US1694170A - Telephone system - Google Patents

Description

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H. In, FRIENDLY 'I'BLIPHOII 5X57:

Filed m. 16. 1921 6 Shoots-Shut 1 Inventor Herheri-PI-Frien dlg yM" f Elm Dec. 4,1928. 1,694,170-

H. M. FRIENDLY vTELEPHONE 51 515 and m. 16. 1921 a Shouts-Shoot 2' Invarflur Atlys jw /rw a. M. FRIENDLY frlmrnon- SYSTEM Film; 000N 16, 4.92!

'Dec. 4, 1928.

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1,694,170 H. M. FRIENDLY TELEPHONE sYs'rnu Filed Dec. 16. 192} 6-'Shee1' s-Sheet 5 N v Q g 8 I "i I 2 w o o k 5' g R M v Q R RN) g 7 K m E2 j] XWYM Dec. 4, i928.

H.'M. FRIENDLY TELEPHONE SYSTEM Filod'boc. 16. 1921 6 Sheets-Sheet 6 Mum, A 3% MZD nOm

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Inventor HE Pb EfiP'I'FIiEHdlH mmm Aim

Patented Dec. 4, 1928.

UNITED STATES PATENT oF IcE- rmmznnr MIL, FRIENDLY, or PORTLAND, OREGON.

'rnnnrnoim SYSTEM.

Application med December 16, 1921.

The present invention has for its broad objects the metering of telephone calls com 7 account variable initial charge values depending upon thehour at which the call is made, and also an additional charge thereto, depending uponthe hour and the duration of the connection.

I so

" the call.

and an additional different meter reg1stra-- cations Ser.

6. Means for metering an initial charge and also a charge depending upon the duration of the call and upon the destination of That is to say, an initial charge tion will be made to different destinations for the same duration'of connection.

0. Means for metering a different initial charge and a different duration charge depending upon the time of the day the call is made. That is to say, calls of equal duration will have a different meter registration depending upon the time of day the call is made, though the calls may have the same origin and destination, the variations depending upon a variable initial charge and also upon a variable duration charge.

d. Means is provided whereby if the call is made to certain groups of lines, no. initial or duration charge will be registered.

The foregoing, and other novel objects of the p'resentinvention, and the invention itself, will be understood from the following description thereof, together with the accom Figs. 1 to '10 panying drawings designated inclusive.

Reference is made to my co-pending appli- No. 420,018, filed Oct. 27, 1920; Ser. No. 510,016, filed Oct. 24, 1921; Ser. N 0. 540.779; filed March 3, 1922; Ser. No. 548,165, filed March 30, 1922. v

Fig. 1 is an apparatus unit involved in the invention.

Fig. 2 are exchange impulse devices com ,mon to a plurality of subscribers lines and called line.

. same Serial no. 522,842.

other equipments, which impulses are subject to control in a secondarymanner by apparm.

tus associated with connections made, the said control being in accordance with predetermined charge factors which are in turn controlled by conditions which are variable, depending upon tratfic and rate factors.

Fig. 3 shows a first selector of the present invention, in co-operation with a second selector'and a connector having access to a Fig. 4 shows the relation of the first selector in Fig. 3 to other first selectors of its group. 1

Fig. 5 shows a lineswitch and associated meters of the present. invention.

Fig. 6 is a somewhat more detailed illustragon'of the devices indicated by a, b, and a in Fig. 7 is a somewhat more detailed illustration of the devices indicatedby d and e in Fig. 2.

Fig. 8 shows the way the various figures are assembled to display the apparatus of the present. invention, the conductor lines runing understood to be continuations of the lines.

Fig. 9 shows a portion of Fig. 3, and in admng towardv the margins which register bedition thereto, a special intermediate seleo-- tor J introduced intoan alternative path to selector SS of Fig. '3.

An equipment element associated in the said' alternative path serves to bar connections to pay telephones.

Fig. 10 shows a schematic-plan of a wiper and cooperating level of bank contacts of the apparatus unit A. The lowermost wiper and bank level is shown, though it is to be understood that it represents each of the levels.

To associate the necessary control apparatus with the meter devices individual to each subscribers line with the lineswitch thereof (as is shown in my pending application Serial No. 420,018, filed Oct. 27, 1920) entails installing special apparatus more or less cost- 1y, for each line, and which requires ofiice space and maintenance in proportion to this quantity. Relating the apparatus for controlling the meter devices, which are individual to-each of the subscribers lines, with the first selectors reduces the quantity of the said apparatus in the ratio of the number of first selectors to the number of subscribers lines and individual terminating lineswitches. This in itself eifects a saving in equipment containing space and maintenance. Howsity thereof has such controlling manently the ends and objects of the present invention invention contemplates not ever the present the 1 a aratus .for control only associatin ling the meter evices with the first selectors,

- but that this ap aratus will not be so assothe selector as are necessary b c om can a c seized after the pl'ished, .tomaintain a correlation of the duration: meter devices, restore and to unseize and the selector when the connection is to be terminated.

, The resent invention would be employed in telep one eirchan e systems where it is desired to encourage t a use of the service at certain periods of the dayl of generally light traffic and to discourage t e asset the service during periods of the day of generally heavy the use of trafiic,.so as to conduce toward the employment of the installed equipment under a condition of higher service factor than would ensue should the service be induced solely atthe whim or inclination of the subscribers, without the incentive for them to adapt the service to economic considerations.- To this end not only would the rate charged to the subscriber initially. for the establishment of the call be varied throughout the various hours of theda corresponding directl to the generaltra c demands. but

I a p emental charge based upon the duration oi an established connection will also be varied throughout the various hours of the day corres ndingrdirectly to the traffic demands. a two charges, that-is, initial charge and the duration char e, may

or may-not be varied'corresponding y. In

addition to the said two basis of charges, the

factor oi destination will also enter, and again, the initial char e and the gd'uration c arge will enter into t e total charge made for the connection. The charges willfbe recorded on meter devices so that the initial charge will be represented by'one or more units, and the duration charge will be represented b one ormore units for each predeterm'ine period of duration, for example, one oi two units for each half minute of duration. To this will enter one or more units dependingu 11 what the destination of the call is so t at calls to certain'lines will involve a higher initial charge, and perhaps, though not necessaril y, a higher duration charge than others, all factors being variable according to the time of day the service is established and durated.

Charging for telephone service based upon signed to be drawn upwar the what rapidly, to again be'drawn upward arm 202 is resting on factors as contemplated herein will appeal to the subscribers as more equitable, a lesser investment in equipment will suflice to handle the same amount of trafiic were not some pecuniary inducement made to the subsciibers to adjust their calling in accordance with the most desirable regulation of the traflic from the viewpoint of the operating concern.

