US1379017A - Semi-automatic telephone system - Google Patents

Description

-G. A. YANOQ'V,HOWSKI ANU H. E. HERSHEY.

v SEMI-AUTUMATIC TELEPHONE SYSTEM.

Awuclmon man v3.21. 191e.

1,379,017. Patented May24,1921.

` 2 SHEETS-SHEE'T-l.

G. A. YANOCHOWSKI AND H. E. HERSHEY. 'SEMI-AUi-MAHCVTELEPHONE SYS'TM. v APFUCTON FILED FEB. 2 2 915 1,379,01 7.. Patented May 24, 1921.

2 SHEETS-SHEET 2.

7 TTORWEY UNITED sTArEsff "PATENT OFFICE.

GEORGE A. *I'ANOCHOWSRLl OE CHICAGO, ILLINOIS, ANL HARRY E; HERSHEY, OE WHITEWATER, KANSAS, AssIGNORs To AUToivi-ATIC ELECTRIC COMPANY, `or CHICAGO, ILLINOIS, A CORPORATION OE ILLINOIS.V l l f SEMI-AUTOMATIC TELEPHONE SYSTEM.

sas, have invented certain new and useful Improvements in Semi-Automatic"v Tele-` phone Systems, of which the following is a specification. A ,K

,Our invention relates to semi-automatic telephone systems in general, but has particular reference `to the means for 'indicat ing to an operator in such a system that a called lineis busy. More specifically, our invention rela-tes to the provision of super-` visory signals associated with y operators cord Circuits and to the method ofl control-V ling said signals when connection is attempted with albiisy line. i

Heretofore various means have been employed for controlling such a signal, but to the best of our present knowledoe, all pre-A vious systems employ specialrmeans asso-v ciated with the connector switches for con# trolling the signal in the operators cord Circuit. Or, at any rate, the connector switch used in theV unsuccessful call Vis instrumental in some way in effecting the continued actuation Yof the signal, and is, therefore` tied up and cannot be used for other connections until released 'by some act of an Operator.

In our improved system we employ a connector switch which releases when an attempt is made to connect with a busy line and which, before so doing, initiates an operation at the operators cord circuit whereby the busyflash signal is controlled, anda busy tone is transmitted to the calling subscriber. L

kThe principal object of our invention is the provision of means .whereby the foregoing is accomplished independently of the automatic switches, eXceat for'the initial operation above mentioned, and whereby,v

after their release, the automatic switches are made accessible for use in other connections. l Y y Further Objects relate to the provisionof certain details of'circuit improvement tending to increase the generalpetliciency and Specification of Letters Patent. i

' Application filed February 21,1916. Serial No. 179,662.

'into a bank of Contact Patented May serviceability .of a telephone exchange sys`V tem of this character. y

To accomplish theforegoing and other useful ends our invention comprises means which will -be hereinafter fully explained,I

reference being had to the accompanying drawings, in which Figures 1 and 2, taken in order with the lines at the ends thereof .in aliiiement..represent a complete circuitV connection between a' calling substation A and a called substation A in a system embodying the principles of our invention. The said connection has been established through theV medium of the individual 'line p n switch C, answering jack J,'cord circuit F, multiple jack J', line switch C2, `and con nector K n y Referring now to Fig. 1, the substation A may be of anypsuitable or approved type, and, as herein represented, vcomprises the usual receiver 9, transmitter 10, ringerll', and condenser V12. y

The substation A thefsubstation A..

The subscribers individual switch C (Fig. 1) isV of the general type of subscribers switch shown in British patentto B. W. James No. 26,301 of 1906; being,"how ever,'of the particular type disclosed in British patent to T. Gr. Martin, No. 1419 of 1910; This line switch ycomprises among other details, a plunger (notshown) at# tached to the endof a so-calledplungeivarin l'which iscontrolled by the magnet 14e. The magnetlt, comprises Vfour windings, namely,1a pulldown winding 15,y cut-off 'or holding winding 16".V lliner winding 17 and an auxiliary winding' 1S.. The core of the magnet 14 is so constructed that theV magnetic circuit of the windings 15 and 16 fis separate from that of the windings 17 and 1S.'n This magnet also controls the cut-off armature 19. The pull-in winding 15 operates both (ing. sie Simian i@ while Vthe cut-off or holding winding 1G. is

strong enough only to operate the cutoii" armature 19 and to hold the plunger arm 13 in its operated position. ,Vhen the plunger arm 13 isioperateththe plunger is forced p springs, forcing the springs 20, 21, 2.2, and 28 into engagement ywith the springs 2e, 25,96, and 27, `respectively@ `Although only one set .of springs (20 to 27) is shown, each line switch is provided with a plurality of such sets, each set forming the terminal of a trunk line leading to an answering jack. Each trunk line is connected in multiple with the corresponding springs of all the line switches of the group which is controlled by the master switch D. The switch C is controlled by the subscriber through the medium of the line winding 17, as will hereinafter be more fully explained.

The line switches C and G2 are of the same type as the switch C.

