US1771842A - Telephone system - Google Patents

Description

y ,'l930.v T. F. CROCKER 1,771,842

. I v 'iPELEPHdNB SYSTEM Original Filed Sept. 26. 1927 2 Sheets-Sheet: 1

TOLL SERVICE TRUNK f rm Thurnas F Er u'ckgr T. F. CROCKER 1,771,842

TELEPHONE SYSTEM Original Filed Sept. 26. 1927 2 Sheets-Sheet 2 July 29, 1930.

IfiiFfiffi I I 'Thmas F Crbclgar IIIIII NEQ control of the sleeve conductor of the cord, the

, Patented July 29, i 1930 UNiTEn STATES (PATENT OFFICEI THOMAS F. CROOKER, OF CHICAGO, ILLI NOIS,,ASSIGI\TOR TO RESERVE HOLDING COM- PANY, 0F KANSASCITY, MISSOURI, CORPORATION OF DELAWARE TELEBHONE sYsTEM Application filed September 26, 1927, Serial No. 221,878. -Renewed. December 12, 1929.

The present invention relatesto telephone systems ingeneral, but is concerned more particularly with cord circuits and trunk circuits used in giving toll service 'to the subscribers of an automatic telephone exchange. I

' This invention is an improvement on my prior application Serial No. 161,514, filed January 17, 1927, particularly with reference to the feature in the'prior application involving the arrangement whereby the dialling keys and other keys are common to allthe cord circuits of an operators position.

One object of the invention is the produc tion of suitable apparatus whereby the amount of workperformed by the operator is reduced. This is accomplished byremoving the cord-splitting contacts from the dial keys and placing them on suitably-controlled relays. Inthis way,'one or the other of the two dial keys may be left thrown all thetime, with the result that the proper cord-splitting relay operates at the proper time. to cause the impulses from the operators dial to be transmitted over the end of her cord circuit indicated by which of the two dialling keys is .left operated. I v

In this connection, a saving of contacts and a simplificationof the circuits result, because the same cord splitting relays above men tioned for use in connection with dialling may be used to perform the cord-splittingoperation necessary during coin collect and refund and such other operations as may re' quire a splitting of the cord;

It is a further object to prevent the operator from hearing severe clicks. when she plugs into a trunk line withher talking key thrown, asshe may often do when she is inserting the calling plug of a cord into a trunk line jackjafter she has answered a call with the answering plug. This object isobtained by providing a short-circuiting relay to short circuit the receiver of the operatorunder the arrangement-being such that the sleeve of the plug contacts with the sleeve of the jack and causes her receiver to be short 'circuited before the tip and ring contacts of the plug and jack have been brought together. I

A feature of the present arrangement in connection with the operators headset is that the operators receiver is maintained short circuited by relays controlled by off-normal contacts of the calling device for an interval following the operation of the calling device in order to permit a'selector, operated by the train of impulses just sent out, to complete its hunting operation and switch through so as to avoid disagreeable clicks in the operators receiver when the switching through opsults in the closure of an alternate holding circuit during the ringing operation, whereas the holding circuit is not closed by the same action of the sleeve relay during dial-. ling; I Another object of the invention is the production of novel circuit arrangements in connection withthe operators cord circuit for timing a conversation and warning the operator when the subscribers have conversed for a predetermined length of time, three min-- utes, for example. In the specific embodiment of the invention hereindisclosed and described, the/operator is provided with a starting pushbutton (common to her several cord circuits) which she operates whenthe conversation begins. timed to operate at the end of the predetermined interval, operates to signal the operator at the end of such interval.

It is a further object of the invention to simplify the operators cordlcircuitsbycaus ing the calling supervisory lamp to flash when thecon'versation has proceeded for thepredetermined interval, rather than using a sep-' aratelamp.

There'are' other objects and features of a;

A slow-acting device,

invention, having to do for the most part with the circuit details involved in carrying out the foregoing.

