Apparatus to be employed at Telephonic Switch Boards.
Year: 1890

page_text: Date of Application, 10th Nov., 1890
Complete Specification Left, 8th Aug., 1891-Accepted, 12th Sept. 1891
PROVISIONAL SPECIFICATION.
Apparatus to be employed at Telephonic Switch Boards.
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 apparatus to be employed at telephonic switch
boards.
The general arrangement is shown at Figure 1. Three subscribers stations
are indicated at 1, 2 and 3, they are similar the one to the other but at station 2
no detail of the instruments is given. From each subscriber two line wires pass to
the central station.
The figure shows also instruments at the central station. I II and III are three
switch boards, there may be as many of these as are required, the attendant at each
switch board attending to the calls of a certain number of the subscribers.
Subscriber No. 1 appertains to switch board I, subscriber No. 2 to switch board II
and subscriber No. 3 to switch board III. At every switch board each subscriber
has a socket or "spring jack" adapted to receive a plug; thus the sockets
belonging to No. 1 are marked n³n n°. Each jack is provided with a contact
point for each line wire the contacts being insulated the one from the other.
Each subscriber also, but at his own switch board only, has a plug connected to
a flexible cord and an instrument called a "cord switch.' At switch board I the
plug belonging to No. 1 subscriber is seen standing in No. I's cord switch; this is
the normal position when the line is not in use. At switch board III the plug
belonging to No. 3 subscriber is seen in the socket n belonging to No. 1; it would
be so placed when the line is being prepared for No. 3 to speak with No. 1. In
this position the noze of the plug is electrically connected with one of No. 1 line
wires and the sleeve of the plug through the other contact with the other of
No. 1's line wires. Two insulated wires contained in the cord lead away from the
plug and are connected as shown; they pass down through the cord switch to
which the plug belongs.
Each subscriber also on his own switch board has an "annunciator" or indicator
which by the fall of a shutter shows when he calls; No. 1's annunciator is
marked and No. 3's is marked p². The test battery at the central office is
narked. The generator which originates the call currents is marked e.
elephones employed by the switch board operators are marked T.
I will now proceed to describe the cord switch in detail.
Figures 2, 3 and 4 are front, side and rear views of the cord switch.
Figures 5 and 6 are detailed views of certain portions thereof.
The
The frame a of a strip of cord switches may be of brass and is provided with
lug sockets and the common contact pieces bc; when this cord switch is used in
onnection with the system shown in Figure 1 the frame a is connected to ground
rough a test battery d; the contact is connected with the central office
enerator e; the contact strip c is connected with one side of the operator's
lephone while the spring which may be common to all the cord switches of one
pard is connected with the other side of the telephone.
The spring which may be connected with one limb of a circuit is adapted to
ose upon the telephone contact c while the spring h which may be connected with
e other limb of the metallic circuit is adapted to close upon spring f; this
ring is provided with a non metallic stud ¹ projecting towards spring « and

page_text: with a block of rubber ² which protrudes so as to be accessible from the front of
spring the spring is provided also with a bearing surface of insulating
material. These two springs and i are adapted to be changed in position by the
movement of a lever k which is adapted, as it is vibrated, to take the surface 2 of
spring in the first place and upon further movement to pass over the said surface
or projection h² and come against the surface of spring i. The lever / when
forced against the surface moves the spring i against the contact at the same
time separating said spring i from its contact with spring h; the surface is of
such form with respect to the end of the lever k coming against the same that on
letting go the handle of lever k the tension of spring i will carry the lever k back
into the notch in the bearing surface of insulating piece h².
A cord plug is provided with a metallic heel adapted to rest in the socket of its
cord switch and to force the spring i backward so as to separate the contact thereof
from spring hand at the same time the telephone contacts are opened; that is to
say, the spring g will be separated from contact c and spring f from its contact with
spring h.
It will be noted that the spring i when thus moved by the insertion of the plug
will come against the shoulder or base of the rubber block interposed between
said springs and i and that the force of spring i thus exerted upon spring h serves
to carry the contact of said spring away from its contact with spring and at the
same time the pressure of the stud against the spring g carries said spring g
away from its contact c.