The master switch D (F ig. 1) is of the same general type as that disclosed in British patent to R. W. James No. 26,301 of 1906; being, however, of the particular type disclosed in British patent to T. G. Martin No. 1419 of 1910. The function of the master switch, as is well known, is to maintain the plungers of all the idle line switches in position to engage the terminals of an idle trunk line. y,

The answering jack equipment E consists ot the usual line relay 28, cut-ofi' relay29, line lamp and answering ack J.

The cord circuit F is of a well known type and comprises the usual answering and calling plugs P and Pf, inductively connected through the medium of the condensers 31 and B2. The lamps 33 and 34 are the usual supervisory lamps. The relay 35, is a polarized relay. The key K is a listening key for .connectin` the o erators talkin@ set not C! 2D shown) with the cord circuit. The key K is a calling device key, the purpose of which is to connect the calling device 78 withl the cord circuit, through the medium of which the operator may control the automatic switches to setup the proper connection. This calling device may be of any desired type, such, for instance, as that shown in British patent to S. G. S. Dicker No. 29,654-

o't 1910. By suitable manipulations of the dial the operator `may interrupt the bridge across the trunk line a number of times corresponding to each of the digits of the number of the called subscriber.

The connector switch H (Fig. 2) is of the same general type of connector switch as disclosed in United States Letters Patent No. 815,176 granted March 13, 1906, to Keith, Erickson and Erickson; the circuits, however, being modiiied to adapt the switch to operate in a system in whichthe central oiice apparatus is controlled by impulses delivered over the two sides of the line in series. Among other details the connector H comprises a bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of wipers 36, 37, and 38 carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 39 and a rotary movement controlled by the rotary magnet 40.

The usual side switch comprising the wipers 41, 42, 43, and 44 is controlled by the private magnet 45 `in the usual and well known manner. The operations of various'parts el the switch are controlled through the medium of the double-wound relay 46, said relay being connected with the line through the reversing springs of a so-called back bridge relay 47, through the windings of which latter relay the called line is provided with talking current. The ringer relay 48 affords means by which ringing current is applied to the called line. Means for permitting the switch to be restored to normal position are provided in the release magnet 49, which, upon energizing, withdraws the retaining doubledog from the shaft, thereby permitting the shaft and wipers to be restored to their normal position. The springs 50 and 51 close only when the switch shaft has been raised one or more steps from its lowest position. The relays 52 and 53 are slow acting, that is, slow to release their armatures upon deenergizing.

For the purpose of supplying battery current for operating the apparatus and for talking purposes, 'there is shown the battery B having one terminal grounded at G. For the purpose of supplying ringing current there is shown the ringing `current generator R. The busy signaling machine Q, as represented herein, comprises an induction coil or transformer, the primary winding of which is included in a local circuit with a battery and an interrupting device. 10o Through the medium of this interrupting device, an interrupted current is supplied to the primary winding, thereby inducing an intermittent alternating current in the secondary winding, whereby, when saidwind- 105 ing is connected with the subscribers line, a' buzzing sound is heard in the receiver.

A general description 01 the apparatus having been given, it will now be explained how a connection is established between'a 110 calling substation A and a called substation A. It will also be explained how, if the called substation is busy, all vof the automatic switches controlled by the operator v in setting up a connection are automatically released and returned to normal position, while the calling subscriber is receiving the busy signal, which is in this case applied to the calling line at the cord circuit. In addition it will be shown how the called supervisory. lamp is caused to flash, thus informing the operator that the number called is busy. It will be assumed that the number of the called substation is 22. Since the apparatus disclosed herein is in general well known in the art, and is described in the publications herein referred to, its operation will be Vexplained in a more or less general manner.

When the subscriber at substation A re- 56, through substation A, conductor 57,k

springs 58 and 59 and the line winding 17 to battery B. The armature'GO, is thereby operated and closes' a circuit vfrom ground G1 through springs 54 and 61, pull-in winding 15, auxiliary winding 18 andthe springs 62 to battery Bf The pull-in winding 15, upon energizing, attracts both the armature 19 and the plunger arm 13. The plunger arm, upon being attracted, forces the plunger which is attached to the end thereoil into the bank of trunk terminals to which it has access,forcing the springs 20, 21, 22, and 23 into engagement with springs 24, 25, 26, and 27, respectively. The engagement of springs 20 and 23 with springs 24 and 27, respectively, closes a circuit through the line relay 28 associated with the answering jack E. This circuit extends from ground G2 through springs 63 and 64, springs 24 and 20, conductor 57, to and through substation A, conductor 56, bank springs 23 and 27, springs 6 5 and 66, and the relay 28 to battery B.

The energization cf relay 28 closes a circuit extending from ygroundG3,V through springs 67, bank springs 25 and 2-1, to the point 68, whence one branch extends over conductor 69 to' the connector private bank contact associated with the calling line, and multiples of the same. Another branch extendsjfroin the point 68 through the holding winding 16o-f line switch C to battery B. This circuit through'the holding winding 16 is closed before the armature 60 falls back, after the circuit k through the line winding 17 is broken bythe attraction of the armature 19. The armature does not fall back immediately upon the pullingV of armature 60 isturther retarded by the short circuitiiig of winding 18 at springs 70, thereby introducing the well known slow action. Thus the armature- 60 1s held in an operated position untilenough tinievhas ela )sed ior the circuit throughthe winding d ,C

