US1295229A - Telephone-exchange system. - Google Patents

Description

A. B. SPERRY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 28. 1908.

1,295,229. Patented Feb. 25, 1919.

3 SHEETS-SHEET I.

i www- A. B. SPERRY.

TELEPHONE EXCHANGE SYSTEM.

APPLlCA ION FILED JULY 23,1908 17,295,229 Patented Feb. 25, 1919.

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A. B. SPE'RRY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION HLED JULY 28, I908.

Patented Feb. 1919 3 SHEETS-SHEET 3.

1 U TED STATES FATE FFIGE.

ARTHUR B. SPERRY, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

l Specification of Letters Patent.

Patented Feb. 25. 19319..

Application filed July 28, 1908. Serial No. 445.769.

To all whom. it may concern Beit knownf'that l, ARTHUR B. Srnnny, a citizen of the United States of America, and resident of Chicago, Cook county, 1llinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems, of which the following'is a specification'.

My invention relates to telephone exchange systems of that character in which a private branch exchange is connected by one or more trunk-lines with a main exchange, the branch exchange being equipped with manual switchboards, and the main exchange being equipped with automatic switches, such as selectors and connectors, controlled by the subscribers thereof.

The object of my invent-ion is the provision of a manual switchboard operators cord circuit that may be used for connecting together any two subscribers of the same private branch'exchange, which may be used for extendin connection from an automatic subscriber 'o the main exchange to any subscriber of the private branch exchange, or which may be used for extending connection from an automatic subscriber of the private branch exchange to a similar subscriber of the main exchange, there being ample supervision of the connection in each case.

Another object of 'my invention is the provision of a manual switchboard operators cord circuit that may be used in con-..

junction or combination with a two-wire'automatic telephone exchange systemthat is to say,'an' automatic telephone system in which no-operating grounds are employed at the substations, and in which the automatic switches of the exchange'are, therefore, controlled by the subscribers over complete metallic line circuits.

It is also an object to provide certain details and features of improvement and combinations tending to increase the general efficiency of a telephone exchange system of this particular character, as will hereinafter more fully appear. f

To the foregoing and other useful ends, my invention consists in matters hereinafter set forth and claimed;

In the accompanyingdrawings Figure 1 represents diagrammatically an equipment for a private branch exchange embodying the principles of my invention. A subscribers automatic substation is shown at A,

suitable or approved type.

and at A and A are two manual substations. The line comluctors of each substatioir tern'linate in the usual jack. At C shown my improved cord circuit by means of which the operator may connect any two subscribers of the private branch exchange, or any subscriber of the branch exchange with any'snbscriber of the main automatic exchange. In the drawings are shown several batteriesB having their positive terminals preferably grounded; there may be, however, but one battery. Either arrangement constitutes a common means for supplying operating and talking current to the subscribers lines. i

In Fig. 2 there is shown diagramnlatically a. central ofiice equipment in connection with which I have elected to explain my invention. trunk-liine conductors which terminate in a jack at the private branch exchange (F l The master switch E controls theipluin At F is show a gers of the line switches. first-selector switch.

In Fig. 3 a connector switch is shown at H. To the line conductors of substation A there allotted the line switch I), which is the same as the line switch D Fig. 1) A central otiice ringer generator is shown at I, and at J is represented a busy-signaling device. A central battery, havin its positive terminal preferably groundee, is shown at B.

As shown in Fig. 1, the substations of the private branch exchange are of two types, automatic and manual.

The line switch D is attached to the The automatic substations may be of any 7 -As shown, it will be seen that substation A is somewhat different from the usual automatic substation, being arranged and modified to operate in connection with a two-wire systemthat is, a system in which no ground connection is used at the subscribers substation. Substation A, for example, comprises the 'usual receiver :2, switch-hook 3, the induction-coil i with the primary winding 5 impulse teeth 11 are adapted to engage tlle.

cam 13 upon the end of the spring 14 and thereby carry the latter out of engagement with the spring i5. Upon the switch'hook 2 there is the cam- 16 which, when the switchdiooli up, permits the springs 17 and 18 to engage. thereby bridging across subscribers line conductors l9 and 20 primary circuit including the trausmitin scrics with the primary wii'iding 5;

the the ter l but when the switch-hook is lowered the spring 17 carried out of engagement with. the spring 18 and into cng a mount with the ppriug in", whereby the ringer 5.) in series with Tim condenser bridged across the linc conductors 19 and .20 ii'istcad.

The manual substatitms A and A are of the usual standard common battery type with the line conductors terminating in. jacks at the private branch board.

The operators cord circuit C is an improyemcnt upon the usual manual con'nnon battery cord circuit, since means are pro vided whereby the operator may connect a manual substation with an automatic substation of the main excliiangc, and, also, an automatic substation of the branch exchange may be operated to establish com1cction with a subscribefls station of the automatic exchange. The cord circuit C comprises the usual supervisory relays Z1 and 2:2, supervisorylamps and 24c, and ringlug and listening key K. In addition there is provided a key K which is operated when the cord circuit is used incompleting a connection to the main exchange. Also, a switch M is provided for disconnecting the ground at the tip from the supervisory lamp r 3 when c lesired. At 0 there is shown an operators set with a calling device.

The line switch D and master switch E are of the general type disclosed in English Patent No. 26,301 of 1.906, and in the l'lcsfmalfl ccfiricimi of January 25, 1908. The circuit connections are, however, modified to adapt the switches to operate in connection with a two-Wire system--that is, any"- tcm in which there is no ground at the subscribers station.

The first-selector switch F is of the gen-- cral type shown in United vStates Letters Patent No. 815,321, granted March 13, 1.906, to Keith, Erickson Erickson. As shown in li ig. 2, the bridge-cut-ofl relay and the normal conductors have been omitted, and the circuits are otherwise changed to opcrate in conjunction with the line switch D.

The connector switch H (Fig. 3) is ol? the ,p cncral type of connector switch shown in [initcd States Letters Patent No. 815.176, granted March 13, 1906, to Keith, Erickson & Erickson. Like the line switch l) and the firstsclector F it is arranged to operate in a system in which there is no gro" id connection at the subscribers station.

A. clearer umlcrstaudimr oi the operation of my improved cord circuit may be had.

from an w ilanalion ol its operation when employed to connect two liucs. As prcyi stated. the cord circuit (7 is a. combimn tion, circuittbat is. it only be used in a private branch exchange to complete the connection between any two local subscribers in the usual mamul', or it may be used when any subscriber of the branch exchange desires a connection with a subscriber ol the main automatic exchange. The branch ex change operator. or the calling subscriber himself provided hc calls from an automatic substation, may operate the main ollicc switches to establish the desired conncctioi'i. Furthermore, a call coming from the main automatic exchange to the branch exchange may be extended to any subscriber of the branch exchange through the medium of the cord C. For example, it will be pointed out how a subscriber of the private branch exchange may be connected with a subscriber of the main exchange. Suppose that the subscriber at the automatic substation A dcsires connection with the subscriber at substation A, (Fig. 3). In that event, when the calling subscriber I'OII'IOYGS the receiver from the switch-hook an energizing circuit is closed through the line relay 25 (Fig. 1) extcruling from thaground i through lhc jack springs to the line comluctor fill. through the substation A, to the line coin ductor 19. jack innings. line relay 25, to the battery B. thence to ground (it. The line relay energizes and closes a circuit through the line lamp 20, whereupon the operator inserts the plug 1 into the jack j. This breaks the energizing circuit for the line relay 25, which is then restored to normal position. The operator then throws the listoning key K to bridge the operators set 0 across the line. The subscriber at substation A is provided with battery current from ground G through the springs 27 and 28 (the hey l'C being in. normal osition). through the winding 29 of the su jicr isory relay 21. sleeve condlu-tors ot' the plug p and jack j to the line conductor 20. thence through the substation to the line comluctor l9, tip conductor of jack j and plug 7 winding- 30 oi? the relay 2].. springs 31 and 3'2. thence through battery B to ground (i. The

