Historical Document · 1951
US 2,562,362 Testing System Employing Test Distributor and Test Connector Switches
AE test distributor/connector system.
Historical Document · 1951
AE test distributor/connector system.
July 31, 1951 . c. E. LoMAx 2,562,362 TESTING SYSTEM EMPLOYINC TEST DISTRIBUTOR SWITCHES ANO TEST CONNECTOR SWITCHES juìy 31, 195] C, E, LQMAX 2,562,362 TESTING SYSTEM EMFLOYING TEST DISTRIBUTOR SWITCHES AND TEST CONNECTOR SWITCHES Filed NOV. 4, 1947 4 Sheets--Shee’rI 2 5m„,ö»3S,mÉEm . m.SmezääëtSÍMÚU4@ n3N| ,«w NGE . , vl EN u v n fau EN Q. r El INVENTGR. CLARENCE E. UMAX BY' »VvmwSßaäw.m c. E. LoMAx 2,562,362 July 31, T951TESTING SYSTEM EMPLOYING TEsT DISTRIBUTOR swITcHEs » AND TEST CONNECTOR SWITCHES 4 Sheets-Sheet 5 'Filed Nov. 4, 1947 C', ‘Ii-____ä ,_ 1 pI if) N E BY July 31, 1951 c. E. LoMAx SWITCHES ` 2,562,362 ' ' TESTING SYSTEM EMPLOYING TEST DISTRIBUTOR AND TEST CONNECTOR SWITCHES Filed Nov. 4, 1947 4 Sheetsèsneet 4 I 2,562,362y l‘Patented July 31, v1951 UNITED STATES gmxrrur oFFlCi-:ffl TRIBUTOR SWITCHES AN e TEST CON NECTOR SWITCHES Clarence E. Lomax, Chicago, Ill., assigner to Auà tomatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware ` Application November 4, 1947, Serial No. '783,962 l 2 The present invention relates in general to ing both testers and verification operators, which automatic telephone systems, Aand more particu larly to circuit facilities employed in 'such'sys tems for testing subscribers’ line circuits from a test switchboard and for verifying Vthe line is seized directly by the testers and through a selector switch by the operators, and which is 5 . automatically positioned >for testing service when seized directly and for verification service when'. numbers of subscribers’ line circuitsV from an seized through a selector switch. operator-controlled switchboard which is usuallyA a switchboard for completing toll connectio’nsto, 'A further object of the invention `is to provide in a testing system of the rcharacter described, and from, the line circuits. _ y , an improved test distributor switch which in-. e ' -The improved circuit facilities provided by the present invention include a test switchboard lo cated in a main office and equipped with position test circuits having the instruments and other apparatus Anecessary to perform tests on sub , 170 i corporates new and novel means for ~busying a' selected test connector switch. A y A still further object of the invention is .to scribers’ line circuits, a test distributor switch accessible to the test switchboard over one trunk path and operable thereover, test connector provide in a testing system of the character ¿de scribed, novel means for artificially busyìng .atest distributor switch while 'it is in service,` .said artificial busying causing no interference with the regular operation and release of the .testing switch, or switches, accessible to the test dis. system. . tributor switch and operable from the test Another object of the invention is to provide in, switchboard through the test distributor switch 20 a testing system of the character described, im for selecting line circuits inthe main olìice’for proved and novel means for releasing an oper-_ testing, and an operatore-controlled switchboard ated test connector switch. . located in the >same main office and having access Another object of the invention is to >provide to the same test distributor switch over another an improved multi-office testing system wherein trunk path for controlling the test distributor 25 the same test distributor switch in a branch office switch and associated test connector switch, or is available to the main ofiice testers and veriñcaf switches, to select certain main fofûce line cir tion operators as well `as to the branch office cuits thereby to verify line 'numbers `passed to tester, wherein means is provided for busying the the operators by main office subscribers when re path from the branch office test switchboard to questing that certain connections (toll) be ai) the branch office test distributor switch when the established for them. branch oilice test distributor switch is seized overr The improved circuit facilities further include the .path from main office, and wherein Ímeansis a similar test switchboard located in a branch provided for busying the path from .main oiñcej omce, a test Adistributor switch in the branch when the branch onice test distributor switch is. ofñce accessible to the branch oi’ñ'ce ltest desk, 35 seized over the path from the branch oñice test test connector switch, or switches, ‘accessible to switchboard. the branch oflice test `distributor switch and A feature of the invention resides in the novel, operable from the branch oñice test switchboard arrangement of the pulsing circuit of _a A.20o-.line through the branch oii‘lce test distributor switch test Yconnector switch having two sets oîf ~wipers for selecting line circuits in the branch o'ñice vfor 40 (one setffor each 10G-line