US2199534A - Telephone system - Google Patents

Description

May 7, 1940. P. BAKKER TELEPHONE SYSTEM Filed Nov. l2, 1938 E 1" Man/ZL ATTORNEY5 MR? 7 1940- P. BAKKER 2,199,534

TELEPHONE SYSTEM Find. nov. 12, 193e ssnaetssneet May 7 `1940.

P- BAKKER @Emmons sx-.STEM

3 Sheets-Sheet 3 INVENTOR,

, Fier B akker BYMWMM MM5,

ATTORNEYS.

fiatented^ May 7, Q

UNITED STATES 1PA-rem* orner.

TELEPHONE. sYs'rEM poration off Delaware Application November 12, E938, Serial No.` 239,990

26 Claims.

The present invention relates to automatic; te1e phone-systems andmoreparticularly to improved line circuits associatedvwith the lines thereof.

In an automatic telephone System, usualli7 a line circuit is individually associated with each line thereof, which line circuit conventionally comprises separate and distinct line, cut-off and .lockout relays mounted upon a supporting panel. These three relays are ordinarily so connected and arranged that the automatic switches in the system having. access to a line are controlled in accordance with` the various operations thereof to set up, by way of the line, outgoing call connections from and incoming call connections to a subscriber subst-ation associated with the line, and that the line is; marked as busy to the automatic switches having access theretov in the event a fault appearsk upon the line. Furthermore, these relays are so connected and arranged that the automatic switches in the system having access to the line are Controlled in accordance with other operations thereof to set up, by way of the line, reverting call connections between two of the subscriber substations associated with the line, in the event. the line is of the multiparty type.

While line circuits of the type briefly described above are entirely satisfactory in operation, they are more expensive to manufacture and to maintain in service than is desirable, primarily due to the fact that. three separate and distinct relays are required in each line circuit in order to render the previously mentioned services by way of the associated line. Y

In` order to reduce the manufacturing and maintenance costs of line circuits, improved line circuits disclosed in the copending application of Clarence E. Lomax, Serial No. 234,751, filed October 13, 1938, were developed. Also, in the abovefmentioned Lomax application, a combined line and cut-off relay is disclosed, which is in.- corporated in the improved line circuits disclosed therein. Briefly, the combinedv line and cut-off relay disclosed in the above-mentioned Lomax application comprises a support, line and cut-off magnets carried by the support, contact actuating members respectively associated with the magnets, a contact set operatively associated with each of the members, and. a latching arrangement for controlling the operation` of the member associated with the line magnet in two steps. The latching arrangement is controlled by the operation of the member associated with the cut-off magnet and is so constructed and ar ranged that the member associated withthe line magnet is only partially operated when the line magnet winding is energized prior to the energization of the cut-ofi magnet winding, that this member is fully operated whenthe line. magnet winding isenergized subsequent tor the energiza.-

(or. 17e-17) tion of, the.` cut-ofi magnet; Windng:,. and. that. this y .member is operated from. a partially operated position. to; a. iully operated position when the cutroi magnet: winding is energized subsequent to. and Whilethe line` magnet` winding is enersized.. The; Contact sets operatively associated these; members; are. controlled in accordance with the; various operations thereof. Alsof the line circuits' disclosed in the Dreviously mentioned Lomax application embody lineI and cut-ott magnet. control circuits,l automatic. switch. Control circuits and line markirler circuits, whichV are controlled; by the Contact sets, and which; .are so connected and arranged that the i` automatic switches in` the system are controlled thereby to render, by way of a subscriber line. with, which the` linecircuit is, associated, calling,v called and reverting callv services to the subscriber substations associated with the sub scriber line.

Although. the improvements as disclosed in the previously mentioned; Lomax application considerably reduce the manufacturing and maintenance costs of line circuits, further reductions in these costs are desirable` and. may be realized byv further simplifying ,the` various circuits embodied in. the line circuits and by employing in the line circuits improved combined line and cutoi relays of the construction and arrangement disclosed in the copendingA application of John E. Ostline, Serial No.,240,00l, led November l2, 1938. y The combined. line and cut-ofi vrelay disclosed in the above-mentioned" Ostl'ine. application cornprises a sup-port, line and" cut-oli. magnets carried by the. support,` a movable contact actuating member operatively associated with the line magnet', a, movable contact actuating member operatively associated. with the cut-oir. magnet, arst contactl set operatively associatedV with the first-mentioned member, a second contact set operatively associated with the second-mentioned member, a third contact set, and mechanical means for operatively associating the third contactsetwiththe first-mentioned member. Each of the Contact sets has a, normal position and is 'movable away from its normal position iny response to the operation ofthe oneof the members `with which it is operatively associated. Also, the combinedv line and, cut-oliiv relay comprises means vfor biasing4 each ot the contact sets to its normal position, and means, controlled by the. operation of the second-mentioned member for releasing the mechanical` means, whereby the third contact set isno-t moved away from its normalV position in. the event the first-mentioned member isl operated subsequent to the operation of the secondrmentioned member andthe third,v contact set is returned' to. its normal positionv in the eventthe second-mentioned member is operated subsequent to the operation of the first-mentioned member. Also, the mechanical means is reset when both of the members are restored.

Accordingly, it is an object of the present invention to provide an improved line circuit adapted for use in an automatic telephone system which comprises line and cut-oi relays, which two relays are connected and arranged in an extremely simple manner and so related that the automatic switches in the system are controlled thereby to render, by way of a subscriber line with which the line circuit is associated, calling, called and reverting call services to the subscriber substations associated with the subscriber line.

It is another object of the invention to provide an improved line circuit of the type described adapted for use in an automatic telephone system. which is extremely economical to manufacture and which is positive in operation in order to control the automatic switches in` the system in a thoroughly reliable manner, whereby the desired services may be rendered to the subscriber substations associated with the subscriber lines in the system.

A further object of the invention is to provide an improved automatic telephone system in which there are incorporated improved line circuits of the type described, each including an improved combined line and cut-off relay of the construction noted.

The features of the present invention are illustrated as being incorporated in an automatic telephone system including a plurality of subscriber lines, some oi the lines being of the multiparty type, each line having an improved line circuit of the type described incorporating an improved combined line and cut-01T relay of the construction noted individually associated therewith, and a number of nder-connector links for setting up connections between the various lines. A number of subscriber substations are associated with each oi the lines oi the multiparty type; and a distributor of the preselective type is provided for the purpose oi assigning idle ones of the links to the use of calling ones of the lines in a predetermined order.

In accordance with one feature of the invention, the line circuit is adapted for use in an automatic telephone system including a line accessible to an automatic switch and comprises, in combination, line and cut-off relays, a rst contact-set operatively associated with the line relay, a second contact set operatively associated with the cut-off relay, a third co-ntact set, and means normally eiective operatively to associate the third contact set with the line relay, each of the contact sets having a normal position and being operative away from its normal position in response to the operation of the one of the relays with which it is operatively associated. Also, the system comprises means responsive to the creation of a calling condition on the line for causing the line relay to be operated, means responsive to the seizure of the line by the automatic switch for causing the cut-off relay to be operated, means controlled by the operation of the cut-o relay for rendering the rst-mentioned means ineiective, means controlled by the operation of the second contact set away from its normal position for causing the line relay to be operated, and automatic switch control circuits and line marking circuits governed by the contact sets. More particularly, the means which is normally effective operatively to associate the kline marked as a calling line.

third contact set with the line relay comprises a blocking or latching element which is tripped when the cut-E relay is operated. Furthermore, means is provided for biasing each of the contact sets to its normal position, whereby the third contact set is not operated away from its normal position in the event the line relay is operated subsequent to the operation of the cutoi relay and the third contact set is returned to its norma-1 position in the event the cut-oi relay isoperated subsequent to the operation of the line relay. Finally, the latching element is reset when both of the line and cut-off relays are restored.

In accordance with another feature of the invention, a telephone system is provided which comprises a line, a number of nder and connector switches having access to the line, a line circuit of the connection and arrangement described associated with the line, and a distributor associated with the nder switches and operative to cause an idle one of the nder switches to operate and seize a line marked as a calling line. Also, the system comprises means responsive to the creation of a calling condition on the line for causing the line relay to be operated, means controlled by the operation of the iirst and third contact sets away from their normal positions for initiating operation of the distributor and for marking the line as a calling line, means responsive to the seizure of the line by one of the iinder switches for causing the cutoi relay to be operated, and means controlled by the operation of the cut-oft relay for releasing the latching element, whereby the third contact set is returned to its normal position. Furthermore, the system comprises means controlled by the operation of the second contact set away from its normal position. for causing the line relay to be retained operated, means controlled by the return of the third contact set to its normal position for arresting the operation of the distributor, means for releasing the one finder switch, means responsive to the release of the one finder switch for causing the cut-oli relay to be restored, means controlled by the return of the second contact set to its normal position for causing the line relay to remain operated in the event a calling condition remains on the line, and means controlled when the first contact set is operated away from its normal position and the second contact set is returned to its normal position for marking the line as busy to the connector switches.

In accordance with a further feature of the invention, the telephone system comprises means controlled by the operation of the iirst contact set away from its normal position for marking the line as busy to the connector switches and signal means controlled when the iirst contact set is operated away from its normal position and the second and third contact sets are returned to their normal positions.

In accordance with a further feature of the invention, the telephone system comprises a line, a plurality of subscriber substations associated with the line, a number of iinder-connector links having access to the line, a line circuit of the connection and arrangement described associated with the line, and a distributor associated with the links and operative to cause the finder switch of an idle one oi the links to operate and seize a Also, the system comprises means responsive to the creation of a calling condition on the line for causing the line dream4 relay to be operated, means controlled by the operation of the first and second contact sets away from their normal positions for initiating operation of the distributor and for marking the line a calling line, means responsive to the seizure of the line by the iinder switch of the one link for causing the cut-o relay to be operated, and means controlled by the operation of the cut-off relay for releasing the latching element, whereby the third contact set is returned to its normal position. Furthermore, the system comprises means controlled by the operation of the second contact set away fromits normal position for causing the line relay to be retained operated, means controlled by the return of the third con.- tact set to its normal position for arresting the operation of the distributor, impulse responsive means included in the selector switch of the one link and operative to cause ringing current to` be projected by way of the one link over the line subsequent to the termination of the calling condition thereon and to cause the line relay to remain operated, and means responsive to the answering of the call at a called one of the substations for causing the one link to be released and for creating a new calling condition on the line'. Finally, the system comprises means responsive to the release of the one link for causingr the cutoif relay to be restored, means responsive to the creation of the new calling condition on the line for causing the line relay to remain operated subsequent toI the return of the second contact set to its normal position, and means controlled when the rst contact set is operated away from its normal position and the second contact set is returned to its normal'position for marking the line as busy to the connector switches of the links.

Further features of the invention pertain to the particular arrangement of the circuit elements thereof, whereby the above-outlined and additional features are attained.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the follo-vving specication taken in connection with the accompanying drawings in which Figs. 1 and 2, taken together, illustrate diagrammatically a telephone system including improved line circuits and embodying the present invention; Fig. 3 is a perspective view of a combined line and cut-oif relay adapted to be incorporated in the line circuits shown in Fig. l; and Fig. 4 illustrates diagrammatically the arrangement of the switch springs associated with the combined line and cut-off relay when it is incorporated in theline circuits shownin Fig. l.