Referring to Fi 2, S2 is a solenoid interrupter device having a plun er-arm 201 dely periodically and then automatically released after it has engaged all the contacts co-op'erativewith it. The operatin cycle period of the plunger arm 201 is pre erably a out five seconds. The

V and wiii 7 also serve to reduce the peak demands sothat energizing circuit is from'grounded arm 202 A to the winding of the solenoid. Arm 202 and arm 203 are attached by an insulating link 205' so that when the plunger-arm 201 rests upon arm 203, arm engaging contact, and when the plun er-arm 201engages arm 202 on its upward stroke it will disengage arm 202 from its restin contact, deenergizing the solenoid S2 an allowing the plunger-arm 201 to recede by r ravity until it re-engages arm 203 and through the insulating link 205 reattracts the mm 202 against its resting contact to resolenoid to again draw the 201, this cycle oi operation coned and of the energize the plunger-arm tinuing indefinitely. The pivot arm 202 involves mechanical friction so that when the arm 202 is raised from itsresting 202 will rest upon its contact it will not retract until the plungerarm 201 in retracting engages arm 203 and withdraws it. The plunger-arm 201 is also given friction by way of dash-pot action to retard its movement upwardly, so that the plunger-arm will be drawn upwardly at a predetermined slow rate, and released someas before, etc.

its contact. Plungerarm 201 makes electrical engagement with the bar 206 with its strokes, and it also engages contacts 208 and 209-, so it will appear thateach time the plunger-arm 201 is drawn upward the ground on arm 202 will be appli I first to contact 208, then to contact 209, and

that ground will not be applied to the said contacts incidental to the recession of the plunger-arm201. Intermediate contacts in pairs 210-211, 219r-21a214-215, 216 -2 17,

sulated conductive member 225 attached to y Bar 206 is grounded-while ed, im-

. at 218-219, 220-221, are engagedby an inthe plunger-arm'201, so designed that as it is drawn over the said pairs of contacts it will short circuit therespective'pairs success sively, but will not connect contacts of adjacent pairs.

Referring a clock mechanism CK closes a set of contacts 601 to-energize -the drive magnet 602 every t0 a,;'b,' and c of Figs. 2 and 6, I

lliu

" hour so that itspawl603 will drive sprocket- Wheel 60 1 one twenty-fourth of a revolution at each energizationof the drive magnet 602,

' there being twenty-four teeth in the sprocketone revolution every twenty-four-hours. The l cams are designed so that contact set a Wlll .wheel 604. The cams a, b, and c are rigidly connected on a common shaft605 with the sprocket-wheel 604, so that theywill make be closed from 6 a. m. to 10 p. m.; the contact set 6' will be closed from 8a. m. to 8 p the contact set 0' will be closed from 10 a. m. to 12 m., a11d"from 2 p. m. to 5 p. m. Thus, bank contacts 211 and 217 will be grounded between 6 a. m. and 10 p. m.; contacts 213 and 219 will be grounded between 8 a. In." and 8 p. m., and contact 221 will be grounded between 10 a. 1n. and '12 m., and between 2p. n. and 5 p. m. Bank contact'215 ispermanently grounded. In view of'the foregoing,.each time plunger-arm'201 is drawn upwardly between the hours of 10 m. and 11 a. m., for example, one ground impulse is applied to common conductor 226,. four ground impulses to common conductor227,

one ground impulse to common conductor 228, one ground impulse to common conductor 229, and one ground impulse to com-- mon conductor 230. And between 1 a. in. and 2 a. m., for example, one ground impulse is applied to common conductor 226, one ground impulse to common conductor 227, none to common conductor 228, none to common conductor 229, undone ground impulse to common conductor; 230. Itis to be understood thatthe conductors 226 and 230 will each be grounded one time for each u ward stroke of the plunger-arm 201 regard ess of the. time of day, while the conductors 227 228, and 229will not be grounded, or will be grounded, one or more times, depending upon 2 r the hour of day when the saidpIunger-arm is drawn upward.

. 1 Referring to d and coi Figs. and 7,

clock mechanism OIC'sClOSBS a set of contacts 701 toenergize the drive magnet 702 every five seconds, so that its pawl 703 will drive sprocket-wheel 704 one-twelfth of a revolu- 'tion at each energization of its drive ma net 702', there being twelve teeth in the sproc et- L wheel (04. The camsd and e'are rigidly connected on a common shaft 705 with the sproeket-wheel704, so that. they will m'ake, one'revolution every minute.

designed so that contact set (1 will be closed one time each minute, and the contact set 0" will be closed two times each minute.

It will thus appeanin View of-the foregoing, that upon the closure "of contact set (1, relay 231 will actuate and lock to grounded armature 232, preparing a circuit from common conductor 226, armature 233, to the upper winding ofrelay 234. Upon conductor 226 becoming grounded, incidental to the upward movement of the plunger-arm 201, slow-' relay 239 will energize an I V and due .to the slow-releasingcharacteristic p. m., and

The cams are releasing relay 234- will energize, causing its lower winding to be locked by way of 'arma-jf I ture 236, armature 237 :to'its resting grounded f contact,- armature 238' plunger-arm 201 engaging bank. contact 209 d unlock relay 2,34,

ofthe latter relay,

9. ground impulse of brief preparing a circuit vfrom the upper vwindingof slow-releasing relayv 239 to-Conductor 230, so that upon the duration will be appliedftrom armature232, V armature 240 to comr'nonconduet-or 242,.the

object of-which will appear presently. In

the same manner, uponthe closurevofcontact sete', relay 231T will actuate and lock to grounded armature 232, preparing a circuit from conductor'226, armature 233'; to the upper windingof relay234. 1U" on con- .ductor- 226 becoming grounded, inci ental to the u ward movement of theplunge r-arm 201, s ow-releasing relay 284 willenergize, causing its lower winding to'be locked way of armature 236,, armature 237Yto'. its resting grounded contact, armature 238 preparing a circuit from the winding of relay 239' to conductor 230 so. that upon. the plunger-arm 201 engagingbank contact 209, slow-releasing relay 239' will energize and unlock relay 234, and due to the slow-releas ing characteristic of the latter relay, a ground impulse of. brief duration will, be applied from armature 232, armature 240fto com- I mon conductor 243.

.or 243 whi e an impulse is being applied to conductor 227, 228, or 229, though the closure of said contact set d or e. may'occur while the plunger-arm 201. is moving upward, and

is between thesaid contacts 208 and 209. The ob ect of this will. appear presently;

Referring to Fig. 3, the ofl-normal spring set SON is adjusted to operate on theseconde s i g 1 1 00v anjimpulse rannotbe applied to either of conductors 242 vertical oil-normal step of the shaft of first selector G. The ofi' -normalspring set 'FON is adjusted to operate on the first vertical oil'- normalfstep of the said shaft. The oil -nor1nal spring set AFN is adjusted to operate only while the said shaft is raised and is at the first oil-normal position. The first level of bank contacts is attained at the, second vertical'oif-normal step, rather than at the first vertical ofi-norma-l step, as has been common in selectors heretofore. The off-normal spring set FS is' designed to be operated the wipers carried by the shaft aligning with 'from the shaftby the insulated collar 7 upon a predeterminedlevel or levels.

That is if a certain level of trunks is selected the said oflnormal set FS will be operated upon the shaft rotating. The object of the said function will appear, however, it 'has'to do with lines reached through suchlevel upon which no toll charge is to be registered.

traction after bein energized it will cause i the setof wipers o the apparatus unit A to be driven into engagement with the next set ent invention,

toting a main group,

of bank contacts, respectively. Drive magnets op'erating thus have been used in well known typesof lineswitches.

In the system chosen to elucidate the presthree sub-groups of three, first (such as C, E, and F), constiare employed, each said main group being'acce'ssible from a specific group of hneswitches, of perha s one hunselectors each .dred, terminating an equal num r of lines.

So that each lineswitch of a certain group of. subscribers lines has commonaccess to the said main group containing nine selectors. Likewise, other groups of subscribers lines will terminate in corresponding grou s of lineswitches at the central olfice, whic latterli-neswi-tches have access to a second group of three sub-groups of three selectors each, there being two subscribers groups leading to two corresponding lineswitc groups, which two lineswitch groups combined, in turn have access to four selector sub-groups of three selectors each. It will thus appear that the sub-groups of selectors are arranged so that they-lap with respect to the main groups of selectors.- That is to say, the 'first' three suboups ofthe four sub-groups comprise the rst main group of selectors. and the last three subups o the said four sub-groups com t e second main group of selectors.

