US2914624A - Automatic routiner for selector and connector switches - Google Patents

Description

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J. S. MURRAY AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Nov. 24, 1959 Fil d July 9, 1957 BY f GP K.

Nov. 24, 1959 J. s. MURRAY AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR swrrcass Filed July 9, 1957 11 Shee ts-Sheet 2 INVENTOR.

JAMES S. MURRAY BY 15? ATTY.

Nov. 24, 1959 J, 5. MURRAY AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Filed July 9, 1957 11 Sheets-Sheet 3 m M #6 M2: m m 8 5m; W M 1 N Il\mmm km 1 S W N3 il 1? 5 1 an t o m v l J 65 8 i 56 i w o z q um lllll n l u n 18 n 193 E U J WNW l II? j in A. ,1 I a NSF--- OL 2m moswdm 2. EESEEE i3 $28228 95 @w u n 33 w 303 2922518 Q kowfi m m: m

ATTY.

Nov. 24, 1959 s MURRAY 2,914,624

AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES INVENTOR.

JAMES S. MURRAY FIG. 4

Nov. 24, 1959 J. 5. MURRAY 2,914,624

AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Filed July 9, 1957 4 ll Sheets-Sheet 5 INVENTOR.

JAMES s. MURRAY Nov. 24, 1959 J. 5. MURRAY 2,914,624

AU TOMATI C ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Filed July 9, 1957 ll Sheets-Sheet 6 O) O m INVENTOR.

JAMES s MURRAY ATTY.

Nov. 24, 1959 J. s. MURRAY 2,914,624

AUTOMATIC ROUTINER FOR SELECTOR'AND CONNECTOR SWITCHES Filed July 9, 1957 11 Sheets-Sheet 7 (ll/(l (Tl/(l P rr- 1 a ,5; (f m 0 ,1 co m m 0) G) O) 03 w m u (D (O INVENTOR.

JAMES s MURRAY ATTY.

FIG. 7

Nov. 24,1959 .1. s. MURRAY 2,9

AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Filed July 9. 1957 lISheets-Sheet 8 AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Filed July 9, 1957 Nov. 24, 1959 J. s. MURRAY 11 Sheets-Sheet 9 INVENTOR.

JAMES S. MURRAY BY K5 6? ATTY.

NOV. 24, 1959 5, MURRAY 2,914,624

AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES F I I INVENTOR.

JAMES S MURRAY ATTY.

Nov. 24, 1959 J S. MURRAY AUTOMATIC ROUTINER FOR SELECTOR AND CONNECTOR SWITCHES Filed July 9, 1957 11 Sheets-Sheet 11 INVENTOR.

JAMES S. MURRAY ATTY.

circuitry for seizing successive ones of United StatesPatentO AUTOMATIC ROUTINER FOR SELECTOR AND I CONNECTOR SWITCHES James S. Murray, Tampa, Fla., assignor to General Telephone Laboratories, In corporated, Chicago, Ill., a corporation of Delaware Application July 9, 1957, Serial No. 670,693

13 Claims. (Cl. 179-17521) This invention relates in general to telephone systems and more particularly to routining equipment therein;

It is an object of this invention to provide a novel, compact, inexpensive and simplified routiner for automaticallytesting each toll selector switch and combination local an'dtoll connector switch in an exchange for seizure of the called line, transmission'of ringing current, battery reversal, and busy test.

A feature of this invention is the provision of a circuit for busying each connector after it is tested, until all of the connectors-ma predetermined group are found to be simultaneously bum-whereupon the busy condition is removed from all of the connectors at one time, and testing of another group of connectors isinitiated.

Another feature of this invention is the novel means for simulating a call originating at a toll switchboard,

and thereafter simulating the operation of the operators ring key, in order to test the transmission of ringing current responsive to a toll call. I

Further. features will be evident upon examination of the following disclosure in which: 1 Figure 1 shows atypical dual access trunkcircuit of the type used in an ofiice served by this routiner, with a toll switchboard and an inter-toll first selector to indicate the origin of toll and non-toll calls, respectively;. 9

Figure 2 shows a toll transmission selector of the type used in conjunction with this routiner; 1

Figure 3 shows a toll intermediate selector in block diagram form, and a simplified circuit diagram for a typical combination local and toll connector used in conjunction with this routiner;

Figure 4 shows the distributor switches andassociated the selectors in the exchange; I

Figure 5 shows the relays and-the associated circuitry for the four major tests thatare connected on each switch train;

Figures 6 and 7 show the distributor switches and relays that are used to busy the connectors after they have been tested; Y

Figures 8 and 9 show the equipment for transmitting digital impulses into the seized selector in order to complete a switch train that can'be tested; a

Figure 10 shows the control mechanism that-is used for transferring from one test to another, together within the early morning hours when trafficis light,,,by de-l.

pressing key 701 in Figure 8. This operates relay 705,

effective to cause the operation of magnets 977 and 980 2,914,624 Patented Nov. 24, 1959 and ground at contacts 708 is then extended through Figure 9 and over lead 768 to Figure 4, and the relays of Figure 4 are then operative to cause the operation of distributor switch magnet 470. This distributor switch is operated until an idle selector is found, indicated by an absence of ground on lead 20, and the idle selector is then seized. When a selector is seized, relays 715 through 740 (Figure 8) operate in conjunction with the mechanism shown in Figure 9 to transmit digits 11991 into the seized selector. Pulsing contacts 734, by opening and closing the closed loop to the selector, are effective to transmit these impulses. The first digit positions the toll transmission selector of Figure 2, the second digit positions the toll intermediate selector shown at the left of Figure 3, the digits 99 cause the combination toll and local connector to seize the test trunk (contact 99 in each connector in the exchange being used as a test trunk), and the last digit 1 is provided in order to routine those connectors wherein a digit 1 is required on party line connector groups, this last digit causing no trouble on other connectors having access to individual lines. Those toll connectors having trunk and level hunting features are also tested by digits 11991, by providing appropriate strapping in the contact banks. For example, in a trunk hunting connector, the test trunk may be connected to contact 90, reached by trunk hunting from contact -99 to and in a level hunting connector, the test trunk-may be connected to contact 01, reached by level hunting from contact 99.

When the digits have been pulsed into the connector, and the connector switches through in the well-known mannen'ground on contact 379 (Figure 3) is extended over lead 392 to'Figure 5, and this grooundinitiates the test sequence on the switch train. Relays 505 through 520 test the ringing function of the connector, whereafter the relays 525 through 545 test the battery reversal function of the selector, whereafter relays 550 through 570 test the operation of the switch train with the test trunk marked busy, and thereafter relays 575 through 595 test the delayed ringing function of the connector on a call that is simulated to originate at a toll switchboard. When this testing is completed, relays such as 671 and 681, and distributor switch wipers such as wiper 623, cause the tested connector to be marked busy. Thereafter the sequence is repeated except that the toll intermediate selector will be unable to seize the connector that is marked busy, and will seize another connector in the same group. In this manner, each of the connectors in a particular group (a maximum of ten being provided for in this routiner) is marked busy, and when all of them are marked busy, relay 608 operates. Distributor magnet 620 then operates, whereafter the connector switches in the next successive group, which have their control leads 317 connected to the second. rotary contact of the various wipers associated with magnet 620, are tested. Operation of relay 608 also causes magnet 979 (Figure 9) to operate, thereby changing the digit sequence to 12991. Thus, the toll intermediate selector will thereafter search for idle selectors in its second level, rather than the first level. Operation of relay 608 is also effective to operate magnet 875, and thereby step wiper 878 one rotary position; and to remove the busy condition from the tested group of toll connectors.