Referring now more particularly to Figs. 1 and 2 of the drawings, the telephone system there illustrated comprises an exchange having a piurality of subscriber lines including the subscriber lines and IBB terminating thereat, and provided with a plurality of finder-connector links including the link ISEF for setting up connections between the various subscriber lines. Also a distributor H33 is provided for assigning idle ones of the links to the use of calling ones of the subscriber v lines; and a number of reverting call switches, including the reverting call switch 201i, are provided for the purpose of projecting code ringing current over a subscriber line when a reverting call is initiated thereon. More specifically, the exchange has an ultimate capacity of one hundred lines, and the number of links isdetermined by the amount of traiilc which the exchange is required to handle, usually ten links being adequate to render satisfactory service.

Each of the links may be identical to the link IEB which comprises a finder-portion or switch lili and a connector portion or switch W2, each having access to each subscriber line in the system. The finder switch and the connector switch included in each link may be one of any of a number of well-known types. However, it is preferable that each of these switches includes a switching mechanism of the Strowger type and the usual control apparatus therefor, the wipers of the switching mechanism included in the finder switch lill being illustrated at ISEL'lBi and |82, and the wipers of the switching mechanism included in the connector switch 182 being illustrated at i253, 186i and |85. Also the connector switch m2 comprises impulse responsive apparatus of any desired type for projecting code ringing current over an idle called subscriber line after it has been seized by the switching mechanism included therein, which is so conf.

nected and arranged that a divided ringing circuit may be employed in the system. The `distributor H33 may be one of any of a number of well-known types. However, it is preferable that the distributor |03 is of the preselective type, such that an idle link is selected to be assigned to the use of a calling line prior to the initiation of a call on the line.

At least a number ci the subscriber lines terminating at the exchange are of the party type, the subscriber lines l and it) being party lines, each serving a number of subscriber substations, respectively, including the subscriber substations A, B and C, D. Each of the subscriber substations is provided with atelephone instrument, a dial mechanism, and a ringer. The subscriber substations associated with each party lineare arranged in two groups, the ringer at each substation in the first group beingl connected between one line conductor of the subscriber line and ground, and the ringer at each substation in the second group being connected between the other line conductor of the subscriber line and ground, whereby a divided ringing circuit is .employed in the system.

A line circuit is individually associated with each subscriber line in the system, the line circuit mit being individually associated withv the subscriber line ld, and the line circuit lii being individually associated with the subscriber line itil. The line circuit IM comprises a combined line and cut-oir relay including a line magnet or relay RIZG and a cut-off magnet or relay Rl i0; and the line circuit MI5 comprises a combined line and cut-off relay including a line magnet or relay Ridi! and a cut-01T magnet or relay RiSil. Preferably, the line circuits are of identical connection and arrangement, each comprising `a combined line and cut-ofi relay of the construction and arrangement of that disclosed in the previously mentioned copending lOs'tline application and shown in FigS. Also, each of the combined line and cut-off relays includes a switch spring assembly of the construction and arrangement shown in Fig. 4.

Each of the reverting call switches' may be identical to the reverting call switch 20B which comprises two minor switches 23d and 29B, a line relay R2 30, a hold relay RZ-tk), two transfer relays R260 and R270, a ring cut-oit relay R255, aswitchyms Y 'ing-through relay' R228, two control relays RZIU vand R258, the control and controlled circuits therefor, and a transformer 28|. The minor switch 280 comprises two rotary switches 28| and 282 provided with Contact banks 234 and 286, respectively, and associated wipers 283 and 285, respectively, a rotary magnet M233 for simultaneously rotating the wipers of the rotary Aswitches 28| and 282, and a release magnet M231 for releasing the wipers of the rotary switches 28| and 282 and for causing these Wipers to be returned to their normal positions. Also two switch springs 238 are associated with the wipers of the rotary switches 28| and 282, which are actuated into engagement when these wipers are rotated by the rotary magnet M236 away 'from ,their normal positions. The minor switch 299 Acomprises two rotary switches 29| and 292 provided with contact banks 294 and 299, respectively, and associated wipers 293 and 295, respectively, a rotary magnet M238 for simultaneously rotating the wipers of the rotary switches 29| and 292, and a release magnet M239 for releasing the wipers of the rotary switches 29| and 292 and for causing these wipers to be returned to their normal positions. Also two switch springs 235 are associated with the wipers of the rotary switches 29| and 292, which are actuated into engagement when these wipers are rotated by the rotary magnet M238 away from their normal positions. Also it is noted that the reverting call switch 288 is connected and arranged to project code ringing current over a calling subscriber line by way of the trunk line |18 when a connection is established therebetween by way of an operated one oi the links, in such a manner that a divided ringing circuit may be employed in the system.

As best shown in Fig. 3 of the drawings, the

A combined line and cut-01T relay which is incorporated in each of the line circuits employed in the system comprises a supporting plate including two portions 38| and 382 suitably secured together by an arrangement including a strap 383 and an outwardly extending plate 394. The portions 38| and 382 of the supporting plate respectively carry line and cut-01T magnets 385 and 389arranged in spaced parallel relationship with respect to each other and to the corresponding portions of the supporting plate, each being provided with a suitable energizing winding. Also, the magnets 385 and 386 are arranged closelyadj acent to each other and comprise, together with the portions 38| and 382 of the supporting plate, a unitary structure. A supporting bracket 381 provided with two upwardly extending arms 388 carrying a pivot pin 389 is secured to the upper portion 38| of the supporting plate by an arrangement comprising a screw 318 and a washer 3| I; and a supporting bracket 3|2 provided with two upwardly extending arms 3|3 carrying a pivot pin 3M is secured to the upper portion 382 of the supporting plate by an arrangement comprising a screw 3I5 and a washer 3|9. An armature 3|'l provided with two rearwardly extending arms 3|8 is pivotally supported on the pivot pin 389 adjacent the pole face of the core of the line magnet 385; and an armature 3|9 provided with two rearwardly extending arms 328 is pivotally supported on the pivot pin 3M adjacent the pole face of the core of the cut-off magnet 388. The armature 3H is provided with a downwardly extending arm 32| having a rearwardly projecting finger 322 on the outer end thereof extending to the rear of the portion 38| ofthe supporting plate adjacent the right-hand edge thereof; and the armature 3|9 is provided .with a downwardly extending arm 323 having a rearwardly projecting finger 324 on the outer end thereof extending to the rear of the portion 382 of the supporting plate adjacent the right-hand edge thereof. Two contact sets or switch spring assemblies 325 and 325, each comprising a plurality of individual flexible switch springs suitably insulated from each other and from the portion 38| of the supporting plate, are secured to the rear side of the portion 38| of the supporting plate and cooperate with an insulating button 321 carried by the nger 322 in such a manner that the individual switch springs in these switch spring assemblies are actuated into engagement and disengagement with each other in a predetermined manner, when the armature 3H is rotated about the pivot pin 389. Also, a contact set or switch spring assembly 328, comprising a plurality of individual flexible switch springs suitably insulated from each other and from the portion 382 of the supporting plate, is secured to the rear side of the portion 382 of the supporting plate and cooperates with an insulating button 329 carried by the finger 324 in such a manner that the individual switch springs in this switch spring assembly are actuated into engagement and disengagement with each other in a predetermined manner, when the armature 3|3 is rotated about the pivot pin 3M.

More particularly, the switch spring assembly 325 comprises a spring 339 provided with a flexible rearwardly extending flange or latching element 33| which normally abuts or engages the upper portion of a spring 332 included in the switch spring assembly 326. Accordingly, when the armature 3|? is rotated in a clockwise direction about the pivot pin 389, as viewed in Fig. 3, the insulating button 32T carried by the iinger 322 engages the spring 338 and flexes the upper portion thereof rearwardly. This rearward movement of the spring 338 actuates the individual switch springs included in the switch spring assembly 325 into engagement and disengagement with each other in a predetermined manner more fully described subsequently. Furthermore, the flange 33| provided on the upper portion of the spring 338 engages the upper portion of the spring 332 and flexes the upper portion thereof rearwardly. This rearward movement of the spring 332 actuates the individual switch springs included in the switch spring assembly 328 into engagement and disengagement with each other in a predetermined manner more fully .described subsequently. When the armature 3| 9 is rotated in a clockwise direction about the pivot pin 3M, as viewed in Fig. 3, the insulating button 329 carried by' the linger 324 engages a switch spring 333 ineluded in the switch spring assembly 328 and fleXes the upper portion thereof rearwardly. This rearward movement of the switch spring 333 acytuates the individual switch springs included in the switch spring assembly 328 into engagement and disengagement with each other in a predetermined manner more fully described subsequently.

As previously noted, the switch spring assemblies 325 and 328 are normally simultaneously actuated away from their normal positions by the movement of the armature 3H. However, an arrangement is provided for rendering the actuation of the switch spring assembly 325 independent of the actuation of the switch spring assemadjacent the upper portion thereof bly 326 and for releasing the switch spring asprising a bearing portion rotatably secured between the rear wall of the portion 302 of the supporting plate and a tab 335 formed integral with the strap 303 and arranged closely adjacent to the rear wall of the portion 3D2 of the supporting plate. Furthermore, the rocking bar 333 comprises an outwardly and downwardly extending arm 336 arranged in the path of movement of the arm 323 carried by the armature 3I9 and an outwardly and rearwardly extending arm 33? arranged beneath the flange 33I provided on the upper portion of the spring 333 included in the switch spring assembly 325. When the'armature 3I9 is rotated in a clockwise direction about the pivot pin 3M, the arm 323 thereon engages the arm 336 on the rocking bar 236, thereby to cause the rocking bar to be rotated in a clockwise direction upon its bearing, as viewed in Fig. 3. When the rocking bar 334 is rotated in a clockwise direction upon its bearing, the arm 33T thereof engages the ange 33I provided on the upper portion of the spring 330 included in the switch spring assembly 325 and flexes the flange 33I upwardly and out of abutting relation with the upper portion of the spring 332 included in the switch spring assembly 32E. At this time, if the armature 3II occupies a non-operated position and is subsequently operated, only the switch spring assembly 325 will be actuated. However, if the armature 3H occupies an operated position, the switch spring assembly 32B will be released and returned to its normal position due to the fact that the outer end of the flange 33I provided on the upper portion of the spring 33D is flexed out of abutting relation with the upper portion of the spring 332. Thus, it will be apparent that in the event the winding .of the line magnet 335 is energized prior lto the energization of the winding of the cut-0E magnet 335, the switch spring assemblies 325 and 326 are simultaneously actuated away from their normal positions. However, in the event the winding of the cut-ofi magnet 335 is energized prior to the winding of the line magnet 335, only the switch spring assembly 325 is actuated upon the energization of the winding of the line magnet 335. Finally, in the event that-the winding of the cut-oir magnet 305 is energized subsequent to the energization of the winding of the line .magnet 335, the switch spring assembly 323 is released and returned to its normal position when the winding of the cut-oir magnet is energized. The switch spring assembly 328 is actuated away from its normal position directly in .accordance with the energization of the winding of the cut? off magnet 33t and the actuation thereof is independent of the sequence of energizing the windings of the line and cut-off magnets 335 and 333, respectively.