relay 21 energizes and attracts its armature 33, thus disen 'aging the contact point 3 The opcratofis set is provided with talking battery current from ground through the winding 35 of the supervisory relay 22. springs 36 and 37, springs 38 and 3t). contacts ll) and 41 ot' the key K, through the primary circuit of the set (1. key contacts and i springs H and 417 and +6 and -17 of the key K, winding. 1 8 of the relay 2)., thence through battery B to ground The relay encrgizcs and attracts its armature it thus disengaging the contact 50. The operator, after learning that a subscriber of the main exchange is desired, inserts the plug p into the trunk-line jack j", arid, since the calling subscriber is at the automatic substation A, the operator throws the key K to the position shown, placing the springs 28 and 39 and 31 and let in contact, thereby extending the calling subscribers line conductors 19 and 20 to the trunk-line conductors 51 and 52. The calling subscriber is then able to establish the desired connection, independently of the operator. To call the number 220, substationA (Fig. 3), the subscriber at substation A (Fig. 1) operates the calling device for each digit in the well-known manner-thatis, when the substation line conductors 19 and 20 are extended to the trunk conductors 51 and 52 by the throwing of the key K, a preliminary impulse provides an energizing circuit for the trip magnet 58 of the line switch D, whereby the line switch D is operated to seize an idle trunk-line leading to a firstselector switch. The dial is turned for the first digit and, upon returning to normal 'position, operates the first-selector switch to establish connection with an idle trunkline leading to connector switch. The inn pulses delivered by the dial for the last two d its directed toward the connector H, which operates to place the shaft wipers in connection with the contacts comcsponding to the desired number. The nary impulse .or energizing the trip ma net 53 occurs when the substation line conductors are nded to the trunk-line conductors and orimary circuit is bridged across the line.

ll' hcn the primary circuit is, thus bridged' acre" the line, the energizing circuit for the tri magnet is completed and extendsfroni 40 d G (Fig: 3) through the trip magnet 7,1. 0 ducts. 52, through the sleeve of the eel: j and plug springs 39 and 28, winding 29 of the supervisory relay 21, sleeve of the plug p and jack 1' to the line conductor 20, through the springs 17 and 18, impulse springs 15 and 1%, primary winding 5, transmitter 7 to the line conductor 19, tip of the -jaclr j and plug 7], winding 30 of the relay 2i, springs and -14, tip of the plugp and jack to the trunk-line conductor 51 {Fig 2)., springs 56 and 57, through the resistance coil58 to the battery lead 59, thence through to ground G. As soon as the trip et energizes, the armature is at C thrust into the banlr terminal. When the plunger engages the bank terminal an energizing circuit established through the motor magnet relay 60, which in turn operates to close an energizing circuit through the motor magnet 61 of the master switch- E. {The motor magnet then operates to advance all idle plungers that are in locking engagement with the she-lit 62 to a point opughthe springs 54: and 55, trunk con-.

d and the plunger is liberated and.

posite the next idle bank terminal. similar to the terminal just engaged. The circuit through the relay extends from ground G through the winding 63 of the relay to the common segment 64, thence through the wiper 65, th rough the segment 66, conductor 67 bank terminal springs 68 and 69, through the winding of the release magnet 70 to the battery lead 59, thence through battery B to ground G. Although this circuit includes the release magnet 70, the said magnet does not operatively energize, since the winding of the relay 60 is of a high resistance, while.

the winding of the release magnet 7 O is comparatively low. The relay 60, upon energizing, operates to place the springs 7 2 and 73 into contact, whereby a circuitis completed through the motor magnet 61 extending from ground G through the springs 7 2, and 73, motor magnet springs 7 4 and 71, through the winding of the motor magnet 61 to the battery lead 59, thence through battery B to ground G. The motor magnet 61, upon energizing, attracts its armature 75, whereby the pawl 76 engages the ratchet wheel 77,

advancing the latter one step. When the I engaged assuming that the next succeeding trunk is idle. Consequently, the Wiper arm 65 is carried from the contact point 66, which corresponds to the engaged terminal, to the contact point 80, which latter corresponds to the terminal before which the advanced idle plungers are now restin Suppose that nine subscribers have cal ed, and that the master switch hasthus operated nine steps, carrying the w1per'65 tothelast contact point 81. Now, when the motor magnet 61'.

operatesfor the next step, when the tenth subscriber calls, the wiper 65 passes back and drops into engagement" with the contact point 66. If the first trunk is still busy the wiper 65 finds a battery potential on the corn tact 66, and an energizingcircuit is established through the differential relay 60,

which in turn'operates to close an energizing circuit through the motor magnet 61. The current through the saidvrelay 60 flows from the said contact 66 through the wiper 65 to the common segment 6%, and through the windingv 63 of the difierential relay 60 to ground G When this relay energizes it operates to close the circuit through the motor magnet 61, and the motor magnet then operates, as previously explained, to

rotate the ratchet wheel 77 one step, and the master switch bank wiper (3.3 one step also and into engagen'ient with the second segment 80. When thus advanced one step the plunger sha't't 2 carries all idle plungcrs that are in locking engagement with said shaft to a. position opposite the first idle hank terminal, as previously explained. If there should be a guardiiu potential at the bank segment 80 the di'tlerential relay (30 will remain energized, whereby the energizing circuit through the motor magnet (31 is again completed when the motor magnet springs 71 and 71 again engage, and as a resuit the motor magnet 61 is again operated, whereby the plunger shaft. (52 and the master switch wiper 65 are advanced another step. T his process continues as long as the wiper (55 continues to find segments with guarding potentials. As soon as an idle segment is found, however. the energizing circuit through the relay 00 is broken, at which time the said relay in turn breaks the energizing circuit for the motor magnet (31 until the next subscriber makes a call. At the instant that the plunger enters the bank tcr-.

iniual the following springs a re pressed into contact: 68 and 69, 82 and 83, S1 and 85, and 86 and S7. The engagement. of the Springs 81 11116185 closes a circuit. through the cut-otl' relay 89 extending from ground G through the springs St and 85, relay S9 to the battery lead 59, thence through battery B to ground G. The said relay, upon energizing. open ates to carry the springs 5 and 50 out oi engagement with the springs 57 and at. hen these springs disengage, the resistance coil 58 is disconnected from the trunlc line conductor 51, and the trip magnet -53 is disconnected from the trunleline conductor 52. The engagen'ient of the bank springs 81-. and 85 also establishes a guarding potential byway of the normal conductor 00 to the connector private bank contacts correspomling to the trunk-line that terminates in the line switch I) to prevent any subscriber from calling the said line after the trunkline has been engaged at the private branch exchange, as explained. Also, the closure of connection between the springs (38 and on establishes a guarding potential at the master switch bank contact (36 over the following circuit: from battery B to the battery lead 51), thence through the winding of the release magnet 70, through the springs 09 and 08. conductor 01 to the said contact point 60. It will be understood that the engaged bank terminal (being the first bank terminal of the line switch bank) correponds to the first scgn'ient ()0 of the master switch bank and, therefore. to the trunk-line the conductors 9;. 92 and 01- of which termihate in the first-selector switch F. This guarding potential protects the seized trunk conductors 02, 93 and 94- from being seized.

