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 boards for telephone exchanges; its
primary object is to provide means whereby the individual annunciator shall be
prevented from being operated while a connection exists to the line, without
disconnecting the annunciator from the line; whereby the inclusion of contact
points in the line circuit, or in the brauch thereof containing the annunciator, may
be avoided.
A further object of the invention is to provide a system for telephone exchanges
employing metallic line circuits, which shall require no branches or connections
common to the different lines or cord circuits.
The invention may be described generally as comprising an annunciator having
two electro-magnets or helices arranged to act differentially upon an armature
common to both, adapted to operate an indicator when actuated, and circuit con-
nections including one of said electro-magnets in the line circuit or in a branch
thereof and the other in a branch from one side of the line circuit to a contact
piece adapted to be connected to the other side thereof when a connection is
made to line, whereby the two helices are placed in parallel when the connection
is made.
In this invention, spring-jacks are employed each having two line-springs of
different lengths, and a test-ring insulated therefrom, or other equivalent pieces.
One spring-jack for cach line is placed upon each section of multiple switch board.
Corresponding line-springs of all the jacks of one line are connected together, the
different line-springs being connected to the different sides of the line circuit
respectively. The test-rings of all the jacks of a line are connected together. In
the practical construction of the individual annunciator, the two electro-magnets
may be of the tubular pattern, arranged with their axes in the same line, with
their poles facing each other, and the armature may be placed between their
abutting ends, and normally resting near to or in contact with one of them.
A suitable arm carrying a catch may be attached to the armature, and a shutter
provided engaging with the catch and adapted to be released by the motion in a
certain direction of the armature. Thus one of the helices when energized tends to
release the shutter, while the other when energized tends to prevent the motion
of the armature. The former coil I designate the "operating coil" and the latter
the "retaining coil."
The operating coil of this annunciator is included in a bridge wire connecting the
two sides of the line circuit; the retaining coil is included in a branch from that
line which is connected to the shorter line-spring, to the test ring.
The connecting plug employed in this invention is provided with a tip adapted
to make contact with the shorter line-spring of a jack into which it is inserted,
and a sleeve adapted to cross together the longer line-spring and the test-ring.
In the operation of the system, when a call signal is sent from a sub-station, the
current finds circuit through the operating coil of the annunciator, thus releasing
the shutter and indicating the signal to the attending operator. The attendant
inserts a plug in the spring-jack of that line at her board, in the usual manner, in
order to make connection from the line to her telephone.

page_text: The operator receives the number desired, and proceeds to establish connection
between the calling line and the called line in the usual manner.
If now a subsequent calling signal, as the clearing out signal, be sent from the
sub-station, the current divides at the long line spring of the jack at which con-
nection is established, a part passing through each path therefrom to the other
side of line, each of which paths includes one coil of the annunciator; and since
these coils are arranged to act differentially upon their armature, the annunciator
is not operated.
A part also of the current is shunted through the cord circuit, and traverses the
clearing-out annunciator therein, thereby operating that annunciator and notifying
the operator that the lines may be disconnected.
The conditions of the answering line are the same as those of the calling line.
Any signalling current sent from the answering station, or any reaching to its lines
from the calling line through the medium of the connecting cords, divides at the
spring-jack in which a plug is inserted, the two portions traversing both coils of its
annunciator and thus failing to operate it.
In keeping with the second object of this invention, a test system adapted to it
is provided having no ground connection. The said test system consists in a source
of telephonic undulatory current in a bridge connection between the two contact
pieces of the connecting plugs, the operator's telephone being also in a similar
parallel bridge. Normally a slight continuous noise is thereby produced in the
operator's telephone.
The test whereby any operator is enabled to determine whether any line is in
use or not, consists in the insertion of one connecting plug into the jack at her
board of the line to be tested, until the tip of the plug makes contact with the
longer line-spring of the jack. If the line be in use, if there be a connecting plug
in some other jack, the testing plug will be short circuited by the plug and contact
pieces of that other jack, and the noise in the telephone will cease, thus indicating
to the testing operator the condition of the line tested. This system of testing
is not limited to use in connection with this invention, and has been made the
subject of a separate application.
