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Патент USA US2105012

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Jan. 1'1, 1938.
N. H. SAUNDERS
2,105,012
TELEPHONE SYSTEM
Filed Oct. 21, 19755
6 Sheets-Sheet l
Jan. 11, 193s.
N. AH. >SAUNDERS
2,105,012
TELEPHONE SYSTEM
Filed Oct. 2l, 1955
6 Sheets-Sheet 2
ATTORNEY.
Jan. 11, 1938.
2,105,012
N. H. sAUNDERs
'
TELEPHONE SYSTEM
Filed Oct. 21, 1935
6 Sheets-Sheet 3
INVENTOR.
NORMAN H. SAUNDEPS
BY ,
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ATTORNEY.
l* Jan. 11, 1938.
N. H. SAUNDERS
2,105,012
TEpEPHoNE‘ SYSTEM
Filed 061.21, 1935
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INVENTOR.
NORMAN H. SAUNDEQS
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ATTORNEY.
Jan. 11, 1938.
N. H. SALJMDERSv
2,105,012
TELEPHONE SYSTEM
Filed oct. 21, 1935 _
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INVENTOR.
NORMAN H. SAUNDERS
ATTORNEY.
Jan. 11, 1938.
N, H, SA'UNDERS
2,105,012
TELEPHONE> SYSTEM
Filed Oct. 21, 1935
6 Sheets-Sheet 6
FIG. 6
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DIAL BACK
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.
INVENTOR.
NORMAN H. SAUNDEPS
ATTORNEY.
Patented Jan. ll, 1938
2,105,012
UNITED STATES PATENT OFFICE
2,105,012
TELEPHONE SYSTEM
Norman H. Saunders, Chicago, Ill., assignor to
Associated Electric Laboratories, Inc., Chicago,
Ill., a corporation of Delaware
Application October 21, 1935, Serial No. 45,845
y
20 Claims.
The invention relates in general to telephone
(Cl. 179-26)
automatic exchange terminating in an outgoing
systems but more particularly to inter-exchange f repeater and an incoming rotary lineswitch. This
calls in which an operator is required to com
lineswitch is the well known type of rotary line
plete connections between automatic subscribers’ switch which advances its Wipers in response t0
lines over trunk lines connecting two automatic
, exchanges.
'I'he main object of the invention is the pro
vision of means whereby an automatic subscriber
in one exchange in order to call an automatic
subscriber in another exchange must first call
the toil operator over a toll trunk extending from
one of the automatic exchanges to the toll ex
change, after which the toll operator dials back
over this same trunk to operate the automatic
switches to complete the desired connection.
When such connection is completed the toll operï
ator may disconnect and free her trunk leaving
the connection between the two automatic sub
scribers established over one of the trunk lines
‘
20 connecting the two automatic exchanges.
One feature of the invention relates to the pro
vision of a monitoring selector operable by'the
toll operator to monitor the trunks between the
two automatic exchanges to determine their idle
25 01' busy condition.
Other features relate to the circuit reñnements
in the dial back repeater which enables this type
of service to be given.
l
'I‘he drawings, comprising Figs. 1 to 7, in
30 clusive, show by means of the usual circuit dia
grams, a sufiicient amount of apparatus to en
able the invention to be described and under
stood.
Fig. 1 shows one of thetrunks extending to a
35
distant automatic exchange terminating in an
outgoing repeater and an incoming rotary line
switch in the local automatic exchange.
Figs. 2 and 3 show the detail circuits of the
novel dial-back repeater and
3 shows one
40 of the trunks extending to the distant toll switch
ing center.
Fig. 4 shows an all-relay monitor selector for
monitoring the trunks connecting the two auto
matic exchanges.
45
Fig. 5 shows one of the local selector switches.
Fig. 6 shows the dial-back, incoming toll, and
the local line switches, the usual associated mas
ter switches, and one of the local subscribers’
lines.
Fig_ 7 shows a one-line diagram of the trunking
arrangement in the local automatic exchange and
the trunk lines extending to the distant automatic
exchange and the toll switching center. `
Referring now in detail to the drawings, Fig. 1
.55 shows one of the trunks extending to a distant
the deenergization of its stepping magnet. These Ul
lineswitches have access to a group of dial-back
repeaters, one of which is shown in Figs. 2 and 3.
The outgoing repeater comprises a repeating coil
RC and five relays, two of which are the usual
slow-releasing relays as shown by the cross- 10
hatched lower portion. Relay |03 is the Well
known shunt field electro-polarized relay having
an operating winding and a polarizing winding.
This relay operates its armature |33 only when
the current ilow in the operating winding is in l5
opposition to the polarizing winding. The re
peaters are accessible from the sixth level of the
local selectors, one of which is shown in Fig. 5,
and from the monitor selectors, one of which is
shown in Fig. 4,
_
The dial-back repeater shown in Figs. 2 and 3
comprises a group of relays and a rotary step
ping switch having access to trunk lines extend
ing to the toll switching center. This stepping
switch is similar in construction and operation 25
to the well known rotary lineswitch which steps
its wipers on the deenergization of the stepping
magnet. A number of the relays are of the usual
slow-to-release type as shown by the cross
hatched lower portion and by the copper sleeves 30
over their cores. Relay 206 is a slow-to-operate
relay as indicated by the full-black upper portion.
Relays 2|0 and 2l2 are diiîerential relays and
relay 200 is a shunt iield electro-polarized relay
similar to the shunt field relay |03 in Fig. l. Re- 35
lay 202 has a vibrating spring 220 which vibrates
upon operation of armature 22| due to the weight
2|9 on spring 220. The weight 2|9 may be ad
justed so as to vibrate spring 220 for a predeter
mined time interval after 22| is operated so as 40
to intermittently open and close the circuit to
slow-to-operate relay 206. The dial-back repeat
ers are accessible from the tenth level of the local
selectors and from the banks of the incoming ro
tary lineswitches. Each dial-back repeater has
access to an individual dial-back lineswitch, one
of which is shown in Fig. 6.
Fig. 4 shows the monitor selector comprising a
group of relays, two voi.’ which, 403 and 405, are
the slow-to-release type as indicated by the
sleeves around their cores, and two two-step re
lays which close only their “.r" contacts on their
iirst step and their remaining contacts on their
second step when the short circuits around their
- lower windings are opened. Only two trunk re
2
2,105,012
stood that in case there are more than two
back lineswitch to plunge and select an idle local
selector after which the operator dials back over
trunks to the distant automatic exchange then
this same trunk to operate the selector to seize an
lays 40| and 402 are shown, but it will be under
additional trunk relays are connected in a similar
manner. The monitor selector has access to the
idle outgoing repeater to the distant automatic
trunks to the distant automatic exchange by way
exchange. The operator now dials the number
of the distant automatic subscriber and the cut
voi? the outgoing repeater in Fig. 1 and is accessible
from the .eighth level of the local selectors.
automatic trunk to cause the automatic switches
Fig. 5 shows one of the local selectors which are
10 of the well known Strowger vertical and rotary
type of switch. These selectors are of the re
stricted service type having normal post springs
going repeater repeats the impulses over the
in the distant exchange to complete the desired
connection.
When the called subscriber answers
the toll operator disconnects from the toll trunk,
thereby freeing such toll trunk for other calls
while the local and distant subscribers talk over
the established connection.
Incoming calls from the distant automatic ex
stricted levels. The polarized switching relay
501, as indicated by the bar through its middle, ' change to the local exchange come in over the
which are operated when the Wipers have been
raised in a vertical direction opposite the re
is similar infconstruction and operation to the
relay disclosed in Patent No. 1,673,884, issued
June 19, 1928, to H. C. Pye. The local selectors
20 have access to the dial repeaters, the outgoing
repeaters, the monitor selector, reverting call
switches, and the local connectors as shown in
Fig. 7. These selectors are accessible from the
dial back, incoming toll, and local lineswitches25 shown in Fig. 6.
,
The lineswitches and master switch shown in
Fig. 6 are similar in construction and operation
to the lineswitch and master switch shown in
Patent No. 1,809,086, issued June 9, 1931, to John
30 Voss and B. D. Willis. These lineswitches: have
access to the local selectors over trunk lines such
as trunk line 560, 563. Each local subscriber’s
line, one of which is indicated by the circle with
A in the center, have a local restricted lineswitch
individual thereto.
Each automatic subscriber,
outgoing repeater causing the incoming rotary
lineswitch to select an idle dial-back repeater
which then automatically selects an idle toll trunk
and signals the toll opérator thereover. In order 20
to extend the call to a local subscriber the toll
operator unbalances the line thereby causing the
associated dial-back lineswitch to seize an idle
local selector after which the toll operator dials
back over this same toll trunk to operate the local
selector and connector to complete the call.
When the local subscriber 'answers the toll oper
ator disconnects and frees her toll trunk for use
on other calls.
'
Since the toll operator is disconnected from the
established connections between the local and dis
tant automatic subscribers, a monitor selector is
provided in the local exchange to enable the toll
operator to determine the busy or idle condition
of the trunks connecting the local and distant
switches are each individual to and accessible
automatic exchanges. In order to monitor these
trunks the toll operator seizes an idle toll trunk
thereby causing the incoming toll lineswitch to
from the dial-back repeaters while the incoming
select an idle local selector after which the local
toll lineswitches are each individual to a toll
selector is operated to seize the monitoring select 40
or. The toll operator now operates the monitor
selector to engage with successive automatic
trunks to determine their busy or idle condition.
Having given a general description of the op
eration, a detailed description will now be given.
For this purpose it will be assumed that a local
subscriber, such as subscriber A in Fig. 6, desires
to call another automatic subscriber in the local
automatic-exchange. In response to subscriber
such as A, is equipped with the usual transmitter,
receiver, and calling device. The dial-back line
trunk extending to the toll switching center. The
dial-back and incoming toll lineswitches are non
restricted, having conductors 680 and 690 for
accomplishing a purpose to be more fully de
45 scribed hereinafter.
Referring now to Fig. 7, a general description
of the operation will now be given. When a local
subscriber such as A calls, the subscriber’s local
lineswitch plunges and seizes an idle local selector.
A removing his receiver a bridge is closed across .