Referring now more particularly to Fig. fi of the drawings, it will be observed that the switch spring assemblies associated with the line `and cut-oir magnets R123 and RI I 0, respectively, corresponding to the switch spring assemblies incorporated in the line circuit IM, are so constructed and arranged that, when the line magnet RIQD is energized, the armature indicated at 3ia is rotated in a clockwise direction about the pivot pin 339e, thereby to cause the insulating button 327e carried thereby to ex the upper portion of the .spring 33Go. This movement of the spring 330e ,is eiiective to actuate the switch spring assembly 325e, thereby to move the switch springs RAI25 and RCI25 into engagement, yto move the switch springs RAIZI and RCI22 into disengagement, and to move the switch springs RAIZI and RCI23 into engagement. Also, this movement of the spring 333e causes the flange 33Ia carried by the upper portion thereof to engage the spring 332a included in the switch spring assembly 326e, thereby to actuate the latter switch spring assembly. This actuation of the switch spring assembly 326e is effective to move the switch springs RAI26 and RCI23 intodisengagement, to move the swtich springs `RAI23 and RCI2I into engagement, and to "move the switch springs RAiM and RCIZIi into engagement. This movement of the switch springs RAIZi, RCIM and RAI26, RCI'Z'I is effective tov close the R contacts associated therewith; and this movement of the switch springs RAIZB, RCIZSv is eiective to open the Rv contacts asso ciated therewith. Subsequently, when the cut.`

ofi magnet RI III is energized, the armature indicated at 3| 9a is rotated in a counterclockwise direction about the pivot pin' llia, thereby to cause the insulating button 3290, carried thereby to vengage the switch spring 333e included in the switch spring assembly 328e and iiex the upper portion thereof, thereby to actuate the individual switch springs included in this switch spring assembly. 'This movement of the switch spring 333e is eiiective to move the switch springs RAI Il! and RCIM into engagement, thereby to close the X contacts associated therewith. Subsequent movement of the switch spring 333e is effective to move the switch springs RAI I3 and' RCII3 into disengagement, to move the switch move the switch springs RAI I2 and RCI I2 into engagement, to move theswitch springs RAIlii and RAI i-'I into engagement, and finally, to move the switch springs RAI Il and RCI Il into dischgagement. Final movement of the switch spring 3330I is eiiective tov move the switch springs RAI I-I and RCIII into disengagement, thereby to open the lY contacts associated therewith.

Also, when the armature 3l9a is rotated in a counterclockwise direction about the pivot 'pin 3I4a, the arm 336e of the rocking bar 333e is engaged, thereby to cause the rocking bar to be rotated in a clockwise direction about its pivot. This `rotation of .the rocking 4bar 333e is veffective to cause the arm 33M thereof to flex the outer end of .the ange 33m provided on the upper portion of the spring 333e included in the switch spring `assembly 3250. out of engagement with the upper portion of the spring 33211. included in the switch spring assembly 326e; The switch spring assembly 326e is then released and the individual switch springs thereof are actuated to their normal positions, therebyto move the switch springs RAIN, RCIM and RAIZB, RCI2'I into disengagement and to move the switch springs RAIZE, RCI28 into engagement. Also, it is .noted that in the event the cut-off magnet RI Ill is energized prior to the energization of the line .magnet RI 23,

switch spring assemby 326er. Accordingly, when the line magnet RIZ@ is then energizedonly the switch spring assembly 325a is actuated. in the previously described manner.

The connection and arrangement of the system will best be understood from a consideration of the following description, with reference tol Figs. 1 and 2 of the drawings, of the operation of the apparatus incorporated therein to set up the different connections between the variousv subscriber lines.

. completed between the line conductors of the subscriber line |50, a bridge circuit is completed for energizing in series the upper and lower windings of the line magnet RI20 in the line circuits I04 individually associated with the subscriber line |50, which extends from battery at the upper winding of RI20 by way of the upper winding of RI20, RAI I I, RCI I I, CI5I, the bridge path at the substation A between CI5I and CI52, CI52, RCIIl, RAIIl and the lower winding of RI20 to ground. When energized over the abovetraced circuit, the line magnet RI20 operates, thereby to actuate the two switch spring assemblies associated therewith in order to close the R contacts associated with the switch springs RAI24, RC|24 and RAIZB, RCI21, and to open the R contacts associated with the switch springs RA|26 4and RCI28. More particularly, the line magnet RIZ@ completes, at RAI25 and. RCI25 and at RAIEB and RCI21, a path for applying ground potential to the start conductor CISi) extending into the distributor I 03, this path extending from ground at RCI I5 by way of RAI I5, RCI25, RAI25, RAIZS, RCI21 and CISI to the start conductor C |90. This application of ground potential to the start conductor CISU initiates the operation of the distributor |03 and causes the distributor to operate and assign the previously selected idle link to the use of the calling subscriber line |50. Assuming that the illustrated link |00 is assigned by the distributor I 03 to the use of the calling subscriber line |50, the distributor also marks with ground potential by way of the conductor CI 93 the level in the contact bank of the Strowger mechanism included in the finder switch 0|, wherein the calling subscriber line |50 terminates. Also, the line magnet RI20 completes, at RAI2|| and RCI24, a path for applying battery potential to the control conductor C |53, this path extending from battery at the upper winding of the cut-01T magnet RIIIl' by Way of the upper winding of Rl I0, RAIM and RCI21! to thc control conductor CI53. This application of battery potential to the control vconductor CI53 marks the radial position of the contact set in the level in the contact bank of the Strowger mechanism included in the nder switch wherein the subscriber line |50 terminates. Further, the line magnet R|20 completes, at RAI2| and RCIZ3, a path for applying ground potential to the control conductor CI 54 of the subscriber line |50 extending to the contact banks of the Strowger mechanisms included in the connector switches of the links having access thereto, thereby to mark the subscriber line |50 as busy thereto immediately and prior to the time the finder switch |01 of the link |00 operates to seize this subscriber line, this path extending from ground at RCII3 by way of RAII3, RC|23 and RAIZI to the control conductor CI54.

The Strowger mechanism included in the nder switch lill then operates to move the wipers |80, I8| and |82 thereof in the vertical direction to the level wherein the calling subscriber line |50 terminates. This Strowger mechanism then operates to move the wipers thereof in the radial direction to the radial position of the contact set wherein the calling subscriber line |50 terminates, at which time the wipers |30 and |82 thereof engage the contacts terminating the line conductor C|5| and CI52, respectively, and the wiper |8| engages the contact terminating the control conductor CI53 of the calling subscriber line |50. The presence of battery potential upon the control conductor C|53 completes a circuit for energizing a relay in the finder switch |0I operative to arrest further operation of the Strowger mechanism included therein, which relay also operates to complete a path for applying ground potential to the wiper 58 I. This application of ground potential to the wiper ISI completes a circuit for energizing in multiple the upper and lower windings of the cut-off magnet RIIO. This circuit extends from the grounded wiper |8I by way of the contact terminating the control conductor CI53 to CI53, one branch of this path extending from CI53 by way of RCIZA, RAI 24 and the upper winding of RI I0 to battery, and the other branch of this path extending from CI53 by way of RAII4, RCII4 and the lower winding of RIIO to battery. Also, this application of ground potential to the wiper I 8| prepares a path, traced hereinafter, for applying ground potential to the control conductor` CI54 of the subscriber line |50 extending to the contact banks of the Strowger mechanism included in the links of the connector switches having access thereto, thereby subsequently to mark the subscriber line |50 as busy to the connector switches of these links. When energized over the above-traced circuit, the cut-olf magnet RI I0 operates to complete, at RAI IIS and RAI I'l, a holding circuit for energizing the lower winding of the line magnet RIZIJ, this circuit extending from battery at the resivstor |51 by way of the resistor |51, RAII6. RAI I1 and the lower winding of RI20 to ground.

Also, the cut-ofi magnet RII!! interrupts, at

RAII'I and RCI|`| vand at RAIII and RCIII, points in the `original bridge circuit for energizing the upper and lower windings of the line magnet RI 20, thereby to free the line conductors CI 5I and C|52 of the subscriber line |50 of impedance elements. Further, the cut-off magnet completes, at RAII?! and RCII2, and at RAIN and RCI I4, the previously mentioned path for applying ground potential to the control conductor CI54, this path extending from the grounded wiper I8| by way of the contact terminating the control conductor CI53, CI53, RAII4, RCIM, RAI I2 and RCI l2 to the control conductor CI54. Further, the cut-off magnet RI I0 interrupts, at RAII3 and RCIIS, a point in the previously traced path for applying ground potential at RC! I3 to the control conductor CI54 and interrupts, at RAI I5 and RC'II5, a point in the previously traced path for applying ground potential at RCII5 to the start lead CI90 extending into the distributor |03. Also, upon operating, the cut-off magnet RIIil releases the latching arrangement for retaining the restoring switch spring assembly associated with the line magnet R12!! in its actuated position, 'thereby -to allow the individual switch springs included in this switch spring assembly to be returned to their normal positions. More particularly, the switch springs RAl2ll and RCl2Ll are moved into disengagement,

thereby to open the R contact associated therewith; and the switch springs RAlZB and RClZ'i are moved into disengagement, thereby to open the R contact associated therewith. Finally, the switch springs RAIZB and RCIZB are moved into engagement, thereby to close the R contact associated therewith. Whenl the R contact associated with the switch springs RANA and RCIM y is opened, the previously traced circuit for enerv er winding thereof.

' gizing the upper winding of the cut-oit magnet RIID is interrupted, this magnet being retained in its operated position at this time due to the completed holding circuit for energizing the low- When the R contact associated with the switch springs RAIEB and RC`I2'i is opened, a further point in the path for applying ground potential to the start lead CI Sil extending into the distributor lll?, is interrupted, and when the R contact associated with the v switch springs RAi 2@ and RClZ is closed, a point in a. circuit, traced hereinafter, is prepared for applying ground potential to the control conduct-or CIBG extending to a permanent alarm device. Also, at this time, the line magnet Rl2tl remains in its operated position due to the corn-v pleted holding circuit for energizing the lower winding thereof. When ground potential is removed from the start conductor Cl9 extending into the distributor EES, the distributor H33 operates to'select an idle link in the group of links to be assigned to 'the use of the next calling subscriber line, and when the finder switch I lll seizes the calling subscriber line Ille, the connector switch EQ2 operates to condition the Strowger mechanism included therein to be responsive to dialed digits.

The subscriber at the substation A then dials the first digit of the directory number of vthe called subscriber line at the dial mechanism thereat, thereby to transmit a rst series of 'impulses over the loop circuit extending by way of the subscriber line 15% between the substation A and the connector switch m2. Impulse responive apparatus in the connector switch MIZ operates in response to this iii-st series of impulses in order to cause the wipers ISS, iSd, and IS5 olthe Strowger mechanism included therein to be moved in the vert-ical direction to the level in the contact bank therein, wherein the called subscriber line ISB is terminated. The subscriber at the substation A then dials the second digit of the directory number of the called subscriber line at the dial mechanism thereat, thereby to transmit a second series of impulses by way of the previously mentioned loop circuit to the connector switch lili? in order to cause the wipers noted of the Strowger mechanism included therein to be moved in the radial direction to the position of the contact set in the contact bank. therein, wherein the called subscriber line I6!) is terminated. The subscriber at the substation A then dials the vthird digit of the Vdirectory number of the called substation C at the dial mechanism thereat, thereby to transmit a third series or impulses b-y Way of the previously mentioned loop circuit to the connector switch le? in order toA At lthis time the lwipers |83 and .E85 engage the contacts in the contact bank terminating the line conductors Cii and CM2, respectively, and the wiper IM engages the contact-in the contact bank terminating the control conductor CI G3 of the called subscriber line Id. At this time ground potential appears upon the control conductor CI63 in the event the called subscriber line i60 is busy. On the other hand, battery potential appears upon the control conductor Clll in the event the called subscriber line i60 is idle.

