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Патент USA US2132857

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Oct. 11, 1938.
Filed March 16, 1937
5 Sheets-Sheet l
Oct. 11, 1938.
Filed March 16, 1937
3 Sheets-Sheet 2
‘Oct. 11; 1938. -
" 2,132,857
Filed March 16, 1937
5 Sheets-Sheet 3
‘ grroR/wsy
Patented Oct. 11, 1938
Albert G. Lang, Whitestone, and Thomas H.
Neely, StewartManor, N. Y., assignors to Bell
Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application March 16, 1937, Serial Nb. 131,144
3 Claims. (01. 179-27)
This invention relates to telephone systems and
more particularly to semiautomatic telephone
An object of the invention is to facilitate the
_ completion of calls through a toll switchboard to
subscribers’ lines in’ an automatic community
(unattended) exchange over operators’ connect
ing ,(cord) circuits primarily arranged for com
‘ pleting calls over trunk circuits to subscribers’
10 lines in main automatic exchanges at which ex
changes a reversal of the line battery occurs when
the ?nal selector switch connects with the called
time and tends to slow up the service, particularly
when a considerable number of such calls are
completed at certain hours of the day.
A speci?c object of the invention is therefore to
provide facilities whereby a single cord circuit
can be interchangeably used to complete calls to
trunks of either of the above described types
without any of the objections above described.
A feature of the invention whereby the forego
ing specific object is obtained, resides in such
modi?cations of the present operator’s cord and
position circuits and community o?lce trunks that
upon completion of dialing on a community office
In toll switchboard cord circuits adapted for
15 luse with trunks of the above-described latter type,
the dial circuit, once ‘it is connected to the cord
circuit, remains associated therewith until the
before-mentioned reversal occurs at which time
a polarized relay operates in the toll operator’s
V iolposition to disconnect the dial circuit from the
The circuits of what are commonly known as
community dial o?ices, i. e. relatively small un
attended satellite of?ces, are in some cases not
25'; arranged to transmit a battery reversal when
the switch connects with the called line and hence
a toll cord arranged to function with trunks to a
main exchange over which a reversal occurs when
the called line is seized could not be operated in
trunk, and the releasevof a. positional dial key,
the trunk conductors at the toll o?ice will be 15
reversed to supply line battery to the cord in a
reversed direction thereby operating a polarized
relay in the position dial circuit to disconnect the
dial circuit from the cord and condition the cord
circuit for conversation in the'same manner as 20
when the call is extended to a main exchange and
connected to the trunk, the dial is connected and
the speech transmission circuit through the cord
is opened, all'under control of a polarized relay in
$51‘: the position circuit which only operates when
the line battery is reversed.
To overcome this dii‘?culty, in the past, it has
been the custom, when community of?ce trunks
are present in the same switchboard with trunks
4.0‘ to main exchange, to provide a special dial jack
for each community o?ice trunk and, when a call
is to be extended thereover, after plugging up the
main trunk jack with the cord circuit to be used
in completing the connection, to plug another
cord circuit, from that over which the connection
7 is to‘bebompleted, into the dial jack.
The oper
ator then operates the dial key and actuates the
dial now associated with this other cord and upon
the completion of dialing removes this other cord
50 'from the dial jack whereupon a talking connec
tion is established by means of the ?rst cord. By
this sequence of operation, the operator is enabled
to complete calls over both types of trunks, but,
in the case of connections to community o?ice
7 55ytrunks, the double handling of cords consumes
the following description and accompanying 25
drawings, Figs. 1, 2 and 3, which ?gures, when
arranged as shown in Fig. 4, represent a toll oper
ator’s cord circuit together with its associated
position and dial circuit (as shown in Figs. 1
t the same manner when connected to a community _ and 2)
o?ice trunk for the reason that once the cord is
battery reversal , automatically
thereat when the called line is seized.