50 lIn case of a local call, subscriber A dials and conductors 610 and 61| thereby completing a cir
operates the selector to seize an idle local con-`
nector which is thereafter operated to complete cuit for the slow-to-operate line relay 640 as fol
lows: from ground by way of springs 664, con
Y the desired local call. In case of a reverting call
the calling subscriber dials and operates the
55 selector to select one of the reverting call switches
after which the reverting call switches are oper
ated to signal the desired subscriber on his own
line when he hangs up. In case a local sub
scriber attempts to dial the distant automatic
60 exchange direct then the selector is operated to
the restricted level where it automatically ro
tates to the eleventh position where the selector
cam springs are operated to give the calling sub
scriber a busy signal. In order for the local sub
65 scriber to be connected to a subscriber in the
distant automatic exchange it is necessary for
such subscriber to dial the selector to the “O”
level to seize an idle dial-back repeater. When
the dial-back repeater is seized a splash of gener
70 ator is transmitted over one of the idle toll trunks
to ’the toll switching center. The toll operator
answers and when it is learned that a local sub
scriber desires connection with a distant auto
matic subscriber the toll operator unbalances the
75 toil trunk thereby causing the associated dial
ductor 61|, through the substation loop, con
ductor 610, springs 643, and through the winding .
of relay 640 to battery. At armature GM line
relay 640 at its back contact opens the circuit to
the B. C. O. upper winding of relay 64S and at its
make contact grounds conductor 672 to make this
line busy to the local connectors. At armature
642 relay 64B completes the circuit through the
lower pull-down winding of the plunger coil 646
in case no other line relay in this particular group
is in operated position. This circuit may be
traced as follows: from grounded conductor 666 65
extending from the master switch through the
normally closed springs controlled by armatures
SI2 and 622, front contact and armature 642 and
through the lower pull-down winding of plunger
coil 646 to battery. In response to the operation 0
of the pull down Winding, the plunger (not
shown) of the lineswitch plunges into the line
switch bank to close springs 65|, 654, 652, and
853. The pull-down winding of coil 646 also
operates its armatures to open the circuit to line
9,105,012
relay 840 at springs 043 and 044 and at springs
545 completes a temporary circuit through the
upper B. C. O. winding o! coil 540 as follows:
from ground by way of iront contact and arma
ture 54|, contact 545, and through the upper
B'. C. O. winding of coil 545 to battery. Since
the master switch maintains the plungers of all
« idle lineswitches opposite an idle trunk terminat
ing in an idle local selector, vas described in Pat
ent No. 1,809,086, the closure ot springs 55| and
654 extends the loop including the calling sub
scriber's line over conductors 550 and 553 and
through armatures 525 and 530 and their back
contacts to the upper winding of line relay 505
to battery and through the lower winding oi line
relay 505 to ground at the normally closed con
tacts controlled by armature 5|6.
Line relay 505 immediately energizes over the
above traced circuit and at amature 524 com
20 pletes the energizing circuit for release relay _505
as follows: from ground by way of armature »521,
amature 525 and front contact, and through the
winding of release relay 505 to battery. At arma
ture 525 line relay 505 also prepares the circuit
25 through the upper winding of polarized switching
relay 501. Release relay 505, upon energizing, at
armature 520 grounds conductor 55| by way of
the busy key 523 to maintain the local lineswitch
operated and the calling line busy to local con
30 nectors after the line relay 840 in the plunger
lineswitch restores. At armature 522 release relay
505 completes the circuit through the lower polar
izing winding of switching relay 501 and com
pletes an energizing‘circuit through the lower
winding of series relay 504 by way of off normal
springs 5H, and at armature 52| opens a point
in the circuit to the release magnet 50| at its
back contact and at its front contact prepares a
circuit for holding the series relay 504 in ener
40 gized position during the dialling period and for
operating vertical magnet 502.
Y
In the local lineswitch the slow-to-release line
relay 540 deenergizes after ground is returned over
connector 55| and which ground extends by way
of springs 553 and through springs 545 and arma-~
ture 54| and back contact in parallel to the up
per winding of coil 545. At armature 542 the de
e'nergization of line relay 640 again establishes
50
'3
relay |04 in operated position as follows: from
grounded armature 521, armature 524 and back
contact, armature 52| and front contact, arma
ture 5|0, and through the vertical magnet 502
and the upper winding of series relay 504 in mul
tiple to battery. Vertical magnet 502 is ener
gized in response to each impulse to step the
wipers 540 to 542 one step in a vertical direction,
while series relay 504 due to its slow release char
acteristics is maintained in operated position
over this pulsing circuitduring the dialling pe
riod. At armature 524 line relay 505 temporarily
opens the circuit through the release relay 505
but the release relay being of the slow-to-release
type maintains its armature in operated position
during the dialling period. On the ñrst vertical
step of the wipers oil-normal springs 5| 0 pre
pares a point in the circuit to the release magnet
50|, on'-normal springs 5| | opens the originalen
ergizing circuit oi' series relay 504, and oil-normal 20
springs 5|2 prepares a point in the circuit to the
rotary magnet 503.
Line relay 505 is maintained energized after
the dialling period and shortly thereafter series
relay 504 deenergizes. At armature 5|6 series
relay substitutes direct ground in place of dial
tone, at armature 5|1 prepares a. point in the cir
cuit to release magnet 50|, and at armature 5|9
completes the circuit for operating the rotary
_magnet 503 as follows: from grounded armature 30
521, armature 524 and front contact, off-normal
springs SI2, interrupter contacts 5| 5 of magnet
503, back contact and armature BES. and through
the winding of rotary magnet 500* to battery.
Rotary magnet 503, upon energizing, steps the
wipers one step for each energlzation and at in
terrupter springs 5|5 interrupts the circuit to
magnet 503. Rotary magnet 503 due to inter
rupter springs 5|5 operates in the manner of a
buzzer stepping the wipers in a rotary direction 40
until such time as the circuit is completed for the
polarized switching relay 501. 'I'he local selector
is of the type known as the battery searching
type, and therefore the polarized switching re
lay 501 will not energize until the test wiper 54| 45
-encounters a bank Contact having battery poten
tial thereon, which potential indicates an idle 1o
the chain circuit to the master switch.
cal connector.
Series relay 505 energizes over the previously
traced circuit through its lower winding, and at
armature 5|5 disconnects ground and substitutes
ground through the dial-tone source by way of
idle local connector having battery potential on 50
its incoming test conductor a circuit may be
traced for energizing the polarized switching re
cam springs 5|3. At armature 5|1 relay 505
opens a further point in the circuit to the release
magnet, at armature 5|8 prepares another point
in the circuit for maintaining itself in operated
position during the dialling period, and at arma
ture 5|0 opens a point in the circuit through the
60 rotary magnet 503. Dial tone is now transmitted
to the calling subscriber by way of dial-tone
source, cam springs 5|3, armature SI5 and i'ront
contact, through the lower winding of line relay
505, back contact and armature 530, from thence
65 over conductors 553 and 51| through the substa
tion loop back over conductors 510 and 550 and
through the upper winding of line relay 505 by
way of armature 525.
`
In response to hearing dial tone the calling
70 subscriber now dials the iìrst digit of the local
called subscriber’s number. Line relay 506 iol
lows the impulses in the dialled digit and in re
sponse to its deenergization at armature 524 and
back contact completes a circuit for energizing
As soon as the Atest wiper 54| encounters an
lay 501 as follows: from ground by way of arma
ture 520, point 532, back contact and spring 53|
of the normal post springs, through the upper
winding of relay 501, armature 525, test wiper
54|, and engaged bank contact. and over the in
coming test conductor of the idle local connector
to negative battery. Since the lower electro-po
larizing- winding of switching relay 501 was ener 80
gized by way of grounded armature 522 of release
relay 505 and since the flow of current through
its upper winding is in the proper direction po
larized relay 501 now energizes and at armature
521 opens the circuit extending to the rotary mag 65
net 503 to stop the wipers of the selector in en
gagement with the bank contacts terminating
this local connector. At armatures 525 and 530
switching relay 501 switches the calling loop from
the windings of the line relay 505 to the windings
of the line relay in the local connector.
'I'he line and release relays in the local con
nector energize in the well known manner and
connect ground back over the incoming test con
76 the vertical magnet 502 and for maintaining series
ductor, test wiper 54|, armature 529, point 532, 15
4
2,105,012 `
armature 523, and through the lower winding of
polarized switching relay 501 for maintaining this
relay in energized position through its 'lower
winding alone as long as ground is maintained
on testwiper 64|. This same ground transmit
ted back from the local connector also extends
from point 532 by way of the busy key 523 and
conductor 56| for maintaining the plunger line
switch in operated position and for maintaining
10 the calling line busy to the local connector. line
relay 506 deenergizes in response to the operation
of polarized relay 501, and at armature 524 pre
pares a further point in the circuit to release mag
net 50| at its back contacts, and atitr front con
16 tacts opens the circuit to release relay 505.4 Slow
t'o-release relay 505 at armatures 520 and 522
disconnects ground from conductors 56| and the
lower winding of relay 501 only after ground has
been returned from the seized connector. At
inclusive are returned to their normal positions.
The cam springs 6|5 and 5|4 are also now in nor
mal position. The local selector is released in a
similar manner at the completion of a local call
over the local connector by the local connector
disconnecting ground sent back over the incom
ing test conductor to test wiper 54| to open the
circuitv through the lower winding of switching
relay 501, whereupon this relay deenergizes. At _
armature 521 relay 501 completes the circuit for
release magnet 50|. This ground is likewise dis
connected from conductor 56| with the result
that the holding circuit through the upper wind
ing of coil 646 of the local lineswitch is opened
causing the armatures of this coil and the plunger
to be restored to their normal position. 'I'his
ground is likewise removed from conductor 612
so that local subscriber A may be called over the
local connectors.
It will now be assumed that subscriber A desires 20
20 armature 52| and back contact release relay 505 Y ‘ to call a subscriber in the distant automatic ex
prepares another point in the circuit to release
magnet 50|.
The local connector is operated in the well
known manner by the calling subscriber to com-V
plete the desired local connection, the talking
circuit including the heavy talking conductors.
In case the local subscriber operates the local
change, and in order to do so subscriber A dials
selector opposite one of the restricted levels then
dial-back repeater, then the circuit for energizing
the polarized switching relay 501 in the local 30
the normal post springs operate to switch the cir
30 cuit Ior operating the polarized switching relay
the digit 0 to cause the local selector in the
same manner' as previously described to be `raised
opposite the tenth level after which the selector 25
rotates step by step in search of an idle dial-back
repeater. Assuming further that the dial-back
repeater shown in Figs. 2 and 3 is the ilrst idle
selector may be traced as follows: from ground
over the restricted service conductor 562 which -by way of armature 520, resting contact and
in this case is not connected in the local line
switch because the subscribers, such as subscriber
A, are restricted from completingV calls on the
restricted levels. Assuming now that subscriber
A has operated the local selector opposite a re
stricted level and since no circuit is completed
for switching relay 501 the rotary magnet 503
continues to operate until the wipers of the se
40 lector are rotated to their eleventh position of the
bank contacts at which time cam springs 5|3 and
5|4 operate. The operation of cam springs 5|4
completes a circuit through the lower winding
of series relay 504 by way of front contact and
armature 524 and grounded armature 521. At
amature 5|3 _series relay 504 upon energizing
opens the circuit to rotary magnet 503 and at
armature 5|6 connects the busy tone to the call
ing subscriber as follows: from busy tone source
50 by way of the front contacts and cam springs 5|3,
amature 5|6 and front contact, through the
lower winding of line relay 506 and from thence
over the calling subscriber’s loop, as previously
described.