group) and'aminor testing, and means in the main ofhce for enabling switch for selecting either set of wipers, whereby the main ofhce test switchboard and the _'main' the pulsing circuit is first controlled to raisethe oñice operator-controlled switchboard to respece wipers to a certain level, then ,controlled to rotate. tively make ‘tests on branch Ío'flîlce line circuits and the wipers to a required position in the selected verify branch oiiice line numbers over the same 45 level, next controlled Vto cause the minor .switch branch cnice test distributor switch and test conf to select one set of wipers, and later controlled nector switch, or switches'as used by the branch t'o further rotate the wipers in the selected level. Another feature of the invention concerning oññce test switchboard. _' It is an object `of the invention to provide in the 20D-line testv connector switch is that Von a` circuit facilities of the character described, new 50 testing connection the wiper selecting >>minor-` and novel means for accomplishing the 'various switch of the test connector switch is not restored circiut connections. ' _ „ to normal position unless both the test distributor Another object o_f the invention is top_rovi'de in switch and the test connector switch of the test a testing 'system of Vthe character described, ,an ing connection are released. A tester isable to improved and novel test distribtuor ‘switch serv' 55 release the test 'connector s‘w’i'tch vwithout re'leasv--> 2,562,362 4 anism is a set of switching springs 234 which are actuated by the movement of the switch shaft in the vertical direction away from its normal position, a combined test jack and busy ing the test distributor switch, and the conse quent non-restoration of the wiper selecting minor switch enables the tester to connect with a line circuit in another level of the same 100 line group by dialing only the vertical and rotary digits of the line number. switch 224, condensers 2|8 and 2|9, and a nurn ber of control relays. The test distributor switch has access to a maximum of 100 test connector A further feature of the invention relates to the novel means for inserting condensers in the testing, or listening, circuit of the test distribu tor switch when the test distributor switch is switches. .. The test connector switch (Fig. 3) comprises the well-known Strowger switch mechanism of seized by a veriñcation operator through a , selector switch. 'the GOO-point type having vertical and rotary movement. Associated with this Strowger mech An additional feature of the invention concerns anism is a set of switching springs 3|3 which are a new and novel use of the vertical off-normal actuated by the movement of the switch shaft in 15 the vertical direction away from its normal posi spring set of a test distributor switch for con trolling relays associated with the vertical step ping and the release of the test distributor switch. tion, a lO-point minor switch of a well-known v type, and a number of control relays. The regular wipers ofthe test connector switch are grouped into two groups of three wipers each, one group of wipers for selecting line circuits in a 100 line group and the other group of wipers for selecting line circuits in another 10U-line group. The various objects and features of the in The minor switch selects either one of the two vention will be understood best from a perusal sets of regular wipers and comprises a step mag of the following description of the drawings com prising Figs. 1 to 4 inclusive, which show by 25 net 350, a release magnet 355, and a set of switch ing springs 356 which are actuated by the move means of the usual circuit diagrams a sui'licient ment of the minor switch shaft in a direction amount of apparatus to enable the invention to away from its normal position. be described and understood. The test trunks on the test switchboards Fig. 1 shows the circuit arrangement of a test distributor selector switch and the basic circuit 30 (Fig. 4) each comprise a jack for enabling the tester to connect the plug ending position test elements of an associated operator-controlled ing circuit with the test trunk, a busy lamp sig switchboard. Fig. 1 also includes a numbering nal, a hold lamp signal, keys for controlling the plan for assembling the drawing sheets together release of the operated test distributor switch so that a continuous circuit drawing of the in vention may be established. 