US1799532A - Connecter switch - Google Patents

Description

Apnl 7, 1931. A. .1. RAY ET AL 1,799,532

CONNECTER swmcn Filed Jan. 7, 1929 2 Sheets-Sheet l SSNVHOXS .LSICI 0i INT. GED.

Clarence *E'. L nmax La narcl L. 5.55155 M i-7 April 7, 1931. A. J. RAY ET AL. 1,799,532

CONNECTER SWITCH Filed Jan. '7; 1929 2 Sheets-Sheet 2 IN 7. GED.

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Patented Apr. 7, 1931 lill llTiEfi STATES Anrrina 3'. sex, or corn, enema-non PATENT QFFHQE terrain or can PARK, an]: LrionnR-n L.

F V ETEEATGN, ILL-TESTS, ASSTGNORS TO RESERVE HOLDING COMPANY, 0F KANSAS CITY, MISSUUBI, A COB-EGRATIGN 0F DELAW'ARE CONNECTER SNITCH Application filed January 7, 1929. Serial No. 330,744.

This invention relates to automatic teleohone s stems in eneral but is more oarticularly concerned with small automatic telephone exchange systems comprising only a few lines; and the object of the invention, briefly stated, is the provision of new and improved automatic switching apparatus which is particularly suitable for use in such small automatic telephone systems.

A particular feature of the invention is a new and simplified connecter switch adapted to be connected directly to a telephone line. This new connecter switch functions as an ordinary connecter when extending a connection to an individual subscribers line, may be operated as a code ringing connecter to signal a particular party on a party line, and may also be operated as a repeater for extending calls to some other telephone'exchange, such as the main automatic exchange of a neighboring city.

One of the features of the invention relates to the manner in which thecalling connecter controls the called connecter to apply ringing current to the called line and the manner in which the called connecter cuts oif the ringing current when the called party answers.

Another feature of the invention relates to the combined busy and ring-cut-ofl relay in the connecter which is operated as a busy relay when the connecter is a calling connecter and is operated as a ring-cut-ofi relay when'the line associated with the connecter is called. 7

The foregoing and other features not specifically mentioned may be described more in detail by referring to the drawings comprising Figs. 1 and 2, which when Fig. 2 is placed below Fig. 1 show by means of the usual circuit diagrams the apparatus to be used in this small automatic telephone exchange.

In Fig. 1 is shown the new and improved connecter Owhich is individual to the substation'line comprising conductors 1 and 2, and has access in its banks to all the lines in the exchange and to the trunks extending to the distant automatic exchange. The connecter O is of the well known Vertical and rotary type of switch having a plurality of horizontal rows of ten sets of contacts each. In this particular disclosure outgoing trunks to the distant automatic exchange are acces sible in the tenth level and the rural or party lines (not shown) are preferably accessible from the ninth level of the connecter banks.

In the drawings, one trunk to the automatic exchange accessible in the tenth level of bank contacts is shown.

At the right of Fig. 1 the trunk line extendingto the distant automatic exchange is designated by the reference character TC and comprises a plurality of .relays and a repeating coil.

Substation A comprises the usual talking, signalling and switch controlling instrumentalities generally used by automatic subscribers.

In Fig. 2 there is shown a connecter C and once characters and 170 which close as soon as the respective connectors take their first rotary step.

Each telephone line in this exchange, regardless of whether it is an individual line, a party line, or a rural line, has a connecter switch similar to connecter C associated therewith in the same manner as connecter C is associated with the line of substation A.

Having described the system and the apparatus to be used, a detailed description of the operation thereof will now be given. For this purpose it will be assumed that the subscriber at substation A wishes to converse with the subscriber at substation A. To establish the connection, the subscriber at substation A rcmoves his receiver and dials the telephone num er of sub tat on A.-

In connectors C and C are shown ro- I tary elf-normal springs indicated by refer- When the receiver is removed from the switchhook, the switchhook springs-close a circuit for energizing the line relay 8 of connecter C as follows: from ground by way of the lower Winding of relay 8, resting contact of armature 17 and said armature, conductor 2, through the substation loop, conductor 1, armature 16 and its resting contact,

and through the upper winding of line relay 8 to battery. It armature 18 line relay 3 closes a circuit for energizing combined busy and ring-cut-off relay 10 by way of vertical oft-normal springs 20, and at armature 19 closes a circuit for energizing release relay 9 by way of ar nature 40. Release relay 9, upon energizing, .at armature 21 grounds release trunk conductor 5 in orderto make the line of substation A-test busy to the switcheshaving access thereto and also closes a circuit for energizing combined switching and change over relay .12 by way of vertical cit-normal springs 71 and the upper winding of relay 12.