Assuming that the called subscriber line I6 is busy, ground potential derived in the line circuit m5 appears upon the control conductor CI63 thereof, thereby to complete a path for energizing a busy relay included in the connector switch It?, which busy relay operates to cause busy tone current to be returned over the loop circuit eX- tending to the c'alling'subscriber substation A., in the usual manner. The production of busy tone in the receiver of the telephone instrument at the calling substation A indicates to the subscriber thereat that the desired connection cannot immediately be had due to the busy condition of the called subscriber line IEB. The subscriber at the calling substation A then releases the operated link Iill and the line circuit 9M by replacing the receiver of the telephone instrument at the substation A upon its hook. The exact manner in which these operated pieces of apparatus are released is described in detail hereinafter.

Assuming that the called subscriber line It@ is idle, battery potential appears upon the con trol conductor Cieli thereof, this battery potential being derived at 'the lower winding of the cutol magnet RIMi and extending 'therefrom by way' of the lower winding of RIBU, RCifl'Z and RAIG'I to the control conductor C163. This application 'of battery potential to the control conductor C563 completes a path for shor't-circuiting the busy relay 'included in the connector switch llZ, thereby to cause the connector switch m2 to opera't'e and project ringing current of 'the previously selected code over the called subscriber line I 6E in order to cause the ringer at the substation C to operate in a characteristic manner. This characteristic operation 'ci the ringer at the substation C indicates to the subscriber'thereat that the substation C is the called substation. Also, a switch-through relay in the connector switch Iil2 operates to apply direct ground potential to the wiper ist. This application of direct ground potential to the wiper it completes a circuit for energizing the lower winding or the cut-ofi magnet Rls'l, this circuit extending from the grounded wiper ltd by way of the contact terminating 'the control' conductor CIEM, C'l', RAIdI, RClll and the lower winding of R to battery. When energized over the above-traced circuit, the cut-oir magnet Rist operates to complete, at RAIEZ and RCE-32, a holding circuit for energizing the lower winding thereof, this circuit oxtending from the grounded control con ductor CIS?) by way of ROSSE, RAISE and the lower winding of Ried to battery. Also, the cutoi magnet Ritt completes, at RAll and RC'IM, a path for applying ground potential to the control oonductor Cite of the subscriber line ISU extending to the contact banks of the Strowger mechanisms included in 'the' uder switches of the links having access thereto, thereby to mark the subscriber .line itil as busy thereto, this path extending .from the grounded control conductor to the control conductor C164. Further, the cutol magnet R|30 interrupts, at RA|33 and RCI33, a path in the circuit for applying ground potential to the control conductor C|63 when the line magnet RI40 operates, and interrupts, at RAI35 A and RCI35, a point in the path for applying ground potential to the start conductor C extending into the distributor |03. Finally, the cut-01T magnet R|30 interrupts, at RAI 3| and RCI3| and at RAIS'I and RCI3I, points in the bridge circuit for energizing the upper and lower windings of the line magnet R|40 and completes, at RA|36 and RAI3l, a holding circuit for energizing the lower winding of the line magnet R|40, this holding circuit extending from the battery at the resistor IGT by way of the resistor IB'I, RAISE, RAISI and the lower winding of R|40 to ground. Also, upon operating, the cutoi magnet R|30 releases the latching arrangement for causing the two switch spring assemblies associated with the line magnet R|40 to be actuated simultaneously.

When energized over the above-traced circuit, the line magnet R|40 operates to actuate only the switch spring assembly directly associated therewith, thereby to interrupt, at RAI4| and RC |42, a point in the previously traced original circuit for energizing the lower winding of the cut-01T magnet R|30. 'I'he subscriber at the substation C then answers the call by removing the receiver of the telephone instrument thereat from its hook, thereby to cause the connector switch |02 to operate in order to interrupt the projection of ringing current over the called subscriber line and to complete an established communication connection between the calling subscriber line |50 and the called subscriber line |80 by way of the operated link |00.

Assuming that the release of this' established connection is under the control of the last subscriber to replace the receiver of the telephone instrument at his substation upon its hook, when the last subscriber at one of the substations replaces the receiver of the telephone instrument thereat upon its hook, the operated link |00 is released in the usual manner, thereby to interrupt the established connection extending between the subscriber lines |50 and |50. When the link |00 is released, ground potential therein is removed from the wiper lI, thereby to interrupt the previously traced holding circuit for energizing the lower winding of the cut-ofi magnet RI I0. The cut-off magnet RI I0 then restores to interrupt, at RAI I4 and RCI I4, a further point in the holding circuit for energizing the lower winding thereof and a point in the path for applying ground potential to the control conductor C I 54 extending to the contact banks of the Strowger mechanisms included in the connector switches of the links having access thereto. Also, upon restoring, the cut-off magnet R! I0 interrupts, at RAII2 and RCI I2, a further point in the previously traced path for applying ground potential to the control conductor CI54, prepares, at RAI I3 and RCI I3, a point in the previously traced path for applying ground potential, at RCI I3, to the control conductor CI 54, and prepares, at RA||5 and RCII5, a point in the previously traced path for applying ground potential, at RCI I5, to the start co-nductor CI 90 extending into the distributor |03. Finally, the cut-oi magnet RI I0 interrupts, at RAI I6 and RAI Il, a point in the previously traced holding circuit for energizing the lower winding o the line magnet RI and prepares, at RAII'I and RCI and at RAIII and RCIII, points in theI previously traced bridge circuit for energizing the upper and lower windings of the line magnet RI20.

The line magnet RI20 then restores to complete, at RAIZI and RCI 22, the previously traced path for applying battery potential, at the lower winding of the cut-01T magnet RI I0, to the control conductor C154. extending to the contact banks of theV Strowger mechanisms included in the connector switches of the links having access thereto, thereby to mark the subscriber line |50 as idle. Also, the line magnet RI20 interrupts', at RAI 2| and RCI23, a point in the previously traced path for applying ground potential, at RCI I3, to the control conductor C|54 and interrupts, at RA| and RCI25, a further point in the previously traced path for applying ground potential, at RCI I5, to the start conductor CI90. Finally, the line magnet RI20 interrupts, at RA|25 and RCI 25, a point in a path, traced hereinafter, for applying ground potential to the control conductor C|56 extending to a permanent alarm device. Also, it is noted that when both the cut-ofi magnet R||0 and the line magnet RI20 restore, the latohing arrangement for causing the two switch spring assemblies associated with the line magnet RI20 to be actuated simultaneously is reset. At this time the subscriber line |50 is marked as idle to the nder and connector switches of the links having access thereto and the line circuit |04 is completely released.

Also, when the link |00 is released, ground potential therein is removed from the wiper |84, thereby to interrupt the previously traced holding circuit for energizing the lower winding of they cut-off magnet R|30. The cut-off magnet R| then restores, thereby to interrupt, at RA|32 and RCI32, a further point in the holding circuit for energizing the lower winding thereof and a point in the previously traced path for applying ground potential to the control conductor C104 of the subscriber line |60 extending to the contact banks of the Strowger mechanisms included in the nder switches of the links having access thereto, thereby to mark the subscriber line |60 as idle. Also, the cut-off magnet R|30 interrupts, at RAI34 and RCI34, a further point in the previously traced path for applying ground potential to the control conductor CIB4. Further, the cut-off magnet R|30 prepares, at RAI33 and RCI33, a point in the path for applying ground potential, at RC 33, to the control conductor C163 of the subscriber line |00 extending to the contact banks of the Strowger mechanisms included in the connector switches of the links having access thereto, and prepares, at RAI35 and RCI 35, a point in the path for applying ground potential, at RCI35, to the start conductor C190 extending to the distributor |03. Finally, the cut-off magnet R|30 prepares, at RAI3| and RC|3I and at RAI3I and RCISI, points in the bridge circuit for energizing the upper and lower windings of the line magnet R| and interrupts, at RAI 36 and RAI3'I, a point in the previously traced holding circuit for energizing the lower winding of the line magnet RI40.

The line magnet R|40 then restores to complete, at RAI4I and RCI42, a point in the previously traced path for applying battery potential, at the lower winding of the cut-off magnet R|30, to the control conductor C|63 of the subscriber line |60 extending to the contact banks of the Strowger mechanisms included in the connector switches of the links having access thereto, thereby to mark the subscriber line |50 as so; i

fas

.Strowger mechanism idle. Also, the line magnet RI40 interrupts, at RA|4| and RCI 43, a point in the path for applying ground potential, at RCISS, to the control conductor C|63. Finally, the line magnet R|40 interrupts, at RA|45 and RC|45, a further point in the path for applying ground potential, at RCl35, to the start conductor CI90 and interrupts, at RAME and RC|45, a point in the path for applying ground potential, at RCI35, to the control conductor Cl extending to the permanent alarm device. Also, it is noted that when both the cut-off magnet R|30 and the line magnet R|40 restore, the latching arrangement for causing the two switch spring assemblies associated with the line magnet RMD to be actuated simultaneously is reset. At this time the subscriber line |60 is marked as idle to the nder and connector switches of the links having access thereto and the line circuit |05 is completely released.

It will be understood that a call which is to be extended from the subscriber substation C to the subscriber sub-station A is first initiated at the substation C by removing the receiver of the telephone instrument thereat from its hook and is subsequently completed to the substation A in the same manner that the previously described call from the substation A was extended to the substation C. The release of this established connection is under the control of the last party to replace the receiver of the telephone instrument at his substation upon its hook, as previously noted. l

A reverting call which is to be extended from the subscriber substation A to ythe subscriber substation B is rst initiated at the substation A by removing the receiver of the telephone instrument thereat from its hook, thereby to complete the previously traced bridge circuit for energizing the upper and lower windings of the line magnet R|20. When thus energized, the line magnet R|20 operates, as previously explained, in order to complete, at RA|2| and RCI23, the previously traced path for yapplying ground potential to the control conductor C154 of the subscriber line |50 extending to the contact banks of the Strowger mechanisms included in the connector switches of the links having access thereto, thereby to mark the subscriber line |50 as busy immediately. Further, the line magnet R|20 completes, at RAIZ!! and RCIZQ, the previously traced path for applying battery potential, at the upper winding of the cut-off magnet RI I0, to the control conductor C|53 of the subscriber line- |50 extending to the contact banks of the included in the lnder switches of the links having access thereto, thereby to mark the radial position of the contact sets in the contact banks terminating the subscriber line |50. Finally, the line magnet R|20 completes, at RAI25 and RC|25 and at RAIZG and RCI 27, the previously traced path for applying ground potential, at RCI I5, to the start conductor C190 extending into the distributor |03. This application of ground potential to the start conductor C|90 causes the distributor |03 to operate to assign a previously selected idle link in the group of links to the use of the calling subscriber line |50. Assuming that the illustrated link |il is assigned to the use of the callf ing subscriber line |50, this application of ground potential to the start conductor CIGS and this application of battery potential to the control conductor C|53 marks the position of the contact vset -in the contact bank of the Strowger links having access mechanism included in the finder switch |0| at which the subscriber line |50 is terminated. The nder switch |0| then operates, in the previously described manner, thereby to seize the calling subscriber line |50. When the callingr subscriber line |50 is seized, the cut-off magnet RI I0 operates to release the. latching arrangement for restraining the restoring switch spring assembly associated with the line magnet R|20 in its .actuated position and to complete, at RAIM and RCI HI, the previously traced holding circuit for energizing the lower winding thereof. Also, the cut-oli magnet R||0 completes, at RAIIG and RAI the previously traced holding circuit for energizing the lower winding of the line magnet Rl20, completes, at RA||2 and RCI I2, the previously traced path for applying ground potential to the control conductor CI54 of the subscriber line |50, thereby to mark the subscriber line |50 as busy to the connector switches of the thereto, interrupts, at RAIII and RC||| and at RAIIT and RCII'l, the previously traced bridge circuit for energizing the windings of the line magnet R|20, and interrupts, at RAI and RCI l5, the previously traced path for applying ground potential to the start conductor C|90. The restoring switch spring assembly associated with the line magnet R|20 then restores to its normal position, as previously noted, thereby to interrupt, at RA|24 and RCiM, a point in the holding circuit for energizing the upper winding of the cut-oli" magnet RI I0, to interrupt, at RA|26 and RCIBT, a further point in the previously traced path for applying ground potential to the start conductor C|90, and to prepare, at RAiZS and RCIZB, a point in the previously mentioned circuit for applying ground potential, at RCII5, to the control conductor C156 extending to the permanent alarm device. At this time the line and cut-oir` magnets R|20 and RI I0, respectively, are completely operated, and the restoring switch spring assembly associated with the line magnet RI 20 is restored to its normal position, as previously noted.