55
In response to busy tone the calling subscriber
will replace his receiver, thereupon opening the
circuit of line relay 506 whereupon the latter
relay deenergizes. At armature 524 line relay
506 opens the circuit to release relay 505 at its
front contact and at its back contact prepares
a point in the circuit to the release magnet, and
at its front contact also opens the circuit through
the lower winding of series relay 504, whereupon
the latter relay deenergizes. When slow-to-re
65 lease relays 504 and 505 deenergize, a circuit for
operating release magnet 50| may be traced as
follows: from grounded armature 521, arma
ture 524 and back contact, armature 52| and
back contact, armature 5|1, off-normal springs
70 5|0, and through the winding of release magnet
50| to battery. By the operation of the release
magnet 50|, the wipers 540 to 542 inclusive, are
returned to their normal position in the well
known manner, and when the wipers reach their
10 normal position the ofi-normal springs 5|0 to 5|2,
spring 53| of the normal post springs, upper op
erating winding of polarized relay 501, armature
625, wiper 54|, conductor |6|, through the lower
winding of impedance 201, conductor 26|, nor
mally closed springs 334 of the busy key, arma
ture 3|3'and back contact, through the resistance
R5 to battery. Polarized switching relay 501
energizes over this circuit and at armatures 526 40
and 530 connects the calling subscriber’s loop
across the windings of the start and battery feed
relay 306. This circuit may be traced as fol
lows: from ground through the upper winding of
relay 306, conductor 266, conductor |62, wiper
542, front contact and-armature 530, conductor
563, contact 654, conductor 61|, through the sub
station loop, conductor 610, contacts 65|, con
ductor 560, armature 526 and front contact, wiper
540, conductor |60, conductor 269, and through .
the lower winding of relay 306 to battery.
Relay 306 energizes over the calling subscriber’s
loop and at armature 323 completes a circuit by
way of conductor 265, armature 243 and back con
tact, conductor 264, through the winding of bat
tery reversing relay 30| to battery for energizing
relay 30|. At armature 330 relay 306 completes
the circuit for energizing relays 302 and 304.
Relay 304, ‘upon energizing, at armature 32|
prepares a point in the circuit for energizing 60
switching relay 305, at armatures 322 and 323
prepares _a circuit for connecting interrupted gen
erator and ground to one of the toll switching
trunks. Relay 30|, upon energizing over the
above traced circuit, at armature 3|0 completes
a circuit for starting the ringing machine at its
front contact and at its back contact opens the
circuit to the all-trunk-busy relay (not shown),
and at armatures 3|| and 3|2 prepares a re
versing circuit to be explained more fully herein 70
after. Hold relay 302, upon energizing, at arma
ture 3|3 disconnects the idle battery potential at
its back contacts and at its front contact substi
tutes ground therefor, thereby connecting ground
to the incoming test conductor |6| and test wiper 75
9,155,019
54| of the local selector to hold the polarized
switching relay 501 in energia“ position and for
maintaining the local lineswitch in operated po
sition and the calling line busy to local connectors.
At armature 3H hold relay 302 grounds con
ductor 262 to energize the polarizing winding of
polar shunt field relay 200, at armatures 3|5 and
3|6 short circuits test relay 303 in case the test
wiper 343 is in engagement with a busy called toll
10 trunk, while at armature M6 completes a circuit
for operating the marginal stepping magnet 301
in case the toll trunk is busy.
In case the toll trunk engaged by the wipers 300
to 343, inclusive, is bus , ground will be present
on the test conductor 302 which ground extends
by way of wiper 343, normally closed springs con
trolled by armature 328, armature 320 and back
contact, armature 3|6, normally closed springs
winding relay 31| of the delayed ground relay
group may be traced as follows: from ground by
way of the high resistance winding of relay 31|,
over common conductor 310, annature 32|, front
contact and armature 3|1, through the lower
winding of switching relay 305,_ through the in
terrupter springs 332, and through the winding of
stepping magnet 301 to battery. Due to the high
resistance winding of relay 31|, switching relay 10
305 and stepping magnet 301 do not energize over
this circuit. Relay 31|, however, energizes and at
armature 312 completes a circuit for energizing
the A. C. relay 316 in case the ringing machine
has been started and generator is applied to the
generator> lead. When A. C. relay 316 energizes it
operates armature 315 to close a circuit to the
20 controlled by armature Eis, conductor 21|,'ar-
slow-to-operate relay 310. After an interval of
time slow-to-operate relay 314 operates its arma.
301 to battery. A branch of this same circuit ex~
tends from ground as previously traced to arma
25 ture 3| 6 and thence through the winding of test
ductor 310 to operate the switching relay 305 and
to short circuit the high resistance relay 31|.
The circuit for energizing switching relay 305
mature 233, conductor 210, interruptor springs
332, and through the winding of stepping-magnet
relay 303, armature 313, conductor 213, to
grounded armature 222, thereby short circuiting
the test 'relay 303 to prevent its energization
when the wiper 303 engages a grounded bank
30 contact. The stepping magnet 301 energizes over
the above-traced circuit and positions its pawl
preparatory to stepping the wipers of the asso
ciated switch. Near the end of its stroke magnet
301 opens the interrupter contacts 332, thereby
opening its own circuit. Stepping magnet 301
35 thereupon deenergizes and steps the wipers one
step into engagement with the next toll trunk. In
case the second called trunk is busy ground is
again encountered by test wiper 303 to maintain
the test relay 303 short-circuited and again oper
40 ates the stepping magnet 301.
When test wiper 333 encounters a bank contact
without ground potential indicating an idle toll
trunk, a circuit may then be traced for energizing
the test relay 303 as follows: from grounded ar
mature 222, conductor 213, armature SIS, through
the winding of test relay 303, normally closed
springs controlled by armature 3| 9, conductor
21|, armature 235, conductor 210, interrupter
springs 332, and through the winding of marginal
stepping relay 301 to battery. Stepping relay
301 is marginal and will not energize due to the
high resistance of relay 303. Relay 303, upon en
ergizing, at armature 3H prepares a circuit
through the lower winding of switching relay 305,
at armature 3|8 connects the ring-back circuit to
60
s“ 5
- The circuit for energizing the high resistance
the calling subscriber, at armature 3|9 substitutes
the battery through resistance R1 for the battery
through the stepping magnet 301, at armature 320
grounds test wiper 303 and conductor 362, to make
this trunk line busy to other dial-back repeaters.
Test relay 303 is now locked in energized position
over the following circuit: from grounded arma
ture 222, conductor 213, armature 3|5, through
the winding of test relay 303, and through the
ture 313 to connect direct ground to common con 20
may now be traced as follows: from grounded ar
mature 313, common conductor 310, armature 25
32|, front contact and armature 3|1, lower wind
ing of switching relay 305, interrupter springs 332,
and through the winding of stepping magnet 301
to battery. Motor magnet 301 does not energize
in series with switching relay 305 but the latter 80
relay at armature 325 completes its holding cir
cuit independent of ground on the delayed
ground lead 310. At armatures 323 and 33|
switching relay 305 connects generator out ‘over
the toll trunk to signal the toll operator at the 35
toll switching center as follows: from grounded
generator through the resistance R6, front con
tact and armature 322, armature 320, wiper 34|,
conductor 360, to the toll center, through the sig
nailing apparatus thereat back over conductor
36|, wiper 342, armature 33|, and armature 323 40
and front contact, to ground. At armature 321
switching relay 305 opens the circuit to the slow
releasing ring-relay 304, and at armature 328
connects direct ground to test wiper 343 to main
tain this toll trunk busy. Ringing relay 304 de
energizes after an interval and at armature 32|
opens the original energizing circuit of switching
relay 305, and at armature 322 and 323 discon
nects ringing current at the front contacts and
at the back contacts thereof connects the line and 50
differential relays 203 in bridge of the toll trunk.
From the foregoing, it will be seen that ringing
current has been applied to the toll trunk con
ductors 360 and 36| for an interval in order to
operate the signal at the operator’s switchboard.
When the toll operator observes the signal and
answers the circuit is completed for energizing
line relay 209 as follows: from ground through
the lower winding of line relay 209, lower winding
oi’ differential relay 2|0, conductor 261, arma 60
ture 3|| and front contact, resting contact and
armature 322, armature 326, wiper 34 |, conductor
make contact and armature 3 I 9 and resistance R1
350, over the bridge at the toll board back over
conductor 35|, wiper 342, armature 33| , armature 65
323 and back contact, front contact and armature
back tone to the calling subscriber may be traced
as follows: from interrupted generator through
the multipled contacts and wiper 340, ring-back
3|2, conductor 266, upper winding of differential
relay 2| 0, and through the upper winding of re
lay 209 to battery. Diiïerential relay 2|0 does
not energize over the above-traced circuit be 70
cause both windings are equal and oppose each
other, but line relay 209 at armature 239 com
pletes an obvious circuit for energizing release
relay 208. At armature 240 line relay 209 pre
pares a point in the loop and impulsing circuit
75
to battery.
The ring-back circuit for transmitting ring
condenser, armature 3|8, conductor 263, armature
2| 5, normally closed contacts controlled by arma
ture 2|6, conductor |60, from thence over the
heavy talking conductors and the calling loop,
as previously described.
2,105,012
6
extending to the dial-back switches. Release re
lay 208, upon energizing, prepares a point in the
circuit to series relay 205 at armature 235, at
armature 236 grounds conductor 26| and the in
coming test conductor |6| through the lower
windings of impedance 201 to maintain the local
switches in operated position. at armature 231
completes a circuit through the lower winding of
armature 329 and at amature 330 opens the cir
cuit of hold relay 302. Reversing relay 30 I, upon
deenergizing, at armatures 3I| and 3|2 reverses
line reversing relay 20| as well as preparing the
10 locking circuit for tone relay 206, and at arma
ture 239 grounds conductor 214 to maintain the
test relay 303 in operated position. Line revers
ing relay 20|, upon energizing, at armature 2I3
completes the circuit for energizing timing relay
202 at its front contact and at its back contact
disconnects ground from the ringing machine
start conductor. At armature 2|4 relay 20| con
nects another ground circuit through the polariz
ing winding of the shunt field relay 204 from ar
20 mature 236, ataar'mature 2 I5 opens the ring-back
circuit toth'ë calling subscriber, at amature 2|1
opens the short circuit around the upper winding
f of" impedance 201
to permit pay-station tone if
connected to conductor |6| to be induced from
25 the lower winding of impedance 201 to the upper
winding of impedance 201 in order to inform the
toll operator that a paystation is calling, and at
armatures 2|6 and 2 I8 reverses battery back over
conductors |60 and |62 for supervisory or meter
30 ing purposes to the calling line. Timing relay
202, upon energizing, operates its armature 22|
to start the weight on spring 220 vibrating to in
termittently close a circuit to slow-to-operate
relay 206. Relay 206 is a slow-to-operate relay
35 and does not immediately operate its armature
battery back over the toll trunk to give the op
erator release supervision. Hold relay 302, upon
deenergizing, at armature 3|3 disconnects one of
the multiple grounds from the test lead I6I, at
armature 3I4 disconnects one of the‘ multiple
grounds to the polarizing winding of shunt field
relay 204 and at armature 3I5 disconnects 10
grounded amature 222 from the lower terminal
oi' test relay 303.
