US1667385A - Automatic telephone system - Google Patents

Description

April 24, 1928. 1,667,385

E. E. JONES AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 9, 1921 3 Sheets-Sheet 1 Eui-wm EJ021515 6% z. w-

r 3 Sheets-Sheet 2 E. E. JONES AUTOMATIC -TELEPHONE SYSTEM Gngmal Flled Feb 9 1921 ii 11 I April 24, 1928.

April 24, 1928. 1 1,667,385

E. E. JON E 5 AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. '9, 1921 3 Sheets-Sheet 3 -1iwan Ur 137mm E. June 565%. W

Patented Apr. 24, 1928.

EDWIN E. J'OLNES, OF CHICAGO, ILLINOIS,

Assienon, {BY MEsNn ASSIGNMENTS, mo

AUTOMATIC ELECTRIC INCL, OF CHICAGO, ILLINOIS, zAHCQRPOR'ATION OF DELA- WARE.

' AUTOMATIC TELEPHONE SYSTEM Application fil ed February 9, 1921;Serial No; 443,654. Renewed June 15, 1927.

The ,present invention relatesto automatic telephone s stems but is concerned more particularly with small systems which are conif monly known as private automatic eX-' feature of this character which is commonly known as conference calling. "This is an arrangement to enable an official of a com pany having a private automatic exchange to talk to a number of his employees simultaneously; in other words a number oftelephone lines may be connected together for conference purposes. Hitherto in arrangements of this character it has been necessary to maintain in use trunk lines and switches for each telephone line during the conference. This invention contemplates a scheme of thisnature wherein the trunlnlines and switches used during a conferenceare reduced to a minimum. v

The particular manner in which this and other results are accomplished will be explained fully hereinafter, reference being had tothe accompanying drawings; Refer ring now to the accompanying drawings comprising Figs. 1 to 3, in order for thedrawings to be understood best, Fig. 1 should be placed over Fig. 2, andi-Fig. 3 should be placed under Fig. 2.

Referring first to 7 shown two substations of the usual automatic type,.each having a rotary line switch of wellknown construction indi'vidual'thereto. These line, switches are indicated by reference characters (land 0, and in com mon with a plurality of other line switches have access to trunk lines leading to connector switches, one of which is shownat D, Fig.2. This connector is of the usual Strowger vertical and rotary type and has the usual set of contacts arranged in ten rows or levels. 011 the first eight levels the switch D andother local switches have the functions ofordinary connectors except in one instance which exception is on the conference number. On thetenth level the switch D operates as an ordinary selector switch. On the ninth level in addition to Fig. 1,}at A and A are a short distance apart in a city served'by a public manual exchange. Ojne of these fac tories is supplied with telephone service by l the private automatic exchange under disk cussion while the other l'factory is supplied wlth telephone service another; private" automatic exchange of the-same type. Thetenth level in the private automatic exchange in factory No. l is reserved for trunk lines leading to the private automatic exchange, 1 1n factory No. 2, while the ninthlevelris used."

for trunk lines extending to the public mane ual exchange. i

From the above description the fwiring ioo of the banks of the connector -D. will be readily understood, 'Bank contacts 18814 O, inclusive, are, the terminals of conductors leading to the local substation A, while-the bank contacts l421 l4, inclusive, are terminals of a line leadingtosubstation A. Bank, contacts 134 136, tinclusive, reliiresentv the,

g8!) conference,numberwhich it wlll be assumed is the number 60. The conductorsleading from this-set of banlrcontacts terminate an auxiliary connector switch Fig. Bank contacts 130-132, inclusive, are ter manual exchange, while contacts 125-127,.inelusive, are terminals of a'trunk line "extending to the private automatic exchange at factory No. 2. All the sets ofcontacts above described are multiplied in the usual man 90 minals of a trunl: lineleading tothe public;

nor into all localconnector switches similar to the switch D. The switch H is used only for conference purposes andis an ordinary v 1100 mg access to local snbscrlbers llnes only and well known Strowgerconnector hav- Tlie bank contacts in the connector switch H in which the local subscribers lines terminate are joined to the multiple between the local con1iectors, but before .bei-ngso joinedv one line conductor of each subscriber who is entitled. to conference service is passed throughthe winding of a ser1es:r elay,these being represented in the drawings at 320 and 327, which are the relays individual to the lines leading to substations A and A, respectively.