35 and the test connector switch, and a group of control relays. Fig. 2 shows the circuit arrangement of a test The position testing circuit for the test switch distributor switch, the banks of which have ac boards is indicated in Fig. 4 by only the plug P cess to test connector switches. There are other objects and features of the - invention having to do for the most part with the Y circuit details necessary to carry out the ob jects and features above enumerated. but may be of any well-known design such as Fig. 3 shows the circuit arrangement of a 200 party line test connector` switch ñtted with two 40 that shown in Fig. 1 of the Crocker Patent No. 1,691,269, dated November 13, 1928, the plug P sets of wipers and a minor switch for selecting in Fig. 4 of this specification corresponding with either set of wipers. plug P’ in Fig. 1 of Patent No. 1,691,269. Fig. 4 shows the circuit arrangement of a The main oñice trunk relay group »|73 shown test trunk on the main oiiice test switchboard, a in Fig. 4 comprises a group of control relays and trunk relay group in the main office, a test trunk condensers 483 and 484 which are automatically on the branch oiiice test switchboard, a test dis inserted into the test, or talking, conductors tributor switch in the branch office and a test when the trunk relay group is seized from the connector switch in the branch ofdce. The test operator-controlled switchboard I0 in the main trunk on the branch office test switchboard is shown mostly in block form as its circuit details 50 oiiice. The trunk relay group is connected be tween test trunk 400 of the main office test are the same as those shown for the test trunk switchboard and test trunk 440 of the branch on the main oiiice test switchboard with the dif oilice test switchboard, and is also accessed from ferences illustrated. The branch ofûce test dis the operator-controlled switchboard |0 in the tributor switch and test connector switch are shown in block form as their circuit details are 55 main oiiice over conductors |21, |28 and |23. It should be understood at this time that while respectively the same as those shown in Figs. the embodiment of the present invention dis 2 and 3 for the main oiflce test distributor switch closed and described in this specification includes and test connector switch. well-known switches of certain bank capacities, The test distributor selector switch (Fig. 1) comprises the well-known Strowger switch mech 60 the invention is not limited to the particular form shown but may utilize other bank-capacity anism of the 30D-point type having vertical and switches or other arrangement combinations of rotary movement. Associated with this Strowger mechanism is a set of switching springs |39 which the switches. It should be further understood that while a are actuated by the movement of the switch shaft in the vertical direction away from its normal 65 plurality of battery connections are shown in the position and a set of switching springs H9 which drawings for the equipment located in any one oilice, they are preferably the same battery for are actuated by the movement of the switch shaft' into its eleventh rotary position. The test dis that oiiice. Also, in order to simplify the draw ings further, such well-known facilities as busy tributor selector switch also includes various control relays, and has access to a maximum of 70 keys, jacks for enabling an attendant to plug into the various switches, spark quenching apparatus, ten groups of ten trunks each. The test distributor switch (Fig. 2) comprises the well-known Strowger switch mechanism of supervisory and release signal arrangements, ringing and tone generating equipment and the like not a part of the present invention, have the 60G-point type having vertical and rotary movement. Associated with this Strowger mech 75 been cunitted.-l 2,562,363: 6 Having described the equipment and appara tus, a detailed description of the voperation will now be given. winding of vertical magnet 260 in multiple to; battery. The off-normal spring set 234 operates with the iirst vertical step thereby opening the locking circuit to the lower winding of relay 235 and placing the release of relay 235 under the control of the vertical pulsing circuit. The op eration of off-normal spring set 235 also com pletes an obvious locking circuit to relay 230 to Testing from main ol‘ìice test switchboard to main oûice lines Upon noting that busy lamp @lll of test trunk 40 (Fig. 4) leading to the main oñîce test disn retain relay 23!) operated until after the >test tributor Fig. 2 is dark, thus indicating that test 10 distributor has been released. distributor Fig. 2 is not in prior use, tester inserts Shortly after the last vertical pulse has been Iplug P (Fig. 4) of 'his position testing circuit into received, relay 255 restores to normal »position jack J of test trunk 55. Relay 505 accordingly and switches the pulsing circuit to rotary magnet operates from ground on the sleeve conductor of 255 and relay 2,55 in multiple. The cessation oi.’ plug VP, sleeve conductor of jack J, winding of the vertical pulses re-establishes ground poten relay 505 to battery, and relay 525 operates from tial on the sleeve conductors of plug P and jack J _ ground, contact ¿llll of jack J, Winding of relay with the result that relay 505 re-operates and 52,5, resistor M9 to battery. . switches the right-hand winding of relay ¿H5 The operation of relays 555 and 525 connect a across the operate leads to hold test distributor Winding