, 16 to be closed;y whereby the plunger arm 13is held in an operated position.. A

A further result of the `energization of relay 28'is` the closure of a circuit'through the line lamp 30. This circuit extendsjfrom l ground ,G3 through contacts of springs 67,

said line lamp 30 tobattery B, thus causing troni the plug seat switch 71 andv inserts Upon the complete said plug in jack J. When the plug is removed rom the plug seat 71, a circuit is closed from the ground G4 through plug seat switch 71, lainp 33, and the springs 72 to battery B. Upon the insertion of plug P in jack J a circuit is closed extending from ground G5 through resistance 73, sleeve of plug P, sleeve of jack J and the cut-off relay 29 to battery B. The'V cut-ofi relay 29, upon energizing, cuts 0Hl the line relay 28 and extends the connection to the cord circuit F, and since the springs 75a of said relay are adjusted to make contact before springs 67 of relay 28 break from their con- Y tacts, the ground G2 now afl'ords a holding circuit for the winding 16 of line switch C to take the place of ground G3 which will 'beremoved upon the denergization of relay 28. The circuit for the new holding ground extends from ground G2 through contacts of springs 75a, bank contacts 25 and 21, and liold-in winding 16 to battery B. When the connection is extended to the cord circuit F a circuit is closed extending `from groundV GG through coil 74, tip of plug P, tip spring of jack J, springs 75 and V64, toy and through Vsubstation A over a circuit previously traced, springs 65 and 76, ring spring of jackJ, ring of plug P, and the relay 77 to battery B. The relay 77, upon energizing, opens the circuit of lamp 33 previously referred to. The operator nowoperates the key Kand converses withthe callingjsubscriber. Upon learning the desired number, she operates thekey` K, thereby separatinor the answering andcalling ends Vofthe cord circuit and bridging the calling device 78 across the calling end, and then inserts the plug P in an idle outgoing trunk 'ack J Upon the insertion of the plug into the jack J `and due to the fact that the calling device 78 is bridgedacross the line conductors of thecord circuit an energizing circuit for the line winding 'of the switch Cla is closed.l The line winding of the switch C2, upon energizing, causes` said switch C? to` VVdraw in its plunger-arm 95 in the saine man# ner as was described regarding'line switch to thereby extend the connection tothe line relay 46 of the connector H. AV cir' cuit niay now be traced `from ground ,G7

through lower winding of relay 46, springs 79 and 80, springs 119, bank springs 81V and 82, conductor 83, ring spring of jack J ,'ring cit'plug P', springs 84,`contact of keyK,

calling device 78,co'ntact of key K', relay k85, `tip or" plug P, tip springV of jack J ,'conduct-or 86, springs 87 and 88, springs 89 and 90, and the upper'windingof relayg-46 to batterylB. The line relay 46, upon fenerf, wizing,.closes acircuit through the relay 52. This, circuit extends from ground GB-through contacts of springs 99 and V99a and relay 52 te battery B. The relay 52 kin-turn,v upon energizing, closesacircuit from ground G through springs 91, springs 92 and 93, and the holding winding 94 to battery B. The holding winding 94, energizes over this cirn cuit and operates it to hold the plunger arm 95 in an operated position.V lt will have been noticed that the energizing circuit of the line winding of the line switch C2 and the later described circuit of the line relay 4G, both included the relay 85 in the cord circuit F. The jack J is so adjusted, that when the plug P is inserted, the tip and ring of plug and jack malte Contact before the springs 96 are closed. 1n this way the relay S5 will be energized and open the circuit of relay 97, at the springs 93, before the circuit of said relay is completed at springs 90.

The operator now operates her calling device for the first digit of the called number, whereby the calling device impulse springs are scparatedtwice momentarily, each time breaking the circuit of the line relay 46 of the connector H. The relay 52 of the connector being slow acting, does not deners during the momentary interruptions of its circuit by the relay 46, and consequently eac-h time the latter relay denergizes, an impulse lis transmitted over the circuit eX- tending from ground G9 through springs 99 and 100, springs 101 and 102, relay 53, vertical vmagnet 39, and the side switch wiper 41 (in first position) to battery vB. The vertical magnet receives two impulses over this circuit and operates to raise the switch shaft and wipers two steps to a position opposite the second row or level of bank contacts, and at the same time the shaft controlled springs 50 and 51 are closed. The slow acting relay 53 is maintained in its energized position continuously while impulses are being transmitted to the vertical magnet through it, and in its energized position, closes a circuit from ground G1 through springs 103 vand104, and the private magnet 45, to battery B. This circuit is broken when the `relay 53 denergizes after the last impulse has been delivered to the vertical magnet, the breaking of said circuit causing the private magnet 45 to deenergize, thus permitting the side switch to pass tok second position. 1n passing from first to second position, the side switch wiper 41 transfers the battery connection from the vertical magnet 39 to the rotarv magnet 40.