Having briefly described the apparatus in the system, a detailed explanation of its operation will now be given. For this purpose it will be assumed that the subscriber at substation A desires to hold a conference. Under these conditions this subscriber will remove his receiver and call the regular local number of the first subscriber desired in the conference, prefixing the digits of the conference number 60. l v hen the receiver is removed at substation A a circuit is closed for the line relay 13 of the line switch C over the line conductors 11 and 12 in series. Upon operating, relay 13 at its armature 2O closes a circuit which includes the switching relay 14: and the stepping magnet 15 in series, and at its armature 21 connects the test wiper 26 to the above circuit at a point midway between the switching relay and the said stepping magnet. The operation now depends upon whether the trunk line with which the .wipers of the line switch C are associated is or is not busy. If the trunk line is busy the test contact with which the test wiper 26 is in engagement will be grounded, and as a result the switching relay 1 1 will be short circuited and the stepping magnet 15, being supplied with direct ground by way of the said test wiper, will operate as a buzzer to advance the switch wipers step by step in search of an idle trunk line. It will be assumed, however, that when the call is initiated the wipers of the line switch C are standing upon the bank contacts shown in the drawings, and it will be further assumed that the trunk line extending from these contacts is idle. Under these circumstances the test contact 29 will have no ground potential on it and when the receiver is removed the energization of the line relay 13 is followed immediately by the energization of the'switching relay 14. It may be stated at this point that the switching relay is of very high resistance so as to prevent the operation of thestepping magnet 15 at this time. As a result of the energization of the switching relay 14, the line conductors 11 and 12 are disconnected from the line relay 13 and from ground, respectively, and are extended by way of armatures 16 and 1S and their front contacts, wipers 25 and 27, bank contacts 28 and 30, trunk conductors 38 and 10, armatures 75 and 7 8 and their back contacts, to the upper and lower windings of the double wound line relay 50 of the local connector 1).

When the calling line is extended to the switch D as above described the line relay 50 enargizes over the line circuit and completes a circuit for the slow acting release relay 51. Upon energizing, relay 51 prepares the operating circuits of the connector D at its armature 66, and at armature 67 establishes a holding circuit which extends from ground G front contact and armature 67, release trunk conductor 89, armature 17 and its front contact, and through the winding of the switching relay 1 1 andthe stepping magnet 15 to battery. The above circuit is completed before the slow acting line relay 13 has had time to deenergize and serves to maintain the switching relay 14 energized throughout the connection. Ground is also extended by way of the private normal conductor 31 to multiply connected test contacts in the from intrusion in the ordinary manner.

The calling subscriber may now operate his calling device in accordance with the first digit. of the conference number, or the digit 6. Six'interruptions are thereby pro duced in tl e line circuit of relay 50 which deenergizes a corresponding number of times, each time completing a circuit extend ing from ground G, armature and its back contact, armature 66 and its front contact, off normal springs 69and 68, through the winding of the slow acting series relay 52 and the winding of the vertical magnet 100 to battery. The above is the circuit over which the first impulse is transmitted. At the first upward movementof the shaft the off normal springs are shifted and the circuit for the vertical magnet is completed over a new path which is the same as the one previously tracedexcept that it includes the oil normal springs 69 and 77, and armature and its front contact, slow acting relay 52 being now' in an operated position. By the operation of the vertical magnet 100 the switch wipers 120122, inclusive, are raised step by step untilthey are )lZICGd opposite the sixth level of bank contacts. The slow acting series relay '52, which is energized in series with the vertical magnet, maintains its armature attracted throughout. the vertical movement of the switch and at the end of the vertical operation deenergizes transferring the operating circuit to the rotary magnet- 102.

The calling subscriber may now operate hiscalling device in accordance with the second digit of the conference number namely, the digit 0. Ten interruptions are thereby produced in the circuit of the'line relay 50 which operates in response thereto and at each retraction of its armature completes a circuit extending as follows: Ground G, armature 65 and its back contact, arn'iature 66 and its front contact, off normal springs 69 and 77, armature 70 and its back contact, normally closed springs controlled by relay 57, armature 99 and its back contact, and thence through the winding of the rotary magnet 102 to battery. Magnet 102 operates to rotate the wipers 120-122, inclusive, into engagement with the'tenth set of con banks of the connector switches, whereby the said line is'protected tacts'in the sixthflevel which, it will be assumed, are the bankcontacts 131136, in- ClHSIVG. The-slowacting relay 58 is ener gi'z ed in multiple'with the rotary magnet and-operates to connect the test wiper 4121' Whenthe springs 83and8ei are brought into engagement a circuit iscompleted extending from ground'on release itrunk conductor 39 by way of armature 96 and its back contact,

th'roughsprings ea andSS, and through npperwinding of relay 56 to battery. Relay 56 operates-to establish a locking circuit for itselfat its armature Bland at armatures 80 and "82 prepares a :point in the dialling oircuit of the auxiliary connector H. If the line is busy the operation of. the springs 83 and 84; will have no function at this time ex cept as above stated. Supposing this to be the case ground will be present on the test contact 135 engaged by the test wiper 121. A circuit will thereby be completed extend ing from the said groundedtest contact by way of test wiper 121, normally closed springs controlled by relay 59, armature 9O 3 and its front contact, back'contact and, armature .93, and thence through the winding of the test relay 57 to battery. Upon oper- .ating, the relay 57 establishes a locking circuit for itselfat armature 85, opens the rotary rnagnet circuit by the operation of armature 86, and at armature 87 places the busy tone upon the lower line conductor, of the calling subscriber thereby notifying him that, for the present the conference number is inaccessible. The calling subscriber will therefore replace his receiver upon the switchhook, thereby releasing the switches C and D in a manner to be explained here-- inafter.