At armature 22 release relay 9 closes a locking circuit for itself independentof armature 40 and at armature 23 and its working contact prepares a point in the-impulsing circuit and the'busyitone to the calling line which, however, is not eiiective at this time because of the energization of switching relay 12. Switching relay 12, upon energizing, at armature 34 closes a point in-the upper talking circuit; at'armature connects interrupter ground to ringing control wiper 44; at armature 36 completes a locking circuit for busy relay 10 so thatirelay 10 will not deenergize when the vertical oft-normal springs 20 open on the "first vertical step of the switch; at armature 37 connects ground to release trunk wiper 45 atarmature 38 prepares a locking circuit for itself at armature 39 prepares a further point in theimpnlsing circuit tothe ertical mag- :net 13 atitsworking contact and at ltS'lQStlIlQ contact opens point in the circuit of the rotary magnet-'14 armature 40 opens the orig inal energizing. circuit of release'relay 9; and at armature 41 disconnects the busy tone source from thelower talking conductor at its restingcontact and at its working contacts connects the lower talking conductors to Wiper 46.

lnlresponsetothe dialling oft-he first digit,

thelcircuit-ot the line relay '8 is opened a plurality of times. The line relay therefore deenergizes a corresponding number of times. The first time line relay 3 deenergizes, a ground impulse is sent to the vertical magnet 13 by way of armature 19 and its resting contact, armature 23 and its working contact, armature 39 and its working contact, armature 28 and through the vertical magnet 13 to battery. A branch of this circuit extends in parallel to the winding of series relay 11, thereby causing this relay to energize. Vertical magnet 13 operates and raises the wipers 43 to 46, inclusive, on vertical step. This operation shifts the vertical oil-normal springs, thereby opening springs 20 and 71 and closing springs 24. The remaining impulses of the first digit operates the vertical magnet step by step to raise the switch wipers opposite the desired level in which the line of substation A terminates. Series relay 11, due to its slow-releasing characteristics is maintained energized during impulse transmission and for a short period of time thereafter. Series relay 11, upon energizing, at armature 32 closes a further point in the circuit of the upper winding of switching relay 12 so that switching relay 12 does not de-energize when the vertical off-normal springs 71 open on the first vertical step; and at armature 33 prepares a circuit for the rotary magnet 14 which is of utility during-the rotary operation of the connecter. Shortly after the secession of impulses, slow-acting series relay 11 deenergizes and at armature 32 opens the locking circuit of switching relay 12, thereby deenergizing the latter relay. At armature 36 and its resting contact relay 12 prepares a circuit for the busy relay 10 which is closed as soon as the rotary off-normal springs close on the first rotary step of the connector wipers and at armature 36 and its working contact relay 12 also opens the locking circuit of the busy relay 10 and said relay accordingly deenergizes. At armature 26 relay 10 prepares a circuit for the lower winding of switching relay 12; at armature 28 opens the circuit extending to the vertical magnet 13; at armature 29 prepares a point in the impulsing circuit to the rotary magnet 14; and at armature 30 disconnects thebusy tone lead. V

The calling subscriber may now dial the next digit and responsive thereto slow-acting release relay 11 is again energized and the rotary magnet .14 is intermittently operated to step the wipers 43 to 46, inclusive, into engagement with the bank contacts 50, 53, 56 and 59. The circuit for operating the rotary magnet 14 may be traced as follows :ground by way of armature 19 audits resting contact, armature 23 and its working contact, armature 39 and its resting contact, armature 29, and through the winding of rotary magnet 14 to battery. Slow-acting series relay 1.1 is maintained energized during therotary impulses, and at armature 33 maintains the 'impulsing circuit to pendent of armature 29. This provision is the rotary magnet indewhile the test wiper is passing over groundmagnet 15.

