack 6. The raising of the plug from its socket permits the plug-
seat-switch s to close one break in the local circuit 9, thus leaving this circuit with
its clearing-out signal lamp controlled only by the relay q. The insertion of plug &
into the springjack extends the line conductors 1, 2, to the conductors 5, 6, of the
plug circuit through the medium of the registering contacts of the springjack and
!

page_text: the plug; at the same time a ground connection is completed from ring through
contact piece and conductor 10 terminating therein, which constitutes a shunt or
short circuit about the lamp f, the contact points of relay e, and the magnet d³ of
the relay. The lamp fis thus extinguished, and the magnetizing helix d³ becomes
inert and permits the armature of the relay to fall away from its contact.
The operator connects her telephone set with the plug circuit by means of key o
in the usual manner, and, having thus established communication with the subscriber
at station A, learns his order. She tests the line to station B in the usual way-
that is, by applying the tip of plug to the thimble or ring of springjack b³. If
the line be not in use, no difference of potential exists between the tip of the plug
and the ring of the springjack, since these constitute the terminals of open circuits
whose other terminals are connected with the same pole of battery h—the rings
being the open terminals of the circuit 4, 3, and the tip of the plug being the
terminal of a circuit through conductor 6 to the listening key and thence through
the operator's telephone receiver and conductor 7 to the battery h. If the line
were in use, the ring of springjack 63 would be grounded through conductor 10
or 11 of the plug circuit by means of which the connection with it was established,
and battery would find a circuit through the tip of the plug to earth at each
application of the plug to the test ring i².
Finding the line free for the desired connection, she inserts plug into the
springjack 63 and operates the key m to ring the bell at sub-station B as usual.
The insertion of the plug into the springjack creates a short circuit about the
lamp signal and the magnet d of relay e, by means of the conductor 11 connected
with the plug, in a manner similar to that established about the signal and relay
magnet of the other line. Hence, although a portion of the signalling current
traverses the line magnet of relay e, the line signal lamp f¹ is not illuminated. It
will be understood that the signal lamp f¹ may be upon any section of a multiple
switchboard, and that its illumination by a signalling current sent to operate the
substation bell would constitute a false signal, which would mislead the operator
having supervision of the signal lamp.
When the subscribers have terminated their conversation, either, subscriber may
transmit a signal for disconnection, by turning his generator a³ of signalling current.
The current thus created in the line finds circuit to the plug circuit 5, 6, and thence
through the line magnet d of the clearing-out relay q. This relay becomes excited
and closes the local circuit 9, illuminating the clearing-out signal lamp r and thus
indicating the signal to the attendant. The continued excitement of the relay,
after the cessation of the signalling current, is attained as before by the magnetisin
of helix d³. In response to the signal, the operator removes the plugs from the
springjacks into which they are inserted and returns them to their resting sockets.
The plug-seat-switch interrupts the local circuit 9, the relay magnet becomes
inert, and the mechanism of the clearing-out device is returned to its normal
condition.
It will be noted that the relay e is not excited at the moment of withdrawal of
plug from springjack 61, so that it remains in its normal position in readiness to
indicate a subsequent line signal.
I do not desire to limit myself to any particular mode of producing current in
the line circuit for the purpose of exciting the relay, or to the location of the
source of current at the substation, since the invention may be easily adapted to
different systems involving various sources of current supply for signalling.
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 with a line relay in a telephone line, responding to currents
in the line, of a local circuit; two signal lamps in parallel branches of the local
circuit, one of the branches including the contact pieces of the line relay, and
means for interrupting the other branch, substantially as described.