The invention is illustrated in the accompanying drawing, and may be more
clearly understood by reference thereto.
In the drawing I have shewn two substations connected by lines with their
respective spring jacks upon two different switch-boards, each line having an
annunciator at one of the boards. Two sets of connecting cords and plugs are
shewn, with the operator's telephone sets, connected with each.
One set of cords is shewn connecting the two telephone lines, and the other as in
the act of testing one of the lines.
The apparatus at the substation, for example station 1, consists as usual of the
telephone a, and transmitter a' in a branch from one side of line, a call bell a², and
calling generator a³ in another branch, and a switch a' connected to the other side
of line adapted to connect the telephone set or the signalling apparatus into
the line.
Line wires bb, extend from the substation to the exchange or central station,
where they are connected respectively to the longer and to the shorter line-
springs cc, of two spring jacks d d', upon two different switch boards e e', and to
the two terminals of the operating helix, of an individual annunciator g: a branch
from the line 6, includes the retaining coil of the annunciator, and is connected
to the conductor joining the test rings h of the spring-jacks d d'.
Both coils of the individual annunciator are made of high retardation, so that
they do not shunt any appreciable portion of the rapidly undulating telephone
current upon the lines."
The line circuit from station 2 is shewn as grounded; the line 65 being continued
through the earth instead of being an unbroken metallic conductor, by grounding
the portions at the substation and at the central station.

page_text: The like contact pieces of the connecting plugs i, i, are joined. by con-
ductors kk.
Keys of well known construction are included in the circuit between the two
plugs, each adapted to disconnect both contact pieces of one plug from those of the
other, and to connect them to the poles of a calling generator_m, when the
plunger n is depressed. Another key o is provided, adapted to connect
the operator's telephone set p in a bridge connection between the conductors k, k²,
when its plunger q is depressed.
The secondary of an induction coil is included in a parallel circuit with the
telephone set p; its primary is included in a local circuit with a battery s and a
microphone t adjusted very lightly and kept in continuous slight vibration by
suitable means.
"
The vibrating microphone renders the current through the primary of induction
coil
undulatory, and the undulations are reproduced by the secondary and
impressed upon its circuit. This secondary of the coil constitutes the "source of
undulatory current," herein before described in connection with the test system.
It normally finds circuit through the telephone p and. produces a slight continuous
noise therein.
Calling current sent from station 1, finds circuit only through the coil of the
individual annunciator g; the annunciator is thereby operated and the signal indi-
cated to the operator at board e¹. The operator inserts a plug into the jack d'
of that line at her board, and depresses the plunger of her listening key o, thereby
connecting her telephone p with the calling line.
Having received the order, say for a connection with station 2, she proceeds to
test that line to determine whether it is already in use or not, by inserting the
connecting plug of the pair into the jack until the tip makes contact with the
longer line spring c.
The plug at board e is shewn as in the act of testing the jack at that board.
It will be seen by examination of the apparatus of that set of plugs, that if the
line tested be busy, that is, if a plug be in any jack of the line, as is actually shewn
in the drawing, the secondary of induction coil is short circuited through the tip
of plug, to the line spring c of jack 2, thence by conductor to spring c of jack d³,
thence through the sleeve of plug to the test ring, then to the test ring h
of jack d, thence to the sleeve of plug 3 returning to the other terminal of coil r.
The undulating current of coil is thus wholly shunted from the telephone, and
the noise therein ceases. The cessation of this noise is thus the indication that
the line tested is in use.
Assuming, however, that the operator at board el finds the line 62ª not in use,
she inserts the other plug entirely into jack d³ whereby the two subscribers are
placed in communication: the circuit being from station 1 over line to spring cof
jack thence by sleeve of plug i, through ringing key l, conductor k, ringing
key to sleeve of plug, thence to spring c, thence by conductor 62 to station 2,
thence returning by conductor to central station, to line-spring c¹ of jack d³,
thence to tip of plug thence again through ringing key conductor ringing
key to tip of plug i, thence to line-spring c¹, to line 1, returning to station 1.