COIMlIK'tOI' .20 to the trunk conductor 0:; and

to the side switch wiper 90 of the selector 1*. The subscriber has thus established connection with the selector switch, which now operated by the impulses that are delivered when the dial returns to normal position tor the first digit. 1V hen the subscribers line conductors 1.9 and 20 are thus extended to the first-selector switch F an energizing circuit is established through the line relay 5)? extending from ground G through the winding 98 to the contact point 99, side switch wiper 96, trunk conductor 93 through the bank springs 87 and S8 to the trunleline conductor 52, then through the sulgistation and to the trunk conductor 51, as previously explained, through the bank springs 82 and 83, trunk conductor .12, side switch wiper 95,

contact point. 100, through the winding 101 to the battery lead 50, thence through battery B to ground G. The relay 97, upon energizing, operates to place the springs 10: and 103 in contact, whereby an energizing circuit is established through the release relay 10-1: extending from ground G through the springs 102 and 103, relay 101 to the battery lead 59, thence through battery to ground (it. The release relay 101, upon cncrgizing, operates to carry the spring 1053 out of ei'igagcment with the spring 10(1 and into engagement with the spring 107. This is the condition of the firstselector switch F when the subscriber operates the dial for the first digit. The first digit being 2, the impulse spring 14- is twice carried out of engagement. with. the impulse spring 15. As a result the energizing circuit through the line relay HT is broken twice. and the spring 10E comes into contact with the spring 108 twice. After the two impulses are thus delivcrml the line relay J7 again energizes and carries the spring 102 into contact with the spring 10 3. The relay 101 is a sl(nv-:u:ti1ig rclaff that is, slow to deiinergize: and when this energizing circuit is momentarily broken during the vertical impulses just delivered, the said relay does not dciincrgize, but remains in an operated position with the spring 105 in contact with the spring 107. Then when. the spring 102 engages the spring 108 two impulses are transmitted to the vertical magnet 109 from ground (1 through the springs 109 and 108, to the springs .105 and 107, through the private magnet relay 110, through the winding of the vertical. magnet 109,

contactpoint 111, side switch wiper 112 to the battery lead 59, thence through battery B to ground G. Twoimpulses being delivered, the vertical magnet 109 is thereby energized twice, and the shaft wipers are given two vertical steps in the well-known manner. It will be seen that the private magnet relay 1 110 is included in the energizing circuit of the'vertical magnet 109. This relay also energizes, but being a slow-acting relay it energizes on the first impulse and remains so until all the impulses are transmitted. This relay,,upon energizing, operates to close the springs 113 and114 in contact, whereby anenergizing circuit is established through the private magnet 115. This circuit extends from ground G7 through the springs 113 and 114, private magnet 115 to the battery lead 59, thence through battery B to ground G. The private magnet relay 110- deenen' giaes after the last vertical impulse, since this energizing circuit is no longer maintained after thefsprings 102 and 108 disengage. Hence, the said relay deenergizes,

' permitting the springs-113 and 114 to disengage, whereby the Y energizing circuit 1 through the private magnet 115 is in turn broken, which private magnet now denergizes and permits the side switch to pass from first to second position, allowing the I side switch wipers-112 and 116 to'engage-the contact points 117 and 118, respectivel The closure of contact between the si e switch ugiper 112 and the contact point 117 sets up an energizing circuit for therotary magnet 119 from ground G through the interrupter springs 120, through the winding of the rotary magnet 119, contact point 117.

side switch wiper 112 to the battery lead 59,

.and through battery B to ground G. The

"position. The energizing circuit for said private magnet extends from the grounded,

terminal Gof the battery B through an oncupying switch (not shown), through the private wiper 123, thence through the conductor 127 to the side switch wiper 116,- contact pointg118, through the winding of the privatem'agnet' 115 to the battery lead 59 thence through battery B to ground G. The private magnet .115, upon-thus becoming energized, loclrsthe side switch wiper 112*i'n engagement with the contac 'oint,

117, whereby the rotary magnet 119 will be energized step by step until the wipers are carried beyond the last busy trunk-line. At the instant the private wiper leaves the last busy contact point the energizing circuit tl'irough the private magnet 115 is destroyed,

and as a result the selector side switch passes to third position. If, however, there are no busy trunk-lines, the private magnet 115 re leases the side switch to third position as soon as the wipers are carried into engagement with the first trunk-line. As soon as the side switch passes, to third position, as

stated, the subscribers line conductors l9 and 20 are extended to the conductors 124 and 125 which, in this case, it is assumed lead to the connector switch F. The extending of the line occurs, of course, as soon as t'he'side switch wipers 95 and 96 engage the contact points 128 and 129, respectively. When the subscribers lines are thus extended 'to, the

connector switch H, an energizing circuit is established through the line relay 130 in the same manner in which the energizing cir-- cuit was established through the line relay 97 of the selector F, when the subscribers line conductors 19 and 20 were extended through the line switch bank to the trunk conductors 92 and-'93. The energizing circuit through the line relay 130 extends from ground Gr through the winding 131, trunk" onductors 125, 93 and 52 to the line conductor- 20 thence through the substationto the line conductor 19, trunk conductors 51, 92

and 124, thence through the Winding 132 to the battery lead 59, and through battery B toground G. The line relay 130, upon energizing, operatesto shift the spring 133 from the spring 134 tothe spring 135,,whereby an energizing circuit is established through the release relay 136extending from ground Gr through the springs 133 and 135, relay 136' to the battery lead "59, th'ence through battery B to ground G. Then the relay 136 energizes, the spring 137 is shifted out 'of contact with the spring 138 and into contact with the spring 139, and the spring 1, 1401's shifted into engagement with the spring 141. 'This primary operation of the connector relays 130' and 136 occurs at the instant that the side switch wipers of the selector F pass to third position and axtend the subscribers line conductors to the connector H. The engagement of the springs 141 and 140 establishes a guarding potential for protecting the trunk-line conductors 124,

andvl26 against seizure by :another line and first-selector. This potential extends from ground G to the side switch iwiper" 142, springs and 141, conductor 12,6 to the private bank contact engaged by the shaft wiper 123. Furthermore, when the side switch of the first-selector F passes to thirdpfiition a .new energizing circuit is established through the release relay 104, said iso circuit extending from ground G at the connector switch to the coi'nluctor 12th through the shatt: wiper side Switch wiper 116, conductor H3, through the release relay 10% to the battery lead 59,. thence through battery 13 to ground U.