Other features will appear hereinafter from
adapted to be connected to either a
standard trunk circuit terminating at an auto
matic central office, arranged to reverse the bat
tery supply to the cord when a called line is
seized, or tobe connected to, a trunk circuit ex
tending to a so-called community dial of?ce not
so arranged, as shown in Fig. 3.
' Fig. 1 of the drawings shows the position dial
circuit. Fig. '2 shows a cord circuit with the
operator’s telephone circuit, and Fig. 3 shows
the outgoingjack of a standard out-dial trunk to 40
an automatic exchange and the circuit at the out
going end of a trunk to a community dial office
arranged to simulate a battery reversal back
into a connected dial circuit when‘ the position
dial keyis released at the termination of the dial
ing operation.
A description of the operation of thecircuits
of this invention follows:
Assuming that the operator is what is known
as an inward operator and has answered a call by
inserting the rear plug of her cord circuit C, Fig. 2,
into a calling toll line, not shown, and desires
to extend the connection to a station in an auto
matic o?ice reachedover trunk l0, she will ?rst
operate'the trunk dial key I thereby operating 55
' 2
relay 2 in a circuit which can be traced from
line, if the line is idle, current flowing back over -
ground, contacts 3 or‘ key I, contacts 4 of relay 5,
the trunk to the dial circuit is reversed thereby
contacts 6 of key i and winding of relay 2 to
causing polarized relay I’! to operate.‘ Operation
battery. Relay‘Z in operating connects battery
of this relay opens the circuit including relays it,
ill and I2 thus permitting relays i9 and i2 to re
to leads ‘l1; ‘52, etc., to operate dial relays, such as
' l2, individual to the respective cords in the posi—
tion, when the front plug 9 of the cord is con
nected to an out-dial trunk such as H].
Trunk ‘I0 is a standard out-dial trunk oi‘ the
type fully described in Patent 1,653,789. to
Relay 52 in releasing disconnects the trunk
from leads 3! and 32 extending into the dial cir
cult, opens contacts l5, and closes contacts 3d
and 35. Closure of contacts 34 connects the tip 10
of plug 5 through to the upper armature of relay
Stokely dated December
1927 and shown in
Figs. 2 and 3 thereof and therefore will not be I I5 anclclosure of contacts 35 connects'sleeve relay
33 to the plug sleeve whereupon relay 83 operates
redescribed here.
By referring to the above patent it will be noted to ground over the sleeve of the trunk. Relay 33
15 that the ring conductor of ‘the trunk jack 2% in operating closes an obvious circuit to operate 15
relay l5 which relay closes its inner upper and
shown in Fig. 2 is grounded through the left
hand winding of relay 262 and consequently when lower contacts to connect the tip and ring'of
the plug 9 of the present cord is insertedin jack plug 9 through to the cord.
Release of relay l9 releases relay 2| and if the
H, which corresponds to jack 296 of the Stokely
20 patent, a circuit is completed to operate the dial ' operator released dial key 8 at the conclusion of 20
the dialing operation, relay 5 will new release
relay i2 which can be traced from battery, con
tacts Q3 of relay 2, lead 1'1, upper winding of relay thereby extinguishing lamp 26 which completely
l2, contacts ill of relay [5, and the ring conductor restores the dial circuit to normal and conditions
of the plug 9 and jack H to ground in the trunk the cord for conversation.
25 circuit, as previously mentioned.
Call to a community dialomce
Dial relay l2 operates in this circuit, discon
nectsrelay 33 from the plug sleeve, and at its
contacts l6 completes a holding circuit for itself,
including its lower winding, which can be traced
30 from battery, contacts of polarized relay l1, re
In case the called subscriber is reached over a
trunk to a so-called community dial of?ce'which
is not arranged to send a current reversal back to
operate polarized relay I? to release the dial cir 30
lays !8 and IQ, lead 29, lower Winding and con
cuit from the cord when (the called subscriber’s
tacts E6 of relay l2, sleeve conductors of plug 9
and'jack H to ground over the left-hand contacts
line is reached, some means must be provided to
simulate such a reversal in order to free the dial
of relay 202 and the right-hand winding of relay
35. 283 shown in the above-noted Stokely patent.