Un er this arran ement if no selector is available in' the ourthsub-group to subscribers of the second main I, cup of lineswitches, the calling line will a selector of the third or second sub-group of selectors which are lapped from the first main group ofselectors into the second main group f so ectors, so the'second main group. of selectors contains the second, third, and fourth sub-groups of selectors. The selectors of the sub-groups are connected alternatively as to sub-groups in the banks of the lineswitches of thecorresponding main groups of subscribers lines, and the circuits are so designed that a maximum of one ap aratus unit, such as A, can be relateduwith idle selectors of a sub-group. That is to say, if the three selectors of a sub-group are idle, only one of cupying the waiting extended to them can have an apparatus unit associated with it. However, another 1 apparatus unit becomes newly associated with. one of the other selectors of the latter said sub-group if the requirement there of the prior associated apparatus unit has not terminatedin a connection being established or if the connec tion has been established and the apparatus unit has not yet been automatically ejected from connection 'with it. as will appear presently. Under this condition, if an apparatus unit is respectivelyassociated with one selector of each of the three sub-groups of a main group of selectors, and there is another apparatus unit newly associated with one of the selectors of one of the subroups, making two apparatus units for the sudi-group, of the latter said main group, in a call which has not been responded to and the initial charge therefor registered, after the said charge is registered and the apparatus unit ejected, as

will appear presently, the apparatus unit will not be able to seize a selector of the three subgroups it is co-operative with, it will rotate selectively oi! the respective apparatus bank contact sets thereof and stop upon the set of bank contacts of the waiting position provided, there'bein ten rotary positions in all. Then, if one of t e selectors including its cooperating apparatus unit is seized by a lineswitch 0 a calling line, tive impulse being ap lie to the said seized selector causing it to 1 moved from its first vertical off-normal position, as will appear presently, the apparatus unit (or units) ocsition will forthwith start automatically unctioning selectively,

whereupon the next available selector of the concerned sub-group will be seized. Of course the latter said selector seized may have been seized by some other hunting apparatus unit (or units which had been ejected practically coinci entally, and in that event the apparatus unit (or units) whichstarted hunting from the waiting position will continue and return tothe wait ngiposition.

presentl it will be clear that one apparatus unit wil be required foreach sub-group of selectors, so there will always be three selectors seizable in a main group (the otherselectors being barred, as will appear presently), and to this, additional apparatus units as willbe required to supply apparatus units for the selectors on connections being estab lished and which have not ejected the concerned apparatus unit therefrom.

While the sub-groups in the exampled sysu on the first direc-' From the foregoing, and as will appear tem comprise three selectors, it will be under- .stood that the number may be varied, and in fact, single grou 5 may be em loyedhaving any desired num er. In the latter. case, an auxiliary sub-group, common to a plurality of main groups may be employed to receive an initiated call in theevent there is no seiz- I able selector in the main group-.. This would be virtually a main group consistingof two to a main group of nine first selectors, three sub-groups of three selectors each,

there is one reserve position from which no sub-groups; however, one said subgroup being a common sub-group with other main groups of selectors. s v In a commercial installation thelineswitches may have access to twenty-five first selectors, consisting of two sub-groups of tenselectors each, which sub-groups may be also lapped into other main groups, and in addi-.

tion, a sub-group of five selectors common to a plurality of main groups may be employed to take care of emergency conditions of heavy coincident traffic. In fact, the-latter sub-group of five selectors may possibly be complete permanent-unit selectors of wellknown form.

Under the last above method of employing the present invention, one apparatus unit would be required for each sub-group of ten, and two emergency apparatus units, which will either be in an operating relation .to a first selector, or on the waiting position provided. To this will be added the permanent-unit type selectors related to the said sub-group of five,

the apparatus units for the said latter subgroup, if selectors of the'present invention and apparatus units associated therewith are employed. Thus, but a percentage of the number, of selectors employedwill be represented by apparatus units. r

It will appear that in the illustration the wipers of the apparatus units have accem selectors can bereached. Also, in viewof the fact that there is a second main selectors similar to the first said mam group,

of which two of the sub-groups are comprisedy in the first said main group, there will be a sub-group of three selectors individual to each main cup. That is,the first sub-group will be individual to the first main group, and

the fourth sub-group" will be individual to I the second main group.

' Referring to the telephones T5, T3, and the A? selector C, (also selectors E and F, shown in you part), when combined with apparatus unit A, they'belong to the class of A and E, respectively, of tin U. S. patent to Newforth, No. 13,901, reissued, April 13, 1915; however, the latter is modified to operate in accordance with the present invention. The lineswitch 1), belongs to the class of the lineswitrh shown in U. S. patent to Lamb, No. 1,193,160, granted August 1, 1916; however, modified to operate in accordance with the present invention. The meterdevices NCM and TM arewell known electro-magnet counting devices with index drums corresponding to a plurality of numerical orders. The wipers and co-operating bank contacts of the apparatus unit are in general similar to the designused in lineswitch D. The connector CON in bein roup of Fig. 3 is like connector H in the said cited patent to Newforth, having particular reference to the function of the back-bridge relay 18 of said connector H wherein it reverses the relationship of the leading-in talkingqconductors with respect to the battery and the ground windings of the front bridge or. line re1ay16.

The general mechanical fOl'IIl: andarrangement of the elements of thezautomatic'teleq Iphone apparatus of. the present-invention aving been set forth, the specific operation of the exampled system'will now be described underassumed operative conditions. u I Upon the initiation of a call from T5 by removing the receiver from the switchhook thereat, a circuit can be tracedfrom the windingof line relay 501, armature-5.02, line conductor, 503, telephone T5, line conductor 504, armature 506 to grounded resting contact, relay 501 actuating. Assuming that first selector C is seizable by having an apparatus unit associated with it, as drawn, andthat,

therefore, the shaft of said O has been stepped off-normal and the off-normal contacts are. in a conditionshown in thedrawing because of its being seizable, as will appear presently, no ground will exist on either of bank contacts 510 or 511, and that, therefore, ground will not be communicated to conductor 512 .by either. wiper 513 0r 514. Armature 515 being normal, the motor magnet M5 willnot beop- 502, wiper 525, bank contact 526," conductor 527, shunted series winding of electropolarized' relay 301, armature 30 2, conductor 303, bank contact 101, wiper 102 to the upper winding of line relay 103 and from the lower winding of the latter relay, wiper 104, bank contact 105, conductor 106, armature 304, conductor 305, bank contact 529, wiper 530, arma ture 506, andthrough the telephone T5 to contelephone ductor 503, relay 103 energizing. A circuit cannow be traced from grounded armature 108, winding of slow-releasing relay 109, the

latter relay actuating, a circuit can nowbe traced from grounded working contact 110,

its co-operating armature, conductor 112,

armature 113, wiper 114, bank contact 115, conductor 116, resistance 307 to the inside winding of relay 301'. The current traversing the two said windings of relay 301 magnetize edifierentially and,therefore, its armatures are not operativel attractedat this time, but, as

will appear, t e current now traversing theouter winding will be changed in direction consequent to a response'being attained from the called line, and under that condition, the

' tively attracted, the resistance 307 being then armatures on relay 301 will become operashort-oircuited by armature 308. .The latter will increase the current derived through the inner winding of relay 301 to a value which ing, will not retract until ground is removed from conductor 116. At this time a circuit can be traced from grounded contact 118, its co-operating armature,'wiper 119, bank contact 120, conductor 121, conductor532, banki contact 510,wiper 513, conductor 512, Jrmature 533 to the lower winding terminal of re lay 517, before arn1a.ture"523 has retracted, so that no lapse of ound potential will occur to the-lower winding terminal of relay 517 the lineswitch D remaining seized.