Thus, successive groups of connector switches are tested by changing the digital sequence from 11991 through 10991, a difierent toll transmission selector switch being used for each connector that is tested. After these first ten groups of connectors have been tested (each group having. a maximum of ten connectors therein), wiper 878 reaches the tenth bank contact and ground is thereby (Figure 9). Magnet 977 causes wiper 962 to rotate to the second bank contact, and magnet'980 causes wiper 965 to be restored to the home position as shown. Thereafter, the digits transmitted by Figures 8 and 9 will be 21991 through 20991. Thus, a different group of toll intermediate selectors is used throughout this test, and a dilferent group of 100 connectors are thereby tested. In like manner, wipers 962 and 965 (Figure 9) are sequentially operated so that digits sequences are changed from 11991 through 00991, providing there are that many con nectors in the oflice. Where less connectors are provided, a lead such as tied to contact 642' (Figure 6) is provided, and will be effective to cause the termination of the test sequence. Further details of the arrangement will be apparent upon an examination of the following detailed description.

DETAILED DESCRIPTION 1" he loll switch train In order to present a clear picture of my invention, I will first describe the function of the telephone system, as embodied in Figs. .1, 2 and 3, independent of the routining mechanism. First, let us assume that a call is initiated at the toll switchboard shown in Figure 1. The operator inserts a plug into the appropriate jack (not shown) and ground is thereby placed on dial control lead 15 in the well-known manner. Relay 130 operates, and closes contacts 131 and 133. Contact 131 completes an obvious operating circuit for relay 150, and relay 150 is thereby operated. Contact 151 places ground on negative line lead 16; contact 152 connects ring control lead 14 to relay 160; contact 153 completes an obvious operating circuit for slow-to-operate relay 140; contact 156 completes a point in the operating circuit of relayv 120, this circuit being now opened at contact 132; and contact 154 connects the ground at contact 172 to control lead 20, thereby marking the circuit busy to the inter-toll first selector and to the test circuit, as will be described in fur-therdetail below. I

It should be observed here that the ground at contact 151, which is connected to contact 142 and negative line lead 16, causes an unbalance condition at the line incoming to the toll transmission selector shown in Figure 2.- When relay 140 operates, and closes contact 141, contact 142 is opened and thereby removes the contact 151 ground from the negative line lead 16, and thereby completesza balanced loop circuit for the toll transmission selector, including negative line lead 16, contact 141, contact 133, and positive line lead 17. The effect of. this change from the unbalanced to the balanced condition, as will become more evident during a discussion of the toll transmission selector, is to indicate to the selector that the call originated at a toll switchboard, since a call originating from the inter-toll first selector would seize the toll transmission selector by placing a closed loop across leads 16 and, 17, and would not ground lead 16 prior to completing. this loop. This ground conditions the toll transmission. selector so as to prevent automatic ringing of the called. line, making it necessary for the operator to depress her.

ring-key (not shown) in order to start the ring.

After seizure is completed, the operator at the toll switchboard operates her telephone dial, digital impulses being thereby placed on dial control lead '15, and relay 130 follows these impulses in the well-known manner..

133 follows the digital impulses, and thereby repeats these impulses over the above mentioned loop circuit to the toll transmission selector, in the well-known manner.

Slow-to-release relay 150 remains operated during dialling. due to the intermittent ground at contact 131, and contact 120 remains operated during dialling as, a result of the..-

intermittent ground at contact 132. When diallingis completed, relay 120 restores and removes the short circuit from the repeater coil.

After the dialling has been completed, and the toll switchboard has been connected with the called subscribers substation, the operator actuates her ring-key and thereby places ground on lead 14. This ground causes the operation of relay .160, and contact 161 thereby places ground on the loop circuit incoming to the toll transmission selector. This ground, occurring subsequent to dialling, has the effect of initiating the called line ring cycle, as will become more evident in thefollowing dis cussion. It should be kept in mind, particularly during an anlysis of the toll-call-ring-test, that the input circuit to the toll transmission selector is grounded both before and after dialling, in the normal toll call.

In the event that the calling incoming to the switch train is received over the inter-toll first selector, ground on the C lead of the inter-toll first selector is extended over lead and contact 155 to relay 170. Relay 170 operates, closing contacts 171 and 175, thereby connect: ing a balanced loop across lines 16 and 17 of the toll transmission selector, including the and leadsof the inter-toll first selector. Thus the momentary-unbalanced condition that occurs whena call is received over the toll switchboard, does not: occur when the call is received over the inter-toll first selector.

Operation of toll transmission selector n toll call' Let us now consider the toll transmission selector shown in Fig. 2, and the effect of the momentary unbalanced line condition. The unbalance ground at contact 151 is extended'through contact 142, lead 16, and con- .3;! 233, to repeater coil 248 andv relay 215. Relay 215 1 OPQEQIQSJ thereby closing contacts'216 and 217. Contact 215 i ineffective at this tim butcont 2 com.- p ctes an o vi us operatin circuit for relay .230.

SloW-to-release relay 230 operates and the contacts associated therewith cause the following operations: Contact 227 prepares a point in the operating circuit of relay 260, this circuit being new open at contact 218; contact 228 connects ground through one winding of relay 280 to control wiper C; contact 229 completes an operating circuit for relay 265, said circuit extending through vertical olf-normal contact 272 and the lower winding of relay 265; and contact 231 connects ground through contact 226 to the upper winding of relay 255 and to relay 275. Relay 255 operates, and locks throughits lower winding and contact 258 to ground at contact 229. Contact 257 is closed, but is ineffective at this time. Relay 265 operates over the above described circuit, whereupon contact 266 opens thecircuit to coil 263. The ground at contact 268 is ineffective at this time. Slowto-operate relay 275 doesnot operate at this time, since the incoming line to the toll transmission selector becomes balanced and relay 210 operates, opening .con-. tact 226, before relay 275 operates.

When the unbalanced loop circuit is replaced with a 2 15 remainsoperated over this circuit, and relay 210 now operates. Contact 211 is thereby closed, but is inefiective at this time, and contact 212 connects ground over an obvious operating circuit to relay 220. Relay 220 operates, and the contacts associated therewith causes the following operations: Contact 221 completes an operating circuit for relay 250, extending fromv ground atcontact 284, and through contacts 221-and 259; contact 222 prepares a point in the operating circuit of the vertical magnet, said circuit being open at contact 213 at this time; contact 223-places a multiple ground on the lead t nding to relay 280; contact 224 places amultiple ground on the holding circuit of relay 25 and the operating circuit of relay 265; and contact 226 is opened to prevent relay 275 from operating at this time.

Relay 250operates over the above described circuit. Contacts 251, 252, and 253 arethereby closed, contacts 251 and 252 being effective at this time, whereas contact 253 connects an operating ground to relay 240 over an obvious circuit.

Relay 240 operates, but the contacts associated therewith have no effect other than to connect relay 250 across the outgoing trunk circuit, in place of relay 270 and the secondary of the repeater coil. a,

The toll transmission selector is now prepared for vertical stepping, relays 210, 215, 220, 230, 240, 250, 255, and 265 being now operated. Relays 210 and 215 follow the dial pulses, being restored and operated on each pulse, relays 220 and 230 remaining operated during the pulsing due to their slow-release characteristics. Relay 260 operates with the first dial pulse, and remains operated during the pulsing, the circuit extending from ground at contact 218 through contact 227. Contact 261 is thereby closed, and is effective to positively prevent relay 250 from restoring in the event that relay 220 restores during the opening and closing of contact 212. The circuit of contact 261 extends through the bottom winding of relay 250 and cam springs 259 through contacts 261 to ground at contact 253. The ground pulses placed on contact 213 by the intermittent operation of relay 210 during pulsing, cause relay 265 to be energized over the upper winding with each pulse and also causes the vertical stepping of the switch wipers due to energization of vertical magnet 294. This pulsing through the upper winding of relay 265 prevents this relay from restoring when the vertical off-normal spring 272 is opened at the first vertical step of the wipers. Vertical off-normal spring 273 is effective, at the first vertical step,

to connect ground from contacts 224 and 229 through contacts 288, 293 and 296 to relay 290 and battery, causing relay 290 to operate. Contact 291 is thereby closed, preparing a point in the operating circuit of the rotary magnet 295.