The connector switch |02 is conditioned to be responsive to a series of dialed digits at this time. The subscriber at the substation A then dials at the dial mechanism thereat successively two predetermined digits into the connector switch |02, thereby to cause the connector switch to operate and select the rst trunk line terminating thereat to which an idle reverting call switch is connected. When these two predetermined digits are successively dialed the connector switch |02 operates as a trunk hunting` connector switch in order to select a trunk line associated with an idle one of the reverting call switches or to return busy tone current over the loop circuit extending to the calling subscriber substation A in the event that all of the reverting call switches are busy. Assuming that the illustrated reverting call switch 200 is the first idle switch, the connector switch |02 operates to seize the trunk line |10 extending thereto. The reverting call switch 200 is marked as idle or busy, respectively, by the presence of battery or ground potential upon the control conductor CH2 of the trunk line |10. At this time, the reverting call switch 200 being idle, battery potential appears upon the control conductor CH2 of the trunk line |'|0, the path for connecting battery potential to the control conductor C|'|2 extending from battery at the resistor 200 by way of the resistor 206,*RA21I, RCZ42, RAMI, and 75 RAN@ to the control conductor C122. When the connector switch i132 selects the trunk line II extending to the idle reverting call switch 23D, further operation thereof is arrested due to the presence of battery potential upon the control conductor CH2 thereof, in the usual manner.

When the trunk line Iii! is thus seized by the connector switch Iii2, this connector switch operates to complete a loop circuit between the calling subscriber substation A and the line relay R23l in the reverting call switch 22S, this loop circuit extending from ground at the lower winding of R233 by way oi the lower winding of R232, RC229, and RAEil to CH3, and from battery at the upper winding ci R235 by way of the upper winding of R235, RCQZ, and RA22I to Ci'l, the line conductors Ci'ii and CH3 of the trunk line ill] being connected by way of the operated link iiil? to the line conductors CISI and CI52, respectively, of the calling subscriber line E58, and the telephone instrument at the substation A being included in a bridge path extending between the line conductors Citi and (N52 of the subscriber line 58. When energized over the above-traced circuit the line relay R232 operates to complete, at RA23i and RC222, an obvious circuit for energizing the hold relay R249. When thus energized the hold relay R24@ operates to interrupt, at RAEM and RC'liif, a point in the path for applying battery potential to the control conductcr CH2 of the trunk line i'it, and completes, at RAMI and RCEAiS, a path for applying ground potential to the control conductor CH2, this path extending from ground, at ROMS, by way of RAZiI, and RA255 to the control conductor C5212. This application of ground potential to the control conductor CH2 of the trunk line I'Ill marks this trunk line as busy to the connector switches oi the links having access thereto, and causes the switch-through relay in the connector switch H32 to operate. When the switch-through relay in the connector switch M2 operates, ground potential in the operated link ISS is removed from the wipers I8! and i 811 of the nder and connector switches IGI and I2, respectively, the link Ill and the line circuit iut being retained in its operated position at this time due to the application of ground potential to the control conductor CH2 of the trunk line lill. Also, upon operating, the relay R240 prepares, at RAME, a point in an impulse circuit traced hereinafter for energizing the rotary magnets M236 and M235 of the minor switches 28S and 292i, respec tively, included in the reverting call switch 255i).

The subscriber at the calling substation A then dials at the dial mechanism thereat a third digit corresponding to the last digit of the directory number of the calling substation A, thereby to transmit a series of impulses by way of the previously mentioned loop circuit to the line relay R232. The relay R23!) follows the dialed impulses in the usual manner, restoring each time the loop circuit is interrupted and operating each time the loop circuit is completed. Each time the relay R232 restores, it interrupts, at RAZSi and RC232, the circuit for energizing the hold relay R246, and completes, at RAZSi and RC233, a circuit for energizing in multiple the relay R259 and the rotary magnet M236 of the minor switch 23S. lThe last-mentioned circuit extends from ground, at RA234, by way of RC233, RAME, and RA262 to R026@ one branch of this circuit extending from RCZGi by way oi the winding of R250 to battery, andthe other branch extending from RCZBIi by way of RA2I3, RC2T6, and the winding of M2M to battery. The relays R240 and R250, being of the slow-to-release type, remain operated during impulsing. Each time the circuit for energizing the rotary magnet M236 is completed and interrupted, this magnet operates to drive the wipers 283 and 285 of the rotary switches 28| and 282, respectively, included in the minor switch 285 one step away from their normal positions. When the wipers noted of the rotary switches 223i and 282 are driven away from their normal positions, the switch springs 232 are actuated into engagement, thereby to prepare a circuit traced hereinafter for energizing the transfer relay R 210, this circuit being interrupted at this time, at RA25i, by the operated relay R252. In response to this digit the wipers 283 and 285 of the rotary switches 28 and 282, respectively, are driven a number of steps away from their normal positions corresponding to this dialed digit and into engagement with correspending contacts in the associated contact banks 284 and 286, respectively. At the conclusion of the third digit the line relay R236 reoperates, thereby to interrupt, at RA23I and RC233, the circuit for energizing in multiple the relay R252 and the rotary magnet M236 in order to cause the relay R25t to restore shortly thereafter and to arrest further operation of the rota-ry magnet M236. Upon restoring, the relay R259 completes, at RA25I, the previously mentioned circuit for energizing the transfer relay R216, this circuit extending from ground, at the switch springs 23d, by way of the switch springs 234, RAZBI, and the winding of R27@ to battery. When thus energized the relay R2'iil operates to complete, at RA2'I2, an obvious holding circuit for energizing the winding thereof, to interrupt, at RAUS and RCZ'MS, a further point in the previously traced circuit for energizing the rotary magnet M236, and to prepare, at RA2i3 andv RCN/i, a point in a circuit traced hereinafter for energizing in multiple the relay R259 and the rotary magnet M238 of the minor switch 29d.

The subscriber at the calling substation A then dials at the dial mechanism thereat a fourth digit corresponding to the last digit of the directory number of the called substation B, thereby to transmit anotherl series of impulses by way of the previously mentioned loop circuit to the line relay R239. dialed impulses in the usual manner. Each time the relay R235] restores it interrupts, at RA23I and RC232, the circuit for energizing the hold relay R226, and completes, at RA23I and RC233, the previously mentioned circuit for energizing in multiple the relay R255) and the rotary mag net M238 of the minor switch 29E). The lastmentioned circuit extends from ground, at RA23I, by way of RC233, RA245, and RA262 to RCZi, one branch of this circuit extending from RC2GII by way of the winding of R250 to battery, and the other branch extending from R025@ by Way of RAZ'IS, RCZ'IB, and the winding of M238 to battery. Each time the circuit for energizing the rotary magnet M233 is completed and interrupted, this magnet operates to drive the wipers 223 and 2S5 of the rotary switches 29E and 292, respectively, included in the minor switch 296* one step away from their normal positions. switches 29I and 292 are driven away from their normal positions the switch springs 235 are actuated into engagement, thereby to prepare a circuit traced hereinafter for energizing the transfer relay R', this circuit being interrupted at The relay R230 follows the' When the wipers noted of the rotary' this time, at RA2 52, by the operated relay R256. In response to this digit the Wipers 293 and 295 of the rotary switchesv 29| and`292,'respectively, are driven a niunber of steps away from their normal positions corresponding to this dialed digit and into engagement with corresponding contacts in the associated contact banks 294 and 296, respectively. At the conclusion of the fourth digit the line relay R235 reoperates, thereby to interrupt, atRA23i and RC233, the circuit for energizing in multiple the relay Rz'ii and the rotary magnet M238 in order to cause the relay R253 to restore `shortly thereafter and to arrest further operation of the rotary magnet M233. Upon restoring, the relay Ri'iii completes, at RA252, the. previously'rnentioned circuit for energizing the transfer relay Ril, this circuit extending from ground, at the switch springs 235, by Way of the switch springs 235, RA252, and the winding of REEG to battery. When thus energized the relay R266 operates to complete, at RA2F5I, an obvious holding circuit vfor energizing the winding thereof, to interrupt, at RAZZand RCZli, a further point in the previously traced circuit for energizing in multiple the relay R253 and the rotary magnet M238, and to prepare, at RAZSE and RC2S3, a circuit traced hereinafter for energizing the relay RZIt.

Shortly after the conclusion of the fourth digit dialed the subscriber at the substation A replaces the receiver of the telephone instrument thereat upon its hook, thereby to interrupt the loop circuit extendingto the line relay RZSQ in order to cause the latter relay tol restore. Upon restoring, the relay R2i! completes, at RA23I and RC233, the previously mentioned circuit for energizing the relay RZIil, this circuit extending from ground, at RA23I, by way of RC233, RAME, RAZER, RC263, RAEEB, and the winding of R2Iil to battery. When thus energized the relay R230 operates to complete, at RAZI I, an obvious path for applying ground potential to the ringing machine start lead C205, to prepare, at RA2i2, a holding circuit traced hereinafter for energizing the switch-through relay RER, "to complete, at RAZIS, a path extending from battery, at .the winding of R220, by way of the winding of R22t, RA22A5, RC225, and RARIB to the ring pick-up lead C2I5 for applying battery potential to C2 iii, and to complete, at RAZIIi, an obvious holding circuit for energizing the hold relay R24li. The hold rela-y R246, being of the slow-to-release type, does not restore incident to the restoration of the line relay R238, and is retained in its operated position over the above-mentioned holding circuit for energizing the winding thereof. Ac-

cordingly, ground potential is not removed from the control conductor CH2 of the trunk line Il!! incident to the restoration of the line relay R230.

Shortly thereafter and at the beginning of a code ringing cycle, ground potential is applied in the ringing machine to the ring pick-up lead C2I5, thereby .to complete a circuit for energizing the switch-through relay R220, this circuit extending from the groundedring pick-up lead CZIE by way of RA2I3, RC226, `RA225, and the Winding of R226 to battery. When thus energized the relay R226 operates to complete, at RAEZO. and RA225, a holding circuit for energizing the Winding thereof extending from ground, at RAZiZ, by way of RAEZA, RA225, and the winding of R229 to battery, and to interrupt, at RA225 and RC226, the original circuit for energizing the winding thereof by Way o-f the ring pick-up lead C2I5. Also'gthe krelay R220 interrupts, at RAZZI `and RC2`22, and at'RA22i and RC223, further points in the loop circuit for energizing the line relay R23il, and completes, at RA22Il and RC223, and at RA22`I and RC228, points in a circuit traced hereinafter for projecting ringing current from the ringing machine associated with the trunk line 2% by Way of the operated reverting call switch 200, the trunk line Iii), and the linkr ISI! over the sub# scriber line 1563,'the exact circuit for projecting inging current from the ringing machine associated with the trunk line Z over the subscriber line ISE] depending upon the positions of the Wipers of the rotary switches included in the minor switches 'Zim kand '390, in a manner more fully described subsequently.