Ilpon the party at telephone T5 manipulating the'callmgdevice thereat in accordance with the first digit of the called number which. number is 1111), relay 103 will eactuate and reactuate one time responsive thereto, whereupon a circuit can be traced from grounded contact 110, upper armature of relay 103, sustained armature 122, winding of slow-releasing relay 123, wiper 124, bank contact 125, conductor 126 to vertical magnet V3, .the vertical magnet operating to set the wipers 312 to 317 (inclusive) into alignment with the first level of bank contacts, reached by two vertical ste s, one of which was iniparted automatical by the apparatus unit at the time it seized the selector C, as will ap- I pear presently. Upon the attraction of armature 127 at the time the vertical magnet V3 is thus energized from contact 110, a circuit was closed from the winding of shunted relay 128, armature 127, to grounded contact 118, the relay 128 actuating and locking by way of wiper 129, bank contact 130, conductor 131, off-normal spring 318, armature 319 of the rotary magnet R3, conductor 320 bank contact 132, wi er 133 to grounded armature 134. Upon t e retraction of armature 127 followin the said impulse tothe vertical in et 3, a circuit can be traced from groun ed contact 118, its co-operating armature, armature 127, armature 135, wiper 136, bank contact 137, conductor 13.8 to the winding of the rotary magnet R3, the rotary magnet operating to drive the wipers 312 to 317 into engagement with bank contacts 325 to 330, respectively. If either of bank contacts 325 or 326 constitutes ground potential, because of second selector SS bein either busy or its shaft is ofi normal, as will appear presently, ground will be communicated to armature 332, conductor 320, armature 319, off-normal spring 318, conductor 131, bank contact 130, wi er 129 to the winding of relay 128, the re ay 128 reactuating and establishing a locln'ng circuit from its 136, bank contact 137, conductor 138, to the winding of the rotary magnet R3, the rotary magnet operating to drive the shaft carrying wipers 312 to 317 an additional rotary step into engagement with the second set of bank contacts, the locking circuit traced for the re1ay 128 being opened as before at armature 319." Upon the retraction of" armature 319, provided either. wiper 312 or 313' receives ground from an engaged bank contact, relay 128 will be caused to be again actuated and locked,.as described, this cycle of operations of relay 128 and the rotary magnet R3 continuing as long as either wiper 312 or 313 receives ground trom an engaged bank contact.

Assumin that neither wiper 312 nor 313 encountered ground when they engaged bank contacts 325and 326, respectively, therefore, when the armature 319 retracted, following the first actuation of the rotary magnet R3,

no energizing circuit was established for relay 128. In this connection it will be noted that ground from contact 118;its co-operating armature, wiper 119, bank contact 120, conductor 121, conductor 532, is maintained on the lower terminal of the winding of seizing relay'335, and as long as armature 134 is attracted or wiper 312 or wiper 313 receivcs ground from an engaged bank contact, bearing in mind the retracted condition of armature 332, ground will also exist on the upper terminal of the winding of relay 335; Thai: is to say, the rela 335 is thus short circuited. However, upon t e relay 128 deactuating, incidental to the armature 319 on the rotary magnet R3 attracting, the grounded armature134 retracts and opens the path traced from it to the upper terminal of the winding of relay 335, so if ground isnot received through wiper 312 or wiper 313, there will not be ground potential on the upper terminal of the winding of relay 335. Bearing in mind the retracted condition of the armature 319 of the rotary magnet, a circuit can be traced from the winding of relay 128, wiper 129, bank contact 130, conductor 131, off-normal spring 318, armature 319,-conductor 320, winding of relay 335, conductor 532, conductor 121, bank contact 120, wiper 119 to grounded working contact 118. Relay 128 is marginally adjusted so that it will not operatively energize included in a circuit path with the winding of relay 335, but the relay 335 will operatively energizeunder that condition. Therefore, relay 335 operates by way of effecting the seizure of first selector C.

circuit can now be traced from the bat- 1 under all off-normal conditions tery winding of the line relay of the second selector SS, conductor 336, bank contact 327, wiper 314, armature 302, shunted series winding of relay 301, 526, wiper 525, over the traced path including the telephone T5 to wiper 530, bank contact 529, conductor 305, armature 304, wiper 315, bank contact 328, conductor 338 to the ground winding of the line relay of second selector SS, the said line relay actuating and causesits release relay to actuate and apply ground to private conductor 339, in the well known manner, in view of the said cited patent to N ewforth. However, in this connection it isto be understood that an addition has been made to the circuits of selector E, of the said cited patent to N ewforth, by way of introducing a set of off-normal springs ON 3, andwhich will close and apply ground to auxiliary private conductor 340 upon the first off-normal movement of the shaft thereof, this ground being communicated to bank contact 325, (and its multiples), so that'bank contact 325 will constitute ground potential of the second selector SS, the object of which will appear presently.

At the time relay 335 actuated, its armatures 302 and 304 disassociated the windings of relay 103 of the apparatus unit so that relay 109 is caused to deactuate consistent with its slow-releasing characteristic thereafter. Contact 118 thus ceases to apply ground to its co-operative armature. However, no lapse of ground occurs to conductor 121 therefrom, due to the fact, that ground is applied to conductor 339 from the second selector SS beforerelay 109 deactuates, and thus no lapse of ground potential occurs to wiper 513, so that the lineswitch D is maintained seized.

At the time relay 335 actuates, its armature 342 closes a circuit from grounded bank contact 330, Wiper 317, said armature 342, conductor 343, bank contact 140, wiper 141, armature 142 to the winding of relay 143, the latter relay fully operating. In this connec tion, it is to be understood, relay 143 is marginally adjusted so that it will attract both of its armatures 144 and 145 upon absolute ground being applied to its winding terminal, but that should ground he applied through a resistance havinga value equivalent to that of resistance 343, for example, it will be only partially operative, wherein armature 144 5 will be attracted into engagement with its working contact but that armature 145 will not engage its working contact. The object of relay 143 will appear presently. I

Upon the calling party at telephone T5 sending the second digit 1, the second selector SS will operate in the well known manner. and its wipers 345 to 347 will seize bank contacts 348 to 350. extending the connection,.

over conductors 351 to 353, respectively, to the connector CON, the line relay in'the conconduct-or 527, bankcontact corresponding to telephone signal and the series windin pleted from armature 340,

:conductor 250, conductor right hand springs of set nector and the release relay therein operating in the well known manner, to apply round to conductor 351 to maintain the rst selector C and thelineswitch D seized before the release relay in second selector SS retracts and removes the ground applied to conductor 339, however, the conductor 339 ground from the connector now receives CON, there having been no lapse of ground thereto. v

Upon the said calling party sendingfthe last two digits 1 1, the connector CON will be caused to operate, setting its wipers 355 to 357np0n bank contacts 358 to 360, T3, and cause the bell 361 thereat to be vibrated, in the well known manner, in view of the said cited patent to N ewforth. Upon the called party at telephone T3 responding by removing the receiver from the switch-hook thereat, the connector (VON will cause the terminals of the front-bridge line relay thereof to be reciprocated with respect to conductors 352 and 353 (in view of the cited patent to N ewforth), so that in lieu of the battery winding of the line relay being connected to conductor 352 as norm-ally, it is now connected to conductor 353, and the ground winding is correspondingly transferred from conductor 353to conductor 352, so the current now traversing the traced circuit includin the telephone T5 01' relay 301 is reversed to that primarily esta lished and maintained up until the said called party I respondedg'g Thus, the polarizing and series windings 031-;

rela j 301 now ener izin ithe core cumulatively, its armatures will operative-1y attract. That is to say, the relay 301 becomes operatively energized upon the response of the called party". And since the energizing circuit for the winding of relay 335 is now com the latter said winding, its attracted armature 332, wiper 313 to grounded bank contact 326, the first selector C is also maintained seized. In this connection it will be stated that battery is shown permanently applied to armature 341 through a resistance. This resistance is of a value approximating the value of the winding (as shunted) on relay 128. The relay 335 is maintained energized from parallel sources through armature 341 and the winding of relay 128 until the latter is disassociated, as will appear, after which relay 335 is is continually reciprocating its plunger-arm,

upon'the plunger-arm 201 engaging contact 208 the first time after the relay 301 has been caused to operatively energize, a circuit can be traced from grounded arm 202, bar 206, plunger-arm 201, contact 208, conductor 226, 362, armature 363, 'FS, conductor 364,

' spring sets a, b, and

conductor 154, wiper bank contact 146, wiper 147, make-before; break spring 149, armature 150 to the winding of slow-releasing relay 151, the latter relay operating and locking to its grounded armature 153 and disconnecting the spring 149 from its resting contact, thereby opening the traced circuit from arm 202.