Although the spring is moved by the insertion of the plug in its socket, as
above described, in a direction towards the generator contact the movement is not
sufficient to actually close this generator connection, such closing of the generator
contact being effected by the vibration of the lever to bring the working end
thereof against the surface i'. When, however, the arm k is tilted to press the
spring backwards the contacts of springs and i will be pressed together, the
stud will come against the spring g and hold the same separated from the con-
tact c while spring will be separated from spring h. When the springs of the
switch are in the position shown in Figure 3 the stud will be at a short distance
from the spring 9 say about one half the distance which the spring his moved when
the lever is tilted as shown at board 3, Figure 1 so that when the lever is thus
tilted the telephone contacts will stand open.
1 will now further describe the telephone line circuits in connection with the
operator's outfits and subscribers apparatus as shown in Figure 1. The subscriber's
outfits at stations 1 and 3 are shown somewhat in detail.
The subscriber's bell m is included in a normally closed ground branch; the
generator m² is included in the circuit when the telephone is on the switch as shown
at station 1, but is shunted when the telephone is removed from the switch as
shown at station 3. The telephone m² in like manner is included in the circuit
when off the hook and shunted therefrom when upon the hook.
The telephone line n of station 1 extends in two branches n¹ and n² to the central
office, the branch or limb n' passing through the springs and contacts of the
switches n³, n', no and from the contact of the switch on the last board to the tip of
the terminal plug n³ of the line. A branch n' including individual annunciator 8
extends at the central office as shown from limb n' to the spring of the cord
switch and thence when the plug n is resting in its socket as shown through the
metallic heel of said plug to the frame of the cord switch, and thence by branch n³
through the battery d to ground. The limb n² is connected as shown with the test
pieces of switches n³ n', no and extends thence to the spring of the switch and
thence by spring i when the two springs are in contact to the sleeve of the plug nº.
Thus it will be seen normally the two limbs of the circuit are open at the central
office except that a connection is made by a bridge or branch from limb n
through the annunciator, spring i of the cord switch, the ring or metallic piece
upon the plug, the frame of the switch, connection n' and battery d to ground.
Telephone line o of station 2 is connected in like manner by limbs o¹ o² through

page_text: the switches 03, 0%, o³ of the different boards and through similar cord switch
apparatus at board 2 which I have not deemed it necessary to illustrate.
Station 3 is connected by line p in branches p' p² in like manner with
switches p³ and thence with the terminal plug and the cord switch at
5 board 3.
At board 3 I have shown telephone line p in connection with telephone line
the cord switch at board 3 being in position to maintain contact between springs
and i and thus to maintain closed the connection between the test rings of line p
and the strand of the cord connecting with the sleeve of the plug, while at the
() same time the annunicator p is bridged across the united circuit of the two lines
and the operator's telephone circuit is disconnected.
At board 1 I have shown the plug nº resting in its socket in its normal position.
I will now describe somewhat in detail the manner of calling the central office,
answering the call, testing the line called for, completing the connections and
5 clearing out and disconnecting the lines.
Subscriber at station 3 by operating his generator will send current over limb pl
through the annunciator p and thence through the spring of the switch at board 3
and, when the plug is in its socket, through its metallic heel and thence through
the frame of the cord switch to ground through battery d. The operator seeing
the shutter of annunciator p fall will lift plug from its socket, the simple act of
lifting this plug bringing her telephone into connection with line p.
It will be noted that the circuit first formed is from ground at the subscriber's
station through the branch containing the bell to the subscriber's switch, thence
through the generator and thence over the limb of the circuit containing the
circuits and contacts of the switches to the branch containing the individual
annunciator and thence through the cord switch to ground as before traced. On
lifting the plug from the socket the telephone is brought into circuit and the
ground circuit through the test battery is opened; the operator while thus holding
the plug which has been lifted receives the order for some other line; in this
instance the order was for the line n of subscriber 1. The operator having
received the order applies the plug to the test piece of the switch of this line, that
is, to the test piece of switch no. Now if the line is free when the test is made
battery circuit will be closed from the test battery d to test piece of switch n³,
thence to the tip or sleeve of plug l, we will say the tip, and thence to the spring g
of the cord switch and thence through half the coil of the telephone to ground.