The various objects and features of the invention will be understood best upon a further perusal of the description in connection with the accompanying drawings, comprising Figs. 1 and 2, showing by means of the usual circuit diagrams so much of the apparatus in a telephone system embodying the features of the invention as is necessary to an understanding of the same.

In the accompanying drawings, Fig. 1. showsa cord circuit at a toll-operators switehs board together with a jack-ending toll line at the left and'a toll service trunk at the right. The toll line may be one extending to a distant city. The toll service trunk is a trunk line leading to a toll servicetrunking system such as, for example, the one shown in the Wicks Patent #1,633,149, granted June Fig. 2 shows the position equipment, common to all the cords of the switchboard, including the various keys and relays and the operators headset.

The invention having been described generally, a detailed description of the operation of the apparatus shown will now be given. For this purpose it will be assumed that the operator receives a call over the toll line, Fig. 1, for a subscriber Whose line terminates in the local exchange.

In response to the ringing current transmitted over the toll line from the distant end thereat line relay 101 is operated and closes a locking circuit for its lower winding through contacts of cut-off relay 102, at the same time closing a circuit for the call lamp 103. The operator, upon noting the lighted condition of the call lamp, inserts the answering plug of an idle cord circuit, for example the one shown in the drawings, into the jack J 'VVhen the plug P enters the jack J, cut-off relay 102 is energized through the sleeve of the plug and jack and removes the line relay from in bridge of the talking conductors of the ack, at the same time unlocking the line relay so as to extinguish the call lamp 103.

The circuit of relay 1.02 at this time includes contacts'of the ringing key, contacts of the talking key, contacts of relays 107- and. 106 and the supervisory lamp 103 and resist ance 104 in parallel. The lamp 103 however is not lighted owing to the relatively high resistance of relay 102.

Having inserted the plug P into the jack J the operator operates her talking key in the cordcircuit so as to be able to converse with the calling operator. When the talking key is thrown, it connects the tip and ring conductors of the answering plug to the common conductors 131 and 132 leading to the position equipment shown in Fig. 2, and it disconnects the sleeve of the plug P from the associated equipment in the cord circuit and extends it over conductor 133 to the holding circuitincluding resistance 202 Fig. 2, and contacts on certain of the common keys. The tip and. ring strands of the plug P having been connected over conductors 131 and 132 and through contacts of the cord splitting relay 201 to the tip and ring conductors with the calling operator and ascertainthe destination of the call. 4

As a further result of the operation of the talking key, relay 108, Fig. 1, is operated and it divides the cord into two sections, connecting the tip and ring strands ofthe calling plug P over conductors 13 1 and 135 to the position equipment shown in Fig. 2. Relay 108 also disconnects the sleeve of the plug P from the associated supervisory lamp 112 and, assuming the dial call key to be normal, connects it over conductor 136 to the common holding resistance 203, Fig. 2, through contacts of certain of the common keys. However, if the operator has the dial call key operated, andshe usually has, thev sleeve conductor 136 of the common apparatus is extended through contacts of thedial call key, contacts of the off-normal relay 209, associated with the calling device CD, and contacts of relay 205 to the upper winding of relay 207 for purpose which will appear presently. a

Having ascertained the number of the dc sired subscriber, the operator inserts the plug P of the cord circuit into the jack of an idle toll-service trunk, the jack J for 8X- ample. As the plug is inserted into the ack, the tip of the plug makes contact with the tip of the jackbefore the ring of the plug makes contact with the ring of the ack, due to the usual plug and jack construction, whereupon the upper spring contacts of the jack are closed by the associated tip springs, grounding the upper terminal of sleeve relay 115. This ground potential is transmitted through relay and the sleeve of the jack to the sleeve of the plug, causing the quick acting relay 207 Fig. 2 to'energize over the sleeve'circuit and through the contacts above mentioned, to short circuit the operators tele phone. It has been found by test that this short circuiting operation is completedbefore the ring contact of the plug makes contact with the ring spring of the jack, preventing a click in the operators headset from the battery potential across the tip and ring contacts of the jack;