' closed on ed or busy test contacts. The operation from now on depends upon Whether the line of substation A is busy or idle. Assuming that the line of substation A is busy when called, a ground potential on test contact 56 will be encountered by the test wiper 45 for energizing the busy relay 10 as follows: grounded test contact 56, test wiper 45, armature 31 and its working contact, rotary off-normal springs which were the first rotary step, resting contact of armature 36 and said armature, and through the winding of busy relay 10 to battery. Busy relay 10 at armature 25 opens the circuit of ringing relay 7; at armature 26 prepares a locking circuit for itself which is closed at the normally closed springs controlled by armature 31 when slow-acting series relay releases; at armature 29 opens the :5 circuit of the rotary magnet; and at a-rma-- ture 30 connects the busy tone lead to the lower talking conductor by way of armature 41 by means of which the callingsubscriber A is given the busy tone in the well-known manner. When sl'ow-actingseries relay 11 deenergizes, said relay at the normally closed springs controlled by armature 31 completes the locking circuit for the busy relay 10 which may be traced as follows: ground by way of J armature 21; armature 26 and its working contact, normally closed springs controlled by armature 31, rotary cit-normal springs 70, resting contact of armature 36 and said armature, and through the winding of busy re ay 10 to battery.

Subscriber A upon hearing the well-known thereby busy tone will replace his receiver,

Line

opening the circuit of line relay 8. relay 8, upon deenergizing,

release relay 9 and at its resting contact prepares a point in the circuit for release magnet 15.

gizing, at armature 21 removes ground from release trunk conductor 5 and opens the looking circuit of busy relay 10; and at armature 23 closestlie circuit for operatingthe release By the operation of release magnet 15 the wipers of the connecter C are returned to their normal position.

Assuming now that the line of substation A is idle when called, the busy relay 10 is not energized because there is no ground potential on test contact 56. Instead, the

switching relay 12 is energized over the following circuit when the slow-acting series at armature 19 and 1ts working contact opens the circuit of Slow-acting release relay 9, upondeenerarmature, test wiper45, test contact 56, conductor 105, vertlcal ofl normal springs 171 (Fig. 2) and through the upper Winding of switching relay 112 to battery. Switching rela 12 u on ener izin' atarniatures In the called connecter C" relay 112 ener-,

gizes over the above-traced circuit and at armature 1410 opens a point in the circuit of slow-to-release relay 109 so that the-latter relay will not energize when the line relay 108 is energized responsive to the called subscriber answering. When interrupted ground is connected to ring-control wiper 4:4 and contact 53 (Fig. 1) a circuit may be traced over conductor 10 1 and armature 125, Fig. 2, for

energizing ringing relay 107 in connector C.

Ringing relay 107 is intermittently operated over the above-traced circuit and at armaturcs 116 and 117 opens the talking circuit extending to the line of substation A and at the working contacts of said armatures connects ringing current across the line conductors 101 and 102 of sub-station A to signal such subscriber. When called subscriber A answers by removing his receiver, a direct current bridge is closed across the line conductors 101 and 102, thereby causing the operation of line relay 108 when ringing relay 107 is in its normal position during a silent period. Line relay 108, upon energizing, at armature 118 closes a circuit for energizing combined busy and ring-cut-olf relay 110. Combined busy and ring-cut-oif relay 110, upon energizing, at armature 125 opens the circuit of the ringing relay 107 and at armature 126 closes a locking circuit for itself which may be traced as follows from grounded release trunk conductor 105, armature 126 and its Working contact, working contact of armature 136 and said armature, and winding of relay to battery. 0 The calling and 34 and 4:1 completes the talking circuit at armamil called subscribers are now connected and may After conversation and responsive to the called subscrlber A replacing his rece ver line relay 108 deenergizes and at armature A 118 opens the original energizing circuit of relay 110. Relay 110 does not deenergize at this time because of the previously traced locking circuit extending over grounded release trunk conductor 105. In the calling connecter C and responsive tosubscriber A replacing his receiver on the switchhook, line relay 8 decnergizes and at armature 19 opens the circuit of release relay 9 as previously described. Release relay 9, upon deenergizing, opens the locking circuit of switching relay 12 at armature 21 and also removes ground from release trunk conductors 5 and 1055, thereby permitting the switching relay 112 andbusy relay 110 in the called connecter C to deenergize. At armature 23 release relay 9 again closes the circuit for the release magnet 15, thereby causing the release of the connecter C in the same manner as previously described. The connecters C and C are now in normal position and may be usedin other calls.