of relay Í¿i5 across the “_” and “-{-” 20 Fig. 2 operated. „ operate-leads of test distributor Fig. 2 to seize The dialing of the second digit of the test'dis the test distributor and cause the operation of tributor causes rotary magnet 255 to rotate the relays 2i5 and 225 in the test distributor. This test distributor Wipers across the selected bank seizure circuit may be traced from ground, wind level to the desired test connector bank contact ing of relay 2 l 5 (Fig. 2), resting contact oi arma 25 in the well-known Strowger manner, and also ture 2 l2, conductor 532 to Fig. ll, resting contact causes relay 255 to operate and hold during the of armature 428, armature 556, right-hand wind rotary pulsing. The rotary pulsing circuitk may ing of relay M5, resting contact of armature 553, be traced from ground, armature 222 and resting armature G22, conductor 553i to'Fig. 2, resting contact, armature 225 and Working contact, contact of armature 2 l l, winding of relay 225 to 30 armature 235_and resting contact, armature 252, battery. At armature 225, relay 525 completes a winding of relay 255 to battery, and also through circuit to the left-hand winding o1”> relay 515 to armature 257, winding of rotary magnet v255 to . battery, but the two windings of relay »i l 5 are now battery. `The operation oi relay 2115 causes relay so poled that relay M5 does not operate. At 255 to operate from ground, armatures 225, 254, armature li2l, relay 520 completes a circuit to armature 252 and .working> contact, Winding of , busy lamp fill but the tester ignores this busy relay 225 to battery. Relay 255 is of `the slow-to release type and, therefore, will remain-operated for a shortA interval after the rotary pulsinggcir signal at this time because he knows that he caused its operation. The operation of relays 2 l 5 and 220 complete obvious multiple circuits to relay 225 which in turn places ground potential f on conductor |59 to make test distributor Fig. 2 busy on the related C bank contact of the test distributor selector switch in Fig. 1. At armature 228, relay 225 completes a circuit to the lower dialing the ñrst test distributor digit, when the tester turns the dial preliminary to dialing, ground, armatures 22'?, 23?, Winding of relay 235 to battery. At armature 232, relay 235 switches the lower winding of relay 235 to ground through the resting contact of off-normal spring set 235, thus locking relay 235 to the ofi-normal spring result that relay ¿£55 1re-operates and switches the right-hand winding of relay M5 across the operate leads to hold the test distributor op erated. Should the dialed test connector be in prior cuit is opened at armature 222. As in the case of ground `potential is removed from the sleeve con ductors of plug P and jack J causing relay 505 . to restore and switch the tester’s position testing winding of relay 235, causing relay 235 to operate 45 circuit from the test leads of the test distributor and prepare the vertical pulsing circuit of the to the operate leads. The cessation of the rotary test distributor at armature 235. The operation pulses re-establishes ground potential on the of relay 235 also causes relay 235 to operate from sleeve conductors oi plug P and jack J with the set 234. . The tester then turns the dial (not shown) pre liminary to dialing, thus removing ground poten use, then wiper 253 of the test distributor en 55. counters ground potential on conductor 215 there by completing a locking circuit for relay 255 by way of armature 255 and resting contact, arma ture 255 and working contact, winding of relay armatures 451 and 255, relay 555 switches the 250, resting contact of armature 252 (relay 255 tester’s position testing circuit (partly shown) 60 now having restored), winding of relay 245 and from the test leads of the test distributor to the battery. At armatures 255 and 251i, relay 255 operate leads, thereby holding the test distribu opens the line test«le,ads to the dialed test con tor by means of the dial pulsing loop (not shown) nector. Relay 25%` operates in series with relay over operate-conductors 53! and 532. At arma 245 and, at armature 25E, connects busy tone ture `555, relay 555 disconnects the right-handing 65 through condenser 239 to the tester's position . winding of relay M5 from the operate leads. test circuit to inform the tester that the dialed , thereby clearing the operate circuit for pulsing. test connector is in prior use. At armature 255, The dialing of the ñrst digit of the test distribu relay 255 completes an obvious circuit to relay tor causes vertical magnet 255 to correspond Ziû, causing relay 2id to operate and reverse the ingly raise the shaft and wipers of the test dis battery and ground connections to operate-leads tributor in the well-known Strowger manner. £53! and 532 thereby reversing the current ñow The vertical pulsing circuit may be traced from through the right-hand winding of relay M5 and ground, armature 222 and resting contact, arma thus