The operation of the. dial tor the last: two digits affects the connector i-zwiteh. and when the dial is operated for the seroi'ul digit .2 the iinpnlse spring l-i is twice carried out of en* gageinent with the spring 15, thereby mo" mentarily deenerg'zing the line relay 1230 twice, whereby the spring;

rm mice engages the sp 'ing 13- thus sending; two impulse to the vertical nuigne't l tt from ground G through the spring 133 and lit-fl, springs 137 and 139, through the vertical magnet, 1H, contact point, 145, side switch wiper 'l.--l-(5,prirate magnet; relay M7 to the hattery lead 59, thence through hat -y B to ground ii. The private magnet relay 14:7 energizes when the 'lirat impulse is delivered, and since the said relay is slow-acting it remains in an operated position until all, the rertieal impuiuea ha e been sent. The vertical magnet, upon being energized, ope ates one step at a time to rarr the shaft wipers l-lS, 14-5? and 1530 two steps to a point opposite the serond level. The relay iii", upon energizing, shifts the spring 151 out o-l engagement with the spring 152 and into engagement with the spring 1.33: also the apring 171i i shifted out of engagement with the spring 153. \Yhen the springs 151 and 153, engage; an energizing circuit in established through the prii'ate magnet 15.) from ground tit through the springs 153 and 15h private magnet; 15.1 to the iuittery lead 59. thence through hatter ii to ground (i The relay 1H being a ulon aetinyg relay remains; in an operated position while the vertical iiut'mlrig are being aent, but after all the iinpua' have been delivered. and the line re jliai returns to ita operated poeition. the circuit through the relay l-lT heromen lirolqen, thou permitting the upringrs llil and ,l i'i' in re turn to normal ptiri iimh When to aprii Y151 and 13.") d-ieen a u the circuit 'tl'nough the prlrate nu met lilo iitaftillltr broken, wherein the Hard nuurnet th fiuergzixe-= per mittinn' the aide -ewiteh to 5 li to Fitt'Ullti lmfiiliull. 'lhe rail iiillli l()(ii\l 7 through the rotary magnet 1-56 to the contact point 15$) thei'uze through the aide switch wiper l ili. through the primate magnet relay ii; to the, bath: lead a. thence through hatteev ii to ground '(t. Again the private magnet relay energizes. a;

in the pl'etious cane, remaining; so until all the impulses are transmitted, thereby retaining the private lllttilflltt energized also. The rotary magnet; .76 then operates to rotate the shaft wip into on men! with the desired line $1-21) it thin line ht "y at the time, the connector aide awiteh will he locked in secont, position, It will he 21:1" sinned, however that the desired line in not hour and that the connection in (""ttiiih-llltti. As soon a:-: the line relay 12h) chat/e; to ri eratae for the h e-t digit tlze t-rirate relay l-tT definerggivra an hei plained, in thin instance permittin the do switch to trip to third position. '1. in result is that the side switch v pers res iet'ti ely en an an t;

p H their third-position rontae points. \Vhen the side SWli/tll wiper ltiti engages the contact point; 1(3)", a guarding; potential it; ctnnpleted. at the prlxatr 'wqiier tilt? tor pro-- tecting the seized line l 'o outauie inter-- entahli hed. eauendrs from int. thenre h'ili terenee while the ennin This guarding ground it to the contr.

ot the side in way springs 1t and 1th, "l

ihh paesea e an dnetor has that ltliiL- leetor and the eonnemor 1: 1 r :i. ml with "iiu -l. i" tln' uuh in? to 1.1a.

trunh coiulurtor the 51th switch z t lantain a 3. nag ianentuil it? in also proiided trout aide raviteh wipt this :hatthe :u around a l-iterrapiol ii: the line relay n in operating and there a pc-eihilit v oi sell :tor en'uila to the Eselertor i tl same trinih-iine. .kiterth to third poaition however, 1 dunner. and the potential wound through the line relay sprin ated. (it course, when the aide switch pera lit) and Ni engage their l'illlti-POSiilUll contact points 172 and 173 the calling eubarriher line platted in trounce tion with the called anhiscrihefis line over the heavy conductors ahown passing; through the ringer relay apringe 1H and 175 on one side, and 176 and 177 on the other side. moon as the coi'meetihn is thus established,

nn-Quinn rein.

prori h ou the;

the ringer relay 178 is energized over the circuitestablished when the side switch wiper 146 engages the contact point 183, the energizin scurrent flowing from ground G d lay-springs 175 and 177, thereby breaking -connection between the calling line and the called line, and pressing the springs 174 wand 176 onto the springs-184 and 185 which arethe terminals of the ringer generator I.v

result ringing current is sent over the i? called line for energizing the bell 186 while the springs 187 and 188 are in contact.

However, as soon 'as the called subscriber answers, the'back-bridge relay 189' is energized by'a flow of current from'ground G contact point 161, side switch wiper 160,

Winding 190 of the back-bridge relay 189,

j ringer relaysprings 177 and 176, side switch through battery B to wiper 171, contact point 173, rotary-line .wiper 149,- normal conductor 165, line conductor 191,- switch-hook springs'188 and 192, impulsesprings 193 and 194, transmitter 195, line conductor 196, normal conductor 164, shaft wiper 148,: contact point 172, side switch w1per-170yringer relay springs 174 .and 175, winding 197 of the back-bridge relay 189, thence to the battery lead 59, and ground G. Once the back-bridge relay 189-is energized, however, the energizin circuit for the ringer relay 178 is interrupts at a point between the springs l and 181, thus making it impossible for ringer relay to -energize as lon as the calledsubscriber is; on the line. 'fhe subscribers being thus connected they may 330mmunicate over themain talking con'du tors 5 and 3, .and

indicated by the heavylines-in Fi 's. 1, 2

denser 2001' other sidethe'condenser 201. 'iAtter the subscribers are through if the ciilling subscriberhangsup his re-- ceiverhej.'upens*np the line circuit at a point between the p,rin gs17 and 18 thereby iniiatin'g the release' of allfQf the/switches. 'llhis release is brought-about as follows:

' At the instant that the circuitis broken between the said springs 17 51111118, the-double woundi-line relay.1 30. and the release relay 136 of the connee 1H deenergize. *At the" instint that are at. acting relay- 136 and theline relay 130 dgnergize, the energizing 'rupted by both of these relays.

including on one side t econ-f the connector H, and onthetalking,

circuit for therelease magnet 202 is closed at a point between the springs 137 and 138 and at another point between the springs 133 and 134. A flow of current is, therefore, set up 'from ground G through the springs 133 and 134, through the springs 137 and 138' to the release magnet 202, thence through said magnet and to the oft-normal spring 204, to the contact point 203 and to the battery lead 59,

thence through battery B to ground Gr,

The release magnet instantly releases the connector switch shaft and side switch, thereby breaking the energizing circuit through the back-bridge relay 189 if the called subscriber has not in the meantime restored his receiver, and also the energizin circuit through the bridge-cut-off relay 16 of the called line switch D. As soon as the connector switch shaft reaches its lowest position it breaks the circuit for the release magnet 202 by separating the offnormal spring 204 from the contact point 203, at which instant the release magnet of the connector is also restored.