Having described in detail how connections between local subscribers are completed, a description will now be given of the manner in which local subscribers call rural or party line subscribers. For this purpose it will be assumed that subscriber A desiresto talk to a party line subscriber. Responsive to the removal of the receiver at substation A and responsive to the operation of the calling device theconnecter C is operated in the same manner as previously described to set its wipers on the bank contacts associated with the party'line. In this case, however, since the party line terminates in the ninth level of the connecter banks the normal post springs 42 are operated when the wipers are raised opposite the ninth level. The operation of the normal post springs 42 opens the circuit ex tending to interrupted ground over conductor 47 at its resting contact and at its work ing contact prepares a circuit forimpulsing over the ringing control wiper "A. After dialling the telephone number of the party line subscriber A will then dial the code ringing number of the desired party on the party line. In this case we will assume that the code number of the desired party is 2 and 2 and therefore subscriber A will dial the digits 2 and 2. Responsive to the operation of the calling device CD the line relay follows the impulses and transmits two ground impulses for the first digit and an additional two grounded impulses for the second digit over wiper 44 which is now connected by way 01 a ringing conductor such as conductor lOl', to the ringing relay, such as ringing relays 7 and 107, in the connecter similar to connecter C in which th party line terminates. Responsive to the first two impulses the ringing relay in the party line connecter is operated to connect ringing current to the called line responsive to-the first digit and after an inter val of time is again operated responsive to the second digit for ringing the bells on the party line. The ringing relays such as 7 and 107 have short copper slugs on theheel end of the coil in order to make them slightly slow-to- .rel-ease. Thus when thedigit2 is dialled the ringing relay in the called party line connecter will remain operated between impulses and ringing current is connected to the party line to produce a short ring of the bells at all party line subscribers on this line. A larger digit such as 8 is dialled by the calling subscriber to produce a long ring of the bells at the party line stations. All the bells on the party line ring but only the party called, upon recognizing his code ring, answers by removing his receiver. Responsive to the called subscriber answering, the connecter switch individual to the party line operates in the same manner as described for a local connectionto cut off the ringing. 111 case the called party does not immediately answer the calling party can again dial the code ringing digits of the desired party and again operate the ringers on the party line. In case the desired party does not answer after ringing a plurality of times the calling subscriber may, if desired, code ring another subscriber on the same line. This can obviously be done in the same manner as previously described by dialling a difierent ringing code. After conversation the release of the connection is accomplished in the same manner as previously described.

Having described how local and party line connections are completed, a description will now be given of the manner in which a local subscriber establishes connection with a trunk circuit extending to a distant automatic exchange and how the calling subscriber impulses over the trunk line to control the automatic switches in the distant exchange to complete a desired connection. For this purpose it will be assumed that subscriber A desires to complete a connection to a subscribers line in the distant automatic exchange. The calling subscriber operates the connecter C in the same manner as previously described to cause the switch wipers to engage the bank contacts in which the trunk lines extending to the dis tant automatic exchange and other exchanges terminate in the tenth level ofthe connecter banks. The normal post springs 42 are again operated when the wipers are raised opposite the tenth level to prepare an impulsing circuit over the ring-control wiper 44:. Assuming that the trunk circuit TC is the trunk circuit with which the wipers or" the connecter C are now in engagement, the switching relay 12 energizes over a portion of the circuitpreviously traced for it by way of wiper 4C5, bank contact 54, conductor 62, and through the winding of relay 64 to battery. Switching relay12 energizes in the same manner as previously described and relay 64 of thetrunk circuit TC energizes and at armature 66 closes a circuit for grounding the two conductors 68 and 69 extending to the distant automatic exchange. Responsive to the grounding of the conductors 68 and 69 the line relay of the incoming selector in the distant automatic exchange is energized to prepare that switch for operation. The calling subscriber may now dial the telephone number of the desired automatic exchange subscribers line. Line relay 8 again follows the impulses and again repeats the impulses to wiper 44 as previously described. Since wiper it is in engagement with bank contact 51 and conductor (51 relay in the trunk circuit/TC is energized each time line relay 8 deenergizes and connects ground to theimpulsing circuit at armature 19 and its resting contact. At armature 67 relay 65 interrupts the ground circuit extending over the trunk line to the distant automatic exchange, thereby interrupting the circuit of the line relay in the incoming selector to cause the operation of such selector. The

automatic exchange and in known manner the connection to the called automatlc subscriber is completed. After conversation and responsive to the replacement of the receiver at substation A, the connecter is released in the same manner as previously described. By the release of the connecter C the circuit of relay 64 is opened and said relay accordingly deenergizes and removes ground from conductors 68 and 69, thereby permitting the release of the switches in the automatic exchange. 7

Incoming calls from the distant automatic exchanges are completed over trunk lines which terminate in individual connecters, such as connecters C and G, and which connecters are controlled from the automatic exchanges to complete connections to the local and party lines in the same manner as previously described.