The operator now operates the calling device for the last digit 2, in response to which the connector line relay operates to transmit two impulses through thek rotary magnet 40, whereby the shaft wipers are rotated onto the contacts of the desired line. The circuit through the rotary magnet eX- tends from ground G9 through springs 99 and 100, springs 101 and 102,relay 53, rotary magnet 40, and the side switch wiper 41 (in second position) to battery B. The relay 53 operates in response to this digit in the same manner as for the previous digit, t0 cause the private magnet 45 to advance the side switch to third position.l By the engagement of side switch wipers 42 and 43 with their third position contact points, the line connection is completed with the called line. Upon the engagement of side switch wiper 44 with its third position contact point, a circuit is completed through the cut-off winding 107 of the line switch C', which upon energizing, disconnects the line relay from the called line. The connection of ground G11 with the connector private bank contact associated with the called line, prevents the called line from being seized by some other connector switch. By the engagement of side switch wiper 41 with its third position contact point, the circuit of the ringer relay 48 is closed. This circuit extends from ground G11 through interrupter 108, ringer relay 48, springs 109, and the side switch wiper 41 (in third position) to battery B. The ringer relay is energized intermittently due to the interrupter 108, and operates to disconnect the calling line from the called line, and to bridge the ringing current generator R across the called line to signal the called subscriber. Upon the response of the called subscriber, his line is provided with talking current through the windings of the back bridge relay 47, which relay, upon energizing, closes the circuit through the ringer cut-off relay 110. The said circuit extends from ground G11 through side switch wiper 44 (in third position) springs 111 and the relay 110 to battery B. The relay 110, upon energizing opens the circuit of the ringer relayA 48 at the springs 109, and closes a locking circuit for itself, through the springs 112 independent of springs 111. This circuit extends from ground G11 through side-switch Wiper 44 (in third position), contacts of springs 112, and relay 110 to battery B. Furthermore, the back bridge relay 47, upon energizing, operates to reverse the direction of the orw of current in the trunk, with a result hereinafter described.

11i7hen the operator has completed dialin@r the called number, she restores the key to normal thereby againconnecting the answering and calling ends of the cord circuit and at the same time opening the bridge consisting of the calling device (8. It will be observed that the polarized relay 35 is now bridgedV across the' trunk in place of the bridge consisting of the calling device 78. The polarized relay 35 will become energized in a direction to close a circuit through lamp34; the glowing oflamp 34 will inform the ,operator that the called subscriber has not answered. Upon the called subscriber removing his receiver, the baclr bridge relay operates to reverse the flow of current in the trunk as previously.Y

out the transmission of the impulses.

Upon the completion of the conversation, the hanging up of the receiverat the calling substation opens the circuit of relay 77, which, upon cle-energizing, closes the circuit of lamp 33. lhe'hanging up of the receiver at the called substation opens the circuit of the back bridge relay 47, which, upon denergizing, again reverses thekcurrentin the trunk to such a direction that the polarized relay 35 again closes the circuit of the lamp 34. rllhe operator, upon seeing both the lamps 33 and 34 glowing, knows that a disconnect is required and thereupon removes the plugs P and P from their respective jacks. The removal of plug P opens the circuit Aof the cut-ofi'1 relay 29, which, upon denergizing, opens the circuit of the holding winding 1,6. Upon the deenergization of the holding winding 16, the plunger arm 13 is released and the line switch C thereupon returns to normal. T he removal of the plug l opensv the circuit of the line relay 46 of the connector H. rIhe denergization of relay 456 opens the circuit of relay 52, which in turn, upon deenergizing, closes a circuit extending from ground G through springs 99 and 100, springs 101 and '113, off normal springs 50, and the release magnet 49 to battery B. The release magnet, upon energizing, operates to restore the side switch wipers to their first position and to remove the retaining double-dog from the shaft, thus allowing the shaft to drop to its normal position, and its own circuit is opened at the springs 50 when said shaft reaches its lowest positionr In addition, the denergization of relay 52 opens the circuit of the holding winding of the line switch )2, whereupon line' switch C2 releases in the same manner as explained in connection with line switch C.

It having been explained how one subscriber obtains connection and the same is released` it will now be explained how a connection is prevented from being made with a busy line. If the called number is busy there will be a guarding grund potential upon the connector private bank contacts, associated with that line, just as explained in connection with the line switch C. When, therefore, the slow acting relay V53 de'e'nergizcs at the end of the last series ofv impulses, a circuit is completed for the busy test relay 114 and the privato magnet 45 over the following path :v ground at the privateV bank Contact, ,private Wper, sideswth Wiper 44 (in second position) springs 115 and 116, relay 171.4, springs 117 and 104, and the private magnet 45 to battery B. rlhe relay 114, upon energizing7 forms a locking circuit for itself extending from ground (x13 through olf normal springs 51, springs 118 and 116; relay 114, springs 117 and A104, andthe private magnet 45 to battery B. In addition, the relay 114, upon energizing, separates the springs 119, thereby opening thecircuit of the line relay 46 and the relay 85, of cord circuit F, in series therewith. As a result of the denergization of the line relay 46 the circuit of relay 52 is broken` whereupon the Vrelease 0f the connector H and the line switch C2 takes place as previously explained. It should be mentioned in this connection that Vwhile relays 85 and '52 areY both sufficiently slow acting to retain their armature during impulses, the latter relay should be somewhat the slower of the two. Furthermore, since the circuit of relay 85 is interrupted slightly before that of relay 52 is interrupted, it follows that soon after the -opening of thercircuit of the line relay 46, and before the denergization of relay 52, the slow acting relay denergizes and .closes a circuit extending from ground G14,