Sleeve relay 115 of the trunk line energizes at this time and closes a bridge across conductors l20'and 121through the lower winding of relay 116 and the winding of relay 119. Relay 119 energizes through the line relay (not shown) of the switch to which the toll-service trunk extends, but the electropolarized relay 116 does not operate at this l il trunk. Upon energizing, {relay119 closesa parallel holding. circuit acrossconductor's 120 an d 121 through. the resistance .118,: at the same time removingsthershunt fromlaround the associated condensers. .These condensers, 'itmaybe,pointedout, are otasufiicientcapacity. to permit ringing tonesand-busy. tones ,to be heard. bythe opera-tor, but. they? .pre vent the starting ofythe ringing operation in the toll service trunkingl systems due to. stray ringing currents. Relay-3 1194 remains operated byv currentLflowr throughiiittin multiple with the holding resistancefllS.

-. Referring now 1 to the ,operators headset sl1own.in'.-Eig; 2, as 31 :further result of the above mentioned energization' ofrrelay207 ,overthe.sleeveycircuit of the. plug P Fig. 1,

acircuit is closed for-the. slowsacting-zrelay .206. Relay 206 thereupon operatesandcloses a multiple shunt around'the:.operator?s-receiver inv addition, to closinga .circuititor. relay ,205 through 5 the ,resistance .208. FRelay 208 operates andlocksitseltto the sleeve extended conductor, at the. same time joining the two terminals of the l lower winding of relays 1207. together ,and .openinggthe circuit throughlthe upper winding of the relay. Relay 207, being quick to v pull ,up initially, as above pointedout-,I is.-.now.."slo'w .to. .fall back due to the closedlowerwin'ding. After an interval, relay 207'fallsLback. and opensthe circuit of -relay }206,..whereupon. relay206 falls back; a, moment ilaterandrremoves.the shunt from around the. operatons telephone, at the same time;openingthe initial circuit of the now-locked relay 205. E'Iheresistance 208 is included in ,the initiahoperating .circuit of the relay :205 so as to avoid shunting the sleeve relayf115Iin the ,to'll service: trunk By the time the relays 205.'z2.07.have gone through the-above. cyfcle'ofoperation the cur rent flow in conductors.12O1an'dl21, Fig. ilg-has become steady and. the condensers associated with relay v11.9. have beeninserted in the talking circuit so thatno. .clickzi's ;pro.duced when the shunt is removedfromaround the-opera-v torstel phone. I r

'Having inserted theplugfP rinto.thejack J 7 with 'theabovedescri'be'd results, theoperator,

who, as above mentioned, is assumed ztoihave left'the dial .callfkey. Fig.2.operated. fromxthe previous operation, how'turnsi her calling device GDin 'accorfdance withthe various digits inthe desired number; i 3

When the callingldeviee CDIis moved from its 2 normal; position, the yeti-normal springs 231, 232, and .233 all make. contact with each other. the contact is made between isprin'gs 22321.2 and-F233, 1 a circuit is 7 closed through relay 209 and contactsof the opertorsrheadset conductors; When springs232 and 231 make contact, the ground potential from'spring- 233 is extended to the upper winding: of relay 207 ,"whereupon relay 207 operates, followed by the operation of relay' "5206. With these two relays operated, the

operators telephone is short circuited, as is ated dial call keyhfor the cut-off relay 201, ':whereupon..relay 201 responds and d scon-p- :ne'cts' conductors131 and 132 from the opera ::associated condenser in the talking circuits.

Relay- 209 operates 'inseries with, the'Ic'ut-oii relay'20l and opensthe extended sleeve circuit, permitting the sleeve relay 115 in thetoll service trunk Fig. 1 to; fallback. Belay 205 2, remains operatedfdue to' the. circuit closed' for it through resistance 208' by relay .206. 1When relay falls-back, it opens the circuit through the lower winding ofre'lay 116 and the winding of relay 119, whereupon relay/119 falls back 'and short circuits the associated condensers, at the same'tirne re- :rnovi ng the bridge includingresistance 118 rfrom across conductors and 121. The

"current flow formerly existingthro'ugh these :two bridges now takes place "over the tip and ring springs of the jack and the correspond- :ingcontacts ofthe plugthrough the extended 'tipfand ring "conductors'134 and 135 and through theoperators headset byway of con-.