l Iowever, it will be assumed in the present-case that the conference number was idle when connection thereto was attempted. Under these circumstances no ground will be-present on the test contact 135 and test relay 57 will not be energized. A circuit is then completed upon'the deenergization of the slow acting relay 58, extending from ground on release trunk conductor 89, ar-

mature 85 and its back contact, through the energizes over this circuit, and establishes a locking circuit for itselfat armature 9'7 and at armatures 95and 1L0 prepares another point in the dialling circuit to the auxiliary connector H4 Uponenergizing, relay 59 at armature 96 also removes :t-he ishort circuit around the relay 55$ A circuit is thencifective 1 extending from ground on FlElGflSG trunk conductor 89, through the winding of relay 55,-camsprings 84: and 83, and throughthe upper winding ofrelay 56 to battery. iitelay 55, upon energizing, completes the dialling circuit to the auxiliary connector H. This circuit includes the lll16:l'6l2iyf250 which is energized over a circuit extending from ground G through the lower winding iof relay 250, conductor 156, bank contact 134, wiper 120,:front contactaud armature 95, through the winding oflow resistanceseries relay 58, front contact and arn'iature 7:5, thence overthe line conductor B8 of the substation A, through the transmitter-landre.- ceiver of the said substation, line conductor 40, armature T8 and its front contact, front contact and armature 82, armature 110 and its front contact, wiper .122, bank contact, 136, conductor 158,'through the upperwind ring of the line relay 1 5.0 to battery.- -,,Y-Relays 53 and250 energize over this circuit. f-Re-' lay 53 at lts armature 76 H1al11t21l]1S"1tlle C1P- cuit ofthe slow acting releasere'lay .51 of thelocal connector D in an operated lJOSl-r tion thereby preventing the release of the switch D and maintaining thelineswitchG in an operated position; Relay 250, upon energizing,completes thecircuit of-the slow acting release relay 252 of the auxiliary connector H. c i i i i The calling subscriber at substation A may now call the remaining two digits ofthe desired local subscribers number. When the calling device is operated for the firstdigit of the subscribers number a series of interruptionsfi-s produced in the line circuit of the linerelay 250 of theconnector H. Bee. lay 250 operates in responsetheretoand sends a corresponding series of impulses-over. a circuit extending fromground G, by Way of armature 265 and its back contact, arma ture 269 and its front contact, ofi normal. springs 272 andf270, through the winding of the slowacting relay 253 and-through the vertical inagnet QGO to battery, The above is the circuitover which the first impulse is transmitted. Upon the'first vertical step of the shaft the oft normal springs are shifted and the remaining impulses to the vertical magnet are sent over a different ci.rcuit which is the same as theone previously traced except that itincludes the off normal springs 27 2 and 27 3 and armature 275 and' its front, contact, relay 253 being now in an operated position. The magnet 260 op erates to raise the wipers 290-292, inclusive, step by'step until they standflopposite the level of bankcontacts in whichcthe desired subscribers line is located. I The slow acting v relay 253 is energized'in serieswith-the yertical magnet 260,,maintains its armature at tracted throughout the vertical operation of Ground G", armature 265 and its back contact, armature 269 and its front contact, off normal springs 272 and 278, armature 275 and its back contact, back contact and armature 283, armature 288 and its back contact, and thence through the winding of the rotary magnet 261 to battery. Magnet 261 op erates to rotate the switch wipers 290-292, inclusive, into engagement with the set of bank contacts associated with the line of the desired subscriber, which it will be assumed are bank contacts 298300, inclusive, in'which the line of the subscriber at substation A is terminated. The slow acting relay 256 is energized in multiple with the rotary magnet and operates to connect the test wiper 291 to the test relay The further operation of the connector 'H depends upon whether or not the line of the desired subscriber is or is not busy. if busy at this time, a ground potential will be present on the test contact 299. A circuit is thereby completed extending from. the said grounded test contact by way of the test wiper 291, armature 284C and its front contact, and through the winding of the test relay 255 to battery. Upon energizing, re

lay 255 establishes a locking circuit for itself at armature 282 and at armature 281 connects the busy tone to the line of the subscriber at substation A. Upon hearing this tone the calling subscriber will know that the line he desires is busy and he will replace his receiver upon theswitchhook, thereby releasing the switches in a manner which will be described fully hereinafter.