through springs 96, sleeve of jack J', sleeve of plug P', relay 97, and the springs 98 to battery B. The relay 97, upon energizing, completes a circuit extending from ground G15 through springs 120 vand the relay 121Y Vto battery The relay 121, upon energizing, forms a locking circuit for itself from ground G4 through plug seat springs 71, springs 122, and the relay 121 to battery-B, and at the same time, by separating springs 84, opens the original energizing circuit for the line winding of line switch G2 so that the automatic switches upon their complete restoration to normal will not again be operated.k After the calling device has been operated the operator restoreskey K to its normal position thereby completing the circuit over the heavy conductors to the calling line and disconnecting the calling device. The polarized relay 35 being at this time in open circuit, its armature will be held in the direction to keep the circuit of lamp 34 open. In addition a circuit is closed from ground Gwthrough interrupter 123, springs 124, and the lamp 34, to battery B. The lamp will be. flashed intermittently, due to the interrupter 123 and this informs the operator that Athe line called is busy.

Furthermore, and at the same time, a cirf cuit is closed from the secondary winding of busy machine Q, springs 125. condenser 32, over heavy conductors to and through substation A, relay 74 to l`ground G6 and return to busy machine The calling subscriber upon hearing the busy tone will restore his receiver to the switch hook, thus giving the operator the disconnect signal as previously explained. The operator, upon observing the hashing ot the lamp 34, is thereby informed that the called line is busy and, provided the calling subscriber has already hung up his receiver, she may remove the plugs from the jacks. In case, however, the calling subscriber has not hung `up his receiver or does not understand the significance of the signal he receives, the operator may throw hey keys K and K and is then able to inform the subscriber' of the inaccessibility of the desired line.

it will be seen that during the entire busy signaling operation above described the connector l-l is entirely free and is accessible to other line switches such as C2. It may, in tact, be seized and used tor establishing a new connection immediately after its restoration to normal.

While we have described in the foregoing a certain specific embodiment of our invention, we do not wish to be held strictly lto the exact form shown herein, for various adaptations will no doubt suggest themselves to persons skilled in the art. We desire, therefore, to include and have protected by Letters Patent all forms and modifications ot cui1 invention which may come within the scope of the appended claims.

llhat we claim is:

l. ln a trunlring system, a line, a plurality oi automatic switches having access to said line, means for operatingv any one ot said switches to iind the line, means .tor releasing whichever switch is so operated, an equipment including a pair or signaling circuits, a signal for cach ot said circuits. means associated with said equipment ifor applying signaling current to said circuits, means 'tor applying said equipment to any one o? said switches whereby, when the line is ifouni'l and the switch relerses. said means associated with said equipment is controlled to simultaneoufly operate said signal'.

ln a truuking system, a liuc. a plurality ot automatic switches having access to said liuc, means for operating anv one ot sai/l switches to rind the line, means ior releasing whichever switch is so operated, an ecuipment includingv pair of signaling circu s, a signal individual to one ot said circuits and a plurality ot' signals associated with the other circuit, means for connecting said other circuit. with any one ot its associated signals, means associated with said equipment for applying signaling current to said circuits, means `for applying said equipment to one ot said switches whereby, when the line is found and the switch releases, said means associated with said equipmentis controlled to simultaneously operate said signals. l

3. ln a trunlring system, a line, a plurelitv' of automatic switches having access to said*- line, means for operating any one of said switches to iind the line, means for releasing whichever switch is so operated, an equipment including a pair of signaling circuits, a signal for each of said circuits, means associated with said equipment for applying signaling current to said circuits, semi-automatic means Vior applying said equipment to any one of said switches whereby, when the line is found and the switch releases, said means associated with said equipment is controlled to simultaneously operate said signals.

4V. ln a trunking system, a line, a plurality of automatic switches having access to said line, means for operating any one of said switchesto lind the line, means for releasing whichever switch is so operated, an equipment including a pair of signaling circuits, a signal tor each of said circuits, means associated with said equipment for applying signaling current to said circuits, semi-automatic means including a second automatic switch for applyingl said equipment to any one ot said switches whereby, when the line is found and the switch releases, said means associated with said equipment is controlled to simultaneously operate said signals.

5. In a trunlin g system, a line, a plurality ot automatic switches having access to said line, means for operating any one ot said switches to find the line, means for releasing whichever switch is so operated, an equipment including a. pair of signaling circuits, a signal individual to one of said circuits and a plu 'ality or" signals associated with the other circuit, means for connecting said other circuit with any one ot its associated signals, means associated with said equipment for applying signaling current to said circuits, means for applying said equipment to any one ot' said switches whereby when the line is found .and the switch releases, said means associated with said equipment is controlled to simultaneously operate said individual signal and one oi'4 said other signals.