It will be assumed that .the stated call is transpiring at 2: 30, p. m., and, therefore, 0, are closed, and that, therefore, contacts 211, 213, 215, 217, 219, and 221 constitute ground potential received through the said s ring sets in the manner as hereinbefore set orth. Upon the plungera-rm 201 drawing upwardly, and as its insulated conductive member 225 short-circuits the pairs of contacts successively, ground will be first applied from contact 221, contact 220,

conductor 227., conductor 251, conductor 252,

armature of relay 151, 155, bank contact 156, bank contact 540, wiper 541 to armature 152, upper conductor 157,

the winding of the total meter TM, causing it to operate to advance its register-wheel one unit. Upon the member 225 successively short-circuiting bank contacts 219-218, 217-216, and 215-214, tional ground impulses, making a total of four ground impulses, to conductor 227, and over the traced path to the winding of said total meter TM, the total meter, therefore, advancing its register-wheel a total of four unit spaces, thus far in the assumed call. 'When the member 225 short- circuits contacts 213 and 212, a ground impulse is applied to conductor 228, conductor 253, conductor 254, armature 144, armature 152, upper armature of'relay 151, and over the traced path to the winding of the total meter TM, thus advancductor 256, armature 145,

ing its register-wheel an additionalunitspace, and. upon the member 225 short- circuiting contacts 211 and 210, a ground impulse "is applied to conductor 229, conductor 255, conarmature 152, upper armature of relay 151, and over-the traced path to the winding of the total meter TM, thus advancing its register-wheel-an additional unit space, the total meter, therefore, having advanced its register-wheel a total of six'unit spaces In this connection it will be noted that the energization ofthe magnets of the meter TM 7 another (and also meter NCM) will depend upon the armature 545 of the lineswitch D being at-' tracted..- '1 hat is, if the lineswit'ch D is not in a seized state the said meters cannot be operated. This isto prevent the false operathe lineswit'ch D is resting idly upon the bank contact set corresponding to .a selector which is seized by lineswitch, wherebi impulses operating the meters of the seize lineswitch would also operate the meters associated with assumed idle lineswitch D.

Upon the plunger-arm attracting so it apit will apply addi thus far in the assumed call. 7

plies the ground received from arm 202 to contact 209, this ground can be traced over conductor 230, conductor 258, armature 158, make-before-break spring 159 to the winding of relay 160. The relay 160 will actuate, whereby a'locking circuit can be traced from its winding, spring 159, armature 161, armature 158 to the said grounded contact 209, the said locking circuit the plunger-arm is caused to retract due to the mecianical operation whereby arm 202 is caused to open the energizing circuit of the solenoid winding. It will be noted that as the plunger-arm retracts ground on the bar 206. 5

At the time relay 160 attracted it unlocked relay 151 at armature 150, and although spring 149 retracts, the relay 151 will not be reenergized due to the fact that coniluctor 226 is not grounded at this time. Re-

3' tion of armature 142. Also, actuation of relay 160, and before relay 151 deactuates, bearing in mind the ing characteristicof the latter relay, a circuit can be traced from grounded armature 162, armature 163, armature 164, conductor 165, armature 166 on the motor magnet M to the winding thereof, the motor magnet actuating to drive the wipers of the A into engagement with the next set of bank contacts, respectively, uponthe deactuation there will be no 3 slow-releasapparatus unit enduring only until 143 will also deactuate due to the attracincidental to the ot' the saidmotor magnet upon its armature l the connection between the ca thereto will then constitute ground potential, the object of which will appear presently; It will also be noted that due to the attraction of armature 366, a circuit can be traced therefrom through armature 367, conductor 368, bank contact 173, wiper 174 to working contact 175, that is to say, if a selector corresponding to C is in-a seized state and a telephonic connection is complete between the calling and called parties, conductor 368 and its multipled attached bank contacts,

ling and called parties, the operation of the apparatus unit llu.

ere ore, having no operappearing in corresponding relation to the accessible apparatus units, ,1 will. constitute. groundpotentiali So if: the apparatus unit.

A is hunting. and the relay168 isthereforc actuated when the wiper 174 receives ground- 'from an engaged bank contact corresponding to a selector in aresponded-to connection,

the'ground received therefrom will be coms.

municated through armature 177,- conductor 165, armature 166 to the windingof motorv magnet M causing it to actuate and advance the wipers from the set of bank contacts cora responding to the latter of said selector, upon the motor magnet M deactuating consequentv to its armature 166 interrupting its energizing circuit, whereupon the apparatus unit will be in-testing. relation totthe successive set of bank contacts. It will alsoappear that if wiper176 (which-also is shown in F ig. 4,]

the functions of which will be discussedpresently) engages a grounded bank contact while relay 168 is actuated, the apparatus unit thus being in a hunting state, a circuit can be traced from saidgrounded wiper, armature 164, conductor 165, armature 166 to I the winding of the motor magnetM, the

ceives ground from an engaged bank contact, 4

this ground will be communicated through armature 166 to the winding of motor magnet M, causing the wipers to be advanced from the'set of bank contacts then engaged to the successive set. And it.will also appear that if wi r 170, receives ound from an engaged ban contact while t e apparatus unit A is hunting, and, therefore, relay 168 is actuated, this ground will be communicated through armature 169, working contact 175, armature 177, conductor 165, armature 166 to the winding of motor magnet M, the motor magnet operating to advance the wipers to t e successiveset of bank contacts.

Recapitulating, the apparatus unit 'A will advance its wipers to a successive set of bank "contact set corresponding to the resting pofrom an engaged "ban Wlll receive ground whenever it engages a sition but. also if said wiper rests on any grounded-bank contact; when its relay 160 actuates and uiilocks relay 151; when the said unit is hunting and wiper 176 receives ground. from an engaged bank contact; when the said unit is hunting and wi er 17 4 receives ground contact. Wiper 170 bank contact set wherein an apparatus unit is already resting upon a corresponding set, that is to say, if an apparatus unit in hunting finds an unguarded bank contact set, and,

therefore, does not rotate from it, a hunting apparatusunit subsequently testinga corresponding (multipled) set of bankcontacts will not be enabled to stop upon them, but will rotate-offto the successive set, at; The impulse received through armatures 162 and 163 will only occur when the plunger-arm 201 advances to the end of its stroke and engagesbank contact 209, meaning that all of;

the meter effecting impulsesinvolved in the initial-charge. have been sent andthatgtheref fore, the apparatus unit. is notfurther' nag,

quiredin relation to the selector C.