'tacts 'on'cut-ofl? relay 204, the condenser associated with the operators headset being short .cir'cuited'by 'contacts of the operated relay 206. I The path of thiscurrent flowit will be noted-is through the impulse'springs of the calling device CD. i As the dial of the calling device rotates ba-cktoits normal position, 'afterhaving been released, the'circuit is interrupted the neces sary number of times'at the impulse springs of the-calling. devicesoas to bring about the desired operation of the first switch in the toll/service traini I 'VVhen the calling device 'CD reaches its normal position, the cit-normal springs 231- 233separates, whereupon relay 209 fallsback,

butthe slowacting relay201'remains operated "for aslight interval-so as to permit a more stable condition to be reestablished inlower windingof relay 116. Relay 119 now energizes'iin multiple with the" loop' through the operatorsheadset and the calling device CD, .Fig. 2, and closes the local multiple bridge through resistance'118, at the same time reinserting the associated "condensers the calling device CD reaches its normal position, with the result that relay 207 falls back after an interval, being rendered slowacting by the closed circuit through itslower winding. llpon fallingiback, relay 207 opens the circuit of the slow acting relay 206, with the result that relay 206'falls1back after aninterval and removes the shunt from around the associated condenser in the talking circuit, at the same time opening the local locking circuit for relay 20-3 andremoving the shunt from around the operators telephone. The circu'ithaving become stabilized in the meantime, with no current-flow in the operators circuit, no click is heard. Relay 205 remainslocked upxover the extended sleeve circuit. 1 V

The operator now dials the remaining'digits in the desired number.

If the called line is busy, the busy tone is heard by the operator after the complete number is dialled, and she-may release the connection by withdrawing the plug P from the jack J Assumingthat the called line isidle,"the connector in use seizes the called line and initiates operationswhich result in a reversal of the current fiowlin conductors 120 and 121. This takes place after relays'115 and 119, of the trunk have reoperated,but before the operators relays 207 and 206 have fallen back. When this reversal occurs, relay 116 operates as the current flows in its windings now assist each other, and relay 119 falls back momentarily owingto the fact that the magnetism in its magnetic circuit must die down to zero and build up againin the opposite direction when the current flow is're; versed. If it were not, for the presence of the bridge including resistatnce 118 across the trunks through contacts of relay 119, the

' line relay supplying current. to conductors 120 and 121 would fall back .at this time due to the high impedance of relay 119. How ever, resistance 118 affords a ready path for the reversed current flow over whichthe line relay is held until relay 119 lets go. VVhen relay 119 lets go, the, associated condensers are short circuited and the current flow over 1 conductors 120 and 121 is continued through the operators circuit (the condenser and the operators telephone being still short circuited by relay 206 Fig; 2).

through resistance 118 is picked up-again when relay 119 energizes in the opposite di-f rection.

As a result of the energizationof the electro-polarized relay 116, a ground-return holding circuitis iprepared'at the lower armature of the relay, and a shunt-is placed 7 stores the talking key.

The current flowaround the upper winding of sleeve relay 7 115 at the upper contacts of the electropolarized relay through contacts of relay 119, thereby pe'rmittingan'increased current flow over the sleeve circuit so as to light the supervisory lamp 112 when the operator re- Having dialled thenumber and not having received the busy signal, the operator new restores her-talking key, whereupon relay 108 falls back completely disassociating the cord circuitfrom the position equipment. The sleeve circuit of the plug P is now transferred back to the supervisory lamp 112 whereupon the lamp 112 becomes lighted over the sleeve circuit in series with the lower winding of the sleeve relay115, the upper winding of-thisrelay being now shunted by the relays 116*and 119. By the lighted condition of thelamp 112, the operator is informed'that the called'line is idle and has been seized."