The test circuit which is thus formed when the line is free will be understood
by tracing the test circuit of line n, the cord switch and operator's telephone outfit
of said line being shown in detail. Thus tracing from ground through battery d
the battery will find circuit over branch n' to the frame a of the cord switch and
thence through the metallic portion of the plug n to spring i thereof and thence by
branch n to limb n¹ and thence through the contacts and springs of switches n³ n' n³
over said limb n' through the generator and thence to the telephone switch at
tation 1, and thence back over limb n² to the test portion of the line. It will be
oted that the bell m is in a ground branch connected with the metallic circuit and
ence its resistance will divert current over the limb n³.
Now the test being made by plug 1 at switch n³ and the line being found free the
perator will insert plug into switch n as shown, this completing the connection
etween the two lines P and n.
In order to signal sub-station 2 the operator pulls
orward the handle of lever k to cause the foot or presser of said lever to take the
rface, thus forcing spring i into contact with the generator connection b, while
the same time contact between springs i and his broken. When thus forced
gainst the generator contact the current from the generator will be directed to the
rand of the cord of plug connecting with the sleeve thereof and thence over
mb n² to the telephone switch at station 1 and thence through the subscriber's
ll to ground.
When the generator is thus closed to line the contact between
rings and
is broken as is desirable to prevent ringing in both directions and
e current is sent over the limb o' through the subscriber's bell to ground.

page_text: The generator of the subscriber which is included in the limb n¹ will prevent
current from being diverted through the annunciator p to the strand of the cord
connecting with the tip of the plug and thence through limb n' and generator m' in
sufficient quantity to operate said annunciator p.
The call having been thus sent the operator will release the lever k which will
be carried back by the force of the spring i so as to take the notch in the piece 2.
In this position the telephone will be disconnected from the circuit, the generator
contact will be opened while the circuit will be closed between springs h
and i.
When the subscribers have finished talking and the telephones are restored to
their hooks one or the other operates his generator, thus throwing down the shutter
of annunciator which is bridged into the circuit when the contact between
springs and i is closed as just described.
Now the generator of the subscriber who does not send the clearing out signal
being included directly in the circuit it is evident that its resistance and retardation
will act to cause more current to be diverted through the bridge containing the
annunciator p so that the current through the annunciator will be sufficient to
operate the same.
The clearing out signal being thus received the operator will withdraw plug
from switch n and return it to the socket of its cord switch, the act of restoring the
plug to its socket serving to bring the lever k back to its normal position.
I will now describe a modification of the cord switch.
Figure 7 is a front elevation of an operator's cord switch.
Figure 8 is a side elevation thereof, partly in section.
Figure 9 is a rear elevation thereof.
Figure 10 is a plan in section on the line X-X of Figure 8.
Figure 11 is an underside view.
Figure 12 is a perspective view of a portion of the apparatus.
Figure 13 is a perspective view of another portion.
Figure 14 is a side elevation of the switch with the parts in another position.
The springs C D F G assume different relations to one another according as the
plug (which is not represented in these figures) is in the socket A or removed from
the same and according to whether the knob or handle H is upright or drawn
forward to the position shewn in Figure 14. The springs C D, the contact piece E
and the springs F G will be separated from one another when the plug is in
place.
When the plug is removed and the handle of the plunger H upright as in
Figure 2 the springs CD and G will come into contact with one another and at
the same time the spring F will close upon contact piece E..
The tension of the springs is such that such changes will take place simply on
removing the plug from the socket. This results from the fact that the contact
piece E forms, as it were, a stop for the springs C D F G the tension of these
springs being so adjusted that their free ends normally press in the same direction,
that is to say, towards the contact E.
Sometimes it is required to separate the contacts except that between the
springs CD, that is to say, to separate spring G from contact with the springs C D
and to separate the spring F from contact without separating or disconnecting
the springs CD. Such a result is accomplished as shewn in Figure 14 by throwing
the handle H forward so as to bring the arm I against the incline plane or bevelled
block K provided upon said spring D, thus forcing the spring D over away from
spring G.
The rubber stud D¹ between spring D and spring F, presses the spring F away
from contact E, at the same time spring D is carried away from spring G, thus
two of the three pairs of contacts are open and one pair permitted to remain
closed, that is to say, that between the springs C D.
or
As shewn in Figures 12 and 13 the spring C is provided with an opening
slot L through which the block K protrudes; this block constitutes an inclined

page_text: bearing surface upon spring D and on this surface the arm I abuts when the
plunger or handle H is thrown over to the position shown in Figure 14.