The operation of the line relay' 130 and of the slowacting relay 136 not only causes the release of the connector, as described, but also the release of the preceding switches, because the ground connection from ground G to the trunk-release conductor 126 is inter- Since the release relay 104 is dependent upon this ground for its energized condition, as already explained, it follows that they will fall back, with the following results: As soon as the release relay 104 of the selector F deenergizes, the springs 105 and 106 are brought into contact, and as a result the energizing circuit for the release magnet 205 is closed. The energizing current for this release magnet 205 then flows from ground G through the springs 102 and 108 and through the said springs 105 and 156' to the release" magnet 205, thence through said magnet to the contactpoint 206, oft-normal spring 207 to the battery lead 59, thence through battery B to'\ ground G. The release magnet, upon ener izing, then restores" the first-selector"; side switch andswitch shaft, which switch shaft, upon reachmg" its lowest position, opens the en- ;gizing circuit for the release magnet'205 ata point between the ofi normal spring 207 and the contact point 206. Furthermore, when the release magnet 205 energizes and closes the springs 208 and 209 in contact an energizing circuit is established throu h the" release magnet of the line switch This circuit extends from ground G through the springs 208 and209 conductor 94 to the bank springs '68 and 69, thence throngh .the release magnet 70 of the line switch ,D to the battery lead 59, and through battery B" to ground G. It will be seen that the release magnet will then energize and attract its armature, ren'iaining in readiiess to restore the switch. As the release mac net 205 deenergizes and separates the springs S and 209, the release circuit is broken...which permits the release magnet 70 oi." the line switch I) to deiinergize, thereby withdrawing the plunger from the banlc terminal. As a result the bank springs 68 and an, as well as the other bank springs of the line switch D, are sepa 'ated, thus preventing any other action from the trunk. .X'tter the switches are thus restored, of course, the calling subscriber can then procoed to make another call.

Furthermore. when. the subscriber at substation A. restoires his receiver, the coerciniug circuit through. the windings 21 and oi the supervisory relay 21 (Fig. 1) becomes broken, and the relay armature 33 returns to normal position in contact with the point 34-. thereby closing a circuit through the supervisor vy lamp The glowing of this lamp indicates to the operator that the subscriber at substation A. has restored his receiver and no longer desires the trunk-line connection. The plugs 1 and p are removed from the jacks j and. j and the key K is restored to normal.

H ad the subscribe at the manual substation A? desired connection with the auto-- matic station A, the connection would have been made by the operator. The plug 3) is inserted in the jack j and the plug 1') in the trunk-line jack j. The key K is operated to.place the springs to and 40, and 4:7 and 210 in Contact, thereby bridging the opeators set and calling;' device O across the trunk-line conductors 51 and The operator then operates the calling device once, in the usual manner, tor each digit of the desired number to complete the connection. After the desired connection established the ,key It" is thrown in the opposite direction, and the line conductors of .the substation A are extended to the trunk conductors 5i and When the subscriber at substation A. restores his receiver on the termination of the connection. the circuit through the coi'inector line relay is brol; i as criplaii'lcd in connection with substation A, and the central otlicc switching apparatus is restored, in the usual manner. JtlSU, when this occurs the circuit through the supervisory relay 21. is broken and the opcrator ,l i\'0i3, a disconnect signal. lt 'should also be pointed out that the substation A. by means of the cord C, may become a regular substation of the main automatic exchange. This is sometimes desirable, as at night. For instance. the trunk-line may be pl ugrpgcd in on the substation A. and all it up; tails are receiredat t :ation it: also may be made Ttroni the suljistai ion it.

when the to the main exchange.

u rec,

relay armature 31-3.

would be in. a deenergized position. and the signal lamp 253 would glow continuously, but to meet this condition the night switch M is provided, whereby the ground at the jack may he cut oil from the superirsory \Yhen a call comes in over the trunleline tor a subscriber at the branch exchange an energizing circuit is closed through the trunk-line rela v' .ZiiZ including in series the ringing current grencn ator ot the r; lliug connector. The line relay upon energizing, closes a circuit tl'irouah the signal lamp 213. The opera tor re ponds by inserting the plug p into the trunlcline jack y", and upon learning that substation A for example, is wanted insects the plug p into the jack j, and throws the key K to the position shown. This oporation extends the trunk-line coiuluctms 5i and 52 to the line conductors of the substation A T line is not in use the SHPG'L'VlStH'V relay 21 lhe substation A then receives ringing current direct from the connector of the automatic exchange. When the sub scriber a i subs a tion A answers, the baclc bridge relay of the connector energizes and ln'eaks the eneigiziug circuit for the ringer relay in the same inanne' as when an aulornatic substation is called.

The cord circuit (1 may also be used to complete connection between the lines of two local private branch exchange subscribers. Suppose that a local subscriber A desires mnncction with another local subscribe' at substation A The plug 7) is inserted in the jack j and the plug 7) in the 'jaclt j. The keys K and h remain in normal position during conversation; the substation A is provided with talking" battery current through the windings oil' the supervisory relay 21, and through the winding of the supervisory relay 213 the substation A. receives similar cur rent. These two relays energize and attract their respective armatures, but. when either subscriber restores his receiver the corre sponding supervisoiy relay dchncreixcs and permits its armature to engage its contact point, thereby closing a. circuit through the supervisory lamp. This circuit cstends from ground at the jack over the third con duclor to the relay armature and contact point through the supervisory lamp to the battery B and to ground (l. The opu'alor is thereby given the disconnect signal and accordinglv removes the plugs from the jachs. i

in the 'l'orecgoino it has been shown how my improved cord circuit may be used in extending a connection from an automatic substation and from a manual substation ot the private branch exchange to a subscriber ot the main mitoniatic exchange: also how a :di lHi'i Wt of th* automatic exchange may call and receive connection with a subscriber times, regardless of the character ot the 'liue-t.hat to say, one adapted necof the branch exchange. l urtherinore, any two subscribers stations of the branch change may be connected by the cord C in the usual Way. When the cord is llSttl in a trunk-line connection the trunk kc it is thrown to the position lIUllCit-ti, ano the relay 21 controls the circuit of the supervisory lamp 23, the snpervisonv relay :32 being disconnected from the circuit when the key K is thus thrown The key i used only when the cord is nsctl in a t r connection, the key K. being the usual 1 nging and listening key. Thus it will be seen that the. cord circuit C not limited to service in one class of connections but is a combination cord, antl admits of use both in local Connections anal in trunk connections, which latter may, moreover, be either incoming or outgoin".

The corcl circuit C is, therefore, 01 uni-- versal utility being adapted for use in trunking either from or to the niain e);- change, and being also adapted for conneq ing any two subscribers of the branch ex" change. There. is innple supervision a all connection. The supervision is clonble l; lo-al connectiens-that is to so there both front and back supervision-1*hil calls from the main to the branch GXCllil or from the branch to the main QXCl! thereis single. supervision only. it will be seen that this corrl c adapted to operate in conjunction with twoovire telephone systein-that is to say, system of the linrl shown in which no L erating grounds are employs at the sulw stations, anrl in which the antoiimitic switches of the erchange are, therefore, controlled by the subscribers over complete metallic circuits. Again it will be scen'i'hzr; "trunk-line extending between l and main exchanges is a two-Ha in either direction. The coral pleinecl, is a l with the twoox zalling connertio.