In this connection. it will'be' noted that'iat' the time relay 151 actuated, its, grounded are.

inature 1 62' applied 163, wiper 179, ban contact 180, conductor 181, bank contact 548, wiper5/l9 to the winding of the magnet of [the number-o f-callsf meter NCM causing it to register one time,

oundthrough' armature the object being to have a recordof the total number of completed connections, and in ad-f dition thereto, to have a record of the total charges involved therein, which latter,'j0f

course, Wlll depend upon the time of day the i call is made, theduration thereof, and

destination. I Since the presentinvention contemplates a duration charge, or charges, it involves opcrating the meter TM at predetermined periods, which in theassumed call will be one unit registration each half minute. It has been described how the'relay 231- is actuated and locked each half minute, preparatoryto transmittingits registering im ulse after the initial charge im ulses have novel provision ing made to avoid the en sent,"the

possibility of coincident impulses being applied to the meter TM. To this end, there lay 231' remains locked until conductor 230 becomes grounded when the plunger-arm ad vances to contact 209 at the end of its upward stroke, and that relay 234" becomes locked when the plunger-arm 201 engages bank contact 208 at the beginning of its upward stroke and grounds conductor 226, the

relay 234' becoming unlocked when the plunger-arm engages contact 209 incidental to relay 239' actuating, followed bythedeactuation of relay 231. An im ulse-isimparted to conductor 243 through e'hereinbefore described functioning of armatures 232' and 240' at the time relay 239' actuates and before relay 234' has permitted its armatureQ232 to retract due to its slow-releasing characteristic. Bearing in mind that the apparatus unit A is at this time disassociating or has already disassociated from the selector C, a circuit can be traced from conductor 243, conductor 369, bank contact 329, wiper 316, armature 370, conductor 37.1, bank contact 540, wiper 541 to the winding'of the magnet of the meter TM, the said meter advancing a unit step. It will be manifest that due to r-arm 201 operating more fre quently t an'the contact set 0' closes, it is most probable that the relay 231' will not have been locked at the time the apparatus unit A disassociated from the selector C, therefore, the impulse applied immediately after its disassociation will not occur as de, scribed under the particular condition. However, at s ucli'time as contact set e closes subsequently, the relay 231' will actuate and lock, followed by relay 234' actuating and locking when the conductor 226 is grounded, and then appl ing the ground impulse over the traced pat to the magnet of the meter TM.. In viewof relay 231' unlocking incidental to relay 239' actuatin the relay 231' is in readiness to be again ocked when contact set e again closes at the next half minute period, after which relay 234' will be caused to actuate and lock the first time conductor 226 becomes grounded thereafter, followed by the actuation of relay 239' when the the plan a conductor 230 becomes grounded, following.

The duration timi devices d and e are commonly related to t e first selector banks of the exchange oflice, while the initial charging devices a, b and c are commonly related to the first selectors of the exch oflice.

Attention is directed to the ction of the oil-normal spring set FS under the condi-- i tion of calling a level wherein it will be caused to operate upon the wipers rotatingin. That is, say the third level constitutes a trunk group leading to specialintermediate selectors having access to connectors or terminating equipments of lines which may be called without char The details of the I said special intermediate selectors and equipments associated therewith will be discussed presentl Upon the ofi-normal spring set FS operating, wiper 178 will become grounded by way of its en ged bank contact 183, con- ,ductor 184, 1c spring of said set FS, up r armature of relay 335 to wiper 313. e wiper 313 will be grounded when the relay 335 actuates to comfplete the traced path, receiving its and cm the succeedin selector seized, in the manner as hereinbe ore described. Under this condition the motor m et M will be energized and the wipers of t 0 ap aratus unit A will be caused to advance an hunt. The said ground will be applied thloltih the middle spring of the said set F8 to e inner winding of relay 301,

causing the latter relay to actuate, since the;

digit 3, the said rela 301 will be then acinner winding of relay 301 will operatively attract the armature thereof when applied to direct ground. Thesaid inner win in is now locked to grounded spring 379. e.

wipers 316 and 317 are now free, since the co-operating bank contacts at the level concerned are unconnected. In this connection,

it will be manifest that since the res tively cooperating bank contacts of all positions of the wiring of the lower two pairs of the entire level is concerned, wherein wipers- 316 and 317 co-operate with live bank contacts, it will be e uivalent to substitute off-- for which no charge is to be made, the apparatus unit is ejected or caused to hunt forthwith, incidental to the selector seizing, and not delay until after an initial registration is made. Also, that due to the right hand contacts of the off-normal set being open, the traced path from conductor 250 to spring 149 is opened, thus precluding an operation of the meter 1 While the third level of the first selector C refers to free lines to which a switching char e is not made, and that the said level may ave trunks leading to second selectors similar to SS, and the latter to in turn have access to connectors similar to CON, or. to connectors which do not cause the direction of current to be reversed back toward the v calling party, this arrangement may be varied. In fact the varied arrangement shown in Fig. 9 may be the preferred arrangement under most operative conditions.

Fig. 9 shows a portion of first selector C as shown in Fig. 3, although parts, incluldin contacts en aged by wipers 316 and 317, are left off. owever, the second selector SS is shown connected as in Fig. 3, although there is an alternative path to said selector SS'by way of the special intermediate selector J and apparatus element K. Under the latter condition, when the selector C seizes the first set of bank contacts of the third level thereof, the connection is extended to selector J, which latter selector is similar to selector SS. The sets of bank contacts of the bank levels of selector J are in corres onding multiple relation with those accessi 1e to selector C. Thus, if the digit 3 is prefixed to any number called through the selector C the selector J will be introduced and the same telephone line reached as if it were not prefixed. However, it has been described how the relay 301 is caused to actuate and lock incidental to the wipers of selector C rotating-in on the third level, so under the condition of the selector J being attained upon sending the first tuated and locked. he next digit called will be 1, which will cause selector SS to be seized by selector J, after which the last three digits 1--1-1 will be sent to o erate the selector SS and the connector C N to cause the latter to set its wipers 355 to 357 on bank contacts 358 to 360, respectively, and signal telephone T3, it being assumed that the right hand portion of Fig. 3 defined by the section line m-n'will be applied to the i right of the similarly designated section line in Fig. 9.

It willbe assumed that the telephone T3 is not a telephone to which a call may be made without charge, and in fact the connector CON will determinethis by reason of its function of reversing the current supplied to the calling line incidental to the called telephone being responded to. After the wipers 312 to 317' engage bank contacts 384 to 389, respectively, and the second digit 1 has been sent, the paths from wipers313 to 315,

- been .1 in lieu of 3. However,

\ However,

have been continued to conductors 339, 336, and 338, respectively, as if the first digit had it will appear that the path from wiper 315 is by way of the series winding of shunted electropolarized relay 908 of equipment element K. Bank contact 905 becoming grounded upon being engaged by wiper 906, (the companion wipers engaging the corresponding companion bank contacts), the inner electro-polarizing winding of relay 908 will become energized. Due to the fact that the conductor 338 is the one connected to the ground winding of the line relay winding of the selector S the two windings of relay 908 will energize differentially, and under that condition will not operat-ively attract its armature 909. upon the connector CON causing the current to be reversed in direction, incidental to the party at telephone T3 responding, the armature 909 will attract and 0 en A. Anderson,

the line switch D will unseize and the selec tors O and J will restore, followed by connector CON and selector SS.