After the last pulse of the first series, relay 265 restores and ground at contact 267 is thereby effective to energize rotary magnet 295. Contact 266 closes a point in the circuit of repeater coil winding 263, but this circuit is held opened at this time at contact 241.

When the ground is placed on contact 267, and rotary magnet 295 is energized, the wipers of the toll transmission selector take the first rotary step. Energization of magnet 295 causes contact 296 to be opened, whereupon relay 290 restores, and contact 291 is thereby opened. The opening of contact 291 causes rotary magnet 295 to restore, whereupon contact 296 is again closed when relay 290 operates, to again close contact 291. Ground at contact 267 is thereupon effective to cause the rotary magnet to take the second rotary step. -In this manner, relay 290 and magnet 295 are alternately operated to cause the rotary stepping of the switch wipers. When an idle toll intermediate selector is found, which is indicated by resistance battery connected to the C wiper of the toll transmission selector at one of the rotary positions, relay 280 operates over a circuit extending from ground at contacts 223 and 228 through the lower winding of relay 280 and out over the C lead to the resistance battery. Relay resistance of 280 is such that only contact 287 is closed, contact 288 being thereby opened to prevent relay 290 from again operating to step the rotary magnet. When relay 280 operates initially, to close contact 287, ground at contacts 224 and 229 is connected to the upper winding of relay 280 over contact 287 and vertical offnormal contacts 273, to operate relay 280 fully. The contacts associated with relay 280 then cause the following operations: Contacts 281 and 282 connect the outgoing line leads through contacts 216, 242 and 244 to the upper winding of relay 250, a loop circuit being thereby completed that includes relay 250; contact 283 connects the extra control lead to ground at contact 252, and to a mutliple ground through contact 257 to contact 277; contact 284 removes ground from the operating circuit of relay 250, but this relay remains operated from ground at contact 253 through contact 261 and cam spring 259 as described above; contact 285 opens the circuit to the upper winding of relay 265 and vertical magnet 294 to prevent their operation in the event that relay 210 restores; contact 286 shorts out the lower winding of relay 280; and contact 289 opens a point in the circuit to release magnet 297.

When relay 280 operates, to terminate the rotary hunt ing of the toll transmission selector, the circuit is prepared to'repeat later pulses to the toll intermediate selector and the combination local and toll connector, relays 210, 215, 220, 230, 240, 250, 255 and 280 being held operated. Pulsing contact 216 of relay 215 follows the remaining pulses of the called number, thereby repeating these pulses to the succeeding switches. Relay 250 remains operated until after the last digit is repeated, since relay 260 is operated duringthe pulsing of each digit and holds operated until the next succeedingswitch is seized, whereupon a resistance battery loop is connected across the and leads of the toll transmission selector which holds relay 250 operated, through its upper winding, during the interdigital time periods.

As will be described below regarding the connector switch, when relay 260 restores followingthe last digit, a holding circuit for relay 250 is not established by the connector switch, and relay 250 restores. This, in turn, causes relay 240 to be restored, due to contact 253 being opened. Restoration of relay 240 completes a circuit from the repeater coil winding 263 through contacts 266, 274, 241, 216, and 281 to the negative line; and another circuit from coil 264 through contacts 276, 243 and 282 to the positive line. The circuit is then ready for ringing, relays 210, 215, 220, 230, 255 and 280 being held operated.

When the operator at the toll switchboard operates the ring-key (not shown), ground on lead 14 causes relay to operate and close contact 161. Ground is thereby placed on the incoming loop of the toll transmission selector. Relay 215 remains operated as a result of the ground on lead 16, by relay 210 is released as a result of the ground on lead 17. Release of relay 210 causes contact 212 to be opened, and relay 220 is thereby restored. Contact 226 is closed when relay 220 restores and a circuit for operating relay 275 is thereby extended from ground at contact 231 through contact 226 to relay 275 and battery. The other contacts associated with relays 220 and 210 are ineffective at this time.

Relay 275 then operates, and the contacts associated therewith cause the following operations: contacts 274 and 276 open the circuit to the secondary of the repeater coil, contact 277 is opened to remove ground from the EC lead and thereby cause ring start in the connector; contact 278 is closed, but this circuit is ineffective at this time; and contact 279 is closed to complete an operating circuit through contact 247 to the bottom winding of relay 265. Operation of relay 265 opens contacts 266 and 267, and closes contact 268, but these operations are ineffective at this time. The removal of ground from the EC lead causes ringing of the called line to be initiated, and this proceeds automatically until the called party answers. When the operator releases the ring-key, relays 210 and 220 are again operated, and relays 275 and 265 are restored, but this has no effect on the ring cycle, as will become more evident from an analysis of the connector circuit.

When the called party answers, the loop is closed across the outgoing trunk and relay 270 operates over a circuit extending from ground through the lower winding of 270, through coil 264, through contacts 276, 243 and 282 to the positive lead, through the loop and back on the .7 negative lead through contacts 281, 216, 241, 274 and 266 to coil 263, and through the upper winding of relay 270 to battery. Operation of relay 270 closes contact 271, whereupon relay 235 operates over an obvious circuit. The contact associated with relay 235 cause the following operations: Contacts 234 and 236 cause a battery reversal across the incoming loop by connecting negative lead 16 through contact 234 to repeater'coil winding 249, and positive lead 17 through contact 236 to repeater coil winding 248 and negative battery at relay 215; contact 238 places ground on the EC lead; and contact 239 is closed, but inefiective at this time, since relays 260, 265 and 275 are not operated. The toll transmission selector is now prepared for conversation, relays 210, 215, 220, 230, 235, 255, 270,'and 280 being operated.

When the conversation is completed, and called party has disconnected, causing relays 270 and 235 to release, the operator may wish to re-ring the called party. The release of relay 235, and battery reversal on the trunk circuit, would indicate that the call had been terminated,

and the operator could then proceedto ring the called party in the same manner as above described.

Release of the toll transmission selector occurs when the operator disconnects from the circuit thereby releasing relay 130. The loop circuit across leads 16 and 17 is thereby opened, whereupon relays 210 and 215 restore. Restoration of relays 210 and 215 causes relays 220 and 230, respectively, to restore. Contacts 224 and 229 open the holding circuit for relays 255 and 280, and these two relays then restore. Ground at contact 232 completes a circuit for operating release magnet 297 including contacts 289 and vertical off-normal contacts 298. When the switch has restored to normal, contact 298 opens to release relay 297.