For calling or signalling, the springs shewn in Figure 7 are provided. The
outer springs M M' may be considered as connected with the two sides of the
generator or source of electricity. The springs N N₁ may be considered as
connected with the different strands of the cord of a loop plug inserted in the switch
of a line into which it desired to loop the calling generator. Spring () may
be considered as connecting with the line of the subscriber who has called and over
whose line it is desirable to prevent the signalling current from being sent.
Now it will be observed that the end of the plunger is in such relation to the
springs N N¹ that when the plunger is forced down spring N¹ will be separated
from spring O and closed to spring M; thus the generator if connected with
springs M M' will be looped into the cords, that is to say, into the metallic circuit
of the line wanted.
It will be observed that the plunger H is supported_in a pivotted guide piece P.
This guide piece having the extension or arm 1. Now it matters not in what
position this guide picce P may be, that is, whether in the position shown in
Figure 14 tilted to bear against the block K on spring D, or whether upright as
shewn for example in Figure 8. In either of these positions the plunger H may
be forced down to operate the springs N N for any purpose desired.
Figures 15, 16, 17 and 18 represent another modification.
Figure 15 is a front elevation.
Figure 16 is a side elevation.
Figure 17 is a rear elevation.
Figure 18 is a detail view shewing the manner of tilting the plunger to throw
on the ground branch containing the annunciator when the plug is lifted from the
socket.
These cord switches are conveniently built up in strips. Thus the metallic or
brass portions A. A and B B of the frame of a strip may be insulated from one
another by a strip of rubber C C the base D D of this frame may be of insulating
material, and is of sufficient width to support the springs and contacts on the
opposite sides of the frame. The plunger is mounted upon a metallic guide
pivotted to the metallic portion B B of the frame, this metallic guide is provided
with an arm consisting of two parts, one portion of the arm being preferably of
insulating material of some substance that will have little friction with the metallic
spring against which it acts; the other or lower portion thereof being of metal and
adapted to be brought into electrical connection with the spring when the guide is
tilted.
Dated this 8th day of Naramban 1000
J. E. KINGSBURY.
COMPLETE SPECIFICATION.
Apparatus to be employed at Telephonic Switch Boards.
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 apparatus to be employed at telephonic switch boards
and is illustrated by the drawings left with the Provisional Specification.
The general arrangement is shewn at Figure 1. Three subscribers stations are
indicated at 1, 2 and 3, they are similar the one to the other but at station 2 no
detail of the instruments is given. From each subscriber two line wires pass to
the central station.
The figure shows also instruments at the central station.
I II and III are three

page_text: switch boards, there may be as many of these as are required, the attendant at
each switch board attending to the calls of a certain number of the subscribers.
Subscriber No. 1 appertains to switch board I, subscriber No. 2 to switch board II
and subscriber No. 3 to switch board III. At every switch board each subscriber
has a socket or "spring jack" adapted to receive a plug; thus the sockets
belonging to No. 1 are marked n³ n' n³. Each jack is provided with a contact
point for each line wire the contacts being insulated the one from the other.
Each subscriber also, but at his own switch board only, has a plug connected to
a flexible cord and an instrument called a "cord switch. At switch board I the
plug belonging to No. 1 subscriber is seen standing in No. 1's cord switch; this is
the normal position when the line is not in use. At switch board III the plug
belonging to No. 3 subscriber is seen in the socket n' belonging to No. 1; it would
be so placed when the line is being prepared for No. 3 to speak with No. 1. In
this position the noze of the plug is electrically connected with one of No. 1 line
wires and the sleeve of the plug through the other contact with the other of
No. 1's line wires. Two insulated wires contained in the cord lead away from the
plug and are connected as shown; they pass down through the cord switch to
which the plug belongs. Each subscriber also on his own switch board has an
"annunciator" or indicator which by the fall of a shutter shows when he calls;
No. 1's annunciator is marked 18 and No. 3's is marked pº. The test battery at
the central office is marked d. The generator which originates the call currents
is marked e. The telephones employed by the switch board operators are
marked T.
I will now proceed to describe the cord switch in detail.
Figures 2, 3 and 4 are front, side and rear views of the cord switch.
Figures 5 and 6 are detailed views of certain portions thereof.