6. In a trucking system, a line, a plurality of automatic switches having access to said line, means for operating any one ct said switches to lind the line, means for releasing whichever switch is so operated` an equipment incliuliim` a pair ot' signalin circuits, a signal for each ol said circuits, means associated with said equipment forapplying signaling current to said circuits, semiautomat-ic means comprising a second automatic switch for applying said equipment tov any oneoii said switches whereby, when the line is found and the switch releases. said means-associated with said equipment is controlled to simultaneously operate said signals, and said second switch is released 7. In a trunking. system, a line, a plurality line, means for operating any one of said switches to iind the line, means for releasing whichever switch is so operated, an equipment including'a pair ofsignaling circuits, a signal for each of said circuits, means associated with said equipment for applying signaling current to said circuits, means `for applying said equipment to any one of said switches whereby, when the line is found and the switch releases, said means associated i withsaid equipment is controlled to simultaiieously operate said signals, and an inter- Yrupter for one ofl said signaling circuits .to

render the associated signal intermittent. Y

8. In a telephone system, a plurality of lines, a plurality of cord circuits, an automatic switch having `access to said-lines, means whereby a connection may be established between a calling and a called line through the medium of any one of said cord circuits andsaid switch, a signal associated with each ofV said cord circuits, means whereby upon the attempt to complete a connection with a busy line said switch is released, and means included in the selected cord cir- Vcuit 'and made effective upon the release of said switch, whereby said switch is rendered accessible to the remainder of said cord circuits, and whereby the signal associated'with the selected cord circuit is operated.

9L In Va ,telephone system, a plurality of lines, a pluralityof cord circuits, a plurality of automatic switches having access to said lines, means whereby a connection may be lestablished between a calling and a called line through the medium of any one of said cord circuits and a yselected one of said switches, a signal associated with each of said cord circuits, means whereby upon thel lines, a cord circuit, an automatic vswitch having access to said lines', means ywhereby a connection may be established between a calling and a called line through the medium of said cord circuit and said switch, a signal associated with said cord circuit, ka circuit for said signal, means whereby upon the completion of a connection to a busy line said switch is released,'means included in said cord circuit and rendered efiective upon the release of said switch for closing the circuit ofsaid signal, and an interrupter in said circuit for making the operation of said signal intermittent in character.

11. In a telephone system, a plurality of lines, a plurality of cord circuits,l an automatic switch having access tosaid lines, means whereby a connection may be established between a calling and a called -line through the medium of any one of said cord circuits and said switch, a signal associated with each of said cord circuits, means whereby upon the completion ofv a connec-` tion to a busy line said switch is released, means included in the selected cord circuit and made effective upon the release of said switch, whereby said switch is rendered accessible tothe remainder of said cord circuits, and whereby the associated signal of the selected cord circuitj is operated; and means for making the operation of said sig nal intermittent in character. f `f l2. Inv a telephone systema pluralityof lines, a cord circuit,'-a plurality of autoinaticswitches havingaccess to saidlines,

means whereby a connection may be established between a calling and a called line through the medium of said cord circuitv and a selected one of' said switches, a signalfassoci ated with said cord' circuit, a-circuit for said signal, means whereby upon the-completion of a connection to a busy line the se? lected switch is released, means included' in vsaid cord circuit and rendered effective upon thev release of saidswitch for closing the circuit of' said signal, yand an interrupterin said circuit for making the operation of said ysignal intermittent in character.

' 13. In a telephone system, a plurality of lines, a plurality of cord circuits, a plurality of automatic switches having access to said lines, means whereby a connection maybe established between a callingy andav called line through the medium of any one of said cord circuits and a selected one of said switches, a signal associated with each of said 'cord circuits, means whereby upon the completion of a connection yto a busy line the selected switch ris released, means included in the selected cord circuit and made effective upon `the release of said switch, whereby said switch" is rendered accessible tov the remainder of said cord circuits and whereby the associated signal of the `selected cord circuitV is operated, and associated means for making the operationof. said signal intermittent in character. f

14., Ina telephone jsystem, a plrality of lines, a cordlcircuit, an automatic switch having `access to said lines, meanslwhereby a connection may be established between a calling and a called line through the medium of said cord circuit and said switch, asigna-'l associated with said cord circuit, a

circuit `for saidsignahmeans whereby upon the completion of a connection to a busy line said switch is released, means included in said cord circuit and made "effective upon the. releaseof lsaid switch "for closing the circuit of said signal, and associated means for transmitting a distinctive tone to the iso` calling line, said last means also controlled by the means included in said cord circuit.

15. In a' telephone system, a plurality of lines, a plurality of cord circuits, an automatic switch having access to said lines, means whereby a connection may be established between a calling and a called line through the medium of any one of said cord circuits and said switch, a signal associated with each` of said cord circuits, means where,g by upon the completion of a connection to a busy line said switchis released, means included in the selected cord circuit and made effective upon the release of said switch, whereby said` switch is rendered accessible to the remainder of said cord circuits and whereby the signal associated with the selected` cord circuit is operated, and associated means for transmittinga distinctive tone to the calling line. l A

16. In a telephone system, a plurality of lines, a cord circuit, a plurality of automatic switches having access to vsaid lines, means whereby a connection may be established between a calling' anda called line through the medium of said cordcircuit and a selected one of said switches, a signal associated with said cord circuit, a circuit for saidsignal, means whereby upon the completion of a connectionto a'busy line the selected switch is released, means included in said cord circuit and made effective upon the release of said switch for closing the circuitjof, said signal, and associated means for transmitting a distinctive `tone vto the calling line, said last means also controlled by the means included in said `cord circuit.