When the toll operator disconnects, the circuit
to relays 209 and 2I0 are opened whereupon relay
209 deenergizes. At armature 239 relay 209 opens 15
the circuit to release relay 208 and momentarily
operates the series relay 205 which is without ef
fect at this time. Release relay 208, upon de
energizing, at armature 235 opens the momen
tarily closed circuit to series relay 205, armature 20
236 disconnects ground from test conductor I6I
to free the local switches and disconnect ground
from the polarizing winding of the shunt ñeld
relay 204, at armature 231 opens the circuit of
line reversing relay 20| and unlocks relay 206, and 25
at armature 239 opens the circuit of test relay
303. Line reversing relay 20|, upon'deenergizing,
at armature 2|1 short circuits the upper wind
ing of impedance 201, at armature 2I3 opens the
circuit of timing relay-202 and again grounds the 30
all-trunk-busy lead, and at armatures 2 I6 and 2I8
restores the normal line connections. Timing re
and therefore does not operate until the vibra
tions of weighted spring 200 decrease in ampli
lay 202 deenergizes and at armature 22| opens
the circuit to tone' relay 206 and tone relay 206,
upon deenergizing at armature 233, opens the
shunt across the upper winding of the impedance
201. Test relay 303, upon deenergizing, at arma
tude or remain closed for an interval of time suill
ture 3I1 closes a short circuit around the lower
cient for the slow-to-operate relay 206 to operate winding of switching relay 305 and likewise com
pletes a circuit for energizing stepping magnet 40
40 its armature. After an interval slow-to-operate
relay 206 energizes and at armature 233 again 301 as follows: yfrom grounded armature 325,
short circuits the upper winding of impedance ` armature 3|1 and'back contact, and through the
201 to cut off the pay-station tone if connected winding of stepping magnet 301, to battery. Step
to conductor | 6| and at armature 234 completes ping magnet 301, upon energizing, positions its
a locking circuit for itself from grounded :arma
pawls preparatory to stepping the wiper of the
switch, and at interrupter springs 332 opens the
ture 231.
The talking circuit between the local calling circuit of switching relay 305. Switching relay
subscriber and the toll operator extends over the
305, upon deenergizing, at armature 325 opens
heavy talking conductors as follows: conductors the circuit to stepping magnet 301, at armatures
610 and 61|, line-switch contacts 65| and 654, 326 and 33| opens the circuit to the toll trunk, 50
50
conductors 560 and 563, armatures 526 and 530 at armature 328 disconnects ground from wiper
and their front contacts, wipers 540v and 542, 343 to free the toll trunk, and at armature 321
conductors |60 and |62, armatures 2|8 and 2I6 prepares a circuit to ringing relay 304. Stepping
and their front contacts, armatures 23| and 230 magnet 301 deenergizes and steps the wipers 340
55 and their back contacts, condensers C2 and C3, to 343, inclusive, one step and closes its inter
conductors 261 and 266, armatures 3II and 3|2 rupter springs 332, thereby again establishing the
and their front contacts, back contacts and arma
tures 322 and. 323, armatures 326 and 33|, wipers
'34| and 342, and by way of the toll trunk conduc
60 tors 360 and 36| to the toll operator. Talking
battery for the toll operator is furnished through
the windings of line relay 209, while talking bat
tery for the local calling subscriber is furnished
through the windings of the battery feed re
65 lay 306.
When the toll operator receives the informa
tion she may extend the call to a distant ofllce,
or may call back through the exchange in which
the dial-back repeater is located by momentarily
70 unbalancing the toll trunk. It will ñrst be as
sumed that the toll operator completes the de
sired call to a distant office and after conversation
is terminated and when the calling subscriber
hangs up the battery feed relay 306 deenergizes
75 and opens the circuit of reversing relay 30| at
short circuit around the lower winding of switch
ing relay 305. The local switches, such as the
local lineswitch and the local selector, release in 60
the same manner as previously described and all
of the relays in the dial-back repeater are now
in normal position and can now be used on sub
sequent calls.
Assuming now that at the time the local sub
scriber seizes a dial-back repeater, all of the toll
trunks are busy. In this case,all of the conductors,
such as conductor362individual to each toll trunk,
wilLbe grounded with the result that the switch
wipers 340 to 343, inclusive, will continue to step 70
until such time as the test wiper 342 engages the
normally grounded all-trunk busy conductor 363
which, in case all the trunks are busy, is now no
longer grounded. Under this condition, when
the switch wiper stops in engagement with this 75
aio'ao'is'
set of bank contacts the test relay is energized
and busy tone is transmitted to the calling sub
scriber. when test wiper 343 encounters the bank
contact terminating conductor 363 from which
ground has been removed, then the test relay 303
energizes in the same manner as previously de
scribed to transmit the busy tone back to the
calling subscriber. 'I'he busy tone circuit may be
traced from the busy tone source, wiper 340, tone
10 condenser, armature 3| 8, conductor 263, armature
2 I6, normally closed- contacts controlled by arma
ture 2|6, conductor |60, and from thence back
over the calling loop to the calling subscriber in
the well known manner. When the delayed
15 ground is connected to conductor 310, as previ
ously described, switching relay 305 energizes and
locks and at amature 321 open the circuit to re
lay 304, whereupon the latter relay deenergizes.
When the calling subscriber hears the busy tone
20 such subscriber will replace his receiver, thereby
causing the deenergization of relays 306, 30|, and
302, and the release Aof the local lineswitch and
selector, as previously described. Test relay 303
likewise deenergizes to open the busy tone circuit
25 and to cause the operation of stepping magnet 301
which in turn causes the deenergization of switch
ing relay 305, after which stepping magnet 301
deenergizes and steps -the wipers one step.
Returning now to the point where the toll
operator is signalled and has answered, it will
now be assumed that the toll operator is to ex
tend this call back through the local exchange to
the distant automatic exchange instead of to an
exchange beyond the toll center, as previously de
scribed. At the time the operator has answered it
will be remembered that the following relays are
ture 250, conductor 216, springs 6I3 and through
the winding of line relay 6|0 to battery. Polar
ized shunt-ñeld relay 204 does not energize over
the above-traced circuit because the current flow
in the operating winding is in the wrong direction.
'I'he toll operator now disconnects ground from
conductors 360 and 36|, whereupon the differen
tial relay 2I0 deenergizes since the short circuit
is now removed from its lower winding. Relay
2|0, upon deenergizing, at armature 24| removes 10
the Short circuit from around the lower winding
of relay 2| I, whereupon the latter relay energizes
in series with the lower winding of dial-back re
lay 2I2 over the circuit previously traced. Re
lay 2II, upon energizing, at armature 242 pre 15
pares a point in the locking circuit to switch
through relay 203, at armature 203 opens the cir
cuit to trunk reversing relay 30|, at armature
240 opens the original energizing circuit through
the lower winding of dial-back relay 2|2 at its 20
back contact and at its front contact prepares
a point in the circuit to the upper windings of
relays 2H and 2|2, and at armature 245 opens a
further point in the circuit to the stepping mag
net 301. Trunk reversing relay 30| accordingly 25
deenergizes and at armatures SII and 3i2 re
verses the current back over the toll trunk con
ductors 360 and 36| to indicate to the toll oper
ator that she may dial.
Returning now to the dial-back lineswitch at 30
a time when the circuit to the line relay 0I0 is
completed. Relay 6|0, upon energizing, at arma
ture SI2 completes the circuit for the lower pull
down winding of plunger-coil 616 as follows:
from ground at the master switch by way of con 35
ductor 660, front contact and armature 6i 2, and
operated: relays 306, 30|, 302, 303, 305, 209, 208,
through the lower pull-down winding of plunger
20|, 202, and 206. The operator after answering
coil Slß to battery. In response to the oper
ation of the plunger coil 6|6 the plunger in the
dial-back lineswitch is operated to plunge in on
40
an idle trunk and in this case, assuming that the
the call now momentarilygrounds both conductors
360 and 36|. Ground extending over conductor
360 short circuits the lower winding of relays
206 and 2 I0, while ground over the" conductor 36|
holds the line relay 209 energized and causes the
operation of differential relay 2I0. Differential
45 relay 2I0, upon operating, at armature 20| corn
pletes the circuit for energizing diiîerential dial
back relay 2I2 as follows: from ground by way
of armature 239 and front contact, armature 20|,
armature 225, armature 264 and back contact,
50 and through the lower winding of differential
dial-back relay 2|2 to battery. At armature 266
relay 2I2 opens a further point in the circuit to
the ringing machine start lead, at armature 201
55
7,
prepares a point in the circuit through its upper
winding, at armature 208 closes a circuit for
maintaining its lower winding energized and for
short circuiting the lower winding of relay 2|I
and at armature 240 closes a loop circuit through
60 the dial-back lineswitch to cause the operation
of line relay' SIU thereat. The short circuit
around the lower winding of relay 2li and the
circuit for maintaining dial-back relay 2I2 in
energized position may be traced as follows: from
65 ground by way of armature 3M, conductor 262,
armature 20B, lower winding of relay 2| I, lower-
winding of relay 2I2 and from thence by way of
back contact and armature 244, armatures 225
and 24|, and front contact and armature 239.
The circuit for energizing the line relay 6I0
70
of the dial-back lineswitch may be traced as fol
lows: from ground by way of Springs SI2, con
ducto'r 215, armature 249, armature 260, right
hand operating winding of polarized shunt-ñeld
relay 204, back contact and armature 232, arma
trunk conductors 560 to 563 extend to another
local selector similar to the selector shown in
Fig. 5, the plunger will operate and close springs
60| to 600, inclusive. The operation of the plung
er coil 6I6 also at springs 6I3 and 6I4 opens the 45
circuit to line relay 6|0 and at spring SI5 mo
mentarily completes a circuit through the upper
winding of coil BIB from ground by way of the
front contact and armature GII, non-restricted
connector 680, springs 6 I 5, and through the upper 50
winding of coil 6|6 to battery.
In order to avoid duplication of drawings it
will be assumed that the local selector shown in
Fig. 5 is now a different selector than the one
taken into use by the local subscriber, and that
in response to the plunging of the dial-back line
switch the following circuit is completed for line
relay 506 of this local selector as follows: from
ground through the normally closed springs con 60
trolled by armature 5| 6, lower winding of line
relay 506, back-contact and armature 530, con
ductor 563, springs 604, conductor 215, armature
209, armature 200, through the right-hand oper
ating winding of polarized shunt-ñeld relay 204, 65
back contact and armature 232, armature 250,
conductor 216 springs 60|, conductor 560, arma
ture 626 and back contact, and through the up
per winding of line relay 506 to battery. 'I'he
operation of the dial-back lineswitch and local 70
»selector are similar to that previously described
for the local lineswitch and local selector used
by the calling local subscriber, and therefore only
a brief description of the operations will be given.