The operator now sends calling current to station 2 by depressing the plunger
of key. A large part of this current traverses the lines 62, 63, and operates, the
bell a at station 2; a portion is shunted at the sleeve of plug i', passing to the
test ring, through conductor to coil f¹ of the annunciator, thence to the line 63,
returning to tip of plug, and another small portion is shunted directly through
coil of the annunciator; but the two coils, being simultaneously energized,
produce no effect upon the armature, to actuate it.
The calling signal having been sent, and the subscriber at station 2 having
responded, the operator disconnects her telephone from the lines by allowing the
plunger 9 to rise.
When the conversation between the subscribers is finished, one or both, we will
suppose only one subscriber at station 1 sends a clearing out signal from his.

page_text: generator. This current divides at the line spring c of jack d', a portion passes
thence through each of the coils of annunciator g, to the line 6, thus failing to
operate the annunciator; another portion passes by the connection cords k¹ to
the clearing out annunciator u operating it and indicating the signal to the operator.
Still another portion passes over conductors kk to the jack and thence dividing
as before, through both coils ff of the annunciator.
Thus I am enabled to insure that while the individual annunciator of .an
unconnected line will be perfectly responsive to calling signals sent over that line,
neither individual annunciator of two connected lines will respond to any signalling
current sent over either line subsequent to the connection.
Further, when metallic circuits are employed, there exists no necessity; in this
improved system, for any connection or branch common to the different lines of the
exchange, either during separation or connection.
I do not, desire, however, to limit myself to the employment of any particular
test system in connection with this invention. Any of several well known test
systems might readily be applied to this switch board system, by any one skilled in
the art.
'
Dated this 5th day of March 1802
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE 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 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 boards for telephone exchanges; its
primary object is to provide means whereby the individual annunciator shall be
prevented from being operated while a connection exists to the line, without
disconnecting the annunciator from the line; whereby the inclusion of contact
points in the line circuit, or in the branch thereof containing the annunciator, may
be avoided.
A further object of the invention is to provide a system for telephone exchanges
employing metallic line circuits, which shall require no branches or connections
common to the different lines or cord circuits.
The invention may be described generally as comprising an annunciator having
two electro-magnets or helices arranged to act differentially upon an armature
common to both, adapted to operate an indicator when actuated, and circuit
connections including one of said electro magnets in the line circuit or in a branch
thereof and the other in a branch from one side of the line circuit to a contact
piece adapted to be connected to the other side thereof when a connection is made
to line, whereby the two helices are placed in parallel when the connection is
made.
In this invention spring-jacks are employed each having two line-springs of
different lengths, and a test-ring insulated therefrom, or other equivalent pieces.
One spring-jack for each line is placed upon each section of multiple switch board.
Corresponding line-springs of all the jacks of one line are connected together, the
different line-springs being connected to the different sides of the line circuit
respectively. The test rings of all the jacks of a line are connected together.
In the practical construction of the individual annunciator, the two electro-magnets
may be of the tubular pattern, arranged with their axes in the same line, with
their poles facing each other, and the armature may be placed between their
abutting ends.and normally resting near to or in contact with one of them.

page_text: A suitable arm carrying a catch may be attached to the armature, and a shutter
provided engaging with the catch and adapted to be released by the motion in a
certain direction of the armature. Thus one of the helices when energized tends
to release the shutter, while the other when energized tends to prevent the motion
of the armature. The former coil I designate the "operating coil" and the latter
the "retaining coil."
The operating coil of this annunciator is included in a bridge wire connecting the
two sides of the line circuit; the retaining coil is included in a branch from that line
which is connected to the shorter line spring, to the test ring.
The connecting plug employed in this invention is provided with a tip adapted
to make contact with the shorter line-spring of a jack into which it is inserted,
and a sleeve adapted to cross together the longer line-spring and the test-ring.