Now let us assume that instead of finding an idle line,

an all trunks busy condition is found during the rotary stepping of the switch wipers in the toll transmission selector. The rotary motion of the switch wipers, caused by the alternate operation of relay 290 and motor magnet 295 as above described, continues until the wipers are rotated to the eleventh rotary position. Cam springs 259 and 293 are then opened, contact 293 being effective to prevent the reoperation of relay 290, and the opening of contact 259 being effective to cause the release of relay 250. Contact 202'is closed to prepare a circuit for placing a 120 IPM source to the line 16. Restoration of relay 250 causes relay 240 to restore, whereupon the '120 IPM signal is connected through contact 202 and a condenser to contacts 241, 274, 266, 274 and coil 263 through the upper winding of relay 270 to battery. On the first pulse of the 120 IPM signal, relay 279 operates, and closes ground to relay 235. Operation of relay 235 causes a battery reversal in a manner above described, and this battery reversal'combined with the 120 IPM signal induced in the repeater coil causes a supervisory lamp to flash at the operators position at a 120 IPM rate, to pro vide visual supervision. Relays 270 and 235 remain operated until the connection is released by the operator.

Operation of toll transmission selector on inter-toll call Let us now assume that the incoming call is received over the inter-toll first selector instead of the toll switchboard. The ground at the C lead of the intertoll first selector causesoperation of the relay 170 in Figure l, the circuit extending from the C lead over lead 20, through contact 154 to relay 170 and negative battery. Contacts 171 and 175 are thereby closed, whereupon the and leads of the'inter-toll first selector are connected, respectively, to the and leads of the toll transmission selector. This places a balanced loop across leads 16 and 17, and the momentary unbalanced condition does not occur.

As a result of the balanced loop placed across leads 16 and 17, relays 210 and 215 operate simultaneously, instead of consecutively as in a case when the call is initiated at the toll switchboard. Relays 220 and 230 are thereby operated, at approximately the same time, and relays 265, 250, and 240, operate as described above. It should be noted here that relay 255 does not operate, which is the distinguishing feature between .a call received over the inter-toll, first selector and a call received over the toll switchboard, the operation of relay 255 being prevented by the opening of contact 266 at the time that contact 231 is closed.

Dialling, switch-through, and line seizure operations are the same as described above, but there is a slight difference with regard to ringing the called line. As described above regarding the toll switchboard, ground on contact 277 is extended through contact 257 of relay 255 to the EC lead through contact 283 when relay 280 .op= crates. Thus, there is a delayed ringing feature on toll calls, since ground is maintained on the EC lead until the operator operates the ring key even though relays 250 and 24 9 release following seizure of the called line. How.- ever, when the call is received over the intertoll first selector, contact 257 is opened and the ground on contact 277 is not placed on the EC lead when contact 283 closes. When contact 283 closes, the ground at contact 252 of relay 250 places ground on the EC lead. Then when relay 250 restores following seizure of the called line, contact 252 is opened and the ground is removed from the EC lead. ,Slow-to-release relay 240 restores shortly thereafter, and ground at 245 is extended through contact 256 and contact 283 to the EC lead. This mo.- mentary removal of ground automatically causes the ring cut-elf relay in theconnector to restore, and thereby closes the ring generator to the line and causes ringing of the called line. Thus, the ringing occurs automatically, and there is no .need to use the ring key as described regarding a call originating at the toll switchboard.

Operation of connector switch In Fig. '3, a combination local and toll connector of the type described in Reissue Patent 21,768, issued to Norman H. Saunders on April 8, 1941, and a toll intermediate selector, are shown. Applicants Figure 3 is a modified version of Figure 3 in the Reissue Patent 21,768, a number of circuits having been eliminated as being unneces, sary .to a description of applicants invention. The following generalized description may be clarified, if dc.- sired, by reference to the above mentioned reissue patent.

As the call proceeds through the switch train having originated either from the toll switchboard or the inter.- toll first selector shown in Figure l, the toll intermediate selector of Figure 3, is seized, and the wipers of the toll intermediate selector are moved in vertical and rotary directions in the well-known manner. We will now as sume that the wipers of the toll intermediate selector have found the combination local and toll connector, shown in Figure 3, by engaging contacts associated with leads 315, 316, 317, and 318, in the well-known manner. As in the case of the toll transmission selector, the rotary movement of the toll intermediate selector wipers is stopped responsive to finding resistance battery on the control lead. Referring to Figure 3, the resistance bat.- tery circuit extends from relay 310 through both sets of vertical off-normal springs, to lead 317 and outover the C lead to the test relay in the toll intermediate selector (not shown) and ground. A loop circuit is also closed for operating relay 303, the circuit extending from the upper winding of relay 303, through contact 322, out over the negative line lead 318, through the loop circuit in the toll intermediate selector, back over the positive line lead 315 through contacts 328, through the bottom of relay 363, through vertical off-normal spring to lead 317, and back into the toll intermediate selector and ground. Relay 303 operates to complete an obvious operating circuit for relay 304. Relay 304 closes contact 333 and direct ground is thereby placed on the lower winding ofrelay 3G3 and on relay 310. Contact 334 is closed when relay 304 operates, thereby preparing a point in the impulsing circuit to the vertical and rotary magnets. The lower contacts of relay 304 open the circuit to the release magnet, to prevent the relay from .operatingwhen the vertical ofi-normal springs associated .impulses over the local impulsing circuit by way of its lower contacts. Slow-to-release relay 304 remains operated during the pulsing of contacts 332. The first series of pulses repeated by relay 303 are effective to cause the vertical movement of the combination local and toll connector switch wipers, and the second series of digit repeated by relay 303 cause the rotary movement, all in the well-known manner. When the wipers reach the intended rotary position busy relay 305 operates if the called line is busy, and switch-through relay 312 operates if the called line is idle. Relay 306 operates from ground on the impulsing circuit during numerical stepping of the switch wipers, and relay 310 restores following said stepping, all in the manner described in said reissue patent. Relay 307 then operates and locks from ground on the EC lead. Relay 306 restores. following operation of relay 312 when the called line is seized. The specific details of this operation will be better understood from an examination of the above mentioned reissue patent.

If the line is busy, the upper contact of relay 305 completes the circuit for sending a busy tone to the calling line, extending from the tone generator through contact 350 (relay 307 operated) to the upper contacts of relay 305, through contact 323 (relay 301 operated over contact 336 when relay 305 operates) and back to the calling line over the negative conductor. If the called line is not busy, relay 312 operates. The upper and lower contacts of relay 312 then connect the called line to the and leads of the toll intermediate selector and contact 379 completes a locking circuit for relay 312. Negative line lead 318 is now seen to extend through contacts 323, 347 and 374 to wiper 382; and positive line lead 315 extends through contacts 327, 354 and the lower contact of relay 312 to wiper 387. Relay 307 is now held operated over EC lead 316, by way of its lower contacts. When the ground on the EC lead is removed, either by the operators ring-key or the automatic operation of the toll transmission selector as described above, relay 307 restores and completes the ringing circuit including the lower contacts of relay 307, wiper 387, the called substation, wiper 382, contacts 374 and 346, and the upper winding of relay 307. Ringing then proceeds automatically, until the called party answers, and it shouldbe noted that re-grounding of the EC lead will not reoperate relay 307 to terminate the ringing.

When the called party answers, relay 307 operates over the direct current loop closed in on the called subscribers telephone, thereby interrupting the ringing circuit and restoring the above mentioned loop circuit including contacts 347 and 354. Relay 307 remains operated, due to ground'on the EC lead. The switch train is then in condition for the parties to converse.

After the call is completed, the call is released from the operators position (or from the Inter-Toll First Selector) by removal of ground from the control lead, thereby causing the switch train to release in the wellknown manner. It should be noted that the operator can, before releasing the connection, re-ring the called party by depressing her ring-key. This would again restore relay 307, and ringing would occur until the called party answers to again re-operate relay 307.