What l claim as in l. in a telcpli 111,21 two-way line, a spring jiac one end of Fil tl line, an opcrah l'tl n'on'iileil plup' for ins 'on in rail LL02} over llll, trunloliuc in one i an automatic H\\".i 'l1 l seizing; lll

cml of said trunk-line to extend connection over thosanxe in the opp itc ilirection. means in said (UUtl circuit 2' sii mrrisii 3 the connections ainl another alumna-.1; switch controlled PJi'i' llittwo siilcs ol' coral, rircni' in i(l'l\* lin conncr tion from one curl in a it line, a spi mo sail;

an operato cortl plO' ltlet l will: a plug rtion in said. nc-l; to extend conneomoo oi'er trunk-l in in one (l tCl'IOH, an.

the

:nuiormrtic snitch for sizing tl: other end no to w nd connection over direction, another extending connection n one end a. l trunk-line, and means h a a, bscribcr may control -llllllt 1)llC(l automatic switch after the said plug; has been inserted in said jack. n lephone ,s cm, telephones, a

3. a. tvoconductor line individual to each telephone, a two-way trunlbline, 2 non niunerii-al tri ing; switch for extending connection tr one of saitl trunk-line, means ior "10 tion to or from the other einl oi saui trunk-line. and means by which a' calling subs r'ber controls Til switch over two sides or the line circ nt in series 7 l. in o :IVQt'GYQ, telephones, a

two-conductor in phone. a twoo switch zlloiil'ed to one end for extending onnection therefrom, means by ranch u ribcr controls said line circuit in Aug connection of said trunk-line.

the )1){). to three-- ich calling subscribers a .iutonn .it' switches over two N the line circuits in series. in a telephone s our, subscribers line circuits including; a pair o'l" talking conduca two Way trunk line, automatic es. nicrins b which calling subscribers Hillll switches over s: itl talking cons in te xl calls over said line in opposite ii L'l'lOil S, and a two; col-(l circuit utlfiplt il. or use in calling either iirm'tion over lrunl; line in a iclrphon a subscribers" lint: s inclul r oftulking rronilue inc. a manual switcln circuit whi h istww notions to or from. 'unl; line, an automatic 5 iltl o" swiicli for i rnil oi saiil trunk line, and. means by a sun-Tiber calling over saifl cord circuit and trunk line controls said automatic switch irer a pair oi said talking; coraluw '74 Ill hllli ti in a telephone *i'til'lll. a :wom'a) truul'- automatic i. l extending connet-lion to or from one cml ol ill saitl trnn-t for ex ending a cell ending: a connection from the" line, a jack for the other end of said trunkline. subscribers lines, and a two-strand cord circuit for extending connection from a subscribers line to said trunleline, or vice versa, depending upon the direction of the all, one of said switches controlled over the two sides of said cord circuit in series.

9. In a telephone system, a two-way trunk-line, automatic devices for extending connection to or from one end of said trunk-- line, a spring jack for the other end of said trunk-line, subscribers lines, a cord circuit adapted for connecting together any two of said subscribers lines; means for adapting the said cord circuit for, use in connecting a subscribers line with the said trunkline, and a supervisory signal for the cord circuit controlled by the calling subscriber.

10. In a telephone system, a two-way trunk line, an, automatic switchforextending connection from one end of said trunkline, another automatic switch for extending connection to the same end of said trunkline, a spring Jack for the other end of said trunk-line, a line signal associated with said spring jack, subscribers lines terminating at a manual switchboard, an impulse sender or calling device for the substation of at least one of said subscribers lines, an operators' cord circuit for connecting together any two of said subscribers lines, means by which the operator adapts the said cord clrcuit for use in extending connection from the line.

having the calling device to the trunk-line, said cord circuit being two-Way to extend connection either to or from the trunkline, and means whereby both front and back supervision is given the operator at the said cord circuit. v

1.1.. In a telephone system, a subscribers line including a pair of talking conductors, an ope ators cord circuit, an automatic switch, means for connecting said cord circuit with said switch, and means by which a callin subscriber controls the said automatic switch over said talking conductors and the two talking strands of said cord circuit in series.

12. In a telephone system, a subscribers line circuit including a pair of talking conductors, a trunk line extending fromone exchange to another, means for establishing a connection between said line circuit and said trunk line, an automatic switch at one end of said trunk line, and means by which a calling subscriber controls said switch over a ircuit including the two talking conductors oi both the sul.)scribe1"s line and said trunk line in series.

13. In a tcleplame system, a metallic line circuit. a trunk-line extending from one eX-' 'liHilf- O. to aimther, means for establishing a. (10H between said linc circuit and said Hilts-H121, an automatic switch at one end of said trunk-line, and means for controlling said switch over the metallic circuit includ- 16. In a telephone system, line circuits each including a pair of talking conductors, a trunk-line, anautomatic switch for seizing said trunk-line, another trunk-line, a non-numerical trunking switch for automatically connecting the first trunk-line with the second trunk-line, and means for controlling said switches over line circuits each including a pair of said talking conductors in series.

17. The combination, in a semi-automatic telephone exchange trunking system, of selectors and connectors responsive to a calling subscriber, and means by which an operator connects a' selector with the line of the calling subscriber before the call can be extended in the direction of the called subscriber, a line'relay for each selector and connector, each line' relay being energized over two sides of the calling line in SQIIGS.

18. The combination, in a telephone exchange system, of a plurality of subscribers lines, a number of first selector switches less than the number of subscribers lines, a trunk, means manually controlled for connecting said trunk to any of said selectors and to any calling line, whereby such said first selector switch is brought into connection with any calling line, together with means whereby the said selector switch may then be controlled by the subscribers to select the llne Wanted whereby a talking circuit maybe set up between the calling and the wanted lines, said talking circuit including conductors in both sides of the calling line,-

and to restore the switches after use, and

signal devices connected with the manual portion of the apparatus to indicate to the operators the necessity for connection and disconnection, each selector having a line relay energized over said talking conductors in said both sides of the calling line in series, substantially as described.

19. The combination, in a telephone exchange system, of a plurality of subs(.'ril.,-vrs lines, a number of first selector switches les.

than the number of subscribers lines, means including operators cord circuits for connecting said first selector switches with the calling lines, each of said cord circuits common to said selectors for connecting any line with any selector together with sending devices at the substations, and responsive devicesat' the central station whereby the said selector switches may then be controlled by the subscribers to select the lines wanted to establish a talking circuit that includes a conductor in each side of the calling line, and to restore the switches after use, lineannunciators and clearing-out annunciators connected with the lines and cords, respectively, to indicate to the operators the desire of the respective subscribers for connection and disconnection, each selector having a line relay energized over said talking conductors in said both sides of the calling line in series, substantially as described,

20. In a telephone system, an automatic switch for finding the called line, means including operator controlled connections for connecting said switch, and aline relay for said switch energized over the two sides of the calling line in series to control the operation of said switch to set up a talking circuit over said two sides, said operators connection normally disconnected from said relay. 21. In a telephone system, trunks divided into groups, a switch for automatically select-i119" an idle trunk in a )redet'ermined group, means whereby an operator connects the said switch with a calling line, and a line relay individual to each switch. whereby the calling; subscriber. then controls the said switch, said relay energized over said two sides of the calling line in series, said line relay normally disconnected from said operators mean 22. In a telephone system, subscribers lines divided into groups, an automatic switch for enablil'ig a calling subscriber to find any certain line in any predetermined group, means including operator-controlled connections for extending connections from the calling line to said switch, and a line relay individual to said switch to set up a talking circuit over two sides of the calling line whereby said calling subscriber controls the said switch, said rel energized over the two sides of the calling line in eerie said line relay normally disconnected from said operators controlled connection.