In order to signal the subscriber on the called line, after she has been notified to do so by the calling operator, the operator throws the ringing key associated with a plug P whereupon ringing current is transmitted over the tip and ring conductors of the jack J At the same time, the shunt is removed from around the resistance 11 1 by the ringing key, extinguishing the lamp 112 and causin the sleeve relay 115 to fall back. The resistance 114 must not be sohigh as to cause the deenergi'zati'on of a tool-line sleeve relay such as 102associated with the jack J As 'a result, the resistance is high enough to cause the sleeve relay to fall back when its upper winding is shunted, but not otherwise. Theup'per' win'ding of the relay is shunted at this'time by the contactslof relays 116 and 119. When the sleeve relay falls back, it grounds the lower conductor 121 through contacts ofrelay 116, at the same time opening the -bridge throughthe lower winding of relay'116 and relay 119. Relay 116 remains operated by the current flow throughits'upper winding alone.v Relay 119 however, falls backfshuritgfthe associated condensers, and would remove the shunt from around the up per winding of relay 115 were it not forthe upper'contacts o f relay 115 which closes a multiple pointin itsown shunt circuit. The ringing current now passes out over the up-. per conductor. 120 to the switch train and causes the: automatic signalling of the called subscriber to start in a manner explained in the /Vicks patent herein'before referred to.

When the operator restores the ringing key,'the ringing current is removed and the resistance llisshort circuited. Whenthis occurs, the supervisory. lamp 112'is1again lighted, and relay 115 v again pulls up." The ground potential placed on. conductor 121; during the time that relay 115is'deenergized with relay 1-16 operated is effective in maintaining operated the-line -relay*which has a windingv connected between battery and c' n-- ductor 121 at this time} I Whenthe called subscriber responds,; tlie 5 talking circuit is closed in the switohftrain andthe current flow over con'ductors'120'and 121 is stopped, the so called dry trunksupervision-being used, When this'occurs, relay 119 falls back and short circuits the assooiat-' edlgcondensersin the talking;circuit so as to afliord abetter talking condition and removes then bridge through--res stance 118' irom' acrossthe talking circuit. -At the sarne time,

relay119 removesthe shunt from around the ,upperwinding of relay 116, thereby extinguishing the supervisory lamp 112, which I I does not remain lighted in series" with the entire winding of the sleeve relay.

resumed, operatingl'relay- 119 to again re place the shunt around the upper winding of thesleeve relay, giving a disconnect sign ah The distant operator'may-senda disconnect-rapplication of ringing'current over the toll line,v in whichicase relay "1077' of the cord circuit operates and 1 removes the shunt from around. relay 106,:whe'reupon relay 106 operates' and opens a further point in itsshunt circuit, at the: same time closinga circuit for the lamp 103,-which lamp becomes lighted a disconnect signal; :Q

- When the operator pulls "down the connection;the-bord-circuit' apparatus reverts to its v position, and the-tollservice switch normal tran i11s released. Assuming now that the operator desires to collect a coin deposited-at apay' station callediover the cord circuit shown in the I drawings andiover the tQll serVicetrunk rshown, sheoperates -her collect call key I ,with the talking key thrown the, cord; This of course takes place after the (con 'nection has been setup "to the line, in

' which-case the ele'ctro pola-rized"relay 116 is: operated; :When the :collect" call key is thrown, the ;lower contactsof the keyf operate vrelay 20t which= splits the cord and places i the current i from I, the negative 110 volt' source'on the extended tip""conductor 134.-' The operated key also removes battery from the extended sleeve conductor 136, deenergizing isleeve relay 115'.v 1 Sleeve relay 7 115 opens the-circuit'throughrelayf119,"deenergizing this relay sons to shunt the con-:-

Ideterrnined interval or takes such other steps I densersand permit the high voltagejcurrent to pass overtheupper conductor 120. Be lay 115also-clo'ses a groundreturn' circuit at its lowercontact to conductor 121 so as; to afiord a return path'for the-highlvoltage- I current under certainiconditionsfofthe switch lay 109 to close" whereupon the supervi trainarid-0 aroma "taming circuit for the In the same way, the operator may refund I a coin-,- by-operating "therefund*call key automatic switches. yWlien "the rel 1 stored, the" circuits shown return to' their" previous condition.