Finding an idle toll transmission selector With the above background information in mind, let us now consider the operation of the routining equipment shown by applicant, and the relationship of this equipment to the above described toll switch train. The testing operation is started by depressing start key 701 in Figure'8, which operates relay 705 over an obvious circuit. Relay 705 operates, and the contacts associated therewith cause the following operations: Contact 706 is closed, but this circuit is ineffective at this time since it is opened at contact 717; contact 707 completes a locking circuit for relay 705, extending from ground at contact 711; contact 708 completes a circuit through tne manual selection key 945 in Figure 9 to lead 768 and contact 709 opens the normalizing circuit for rotary switch wipers 962 and 972.

Let us first consider that branch of lead 768 that extends through Figure 10 into Figure 11, and to relays 805 and 810 in parallel. Relays 805 and 810 are thereby operated, and the contacts associated therewith cause the following operations: Contacts 802, 806 and 811 open the normalizing circuits of the distributor switches shown in Figs. 6 and 7, contacts 806 and 811 being connected to individual stepping magnets in the same way that contact 802 is connected to stepping magnet 620 (it should be noted here that there are eight such distributor switches, only 4 of which are shown); contacts 803 and 812 open the operating circuits of release magnets 876 and 871, respectively; and contact 804 completes obvious operating circuits for relays 815, 820, 611 and 612. Thus, it is seen, that when relays 805 and 810 restore (at the conclusion of testing) the distributor switches in Figs. 6 and 7, and the rotary switch in Fig. .11, are normalized.

Since relay 615 is slow-to-operate, relays 820, 611 and 612 operate first, and ground on contacts 818 and 8:19 is thereby extended to magnets 620 and 630 before relay 815 is operated. Wipers 622 to 627, and 632 to 637, are thereby rotated to the first bank contact. Relay 815 then operates, causing magnets 620 and 630 to restore, and relay 825 operates over an obvious circuit extending from contact 816. Contact 824 opens the circuit to relays 815 and 816, causing their restoration; contact 826 completes locking circuit for relay 825, to ground on lead 768; and contact 827 prepares another operating circuit for relays 815 and 820.

The ground on lead 768 is also extended to relay 435, through contact 443 to relays 405 and 410, through contact 406 to magnet 450, and through contact 423 to test lamp 1 in Fig. 10. Relay 405 is slow-to-operate, and therefor magnet 450 operates to rotate wipers 452 through 457 one rotary-step before relay 405 opens contacts 406.

When magnet 450 operates, and steps Wipers 452 through 457 to the first rotary position, ground at contact 411 is extended through contacts 429 and 418 and through wiper 454 to wiper 474 and through contacts 464 and 471 to magnet 470. Simultaneously, a ground is placed on the opposite side of relay 460, thereby preventing it from operating, through wiper 455 and contact 412 to contact 427 and ground. Thus, magnet 470 operates and steps wipers 472 through 476 to the first rotary position. The toll transmission selectors in the telephone exchange, are successively connected by way of their control leads, such as lead 20, to the bankcontacts associated with distributor switch wipers such as 474. If the toll transmission selector associated with the first bank contact is busy, ground on 420 will then be extended through wiper 474 and contact 464 to the right side of relay 460, to prevent this relay from operating, and also will be extended through contact 471 to magnet 470, whereupon magnet 470 will cause the wipers associated therewith to take a second rotary step. This rotary movement continues, until an idle switch train circuit is found, in which case ground will not be marked on lead 20 to short out relay 460.

Relay 460 then operates to contact 427 and ground, and the contacts associated therewith cause the following operations: Relay 715 is operated over a circuit extending from ground at contact 461, through contacts 446 (relay 445 being held operated from ground at contact 851), 537, 558 and 758; contact 462 extends ground to relay 415, causing this relay to operate; contact 463 extends ground from wiper 455 and contact 427 to wiper 474 and control lead 20, to thereby mark the circuit under test busy; contact 464 opens the circuit to magnet 470 to prevent the ground at wiper 455 from operating this magnet and contacts 465 and 466 prepare points in the loop circuit extending from leads i6 and 1'7 through wipers 475 and 476.

When relay 415 operates, locking ground is extended from contacts 411 through contacts 429 and 416 to relay 415. Contact 417 places ground on wiper 457 and thereby on wiper 473, so that when wiper 473 reaches the last rotary position, ground is extended through wiper 453 to relay 430 and battery. Contact 413 removes ground from the last contact associated with wiper 474. As will become obvious later, the operation of relay 450 due to the wipers such as 473 reaching the last rotary position, is efiective to bring another group of toll transmission selectors into play. This function will be discussed below.

Seizing the test trunk When relay 715 operates over the above described circuit, contact 713 completes the loop circuit for seizing the toll transmission selector (including contacts 734, 597, 557, 532, 465, and 466); and contact 714 completes the circuit initiating the transmission of pulses into the seized selector switch.

Contact 714 completes a circuit extending from ground at contact 706, through contacts 714, 762, 944, 717, 726, and 731 to relay 735 and battery. Relay 735 is thereby operated, and the contacts associated therewith cause the following operations: Contact 734 opens the above mentioned loop circuit, thereby causing the first digital impulse to be placed on said loop, causing the wipers of the toll transmission selector in the first vertical step in the manner described above; contact 738 connects ground over lead 905 to magnet 951; and contact 739 completes an obvious operating circuit for relay 740. Relays 730, 735 and 740 operate sequentially, and are rnargined so as to provide digital impulses of appropriate length. As long as ground is maintained at contact 731, the pulsing continues. Relay 735 operates relay 740, which operates 730 and thereby releases 735, terminating the first pulse. Release of 735 releases 740, which releases 730, whereupon 735 again operates to start the second pulse and so forth. However, pulsing ground on lead 905, and the position of the rotary switch wipers in Fig. 9, are effective to operate relay 720 and thereby terminate the transmission of pulses, when a predetermined digit has been transmitted. This feature will now be described.

Each time the loop circuit is opened, contact 738 extends ground over lead 905 to Fig. 9.. With the first impulse, this ground is extended through contact 911 to the stepping magnet 951 associated with wiper 961 of the corresponding rotary switch. Wiper 961 is therefore moved to the first bank contact, and oil-normal contact 960 is closed. When wiper 961 reaches this first contact, ground at contact 722 (Fig. 8) is extended over lead 904 through wipers 962 and 961, and through contact 915 to relay 910, with a parallel circuit through relays 720 and 910 in parallel. Relay 720 operates, whereupon contact 717 opens the circuit to relay 735, to prevent further pulses being placed on the loop to the toll transmission selector; contact 721 completes a temporary locking circuit for relay 720 to ground at contact 960; contacts 718 and 722 open the operating circuit of relays 910 and 720; and contact 723 completes an obvious operating circuit for relay 725. Relay -91!) operates, and transfers leads 905 and 906 to contacts 912 '12 and 914 respectively; and contact 916 completes a locking circuit for relay 910 extending through contacts 916, 746, 558, 446 and 461.

Operation of relay 725 opens the pulsing circuit-of relay 735 at contact 726, prepares a circuit at contacts 727 for operating rotary magnet 957, and completes a circuit at contact 728 extending over lead 917 through contact 921 to operate release-magnet 952. Rotary wiper 961 is thereby restored to the home position (as shown) and when contact 960 opens, the ground is removed from lead 908 and thereby from relay 720, causing relay 720 to restore. Restoration of relay 720 causes relay 725 to be restored, whereupon magnet 952 restores and the operating circuit of relay 735 is again completed. This operation of relays 720 and 725, and subsequent restoration of wiper 961, relay 720 and relay 725, provides the interdigital time period following the pulsing of the first digit into the toll transmission selector (which in this case, due to the position of wiper 962, was the digit 1).