Assuming that the connector CON has its reversing armatures blocked so they are inoperative, or that a well known form of connector which does not reverse the current projected back over the calling line is used, or that a connector ofthe type of connector F in U. S. Patent No.- 1,269,245, granted to June 11, 1918, is emplo ed, and that the linel'eading' to telephone 3 is connected through the tenth or O level in lieu of the 1 level, it will appear that the current traversing the series windin of relay 908 will not energize cumulative y with the inner winding thereof, upon a response being attained at telephone T3.' Under the latter condition the armature 909 will not be operatively attracted, and, therefore, the connection Wlll not be destroyed, as last before described. I

In view of the last foregoing paragraph it will thus appear that if "the selector J is introduced by prefixing the digit 3 and the call is completed to a telephone to which a charge is made, the connection will be destroyed incidental to the called telephone being responded to. Also, if the said call is to a telephone to which no charge is to be made, the connection will not be destroyed, it being understood that where no charge 18 to be made the connector or. selector reaching the line called does not cause the current projected toward the calling line to be reversed in direc tion incidental to obtaining a' response on the called line. ,Fig. '9 thus provides for free calls over the general trunking system.' While the third level has been described as the free level, in practice, this may be any level, possibly the first level. Subscribers will" know by the digit or'letter designation indicative thereof if'the line to be called is a free line.

Selector O as shown in the drawing, Fig. 3, has its shaft one step off-normal, therefore,

The arrangement disclosed in.

the contacts of set FON are open. Were the 7 said selector idle, associated therewith, the said off-normal set FON would have its sprin s, closed, and, therefore, its springs 372 wou d be grounded, and this ground would be communicated to conductor 532, bank contact 510 and its multiples, thus guarding the selector against seizure by a lineswitch. This groundon conductor 532 is communicated over conductor 121 to bank contact 120, thelatter to no operative purpose'at this juncture. Off-normal set AFN will have its springs normal, that is, .the left hand pair of springs will be engaged and the right'hand pair will be disengaged. Bearing in mind that E and F represent-the shafts of selectors belonging to the sub-group of three containing the selector C, and assuming that they are unrelated to. an apparatus unit, and are not in a connection but are at normal, a circuit can be traced from grounded spring 401, spring 402, spring 403, spring 404, conductor 405, spring 373, spring 374, conductor 375, off-normal spring 376, conductor 377, conductor 407 to the winding of relay 408, the latter relay actuating. A path can also be traced from conductor 375 through the lower spring pairs of SON, SON, and SON to conductor-407. In view of the last traced circuits it will appear that whenever without an apparatus switch off-normal sets AFN, AFN, and AFN" are I unoperated, which will mean that the shafts of the selectors O, E, and F are either at normal or above the first off normal osition, and

that any one of the ofi-norma sets SON, SON, and SON are unoperated, which will mean that the shafts of the selectors O, E, and F, or any one of them have not stepped above the first off-normal position, the relay 408 tors apply ground to coluluctors 411 and 412, respectively, and grounded armature 413 will apply ground to conductor 414, and to bank contact 415 occupying the resting position, there being no selectors corresponding to the resting position. For convenience, the said resting position will be referred to as resting position ten, since it is assumed that there are ten sets of bank contacts in the cycle, nine of which correspond to the three sub-' roups of three selectors, referred to herein eforc. Grounded armature 417 is applied to the free terminal of lamp 418, causing it to glow to, indicate the condition, which is, that the group of selectors C, E, and F has no a paratus unit associated with any one 0 them and is also seizable to an apparatus unit, it bein borne in mind, that an apparatus unit may e associated with one of the said selecofi-normal position, perhaps by way of completing a connection which has not yet been answered and the initial charge registered therefor.

It will be remembered that under the laststated condition, no selector of the said subgroup is seizable by a lineswitch, due to the fact that it is guarded as set forth, if its shaft is at normal, or if it is seized by a lineswitch. It will be manifest that bank contacts 420, 421, 422, 423, 424, and 425 constitute ground potential, as well as the corresponding multipled bank contacts engageable to the apparatus unit A by its wipers 17 8 and 176, as indicated, the said wipers being in .a position shown in Fig. 1, wiper 178 being also shown in the same position in Fig. 10. The bank contacts designated H are engageable to one of the companion apparatus units to said A which have common access with said A to the second and third sub-groups of selectors and to the fourth sub-group of selectors, so that it has common access with said A to the second and third sub-group of selectors only. It is to be borne in mind that there would. be a lurality of apparatus units in access to eac of a plurality of main groups constituted of s milar sub-groups.

It is to be understood that me selector. C will occupy position one, selector E position four, and selector F position seven, the wipers of apparatus unit A being shown as resting upon the set of bank contacts occupying position one. Thus a sub-group of three selectors will also occupy positions two, five, and eight. And a sub-grou of three selectors will also occupy positions t ree, six, and nine. The selectors constituting the sub-groups not shown, but referred to, are to be assumed similar to the sub-group occupying position one consisted of selectors C, E, and F.

In view of conductors 411 and 412 being grounded, and also 1n view of the statement 17 6, wherein if it recontact, a hunting with reference to wiper ceives ground from a bank and the shaft thereof be above the firstthe sub-group occupyin apparatus unit will not be enabled to stop thereon,'it will appear that the only subgroup of selectors that is not barred against seizure by a hunting apparatus unit is the sub-group occupying positions one, four, and seven that is seizable to a lineswitch, and it also evidences that there must be a selector in this group nominally seizable because of its shaft being at normal, as otherwise the relay 408 could not actuate, due to the fact that the lower pair. of sprin s of sets SO SON, and SON" would then be operated. Under this condition, (relay 408 being actuated), a hunting apparatus unit is constrained to seize one of the selectors of the bank positions one, four, or seven, an which are the only selectors of the main group with which apparatus unit Aeo-operates which are not falsely guarded through the agency of relay 408.

Assuming that the apparatus unit A (although it may be any other apparatus unit or units companion to A) is occupying the resting position, and that its wiper 17 8 is,

therefore, resting upon bank contact 415, it

will be manifest that since conductor 414 was grounded through the agency of relay 408 coincident with the said relay placing a false guarding condition on the selectors of the said two sub-groups, and in view of the statement wherein if wiper 17 8 receives ground the motor magnet M will be-caused to advance the wipers and hunt, it is clear that the apparatus unit A will forthwith start its hunting operation seeking one of the three selectors of the sub-group containing C, E, and F, and it will stop with its wiper resting upon a bank contact set corresponding to the selector of the said sub-group which does not present a barred condition to the apparatus unit A.

In this connection, the selector C is the one that is seizable, and that, therefore itshaft was at normal, and under which condition it will be remembere the pairs of springs constituting the offnormal set FON will be engaged, Then, upon the apparatus unit A stop ing upon the, set of bank contacts correspon ing to the selector G, a circuitcan be traced from the winding of the vertical magnet V3, conductor 172, bank contact 171, wiper 170, armature 169 to its resting grounded contact, the vertical magnet operating to step the shaft up one vertical position, incidentally opening the pairs of springs of the off-normal set FON, and operating off-normal set SON not bein operatively affected. Ground having thus been removed from spring 372 and bank contact 510 and its I bank positions one, four, and seven; all the selectors of the other two sub-groupsbeing barred by reason of relay 408 being actuated because there is no selector in the group occupying the said bank each of all of the off-normal the off-normal set AFN, the

it will be assumed that i multiples, the said selector C is now subject Relays 430, 431, and 432 correspond in nu-' merical order to relay 408 with relation to the other three sub-groups of selectors (not shown) and will be caused to actuate under the same conditions as caused relay 408 to actuate, in the foregoing description. How'- ever, in view of the fact that the second and third sub-groups are common to both main groups, it will appear that if relay 430 is.

actuated there is a sub-group of both main groups that r uires an apparatus unit, and under that con ition, armatures 435 and 436 will apply ground toponductors 414 and 437. Under that condition, should there be an apparatus unit (or units) with its wiper corresponding to 178 resting upon bank contact 415' of the first main group, and an apparatus unit (or units) with itswiper corresponding to 178 resting upon bank contact 440 of the second main group, the said apparatus units will be caused to forthwith advance to the successive set of bank contacts in hunting operation, seeking an idle selector in the second sub-group occupying bank positions two, five, and eight of the first main group, and positions one, four, and seven of the second main group. It is manifest that since grounded armature's 442, 443, and-444 are attracted, conductors 445, 446, and 411 are grounded and that, therefore, the selectors of the fourth, first, and third sub-groups are barred a ainst seizure by a hunting apparatus unit; t iis applyingto both main groups .of selectors, where a sub-group appears in both said main groups. In the exampled case, the third sub-group of selectors appears .in both said main groups of selectors.