page_text: 2. The combination with a telephone line, of a relay responding to currents in
the line, a local circuit including a resistance coil and a line signal lamp associated
with a spring-jack of the line, controlled by the relay, a clearing-out signal-lamp,
and means for connecting the clearing-out signal lamp in a shunt about that portion
of the local circuit which includes the relay and the line signal lamp, substantially
as described.
3. The combination of a switchboard, telephone lines extending therefrom, a
relay in each line at the switchboard station actuated by a signal current passed
through the line and then closing a local circuit which includes a source of current,
a line signal on one side of the relay and a resistance on the other side, and a
branch circuit extending from between the resistance and the relay to the spring
jacks of the line and through a connecting plug and clearing out signal back to
the source of current-the source of current and resistance being so proportioned
that either signal responds when traversed by the full current but does not respond
when both are traversed by the current.
4. A telephone system arranged substantially as hereinbefore described and
illustrated in Figure 1 of the drawings annexed.
5. In a testing device for multiple switchboards, a series of contact pieces in the
different springjacks of a line, electrically connected together, a
source of
determinate current connected with these contact pieces, means for applying a
shunt about the source of current when connection is made with the line, a testing
instrument adapted to respond when traversed by the full current of said source,
and means for applying the testing instrument to the test contact of any spring
jack to bring it into shunt of the source of current, whereby the presence of a
shunt about the said source may be determined.
6. In a testing device for multiple switchboards, a series of test contacts in the
different springjacks of a line, electrically connected together, a battery permanently
connected through a resistance coil with the said test contacts, a conductor leading
from the free pole of the said battery, means for connecting the said conductor to
the test contacts when connection is made with the line, and a testing device
adapted to respond to the full current through said resistance coil in a similar
conductor adapted to be applied to any test contact, whereby the presence of the
shunt may be detected.
st
7. In a testing device for multiple switchboards, the combination with
contacts in the different springjacks of a line, of a source of current permanentiy
connected through a resistance coil with the test contacts, a connecting plug and a
contact piece therein adapted to register with said test contacts and forming the
terminal of a conductor connected with the free pole of said battery, another
connecting plug and a similar contact piece therein, a signal lamp in the conductor
terminating in the said contact piece, said lamp being adapted to be illuminated by
the full current through the resistance coil, whereby the presence of an existing
connection is automatically indicated when the last mentioned connecting plug is
inserted into the spring jack.
8. In a testing device for multiple switchboards, the combination with the
springjacks, of a series of test contacts therein, a source of current adapted to give
a current of determinate volume permanently connected with the test contacts, a
shunt circuit about said source of current, and a relay responding to currents in the
telephone line controlling the shunt, other shunt circuits terminating in the different
connecting plugs so as to be applied when connection is made with any springjack,
a testing instrument adapted to respond only to the full current from said source,
and a conductor including the testing instrument connected with the free pole of
the battery and adapted to be applied to any test contact, whereby the presence of
an existing connection and currents in the telephone line both cause the line to
test busy.
9. The arrangement of a cord switch operated by the test plug or its cord and
controlling the connection between the operators telephone and the listening key
substantially as described.

page_text: 10. A telephone signal incandescent lamp mounted within a tube carrying &
plano convex lens of opal glass at its front end substantially as described.
11. The combination of the bar or strip having a number of sockets formed in it
each to receive a tube carrying an incandescent signal lamp and carrying contact
springs for each lamp substantially as described.
12. The construction of relays substantially as described and illustrated in
Figures 2 and 3.
13. The combination with an electric circuit and means for producing a current
therein, of a relay in the circuit, a local circuit controlled by the relay to be closed
when the relay is excited, including a subsidiary signal, and an auxiliary magnet-
helix on the relay connected with the local circuit to receive current when the
local circuit is closed, whereby the subsidiary signal is caused to be permanently
excited by a momentary current in the line circuit.
14. The combination with a telephone line, of means for producing a signalling
current in the line, a relay in the line circuit responding to such current, a local
circuit including a subsidiary line signal and a source of current adapted to be
closed when the relay is excited, an auxiliary magnet helix adapted when excited
to maintain the continuity of the local circuit, said auxiliary magnet being
connected with the local circuit to receive current when the circuit is closed, and
means for interrupting the current through the auxiliary magnet, substantially as
.described.
15. The combination with a telephone line, of means for producing a signalling
current in the line, and a relay in the circuit responding to such current, a local
circuit including a subsidiary line signal controlled by the relay, an auxiliary helix
on the relay in the local circuit, means for establishing connection with the line,
and switch contacts actuated in the establishment of such connection adapted to
interrupt the current through the said auxiliary helix, substantially as described.
16. The combination with a telephone line and means for producing signalling
current therein, of a relay in the line circuit, a local circuit including a subsidiary
line-signal, and a source of current, controlled by the relay, an auxiliary magnet-
helix on the relay in the local circuit, springjacks and connecting plugs for making
connection with the line, and a normally open short-circuit about the auxiliary
helix and the subsidiary line-signal, and co-operating contacts in the plug and
springjack adapted to close the short-circuit substantially as described.
17. The combination with a telephone line and means for producing signalling
current therein, of a relay in the line circuit, a local circuit including a subsidiary
line-signal controlled by the relay, an auxiliary magnet-helix on the relay, included
in the local circuit, spring jacks connected with the line and a connecting plug
adapted to be inserted therein, and a normally open short-circuit about the
subsidiary signal and the auxiliary magnet-helix terminating in registering contacts
in the spring jack and connecting plug..
18. The combination with a plug-circuit adapted to be temporarily connected
with the telephone line, of a relay having a line magnet connected with the plug
circuit, a local circuit including a subsidiary signal controlled by the relay, an
auxiliary magnet-helix on the relay included in the local circuit, and a plug-seat-
switch for one of the connecting plugs adapted to open the local circuit while the
plug is in its seat, substantially as described.
19. A telephone system arranged substantially as described and illustrated at
Figure 2.
20. A telephone system arranged substantially as described and illustrated at
Figures 3 and 9.
J. E. KINGSBURY.