Line relay 506, upon energizing, at armature 524 75
aioaoîà
completes the circuit for energizing release relay
505 and at armature 525 prepares the test circuit
for the polarized switching relay 501. Release
relay 5|5, upon energizing, _at armature 520 con
nects ground to conductor 56| to maintain the
dial-back lineswitch in operated position after
the line relay 6|0 deenergizes, at amature 52|
prepares a point in the circuit to a point in the
impulsing circuit to the vertical magnet 502 and
10 the series relay 504, and at armature 522 closes
a circuit through the lower polarizing winding of
switching relay 501 and completes the circuit for
operating series relay 504. Series relay 504, upon
energizing, at armature 5|6 substitutes ground
through the dial-back tone source for ground at
thelnormally closed springs controlled by arma-V
ture`5|6 in order to give the operator the dial
tone, at armature 5|1 opens a pointin the cir
cuit to the release magnet. at armature 5|3 pre
20 pares the circuit for the vertical magnet 502 and
at its own upper winding, and at armature 5|9
opens the circuit to the rotary magnet 503. Dial
tone is now transmitted back to the toll operator
as follows: from grounded dial tone source, back
25 contact and cam spring 5|3, armature 5|6, lower
winding of line relay 506, front contact and ar
mature 530, conductor 563, springs 604, conductor
215, condenser C, armature 233, condenser C3.
conductor 266, and from thence back over the
30 heavy talking conductors, as previously traced, to
the toll operator.
When the toll operator hears dial tone she
then dials the digit required to operate this other
local selector to seize an idle trunk extending to
the distant automatic exchange and thereafter
dials the called subscriber’s number in the distant
automatic exchange to complete the desired con
nection. In response to the first digit, or in this
case the digit 6, line relay 209 in the dial-back
40 repeater follows the impulses and deenergizes six
times. Each time line relay 209 deenergizes, the
loop circuit extending through the line relay 506
in the local' selector is opened at armature 240,
while at armature 239 and its back contact a cir
cuit is completed for energizing the series relay
205 and at the front contacts of armature 239
the circuit through the release relay 209 is mo
mentarily opened but the latter relay, being of
the slow-to-release type, maintains its arma
v50 tures attracted throughout the impulsìng series.
The circuit for energizing series relay 205 may
be traced from grounded armature 239 and back
contact, and armatures 235 and 224, through the
winding of series relay 205 to battery. Series
relay 205 is also of the slow-to-release type and
therefore maintains its armatures attracted
throughout the lmpulsing period. At armatures
230 and 23| relay 205 opens the circuit extending
back to the calling subscriber to prevent this sub
60 scriber from hearing the dial impulses and at
armature 232 short circuits the right-hand op
erating winding of the polarized shunt-field re
lay 204 in order to improve the impulsing circuit.
Slow-to-release relay 205 falls back after each
65 dialling period. At armature 232 opens the di
switches.v
l
In the local selector each time relay 506 de
energizes said relay at armature 524 completes
a circuit for operating the vertical magnet 502
and for maintaining relay 504 in energized posi
tion, as previously described. The vertical mag
net 502 in response to these impulses raises the
wipers and shaft opposite the sixth level at which
time the normal post springs are operated. The 10
off-normal springs close on the >iirst vertical step
of the shaft to prepare the circuit for the release
magnet 50| at olf-normal springs 5|0, to open
the original energizing circuit of series relay 504
now held over its upper winding, and at oil-nor
mal springs 5|2 prepares a point in the circuit
for the rotary magnet 503. After the impulsing
period the slow-to-release series relay 504 de
energizes and at armature 5|6 disconnects dial
tone and again reconnects ground. At armature 20
5|1 relay 504 prepares a point in the circuit to
release magnet 50|, at armature 5|8 opens a
point in its own circuit, and at armature 5|9
completes the circuit for operating the rotary
magnet 503. Rotary magnet 503, upon energiz 25
ing, steps the wipers into engagement with the
ñrst set of bank contacts in the sixth level and at
interrupter contacts 5|5 interrupts its own cir
cuit. The rotary magnet 503 continues to op
erate in the manner of a buzzer until such time 30
as the test wiper 54| finds battery potential on a
test contact terminating an idle outgoing re
peater to the distant automatic exchange, at
which time the circuit for the polarized switch
ing relay 501 is completed to stop further rota 35
tion of the switch wipers.
Since the local selector has been operated to
the restricted level the circuit for operating the
switching relay 501 now includes the operated
normal-post springs and the non-restricted con 40
ductor 600 inthe dial-back lineswitch as follows:
from ground by way of armature 520, back con
tact and spring 523 of the busy key, conductor
56|, springs 602, non-restricted conductor 600,
springs 603, conductor 562, front contact and
spring 53|, of the normal-post springs, upper
winding of switching relay 501, armature 525,
test wiper 54|, conductor |51, nonnally closed
springs controlled by armature | I2, armature HJ
and back contact, armature |20 and back coni“ 50
tact, and through the resistance R to battery.
Polarized switching relay 501 very quickly ener
gizes over the above-traced circuit and at arma.
ture 521 opens the circuit to the rotary magnet
to prevent further rotary operation of the wipers.
At armatures 526 and 530 switching relay 501
disconnects the line relay 506 and extends the
loop from the dial-back repeater to line relay |02
in the outgoing repeater shown in Fig. 1. At
armature 528 relay 501 closes a holding circuit GO
through its lower polarizing winding independent
of ground at armature 522 and ground at arma
ture 520, and at armature 529 prepares a circuit
to hold itself in energized position and maintain
the preceding switches operated when ground is 65
sent back from the repeater. Line relay 506,
rect loop to the dial-back switches and closes a
upon deenergizing, at armature 524 prepares a
loop in series with the right-hand operating wind
ing of shunt ñeld relay 204 and the resistance RI
in multiple; at armatures 230 and 23| reconnects
point in the circuit to the release magnet 50| and
70 the calling subscriber. The non-inductive re
sistance R2 prevents completely opening the loop
circuit to the dial-back switches during the trans
75
duces the impedance of the loop to the dial-back
fer from the direct loop to the loop in series with
relay 204. The non-inductive resistance RI re
also opens another point in the circuit to the re
lease relay 505, and at armature 525 opens the 70
circuit to the upper operating winding of the '
switching relay 501 which relay is now held in
operated position through its lower winding
alone. Relay 505, being slow to release, does not
deenergize until after ground is sent back over 75
2,105,018
conductor |51 from the outgoing repeater at
which time this ground extends by way of wiper
54|, armature 529, and armature 528 to hold relay
501 in operated position, and which ground like
wise extends by way of the busy key over con
ductor 56| to maintain this local selector busy
and to hold the dial-back lineswitch in operated
position. When release relay- 505 deenergizes
after an interval, said relay at armature 520 dis
10 connects ground from conductor 56| now ground
ed from the outgoing repeater, at armature 52|
prepares a further point in the circuit to the re
lease magnet 50|, and at armature 522 likewise
disconnects ground from the lower winding of
switching relay 501 which, however, is also
9
in the distant automatic exchange, whereupon
line relay 209 in the dial-back repeater at ar
mature 240 interrupts the circuit to the line relay
|02 in the outgoing repeater, whereupon the line
relay |02 at armature ||4 repeats the impulses
over the trunk conductors |5| and |53 to operate
the automatic switches in the> distant exchange
to complete the desired connection. At arma.
ture | I3 line relay | 02 intermittently opens the
circuit to slow-to-release relay |04 but the latter
relay, due to its slow-release characteristics isV 10
maintained energized during the impulsing pe
rîod.
When the called party in the distant auto
matic exchange answers the flow of current is 15
reversed over the trunk conductor | 5| and |53
grounded from the repeater, as previously de
scribed.
the operating winding of polarized shunt
Line relay |02 in the outgoing repeater is ener ¿ through
field relay |03 to cause this polarized relay to
gized over the following circuit when the switch
20 ing relay 501 in the local selector switches operate its armature |33. At armature |33 relay
through: from ground through the lower winding |03 completes the circuit for the reversing relay 20
of line relay |02, through the lower left-hand | 0|, whereupon the latter relay at armature || 2
winding of repeating coil RC, normally closed connects direct ground to conductor |51 to main
tain the local selector and dial-back lineswitch in
springs controlled by armature |||, conductor operated
position. At armatures || 0 and ||I re
|56, wiper 542, front contact and armature 530, versing relay
|0| reverses battery back over con 25
conductor 553, back through the loop previously
ductor |55 and |56 for operating the shunt ñeld
traced through the dial-back lineswitch and dial
back repeater to conductor 560, amature 526 polarized relay 204, which it will be remembered
is included in the loop circuit extending to the
and front contact, wiper 540, conductor |55, nor
dial-back switches.
mally closed springs controlled by armature || 0,
The reversal of current through the operating 30
through the upper left-hand winding of repeat
ing coil RC and through the upper winding of line winding of polarized relay 204 causes the opera
of this relay whereupon at armature 221 a
relay |02 tobattery. At armature H3 line relay tion
circuit is closed through the winding of switch
|02 completes the circuit for energizing release through
relay 203 and through the upper wind
relay |04, and at armature ||4 prepares a point
ing of line reversing relay 20|. At armature 228 35
in the loop circuit extending to the distant auto
relay 204 again completes the circuit for ener
matic exchange. Release relay |04, upon ener
gizing, at armature ||5 completes the circuit gizing trunk reverse relay 30| and at armature
through the polarizing right-hand winding of 229 shorts the resistance R2 at the back contact
and armature 232. At armature 223, relay 203
40 polarized shunt field relay |03, at armature | I6
upon’
energizing prepares a point in its own lock
completes the circuit for energizing switching re
40
ing
circuit,
at armature 224 opens the circuit to
lay |05, and at armature ||1 connects ground
series
relay
2.05,
at
armature
225
opens
the
cir
to conductor |51 by way of the normally closed
springs controlled by armature ||2 to maintain cuit through the upper windings of relays 2H and
2 I2, at armature 222 disconnects one of the mul
the switching relays 501 in the local selector tiple
grounds from the lower terminal of test
energized and to maintain the dial-back line
relay 3|3, at armature 225 and back contact re 45
switch operated. Switching relay |05, upon ener
the resistance R| from in multiple with
gizing, at armatures ||B and |2| disconnects the moves
rotary incoming lineswitch from the outgoing the operated winding of relay 204 to improve
transmission, and at the front contact thereof
50 trunk conductors at back contacts and at the
front contacts of these armatures completes the connects the operating winding of the polarized 50
204 directly across the trunk conductors
loop circuit ext-’ending to the distant automatic relay
exchange. At armature || 9 relay |05 opens a 215 and 216 independent of armature 240 to pre
point in the circuit to the reversing relay |0|, vent further interruption of the loop to the dial
back switches when line relay 209 is deenergized.
and at armature |20 prepares a substitute cir
The trunk reversing relay 30| is energized over
cuit for grounding armature I|1 during the in
55
terval when relay |04 is released and relay |05 the following circuit: from ground by way of ar
mature
329,
conductor
255,
armature
243
and
is falling back.
front contact, armature 228, conductor 264, and
The loop circuit extending to the distant auto
through the Winding of trunk reversing relay 30|
60 matic exchange may be traced from conductor
to battery. At armatures 3| | and 3I2 trunk re
| 5|, armature | I8 and front contact, upper right
50
hand winding of repeating coil RC, through the versing relay 30| reverses battery back over the
toll
trunk
conductors
360
and
36|
to
give
the
toll
operating winding of the polarized relay |03,
operator answering supervision in the well known
lower right-hand winding of repeating coil RC, manner.
pulsing armature H4, front contact and arma.