As previously noted, a divided ringing circuit is employed in the system, a rst group or" subscriber substations associated with each party line `having ringers thereat connected between one line conductor of the party line and ground, and a second group of subscriber substations associated With each party line having ringers thereat connectedbetween the other line conductor of the party line and ground. The oper# ation of the reverting call switch Zii depends upon whether the calling and called subscriber substations A and B are in the saine group. In the event these subscriber substations are in the same group, the reverting call switch 203 operates to cause ringing current of the code corresponding to the called subscriber substation to be projected over the line conductor 'of the sube scriber line Iil, to which the ringers at each of the subscriber substations A and B are connected. in the event these subscriber substations are in different groups, the reverting call switch Edil operates first to cause ringing current ofl the code corresponding to the called subscriber substation to be projected over the line conductor of the subscriber line idto which the ringer at the called substation B is connected, and then to cause ringing current of the code corresponding to the calling subscriber substation to be projected over the line conductor of the subscriber rline Iil, to which the ringer at the calling sub-- station A is connected. Also, itis noted that the subscriber substations associated withV the subn scriber line 50 and having ringers connected to one line conductor thereof are assigneddirectory numbers comprising a third odd digit, and the subscriber substations associated with the subscriber line Ibi) and having ringers connected to the other line conductor thereof are assigned rectory numbers comprising a third even digit.

Assuming that the third digit of the directory number of the calling subscriber substation A'is l, the No. l, and the third digit of the directory number of the called subscriber substationvB is the No. 3, the wipers of the rotary switches oi the minor switch 280 engage the rst contacts in the associated contact banks, and the wipers of the rotary switches of the minor switch 29!) engage the third contacts in the associated contact banks. At this time a circuit. is completed for projecting ringing current of the code corresponding to the called subscriber substation B over the subscriber line Idil, this circuit extending from the ungrounded terminal of the ringing machine winding by Way of the ringing conductor M3, the third contact in the contact bank 2M and the associated wiper 233 of the rotary switch 2ilI, the upper winding of the ring cut-off relay R255,

YRCZLZt, and RAZZI, to the line conductor Ci'I of the trunk line i119, and rtherefrom -by-way of the operated link |00, the line conductor C|5| of the subscriber line |50, and a condenser and the ringer at the called substation B, to ground. Also, a circuit is prepared for energizing the upper winding of the ring cut-oir relay R255, which is completed when the subscriber at the substation B answers the call by removing the receiver of the telephone instrument thereat from its hook, this circuit extending, when completed, by way of the previously traced path to the line conductor C5| of the subscriber line |55, and therefrom by way of the bridge path at the substation B between the line conductors C15! and C|52 of the subscriber line |50, C|52, the operated link |00, the line conductor CH3 of the trunk line |10, RA22?, RC228, and the windings 202 and 203 of the transformer 20| to ground.

Assuming that the third digit or the directory number ofthe calling subscriber substation A is the No. 2, and the third digit of the directory number of the called subscriber substation B is the No. 4, the wipers of the rotary switches of the minor switch 280 engage the second contacts in the associated contact banks, and the wipers of the rotary switches of the minor switch 200 engage the fourth contacts inthe associated contact banks. At this time a circuit is completed for projecting ringing current of the Code corresponding to the called subscriber substation B over the subscriber line |50, this circuit extending from the ungrounded terminal of the ringing machine winding by way of the ringing conductor M4, the fourth contact in the contact bank 295 and the associated wiper 295 oi the rotary switch 292, and the windings 205 and 200 of the transformer 20i to ground at RA220. This ringing current traversing the windings 204 and 205 of the transformer 20| induces a correspondingy ringing current in the windings 202 and 203 thereof, which traverses a path extending from ground by way of the windings 203 and 202, RC22B, RA221, to the line conductor CH3 of the trunk line |10, and therefrom by way of the operated link |00, the line conductor C|52 of the subscriber line |50, and the condenser and the ringer at the called substation B to ground. Also, a circuit is prepared for energizing the upper winding of the cut-oil relay R255, which is completed when the subscriber at the substation B answers the call by removing the receiver of the telephone instrument thereat from its hook, this circuit extending, when` completed, from battery at the resistor 20?, by way of the resistor 201, the second contact in the contact bank 280 and the associated wiper 203 of the rotary switch 28|, the fourth contact in the contact bank 204 and the associated wiper 293 of the rotary switch 20|, the upper winding of R255, HC22-3, RAZZI, the line conductor Ci 'H of the trunk line |10, and the operated link |00 to the line conductor C|5|, and therefrom by way of the bridge path at the substation B between the line conductors C|5| and C|52 of the subscriber line |50, and a portion of the previously traced circuit to ground, at the winding 203 of the transformer 20|.

Assuming that the third digit of the directory number of the calling subscriber substation A is the No. l, and the third digit of the directory number of the called subscriber substation B is the No. 2, the wipers of the rotary switches of the minor switch 200 engage the first contacts in the associated contact banks, and the wipers of the rotary switches of the minor switch 200 engage the second contacts in the associated contact banks. At this time a circuit is completed for projecting ringing current of the code corresponding to the called subscriber substation B over the subscriber line |50, this circuit extending from the ungrounded terminal of the ringing machine winding by way of the ringing con- 'I ductor M2, the second contact in the contact bank 296 and the associated wiper '295 of the rotary switch 292, and the windings 205 and 204 of the transformer 20| to ground at RA220. This ringing current traversing the windings 204 and 205 of the transformer 20| induces a corresponding ringing current in the windings 202 and 203 thereof which is projected by way of the previously traced path over the line conductor C|52 of the subscriber line |50 to ground at the ringer at the called substation B. Also a circuit is completed for projecting ringing current of the code corresponding to the calling subscriber substation A over the subscriber line |50, this circuit extending from the ungrounded terminal of the ringing machine winding by way of the ringing conductor Ml, the first contact in the contact bank 285 and the associated `wiper 2830i the rotary switch 28|, the second contact in the contact bank 204 and the associated wiper 293 of the rotary switch 29|, the upper winding of the ring cut-01T relay R255, RC223, RAZZI, the line conductor Cl'H of the trunk line |10, the operated link |00, the line conductor C|5| of the subscriber line |50, and a condenser and the ringer at the calling substation A to ground. The ringing machine operates to complete the circuits for applying ringing currents to the ringing conductors MI to M5, inclusive, sequentially, thereby to cause the ringer at the called substation B and the ringer at the calling substation A to be operated alternatively. Also a circuit is prepared for energizing the upper winding of the ring cut-off relay R255, which is completed when the subscriber at the substation B answers the call by removing the receiver of the telephone instrument thereat from its hook, this circuit extending, when completed, from the ringing conductor Ml by way of the previously traced path to ground at the winding 203 of the transformer,

Assuming that the third digit of th`e directory number of the calling subscriber substation A is the No. 2, and the third digit of the directory number of the Acalled subscriber substation B is f,

the No. l, the wipers of the rotary switches of the minor. switch 280 engage the second contacts in the associated contact banks, and the wipers of the rotary switches of the minor switch 290 engage the first contacts in the associated con-;

tact banks. At this time a circuit is completed for projecting ringing current of the code corresponding to the called subscriber substation B over the subscriber line I 50, this circuit extending from the ungrounded terminal of the ringing machine winding by way of the ringing conductor MI, the iirst contact in the contact bank 294 and the associated wiper 293 of the rotary switch 20|, the upper winding of R255 and a portion of the previously traced circuit including the line conductor C|5| of the subscriber line |50 to ground at the ringer at the called substation B. Also a circuit is completed for projecting ringing current of the code corresponding to the calling substation A over the subscriber line |50, this circuit extending from the ungrounded terminal 0f the ringing machine winding by way of the ringing conductor M2, the second contact in the contact bank 286 and the associated wiper 285 of the rotary switch 282, the

rst contact in the contact bank 296'and the associated wiper 295 of the rotary switch 292, and the windings 205 and 200 of the transformer 20`I` to ground, at RA220. This ringing current traversing the windings 204 and 205 of the transformer 20! induces a corresponding ringing current in the windings 202 and 203 thereof which is projected by way of the previously traced circuit including the line conductor C|52 of the subscriber line |50 to ground at the ringer at the calling substation A. As previously noted, the ringers at the called and calling subscriber substations B and A, respectively, are Operated alternatively. Also a circuit is prepared for energizing the upper winding of the ring cut-off relay R255, which is completed when the subscriber at the substation B answers the call by removing the receiver of the telephone instrument thereat from its hook, this circuit extending, when completed, from the ringing conductor MI by way of the previously traced path to ground at the winding 203 of the transformer 20|.

When the subscriber at the called substation B answers the call, one of the previously traced circuits for energizing the up-per winding of the ring cut-01T relay R255 is completed, depending upon whether the calling and called substations A and B, respectively, are in the same or different groups, as previously noted. When thus energized the ring cut-off relay R255 operates to complete, at RA251, a holding circuit for energizing the lower winding thereof, this circuit extending from ground, at RAZM, by way of RA251 and the lower winding of R255 to battery. Also the relay R255 interrupts, at RA256, the previously traced path for applying ground potential to the control conductor CH2 of the trunk line |10, and interrupts, at RA258, the circuit for energizing the relay R2 I0, thereby to cause the latter relay to restore. Upon restoring, the relay R2 |9 interrupts, at RA2| l, the previously traced path for applying ground potential to the ringing machine start lead C206 in order to arrest further operation of the ringing machine associated with the reverting call switch 200, to interrupt, at RA2|2, the holding circuit for energizing the relay R220 in order to cause the latter relay to restore, and to interrupt, at RA2I4, the previously traced holding circuit for energizing the hold relay R200. Shortly thereafter the hold relay R220 restores to interrupt, at RA244, the holding circuit for energizing the lower winding of the ring cutoff relay R255 in order to cause the latter relay to restore shortly thereafter, and to complete, at vRANG, a circuit for energizing the release magnet M239 of the minor switch 250, this circuit extending from ground. at RA245, by way of RA2S5, RCZSE, and the winding of M239 to battery. When this energized the release magnet M239 operates to -release the wipers of the rotary switches 29| and 292 of the minor switch 290, thereby to cause these wipers to be returned to their normal positions. When the wipers noted of the rotary switches of the minor switch 280 are returned to their normal positions, the switch springs 235 are actuated into disengagement, thereby to interrupt the holding circuit for energizing the transfer relay R250. The transfer relay R260 then restores to interrupt, at RA265 and H6266, the circuit for energizing the release magnet M239, and to complete, at RA255 and R026?, a circuit for energizing the release magnet M231 of the minor switch 230, this circuit extending from ground, at RA246, by way of RA265, RCZB'I,

RAZ'H, and the `winding of R231v to battery. When thus energized the release magnet M231 operates to release the wipers of the rotary switches 20| and 282 of the minor switch 280, thereby to cause these wipers to be returned to their normal positions. When the Wipers noted of the rotary switches of the minor switch 280 are returned to their normal positions, the switch springs 230 are actuated into disengagement, thereby to interrupt the holding circuit for energizing the transfer relay R270. The transfer relay R270 then restores to interrupt, at RAZll, the circuit for energizing the release magnet M231. Upon restoring, the hold relay R200, the

ring cut-off relay R255, and the transfer relay..