The invention having been fully described, what is considered new and is desired to have protected by Letters Patent will be pointed out in the appended claims.

What is claimed is: 1

1. In a telephone system, a subscribers line, a switch individual to said line, and a relay in said switch operated as a busy relay when said line is a calling line and as a ringcut-otl' relay when said lineis a called line.

2. In a telephone system, a subscribers line, a switch individual to said line, a busy tone source, a source of ringing current, and a combined busy and ring-cut-otl relay'in said switch for connecting the busy tone to said line in case said line is a calling line and has operated said switch into engagement with a busy line and for cutting ofi the application of ringing current responsive to the sub scriber on said line removing his receiver in case said line is a called line and is being rung.

3. In a telephone system, a calling subscribers line, an automatic switch individual thereto, a called subscribers line and an automatic switch individual thereto, means for operating the switch associated with the call 7 ring-cut-ofi relay in said called switch oper-' ated responsive to the called subscriber answering.

a. In a telephone system, a calling subscribers line, an automatic switch individual thereto, a called subscribers line and an automatic switch individual thereto, means for operating the switch associated with the calling line to complete a connection to the called line, a line relay in both of said switches for feeding talking battery to their respective lines, and a single condenser in each of said switches for separating the respective battery feed relays.

5. In a telephone system, a calling subscribers line, an automatic switch individual thereto, a called subscribers line and an automatic switch individual thereto, means for operating the switch associated with the calling line to complete a connection-to the called line, a ringing relay in the switch associated with the called line, and means in the calling switch for automatically operating said ringing relay to apply ringing current to the called line. I

6. In a telephone system, a switch indi vidual to a subscribers line, a combined busy and ring-cut-oii relay in said switch, and means efiective when said relay has been operated asa ring-cut-ofi' relayfor locking said relay in operated position independent of control from said line.

7. In a telephone system, a callingsubscribers line, a switch individual thereto, an individual subscribers line, a party line, and a trunk line accessible to said switch,

means controlled by the calling subscriber for operating said switch to complete a 0011- nection to said individual line, said party line, or said trunk line, means automatically efiective incase' said individual. lineis connected with for ringing the called individual subscriber, means efiective in case said party line or said trunk line is connected with for preventingthe automatic application of ringing current, and subscriber controlled means for code ringing on said party line in accordance with the code of the desired called party line subscriber in case said party line is connected with or for repeating impulses over said trunk line-in case said trunk line is connected with.

8. In a telephone system, a calling subscribers line, a switch individual thereto, a called party line and an automatic switch individual thereto, said party line having a plurality of subscribers on, said line, means for operating the switch associated with-the calling line to complete. a connection to said party line, a. ringing relay in the switclrassociatedvwith said party line, andmeans in said calling switch controlled by the calling subscriber for operating saidringingrelay to apply ringing current to said party line in accordance with the code of the desired subscribe-r thereon.

9 In a telephone system, a calling sub scribers line, a switch individual thereto, acalled party line and an automatic switch individual thereto, said party line having a plurality of subscribers on said line, means for operating the switch associated with the calling line to complete a-"connectionto said party line, a ringing relay in the switch associated with said party line, means-insa-id callingswitch controlled by-the' calling subscriber for operatingsaid ringing relay to apply ringingcurrentto saidparty line in accordance with the code of the: desired subscriber thereon, and aqrin-g-cut-ofi relay in the called switch operated responsive to the removal of the receiver by the called subscriber for rendering said ringing relay inoperative.

10. In a two-motion con-necter switch-individual to a subscribefis line having a combined change-overand switclrthrough relay, a combined busy and ring-cut-ott relay, and

a ringing relay, saidzfirst relay operating as a change-over relay in order to control-said switch in its two movements and as a -switch ing relay to connect-the calling and called lines, said second relay operating as a' busy relay when saidline is a'ca-llingline and as a change-over relay in order to control saidswitch in its two movements and as a switch- 1ng relay to connect the calling and called lines,- said second relay operating as-a busy relay when said line is a calling lineand as a ring-cut-oii relay when said line is'a called line, means for operating said third relay to ring the called line when said line is the called line, and a line relay for controlling the operation ofsaid switch and for feeding talking battery to said line when it is a call ing or a called line in an established connec tion.