The frame a of a strip of cord switches may be of brass and is provided with plug
sockets and the common contact pieces c; when this cord switch is used in
connection with the system shown in Figure 1 the frame a is connected to ground
through a test battery d; the contact b is connected with the central office
generator the contact strip c is connected with one side of the operator's
telephone while the spring which may be common to all the cord switches of one
board is connected with the other side of the telephone. The spring a which may
be connected with one limb of a circuit is adapted to close upon the telephone
contact c while the spring which may be connected with the other limb of the
metallic circuit is adapted to close upon spring; this spring his provided with a
non metallic stud ¹ projecting towards spring g and with a block of rubber /²
which protrudes so as to be accessible from the front of spring i; the spring i is
provided also with a bearing surface of insulating material. These two springs h
and i are adapted to be changed in position by the movement of a lever & which is
adapted, as it is vibrated, to take the surface 2 of spring in the first place and
upon further movement to pass over the said surface or projection 2 and come
against the surface i of spring i. The lever k when forced against the surface i
moves the spring against the contact at the same time separating said spring i
from its contact with spring h; the surface i¹ is of such form with respect to the end
of the lever & coming against the same that on letting go the handle of lever k the
tension of spring i will carry the lever k back into the notch in the bearing surface
of insulating piece /².
The cord plug is provided with a metallic heel adapted to rest in the socket of its
cord switch and to force the spring i backward so as to separate the contact thereof
from spring hand at the same time the telephone contacts are opened; that is to
say, the spring g will be separated from contact c and spring f from its contact with
spring h.
It will be noted that the spring when thus moved by the insertion of the plug
will come against the shoulder or base of the rubber block 2 interposed between
said springs and i and that the force of spring i thus exerted upon spring serves
to carry the contact of said spring / away from its contact with spring and at the
h

page_text: pressure of the stud h' against the spring g carries said spring away
from its contact c.
Although the spring i is moved by the insertion of the plug in its socket, as
above described, in a direction towards the generator contact the movement is not
5 sufficient to actually close this generator connection, such closing of the generator
contact being effected by the vibration of the lever to bring the working end
thereof against the surface i¹. When, however, the arm kis tilted to press the
spring backwards the contacts of springs h and i will be pressed together, the
stud will come against the springy and hold the same separated from the contacte
while spring will be separated from spring h. When the springs of the switch are
in the position shown in Figure 3 the stud 4 will be at a short distance from the
spring y say about one half the distance which the spring is moved when the
lever kis tilted as shown at board 3 Figure 1, so that when the lever is thus tilted
the telephone contacts will stand open.
I will now further describe the telephone line circuits in connection with the
operator's outfits and subscribers apparatus as shown in Figure 1. The subscriber's
outfits at stations I and 3 are shown somewhat in detail.
The subscriber's bell is included in a normally closed ground branch; the
generator mis included in the circuit when the telephone is on the switch as
shown at station I, but is shunted when the telephone is removed from the switch
as shown at station 3. The telephone n² in like manner is included in the circuit
when off the hook and shunted therefrom when upon the hook.
The telephone line n of station I extends in two branches ¹ and n² to the central
office, the branch or limb n passing through the springs and contacts of the
switches n³ ³ ³ and from the contact of the switch on the last board to the tip of
the terminal plug n³ of the line. A branch n' including individual annunciator n³
extends at the central office as shown from limb n' to the spring i of the cord
switch and thence when the plug n is resting in its socket as shown through the
metallic heel of said plug to the frame of the cord switch, and thence by branch ³
through the battery d to ground. The limb 2 is connected as shown with the test
pieces of switches n³n n³ and extends thence to the spring of the switch and
thence by spring i when the two springs are in contact to the sleeve of the plug nº.
Thus it will be seen normally the two limbs of the circuit are open at the central
office except that a connection is made by a bridge or branch n from limb n'
through the annunciator, spring i of the cord switch, the ring or metallic piece upon
the plug, the frame of the switch, connection n° and battery d to ground.
Telephone line o of station 2 is connected in like manner by limbs o¹ 02 through
the switches 03 04 05 of the different boards and through similar cord switch
apparatus at board which I have not deemed it necessary to illustrate.
Station 3 is connected by line p in branches p' p² in like manner with
switches p p p and thence with the terminal plug and the cord switch at
board 3.