In"' case 'theioperat'or desires to'iconverse over the answering end of *the cord gwnne; the calling end isfcutofi, she operates thec'utfj 'ofi call key, operating relay204 to cut'bfi the' calling end, leaving her "headset connected-"- to the answering end er the cord.

It Will be' noted that the keys above referred vto' appear, in duplicate on both ends of the, common equipment so that either end ofthe cord may" be usedQin efieeting a connection; It is to be noted"especiallythat, the end of the cord over which 'diallingjirn f" pulses are transmitted is dependent entire ly'upon whichof the two, dial keysisfthrown when the dial moves fromits 'normarp'esig tio'n-g- If the dial call key is thrown as -hl' -e ;--inbefore described, the answering'cut-bff te lay?"20'l"is operated as hereinbefore pointed stead, the calling cut-foff anyxeor 'is operate'd' instead, and the dialypulses areitransJ- fl mit'ted over the answering end of [the cord;

Assuming'now that thejoperator 'WiShBS tof "time a connection and tobe'notified wlien.,f*-'

a 'c'onversation has proceeded "ffor a prede terininedf length of: time, for example, three minutes, she operates the 'fcoinmonpush'f button PB, Fig. 1, while the talking key and";

corresponding 'relay l 08' ,of the cord "circuit i'o riv h hefq n' f t en is pass 'giar operated? ,Wlien'u' this occurs,- a c cuitfis closedsfor' the starting; relay ll :1, f whereupon i i this relay operates and lock fitselfi f to the sleeve conductor in multiple with the su ervisory ;lamp,"at the fsaine time i'openin'g its initial circuit and preparing a j'c'ircuit'forfth i when retarded relay 109, which is comp tard'ed by asu'itable slow-acting device,"such the' predetermined' intervalfithe s19 actlng device tll'Offlaerrni-ts thecontactsf ofa v, r :Y. lamp *112 commences to flash und'ergth'ef Goa; tI'OlTOf the flasher 'F'. The resistancdas'so ciatefd'withi-theflasherF in the flashinglead' whichthe" plug 1?? is inserted. i

subscribers that they have conversedlthe preas she-may be: instructed: totake;

is toffprevent the short 'cirouiting "of the sleeve relay" associated 'With'the" jack? in'td 7 T 3 f.

i p i 'q 1, 7 fl l l f fibf e" I su ri y f ainpi .1 2, the bp' r'a br? -L." operates her talking key andniaywai'n ih6' W hen the operator throwsher i h 2 8 ali 11 em ns pf s ii b relayf'lf'OQTis thereupon released tostop the'fif "flashing operatioiii Elf-the" subscribers have "7 V the conductors of said trunk line connectedv to the outgoing side of said-condenser, a seca desire to converse for another period of time, the operator merely restores her talking key, whereupon the timingoperation commences agam.

' What is claimed is:

1. Ina telephonesystem, a trunk line including two talking conductors, a bridge across'said talking conductors, a relay energized responsive to current flow through said bridge, a second bridge, a condenser'connected in series withone talking conductor and directly shunted when said relay is normal, and contacts on said relay effective when the relay is operated to remove the shunt from around said condenser and to place said second bridge directly in multiple with the first.

2. In a telephone system, a'trunk line including two talking, conductors, acondenser in series with one of said talking conductors, a bridge across said talking conductors on one side of said condenser, a relay in said bridge responsive'toticurrent fiow over said trunk line, a shunt'aroundsaid condenser controlled by saidirelay, a'second bridge across said trunk line in multiple with the first bridge when the relay iseoperated, and

contacts onv said relay for opening the second bridge and for shunting said condenser when the'relay falls back responsive. to a cessation I in current flow over said trunk line.