Let us assume now that the line of the subscriber at substation A was idle when connection thereto was attempted. Under these circumstances there will be no ground potential present on the test contact 299 engaged by the test wiper 291. A circuit is thereupon completed following the deenergization of the slow acting relay 256 which extends from ground on release trunk conductor 263 by way of armature 282 and its back contact, upper winding of the switching relay 257, back contact and armature 28 1,'test wiper 291, bank contact 299, con ductor 151, conductor 35, through the winding of the switching relay 32 of the line switch C and through the winding of the stepping magnet 83 to battery. Relays 257 and 32 operate over this circuit. Due to a mechanical interlocking device controlled by the armature of the line relay 31, the switching relay 32 is only operated enough to clear the line of the substation A from its normal battery and ground connections in the line switch G. Relay 257, upon operating, establishes a locking circuit for, itself at its armature 287, opens the rotary magnet circuit at armature 288, and at armatures 285 and 289 completes the ringing circuit. Ringing current will flow over a circuit extending from the generator V, back contact and armature 280, armature 289 and its front contact, Wiper 292, bank contact 300, through the winding of relay 327, and the condenser associated therewith in multiple, conductor 152, conductor 36, switchhook springs, ringer and condenser of the substation A, conductor 34,,conductor 150, bank contact 298, wiper 290, front contact and armature 285, armature 278 and its back contact, and thence through the upper winding of the ring cut-0E relay 254: to battery. Ringing current is intermittently applied to the above traced ringing circuit until the subscriber at substation A removes his receiver from the switchhook. The relays 827 and 25s are so constructed that they do not respond to alternating current and hence will not operate over the ringing circuit.

When the subscriber at substation A re moves his receiver a path for direct current is provided over the line circuit thereby energizing the relays 327 and 254. Relay 25 i upon energizing, establishes a locking circuit for itself at armature 279 and at and 336 and their front contacts to extend the line of the subscriber at substation A into connection with the conference holding trunkcomprising conductors 340 and 341. The calling subscriber at substation A will inform the subscriber at substation A that a conference is to be held. It will be noticed that while relay 327 is included in the line circuit between the two subscribrs its inclusion will have no effect on the transmission of voice currents because a path for talking current is provided by the condenser associated with relay The calling subscriber will then hang up his receiver thereby openings the line circuit of relay 250 and also the circuit of the series relay 53. Both these relays deenergize thereby opening the circuit of the slow acting release relays 51 and 252 in their respective switches, relay 51 upon deenergizing, completing the release magnet circuitof the connector D at the sainetime removing ground from the holding circuit of the line switch C and relay 2" 2 upon defrom intrusion in the ordinary manner and over the following circuit: Ground through the lower winding of thecommon talking impedance 325, front contact and armature 336 through the winding of relay 327 and i over the line conductors of the called substation, armature 333 and its frontcontact,

, and through the upper winding of the impedance 325 to battery. At armature 337, relay 327 also maintains ground on private normal conductor 151 of the substation A thereby protecting the line of the subscriber at the same timemaintaining the switching relay 32of the line switch C in its operated position. V

The "calling subscribed at substation A will now remove his receiver and, in identically the same manner as above described, call another local branch exchange subscriber by means of a local connector and the auxiliary connector H. This operation will now be briefly described. WVhen the-receiver is removed at substation A the line switch G operates as before described to se- 1 lcctan idle trunk terminating in a local connector which it will be assumed is the connector D. v V p When the callingdevice at substation A is operated for the digits of the conference number 60 the line relay controlsthe operation of the vertical magnet 100 in stepping the switch wipers 120122, inclusive, opposite the sixth level of bank contacts. hen the last digit of the conference number isdialled the line relay 5O responds to the interruptions in its line circuit and con trols the operation of the rotary magnet 102 i in rotating the switch wipers into engagement with the conference number. When this occurs relays 56, 59 and 55 "again enerto complete the circuit of the line relay 250 of the auxiliary connector I-l.

The calling sijib'scriber may now operate his calling device in accordance with the first digit of the next local subscribers number. The line relay 250 operates, sending a corresponding series of impulses to the vertical magnet 260 in series with'the-slow act'- relay 253 in the same manner ;'as previously described. Magnet 260 operates to raise the wipers290-292, inclusive, step by stop, until they are placed opposite the level of bank contacts in which th'enext local subline is located. The slow acting re rgized in serieswith the res:

tical magnet and maintains its armature attracted throughout the vertical operation of theswitclr and atthe termination of the verti a1 movement deener-giz es, thereby transferring theoperating circuit to the rotary, magnet 261. 3

hen the last digit of the local subscribers number is called the rotaryma-gnet 26-1 under the control of the line relay 250 operates to rotate the switch wipers into en; gagen'ient witlrthe set of -ba'nlr contacts in which the desired subscribers line is tere initiated. 'If this line is busy the connector H will operate in the usual manner to give the busy tone to the calling subscriber. If the line is idle the switching relay 257 will energize and complete the ringing circuit, Ringing current is then intermittently projected over the line circuit of this subscriber in identically the same manner as va -sidescribed in the connection with the subscriber at substation A.