In the operation of the system, when a call signal is sent from a sub-station, the
current finds circuit through the operating coil of the annunciator thus releasing
the shutter and indicating the signal to the attending operator. The attendant
inserts a plug in the spring-jack of that line at her board in the usual manner, in
order to make connection from the line to her telephone.
The operator receives the number desired, and proceeds to establish connection
between the calling line and the called line in the usual manner.
If now a subsequent calling signal, as the clearing out signal be sent from the
sub-station, the current divides at the long line spring of the jack at which con-
nection is established, a part passing through each path therefrom to the other
side of line, each of which paths includes one coil of the annunciator; and since
these coils are arranged to act differentially upon their armature, the annunciator
is not operated.
A part also of the current is shunted through the cord circuit, and traverses the
clearing out annunciator therein, thereby operating that annunciator and notifying
the operator that the lines may be disconnected.
The conditions of the answering line are the same as those of the calling line.
Any signalling current sent from the answering station, or any reaching to its lines
from the calling line through the medium of the connecting cords, divides at the
spring-jack in which a plug is inserted, the two portions traversing both coils of its
annunciator and thus failing to operate it.
In keeping with the second object of this invention, a test system adapted to it
is provided having no ground connection. The said test system consists in a source
of telephonic undulatory current in a bridge connection between the two contact
pieces of the connecting plugs the operator's telephone being also in a similar
parallel bridge. Normally a slight continuous noise is thereby produced in the
operator's telephone.
The test whereby any operator is enabled to determine whether any line is in
use or not, consists in the insertion of one connecting plug into the jack at her
board of the line to be tested, until the tip of the plug makes contact with the
longer line-spring of the jack. If the line be in use, if there be a connecting plug
is some other jack, the testing plug will be short circuited by the plug and contact
pieces of that other jack, and the noise in the telephone will cease, thus indicating
to the testing operator the condition of the line tested.
The invention is illustrated in the accompanying drawing, and may be more
clearly understood by reference thereto.
In the drawing left with the Provisional Specification I have shewn two sub-
stations connected by lines with their respective spring jacks upon two different
switch boards, each line having an annunciator at one of the boards. Two sets of
connecting cords and plugs are shewn, with the operator's telephone sets, connected
with each.
One set of cords is shewn connecting the two telephone lines, and the other as in
the act of testing one of the lines.
The apparatus at the substation, for example station 1, consists as usual of the

page_text: telephone a and transmitter a¹ in a branch from one side of line, a call bell a², and
calling generator a³ in another branch, and a switch a' connected to the other side
of line adapted to connect the telephone set or the signalling apparatus into
the line.
Line wires bb, extend from the substation to the exchange or central station,
where they are connected respectively to the longer and to the shorter line-
springs e c', of two spring jacks d d', upon two different switch boards e e¹, and to
the two terminals of the operating helix, of an individual annunciator g; a
branch from the line b¹, includes the retaining coil of the annunciator and is
connected to the conductor joining the test rings of the spring-jacks d d'.
Both coils of the individual annunciator are made of high retardation, so that
they do not shunt any appreciable portion of the rapidly undulating telephone
current upon the lines.
The line circuit from station 2 is shewn as grounded; the line 63 being continued
through the earth instead of being an unbroken metallic conductor, by grounding
the portions at the substation and at the central station.
The like contact pieces of the connecting plugs i, ¹, are joined by conductors kk'.
Keys of well known construction are included in the circuit between the two
plugs, each adapted to disconnect both contact pieces of one plug from those of
the other, and to connect them to the poles of a calling generator m, when the
plungern is depressed. Another key o is provided adapted to connect the
operator's telephone set in a bridge connection between the conductors k, k',
when its plunger q is depressed.
?'
The secondary of an induction coil is included in a parallel circuit with the
telephone set p its primary is included in a local circuit with a battery s and a
microphone t adjusted very lightly and kept in continuous slight vibration by
suitable means.
The vibrating microphone renders the current through the primary of induction
coil undulatory, and the undulations are reproduced by the secondary and
impressed upon its circuit. This secondary of the coil r constitutes the "source of
undulatory current," hereinbefore described in connection with the test system.