The sequential operation of relays 735, 740 and 730 is again started to place pulses on the loop circuit,and ground at 738 is now extended over lead 905 through contact 912 and through contact 923 to magnet 953 and battery. Magnet 953 operates as the first pulse is placed on the loop circuit, and rotates wiper 964 to the first contact, closing contact 963. Ground on contact 722 is then extended over lead 904, wipers 965 and 964, to relays 920 and 720, in parallel. Relay 720 operates as before, ground at contact 963 providing the locking circuit. Relay 920 operates, and at contacts 922 and 924, transfers leads 917 and 913 to the operating circuit of release magnet 954, and stepping magnet 957, re.- spectively. Contact 926 extends lead 906 to wiper 967', in preparation for the next digit. Contact 928 completes a locking circuit for relay 920, extending through contact 928 to the above described locking circuit for relay 910. Contact 929 prepares a point in the operating circuit of relay 930. When relay 925 operates, ground at contact 728 is extended over lead 917 through contacts 922 and 931 to release magnet 954, causing wiper 964 to be restored to the home position as shown. When the home position is reached, and contact 963 is opened, ground is removed from lead 908 and relay 720 is released as described above. When relays 720 and 725 have both restored, ground at contact 724 is extended over contacts 729, 929 and 934 to operate relay 930,

whereupon relay 930 operates and locks to the locking circuit of relays 910 and 920. Since relay 725 restores before relay 930 operates, the circuit from contacts 727 does not operate magnet 957 at this time. With relays 720 and 725 restored, the pulsing circuit of magnet 735 is again completed, and the sequential operation of relays 730, 735 and 740 again occurs to place further digital impulses on the loop circuit to the toll transmission selector. As a result of the first two digits, which in this case were the digits 11, the wipers of the toll transmission selector and toll intermediate selector have been operated to the first level, and an idle connector seized.

As the third digit pulsing takes place, ground at contact 738 is extended over lead 905 through contacts 912, 924 to magnet 955 and battery. Magnet 955 is thereby operated one time for each pulse that is placed on the toll transmission selector loop, thereby causing wiper 967 to rotate across the bank contacts. Contact 966 is closed at the first step to prepare a locking ground for relay 720. When wiper 967 reaches the 9th rotary position, a circuit is completed from ground at contact 722 through lead 904, wipers 969 and 967, and through contacts 926, 718 to relay 720 and battery. Relay 720 then operates, to interrupt the pulsing circuit of relay 735, nine pulses having been transmitted, and relay 720 locks to ground at off-normal contact 966. When relay 725 operates from contacts 723, ground at contacts 727 is extended over lead 918 through contact 933 to magnet 957, and

. 13 wiper 969 is thereby caused to take one rotary step from the normal position. Ground at contacts 728 is extended over lead 917 through contacts 922 and 932 to release magnet 956. Wiper 967 is thereby restored to the home position, opening contact 966, whereupon the holding ground of relay 720 is removed and relay 720 restores.

It should be observed that the vertical stepping of the connector has now occurred.

' Relay 720 restores relay 725, and relay 735 is again operated to start the next series of pulses. Wiper 957 is again rotated in the manner just described, due to -the strap which connects the first two contacts associated with wiper 969. Thus, the toll transmission selector which has received pulses corresponding to digits 119, receives pulses corresponding to a fourth digit of 9 also, thereby causing the rotary stepping of the connector switch wipers.

When relay 725 operates following this digit, ground at contacts 727 is extended over lead 918 through contact 933 to magnet 957, and magnet 957 rotates wiper 969 to the third contact. Relays 720 and 725 again restore, in the manner described above, completing the pulsing circuit of relay 735. The fifth digit is thereby started, and at the first pulse, ground at contacts 738 is extended over lead 905 through contacts 912, 924 to magnet 955, and wiper 967 is moved to the first bank contact. Ground is then extended from contacts 722 to lead 904, through the third bank contact associated with wiper 969, and through wiper 967 to contacts 926 and 914, and over lead 906 to contact 718 and relay 720. Thus, relay 720 interrupts the operating circuit of relay 735 after the first impulse, thereby completing the transmission of impulses to the toll transmission selector, impulses corresponding to digits 11991 having been transmitted. When relay 725 operates, ground is extended through contact 933 to magnet 957, thereby rotating wipers 969 and 976 to the fourth bank contact. Ground at contact 976 is extended to relay 960 and battery, whereupon relay 940 operates and locks to ground over the above described holding circuit for relays 910, 920 and 930. Ground at contact 943 is extended through offnormal contact 968 to magnet 958, thereby releasing wipers 969 and 976 to the home position as shown. Ground at contact 943 is also effective to operate one of; the lamps in each of banks 970 and 971, due to the position of wipers 972 and 974, respectively, to indicate the group of connectors being tested. Further impulsing is now prevented by contact 944, which prevents relay 735 from reoperating.

Incomplete call test Responsive to the above described digital impulsing, wipers 382, 386 and 387 should become connected with test trunk leads 393, 392 and 391, respectively, and relay 312 should operate since the test trunk is not marked busy. In the event that this does not occur, and ground at contact 379 is not connected to lead 392 within a predetermined time period, an incomplete-call-alarm is operated. This time period is measured by the timed ground pulses on contact 941, and relays 780 through 795, in the following manner.

When relay 940 operates, the first ground pulse on contact 941 is extended over lead 781 and through contacts 508, 527, 552, and 778 to relay 780 and battery. Relay 780 operates and locks from ground at contact 777, the ground extending over lead 781, through contacts 509, 526 and 551, and back over lead 786, to 779, relay 780 and battery. Ground at contact 777 is also extended to relay 785. but as long as the ground pulse is maintained at contact 941, and therefore through contact 783 to the opposite side of relay 785, relay 785 cannot operate. However, when the first ground pulse ends, ground at contact 777 operates relay 785 over an obvious circuit. When the second ground pulse is placed on contact 941, it is extended over theabove described cir- 14 cuit through contact 784, and through contact 791 to relay 790 and battery. Relay 790 operates, and locks through contact 792 to the above mentioned holding circuit. Ground at contact 777 is then extended through contact 789 to relay 795 and battery. However, relay 795 does not operate until the ground pulse is removed from contact 941, since this ground is extended through contact 784 to the battery side of relay 795 and prevents relay 795 from operating. When the second ground pulse ends, relay 795 operates over the circuit including contacts 777 and 789, whereupon ground at contact 794 is extended over lead 770 to relay 760 and battery, to operate the alarm circuit (not shown), relay 760 being locked operated over contacts 761 and 747. Ground at contact 793 operates lamp 10 associated therewith, indicating an incomplete call failure; and is extended over lead 801 to relays 840 and 845, these two relays then operating. It should be noted here that if relay 505 operates at any time during the sequence of operation of relays 780790, contact 509 would be opened and thereby cause relays 780 and 785 to release, preventing relay 795 from operating. In that event, there would be no alarm and relays 840 and 845 would not be operated.