lVhen this called subscriber answers the ring out off relay 25s and the relay silnilarto relay 327 in series with the line circuit: will be energized, relay 25etestablishing a locking circuit for itself and completing the; talking connection, the relay similar to 327 bein operated to transfer the line of the called subscriber onto the conference holding trunk. After informing this called subscriber that a conference is to be held the calling subscriber will replace his receiver upon the switchhool; thereby initiating the release of subscribers in the conference, for "the reason that he has now beenplaced in telephonic coi'rnection' with the conference holding trunk comprising conductors 3 10 and 3&1 by means of the energization of the series relay similar to 327 in the line of the subscriber last called. it

. When the conferenceis terminated each subscriber by placing his receiver upon the switchhookj severs his connection with the conference holding trunk, the relays 32.0,

327 and similar relays being deenergized' upon theassociated called subscribers replac ing their receivers upon the switchhook. hen the calling subscriber replaces his receiver upon the switchhook he will release the operated switches C, D, andIIin manner before described.

Having described the'process of up conference ,the' manner in which a local' connection is coinplete d wil l sown-e sciibedi For this purpose as sinned that the subscriber at substation A de sires to call the subscriber at substation A. hen the receiver is removed at'substation A the line switch C operates in the'usnal manner to select an idle trunk terminating in a local connector switch which it will be assumed is the connector D. The line relay of the connector D will be energized over the line circuit completing the circuit of the slow acting release relay 51. Relay 51 energizes preparing the operating circuits of the switch D at armature 66 and at armature 67 establishing a holding circuit for the line switch C.

l/Vhen the calling device'at substation A is operated for the first digit of the desired number of the line relay 50 responds to the interruptions in its line circuit and at each retraction of its armature completes a circuit extending from ground G by way of armature 65 and its bacl: contact, armature 66 and its front contact. off normal springs 69 and 68, through the winding of the series relay 52, and the winding of the vertical magnet 100 to battery. Upon the first step of the switch the otl' normal springs are shifted and the impulses are sent to the vertical magnet over a different circuit which includes the elf normal springs 69 and 7? and armature 0 and its front contact relay 52 being now in an operated position. Magnet 100 operates to raise the wipers 120 122, inclusive, step by step until they are placed opposite the level of bank contacts in which is located the line of the desired subscriber. The slow acting series relay 52 is energized in series with the vertical magnet and re mains so throughout the vertical operation of the switch. At the termination of the vertical movement the slow acting relay 52 deenergizes and transfers the operating circuit to the rotary magnet 102.

lVhen the'callinp; device at substation A is operated in accordance with the last digit of the subscribers number another series of interruptions is produced in the circuit of relay 50. Relay 50 operating in response thereto sends a series of impulses to the rotary magnet 102 in multiple with the slow acting relay 5S. Magnet 102 operates to rotate the switch wipers into engagement with the set of contacts in which are terminated the conductors of the desired subscribers line and which, we will assume, are the bank con tacts 1&2 14 1, inclusive. As before, relay 58 being energized in multiple with the rotary magnet 102 operates to connect the test wiper 121 to the test relay 5?. 1f the line of the subscriber at substation A should happen to be busy at this time a ground potential will be present on the test contact 1 13.

Supposing this to be the case, acircuit is then completed extending from the said grounded test contact by way of the test wiper 121, normally closed springs controlled by relay 59, armature 90 and its front contact, back contact and armature 93, and through the winding of the test relay 57 to battery. Upon operating, relay 57 establishes a locking circuit for itself at armature 85 and at armature 87 places the busy tone on the calling subscribers line. The calling subscriber upon hearing this tone will know that the line is busy and will replace his receiver thereby causing the release of the connector D and the line switch 0 in the usual manner.

It will, however, be assumed that the line of the subscriber at substation A was idle when connection thereto was attempted. Under these circumstances there will be no ground present on test contact 1&3. A circuit isthen completed upon the deenergization of the slow acting relay 58 extending from ground on release trunk conductor 39, armature 85 and its back contact, through the lower winding of the switching relay 59, back contact and armature 90, normally closed springs controlled by relay 59, test wiper 121, test contact 143, conductor 151. conductor 35, and through the winding of the switching relay 32 and the stepping magnet 38 to battery. Relays 32and 59 operate over this circuit, relay 32 operating, as before, to disconnect the line of the subscriber at substation A from its normal battery and ground connections in the line switch C. Relay 59 upon operating, establishes a locking circuit for itself at armature 97 places ground on the private nor mal conductor 151 at armature 98 and at armatures 95 and 110 completes the ringing circuit. Ringing current is then intermittently applied to the line of the substation A until the subscriber thereat responds by removing his receiver from the switchhoolr. lVhen this occurs the ring cut oil relay 56 energizes establishing a locking circuit-for itself at armature 81 and at armatures 80 and 82 opening'the ringing circuit, and at the front contacts of these armatnres completing the talking connection. Couriers-a tion may now be carried on between the subscribers at substations A and A battery being supplied to the calling subscriber from the winding of the line relay 50 and to the called. subscriber from the windings oi the back bridge relay 54L Vhen the COIIYQISttion is terminated both subscribers will replace their receivers upon the switchhoolt, the replacement of the receiver at the calling substation A initiating the release of the line switch C and connector D as previously described,