at the called substation B to interrupt, at RA256,

the path for applying ground potential to the control conductor CI'I2 of the trunk line I'lil, thereby to interrupt the previously traced holding circuit for energizing the lower winding-of the cut-off magnet RI|0 in the line circuit |20 individually associated with the subscriber line |50. The cut-olf magnet RI Ill then restores, to complete, at RAIH and RCN? and at RAMI and RCI a bridge circuit for energizing the windings o f the linemagnet R520, thereby to retain this line magnet in its operated position. This circuit extends from ground at the lower winding of RI 20 by way of the lower winding of RI20, RAIll', RCII'I, CI52, the bridge path including the telephone instrument at the called subscriber substation B between the line conductors C|52 and CI5| of the subscriber line |50, C|5I, RCIH, RA||| and the upper winding of R|20 to battery.l Also,lupon restoring, the cuto magnet Rl I0 interrupts, at RAI IIi and RAI Il', the previously traced holding circuit for energizing the lower winding of the line magnet R|20, interrupts, at RAI I4 and RCI I0, a further point in the holding circuit for energizing the lower winding thereof, interrupts, at RAI I2 and RCI 2, a further point in the previously traced path for applying ground potential by way of the control conductor CI53 of the subscriber line |50 to the control conductor CI54 thereof, and completes, v

at RAI i3 and RCI I3, the previously traced path for applying ground potential, at RC! I3, to the control conductor CI54 of the subscriber line |50 extending to the contact banks of the Strowger mechanisms included in the connector switches of the` links having access thereto, thereby to mark the subscriber line |59 as busy. Finally, the cut-off magnet R|I0 completes, at RA|5 and ROMS, the previously mentioned path for applying ground potential to the control `conductor C|5 extending to the permanent alarm, this path extending from ground at RC|I5 by way of RAl I5, RCI25, RA|25, RA|25 and RCIZS to the control conductor OISE. This application of ground potential to the control conductor C |56 causes the permanent alarm device associated therewith to be actuated, thereby to indicate to an operator that the subscriber line |50 is busy on a reverting call or due to a permanent `fault thereof thereon. Due to the fact that the bridge circuit for energizing the upper and lower windings of the line magnet RIZil is completed at RCIII and RAIII and at RAII'I and RCEIT prior to the interruption of the holding circuit for energizing the lower winding thereof at RAI I6 and RAI Il, as previously noted, the line magnet RIZ!) remains in its operated position. At this time the line circuit m4 is operated to lock the subscriber line I5!! out of service; and talking battery is supplied by way of the previously traced bridge circuit to the telephone instrument at the called subscriber substation B.

As previously noted, when the subscriber at the called substation B answers the call the reverting call switch 200 is-released, thereby to interrupt the circuit for projecting ringing current over the subscriber line I5!) in order to cause further operation of the ringer at the calling subscriber substation A to be arrested. When the operation of the ringer at the calling subscriber substation A is arrested, the subscriber thereat is advised that the subscriber at the called substation B has answered the call. The subscriber at the substation A then removes the receiver of the telephone instrument thereat from its hook, thereby to complete an established connection between the calling and called subscriber substations A and B, respectively, for two-way communication therebetween, talking battery being supplied to the substation A by way of the previously traced bridge circuit.

The release of this established connection between the subscriber substations A and B is under the control of the last subscriber to replace the receiver of the telephone instrument at his substation upon its hook. When the last subscriber replaces the receiver of the telephone instrument at his substation upon its hook, the bridge circuit for energizing the upper and lower windings of the line magnet RIZIB is interrupted, thereby to cause this line magnet to restore, as previously noted. At this time the established connection between the subscriber substations A and B is completely released, and the line circuit |04 individually associated with the subscriber line I5@ is released, thereby to mark this subscriber line asv idle to the finder and connector switches of the links having access thereto.

It will be understood that a reverting call which is to be extended from the subscriber substation C to the subscriber substation lD is first initiated at the substation C by removing the receiver of the telephone instrument thereat from its hook and is subsequently completed to the substation D in the manner that the previously described reverting call from the substation A was extended to the substation B. The release of this established connection is under the control of the last party to replace the receiver of the telephone instrument at his substation upon its hook, as previously noted.

Also it is noted that a timing arrangement is incorporated in the connector switch H32 which is operative in the event the switch-through relay therein does not operate within a predetermined time interval, due to the fact that the connector switch has not been fully operated to seize a line accessible thereto, to cause ground potential to be removed from the wiper ISI. For example, the link im) may be seized in the previously described manner by the appearance of a fault on one of the subscriber lines, in which case the connector switch H32 thereof would not be operated subsequently to seize a line accessible thereto in order to cause the operation of the switch-through relay therein, whereby ground potential would be removed from the wiper IBI, as previously noted. Under these conditions where ground potential is removed from the wiper IBI, the holding circuit for energizing the cut-off magnet in the line circuit associated with the line having the fault thereon is interrupted, thereby to cause the cut-off magnet to restore. Upon restoring, the cut-off magnet in the line circuit associated with the line having the fault thereon Causes the line to be locked out of service in the manner described previously in connection with the extension of a reverting call between the subscriber substations A and B. Also, ground potential is' applied to the control conductor associated therewith extending to the permanent alarm device, thereby to cause the permanent alarm device to be operated. The operation of the permanent alarm device for an unreasonable time interval indicates to an operator that the associated-4 line is locked out of service upon a permanent fault thereon rather than merely being busy due to a reverting call thereon.

While there has been described what is at present considered to be the preferred embodiment o the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A line circuit adapted for use in a telephone system including a line accessible to an automatic switch, said line circuit comprising, in combination, line and cut-oil relays, a first contact set operatively associated with said line relay, a second Contact set operatively associated with said cut-off relay, a third Contact set, means normally eirective operatively to associate said third contact set with said line relay, each of said contact sets having a normal position and being operative away trom its normal position in response to the operation of the one of said relays with which it is operatively associated, means responsive to the creation o a calling condition on said line for 'I causing said line relay to be operated, means responsive to the seizure of said line by said automatic switch for causing said cut-oif relay to be operated, means controlled by the operation of said cut-oit relay for rendering said rstmen tioned means ineective, additional means controlled by the operation of said second contact set away from its normal position for causing said line relay to be operated, and circuits for controlling said automatic switch governed in aocordance with the positions of said contact sets.

2. A line circuit adapted for use in a telephone system including a line accessible to an automatic switch, said line circuit comprising, in combination, line and cut-oi relays, a first contact set operatively associated with said line relay, a second contact set operatively associated with said cut-01T relay, a third contact set, mechanical means for operatively associating said third contact set with said line relay, each of said contact sets having a normal position and being operative away from its normal position in response to the operation of the one of said relays with which it is operatively associated,

said line relay being operative in response to the creation of a calling condition on said line, said cut-oif` relay being operative in response to the seizure oi said line by said automatic switch, means controlled by the operation of said cutoi relay for actuating said mechanical means,

fai

tig.)

tir

till) additional means controlled by the operation of said second contact set away from its normal position for causing said line relay to be operated, and circuits for controlling said automatic switch governed in accordance with the positions of said contact sets. y

3. A line circuit adapted for use in a telephone system including a line provided with at least one-line conductor `and accessible to an automatic switch, said line circuit comprising, in combination, line and cut-oilc relays, a rst contact set operatively associated with said line relay, a second contact set operatively associated with said cut-off relay, a vthird contact set, means normally elective operatively to associate said third contact set with said line relay, each of said contact vsets having a normal position and being operative away from its normal position in response to the operation of the one of said relays with which it is operatively associated, a first circuit including said line conductor for said line relay, a holding circuit for said line relay, said rst lcircuit being completed in response to the creation of a calling condition on said line, whereby said line relay is operated, said cut-off relay being operative in response to the seizure of said line by said automatic switch, means controlled by the operation of said cut-off relay for rendering said first-mentioned means ineiective, whereby said third contact set is returned to its normal position, means controlled by the operation of said second contact set away from its normal position for completing said holding circuit and for interrupting said rst circuit, whereby said line relay is retained operated, and circuits for controlling said automatic switch governed in accordance with the positions of said contact sets.

4. A line circuit adapted foruse in a telephone system including a line provided with at least one line conductor andA accessible to an automatic switch, said line circuit comprising, in combination, line and cut-olie relays, a rst contact set operatively associated with said'line relay, a

second contact set operatively associated with said cut-oli relay, a third contact set, mechanical means for operatively associating said third contact set with said line relay, each of said contact sets having a normal position and being operative away from its normal position in re sponse to theoperation of the one of said relays with which it is operatively associated, a rst circuit including said line conductor for said line relay, a holding circuit for said line relay, said irst circuit being completed in response to the creation of a calling condition on said line, whereby said line relay is operated, said cut-off relay being operative in response to the seizure of said line by said automatic switch, means controlled by the operation f said cut-off relay for actuating said mechanical means, whereby said third contact set is returned to its normal position, means controlled by the operation of said second contact set away from its normal position for completing said holding circuit and for inter'- rupting said rst circuit, whereby said line relay is retained operated, and circuits for controlling said automatic switch governed in accordance with the positions of said contact sets.

5. In a telephone system, a line, a number of automatic switches having access to said line, a line circuit associated with said line and including line and cut-oli relays, a first contact set operatively associated with said line relay, a second contact set operatively associated with said cut-off relay, a third *contact set', means normally effective operatively to associate said third contact set with said line relay, each of said contact sets having a normal position and being operative away fromiits normal position in response to the operation of the one of said relays with which it is operatively associated, means responsive to the creation of a calling condition on said line for causing said line relay to be operated, control means operative in response to the operation of said rst and third contact sets away from -their `normal positions for causing an idle one of said automatic switches to seize said line, means responsive to the seizure of said line by said one automatic switch for causing said cut-oli relay to be` operated, means controlled by the operation of said cut-on relay for rendering said first-mentioned means ineffective, whereby said third contact set is returned to its normal position, means controlled by the return of said third contact set to its normal position for arresting the operation of said control means, and additional circuits for controlling said automatic switches governed in accordance with the positions of said Contact sets.

6.'In a telephone system, a line, a number .of inder switches having access to said line, a line circuit associated with said line and including line and cut-01T relays, a distributor associated with said nder switches and operative to cause an idle one of said finder switches to operate and seize a line marked as a calling line, a rst contact set operatively associated with said line relay, a second contact set operatively associated with said cut-offrelay, a third contact set, means normally effective operatively to associate said third contact' set with said line relay, each of said contact sets having a normal position and being operative away from its normal position in response to the operation of the one'of said relays with which it is operatively associated, means responsive to the creation of a calling condition on said line for causing said line relayto be operated, means controlled by the .operation of said iirst and third contact sets away from their normal positions for initiating operation of said distributor and for marking said line as a calling line, means responsive to the seizure of said line by one of said finder switches for causing saidcut-off relay to be operated, means controlled bythe operation of said cut-oi relay for rendering said first-mentioned means inelective, whereby said third contact set is returned to its normal position, and means controlled by the return of said `third contact set to its normal 'position for arresting the operation of said distributor. y

'7. In a telephone system, a line, a number. of nder switches having access to said line, aline circuit associated with said line and including line and cut-oi relays, a distributor associated with said iinder switches and operative to cause an idle one of said nder switches to operate and seize a line marked as a calling line, a iirst contact set operatively associated with said `line relay, a second contact set operatively associated with said cut-off relay, a third Contact set, mechanical means forv operatively associating said third contact set with said line relay,'e`ach of said contact sets having a normal position and being operative away from its normal position in response to the operation of the one of said relays with which it is operatively associated, means responsive to the creation of a calling condition on said line for causing said line relay `to be operated, means controlled by the operation of said rst and third contact sets away from their normal positions for initiating operation of said distributor and for marking said line as a calling line, means responsive to the seizure of said line by one of said finder switches for causing said cut-ofi relay to be operated, means controlled by the operation of said cut-off relay for actuating saidv mechanical means, whereby said third contact set is returned to its normal position, and means controlled by the return of said third contact set to its normal position for arresting the operation of said distributor.