When the toll operator receives the answering 65
ture |2|, and by way of trunk conductor |53 to
the distant automatic exchange. The closure oi supervision indicating that the distant automatic
called subscriber has answered, the toll operator
this loop circluit in the distant automatic ex
change operates the line relay therein to prepare will disconnect by opening the circuit to relays
TÍ) the automatic switches for operation. The ñow
209 and 2|0. Relay 209 accordingly deenergizes
of current through the operating winding of the and at armature 239 and front contact opens the 70
circuit to release relay 208. At armature 239 and
polarized shunt field relay |03 is in such a di
rection that the relay does not operate its ar
mature |33 at this time. The toll operator now
back contact line relay 209 completes the locking
dials the digits of the called subscriber’s number
and at armature 240 opens the previous loop
which loop is 75
10
2,105,012
now closed through armature 225 and front con
tact. Slow-to-release relay 208, upon deenergiz
ing, at armature 236 removes one of the multiple
grounds connected to conductor |6| and to the
polarizing winding of relay 204, at armature 231
opens the locking circuit Íof tone relay 206 and
the circuit through the lower winding of line re
versing relay 20 |v which, however, is maintained in
operated position over its upper winding, and at
10 armature 238 opens the circuit to test relay 303.
Tone relay 206, upon deenergizing, at armature
233, removes the short circuit from the upper
winding of impedance 201. Test relay 303, upon
deenergizing, at armature 3|1 and back contact
15 completes the short circuit around the lower
winding of switching relay 305 and also completes
the circuit for energizing stepping magnet 301,
as previously described. At armature 3|8 relay
the distant automatic exchange to the called sub
scriber. Talking battery to the called subscriber
is furnished from the automatic switches in the
distant automatic exchange and -talking battery
for the local calling subscriber is furnished
through the windings of relay 306.
After conversation and in response to the called
automatic subscriber replacing his‘receiver, the
303 opens a point in the ring-back circuit, at ar
20 mature 3|3 opens a point in its own locking cir
cuit as well as preparing the automatic stepping
circuit for stepping magnet 301, and at armature
320 prepares another point in the stepping circuit
to stepping magnet 301. The circuit for energiz
25 ing stepping magnet 301 m‘ay be traced as follows:
from grounded armature 325 and front contact,
armature 3|1 and back contact, and through the
winding of stepping magnet 301 to battery. Step
ping magnet 301 operates its pawl preparatory to
30 stepping the wipers of the associated switch, and
at interruptor springs 332 opens the circuit
through the lower winding of switching magnet
305, as well as opening the short circuit around
the lower winding of switching relay 305. Relay
35 305 deenergizes after an interval and at armature
325 opens the circuit to stepping magnet 301 to
allow the stepping magnet to deenergize and step
the wipers one step. At armatures 326 and 331
relay 305 upon deenergizing opens the circuit ex
40 tending to the tollk operator over the toll trunk,
at armature 321 again establishes the circuit for
energizing ringing relay 304, and at armature 328
removes ground from test wiper 343 and conduc
tor 362 to make this toll trunk available for other
45 calls. The operation of ringing relay 304 is with
out eiîect at this time because switching relay
305 is not in operated position. The dial-back
repeater is now operatively disconnected from the
toll trunk which is free to be seized and used on
50 other calls.
_ The calling local subscriber and the called dis
tant automatic subscriber may now converse over
current flow over trunk conductors 15| and |53
is reversed in the well known manner. Due to
this reversal of current in the operating winding
of polarized relay |03, relay |03 deenergizes and
at armature |33 opens the circuit to the reversing
relay |0|, whereupon the latter relay at arma
tures ||0 and ||| reverses battery back through
the operating winding of polarized relay 204.
This reversal of current in the operating winding
of polarized relay 204 causes the deenergization
of the latter relay.' At armature 221 relay 204
disconnects one of the ground connections from 20
the upper winding of line reversing relay 201 and
switch-through relay 203 which relays, however,
are still maintained energized from ground at
armature 239 by way of armatures 242 and 223.
At armature 228 relay 204 opens the circuit to
trunk reversing relay 30| to restore the latter re
lay to its normal position, and at armature 229
removes the shunt around armature 232.
When the calling subscriber hangs up the cir
cuit to battery feed relay 306 is opened where
upon this relay accordingly deenergizes. At
armature 330 relay 306 opens the circuit to hold
relay 302 and ring relay 304. Relay 302, upon
deenergizing, at armature 3|3 again connects the
resistance R5 and battery to the release trunk |6| 35
through the lower winding of impedance 201 at
its back contact and at its front contact re
moves one of the multiple grounds from the con
ductor |6|. At armature 3|4 relay 302 discon
nects the remaining ground from the release 40
trunk conductor |6| to free the local selector and
lineswitch extending to the calling line, and also
opens the circuits to relays 2|| and 2|2 and the
polarizing winding of relay 204. Relay 2|2, upon
deenergizing, at armatures 249 and 250 opens the
loop circuit extending to the dial-back switches
to permit the dial-back switches including the
dial-back lineswitch and the second local selector
to release. Relay 2| l, upon deenergizing, at
armature 242 opens the circuit to switch-through 50
relay 203 and line reversing relay 20| to cause
these relays to deenergize. At armature 203
relay 2li prepares the original energizing circuit
of relay 30|, at armature 233 prepares the original
energizing circuit of dial-back relay 2|2, and at 55
armature 235 prepares a point in the stepping
circuit to stepping magnet 301. Switch-through
relay 203, upon deenergizing, at armature 223
the following talking circuit: from local subscriber
A over conductors 610 and 61|, springs 65| and
55 654, conductors 560 and 563, through the first
local selector by way of armatures 526 and 530 and
front contacts, wipers 540 and 542, conductors |60
and |62, armatures 2|8 and 215 and their front opens a point in its own locking circuit, at arma
contacts, armatures 23| and 230 and their back
ture 224 prepares a circuit to relay 205, at arma
60 contacts, condensers CI and C, back contact and
armature 232, and front contact and armatures ture 225 again prepares the circuit for relay 2|2,
250 and 249, conductors 216 and 215, dial-back at armature' 222 grounds conductor 213 to pre
pare the circuit for test relay 303, and at armature
.line switch contacts 60| and 604, the talking con
ductors extending to the second local selector ' 226 connects the resistance RI 'in bridge of the
65 which, in this case, we are assuming to be a se
operating winding of polarized relay 204. Relay
lector like the local selector in Fig. 5, and thence
by way of armatures 526 and 530 and their front
contacts, wipers 540 and 542, conductors |55 and
|56, front contacts and armatures ||0 and |||,
70 and through the left-hand windings of the repeat
ing coil RC, and from thence through the right
hand winding of the repeating coil RC and con
denser, armature ||4, front contacts and arma
tures | I8 and` |2|, and over trunk conductors |5|
75 and |53, and through the automatic switches in
20|, upon deenergizing, at armature 23| again
grounds the all-trunk-busy conductor at its back
contact and at its front contact opens the circuit
to timing relay 202, at armature 2|5 prepares a 70
point in the ring-back circuit, at armature 2|1
places a shunt around the upper winding of im
pedance 201, and at armatures 2|6 and 2IB re
stores the talking conductors to normal posi
tion. Timing relay 202 upon energizing at 75
2,105,012
armature 22| opens a point in the circuit to tone
relay 206. >
'
The disconnection ofA ground from release con
ductor | 6| by the deenergization of release relay
302 opens the holding circuit to the switching
relay 501 in the ñrst local selector and to the
plunger coil 646 of the local line switch, where
upon the relay and coil deenergize. Relay 501,
upon deenergizing, completes the circuit for the
10 release magnet 50| to cause the selector to re
lease in the same manner as previously described.
The ldcenergization of the plunger coil 646 in the
local lineswitch causes the local lineswitch to re
store in the well known manner.
15
.
When the loop to the dial-back lineswitch is
opened at armatures 209 and 250 by the deener
gization of relay 2|2, relay |02 in the outgoing
repeater deenergizes. Relay |02, upon deenergiz
ing, at armature H3 opens the circuit of release
20 relay |04 and at armature ||I|_ opens the loop ex
tending to the distant automatic exchange to re
lease the automatic switches therein in the well
known manner. Release relay |04, upon deener
gizing, at armature | I5 opens a circuit extending
through the polarizing winding of relay |03, at
armature ||5 opens the circuit to switching relay
|05, and at armature | i1 substitutes the ground at
armature |20 for the ground at armature |!1 for
maintaining the release trunk |51 grounded by
30 means of which the second local selector and the
dial-back lineswitch is maintained in operated
position. Switching relay |05, upon deenergizing,
at armatures I |8 and |2| connects the trunk con
ductors |5| and |53 to the incoming rotary line
35 switch, at armature |20 and front contact dis
connects ground from release trunk conductor | 51
to open the circuit to the switching relay in the
second local selector and the plunger coil in the
dial-back lineswitch, and at the back contact
40 connects battery through the resistance R so that
the outgoing repeater may be seized for other
outgoing calls.
When ground is disconnected from release
trunk conductor |51 the second local selector
45 seized by the dial-back lineswitch and this line
switch are released by the deenergization of the
switching relay, similar to switching relay 501,
and by the deenergization of the plunger coil 6|6.
Since the release of the dial-back lineswi‘tch and
the second local selector seized by such line
switch is similar to the release of the local line
switch and the ñrst local selector, a further de
scription of the releasing operation will not be
given. All of the apparatus now used in extending
c1 Si and completing a call between a local calling sub
scriber to a distant called automatic'subscriber
by the aid of the toll operator are now in normal
position and may be used on subsequent calls.