Having described the process of setting up a local connection, the manner in which a trunk connection to the public manual exchange is completed will now be explained, after which a description will be given of the process of establishing a trunk connection to a" subscriber in "the other private automatic exchange which'is located at factory No. 2. p

As before stated the trunk lines extending to the main exchange terminate in the ninth level; It follows therefore, that in order to connect with one of these trunk lines the digit 9 must be called. The subscriber. atsu'bstation A who desires to connect with the main exchange willtherefore remove his receiver and operate his callingdevice in accordance with the digit 9 When the receiver is removed the line switch 6 operates as before described to extend the associated line to a trunk line terminating in an idle local connector switch.

ssumin iavtre on1ec Y 'isi -A ,tl tl c 1 toiD dle and is selected for use. When connection is extended thereto the line and release relays 50 with the same results.

be accomplished by any suitable cam arrangement'. A convenient way is to mount the spring assembly comprising springs 105-108,. inclusive, just above the top of the shaft so that spring 106 will be operated by the cup spring casing mounted at the upper extremity of the switch shaft. switch isoperated opposite the ninth level the spring 106 willbe operated and when the switch shaft. is raised opposite the tenth level both springs 106 and 108 will be actuated;

To proceed, thejslow actingseries 1"elay 52is energized during the vertical operat on 01' the switch and for an instant there 'when the ninth and tenth level sha'tt springs 105 and 106 are closed on the ninth vertical stcpra circuit is completed extending as follows: Groundon release trunk conductor 39. by way of shaft controlled springs 105 and 106, springs 109, armature 73 and its front contact, back contact and armature 93, and through the winding. of the test relay 57 to battery. Upon energizing, relay 5'5. establishes alockingcircuit for itself at armature and at armature 86"prepares the rotary I magnet circuit. At the termination of the vertical movement of the shaft the slow acting relay52 deenergizesan d a circuit is thereby completed extending from ground on release trunk conductor 39 by way of shaft controlled springs 105 and 106, springs 109, armature 73 and its back contact, armature 86 and its front contacnarmat'ure 99 and its back contact, and through the winding of l Vhen the atter and,

the rotary magnet 102 to battery. Relay 58 is energized in multiple with the above circult ,of the rotary magnet: 'Ma-gnet' 1020perates to rotate the switch wipers 120122, I

on whether or not thetrunk line with which 7 the switch wipers are in engagement is or is not busy. If busy, a ground potential will be present on the test, contact engaged by the wiper 121'; A circuit is thereby com pleted extending from the said grounded test contact by way of test wiper 121, normally closed springs controlled by relay 59,

armature 90 and its front contact, backcon- 1 tact and armature 93, and'thr'o'ugh thewindingot the test relay 57 to battery. Relay 57 energizes and again completes the rotary magnet circuit. Relay 57' and 1nagneti102 will operate alternately" until an idle trunk line is found which, we will assume, is the trunk line terminating in, bank contacts 130132, inclusive. lVhen the switch wipers are rotated into engagement with this set of bank contacts no ground will be present on test contact131. Then upon the deenergization of the slow acting'relay 58 a c rcuit is completed extending from groundon release trunkconductor-39, armature 85 and its back contact, lower winding of the switching relay 59, had; contact and armature 90, normally closedsprings controlled 'by relay 59,

. test; wiper 121, test contact 131, through resistance R to battery. Relay 59" energized over this circuit and establishes a locking circuitefor itself at armature Wand at armatur'es 95 and1'10 completes a ringiugcircuit. Ringing current is then automatically pro jected out over the trunk line the sameas in the case of the called local line and the ring downdrop or other signalling .device at the manual switchboard in the public exchange is operated in .t'heusual manner. lVhen the operator plugs in to answerthecall the ring cut oil relay 56 is operated, disconnects the ringing currentand completes the talking connection. local station in the main exchange may he completed by the operator through the medium of any suitable means which need not be explained herein.

The operation of the local connector I) when usedfor trunking to the second private automatic exchange is-thc same as in thecase just described'in so far as the selection-of an 1dle trunk 18 concerned, but since theconnecv tion in the private automatic exchange must be controlled automatically the circuits of the switch D are altered suitably in order'to permitthe switch to operate as a series repeater' for the purpose of repeating impulses loo The connection to the desired over the selected trunk line extending tothe private automatic exchange at factory No. 2. The operation which takes place when connection is extended to the second private automatic exchange will now be briefly explained.