causing relay M5 to operate. At armature ture 226 and working contact, armature 235 and @l5 and Working Contact, relay M5 connects in-~ Working contact, upper Winding of relay 235 and 75 terupted ground potential to busy lamp 4H to _ tial from the sleeve conductors of plug P and jack J and causing relay 555 to restore. At 2,562,362 7 indicate to the tester that the dialed test con nector is in prior use. Assuming now that the dialed test connector is not in prior use, then wiper 203 does not en 8 relay 305 to correspondingly complete the pulsing circuit to rotary magnet 365 and relay 32 0, there by causing rotary magnet 365 to rotate the test connector wipers across the selected bank level to the desired line circuit bank contact in the Well known Strowger manner, and also cause relay 320 the selected test connector and, consequently, re to operate and hold during the rotary pulsing. lay 245 cannot lock up but restores shortly after The rotary pulsing circuit of the test connector relay 240 restores. Before relay 245 restores, may be traced from ground, armature 306 and however, a circuit is completed from ground, armature 223, armature 254, armature 242 and 10 resting contact, armature 3H and working con tact, winding of relay 320 to battery, and through resting contact, armature 243, winding of relay armature 33| and working contact, winding o! 255 to battery, causing relay 255 to operate and rotary magnet 365 to battery. At armature 32| lock to ground through armatures 244 and 229. and working contact, relay 320 causes relay 325 to At armature 251, relay 255 opens the rotary mag net circuit to prevent possible further rotary 15 operate. At armature 321 and working contact, relay 325 completes a holding circuit for relay stepping: at armature 259 and working contact, 330 from ground, armature 3|2 and working con connects direct ground through wiper 203 to con tact, armature 321 and Working contact, arma ductor 213 of the selected test connector to busy ture 332 and working contact, lower winding o1 the selected test connector against intrusion; and, at armature 256, completes a loop circuit 20 relay 330 to battery: at the resting contact of armature 321, opens the circuit to the upper for relay 305 of the selected test connecton counter ground potential `on conductor 213 of through armature 22| thereby causing relay 305 to operate. At armature 306 and working con tact, relay 305 completes a circuit to relay 3I0, causing relay 3|0 to operate. At armature 3|2 and working contact, relay 3|0 completes a cir cuit to relay 335 through armature 3|1, causing relay 335 to operate. winding of relay 330; and, at armature 326, short circuits the upper winding of relay 320 to make relay 320 slow in releasing when the circuit of relay 320 is opened. The opening of the circuit of the upper winding of relay 330 also opens the locking circuit of relay 335, causing relay 335 to restore. The circuits to wipers 30|, 302, 303, `301, 308 and 303 of the test connector are open at the The dialing of the first digit of the test con nector causes relay 220 of the test distributor to 30 banks of the minor switch wipers 35|, 352 and correspondingly interrupt the loop circuit of re lay 305 of the test connector at armature 22|. The interruptions of the loop circuit of relay 305 cause relay 305 to correspondingly complete the 353 as wipers 30|, 302, 303, 301, 308 and 309 are passing over line circuit bank contacts in response to the dialing of the second digit of the test connector, thereby preventing interference with pulsing circuit to vertical magnet 350 and relay 35 line circuits during rotation. Shortly after the last rotary pulse has been 320, thereby causing vertical magnet 360 to cor received, relays 320 and 325 restore. At arma respondingly raise the shaft and associated wipers ture 321, relay 325 opens the locking circuit to of the test connector in the well-known Strowger the lower winding of relay 333, causing relay 330 manner, and relay 320 to operate and hold dur ing the vertical pulsing. The vertical pulsing cir 40 to restore. The dialing of the third digit of the cuit of the test connector may be traced from test connector causes relay 220 of the test dis tributor to correspondingly interrupt the loop ground, armature 306 and resting contact, arma circuit of relay 355 or" the test connector at arma ture 3| I and working contact, winding of relay ture The interruptions of the loop circuit 320 to battery, and through armature 33| and resting contact, armature 336 and Working con 45 of relay 335 cause relay 305 to correspondingly complete the pulsing circuit to step magnet 350 tact, winding of vertical magnet 360 to battery. of the minor switch and relay 320, thereby caus The operation of relay 320 causes relay 325 to ing step magnet 350 to rotate the minor switch operate over an obvious circuit. At armature 321, wipers 35|, 352 and. 353, and also causing relay relay 325 opens a point in the circuit of the up per winding of