8. In a telephone system, a line provided with at least one line conductor, a number of nder switches having access to said line, a line circuit associated with said line and including line and cut-oil" relays, a distributor associated with said finder switches and operative to cause an idle one of said finder switches to operate and seize a line marked as a calling line, a first contact set operatively associated with said line relay, a second contact set operatively associated with said cutoii relay, a third contact set, mechanical means lor operatively associating said third contact set with said line relay, each of said Contact sets having a normal position and being operative away from its normal position in response to the operation of the one of said relays with which it is operatively associated, a rst circuit including said line conductor for said line relay, a holding circuit for said line relay, means responsive to the creation of a calling condition on said line for causing said first circuit to be completed, whereby said line relay is operated, means controlled by the operation of said irst and third Contact sets away from their normal positions for initiating operation of said distributor and for marking said line as a calling line, means responsive to the seizure of said line by one of said nder switches for causing said cut-off relay to be operated, means controlled by the operation of said cut-oi relay for actuating said mechanical means, whereby said third contact set is returned to its normal position, means controlled by the operation of said second contact set away from its normal position for completing said holding circuit and for interrupting said first circuit, whereby said line relay is retained operated, and means controlled by the return of said third Contact set to its normal position for arresting the operation of said distributor.

9. A line circuit adapted for use in a telephone system including a line accessible to a number of automatic switches, said line circuit comprising, in combination, line and cut-01T relays, a first contact set operatively associated with said line relay, a second contact set operatively associated with said cut-off relay, a third contact set, means normally effective operatively to associate said third contact set with said line relay, each of said contact sets having a normal position and being operative away from its normal position in responseto the operation of the one of said relays with which it is operatively associated, means responsive to the creation of a calling condition 'on said line for causing said line relay to be operated, means responsive to the seizure of said line by one of said automatic switches for causing said cut-ofi relay to be operated, means controlled by the operation of said cut-oi relay for rendering said first-mentioned means ineiective, whereby said third contact set is returned to its normal position, means controlled by the operation of said second contact set away from its normal position for causing said line relay to be retained-operated, means for releasing said one automatic switch, means responsive to the release 01 said one automatic switch for causing said cut-off relay to be restored, means controlled by the return of said second contact set to its normal position for causing said line relay to remain operated in the event a calling condition remains on said line, and means controlled when said first contact set is operated away from its normal position and said second and third contact sets are returned to their normal positions for marking said line as busy to said automatic switches.

l0. A line circuit adapted for use in a telephone system including a line accessible to a number of automatic switches, said line circuit comprising, in combination, line and cut-oit relays, a rst contact set operatively associated with said line relay, a second contact set operatively associated with said cut-off relay, a third contact set, mechanical means for operatively associating said third 'contact set with said line relay, each of said contact sets having a normal position and being operative away from its normal position in response to the operation of the one of said relays with which it is operatively associated, said line relay being operative in response to the creation of a calling condition on said line, said cut-off relay being operative in response to the seizure of said line by one of said automatic switches, means controlled by the loperation of said cut-off relay for actuating said mechanical means, whereby said third contact set is returned to its normal position, means controlled'by the operation of said second contact set away from its normal position for causing said line relay to be retained operated, means for releasing said one automatic switch, said cut-off relay being restored in response to the release of said one automatic switch, said line relay remaining operated subsequent to the return of said second contact set to its normal position in the event a calling condition remains on said line, and means controlled when said first contact set is operated away from its normal position and said second and third contact sets are returned to their normal positions for marking said line as busy to said automatic switches.

il. A line circuit adapted for use in a telephone system including a line provided with at least one line conductor and accessible to a number of automatic switches, said line circuit comprising, in combination, line and cut-off relays, a first contact set operatively associated with said line relay, a second contact set operatively associated with said cut-oit relay, a third contact set, means normally effective operatively to associate said third contact set with said line relay,`

each of said contact sets having a normal position and being operative away from its normal position in response to the operation of the one of said relays with which it is operatively associated, a iirst circuit including said line conductor for said line relay, a holding circuit for said line relay, said first circuit being completed in response to the creation of a calling condition on said line, whereby said line relay is operated, said cutoff relaybeing operative in response to the seizure of said line by one of said automatic switches, means controlled by the operation of said cutoff relay for rendering said first-mentioned means ineffective, whereby said third Contact set is returned to its normal position, means controlled by the operation of said second contact set away from its normal position for completing said holding circuit andY for' interrupting said rst' circuit, whereby said line 'relay lis Lretained operated, means f for f releasing `said# one automatic switch, said cut-oi relay being lrestored i in response zto theA release of said one automatic switch,-fmeans controlled -by the returnfof saidfsecond-4 contact set to its `normal Aposition for completing` said ilrst circuit and 'for interrupting said'holdng circuit, whereby'said line relay remains loperated to said'secondv positiony in-'theevent af calling-condition -remains onV said line, and means-controlled when said rst contactset-is operated 'awayfrom its-normal position and-said secondandethird contact sets are returnedto'ftheirhnormal 'positions for marking -saidlineas busy to f said lautomatic switches.

' 12. In a telephone systemfaline-a number of automatic -switches rhaving access lto-'said"\line, a i line circuit -associated with` said *line andl including line land cut-'01T relays, a 'first contact set operatively associated with-said@line relay, a-"second contact set 'operativelyfassocia-ted-fwith said cut-oif relay,` al third contact 'set, meansfnormally effective voperatively to associatersaidfthird contactset with said'line relayeach ofesaid-` contact setshaving a normal position and-'beingI operative away from its normal `position in -response to theV operation-ofthe one vof said-V relays with which it is operatively associated;- means/responsive to the creation of-'a call-ing-condition-"on said line for causing saidline relayto be operated; means controlled bythe operationof said "rst and third contact sets -awayfromtheir normal-positions for causing an -idleione of said automatic switches to seize said-line,=meansre sponsive to-the seizure of said line bysaid-one automatic switch for causing saidvcuteoff relay 'to be operated, means controllediby-the oper- -ation of said cut-off krelay ifor rendering sa-id rst-mentionedmeans ineiective, whereby said thirdcontactI set is-returned to its'fnormal'position, means controlled-'by theA operation of-said second contact set -away ffrom -its normaliposition'for causingsaid line relay to =be retained operated, means for releasing -.-said one'Lautomatic switch,-means responsive to `the release of `said-one automatic switch for causing saidcutvoff` relay to be restored', meansY controlled by the return of-saidv-second contact set to its normal position'for causing said `line relay to remain -operated inthe eventra calling"condition-'remains onsaid line, -andI-means controlled "when said iirst contact set is operated awayffromf its 'normallrposition and saidesecond and v-thirdfcontact sets` are returned to their fnormalpo'sitionsrfor marking said line as Abusy to said -automati switches.

13. In a' telephone system, a line,v a numberof nder and connectorrswitches'havingaccess to said line, a-line circuitassociated with= said *line and including line4 and cut-ofi relays,` a distributor associated with fsaidnder switchesfand operative to cause an idle one of said fnderswltches to operate and seize Va line-marked as `a calling line, a rst contact setY operatively associated with said line relay, a secondv contact set operatively associated withfsaid cut-off relay, -a -third contact set, means normally effective -op'erativelyto associate said' third contactset-with said l-linerelay, each of said contact sets having-afnormal-position and being operative away from rits normal position in response to the operation of'they one of `said'relays with which@ itis operatively Aasf sociated,2means responsiveto the :creationlof a calling conditiony onsaid line? forI causingdsaid line relaylto be.V operated; means Vcontrolled by the operation i of :saldi firstv and third contact `setsV away .from'their 'normal upositionsifor initiatingoperation of said distributor andfforrmarking-isaid'- line asa'calling .line,'means responsive'to the'seizure 31 .of fsaid line: by one of said nder switches for causingzsaidcut-oii relay to be operated,v means ,controlledfby the operation of said cut-off relay -for rendering .said iirst-mentioned 1 means ineiective, vwhereby saidfthirdcontact r'set is returned ato its normal position, means controlled ,bylthe .operation of .said second Contact yset away fromiitsr'normal position forr causing said line relayztotbe retainedvoperated, means controlled :byltheireturn'fofsaid` third contact set'to its normalzposltionior arresting the operation of said vdistributor,"means for releasing said. one f-finder .switch,means responsiveto the release of said 'one'nderswitch ior'causing said cut-oir relay -torberrestoredmeans controlled by the'return` of said y.second :contact settoits normal position for causing .saidiline relaytoremainoperated -ingthefevent a kcalling condition remains on said .line,. andvmeans .controlled when said first contact set isuoperatedraway from its normal position and saidrsecond` contact set is: returnedY to its. normal lposition for marking saidlineas busyto-sad connector switches.

:14.:In yatelephone system, a line, a number -of :iinfderf a-nd connector `switches having .access to Vlsaid line, a :line circuit; .associated with said line :and-1 including line and cut-.01T 1 relays, a distributorrassociated withfsaid finder .switches .and operative .to /causeran idle one :offsaid finder switches to operate; and seize alinefmarkedas .Aafrcalling'rlinefa Y rst contact set operativelyassociated with *saidzline-relay,` axsecond contact set i :operatively .associated with said i cut-off 1 relay; a .third contact set; :means normally effective operatively t0 associate said third contact setA with vsaidr-linemelay,l each of said 'contacta sets having .anormal position-and'beingsoperative away from its normal position inresponse toithe operation .off the oneofsaid"relays.wwith which itisoperatively associated, meansresponsive-to the creation `of a calling, condition on said line for causing said line:relay'to be operated; means controlledE .by the- .operation of t said riirstI 'aandnthird .contact 'setsaway from theirzfnormal lpositions for .initiating operation of said distributor :and for 'marking said line asa calling line,ameans: responsive to thefseizure of` said vlinefrby yone vof said nder` switches r for causing said icut-oii'relayly to bezoperatemmeans controlled bytheoperationof said `cut-off e relay for vrendering. said Arstz-mentioned means ineffectivepwhereby said third con- *tact-set isreturned to its normal position,.;means controlledby the operation of.y said .secondi` contact set. :away from' its normalnposition' for causing said. line relay to `beretaine'd operated; means controlled' by the 'return of4 said! third Contact 'fset to its normal position' for. arrestingthe operation of i-said distributor, lmeans `for'releasing lsaid' one nd'er switch-means responsive -to' I-thefrelease of said oneA finder lswitch for causing-.said` cut-'off relay vto be restored, means controlledI bytheI return offsaid second contacts'et vto its'normal position-y for' causingl said line relay; to remain operated in the event a calling .condition remains on said line; :means controlled when-said first contact set isoperated laway from-itsnormal position and 'said' second contact'setds returnedto its normal position 'ior1marki-ng1said line as`r busy to said' connector switches,- eandlv signalingE means controlled tv-lierresaid-v rstfcontact seti -is operated

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