Qperation of relay l2 also connects, at its con
tacts 29 and 36, the tip and ring conductors of the
trunk to leads 3i and 32 extending to the dial
circuit of Fig. 3.
Relay i8 is marginal and does not operate in
the above traced circuit but relay l9 and trunk
relay 263 do operate which latter relay, it will be
observed, operates relay 2E3] to extend the trunk
to pulsing relay 2M thereby connecting ground
45 and battery respectively to the tip and ring con
ductors of the connected cord plug 9.
Relay ill in operating causes thesuccessive op
eration of relays 2i and 5, The latter relay locks
up over its contacts 22 to ground on the dial. key
1, opens the operating circuit of relay 2 and at
its contact 23 closes a circuit from the dial 2G over
lead 3i and contacts 29 of relay E2 to the tip con
ductor of the cord plug 9. When relay, 2 releases
it disconnects battery from lead 71 and all other
- corresponding leads to other cords thereby open
circuit and condition the cord for conversation
and to accomplish this the trunk T (Fig. 3) has 35
beenprovided, the operation of which is as fol
When the operator desires to reach a commu
nity dial of?ce subscriber, she ?rst operates dial
key l as before described, thereby operating relay 40
2 which connects battery over leadsli, l2, etc. to
operate the respective dial relays such as l2 when
the respective plug, such as 9, is inserted'in trunk
jack 3% at which time a circuit is completed to
operate relay 12 which can be traced from bat 45
tery, contacts l3 of relay 2, lead '11, upper winding
of relay 52, contacts id of relay 15, ring conduc
tors of plug 9 and jack 36, contacts 3? of relay
38, contacts 39 of relay I30 and lower winding of
relay 6! to ground. Relays l2 and ii operate in
. this circuit.
Operation of relay‘ 12 extends the
tip and ring of the plug 9 to the dial circuit (Fig.
1) over its contacts 29 and 39 and leads]?! and 32,
and prepares a locking circuit for itself at con
tacts it. Relay 4! inaoperating operates relay 42 55
ing the circuits previously traced which caused r in a circuit which can be traced from battery,
operation of relay 202 in the trunk. Relay I2, - contacts of polarizedrelay ll of the dial circuit,
windings of relays l8, l9 and the locking winding
however, remains locked up over its lower wind
and contacts lb‘ of relay l2, sleeve of the plug 9
ing as previously described.
. . .
Relays l9, 2! and 5 are su?iciently slow in and jack 3%, contact 43 of. relay 4! and lower
operating, however, to permit relays 2m and 262 V winding of relay 42 to ground.
In the standard out-dial trunk IE, before‘dis
in the trunk to lockup before the original operat
ing circuit for relay 292 is opened by the release 7 cussed and described in Patent 1,653,789, the
right-hand winding of sleeve relay 293 is of su?i
of relay 2. Release of relay'Z closes, at its con
tact 25, a circuit to light the dial pilot lamp 25 ciently'high resistance to prevent operation of
which can be traced from battery, contacts 25 of marginal relay l8 in the dial circuit, but the lower
winding of sleeve relay A2 in the community trunk
relay 2, contacts 7270f relay 2%, lamp 28 andcon
tacts 22 of relay 5 to ground over contacts 3 of T (Fig. 3 or‘ the present application) is made low'
dial key I.
enough to permit this relay (A) to operatethere
The circuit is now inrcondition for dialing and by closing a circuit to operate relay '15 which can
actuation of the dial 2% transmits pulses over the be traced from battery’, winding of relay 15, con
trunk to operate vthe pulsing relay 266 in the tacts of relay l8 and the upper normal contacts
trunk as shown in Patent 1,653,789. As described of the dial to ground. Operation of relay 15 opens
in the above patent, when the connector switch at its contact 76 the normal short-circuit around
75 in the distant o?ice comes to rest onthe'called resistance’ 17 and closes its contact 18 thereby
transferring the lead 19, which extends'lto ground
through the transformer winding 80 of the oper
ator’s induction coil in the telephone circuit OT,
shown at the bottom of Fig. 2, from the lead 8|
normally connected to the tip of the plug 9, to the
lead 32 and thence to the ring conductor of the
trunk in order to receive dial tone from the dis
tant'community office 'over the ring conductor of .