3. Ina telephone system, a trunk line comprising two, talking conductors outgoing from a switchboard, a condenser inserted in one of saidtalking conductors, a shunt normally around'said condenser, a bridge across 011d bridge across sai'dtrunk line directly in multiple with the first bridge, inean'sfforplacing a bridge across the trunk line on the switchboard side of said condenser and for opening the first named bridge, means responsiveto the cessationbf current flow in the first named "bridge for 'shuting said condenser and forlremoving the second bridge from across the trunkline. v I

4. In a telephone system, atrunk line, three bridges arranged to be placed across said trunk line, means for, placing the first bridge across the said trunk line, means responsive to the resulting current flow through the first bridge for placing the second bridge across the trunk line, means'for preparing the third;

bridge and for opening the first bridge, means responsive to the resulting cessation of current flow inthefirst bridge for reniov ing the second bridge from across the trunk lineand for placing the third bridge across the trunkline. i

55111 a telephone system, a bridges arranged to be placedacross said trunk line, means for placing the first bridge across the trunk line,'means for preparing the second" bridge 'and ..for opening. the first bridge,mean s responsive to the opening of trunk line, two

holding bridge is opened to permit the condenserstobe shunted for the 6. In a telephone system, a trunk line extending from a manual switchboard to an automatic switchboard, means for extending a connection to said trunk line at said manual switchboard and for placing a switch holding bridge across the trunk line, said bridge,

excluding said manual switchboard, operator-controlled means for opening said holdmg bridge to permit the. operation of the mechanism at the automatic switchboard to I be controlled from the manual switchboard and for opening it subsequently to permit ringing current to be transmitted from the manual switchboard to the automatic switch board, a device at said'manual switchboard end of said trunk revertively controlled from ,the automatic switchboard after the automatic switching mechanism has been set and before the ringing current has been transmitted, and means controlled by said: device for rendering effective an, alternative holding circuit for the automatic switching mechanism when said bridge is opened to permit the passage of ringing current.

7. Ina telephone system, a trunk line ex tending from a manual switchboard to an au tomaticswitchboard, ringin'g-current-block ing condensers inserted in said trunk line, means controlled by the operator at said manual switchboard for shunting said condensers to permit the mechanism at the aui V tomatic switchboard to be controlled from the manual switchboard and for subsequently shunting? the condensers topermit the pas- ;sage of ringing current, a holding bridge 9 across said trunk 11116 on the automatic switchboardside'ofsaid condensers, the said condenser shunting means being rendered cf- 7 festive upon a cessation of the'ocurrent fiowT in said holding bridge, an alternative'switch holding circuit path, and means revertivelycontrolled from the automatic switchboard."

after the connection has been set up andbe fore the ringing currenthas beentransmit- 1 ted for preparing said alternativexswitchr holding path so that it is completed when the a bridge across said trunk line at the manual switchboard end, a polarized relay included in said bridge,-and a sWitch-holding circuit path alternative to said bridge and controlled 7 by said relay.

49. In a telephone system,atrunkqline extending from a manual switchboard to an automatic switchboard whereat a current flow in a given direction is brought about over. said trunk line while: a connection is being set up through the automatic switchboard and a reversed current flow is caused to take place after the connection isset up and before and after conversation, and whereat the current flow over the trunk line is prevented during conversation, a bridge across said trunk line at the manual switchboard end'thereof including a polarized and a non-polarized relay, a supervisory lamp, and a circuit for said lamp controlled by said relays jointly.

10. In a combined manualand automatic telephone system in which automatic switches may be operated from a manualswitchboard, a link circuit at said manual switchboard comprising two sections, a calling device for controlling the operation of automaticswitohes, said calling device having anormal position, and meansresponsiveto the movement of said calling device from its normal position to effect the control of said switches for associatingsaid calling device with one section of said link circuit to'the exclusion oi the other and foricancelling such association upon the return of the calling device to normal.