It normally finds circuit through the telephone p and produces a slight continuous
noise therein.
Calling current sent from station 1, finds circuit only through the coil fof the
individual annunciator g; the annunciator is thereby operated and the signal
indicated to the operator at board e¹. The operator inserts a plug i into the jack d
of that line at her board, and depresses the plunger of her listening key o, thereby
connecting her telephone p with the calling line.
Having received the order, say for a connection with station 2, she proceeds to
test that line to determine whether it is already in use or not, by inserting the con-
necting plug of the pair into the jack d³ until the tip makes contact with the
longer line spring c.
?'
The plug at board e is shewn as in the act of testing the jack d² at that board.
It will be seen by examination of the apparatus of that set of plugs, that if the
line tested be busy, that is, if a plug be in any jack of the line, as is actually shewn
in the drawing, the secondary of induction coil is short circuited through the tip
of plug, to the line spring c of jack 2, thence by conductor to spring c of jack d³,
thence through the sleeve of plug to test ring 7, then to test ring of jack da,
thence to the sleeve of plug returning to the other terminal of coil r. The
undulating current of coil is thus wholly shunted from the telephone, and the
noise therein ceases. The cessation of this noise is thus the indication that
the line tested is in use.
"'
Assuming, however, that the operator at board e¹ finds the line 62 63 not in use,
she inserts the other plug entirely into jack d³ whereby the two subscribers are
placed in communication: the circuit being from station 1 over line to spring e of
jack d¹ thence by sleeve of plug i, through ringing key 1, conductor k, ringing key l

page_text: to sleeve of plug i, thence to spring c, thence by conductor to station 2, thence
returning by conductor to central station, to line-spring cl of jack d³, thence to
tip of plug thence again through ringing key conductor ringing key to tip
of plug i, thence to line-spring e', to line returning to station 1.
The operator now sends calling current to station 2 by depressing the plunger of
key. A large part of this current traverses the lines, 3, and operates the
bell a at station 2, a portion is shunted at the sleeve of plug, passing to the test
ring, through conductor to coil " of the annunciator, thence to the line b³, returning
to tip of plug, and another small portion is shunted directly through coil of the
annunciator, but the two coils, being simultaneously energized, produce no effect
upon the armature, to actuate it.
The calling signal having been sent, and the subscriber at station 2 having
responded, the operator disconnects her telephone from the lines by allowing the
plunger q to rise.
When the conversation between the subscribers is finished, one or both, we will
suppose only one subscriber at station 1 sends a clearing out signal from his
generator. This current divides at the line spring of jack d', a portion passes
thence through each of the coils of annunciator g, to the line b', thus failing to
operate the annunciator, another portion passes by the connection cords & to the
clearing out annunciator u operating it and indicating the signal to the operator.
Still another portion passes over conductors kk' to the jack d³ and thence dividing
as before, through both coils of the annunciator.
Thus I am enabled to insure that while the individual annunciator of an uncon-
pected line will be perfectly responsive to calling signals sent over that line, neither
individual annunciator of two connected lines will respond to any signalling current
sent over either line subsequent to the connection.
Further, when metallic circuits are employed, there exists no necessity, in this
improved system, for any connection or branch common to the different lines of the
exchange, either during separation or connection.
I do not desire, however, to limit myself to the employment of any particular
test system in connection with this invention. Any of several well known test
systems might readily be applied to this switch board system, by any one skilled
in the art.
Having now particularly described and ascertained the nature of the 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 telephone line extending from a substation to a central
station, of spring jacks at the central station each having two line-springs of different
lengths and a test ring, the different line-springs of each jack being connected to
the different sides of line, and an individual annunciator having two electro magnets
arranged to act differentially upon a common armature adapted to operate an
indicator when actuated, one of said electro-magnets being included in a V branch
connection between the two sides of said line and the other electro-magnet being
included in a branch extending from the line connected to the shorter line-spring to
the test-ring substantially as described.