At board 3 I have shown telephone line p in connection with telephone line n,
the cord switch at board 3 being in position to maintain contact between springs h
and i and thus to maintain closed the connection between the test rings of line p
and the strand of the cord connecting with the sleeve of the plug, while at the same
ime the annunciator p is bridged across the united circuit of the two lines and the
perator's telephone circuit is disconnected.
At board I have shown the plug n resting in its socket in its normal position.
I will now describe somewhat in detail the manner of calling the central office,
nswering the call, testing the line called for, completing the connections and
learing out and disconnecting the lines.
Subscriber at station 3 by operating his generator will send current over limb pl
hrough the annunciator p' and thence through the spring i of the switch at board 3
nd, when the plug is in its socket, through its metallic heel and thence through
he frame of the cord switch to ground through battery d. The operator seeing

page_text: the shutter of annunciator p³ fall will lift plug I from its socket, the simple act of
lifting this plug bringing her telephone into connection with line p.
It will be noted that the circuit first formed is from ground at the subscriber's
station through the branch containing the bell to the subscriber's switch, thence
through the generator and thence over the limb of the circuit containing the
circuits and contacts of the switches to the branch containing the individual
annunciator and thence through the cord switch to ground as before traced. On
lifting the plug from the socket the telephone is brought into circuit and the
ground circuit through the test battery is opened; the operator while thus holding
the plug which has been lifted receives the order for some other line; in this
instance the order was for the line n of subscriber 1. The operator having received
the order applies the plug to the test piece of the switch of this line, that is, to the
test piece of switch Now if the line is free when the test is made battery
circuit will be closed from the test battery d to test piece of switch no, thence
to the tip or sleeve of plug 1, we will say the tip, and thence to the spring g
of the cord switch and thence through half the coil of the telephone to ground.
The test circuit which is thus formed when the line is free will be understood by
tracing the test circuit of line n, the cord switch and operator's telephone outfit of
said line being shown in detail. Thus tracing from ground through battery d the
battery will find circuit over branch n' to the frame a of the cord switch and thence
through the metallic portion of the plug to spring i thereof and thence by
branch n to limb n' and thence through the contacts and springs of switches n³ n¹ n³
over said limb through the generator and thence to the telephone switch at
station 1, and thence back over limb n to the test portion of the line. It will be
noted that the bell m is in a ground branch connected with the metallic circuit and
hence its resistance will divert current over the limb ².
Now the test being made by plug at switch n³ and the line being found free the
operator will insert plug into switch n as shown, this completing the connection
between the two lines
and n.
p
In order to signal sub-station 2 the operator pulls
forward the handle of lever k to cause the foot or presser of said lever to take the
surface, thus forcing spring i into contact with the generator connection b, while
at the same time contact between springs i and his broken. When thus forced
against the generator contact the current from the generator will be directed to the
strand of the cord of plug connecting with the sleeve thereof and thence over
limb to the telephone switch at station 1 and thence through the subscriber's bell
to ground. When the generator is thus closed to line the contact between springs i
and his broken as is desirable to prevent ringing in both directions and the current
is sent over the limb o² through the subscriber's bell to ground. The generator of
the subscriber which is included in the limb n¹ will prevent current from being
diverted through the annunciator to the strand of the cord connecting with the
tip of the plug and thence through limb n¹ and generator m² in sufficient quantity to
operate said annunciator p.
The call having been thus scut the operator will release the lever k which will be
carried back by the force of the spring i so as to take the nctch in the piece h. In
this position the telephone will be disconnected from the circuit, the generator
contact will be opened while the circuit will be closed between springs and i.
When the subscribers have finished talking and the telephones are restored to
their hooks one or the other operates his generator, thus throwing down the shutter
of annunciator 2 which is bridged into the circuit when the contact between
springs and is closed as just described.
Now the generator of the subscriber who does not send the clearing out signal
being included directly in the circuit it is evident that its resistance and retardation
will act to cause more current to be diverted through the bridge containing the
annunciator p so that the current through the annunciator will be sufficient to
operate the same.
The clearing out signal being thus received the operator will withdraw plug

page_text: ping to res socket serving to bring the lever back to its normal position.
I will now describe a modification of the cord switch.
Figure 7 is a front clevation of an operator's cord switch.