12. In a telephone system, a subscribers line, a connecter switch individual thereto and having apair of line wipers, attest wiper, and a ringing wiper, lines o of two classes accessible to said wipers, automatic means in said connecter for automatically transmitting grounded impulses over said ringing wiper to cause ringing current to be automatically applied to a called line in case said connecter isconnected with a line of a certain class, and subscriber controlled means "for directively transmitting ground impulses over said ringing wiper ina"cord ance with a called subscribers code to cause ringing current to be applied to the called line in accordance therewith in case the connccter is connected to a line of a different class.

13. In a telephone system, a subscribers line, a connector switch individual thereto and having a pa-ir of line wipers, a test wiper, and a ringing wiper, lines of two classes accessible to said wipers, automatic means in said connecter for automatically transmittir grounded impulses over said ringing l to cause ringingcurrent tobe autocally applied to calledline in case saconnector is connectedwith aline of a certain class, subscriber controlled means for TlllECtIVly" transmitting ground nnpulses over said ring-ing wiper in accordance with" connected to a line of a diflerent class, a

trunk line accessible to said wipers, said last nientioned means also for directively transmitting ground impulses over saidwlper to said trunk line in accordance with a called subscribers telephone number in case theconnecter is -connected to said trunlrline, and means insaid 'trunki lineior repeating'said impulses.

14. In a telephone system, a'subScribersllne, other l1nes divided anto groups, a SWltCll individual :to said line and :having accessto said oth'ervlines, subscriber controlled means for operating said switch opposite one of saidgroups and then into engagement with one of said lines in-said group, means in said switch for automaticallytransmitting ground impulses overa ringingwiperot said switch to cause ringingcurrent to be automatically-applied to the connected line in said'selected group and means effective in case said'switch' is operated opposite. a dit; ferent' group or" said lines for preventing the automatic transmission of ground impulses over, said wiper and for preparing, a circuit for directivelytransmitting ground impulses over. said wiper, responsive-to directive control from said subscribers line.

15'. In an automatic switclrindividual to a subscribers line, a line relay operated when said line isa calling ior=a called line, a release relay controlled bysaid line relay, and a cutoff relay operated-when said Eline is acalled line to prevent the operation ofsaid release relay.

16. In a telephone system, a subscribers my name this third day of January, A. D. line having a switch individual thereto, a re- 1929.

lay in said switch operated to connect up the wipers of said switch when said line is a calling line, a release relay in said switch, my name this third day of January, A. D.

CLARENCE E. LOMAX. In witness whereof, I hereunto subscribe and means for operating said first relay as a 1929.

cut-ofi relay to prevent the operation of said release relay when said line is a called line.

1?. In a telephone system, a subscribers line, a two motion switch individual to said line, a relay in said switch operated as a changeover relay to control the two movements of said switch and as a switching relay to connect the calling and called lines when said line is a calling line, a release relay in said switch, and means for operating said first relay as a cut-off relay'to prevent the operation of said release relay when said line is a called line.

18. In a telephone system, a subscribers line, an automatic switch individual thereto, and a relay in said switch operated as a changeover relay and as a switching relay when said line is a calling line and as a cutoff relay when said line is a called line.

19. In a telephone system, a calling and a called line each having a switch individual thereto, means for operating the switch associated with the calling line to complete a connection to the called line, and means in the switch associated with the called line controlled from said calling switch for applying ringing current to said called line.

20. In a telephone system, a calling and a called line each having a switch individual thereto, means for operating the calling switch to complete a connection to the called line, means in said called switch controlled from said calling switch for applying ringing current to said called line, a line relay in the called switch responsive to the answering of the call, and means controlled by said line relay for preventing further application of ringing current to the called line.

21. In a telephone system, a calling line having a switch individual thereto, two classes of called lines, each of said called lines having a switch individual thereto, means for operating said calling switch to complete a connection to a called line of either class, and means in the switch associated with the called line for applying ringing current to the called line, said means being controlled automatically from the calling switch in case the called line is of one class and controlled by the calling subscriber over the calling line in case the called line is of the other class.

In witness whereof, I hereunto subscribe my name this second day of January, A. D.

ARTHUR J RAY. In witness whereof, I hereunto subscribe LEONARD L. RUGGLES.

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