the trunkh Relay l9 also operates in this circuit,
as previously described, which operates relays 2|
and 5 in turn. Relay 5 releases relay 2 which
completes the circuit of dial pilot lamp 26'. Relay
The resistance of this circuit, due to resistance '
11, is such that marginal relay'51 does not oper
ate, but pulsing relay 51 does operate, over its
lower winding, thereby closing its lower contact
86lto operate relay 81 in an obvious circuit.
Relay 31 in operating closes its locking contact
88. thereby completing a locking circuit for itself
from ground at contact 89 of relay 54, and at its
co'ntact‘90 short-circuits the lower, and high re
sistance, winding of relay‘ 9| thereby decreasing 10
the resistance of the loop to the community dial
office su?iciently to operate a marginal line relay
5 in operating also closes its contacts 23 which thereat, not shown, thereby causing the circuit at
extends lead 3| to the dial 24. With relay I2 ‘that point to be conditioned to ‘receive dial pulses,
16 operated and locked when relay ‘5, which is slow
in a well-known manner, and as trunk T is a two
to operate, ?nally closes its contacts dial 24 is con— way circuit, to make the outgoing terminals of
nected across the tip and ring springs of the trunk this trunk busy to any switch which may attempt
jack 36 in series with polarized relay I1. ‘Oper
toisei'zeit to originate a call in the opposite direc
ation of trunk relay 42 ~completes, ‘at its‘ lower tion, i. e. toward the toll oi’rlce'~ end.
contacts an obvious circuit to energize‘relay. 40, ' ' The toll operator now actuates the dial 24 to
which circuit was prepared by the operation of’ transmit the proper ‘impulse code corresponding
relay 4|, and a second obvious and parallel‘cir
to the wanted line. When the dial is moved off
cuit to operate slow acting relay ~44.
normal, the upper‘or oil-normal contacts of the
‘Relay 49 in operating completes a'locking cir . dial are opened thereby releasing relay 15 which
cuit for relay 4| which can be traced from ground, thereupon transfers the busy test lead 19 from
contacts 41 of relay 49', contacts 48 of‘ relay 38, . lead, 3| back to its normal connection to lead 8|
and contacts 49 and upper winding of relay4| to and reestablishes the short circuit around resist
battery. Relay 46 also opens its contacts 39 and ance 11 thereby removing this resistance. from the
closes contacts 59 thereby transferring the con
previously traced pulsing circuit which includes
nection of the ring conductor of the jack 36 from the dial, relay I1, pulsing relay 51 and marginal
the lower or operating winding of relay 4| to the relay 61 whereupon relay 6'! now operates which
lower winding of relay 5|, which latter relay now, in turn ‘operates relay 9| in a circuit traced from
operates. Further, relay 49 opensits lowermost battery, contact 63 of relay 54, winding of relay
contact thereby disconnecting battery from'the 9|, contact 92 of relay 61 to ground over contact
35 lower or primary winding of relay 38 and prevent‘
41 of relay 40. Relay 9| closes an obvious circuit
ing that relay from falsely operating in response to operate relay 62, which relay opens its contact
to the operation of relay 45 which immediately 93 andcloses contact 94 thereby connecting the‘
follows. When relay 44, closes its contacts it tip conductor. 85 of the trunk to the ring con
completes a circuit for relay 45 whichis slow act
ductor 96 through the pulsing contact 91 of relay
Ill) ing. After a short interval this latter relay oper
51 to the exclusion of the repeating coil 56, upper
ates and in turn operates relay 46. Relay 45 is 3 winding of polarized relay I01 and contact 99 o
made slow to operate in order to insure that relay relay 81.