Ring test on inter-toll call When relay 312 in Fig. 3 operates in the normal mannet, as described above during an analysis of the connector circuit, ground at contact 379 is extended over wiper 386 through-test lead 392 into Fig. 5, and then through contacts 548, 571 and 447, to wiper 772, relay 505, and battery. Relay 505 then operates. Contact 504 completes a loop circuit including the A.C. relay 520 and leads 391 and 393, said leads extending to Fig. 3 and completing the loop including the ring generator; contact 506 prepares a circuit for operating relay 510, sad circuit extending over lead 781 through Fig. 10 and into Fig. 9, and through contact 941 to ground ringing generator; contact 507 completes a temporary locking circuit for relay 505, extending from contact 521; and contacts 508 and 509 open the above described circuits for causing the incomplete call alarm. When relay 940 operates, following the pulsing of the last digit in the series 11991, an interrupted ground circuit is extended over contact 941 through contacts 506 and 511 to relay 510 and battery. Relay 510 operates, contact 513 being effective to place ground on the left side of relay 515, and contacts 514 being effective to extend the ground that operated relay 510 through contacts 523 and 517 to the right side of relay 515. Thus, during the time that the ground pulse is applied to contact 941, relay 515 is prevented from operating. Relay 510 locks operated to ground at contacts 521, and to an alternate ground including contact 507 and the original operating ground of relay 505. If the circuit under test is operating properly, ringing generator applied to the above mentioned loop-circuit including relay 520 will cause relay 520 to operate, whereupon the ground at contact 521 is transferred to contact 522, and thereby extended through contacts 587 and 577, to magnet 776 and battery. Magnet 776 is thereby operated, stepping wiper 772 to the second contact, and thereby transferring ground from lead 392 in Fig. 3 from relay 505 to relay 525. Relay 510 then restores, and relay-515 is prevented from operating.

However, if the circuit under test is functioning improperly, at least to the extent that there is a defect in the ringing circuit, relay 520 does not operate over the above described loop circuit. In that event, relay 510 operates as described above, and when the ground pulse is removed from contact 941, and thereby removed from the right hand side of relay 515, ground at contact 513 causes relay 515 to operate. The next ground pulse at contact 941 is then extended over lead 781, and through contacts 506, 51 4, 523, 516; and 579. to relay 760 and battery. Thus, at the beginning er the second grounding impulse at contact 941, relay 760 operates. Relay 760 locks operated from ground at contacts 748, through contacts 761 and 757 to relay 760. Operation of relay 760 closes the alarm circuit contacts, to indicate that a fault has been located in the tested switch. Lamp 1 on Fig. 4 is operated to indicate the test that failed, over a circuit extending from ground at contact 708, through contacts 945 and 423.

Battery reversal test Let us now assume that the ring test has been successfully completed, and that wiper 772 has advanced to the second rotary position as described above.

The second of the four tests that are sequentially performed on each of the circuits to be tested, is the test for determining that proper battery reversal occurs when the called party answers. This test, which involves relays 525, 535, 540 and 545 will now be described.

When wiper 772 steps to the second rotary position following the first test sequence, ground on lead 392, originating at contact 379 in Fig. 3, is extended through wiper 772 and over lead 797 to relay 525 and battery. Relay 525 operates, and the contacts associated therewith cause the following operations: Contacts 526 and 527 open points in circuit extending to the incomplete-call relays; contact 528 connects resistor 538 across test trunk leads 391 and 393, the establishment of this loop circuit being the equivalent of an answer by the called party;

contact 530 completes an obvious circuit for operating relay 540; contact 531 prepares a point in the operating circuit of relay 535; contact 532 removes the shunt from the 1000 ohm resistor R, thereby placing this resistor in the loop circuit extending from leads 16 and 17, this circuit extending from lead 1 6 over wiper 475 to contact .465, the 1000 ohm resistor, contacts 557, 597, 734, -713 and 466, to wiper 476, and back to lead 17. Should relay 235 operate in the usual manner, responsive to the called party answer represented by the closed loop at contact 528, and thereby reverse the battery on leads 16 and 17, negative battery extending from relay 215 through coil 24S and contact 236 is. extended over the above described loop circuit to the bottom of the 1000 ohm resistor and through contact 531 to the bottom of relay 535. Relay 535 then operates, and the contacts associated therewith cause the following operations: Contact 533 prevents slow-operating relay 540 from operating; contact 534 completes a locking circuit for relay 535 including contact 530; contact 536 completes an obvious operating circuit for relay 545; and contact 537 opens the holding ground circuit of relays 715, 910, 920, 930 and 940.

Relay 545 operates over the above described circuit, and the contacts associated therewith cause the following operations: Contact 543 completes a point in the circuit for marking the test line busy; contact 544 connects ground at contact 530 through contacts 544, 587 and 577 to magnet 776 and battery, thereby operating magnet 776 and causing wiper 772 to rotate to the third rotary position, thereby opening the circuit to relay 525 and causing it to restore; contact 546 completes a locking circuit for relay 545, including contact 554; and contact 547 prepares a point in the operating circuit of relay 550. When relay 525 restores, relay 535 also restores, but relay 54S remains operated to the ground at contact 554.

In the event the battery reversal does not occur, ground on lead 17 is extended over the above described circuit to the bottom of the resistor and through contact 531 to the bottom of relay 535. Thus, relay ,535 does not operate to open the operating circuit of relay 540. In that event, after relay 525 operates, ground at contacts 530 is extended through contact 533 to relay 54b and battery. Relay 5'40 operates, and ground at contact 539 is extended through contact 579 to lead 776, and then relay 768 and battery. Relay 76.0 operates, and locks to groundat contact 743, the circuit extending through contacts 761 and 757. Operation 0 Inlay 760 causes the alarm circuit to be completed, to indicate that a fault has occurred in the circuit under test.

Busy test As pointed out above, when relay 535 operates during the reverse-battery test, relay 715, 910, 920, 930 and 940 are restored. Contact 713 then opened the line loop, and the switch train under test was released. Now, when relay 535 restores following the reverse-battery test, contact 537 completes the circuit extending from ground at contact 461 over contacts 446, 537, 558, 758, to relay 715 and battery. Thus, relay 715 is again operated, to complete the line loop circuit at contact 713; and also to complete the operating circuit of relay 735 extending from contact 706 through contacts 714, 762, 944 (now closed since relay 940 has restored), 717, 726 and 731. The sequential operation of relays 730, 735, and 740 again occurs, and digits 11991 are again pulsed into the toll transmission selector. After the last digit has been pulsed into the circuit, ground on wiper 976 is extended to relay 940, which operates and locks as described above, and is also extended over lead 782 through contacts 547, 571 and 447 to wiper 772, and

through the third bank contact to relay 550 and battery. Relay 550 is thereby operated, and the contacts associated therewith cause the following operations: Contacts 551 and 552 open points in circuits extending to the incomplete-call relays at the bottom of Fig. 10; contact 553 completes a circuit extending from the timing ground at contact 941 to contacts 508, 527, 553 and 562, to relay 565 and battery; contact 554 removes the locking ground from relay 545, and relay 545 restores; contact 555 prepares a point in the locking circuit of relay 560; contact 556 connects the bottom winding of relay 560 through contact 532, contact 465, and wiper 475, tonegative line lead 16 of the toll transmission selector; and contact 557 removes a shunt from the 1000 ohm resistor R thereby placing resistor R across line leads 16 and 17 of the toll transmission selector circuit.

When switch wiper 386 of the combination local and toll connector shown in Fig. 3 engage thetest contacts associated with lead 392, the ground on lead 392 extending from contacts 543 and 529 indicates a busy condition, and there should be no battery reversal in the toll transmission selector. If battery reversal does occur, ground potential is connected to lead 16 and therefor through contact 556 to the left side of relay 560, and relay 560 is prevented from operating. In that event, relay 565 operates from the ground pulse at contact 941, and contact 566 of relay 565 completes a circuit to the alarm relay, extending over contact 569 and lead 770 to relay 760. Relay 760 operates and locks, and also completes the alarm circuit, in the manner described above.