60
It will now be assumed that an automatic sub
scriber in the distant automatic exchange, desires
to talk with an automatic subscriber in the local
exchange. In this case the distant automatic
subscriber operates the distant automatic switches
to seize one of the idle trunks extending to the
local exchange and it will therefore be assumed
that the trunk conductors |5| and |53 are the
trunk conductors engaged by the distant auto
matic switches in initiating this call. When this
trunk is seized, a bridge is closed across the con
70 ductors |5| and |53 at the distant automatic ex
change to complete the energizing circuit for line
relay |08 of the incoming lineswitch as follows:
from ground through the lower winding of line
relay |08, back contact and armature |24, back
75 contact and armature |2|, trunk conductor |53
11
through the loop in the distant automatic ex
change to trunk conductor |5|, armature ||8 and
back contact, armature | 22 and back contact,
and through the upper winding of line relay |08
to battery. At armature |21 relay |06 completes
an energizing circuit for the stepping magnet
|09 from grounded armature I 2B and at armature
|20 completes the circuit for energizing the slow
to~operate relay |01. Stepping magnet |09, upon
energizing, positions its pawl preparatory to step 10
ping the wipers of the incoming rotary lincswitch,
and at interrupter springs |29 opens a point in
its own automatic stepping circuit. After an in
terval slow-to-operatc relay |01 energizes and at
armature |25 prepares a point in the automatic
stepping circuit of magnet |09. At armature |26 15
and back contact relay |01 opens the circuit to
stepping magnet |09 and its front contact pre
pares a point in the energizing circuit of switch~
ing relay |06 and also completes the circuit for
energizing reversing relay |0| by way of arma
ture ||9. Reversing relay |0| at armature ||2
connects ground to the release trunk conductors
|52 and |51 to mark this outgoing repeater busy
to the monitoring and local selectors. Stepping 25
magnet |09, upon deencrgizing, steps the wipers
|30 to |32, inclusive, one step into engagement
with the next set of bank contacts, and at arma
ture |29 completes a circuit for energizing switch
ing relay |06 or for short circuiting this latter 30
relay dependent upon the idle or busy condition
of the dial-back repeater terminating in this set
of bank contacts.
In case the dial-back repeater terminating in
this set of bank contacts is in use, then ground 35
will be connected to the release conductor |6|
whereupon a circuit may be traced for short-cir
cuiting the switching relay |06 as follows: from
grounded release trunk conductor, test wiper |3|,
armature |23 and back contact, armature |25,
through the winding of switching relay |06 to
ground at armature |26. 'I‘he switching relay
|06 is prevented from operating over this circuit
and this same ground from release trunk con
ductor extends through the interrupter springs
|29 and the winding of the motor magnet |09 to 45
energize the magnet. Motor magnet |09 there
upon energ‘ :es from ground engaged by the test
wiper |3| and causes the wipers to step on the
decnergization thereof to engage another set of
bank contacts terminating another dial-back re~ 50
peater. This stepping operation continues as long
as test Wiper |3| encounters a grounded bank
contact.
As soon as the test wiper |3| engages a bank
contact having no ground potential thereon then
the switching relay |06 energizes in series with
the marginal stepping relay |09 as follows:
ground by way of armature |26 and front contact,
winding of switching relay |06, interrupter spring
|29, and through the winding of stepping magnet
|09 to battery. Due to the high resistance of the
winding of switching relay |05 stepping magnet
60
|09 is not energized in this circuit. Switching
relay |06, upon energizing, at armature | 23 con 65
nects ground by way of armature |26 and test
wiper |3| to release trunk conductor |6| to make
this dial-back repeater busy to the local selectors,
and at armatures |22 and |24 and back contacts
disconnects line relay |08 and at the front con
70
tacts connects the trunk conductors |5| and |53 to
trunk conductors |10 and |12, whereupon a cir
cuit is completed for energizing the battery feed
relay 306 as follows: from ground by way of the
upper winding of relay 306, conductor 268, nor
2,105,012
12
326 and 33| connects generator out over the toll .
mally` closed springs controlled by armature 2| 0, _trunk
conductors to signal the toll operator.
conductor |12, wiper |32, front contact and arma
Slow-to-release relay 304 deenergizes shortly af
ture |24', back contact and armature |2|, con
ter the operation of switching relay 305 toidis
-ductor |53, through the distant- loop, conductor connect ringing current and connect> the toll
|5I, armature Hl and` back contact, armature trunk to the windings of differential relay 2|0
|22 and front contact, wiper |30, conductor |10,
'
normally closed .springs controlled by armature > and line relay 209.
When the toll operator answers in response to ,
2|6,' conductor 269, and through the lower wind
_ing of battery feed relay 306 to battery.
Relay 306, upon energizing, at armature 329
completes the energizing circuit for trunkV revers
ing relay 30|, and at armature 330 completes the
circuit for energizing hold relay 302 and ring relay
304, as previously described. At armature 3|3,
15 relay 302 grounds the test conductor |6| by way
of the busy key springs 334, conductor 26|, and
the lower winding of yimpedance 201 to hold the
switching relay |06`in the incoming lineswitch
in operated position after the release relay |01
20 deenergizes which it does shortly after the release
10
of line relay |00. ' This ground on release trunk
conductor |6| extends through wiper |3|, arma
ture |23 and front contact to switching relay |06.
Line relay |00 deenergizes in response to the
25 operation of switching relay |06, and at armature
|20 opens the circuit to release relay |01 and at
armature |21 opens the original energizing cir
cuit of stepping-magnet |09. Release relay |01
in addition to being slow to operate is likewise
30 slow to release and therefore ground at arma
ture |26 is not removed from the winding of
' switchingjrelay |.06ßuntil ground is sent back over
test conductor |6I, as previously described.
Relay 302 also at armatures 3|5 and 3|6 pre
36 pares 4the circuit as previously described for op
erating the test relay 303 in case the wipers of
the switch associated with the dial-back repeater
are in engagement with an idle trunk or com
plete the circuit for energizing the marginal step
ping magnet 391 in case the test wiper 343 en
40 gages a grounded bank contact indicating that
this particular toll trunk is busy. Since this op
eration is the same as previously described it is
not thought necessary to give the detailed opera-V
tions thereof. When test relay' 303 energizes in
45 response to the associated switch engaging an
idle toll trunk test relay 303 energizes and at
armature 3|0 connects the ring-back tone to the
calling subscriber over the following circuit: from
interrupted generator connected to the multiple
50 connected bank contacts accessible to wiper 340
through the ring-back condenser, armature 3|3,
conductor 263, armature 2 I 5, conductor |10, wiper
|30, front contact and armature |22, armature
H8, conductor |53, to- the distant automatic
55
exchange.
_
At armature 320, relay 303 connects ground by
way of armature 22, conductor 213, and armature
3|5 to test wiper 343 to ground conductor 362
thereby marking this toll trunk busy to other
00
dial-back repeaters. Test relay 303 also at arma
ture 3|9 locks itself in the same manner as pre
the splash of ringing current, line relay 209 en
ergizes and at armature. 239 completes a circuit 10
for energizing relay 208. Relay 208 at armature
236 grounds the release trunk conductor |6|
through the lower winding of impedance 201, at
armature 231 completes the- circuit through the
lower winding of reversing relay 20|, and at ar
mature 238 grounds conductor 214 to hold the
test relay 303 in operated position. Relay 20|
energizes and reverses battery back to the call
ing distant automatic exchange at armatures 2|6
and 2|8, opens the ring-back circuit at armature 20
2|5, and at amature 2|3 completes a circuit for
the timing relay 202. Relay 202 oœrates and
vibrates its weighted spring 220, whereupon slow
to-operate relay 206 is energized after a predeter
mined time. The circuits for operating relays
209, 206, 20|, and 202 and 206 are the same as
previously described andhave not therefore been
traced in detail.
l
A talking circuit is now completed between the
distant automatic subscriber and the toll -oper 30
ator as follows: trunk conductors |5| and |53,
armatures ||8 and |2| and their back contacts,
armatures |22 and |24 and front contacts, wipers
|30 and |32, conductors |10 and |12, armatures
230 and 23|, armature 233, condensers C3 and
C2, conductors 266 and 261, armatures 3|2 and
3|| and front contacts, resting contacts and ar
matures 323 and 322, armatures 33| and 326, wip~
ers 342 and 34|, and by way of the toll trunk
conductors 36| and 360 to the toll operator. Talk
ing battery to the toll operator is furnished
through the windings of line relay 209 while talk
ing battery through the windings of relay 306 is
furnished to the distant automatic subscriber.
The toll operator may extend the call to a 45
distant exchange or «may call back through the
dial-back switches in this local exchange by mo
mentarily unbalancing the line to operate differ
ential relay 2|0 and‘thereafter dial the local sub~
scriber’s number to cause the operation of the 50
dial-back lineswitch, the local selector and con
nector to complete the connection to the desired
local line in the same manner as previously de
scribed. The talking circuit between the distant
calling subscriber and the local called subscriber 55
extends over the trunk conductors |5| and |53,
conductors |10 and |1| to armatures 230 and
23|, as previously traced, and thence by way of
condensers C and C|, armature 232 and back
contact, armatures 249 and 250, conductors -216
and 216 and through the dial-back lineswitch,
local selector, and local connector to the called
viously described. At armature 3|1 relay 303
connects the high resistance common relay 31|
in series with the lower winding of switching
65 relay 305 and the winding of `stepping magnet
301. Relay 31| alone energizes over this circuit
to cause the operation of the A. C. relay 216 which
local subscriber’s line. After completing the con
nection over the dial-back lineswitch, the local
tion of relay 314. After an interval relay 314
70 connects ground to armature 313 and conductor
310 whereupon the switching relay 305 is ener
scriber «and the local called subscriber replacing
their receivers the dial-back lineswitch, selector
selector and connector, and the called subscriber 65
has answered, the toll operator may disconnect
and free her toll trunk for other uses in the same
manner as previously described. After conver
in turn at armature 315 completes the energiza- ' sation, and responsive to the distant calling sub
gized -as previously described.
Switching relay
305 therefore energizes a short time after the
energization of test relay 303 and at armatures
and connector in the local exchange and the dial
.back repeater are released in the same manner as
previously described when the calling subscriber
opens the circuit to relay 306. When the dial
2,105,012
back repeater has released ground is removed
from conductor |6|, thereby opening the circuit
of switching relay |06. The removal of ground
from release trunk conductor |6| alsoI opens the
circuit through reversing relay |0| whereupon the
latter relay at armature ||2 disconnects ground
from release trunk conductors |52 and |51 to
again mark this outgoing repeater as being idle.
The restoration of the switching relay |06 again
10 prepares the incoming lineswitch for use on fur
ther incoming calls over this trunk conductor.
In case the toll operator dials the wrong num
ber, if a dead number is encountered, or if for
some other reason the toll operator is unable to
15 complete the desired connection she may release
the dial-back switches by momentarily grounding
both conductors 360 and 36| to operate the dif
ferential relay 2|0 a second time. In order to
describe this operation it will be assumed that
20 the dial-back lineswitch in Fig. 6 and the local
selector in Fig. 5 have been operated and for
some reason clue to wrong dialling or otherwise
the desired connection cannot be completed. In
. the dial-back repeater in Figs. 2 and 3 it will be
remembered that certain relays will be operated
at this time before the called party answers,
namely: relays 20|, 202, 206, 208, 209, 2||, 2|2,
302, 3|3, 305, and 306. Now when the toll op
erator grounds the toll conductors 360 and 36|
30 differential relay 2|0 is again operated in the
same manner as previously described. Since re
_
13
viously- described. At armature 248 relay 2|2‘
completes the circuit for operating relay 2||
when the short circuiting ground is removed by
the deenergization of the differential relay 2|0
as previously described. The operation from here
on is the same as previously described.