relay 330 to prevent the opera 50 320 to operate and hold during the pulsing of the third digit. The pulsing circuit of the third tion of relay 330 in series with relay 335; and, digit of the test connector may be traced from at armature 326, short-circuits the upper wind ground, armature 303 and resting contact, arma ing of relay 320 to make relay 320 slow in re ture 3H and working contact, winding of relay leasing when the circuit of relay 320 is opened. At armature 321 and working contact, relay 325 55 320 to battery, and through armatures 33|, 336, 34| and associated resting contacts, winding of completes a locking circuit for relay 335 by way step magnet 350 to battery. At armature 32| of armature 331, armature 332 and resting con and working contact, relay 320 causes relay 325 tact. The off-normal spring set 3|3 operates to operate. At armature 326, relay 325 short with the first vertical pulse thereby causing relay 3|5 to operate and perform certain preparatory 60 circuits the upper winding of relay 320 to make relay 323 slow in releasing when the circuit to functions. relay 320 is opened. Shortly after the last vertical pulse has been The operation of step magnet 350 of the minor received, relays 320 and 325 restore. At the rest switch causes wipers 35 |, 352 and 353 to be moved ing contact of armature 321, relay 325 completes a circuit through the upper winding of relay 330 65 across the associated sets of bank contacts. lf the third digit of the test connector consists of from ground, armature 3|2 and working contact, five pulses or less, wiper 35| will test in the ñrst resting contact of armature 321, upper winding 1GO-group of line circuits, and if the third digit of relay 330, armature 331, winding of relay 335 consists of six or more pulses, wiper 35| will test to battery, causing relay 330 to operate and relay 335 to remain operated. 70 in the second 10U-group of line circuits. As the minor switch wipers 35|, 352 and 353 step off The dialing of the second digit of the test con normal, the minor switch off-normal spring set nector causes relay 220 of the test distributor to 356 operates to prepare other circuits for the correspondingly interrupt the loop circuit of relay switch. The line test leads to wipers 30|, 302, 305 of the test connector at armature 22|. The interruptions of the loop circuit of relay 305 cause 75 301 and 308 are open at contacts 246 and 241 of ' 2,562,362 vthe test `distrikuitor during the dialing of the third digit of the test connector because relay 255 operates with the iirst pulse of the third digit and remains operated for the-period of the pulsing of the third digit. Shortly after the last pulse of the third digit has been received, relays 320, 325 and 345 restore. Should the dialed line circuit be in prior use, . leads 261 and 238 Y and10 .» operating the *Y line relay (not shown) to seize a trunk circuit accessible to the selected line circuit. Operating key M1 causes relay M0 to operate and connect ground potential to negative operate conductor 43E, thereby shunting relay 2 I5 in the test distributor and «causing relay 2| 5 to restore. At armature ille, relay 2|5 removes ground potential from conductor 214 of the test connector thereby caus ing the cut-oil relay (not shown) of the selected then. ground potential will he returned over either wiper 303 or wiper 333, dependent upon Whether the dialed line circuit is in the first 10Q group or the second 1GO-group, by way of wiper 35i, conductor 21d, bank contact connected to `line to restore. winding ci relay M5 and thus causing relay M5 original circuit through the right-hand winding ' ^ ` - ' At the conclusion of the tests, the tester re leases> the test distributor, test connector and conductor 213 in Fig. 2, wiper 205i, armature 253, selected line circuit by withdrawing plug P from _armature 248 and working contact (before relay jack J and operating key 4I8. VThe removal of 255 has had suflicient time to restore after the plug P opens contact 4I4 but relay 420 cannot dialing of the third digit), armature 23|, wind restore because its circuit is maintained through ing of relay 2li) to battery, causing relay 2&5 to armature423 and the winding of relay 425. The operate and lock to ground by way of armature opening of contact 4m also removes the ground 253, resting contact ot armature 258 (relay 255 20 shunt from the winding of relay 425, and relay now having restored), and armature 2l3 and 425 immediately operates to'complete a multiple working contact. At armatures 2H and 2&2, re circuit through the right-hand winding of relay lay 2 lil reverses the battery and ground connec M5 at armature 421. The removal of plug P tions to operate~leads 43! and, 432 thereby re also opens the circuit to relay 405 causing relay versing the current flow through the right-hand 25 405 to restore and, at armature 40B, open the to operate. At armature M3 and working con of relay 4I5 but the multiple circuit through ar tact, relay 555 