40 has operated and removed battery from relay
. The return of the dial interrupts the circuit
38 before relay 45 closes its lowermost contact through relay 51 the required number of times
which otherwise would cause the premature oper- ‘ which relay releases and reoperates thereby al
ation of that relay (38) which is not desired at ternatelyopening and closing the trunk loop to
this time.
control the switching‘ circuit at the distant o?ice.
Relay 45 in operating closes, at its contact 52,’ Relay 61 also follows the interruption of the dial
an obvious circuit for operating relay ‘I I3 and at thereby alternately opening and closing the cir
.» its contact 53 closes an equally obvious circuit for
cuit previously traced for relay 9|, but this relay,
operatingrelay 54. Operation of relay ‘I I3 con
which is slow' to release, holds operated over
nects ground through resistance 55 to the right
these brief open-circuit intervals thereby holding
hand terminal of the upper winding of pulsing relay 62 operated.v Further, due to the closure
relay 5?. Operation of relay 54'closes its contact of contact 98 of relay 62, relay 9| is held operated
93 thereby connecting battery through the'lower
50 3
as long as relay’51 is released, under control of
winding of relay 5? and thence to. the left-hand relay 54.‘ When‘the dial restores to normal, relay
armature of relay 5 in the dial circuit (Fig. 1) 7 15 reoperates which again removes the short cir
which due to its slow-acting characteristic has cuit from resistance 11 thereby again increasing
not yet operated. This circuit can be traced from ' the‘ resistance of the pulsing circuit including
60 battery, contact'53 of relay 54, leads 64 and 165, . marginal relay 61 which latter relay thereupon 60
contact 93 of relay 38, winding. of 'marginal relay releases which permits relays‘ 9| and 62 to re
61, contact 68 of relay 46, lowerwinding of puls
ing relay .51, contact 59 of re1ay59, resistance 19,
lower left-hand winding of repeating coil 56, lead
84, contact 85 of relay 4 | ,' tip spring of‘ jack 36 and
tip of plug 9, contact 29 of relay I2 and lead 3|
to the left armature of relay 5. Relay 5, however,
lease in turn.
The release of relay62 ‘opens its contacts 94
and '> 98 and recloses'contact 93 thereby recon~
necting the trunk conductors 95 through the up
per right winding of repeating coil 56, upper low
resistance winding of relay I01, contact 90 of
operates almost immediately after relay 54 and -.
relay 91, and‘ lower rightwinding of repeating
the foregoing circuit may be continued over con
coil 55 to the ring conductor 96. This restores
tact 23 of relay 5, pulsing contact82 of dial24, ,3 the original condition which existed before
resistance 11,‘ winding of polarized relay I1, lead ?rst digit was dialed.
32, contact 35 of relay l2, contact l4 oi=relay l5,
When the dial is moved 011‘ normal to transmit
ring conductor of plug 9 and ring‘spring of jack ' the next'digit, the ‘same sequence of operations
35, contact 31 of relay 38, contact 59 of relay 40 to takes place, and so on, until the dial comes to
75 ground through the lower winding of relay. 5|. . rest at thesconclusion of the dialing operation at
which time the operator must release the dial key
I in order to free the dial circuit from the trunk
and condition the cord for conversation.