From the foregoing it will be seen that when
the toll operator completes either incoming or
outgoing calls between the local and distant au
tomatic subscribers’ lines, the toll operator is dis 10
connected from these established connections
and it is therefore desired to provide the toll
operator with some means for ascertaining the
idle or busy condition of the trunk lines con
necting the distant and local automatic ex 15
changes. The monitor selector shown in Fig. 4
is therefore provided in order for the toll operator
to determine thc idle or busy condition of the
trunk lines connecting the two automatic ex-changes. Assuming now that the toll operator 20
Wants to test the idle or busy condition of the
trunk lines connecting the two automatic ex
changes, then the toll operator will select one
of her toll trunks extending to the local auto
matic exchange and in this case it will be fur 25
ther assumed that the trunk conductors 380 and
36| are the conductors of the trunk line selected.
'I'he toll operator in selecting this trunk line
throws a bridge across the conductors 360 and
36| thereby completing a circuit for energizing 30
line relay 620 of the incoming toll lineswitch as
follows: from ground through springs 624, con
lays 2|| and 2| 2 are operated at this time the
operation of armature 24| by diiîerential relay ductor 36|, through the toll operator’s bridge,
2|0 completes a circuit through the upper Wind
conductor 360, springs 623 and through the
ings of relays 2|| and 2|2 as follows: from winding of line relay 620 to battery. Since the
35
grounded armature 239 and front contact, arma
operation of the incoming toll lineswitch is sim
ture 24|, armature 245, armature 244 and front ilar to both the dial-back lineswitch and local
contact through the upper winding of relay 2|| lineswitch, the operation of line relay 620 causes
and by way of armature 241 through` the upper the plunger coil 626 to operate and select an
winding of differential dial-back relay 2| 2. The idle local selector. Assuming further that the
circuit traced through the upper winding of local selector in Fig. 5 is the selector seized by 40
relay 2|| malntains this relay in energized posi
the plunging of the incoming toll lineswitch.
tion, while the circuit through the upper dif
When the toll operator hears dial tone trans
ferential winding of dial-back relay 2|2 causes mitted from the seized selector, she will operate
the differential dial-back relay 2|2 to deener
the local selector opposite the eighth level to
gize, since the- upper and lower windings now seize the monitor selector in Fig. 4 in the same 45
oppose each other. At armatures 241 and 248 manner as previously described.
relay 2|2 simultaneously opens the circuit
When the local selector switches through in
through both its windings and in addition at response to' the operating of switching relay 501,
50 armature 248 opens the circuit through the lower
line relay 406 in the monitoring selector is en
winding of relay 2| I which relay, however, at this ergized over the following circuit: from ground 50
time is held energized through s upper Winding through the lower Winding of line relay 406, nor
alone. At armatures 249 and 250 relay 2|2 opens mally closed springs controlled by armature 425,
the loop extending to the dial-back lineswitch conductor 462, wiper 542, front contact and arma
and local selector and connector to cause these ture 530, conductor 563, contact 635, conductor
switches to release in the same manner as pre
36|, through the bridge at the toll operator’s po 55
viously described. The toll operator now re
sition,
conductor 360. springs 63|, conductor 560,
moves the unbalancing ground condition from armature 526 and front contact, wiper 540, con
conductors 360 and 36|, whereupon differential
At armature 24| relay
60 relay 2|0 deenergizes.
2|0 opens the circuit through the upper winding
of relay 2| I, whereupon this relay now deener
gizes. Relay 2|| at armature 243 completes the
original energizing circuit of trunk reversing
relay 30| which thereupon operates and reverses
battery to the toll operator as previously de
scribed.
The toll operator may now reoperate the dial
back lineswitch by again connecting ground to
both conductors 360 and 36| to reenergize the
diiierential relay 2|0. T'he operation of relay
2 I0 at armature 24| causes the operation of relay
2|2 which at armatures 249 and 250 closes a loop
circuit to the dial-back lineswitch to cause it to
plunge and seize an idle’local selector, as pre
ductor 460, normally closed contacts controlled
by armature 423, and through the upper winding 60
of line relay 406 to battery. At armature 428
line relay 406 completes the circuit for the slow
to-release relay 405. At armature 426 relay 405
connects ground to release trunk conductor 46|
to maintain the polarized switching relay 501 and
the pull-down coil 626 in operated position to 65
maintain the local selector and incoming toll line
switch in operated position, and at armature 421
connects ground to armatures 4|4 and 4 I9.
The toll operator now dials the digit 1 in order
to supervise the ñrst trunk line connecting the 70
two automatic exchanges. In response to this
digit, or digit 1, line relay 406 deenergizes and at
armature 428 kcompletes the circuit for energizing
slow-to-release relay 403 as follows: from ground 75
14
2,105,012
by way of armature 428 and back contact, arma
ture 429, and through the winding of slow-to
release relay 403 to battery. At armature 42|
relay 403, upon energizing, opens the circuit of
reversing relay 404, and at armature 422 com
pletes a circuit through the upper winding of
trunk No. I relay 402 to operate this relay in
its first step to close its “X” contact at armature
4|9. This circuit may be traced as follows: from
10 ground by way of armature 428 and back contact,
amature 429, armature 422, armature 4|8l and
back contact, and through the upper winding of
relay 402 to battery. Relay 402 operates its
armature 4|9 to complete a holding circuit for its
upper winding and at the same time short cir
cuits its lower winding from ground at armature
421 to ground at armature 428. When line relay
406 energizes after this impulse, ground at arma
ture 428 is removed from the winding of series
20 relay 403 and the windings of relay 402, where
upon the two-step relay 402 energizes in its’sec
ond step over the following circuit: from ground
by way of armature 421, armature 4|9, through
the lower- winding of two-step relay 402 land
through the upper winding to battery. Relay
402 operates its remaining armatures and at ar
matures 4|6 and 420 connects the talking con
ductors 460 and 462 by way of armatures 4| I and
4|5 and back contacts to conductors |5| and |53
30 extending to the distant automatic exchange. At
armature 4|1 two-step relay 402 prepares a point
in the circuit to the reversing relay 404. At
" armature 4|8 relay 402 prepares- a point in the
circuit for energizing trunkk No. 2 relay 40|.
Shortly after the impulsing period, series relay
403 deenergizes and at the normally closed springs
controlled by armature 42| completes the circuit
for energizing the reversing relay 404 in case ,the
ñrst trunk line to the distant automatic exchange
40 is busy.
In this case ground'will be connected
to test conductor |52, -thereby completing the
energizing circuit for relay 404; from grounded
conductor |52, back contact and armature 4|2,
armature 4|?, normally closed springs controlled
by armature 42|, and through the winding of
reversing relay 404 to battery. At armature 424
relay 404 prepares a locking circuit for itself and
at armatures 423 and 425 reverses battery from
the windings of the line relay 406 back over the
50 toll trunk conductors in order to advise the o`p
erator that the first trunk line is busy. If de
sired, the toll operator may converse with the
subscribers in the established connection or may
camp on this connection until such time as. the
ci Cn subscribers release whereupon groundis removed
from conductor |52 to cause the deenergization
of reversing relay 404 which thereupon again re
verses battery back over the talking conductor to
the toll operator advising such operator that the
60 first trunk line is now idle and may be used on
other calls.
If desired the toll operator may transmit .an
other impulse to line relay 406 to test the idle or
busy condition of the second trunk line. In re
65 sponse to this impulse " line relay 406 again de-`
energizes and again completes the circuit for
series relay 403 and at the same time completes
the circuit for energizing two-step relay 40| in
its ñrst step to operate armature 4|4. The cir
70 cuit. for operating relay 40| in its ñrst step may
be traced as follows: from ground by way of ar
mature 428 and back contact, armature 429, ar
mature 422, armature 4|8 and front contact, ar
mature 4|3 and back contact, through the upper
75 winding of relay 40| to battery, At this time relay
40| operates only- its armature 4|4 to complete
a short circuit around its lower winding extend
ing from ground at amature 421 and ground at
armature 428. When line relay 406 energizes
after this impulse, the circuit to series relay 403
is opened and the short circuit around the lower
winding of two-step relay 40| is removed with the
result that relay 40| operates through its second
step to operate its remaining armatures. When
series relay 403 energized in response to the sec- ’
ond impulse, said relay at armature 42| com
pleted the locking circuit for reversing relay 404
and at armature 422 completed the previously
traced circuit for relay 40|. At armature 4|2
relay 40|, upon operating through its second step,
disconnects' test conductor |52 of the first trunk
and connects up test conductor |52' of the sec
ond trunk and at armatures 4|| and 4|5 discon
nects the talking conductors of the first trunk~
and connects up the talking conductors of the 20
second trunk. At armature 4|3 relay 40| opens
the original energizing circuit to upper winding
of relay 40| and transfers the impulsing >circuit
to a succeeding relay in case there are more than
two trunks connecting the two automatic ex
changes. Shortly after the second impulse trans
mitted by the toll operator, series relay 403 de
enegizes and at armature 42| connects the re
versing relay 404 to the test conductor |52'. In
case the second trunk is busy ground on conductor
|52' will maintain the reversing relay energized
to maintain the reversed battery connection to
the toll operator, thereby advising the toll oper
ator that the second trunk is likewise busy. In
case the second trunk line is not busy then no
circuit is completed for reversing relay 404 with
the result that relay 404 deenerglzes and restores
normal talking connections to the toll trunk there
by advising the operator that the second toll
trunk is idle. From the foregoing it is therefore
seen that by use of the monitor selector the toll
operator is enabled to connect with the trunk
lines connecting the two automatic exchanges
regardless of their idle or busy condition and may
converse thereover in case the trunk lines are
1n use.
Incoming toll calls from the toll switching cen
ter to local automatic subscribers are handled
through the incoming toll lineswitch and the
local selector and connector, while incoming-toll
calls from the toll switching center to the dis
tant automatic exchanges are handled by the
incoming line switch, local selector, and the out
going repeater to the distant automatic exchange.
The operation of the local selector and outgoing
171 L1
repeater is the same as previously described, ex
cept in this case no dial-back repeater is included
ln the circuit as the local selector when used by
the toll operator connected with the 'outgoing
repeaters direct.
'
`
(il)
Having described the invention, what is con
sidered to be new and is desired to be protected
by Letters Patent is set forth in the following
claims.
What is claimed is:
1. In a telephone system, a distant exchange,
a local exchange, and a toll exchange, trunk lines
connecting the distant and local exchanges, dial
back repeaters in the local exchange, a hunting
switch individual to each said trunk line having ”
access to said repeaters, toll trunk lines connect
ing the local and toll exchanges, a selecting switch
individual to each said repeater having access
to said toll trunk lines, automatic subscribers’
lines terminating in said local exchange, local 75
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