2. The combination with a telephone line extending from a substation to central
station, of spring-jacks at the central station each having two line springs and a
test ring, the corresponding line springs of each jack being connected together and
the different line-springs being connected to the different sides of line, an individual
annunciator having two electro-magnets arranged to act upon a common armature
adapted to operate an indicator when actuated, one of said magnets being adapted
to operate said armature when energized and being included in the line circuit or
in a brauch therefrom, and the other of said magnets being adapted to retain said
armature to render it unresponsive to the operating magnet and being included in

page_text: a branch connection from one of the line-springs to the test ring, and a connecting
plug inserted into a spring-jack, having a tip making contact with that line-spring
in immediate connection with the retaining coil, and a sleeve making contact with
the other line-spring and the test ring, whereby the annunciator is rendered
unresponsive to currents sent over the line when a plug is inserted in a jack of the
line, substantially as described.
3. In combination, two telephone lines extending from sub-stations to a central
station, spring-jacks at the central station connected with each line, each having
three different contact pieces two of said contacts being connected to the different
sides of the lines, individual annunciators each having two electro-magnetic helices
arranged to act differentially upon a common armature adapted to operate an
indicator when actuated, one of said electro-magnetic helices being included in the
line circuit of its line or a branch therefrom, and the other being included in a
branch from one side of its line to the third contact piece of the spring-jacks of its
line connecting plugs, each having two contact pieces one making contact with that
line contact which is connected through one annunciator coil to the third contact
piece, and the other making contact with the other line contact and said third
contact piece, one plug being inserted in a jack of each line, and connecting cords
joining corresponding contact pieces of the plugs, whereby the telephone lines are
joined into a continuous circuit and the two helices of the individual annunciators
of both lines are placed in parallel bridge connections between the different sides
of the complete circuit, substantially as described.
4. In combination two telephone lines extending from sub-station to a central
station, spring-jacks at the central station connected to each line, each spring-jack
having two line-springs of different lengths, and a test ring, corresponding line-
springs of each line being connected together and the different line-springs of cach
line being connected to the two sides of line respectively, conductors joining all the
test rings of each line, an individual annunciator for each line having two helices
arranged to act differentially upon an armature common to both adapted to operate
an indicator when actuated, one helix of each annunciator being included in a
bridge connection between the two sides of its line, and the other helix being
included in a branch from that side of its line which is connected to the shorter
line-spring to the test rings of the jacks of its line, connecting plugs, one in a jack
of each line, each having separate contact pieces making contact with the shorter
line-spring and with the longer line-spring and the test ring of the jack, conductors
joining like contact pieces of the two plugs, and a clearing out annunciator in a
bridge connection between the different contact pieces of the plugs, substantially
as described.
5. The combination with a telephone line extending from a substation to a central
station, of an individual annunciator at the central station provided with two
electro-magnets arranged to act in opposite directions upon an armature adapted to
operate an indicator when actuated, one of said electro-magnets being included in
the said line circuit or a branch thereof, and the other included in a branch from
one side of line to a contact piece adapted to be closed to the other side of said line
when a connection is made to the line, substantially as described.
6. The combination with a telephone line extending from a sub-station to a
central station, of an individual annunciator at the central station provided with
two electro-magnetic helices, said helices being arranged to act differentially upon
a common armature adapted to operate an indicator when actuated, one of said
electro-magnetic helices being included in the line circuit or in a branch therefrom,
and the other electro-magnetic helix being included in a branch connection from
one side of said line to a contact piece adapted to be connected to the other side
thereof when a connection is made to the line, substantially as described.
7. The combination with a line circuit extending from a sub-station to a central
station, of an individual annunciator having two electro-magnetic helices arranged
to act differentially upon an armature common to both, adapted to operate in

page_text: indicator when actuated, one of said helices being permanently connected in a
bridge connection between the two sides of the line circuit, and contact pieces and
circuit connections adapted to connect the other helix also in a bridge connection
between the two sides of line, whereby the second helix is alternately connected
5 and disconnected as the line is in use or not in use, substantially as specified.
Dated this 3rd day of December 1892.
J. E. KINGSBURY.