17. In a telephone system, a plurality of lines, a plurality of cord circuits, a plurality of automatic switches having access to said lines, means whereby a connection may be established between. a calling and a called line through the medium `of any one of said cord circuits and a selected one of said switches, a signal associated with each of said cord circuits, means whereby upon the completion of a connection to a busy line the' selected switch is releasedmeans included in the selectedcord circuit and made effective upon the release of said switch, whereby said switch is rendered accessible to the remainder `of said cord circuits, and whereby the associated signal of the selected cord circuit is operated, and4 associated means for transmitting a distinctive tone to the calling line. t y f A i 18. In a trunking system, anv automatic switch, 'an operating circuit therefor, said operating circuit having a terminal connection, a plurality of extensions having access infcommon to said connection, a line accessible to said switch, a busy test circuit for said line, means controlled over said test circuit for controlling said operating circuit, a relay in each of said extensions,

and a controlling relay for each of said extensions under the control of said first relay.

19. In a trunking system, an automatic u Acircuit for controlling said operating cir cuit, a relay in each of said extensions, a controlling relay for each of said extensions under the control of said first relay, a signal and la circuit therefor controlled by sald controlling relay.`

I20. In a trunking system, an automatic switch, an operating circuit therefor, said operating circuit having a terminal connection, a plurality of extensions having access in common to said connection, a line accessible to4 said switch,fa busy test circuit for vsaid line, means controlled over said test circuit for controlling said operating circuit, a relay in each of said extensions, a controlling relay for each of said extensions under the control of said first relay, a signal and a circuit therefor controlled by said controlling relay, andmeans for intermittently interrupting the circuit of said signal.

21. In, a trunking system, an automatic switch, an operating circuit therefor, said operating circuit having a terminal vconnection, a plurality of extensions having access in common to said branch, a line accessible to said switch, a busyftest circuit for said line, means controlled over said test circuit for controlling said operating circuit, a relay in each of said extensions, a controlling relay for each of said extensions under the control of said first relay, and a plurality of signaling circuits controlled by said controlling relay. y

22. `In a trunking system, an automatic switch,an -operating circuit therefor, said operating circuit having a terminal connection, a plurality of extensionsihaving access in common to said connection, a line accessibletohsaid switch, a 4busy test circuit for said line, means controlled over said test circuit .for controlling said 4operating circuit, a relay in each of said extensions, a controllingrelay for each of said extensions underthe control of said first relay, a plurality of signaling vcircuits controlled by said controlling relay, and means for intermittently interrupting one ofsaid signaling circuits.` Y A A23). lIn a telephone system, aline, a pluralityof trunk lines, an automatic switch Vhaving access to said line and normally accessible from each of said trunk lines, means `including Vone of a plurality ofV cord circuits whereby an operating circuit for said switch may be established over one of said trunk lines, a relay in said cord circuit for r controlling said operating circuit, and means effective when said switch is operated to connect with said line in its busy condition for restoring said switch to its normal condition and for initially` operating said relay.

24. In a telephone system, a line, a plurality of trunk lines, an automatic switch having access to saidline and normally ac-v cessible from each of said trunk lines, means including one of a plurality of cord circuits whereby an operating circuit for said switch may be established over one of said trunk lines, a relay in said cord circuit for controlling said operating circuit, means effective when said switch is operated to connect with said line in its busy condition for restoring said switch to its normal condition andfor initially operating said relay, and

i means for maintaining said relay in operated position whereby a new operating circuitv for said switch maybe established by means of another of said cord circuits and another of said trunk lines.

25. Ina telephone system, a line, a plurality of trunk lines, an automatic switch having access to said line and normally accessible from each of said trunk lines, means including one of a plurality of cord circuits whereby an operating circuit `for said switch may be established over one of said trunk lines, a relay in said cord circuit for controllingsaid operating circuit,fmeans effective when said switch is voperated to connect with said line vin its busy condition for. re-

V'stoi-ing said switch to its normal'condition and for initially operating said relay, and a signal controlled by said relay.

26. In a telephone system, a line, a plurality of trunk lines, an automatic switchV having access-to said line and normallyaccessible from each of said trunk lines, means including one of a plurality of cord circuits whereby an operating circuit for said switch may be established over one of said trunk lines, a relay in said cord circuit for controlling said operating circuit, means 4effective when said switch is operated to-connect with said line in itsbusy condition for rei storing said switch to its normal condition and 'for initially operating said relay, means Yfor maintaining said relay in operated position whereby a new operating circuit for said switch may be established by means of another of said cord circuits and another of said trunk lines, and a signalfcontrolled by said relay.

27. In a telephone system, a calling and a called line, a cord circuit and an automatic switch for connecting the two lines, a supervisory signal in said oo rd circuit under the control of the called line after connection therewith has been established, means effective when said called line is busy for preventing connection thereto and for releasing said switch, auxiliary controlling means in said cord circuit kfor saidy signal initially operated through the medium of said first means, means for securing the continued if operation of said auxiliary controlling means until the disconnection of said calling line independent of said switch. i

28.' In a telephonesystem, a calling and a called line, a cord circuit and an automatic switch for connectingthe two lines, a supervisory signal in said cord circuit under the control of the called line after connection therewith has been established, means efl'ective when said called line is busy for'fpreventing connection thereto and for releasing said switch, auxiliary controlling means in said cord circuit for said signal initiallyy operated' through the medium of said first means, and means for indicating during `Vthe operation of the signal whether it is controlled by the called line or by its auxiliary controlling means.