Figure 8 is a side elevation thereof, partly in section.
Figure 9 is a rear elevation thereof.
Figure 10 is a plan in section on the line X-X of Figure 8.
Figure 11 is an underside view.
Figure 12 is a perspective view of a portion of the apparatus.
Figure 13 is a perspective view of another portion.
Figure 14 is a side elevation of the switch with the parts in another position.
The springs C D F G assume different relations to one another according as the
plug (which is not represented in these figures) is in the socket A or removed from
the same and according to whether the knob or handle H is upright or drawn
forward to the position shewn in Figure 14. The springs CD, the contact piece E
and the springs F G will be separated from one another when the plug is in place.
When the plug is removed and the handle of the plunger H upright as in
Figure 2 the springs CD and G will come into contact with one another and at
the same time the spring F will close upon contact piece E.
The tension of the springs is such that such changes will take place simply on
removing the plug from the socket. This results from the fact that the contact
piece E forms, as it were, a stop for the springs C D F G the tension of these
springs being so adjusted that their free ends normally press in the same direction,
that is to say, towards the contact E.
Sometimes it is required to separate the contacts except that between the
springs CD, that is to say, to separate spring G from contact with the springs CD
and to separate the spring F from contact E without separating or disconnecting
the springs CD. Such a result is accomplished as shewn in Figure 14 by throwing
the handle H forward so as to bring the arm I against the incline plane or bevelled
block K provided upon said spring D, thus forcing the spring D over away from
spring G.
The rubber stud D' between spring D and spring F, presses the spring F away
from contact E, at the same time spring D is carried away from spring G, thus two
of the three pairs of contacts are open and one pair permitted to remain closed, that
is to say, that between the springs C D.
As shewn in Figures 12 and 13 the spring C is provided with an opening or
slot L through which the block K protrudes; this block constitutes an inclined
bearing surface upon spring D and on this surface the arm I abuts when the plunger
or handle H is thrown over to the position shewn in Figure 14.
For calling or signalling, the springs shewn in Figure 7 are provided. The outer
springs M M may be considered as connected with the two sides of the generator
or source of electricity. The springs N N' may be considered as connected with
the different strands of the cord of a loop plug inserted in the switch of a line into
which it is desired to loop the calling generator. Spring O may be considered as
connecting with the line of the subscriber who has called and over whose line it is
desirable to prevent the signalling current from being sent.
Now it will be observed that the end of the plunger is in such relation to the
springs N N that when the plunger is forced down spring N' will be separated
from spring O and closed to spring M; thus the generator if connected with
springs M M will be looped into the cords, that is to say, into the metallic circuit
of the line wanted.
It will be observed that the plunger H is supported in a pivotted guide piece P.
This guide piece having the extension or arm I. Now it matters not in what
position this guide piece P may be, that is, whether in the position shown in
Figure 14 tilted to bear against the block K on spring D, or whether upright as
shewn for example in Figure 8. In either of these positions the plunger H may be
forced down to operate the springs N N¹ for any purpose desired.
נו

page_text: Figure 16 is a side elevation.
Figure 17 is a rear elevation.
Figure 18 is a detail view shewing the manner of tilting the plunger to throw
on the ground branch containing the annunciator when the plug is lifted from the
socket.
These cord switches are conveniently built up in strips. Thus the metallic or
brass portions A A and B B of the frame of a strip may be insulated from one
another by a strip of rubber C C the base D D of this frame may be of insulating
material, and is of sufficient width to support the springs and contacts on the
opposite sides of the frame. The plunger is mounted upon a metallic guide
pivotted to the metallic portion B B of the frame, this metallic guide is provided
with an arm consisting of two parts, one portion of the arm being preferably of
insulating material of some substance that will have little friction with the metallic
spring against which it acts; the other or lower portion thereof being of metal
and adapted to be brought into electrical connection with the spring when the
guide is tilted.
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 the subscriber's telephone switch, of the subscriber's
bell in a ground branch and the telephone and generator and contacts, whereby
the telephone is shunted when resting upon the switch while the generator and
bell are in circuit while on removing the telephone the generator is shunted, the
ground branch containing the bell opened and the telephone brought into circuit.