11. In a combined manual and automatic:

ing device for controlling the operation of r automatic switches over elther sectlon of said link circult, a key contact forpredetermlning the association. of said calling device with either of said sections, and means effective upon the turning of the call ng devlce oil normal for completing the predetermined association. I p v 13. In a;telephone system, an operators link circuit comprising two sections, a calling device for association with either section,op erator controlledrmeans for predeterminingwith which section the calling device shall be associated to the exclusion of theother and means eii'ective upon'the manipulation of said calling device bythe operator for carrying into effect the predetermined operation,

14. In a telephone system, an operators link circuit divided into three sections, a call- 1 ing'device connected to the middle section, av

relay associatedwith the first section for disconnecting the first section from the middle section to permit'the'calling device to' operajte over the middle and' third sections, [a second" relaysiinilarly associatediwith the first sec tion; coin on oliapparatus, and means for oo'eratin ithei of and, rcla s selectivel 1 l D i when 'saidcoin controlled apparatus is being idjvhjen'said calling device is being" 15, In a telephone system, an operatoi"s link circuit dividil 1 into three sections, arelayffor di onnecting the middlesection from the; first section, a slinilar relay for disconnecting f theiniddleisection from theo'third section, a

callingdelice connected to the middle section, means for operating elther of said relays whenthe-calling device is in use, and means for, operating eitherof said relays-selectively when saidc'alling device isnot in use 1 6. In atelephone system inwhich connections faresetupthrough link circuitsjat'a "33" manualswitchboard, a separate timing device for e chiink circuit, and operator-controlled,

means 'co-mmonftoall link circuits for, ng anydes red tlmlngdevice.

1' Zl Ina tel phone system, atrunk line eXQ tending fromja manual switchboard, a bridge across said trunk line at the, manual switchboard including a polarized'fr elay and a nony i i tlr r a o 18." n1 atelephonesystenna trunk line eX- tending from a manual switchboard, a bridge across'said trunklineat the manual switch board including a polarized relay and a nonpolarized relay, a supervisory device, contacts on: each relay, and a circuit for said device including said contacts in series. I

- 19. In a telephone systemin which'connections are set up through link'circuitsvat a manual switchboard, a separate timing device mon to allsaid timing devices,'means for associating said starting device'with any one of said timing devices, and means responsive to, I a subsequent operation of the starting device torstarting the associated timing device.

20. In a telephone system in which connections are set i up through link circuits at fa manual switchboard aseparatetiming device f I,

for each link circuit, a talking key for each link circuit operable under the control'of the operator at the switch-board,'a starting device common to all-said timing devices, and means responsive to an operation of said starting for each link circuit,a starting device comdevice for starting the operation of the timdevice associated with any link circuit at which the talking key is operated. I

'21. Ina'telephone system, a link circuit comprisin'g'two sections, a calling device normally connected to'both sections,means "forselectingeither section, and means automatically responsive to an 'operation'rof the polariz'edfrelay," a supervisory; device, and a n 95 7 Y Y circuit 'for said device controlled by said calling device for disconnecting the calling device from the other section.

22. In a telephone system, a link'circuit comprising two sections, a calling device normally associated with both sections, means for selecting either section, and means automatically responsive to an operation of the calling device for disassociating the calling device from the other section.

23. In a telephone system a plurality of individual link circuits each comprising two sections, a common link circuit comprising two sections and containing a calling device arranged to exercise a control over switching apparatus by way of either section of any individual link circuit, means for connecting the sections of said common link circuit to the sections, respectively, of any individual link circuit and for selecting either section of the common link circuit, and means automatically responsive to anoperation of said calling device to exercise a control over switching apparatus by way of the selected section of the common link and the connected section of the individual link for disassociating said calling device from the other section of the common link and connected section oi the individual link.

In witness whereof, I hereunto subscribe my name this 24th day of September, A. D.

THOMAS F. CROCKER.

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