29. In a telephone system, a calling and a called line, a cord circuit and an automatic switch for connecting the two lines, a supervisory signal in said cord circuit under the control vof the called line after connection ytherewith has been established,meanseffec tive whensaid called line is busy for preventing connection thereto and for releasing said switch, auxiliary controlling means in said cord circuit for said signal initiallyvswitch for connecting the two lines, a supervisory signal in said cord circuit under the control of the called line after connection therewith has been established, means effective when said called line is busy for preventing connection thereto and for releasing said switch, auxiliary controlling means in said cord circuit for said signal initially operated through the'inedium of said first lmeans, means for securing the continued operation of said auxiliary controlling means until the disconnection of said calling line independent of said switch, and means for indicating during the operation of the signal whether itis controlled by the called line or by its auxiliary controlling means,

3l. In a telephone system, a calling and Ya called line, a cord circuit and an automatic switch for connecting thetwolines,` asupe`rvisory signal in said cord circuit under the control oic the called line after connection therewith has been established, means eilec` tive when said called line is busy for preventing connection thereto and for releasing said switch, auxiliary controlling means in said cord circuit for said signal initially operated through the medium of said iirst means, means for indicating "during the operation oit the signal whether it is controlled by the called line or by its auxiliary controlling means, and means under the control of said auxiliary controlling means tor transmitting a distinctive tone over the calling line. i

32. In a telephone systeml` a calling and a called line, a cord circuit and an automatic switch for connecting the two lines, a supervisory signal in said cord circuit under the control of the called line aifter connect-ion therewith has been established, means effective when said called line is busy for preventing connection thereto and for releasing said switch, auxiliary controlling means'iii said cord circuit for said signal initially operated through the medium of said first means, means for securing the. continued operation of said auxiliary controlling means independent ot said switch, means for indicating during the operation of? the signal whether it is controlled bythe called line or by its auxiliary controlling means, and means under the control of said auxiliary controlling meansffor transmitting a distinctive tone over the calling line;

ing a potential on said test circuit when said operating circuit is established to make the switch busy,a relay iii said cord circuit liter interrupting said operating circuit, ,means in said switch effective upon the operation Vo 'l'said Aswitch to connect with said line in relay. i i

In a telephone system, a line, a plurality oil trunk lines, an automatic switch Vhaving access to ysaid line andaecessible i'roiiieacli or said trunk lines, means including a cord circuit whereby an operating circuit orsaid switch may be established over one or said trunk lines, a test circuit individual'to said switch, means for placingJ 33. In a telephone system, a` calling andy a Vcalled line, a cord circuit and an automatic switch for connecting the two lines, a supen visory signal in said cord circuit under the control of the called line alterconnection therewith has been established, means eilective when said called line is busy for preventing connection thereto and for releasing said switch, auxiliary controlling means in said cord circuit for said signal initially operated through the medium oil said first means, means for securing ,the continued operation of said auxiliary controlling means until the disconnection ot said calling line independent of said switch, means for indicating during the operation ofthe signal whether it is controlled by the called line or by its auxiliary controlling means, and

means under the control oi said auxiliary controlling meansfor transmitting adistincf p tive tone over the calling line.

34. In a telephone system, a line, a plurality of trunk lines, anaiitomaticV switch having access to said line and accessible from each of said trunk lines, `means in-V cluding` a cord circuit whereby an operating circuit for said switch4 may be established over one of said trunk lines, a test circuit individual to said switch, means' for placpotential on'said test circuit when said `operating circuit is established to make the switch busy, a relay in said cord circuit -for interrupting said operatingcircuit, means in said switch effective upon the operation of said switch to connect with said line in its b usy condition for interrupting said operating circuit to release said switch and re'- move the potential from said test contact, a second relay in said cord circuit responsive to interruption ofV said operating-circuit for initially controlling said first relay, and meansfor maintaining said first relay in operated position independent of said operating circuit 'and of'said switch.

36. In a telephone system, calling and called lines, i al plurality of automatic switches having access tocalled lines, manual equipment `for controlling one of said switches to find said called line, a signal for said calling line and a signal in said testing equipment being operated when the called 'line is busy to release said operate said relay.

38. In a? telephone system, an automatic switch, an operating circuit therefor, a line switch and accessible to said switch, a busy test circuit forsaid line, a relay in saidtest circuit, a relay in said operating circuit individual to said switch, another relay in said operatvingfcircuit common to a number 'of Ysaid switches, said first relay controlled over said test circuit to control said operating circuit,k

whereby said second and third relays are operated, said Second relay controlling the 5 release of said switch and said third relay controlling said'operatng circuit. Signed by me at city of Chicago, Cook county, Illinois, this 15th day of February,

` GEORGE A. YANOCHOWSKI. l0 Signed by me ateity of St.`l)au1, Ramsey county, Minnesota, this 12th day of February,A 1916.

' yHARRY E. HERSHEY.

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