2. A telephone line connected in two branches with switches on different switch
boards at the central office, said limbs being normally open at the central office,
a branch or bridge from one of said limbs normally closed through an individual
annunciator and switching device to ground at the central office and the
subscriber's generator included in the limb with which said annunciator branch is
connected and a ground branch at the subscriber's station normally closed to the
subscriber's telephone switch, whereby the subscriber's generator is brought into
a ground circuit between the subscriber's bell and the individual annunciator to
operate the same, substantially as and for the purpose specified.
3. A telephone line extending in metallic circuit to switches on different switch
boards at the central office, one limb of said metallic circuit being branched
through a switching device to a test battery and ground, the subscriber's telephone
switch normally included between the subscribers bell which is in a ground
branch and the subscriber's generator included in that limb of the metallic circuit
which at the central office is provided with the branch connections through the
test battery, in combination with an operator's telephone included in a ground
branch having a cord and plug terminal, whereby on applying said plug terminal
to the test piece of a switch of the line current is diverted by the resistance of
the subscriber's bell in its ground branch to the test piece at which the plug
terminal is applied, thereby indicating by the sound in the operator's telephone
that the line is free.
4. A subscriber's outfit connected with a metallic circuit extending in two limbs
from the subscriber's station to the central office, said outfit consisting of a
generator, a telephone, a bell and an automatic switch, the generator and bell
being in different limbs of the metallic circuit and the bell in a ground branch
which is closed when the telephone is hung upon the switch to bring the said bell
and generator into circuit and disconnect the telephone therefrom.
5. Two telephone lines looped together in metallic circuit through the central
office and a clearing out annunciator bridged across the united circuit of the two
lines at the central office, in combination with the subscriber's generators and

page_text: ening apparatus, whereby when the subscribers operate their switch devices
and bring their generators into circuit the generator of one of the subscribers will
cause current sent from the generator of the other subscriber to flow through the
clearing out annunciator.
6. A telephone line extending in metallic circuit in two limbs or branches to
the central office, one limb being connected with the springs and test pieces of the
switches of the line on different switch boards and through a branch containing a
test battery to ground, the other limb extending to the test pieces of said switches
and being normally open, in combination with a bell included in a normally
closed ground branch at the subscriber's station and current indicating devices at
the different switch boards adapted to be applied to the test piece of a line thereat,
whereby the resistance of the subscriber's bell in the ground circuit serves to
divert current from the test battery to the test piece to which the current indicating
device is applied.
7. A metallic circuit telephone line extending from the subscriber's station to
the central office, in combination with a cord switch and a branch containing an
individual annunciator, whereby the branch containing the individual annunciator
from one limb of the circuit is closed to ground, the two limbs of the circuit being
otherwise normally open at the central office.
8. The two limbs of a metallic circuit, one working directly through the
subscriber's telephone bell and to ground, the other connecting to the same bell
and to ground, an annunciator bridged between the two limbs, in combination with
the calling generator at the central office and switching apparatus for connecting
the same with the first mentioned limb, whereby the subscriber's bell may be rung
without dropping the annunciator.
9. The combination with two metallic circuits, of a generator normally in
circuit at each subscriber's station in the same limb of a metallic circuit, an
annunciator at the central office bridged between the two limbs of the metallic
circuit, whereby upon operating one of the generators the retardation of the other
will divert current through the annunciator to operate the said annunciator.
10. In a cord switch the combination with a set of contact springs, of a plug
adapted to bear upon one of said contact springs to move the same and thereby
the other contact springs of the switch to alter their connections and a lever
adapted to bear upon either of two of said contact springs, whereby three different
commutations may be effected by the said cord switch.
11. The combination with the pivoted lever, of two springs having bearing
surfaces against which said lever is adapted to be forced when vibrated one of
aid bearing surfaces being notched and the other being curved, whereby the
ension of the spring having the curved bearing surface, when the lever is released
fter being forced against the same, causes the lever to take the notch of the
ther spring, substantially as and for the purpose specified.
12. In a cord switch the combination with a set of contact springs, of a plug
dapted to bear upon one of the said contact springs to move the same and
hereby the other contact springs of the switch to alter their connections and a
ocking lever adapted to move certain of the contact springs and also furnished
ith a spring piston or plunger operating on other calling or signalling contact
prings, whereby three different commutations may be effected by the said cord
vitch.
13. Apparatus substantially as represented by the annexed drawings.
נית
300