Since the trunk lines extending to the pri vate automatic exchange at factory No. 2 terminate in the tenth level the digit to be called is the digit 0. Assuming that a subscriber at substation A desires to call a party in the second private automatic exchange, when the receiver is removed the line switch G operates to extend the line of the calling subscriber to an idle connector D. V iVhen the calling device is operated for the digit 0, ten interruptions are produced in the line circuit of the relay 50 which deenergizes a corresponding number of times whereby controlling the vertical magnet 100 in raising the switch wipers 120122, inclusive, step by step until they are placed opposite the tenth level. Upon the tenth vertical step of the switch the springs 105 and 106. and 107 and 108 are shifted into engagemen As before, the slow acting relay 52 is energized in series with the vertical magnet and maintains its armature attracted throughout the vertical movement of the switch and for an instant thereafter. When the springs 105 and 106 are brought into engagement a circuit is thereby completed for the test relay 57 which energizes establishing a locking circuit for itself at armature 85 and preparing the rotary magnet circuit at armature 86. Upon the termination of the vertical movement of the switch relay 52 deenergizes. A circuit is then completed for the rotary mag net 102 in multiple with the slow acting relay 58. Magnet 102 operates to rotate the wipers 120122, inclusive, into engagement with the first set of contacts in the tenth level and to also break the locking circuit of relay 57. the operation of springs 107 and 108 a circuit is completed extending from ground on release trunk conductor 39, armature 06 and its'back contact, shaft controlled springs 107 and 1.08, and through the upper winding of the ring out oft relay 56 to battery. Relay. 56 operates as before, establishing a locking circuit for itself at its armature 81, and at armatures and 82 preparing a point in the repeating circuit. If the trunk line with which the switch wipers are associated is busy ground'willbe present on the test contact thereof and the relay 5'? will be again energized to complete the rotary magnet circuit. The alternate operation of relay 57 and magnet 102 will continue until an idle trunk line is found which, we will assume, is the trunk line terminating in the bank contacts 125-127, inclusive. W hen the switch wipers are rotated into engagement with this set of contacts ground will not be present on the test contact 126 and a circuit is completed extending from ground on release trunk conductor 39 by way of armature 85 and its back contact, lower winding of relay 59, back contact and armature 90, normally closed springs controlled by relay 59, test wiper 121, test contact 181, and thence through re sistance R to battery. Relay 59 upon operating, establishes a locking circuit for itself at armature 97, at armatures and 110 prepares another point in the repeating circuit, and at armatures 9-6 removes short circuit from relay 55. A circuit is then eifective extending from ground on release trunk conductor through the winding of relay 55, shaft controlled springs 107 and 108, and through the upper winding of the.

ring cut off relay 56 to battery. Upon operating, relay 53 completes the repeating circuit in the same manner as was described when the switch D was operated to seize the auxiliary connector H on the conference number. Relay 53 is energized in series with this repeating circuit and operates as before to maintain the slow acting relay 51 in an operated position as long as the calling subscriber atsubstation A maintains his receiver off the switch-hook. It will be seen that the subscriber at substation A by op erating his calling device will produce a.

series of in erruptions in the line relay circuit of the incoming switch in the private automatic exchange at their factory No. 2, and the connection is thereby completed to the subscriber in private automatic exchange No. 2, in the usual manner. It will also be seen that only a two conductor trunk' is necessary between the two private automatic exchanges for the reason that the series relay 53 in the connector D maintains the switches C and D in their operated position.

In case a call is attempted by way of either the ninth or the tenth level of the connector D and all the trunks in the called level are busy, the trunk selecting operation of the switch D continues until the wipers 120422, inclusive, are rotated out of engagement with the last set of bank contacts.

This occurs upon the eleventh rotary step 1 and, at'this time, a cam on the switch shaft shifts spring 109 out of engagement with its lower contact and into engagement with its upper contact, thereby opening the circuit of the rotary magnet and closing a circuit to maintain busy relay 57 energized so as to give the usual busy signal to the calling subscriber.

Having described the invention what is considered to be new and desired to have protected by Letters Patent will be pointed out in the appended claims.

What I claim as my invention is:

1. In a telephone system, calling and called subscribers lines, automatip switches, tan

' a holding trunk, means whereby asubscriber ,on one of said calling lines may establish connections with a number ofsaid called s'ubscribers lines, a relay individual to theline of each called subscriber, and, means 'con trolled by the response of the SLIbSCliliGlflOil each of said called li-nes for energizing; the

associated relay to place theassociated called. subscribers line inconnectioni with the said holding trunk. V c

In a, telephone, system, calling subscribers line, automatic switches, ahol'ding,

trunk, a plurality ot called subseribefis lines, means under the controllofcthe subscriber on the said calling line for establishing connections successively with each ofs ,id called subscribers lines, a relay individualto each of said called lines, means for, energizing,

each oi? said relays upon the response of its subscriber on the associated called line, and

means controlled by each: relayfor connectins its associated called subsci iberslinet Q I I c scribe'r on said called line for placingthe said holding trunk. V a I a In atelephone system, a. calling subscribers line, automatic switches,a holdingtrun-k, a plurality of called.subscribers"lines,, means under the control of the subscriber on,

oneof said callinglines for establishingcon:

nections successively with each ofsai-dfcalled] ing, each ofrsaid relays up on the response.