When dial key I is released, due to the fact that
_ relay 51 is now operated, ground at the right;
hand contact of relay 15 will be applied‘ over
contact 99'of rear dial key I00 and contacts IOI
of the front dial key I to junction point I02 be
tween resistance ‘I1 and relay I‘I thereby ground
10 ing both the tip and ring of the trunk. This
, ground is connected through relay I‘! to the ring
spring of the trunk jack and thence over contact
' 3‘! of relay 38 and contact 50 of relay 40 to the
lower winding of relay 5| thereby short-circuiting
15 it. During the pulsing period although the puls
ing circuit includes the lower winding of relay
5!, and consequently is alternately opened and
closed, this relay (5|) remains operated, i. e.,
while the dial circuit is opened, relay 5| is held
winding of'relay I‘I, lead 32, contact 30 of relay
I2, contact I4 of relay I5, contacts of the plug 9,
ring spring of jack 36, contact ‘II of relay 38,
lower left winding of repeating coil 56, resistance
‘I0, contact 69 of relay 59, lower winding of relay 5
51, contact 68 of relay 45, winding of relay 61, re
sistance I09, leads 65 and 64 and contact 63 of
relay 54 to the negative pole of battery. Opera
tion of relay‘ I‘I releases relays I8, I9 and I2.
Relay‘ I2 in releasing opens its contacts 29 and
39 thereby disconnecting the dial circuit (leads
3| and 32) from the tip and ring of the trunk,
closes its contact 34 to extend the tip of plug 9
to the upper armature of relay I5, opens contacts
I6 and closes contacts 35 thereby connecting bat
tery through the cord sleeve relay 33 to the sleeve
of plug 9 and consequently to the sleeve of the
trunk thereby holding the trunk sleeve relay 42
operated which otherwise would also release.
20 ‘operated by its upper winding in a circuit traced I Cord'sleeve relay 33 now operates in series with 20
from battery, contact 63 of relay 54, lead 64, re v.the trunk sleeve relay 42 thereby operating relay
sistance. I03, upper winding and contacts I04 of I5. Relay I5 closes through the tip and ring
relay 5| and contact 89 of relay 54 to ground.
of the cord.
When the dial circuit is. closed, thereby operat
‘i5 and release of relay I9 releases relays 2| and
25. ing relay 51, the holding winding of relay 5| is
short-circuited in the following path: Ground,
contact 86 of relay 51, contact I05 and the upper
winding of relay 5|, contact I04 of this relay and
contact 89 of relay 54 back to ground.
Ground connected at the junction point I02,
by the release of dial key I, is also connected
through resistance 11, contact 82 of the dial and
contact'23 of relay 5, to lead 3| and thence over
the previously traced pulsing circuit including the
35 lower winding of relay 5‘! and marginal relay G‘I
to battery. As before mentioned, resistance: 11 is
su?iciently high to prevent the operation of relay
51, but relay 51, however, holds operated in this
' The short-circuiting ofrelay 5| and its conse
quent release at this time completes a circuitto
operate relay 38 which cain be traced from ground
at- the still closed contacts 86 of relay 5?, con
. tacts I06 of relay 5|, now released, upper con
45 tacts of relay H3 and upper winding of relay
Release of relay I8 releases relay
5 thereby restoring the position dial'circuit (Fig.
l) to normal.
With relay I2 released and relay I5 operated
the tip and ring conductors of the cord are
connected through and the‘ supervisory bridge,
comprising retard coil IIO,and relay II I 'in par-_
allel across the cord, holds relay 5'! operated.
Relay III operates at this time and lights super
visory lamp II2.
.When the called subscriber answers battery
and ground are reversed in the usual manner, over 35
the trunk from the community dial of?ce, causing
operation of polarized relay I0‘! in the trunk.
Operation of relay I01 closes a circuit to operate
relay 59 which can be traced over the lower con
tacts of‘relay 81 and lowermost normal contacts I
of relay 40 to battery. Operation‘ of relay 59
opens its contacts 58 and 59 thereby disconnect
ing the two windings of relay 5‘I from the previ
' ously traced circuit through the cordwhich has
held this relay operated and at its ‘upper and
lower front contacts substitutes a local holding
circuit for relay 51. This, however, opens the cir
cuit for supervisory relay III in the cord which
38 to battery. Operation of relay 38 closes its
contacts ‘I2 and ‘II thereby connecting the tip.
and ring springs of the jack 36 to the respective
terminals of the left-hand windings of repeating
50 coil 55. Operation of this relay also opens its
contact 48 thereby opening the locking circuit for
releases and extinguishes the supervisory lamp
relay 4| which thereupon releases which in turn
opens the circuit for relay 40‘which also releases.