In a telephone system, an automatic switch for finding: the called line, means including operator-controlled connections for extending" connections from the calling line to said switch, a line relay indi idual to said switch whereby the calling subscriberthen controls the said switch to set up a talking circuit over two sides of the calling line,

ails

said relay energizedover saidtwo sides of thecalling line in series, and means whereby the calling subscriber signals the operator for disconnection, said line relay normally disconnected from said operators controlled connection.

2%. In a telephone system, trunks divided into groups, a switch for automatically sclecting an idle trunk in a; predetermined group, a line leading to said switch, means whereby an operator connects the said line with a calling line, means whereby the calling subscriber then controls the said switch over the two sides of said first line in series to set up a talking circuit over the said two sides of the calling line, said relay normally disconnected from said operator's means, and means whereby the calling subscriber signals the operator for I disconnection.

In a telephone. system, subscribers lines divided into groups, an automatic switch for enabling a calling subscriber to find any certain line in any predetermined group, means including" operator-controlled connections for extending connections from the calling line to said switch, a line relay whereby the calling subscriber controls the said switch to set up a talking; circuit over two sides of the calling line, said relay energized over the said two sides of the calling line in series, said relay being normally disconnected from said operator-controlled connections, and means whereby the, calling subscriber signals the operator for" disconnectlOn.

26. In a telephone system. an automatic switch for finding the called line, means ineluding operator-controlled connections for extending connections from the calling line to said switch, means whereby the calling subscriber then controls the said switch over the two sides of the calling line in series, and supervisory relay mechanism whereby the called subscribersignals the operator for disconnection.

27. In a telephone system, trunks divided into groups, a switch for automatically selecting an lCllG trunlcln a predetermined group, means whereby an operator connects the said switch with a calling line, means whereby the calling subscriber then controls the said switch o her the two sides of the calling line in series, and pervisory relay mechanism whereby the called subscriber signals the ope 'ator for disconnection.

28. In a' telephone syst'm, subscribers lines divided into groups, an automatic switch for enabling a calling subscriber to find any cer ain li e in any predetermined group, means including operator-controlled connections for extending" connections from the calling line to said switch, means whereby, the calling subscriber cymtrols the said switch over the two sides oi the calling line wher by the called subscriber signals the operator for disconnection.

25). In a telephone system. a plurality of first selectors, each adapted to operate in a ':cordance with the first digit of the called number, a switch for nHiOlTlntlCtlllV selecting idle first selectors, a manual switchboard whereby an operator connects the said switch and the automatically selected idle first selector with the line ot'the calling subscriber, and means whereby the calling subscriber controls the said selector over the two sides of the calling line in series.

30. In a telephone system, an ol' erators cord circuit. an automati switch, a line relay normally diseonnecttal from said cord circuit individual to said switch for controlling the switch whereby a talking circuit may be set up'tberethrough and over conductors in the two sides of the cord circuit. and an energizing circuit for said relay which includes the said two sides of a cord circuit in series.

31. In a telephone system), a main exclninge and a branch exchange, a cord circuit at said, branch exchange i'or use in extending a connection between subscribers of said branch exchange, or between said branch exchange and said main exchange, front and back supervisory signals for said cord, and means for rendering said back supervisory signal inoperative when a call goes in from the branch exchange to the main exchange.

32. In a telephone system, a main change and a branch exchange, a, cord circuit 7 at. said branch exchange for use in txtending' connection between subscribers of said lnaneh exchange. or between said branch exchange and said main exchange, means for giving double supervision of calls when said cord is used for establishing a connection between subscribers of said branch exchange. or for extending coni'lection fi'oi'n said main exchange to said branch exchange, and means to]- giving single supervision when said cord used for extending a connection from said branch exchange to said main ex. change.

32- in a telephone systenn a main exchange and a branch exchange, a cord circuit for use in establishing a connection between subscribers of said branch exchange, or for extending a connection between said branch exchange and said main exchange, front and back supervisory signals for said cord circuit, an impulse-transmitting device, auto matic switches at the central office controlled thereby, an operators key, and means con trolled by said key for connecting the operators impulse-transmitting device with said cord, and for disconnecting one of said supervisory signals from said cord.

line circuit in series, and means .t'or

34. In a telephone system, a branch exchange and a main exchange, a cord circuit at said branch exchange, a vsupervisory relay normally bridged across said cord. :1 supervisory signal controlled by said relay, an .iperatoi"s key, an inipulse-transmitting dc- \'iee means controlled by said key for dis eonnecting said relay from said cord and for connecting said iinpulse transmitting device ith said cord to t ansmit impulses, and an automatic switch controlled by said impulses 4 35. In a telephone system, a calling and :1 called snbseribefs line, means including an operatoi"s cord circuit and an automatic switch for extending a connection between said liT1(*,S,.IllGtU1S for connecting one end of said cord with said calling subscribers line and the other end with said automatic switch. a pair of condensers in tl I two sides of said cord, thereby preventing direct con nection between said subscribers lines and said automatic switch, afikey :for short-circuiting said condensers so as to establish a direct connection between said subseribefis line and said switch. a supervisory relay, and means controlled by said key switch for rendering said supervisory relay inoperative.

36. In a telephone stem, telephones, a two-conductor line indi\idual to each telephone, a two-way trunk-line, an automatic switch allotted to one end of said trunk line for extending connection therefrom comprising a central battery common to the lines means by which a calling subscriber initially controls said switch over two sides of the ing connection to or from the other end of said trunk line.

37. To a telephone system, telephones a two-conductor line individual to each telephone, a two-way trunk line. an automatic switch allotted to one end of said trunk line for extending connection there'l'rom com,- prising a central battery eounnon to the lines, means by which a calling HllbSCl'ibGl' Q 0 initially controls said saw it over two sides of the line circuit in ser and means for extemling cormection to or from the other end of said trunk line. said switch responsive to the closure of a. bridge circuit across the trunk. line.

38. In a telephone sytem, a trunk ine tern'iinating at one end. n a manual connective terminal and )IOVldGfl at the other end with two branches, terminating, respectively, in fixed and movable contacts in numerical and non-numerical antomatic trunking switches, means including said termral and the said non-numerical switch for extending calls over said trunk line in one direction, and means including said numerical switch and said terminal for or;-

u I l tending calls over said l'lfi vine is the on posite direction.

39. In a telephone system, a trunk line terminating at one end in a spring jack, means including said-jack and ai'rautomatic switch at the other end of said trunk ine controllable thereover for extending calls over said trunk line in one-direction, and means including a second automatic switch operable to seize saidtruul: line at one end and the said jaclrat the other end of said trunk line for extending calls thereo er in the opposite direction, other automatic switches associated with said first automatic switch in a group, trunk lines at mle to said group of itches, and a master switch common to the swi l so tches oil saiu lecting an idle trunk for calls in said direction,

40, In a telephone system, a

trunk line terminating at one end in a sprin jack and "ill provided at the other end with two branches, terminating, respectii-ely, in fixed and morable contacts in numerical and non-numerical automatic trunking switches, means ineluding said jack and the saidnon-numerical switch for extending calls over said trunk line in one direct-ion, and means including said numerical swit -h and said jack for extending calls over s posite direction.