6. Ina telephone system, calling and called subscribers lines; ,agutomatic' switches,

means whereby asubscriber ,on.,one of said calling linesmayestablish a" connection with alcall ed subscribers line tlii'o-ugli' a series of said, automatic switches, a holding trunk,

means controlled bythelsubscriber on said:

called line forjplacing his line in connection-with the said holding, trunk, and means under the control of the subscriber on said callingjline for releasing said series of automatic switches while the said called subscribers line is maintained in connection with the said holding trunk. 7. In a, telephone system, a calling subscribers line, automatic switches, called subscribers lines accessible there-to,meansunder the controlofthe subscriber on the said call ii'i'g line for, establishing ,connectionlwitl'i' one ofsa-id called lines by way of a series of said automat c switches, holtlliig tiilnli,

means controlled Jbythe response oftlie subsaid line in connection with the said holding trunk, electrical means under the control of the, subscriber on said callingline for releasin'g all, of, said series of automatic.

' inn; his line from tliefsaid holding-trunk;

of the subscriber on its associated lin,e, neans; controlled by each zrelay forfconnecting the associated called :subscribers line to these-id holding trunk, and'meansi for, maintaining,

' from either connector switch, means whereby thesubscriberon. said calling lineima estab each relay energized to maintain the line of theassociated CZIllGdJSUbSCllbQl in connection with the said holding trunk after the subscriber on said calling line replaces his receiver. e

a. In a. telephone system, a calling subscribers line, called subscribers lines, auto-- the response oteach oi? said called subsci-ibers for placing his line in connection with the lines previously called independent of said automatic switches.

In a telephone system, a calling subscribers line, automatic switches, called subscribei's lines accessible to said switches, a holding; trunk common to all of said called subscribers lines, means under the control of thesubscriber on the said calling line for establishing" a connection with a called subscribers line by way of said automatic switches, and means controlled by the response of the subscriber on the said called line for placing his line in connection with the said holding trunk over a path independent of the said automatic switches.

sllllfltz telephone system, aacallingisubseriberls line, two automatic the, other, a calledsubscribeids line accessible lHZLtlC switch, means whereby the subscriber on. said calling line may establish a second connection with the said called subscribers line by way of both connector switches, arain y individual to the line of the said called subscriber, and means for energizing said relay upon the response of the called sub;

scriber in the second connection only.

9. In a telephone system, a calling subscribcrs line, a. holding trunk, two automat-icconnector switches one of said switches accessible to the other, it called subscribers lineaccessible from either connector switch, means whereby the subscriberon said calling line may establish a connection with the subscriber on said called line directly from said first automatic switch, means whereby the subscriber on the said calling line may establish a second connection with the subscriber on said called line by way of both connector switches, a relay individual to the said called line, means for energizing said relay upon the res ionse of the subscriber on said called line in the second connection,

, connector I sw tches, one of I said switches accessible to and means controlled by the said relay for extending said called line into connection with the said holding trunk.

10. In a telephone system, two automatic connector switches, a line accessible to both switches, means for establishing a connection with said line by way of either switch, a relay individual to said line, and means for energizing said relay upon the response of the subscriber on said line when one of said connectors is used for the call, said relay remaining inert upon the response of the subscriber on said line when the other connector is used tor the call,

11. In a telephone system, two automatic connector switches, a line accessible to both switches, means for establishing a connection with said line by way of either switch, a relay individual to said line, means for energizing said relay upon the response of the subscriber on said line when one of said connectors is used for the call, said relay remaining inert upon the. response of the subscriber on said line when the other connector is used for the call, a holding trunk, and means controlled by said relay tor connecting said line with said holding trunk.

12. In a telephone system, a line, two sets of terminals, the conductors of said line be ing connected to both sets of terminals, a re lay, the connection of said line to one set of terminals including said relay in series, the connection of said line to the other set of terminals excluding said relay, a trunk, and means controlled by said relay for extending a talking connection from said line to said trunk.

13. In a telephone system, a line, a pair of branches for said line, step by step conl t. In a telephone system, a line, two sets of terminals, the conductors of said line be ing connected to both sets of tern'iinals, a relay, the connection of said line to one set of terminals including said relay in series, the connection of said line to the other set of teri'ninals excluding said relay, another line, a trunk, means for connectin said other line, to said trunk, and means controlled by said relay for extending a talking connection from said trunk to said first line.

15. In a telephone system, a plurality of lines each having two sets of terminals, the conductors of said lines being connected respectively to both sets of terminals, a relay for each line, the connections o't said lines to one set of terminals including said relays in series, the connections of said lines to said other set 01 terminals excluding said relays, a trunk line, a step by step automatic connector switch having access to said first set of terminals, means for controlling said connector switch to connect with said terminals, and means controlled by said relay for extending talking connection between its associated line and said trunk, independent of said connector switch.

Signed by me at Chicago, Illinois this 25th day of January 1921.

EDWIN E. JONES.

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