However, if relay 560 operates promptly, as it should on a busy trunk (the battery for operating this relay being extended from relay 215 of Fig. 2 and out over lead 16 in the above described circuit) contact 562 associated with relay 569 will open and prevent the operation of relay 565. The other contacts of relay 560 are effective as follows: Contact 558 opens the 910, 920, 930 and 940, causing these relays to restore; contact 559 com? pletes a locking circuit for relay 560 extending through ground at contact 555; and contact 561 completes a circuit extending from the ground pulse circuit at contact 941 over lead 781, and through contacts 508, 527, 553, 561 and 568, torelay 570 and battery. Relay 570 operates, and the contacts associated therewith cause the following operations: Contact 564 completes a point in the circuit for ground leads 16 and 17, to thereby simulate a toll call; contact 567 extends ground over contacts 578 and 577 to lead 769 and magnet 776, causing magnet 776 to operate and stopwipers 772 and 773 to the fourth bank contact; contact 569 completes a locking circuit for relay 570 extending through contact 573 to ground; contact 56,8 opens the original operating circuit of relay 570;

17 contact 571 is opened and contact 572 closed, to thereby transfer wiper 772, from control lead 392 to the circuit including ground at contact 706, this circuit being now open at contact 714 due to the previous opening of contact 558, so that ground on 706 is not extended over the circuit at this time.

Delayed ring test on toll call As a result of the above operations, the circuit of relay 550 is opened, both at wiper 772 and at contact 571, and relay 550 restores. Contact 555 then opens the locking circuit to relay 560, causing relay 560 to restore. Restoration of relay 560 closes contact 558, thereby reoperating relay 715, and the reoperation of relay 715 completes the loop circuit to the leads 16 and 17, by closing contacts 713. Ground at contact 706 is then ex tended through contacts 714 to relay 735, to start the sending of digital impulses representing digits 11991 into the same toll transmission selector for the third time; and this ground at contact 706 is also extended over lead 761 through contacts 572 and 447 to wiper 772, and then over the fourth bank contact to contact 592, relay 575 and battery.

Relay 575 operates, and the contacts associated therewith cause the following operations: Contact 573 opens the locking circuit of relay 570, but slow-release relay 570 does not restore immediately; contact 574 completes an obvious circuit to slow-operating relay 580; and contact 576 closes before slow-to-operate relay 580 operates and before slow-release relay 570 restores, extending ground through contacts 564 and 583 to both sides of the incoming line, over leads 16 and 17. This unbalanced condition on the incoming line, which indicates a call originating at the toll switchboard should cause relay 255 to operate during the seizure of the toll transmission selector, and thereby prevent the automatic ringing of the called telephone. The purpose of this test, then, is to check the operation of the toll transmission selector on a delayed ring toll call.

The above described ground circuit from contact 564 is opened by the operation of relay 580, or restoration of relay 570. Then, during the transmission of digital impulses into the switch train, relay 575 restores (due to the opening of contact 572), and thereby restores relay 580.

When test lead 392 is seized and grounded, due to the operation of relay 312 (Fig. 3), this ground is extended through contacts 548, 571, and 447 to wiper 772, and through the fourth bank contact to contact 592 and relay ,575. Relays 575 and 580 operate as before, except that contact 564 is now open and prevents leads 16 and 17 from being grounded. When relay 580 operates, ground on lead 392 is extended through contacts 548, 582 and 586 to relay 505. Relay 505 then operates, in a manner described above for the first ring-test, and connects relay 510 over contacts 511 and 506 to the interrupted ground lead at contact 941. Contact 504 completes the loop circuit through A.C. relay 520. If a ring occurs, and relay 520 operates, ground at contact 521 is extended over contacts 587 and 578 to relay 760 and battery. Thus, due to the transfer contacts of relay 580, the operation of relay 520 is effective to cause the alarm condition.

If the switch train is functioning properly, relay 520 does not operate, and the ground pulses at contact 941 are effective to cause the test to proceed. As described above, relay 510 operates at the beginning of the first ground pulse, and relay 515 operates at the end thereof. The second pulse is then extented through contacts 506, 514, 523, 516, 581, and 591 to relay 585, and relay 585 operates. Contact 584 completes an obvious operating circuit for relay 595, and contact 586 opens the circuit to relay 505, but relay 505 is held operated by ground at contact 521. Relay 595 then operates, and contact 596 of relay 595 completes an obvious operating circuit 18 for relay 590. The'other contacts. of these relays are effective as follows: Contacts 587 and 588 transfer the ground circuit from contact 521 from the operating circuit of alarm relay 760 to the operate circuit of release magnet 775, said circuit including off-normal contact 774; contact 589 opens the operating circuit of relay595, causing it to restore; contact 591 opens the operating circuit of relay 585, causing relay 585 to restore; contact 592 opens the circuit to relay 575, causing relay 575 to restore; thereby restoring relay 580; and contact 593 completes a locking circuit for relay 590 including contacts 593, 548, and control lead 392 to contact 379 in Fig. 3.

It should be noted here that during the time relay 595 was held operated, the line loop was open at contact 597 and ground at 598 was effective to hold relay 215 operated. This line condition, as pointed out during an analysis of the toll transmission selector, is the equivalent of the actuation by the operator of her ring key, and transmission of ringing generator from the connector switch should start. If relay 520 does not operate before the next ground pulse on contact 941, this pulse will be extended over contacts 506, 514, 523, 516, and 579 to alarm relay 760'and battery. If A.C. relay 521 does operate, the group of tests is concluded, and ground at contact 521 is extended through contact 588 to magnet 775, restoring wiper 773 to the home position as shown; and also extended over lead 483 to relay 420 and battery. Relays 505 and 510 restore when contact 521 is opened; and contacts 504-and 513 then cause relays 520 and 515, respectively, to restore.

Initiation of another'test sequence Operation of relay 420, which indicates that the test has been completed, causes the following operations: Contact 419 completes the circuit for operating magnet 470 extending through contacts 426, 432, wiper 456, to magnet 470, and wipers 472 to 476 are thereby stepped one step; contact 421 completes an obvious operating circuit for slow-operating relay 425, the operation of relay 425 being effective to open the above described operating circuit for magnet 470 at contact 426, and open the circuit to relay 460 at contact 427; contact 422 completes a circuit extending from ground at contacts 708 over lead 903 through manual contacts 945 and over lead 768 through contacts 422 and out on lead 764, through Fig. 10, to relay 850 and battery; and contact 424 completes a temporary locking circuit forrelay 420, including contacts 461, 446, 537 and 558. When magnet 470 operates, and rotates the associated switch wipers, leads 16, 17 and 20 of the tested switch train are opened, and the switch train releases, whereafter relay 590 restores due to the removal of ground from lead 392.

When relay 850 operates, over the above described circuit, ground at contact 848 operates relays 840 and 845, ground at contact 849 completes an obvious operating circuit for relay 855, relay 445 is restored due to removal of ground from contact 851, and a locking circuit for relay 850 is completed from ground through contact 852and contact 861. This. locking circuit prevents relay 850 from restoring before relay 860 operates, and is necessary since the operating circuit of relay 850 is opened at contact 422 when either relay 445 or 460 restores to open the holding circuit of relay 420. When relay 445 restores. contact 446 opens the ground circuit extending from contact 461 to relays 715, 910, 920, 930 and 940, and these relays then restore.

It will be remembered that atv the time the tested switch train is released, relays 805 and 810 are held operated from ground at contact 708, that relay 825 is held operated at contact 816, that ground at contact 804 is then'extended over wiper 874 and lead 692 to relays such as 61] and 612 to hold these two relays operated, and that wipers 622 to 637 have been rotated to the first rotary position. Then, during the test sequence, when an idle toll transmission selector is found and seized,

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