connects interrupted ground po mature'421 retains a circuit through the'right tential to busy lamp 4i l to indicate to the tester hand ‘winding of >relay M5'. The ~operation of that the dialed line circuit is in prior use. 80 key M8 shunts down both relays 420’and 425 Assuming now that the dialed line circuit is and the holding circuit to the test distributor not in prior use, then ground potential is not operate-leads 43| and 432 is now open at arma returned to conductor 214 in Fig, 2 and, conse tures 422 and 421. ' quently, relay 2li) cannot operate and reverse Should the test distributor release ñrst by the the current flow through the right-hand winding 35 opening of the holding circuit at armatures 422 of relay M5. Instead, a circuit is completed for and 421, the test connector is guarded by ground relay 350 of the test connector from ground, potential through armature 3|9. Should the armature 32E and resting contact, contact 35i cf test connector release ñrst by the opening of its minor switch spring set 355, armature 313 and holding circuit at armature 22|, the test con« working contact, winding of relay 352 to battery, 40 nector trunk is busied from ground through ar causing relay 335 to oper te and lock to ground mature 250 and wiper 203. The release circuit by way of armature 352 and conductor 213. At of the test distributor is completed from ground, armature 35i, relay opens the pulsing circuit to armature 222 and resting contact, armature 22B step magnet 355 of the minor switch: at arma and resting contact, armature 23|, winding‘oiî ture 315| and working contact, prep-ares a pulsing 45 release magnet 210 to battery, and magnet 2-10 circuit to rotary magnet 335 to enable the tester causes the release of the shaft and wipers in to later advance the test connector Wipers to the well-known Strowger manner. As the shaft another line circuit by dialing another digit, or reaches its normal position, off-normal spring setV digits; and,l at armature 353, opens a point in 235 is operated to unlock relay 230, thereby open the release circuit of the minor switch. As pre 50 ing the circuit of release magnet 210 at arma viously indicated, relay 225 in the test distrib ture 231. The restoration of relay 225 opens the utor restores shortly after the third digit of the locking circuit to relay 255 at armatureA 229, and test connector has been dialed, and ground po the restoration voi" relay 255 removes groundl tential is extended to either wiper 323 or 305 potential from wiper 203 at armature 259 and (as the case may be) or" the test connector by 55 ground potential from wiper 204 at armature Way of armature 2de, armature 2l3 and resting 258. contact, resting Vcontact of armature 223, arma Two release circuits are employed in the test ture 253, wiper 254, conductor 2id to Fig. 3, wiper connector (Fig. 3), ones for causing the restora 35i and selected bank contact cf the minor tion of the test connector switch shaft and asso switch. The ground potential on wiper 303 or 60 ciated wipers, and the other -for causing the 353 causes the cut-oli relay (not shown) of the restoration of the minor switch-and associated selected line circuit (not shown) to operate, and wipers 35i, 352 and 353. The release circuit for also guards the selected line circuit against in the shaft and wiper 30l, 302, 303, 301, 308 and trusion. The tester’s position testing circuit is 309 is completed from ground, armature 306 and now connected through to the selected line cir 65 resting contact, armature 3H andv resting con cuit over test conductors 25? and 268, and any tact, armature SIS, windingV of release magnet or all of well-known tests can be applied to the 310 to battery, and magnet S10-causes the release selected line circuit. Since such tests form no of the shaft and associated wipers in the well part of thepresent invention, the details will not known Strowger manner. As the shaft reaches be included in this speci?cation other than to 70 its normal position, oir-normal spring >set 313 indicate that by operating key fig-l1 (Fig. 4), the is operated to unlock relay SI5, thereby open tester may remove ground potential from the ing the- circuit of_ the release magnet 310 at cut-ofi relay (not shown) or" the selected line cir armature _3l6. VThe removal of multiple cuit. thereby placing the line-relay (not shown) ground potential from conductor 213 at arma of theselected line circuít'across the line test 75 tures 3| 9 and 259 opens the locking circuit of A2,562,362 12 309 to the next bank contacts of the same bank relay 340. The release circuit for the minor level. By successive single pulses, wipers 36|. switch and associated wipers 35|, 352 and 353 is 302, 303, 301, 308 and 309 can be advanced to the completed from ground, armature 32| and rest successive bank contacts of the same bank level ing contact, contact 351 of minor switch off-nor until the last set of bank contacts in the level mal spring set 356, armature 3|8 and resting are reached. In this manner, the tester can contact, armature 343, winding of minor switch select and test all of the line circuits associated release magnet 355 to battery, and the operation with the same bank level without releasing the of release magnet 355 restores wipers 35 |, 352 and used test connector. 