Release of relay 4| opens its contact 85 which up
55 to this time has connected. the tip spring of the
jack 36 to the lower left-hand terminal of re
in turn thereby reconnecting the winding of relay
51 to the cord and reoperating supervisory relay
III which lights supervisory lamp IIZ. The toll
operator then challenges on the line and- ?nding
peating coil 55 which extends to battery through
relays 01 and 57.
Relay 38 in operatingalso'closes its contact I08
60 thereby maintaining‘ a connection between the
sleeve of jack 35 and relay 42 and holding this
relay operated, which otherwise would have re
leased due to the release of, relay 4|.
Further, operation of relay 38 opens its contact
83, thereby removing the short circuit heretofore
connected around resistance I09. The effect of ~
the closure of contacts ‘I2 and H and opening of
' contact 83 of relay 38 and the opening of contact
I I2.
When the conversation is ended and the called
subscriber disconnects, relays I0‘I and 59 release
the conversation ?nished removes plug 9 from
jack 36 whereupon the trunk circuit restores to
normaLwhich operation, as it forms no part of
the invention, ‘will not be described in detail.
What is claimed is:
1. In a telephone system, a trunk circuit, an
operator’s cord circuit adapted to be connected
to said trunk, a dial adapted to be connected and
locked to said cord circuit, a dial key, a polarized
relay adapted to be connected inseries with said
dial when the dial is connected to the cord, means
responsive to the joint connection'of said cord
circuit to said trunk and operation of’ saiddial key
35 of relay 4| is to reverse and reduce the current
70 ?owing back into the dial circuit through a to connect said dial to said cord andlock it under
polarized relay [1 and due to this reversal of cur- ' control of saidpolarized relay, a source of direct
rent, relay I‘I now operates.
current adapted to be connected to said trunk re
Thereversed circuit for operating relay I“! can sponsive to the connection of said dial and in a,
be traced from ground,. right-hand contact of non-operate direction with respect to saidpolar
75 relay ‘I5, contacts 99 and IM of keys I00'an-d I, ' ized relay, and means responsive to therelease
of said dial key to cause said current source to be
reversed in polarity with respect to said trunk to
operate said polarized relay and release said dial
from the cord.
I 2. In a telephone system, an operator’s cord
circuit, a trunk circuit,‘ a dial, a dial key, means
responsive to operation of said dial key and cone
nection of said cord to‘the trunk to 'connectand
lock the dial to the cord, a polarized relay in
nected and locked to any of said cord circuits
jointly responsive to connection of the cord to
any one of said trunk circuits and the operation
of the key, polarized relay means at said manual
exchange in series with said dial when it is con
nected to a cordadapted when operated to dis
connect said dial from its connected cord circuit,
means at certain of said automatic exchanges re
sponsive to seizure of the called line thereat to
10 series with the dial controlling the locking circuit , reverse thec'onnection of the exchange battery 10
of said dial, a source of direct current, and means
responsive to release of said dial key to connect
said source to the trunk in such a polar direction
as to operate said polarized relay to disconnect
15 the dial from the cord.‘ ,
3. In a telephone system, a manual exchange,
a plurality of automatic exchanges, trunk cir
cuits from said manual exchange to each of said
automatic exchanges, cord circuits at said manual ‘
exchange for making connection to said trunk
circuits, a position circuit including an impulse
transmitting device and a key at the manual
exchange, said device being adapted to be con
to the calling trunk circuit to operate said polar
ized relay means at the manual exchange, and
means-associated with said position circuit, cord
circuits, and trunk circuits extending to automatic
exchanges not arranged to reverse battery to the 15
trunk when the called line is seized,vresponsive
to release of the dial key, to cause direct current
to be connected to the trunk circuit at the manual
exchange in such a direction, as to operate said
polarized relay means to release the dial from its
associated cord circuit.
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