n. In a telephone system, a trunk line terminating at one end in a i'nanual connective terminal and provided at the other end with two branches, terminating, respectively, in fixed and movable COIllLilfftSilll numerical and non-nunierical automatic switches, n'reans including said said non-numerical switch over said trunk line in one trunking terminal and the "direction, means including said numc ical switch and sail terminal forcxtendin calls over said trunk line in the oppos lii action, and a circuit for making said. trunk line busy to said numerical switch whcnci'e-r the said non-numerical switch is operated. is

-12. In a telephone, am, a trust; line terminating at one end in a numual trouncetive terminal and provided at the other end wi th two branches, terminating )(T rely, in tixed and movable emit-acts in inn and n0n-numerical automatic trunking switches, means including said terminal and the said non-munerical switch for extendingcalls over said trunk line in one direction, means including said numerical switch and said terminal for extending calls over said trunk line in the opposite direction, and means including a relay for rendering said non-numerical switch inoperative whenever said trunk line is seized by said numerical switch,

in a telephone system,

a trunk line trunl' line in the opterminating at one end in a spring jack, means including said jack and an automatic switch t the other end of said trunk line controllable thereover for extending calls orer said trunk line in one direct-ion, means including a second. automatic switch to seize said trunk line at one end and the said aclr at the otl er end of said trunk line for extending calls thereover in the opposite direction, and a circuit for making said trunk line busy to *ccond switch whenever the said iiriz switch is operated, other automatic switches associated with said. first automatic switch in a group, trunk lines accessible to said group of switches, and a master switch coinn'ion to the switches ofsaid group for selecting an idle trunk for calls in said first dir ion.

in telephone systen, a trunk line erminating at one end in a spring jack, means neluding sa'd Jack and an automatic switch at the other end of said trunk line controllable thereorcr for extending calls over said trunk line in one direction, means including a second automatic switch operable to seize said trunk line at one end and the said jack at the other end cit said trunk line extendingcalls thereover in the opposite d: ection, and means for-rendering said first switch inoperative whenever said trunk line is seized. by said second switch, other automatic switches .associated with said first auton'iatic switch in a group, trunk lines accessible to said group of switches and a master switch comn'ion to the switches of said group for selecting an idle trunk for calls in said first direction. 7

ln a telephone system, a trunk line terminating at one end in a spring jack and provided at the other end with two branches, terminating, respectively, in fixed and movnhle contacts in numerical and non-nu1nerical automate trunking switches, means in claling' said jack and the said noirnumerical sw. tor extending calls over said trunk line in one dii ection, means includingsaid numerical switch and .aid jack for extendin lls over said 't-rlmi line in the opposite direction, and a circuit for making said trunk line busy to said numerical switch l never the said non-numerical switch is operated,

In a telephone systelii, a trunk line terminating at one end in. a spring jack and provided at the other end with two branches, terminating, respectively, in fixed and movable contacts in numerical and non-nun'ierical automatic trunking switches, means in cluding said jack and the said non-numerical switch for extending calls over said trunk line in one direction, means including said numerical switch and said jack for cxtendin calls over said trunk line in the opposite direction, and means including a relay for rendering said non-numerical switch inoperative whenever said trunk line is seized by said numerical switch.

7.111 a telephone system, a line circuit, a link circuit to connect therewith, a pair of condensers in said link circuit, a relay having a winding bridged around each of said condensers, a supervisory signal, means for displaying said signal when said link and line circuits are connected, and means for rendering said signal inope 'ative when said relay is energized.

48. In a telephone system. a trunk line, an ope ators call signal at. one end thereof, means, at the other end of said trunk for supplying ringing current, means whereby said signal is responsive to the tlow of ringing current over the trunk, and electrically controlled means for calling and releasing auton'iatically over circuits each oil which includes a portion of one side of the trunk line in series with a portion of the other side thereof.

4 In a telephone system, lines, numeri cal trunk selecting switches, impulse send ing means for said lines, and an operators trunk circuit in combination with non-numerical trunk selecting switching means for connecting any one of said lines with any one of said numerical trunk selectors, whereby the connected selector may be operated from the connected line.

50. In a telephone system, lines, nnmerical trunk selecting switches. an ope fators trunk circuit in combination with non-numerical trunlc selecting switching means for connecting any one of said lineswith any one of said numerical trunk selectors, and means controlled from the line for releasing the numerical switch after it has been oper ated.

in a telephone system, lines, numeri cal trunkselecting switches, impulse sending means for said lines. an operators trunk circuit in combination with non-numerical trunk selecting switching means for connecting any one of said lines with any one of said numerical trunk selectors, whereby the connected selector may be operated from the connected lines, and means controlled froin the line for releasing the numerical switch after it has been operated.

In a telephone system, lines, numerical trunk selecting switches, impulse sending means for said lines, an operatofs trunk circuit in ombination with nonannnerieal trunk selecting switching means for connecting any one of said lines with any one of said numerical trunk selectors, whereby the connected selector may be operated from. the connected line, and signal devices connected with the manual portion of the apparatus to indicate to an operator the ne essity tor con nection and disconnection.

53. In a telephone system, lines. numeriial trunk selecting switches. an operators trunk circuit in combination with non-nuincrical trunk selecting switching means {or connecting any one of said lines with any one of said i'iumerical trunk selectors. means controlled from the line for releasing the numerical, switch after it has been operated, and signal devices connected with the manual portion of the ai'iparatus to indicate to an operator the necessity for connection and discoi'mection.

54. In a. telephone system, lines, numerical trunk selecting, switches, impulse sending means for said lines, an operators trunk circuitin combination with non-nlnnerical trunk selecting switching means for connecting any one of said lillcs with any one of said numerical trunk selectors. where y the connected selector may be operated from the comiectcd line, means controlhal from the line for releasing the numerical switch alter it has been operated, and signaling devices connected with the manual portion ol' the apparatus to indicate to an operator the ne-- cessity for connection and disconnection.

55. In a telephone system, lines, nmnc ical trunk selecting switches, impulse sending means for ::id lines. and an operators trunk circuit in combination with non-nunierical trunk selecting switching means for connecting any one of said lines with any one of said nnmericail trunk selectors, whereby the connected selector may be operated from the connected line to establish a talkin circuit from. the connected line to aliothcr line.

so. In a telephone system, lines, numerical trunk selecting switches, impulse sending means for said lines, an operators trunk circnit in combination with non -numerical trunk seltartin; switching means for connecting any one of said lines with. any one of said numerical trunk selectors, whereby the connected selector may be. inicrated from the connected line to establish a talking circuit from the connected line to another line. and means controlled from the comn-ctcd line for releasingthe numerical switch alter it has been operated.

57. In a telephom system. lines. ll'dllltflh cal trunk selecting switches. impulse Stlltling means for said lines, an operators trunk circuit in con'ibiinition with non-numerical trunk selecting switching means for connecting any one of said lines with any one ot said numerical trunk selectors, whereby the connected selector may be ope ated from the connected line to establish a talking circuit from the connected-line to another line, the connected selector being controlled over two sides of the talking circuit in series.

52v. In a telephone system, lines, numerical trunk selecting switches, impulse sending 10 releasing the numerical switch ing means for said lines, an operators trunk circuit in combination With non-numerical trunkselecting switching means for connectany one of said lines with any one of said numerical trunkselectors, whereby the connected selector may be operated from the connected line, to establish a talking circuit from the connected line to another line, and means controlled from the-connected line for after it has ARTHUR B. SPERRY.

county,

Witnesses:

ETHEL A. EDGELL, EDWARD D. FALns.

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