353 to their normal positions. As wipers 35|, Should the tester desire to select a line circuit 352 and 353 reach normal position, off-normal 10 in another bank level of the same '1GO-group of spring set 356 is restored to normal position line circuits after having selected and tested a thereby opening the circuit of release magnet line circuit in a different bank level, he then op 355 at contact 351. Should the shaft and asso erates key 4|2 momentarily, thus causing relay ciated wipers fail to restore when the circuit of release magnet 310 is completed, a circuit to a 15 430 to operate. At armature 428 and working contact, relay 430 connects battery through re delayed alarm circuit (not shown) is completed sistor 429 to operate-conductor 432, thereby from ground, armature 3|2 and resting contact shunting down relay 220 of the test distributor and armature 3|4 and working contact. Should and retaining relay 2|5 in the operated position. the minor switch and associated wipers 35|, 352 and 353 fail to restore when the circuit of re 20 At armature 2|1, relay 2 |5 retainsl hold relay 225 operated to prevent the release of the test dis lease magnet 355 is completed, a circuit to the tributor. At armature 22|, relay 220 opens the delayed alarmvcircuit (not shown) is completed loop circuit to relay 305 of the used test con from ground, armature 3|2 and resting contact, nector, thereby causing the completion of the armature 3|4 and resting contact and contact 25 circuit to release magnet 310. The operation of 358 of minor switch off-normal spring set 356. release magnet 310 causes the restoration of the After having selected a line circuit over test shaft and associated wipers in the well-known trunk 40, test distributor Fig. 2, and test con Strowger manner but in this instance relay 340 nector Fig. 3, should the tester desrie to “hold” is retained in the locked position by means of the selected line circuit for the time being and use his position testing circuit for another pur 30 the ground potential through armature 259 and wiper 203 of the held test distributor and con pose in the meantime, he can do so by removing plug P from jack J of test trunk 40. The with ductor 213 of the test connector. As a conse quence of relay 340 remaining locked, the circuit drawal of plug P causes contact 4|4 of jack J to to release magnet 355 of the minor switch remains open with the result that relay 42|) is retained in the operated position through armature 423 open at armature 343, and the minor switch is, and the winding of relay 425, and relay 425 im therefore, not released. The tester next dials the mediately operates. At armature 421, relay 425 ñrst and second test connector digits of the de completes a multiple circuit through the right sired line circuit, omitting the third digit since hand winding of relay 4| 5; and, at armature the minor switch wipers 35|, 352 and 353 re 426, completes the circuit of hold lamp 4|3. The 40 mained in the operated position as a result of withdrawal of plug P also causes relay 405 to the non-release of the minor switch. The test connector operates up and around responsive to restore and, at armature 406, open the original circuit through the right-hand winding of relay the dialing of the ñrst and second digits of the test connector in the manner previously ex 4|5 but the multiple circuit through armature 421 retains a circuit through the right-hand 45 plained, and the tester’s position testing circuit is extended over line test-leads 261 and 268 to the Winding of relay 4|_5. The tester may later re line circuit just selected. turn to the held connection on test trunk 40 by Should the dialed test connector Fig. 3 be in re-inserting plug P into jack J in which event prior use when the test distributor Fig. 2 at relay 405 re-operates and relay 425 is shunted down thus placing the test connection in the 50 tempts to seize that test connector. busy lamp 4| I . same condition as it was when set up originally. The tester may abandon the held connection on test trunk 40 without re-inserting plug P into jack J by operating key 4| 8, thereby releasing of test trunk 40 is caused to ilash in the manner previously explained to inform the tester that the dialed test connector is in prior use. The tester can then either abandon the connection by with the held connection in the manner previously 55 drawing plug P i‘rom jack J and operating key explained. ' 4|8 to effect a complete release, or leave the con nection remain as it is with busy lamp 4|| con After having selected a line circuit in one of tinuing to flash. In the latter instance, busy the 10U-groups of line circuits in the manner lamp 4| | will continue to