It will, be manifest that the second sub-group k of selectors, which is accessible to the apparatus units of both main groups, is the only sub-group of selectors unguarded falsely, and latter said sub-group is also the one requiring an apparatus unit, as evidenced by the actuation of relay 430. It will appear that ground is now applied from armature 435 to bank contact 415, which will cause a resting apparatus unit of the first main group of selectors to rotate-off and hunt from the corresponding resting bank contact set, should its wipercorresponding to 178 be resting on said contact 415. It will also appear that ground is now applied from; armature 436 to bank contact 440 of the second main group, which will cause a resting apparatus unit of the, second main group. to rotate-0E constrain any other hunting apparatus, unit which may have become disassociated from a selector ofrany sub-group to find a selector of the second sub-group, because it is not able to stop on a selector of any other group. In case no apparatus units are in'the waiting position of either main group the relay 430 will continue actuated until an apparatus unit of either main groupv is disassociated from a cooperating selector, when the said unit will be directed to an idle selector of the second sub-group.

In the same manner as in the lastforegd ing, if no apparatus unit is associated with a disengaged selector'of the third sub-group, and-one or more of the selectors'thereof has its shaft at normal, and, therefore, relay 431 will be actuated, the selectors which may be seized by an apparatus unit which may be in a resting position or hunting, will be in the third sub-group, which is'common to bothmain groups. And in the same manner, if no apparatus unit is associated with a disengaged selector of the fourth sub-group, .and

one ormore of the selectors thereof has its shaft at normal, and, therefore, relay 432 will be actuated, the selectors which may be seized by an apparatus unit which may hair. a resting position or hunting, will be in the fourth sub-group, which appear in the'second main group only. I

In connection with the latter, itwill be noted, the first main group is not concerned,

that is conductor 414 is not grounded, but conductor 437 is grounded through armature 451. It will be noted here that when any selector of the first sub-group has an apparatus unit'associated with it, and the said selector has its shaft standing at the first off-normal position with its off-normal sets FON and AFN operated (the selector may or may not be in seized relation with a lineswitch at the time), the conductor 457 will be grounded. This is due to the right hand springs of the off-normal sets AFN, AFN, and AFN being in multiple relation with said conductor 457, and that when a shaft is standing at its first off-normal position a said spring thereof will be grounded. The object of the latter provision is to insure all the selectors of the first sub-group being barred against a hunting apparatus unit if one of the selec tors of the said sub-group is in relation to a said unit and the shaft .thereof is at normal and the selector is unseized. The latter statement is to say that if the selector is seized by a lineswitch, whereby the calling party has not as yet sent the first directive impulse, and, therefore, the shaft will be in the same physical off-normal state as if the selector had not been seized, the conductor 457 would not then be grounded due to the fact that the ground applied to ri ht hand spring of the ofl-normal set AFN, or example, is received through grounded armature 169, armature 182, wiper 174, bank contact 173, conductor 368 and spring 382, the said path being opened at armature 182 when the selector is seized due'to relay 109 actuating. Under this condition, while the conductor 457 becomes grounded upon the selector being seized by an apparatus unit, and thereb bars any idle selectors remaining in the su -group containing it, upon the selector being seized by a lineswitch, the conductor 457 becomes ungrounded and the idle selectors of the said sub-group are then subject to seizure by a hunting apparatus unit.

. In a like manner sprin 460 and 461 are caused to be grounded t rough conductors 368 and 368 over a corresponding path in an engaged selector as was traced from the corresponding conductor 368, to the grounded contact 11 on which armature 169 normally rests. t will now be manifest, that if a selector is seized by a lineswitch, and the calling party does not forthwith start the directive impulses, the idle selectors of the concerned sub-group will not be barred falsely against a hunting apparatus unit, so that a said apparatus unit can seize and adapt the latter seized selector for seizure by a lineswitch, notwithstanding the said selector last seized has not been operated directively by the calling party.

With reference to relays 408, 430, 431, and 432, it will be noted that they each derive energizing current through chained armatures of the precedingrelays. This is to insure that one only of the said relays can be operated at any time; the relays predominating from the left. Otherwise, a condition may be wherein. all subroups of a main group could become falsely arred, as by the relays 430 and 431 actuating coincidentally, for examle. It will be noted in this connection if rciiiy 432 becomes actuated, conductor 414 will not become grounded, so an apparatus unit of the first main group which may occupy the resting position will not be caused to hunt.

\Vith reference to the bank contacts shown in G and H, it will be understood that the right hand contact adapted to be engaged by wiper 176 is dead, and that the first nine con t acts adapted to be engaged by wiper 178 appertain to conductors of nine accessible first selectors, while the tenth bank contact only refers to the waiting position. It will be manifest that a plurality of waiting bank positions may be provided for waiting positions by tying them in multiple. The latter bank positions, of course, would not be available for co-operating selectors. In this connection, it will appear, a greater number than nine selectors may be inaccess to the apparatus units and the lineswitches, in fact, in commercial installations the number would usually be twenty-five or more, the suboups each having five or more selectors, in ieu of three as described in the exampled system.

Going back to the condition of the circuits wherein the party at tele hone T5 was in telephonic relation with t e party at telephone T3, bearing in mind the relation of conductor 243 to the said connection for recording duration charges. It will be assumed that the party at telephone T5 relaces the receiver thereat 0n the switchiook to terminate the service. The connector CON'will operate, in the well known manner, responsive thereto and remove the ground from conductors 351, 339, and 532, which will deenergize relays 517 and 335, the relay 301 'being maintained energized through off-normal spring 379. Upon the deactuation of relay 335, a circuit can be traced from the winding of release magnet Re3, armature 367 to grounded armature 366, the release magnet operating to restore the shaft of selector C to normal, incidentally disengaging spring 379 when the shaft leaves the second off-normal position in restoring, thereby causing relay 301 to deactnate. U on the shaft arriving at normal, ground Wlll be applied through spring 372 to bank contact 510, and its multiples, to uard the selector C against seizure, groun ed armature 366 maintaining a ground upon conduc tor 380 to bank contact 511, and its multiples, consistent with the slow-releasing characteristic of its relay 301, so that the bank contact 511 will constitute ground potential, at least until the ground is re-applied to bank contact 510 through sprin 372. That is to say, at no time since the se ector C was first seized by the lineswitch D has both bank contacts 510 and 511 been free from ground simultaneously. The object of the novel arrangement whereby the lineswitch D has an auxiliary private wiper and co-operating contacts is to insure that when a lapse of ground potential occurs to conductor 532, causing the private bank contact 510 to become ungrounded and the selector C is caused to restore, as set forth in the last foregoing, the said selector is not un uarded with respect to other lineswitches w ich may be hunting or in a seizing state with reference to the said selector C. Undersuch condition the relay of the lineswitch concerned corresponding to 517 will be in a deactuated state, and, therefore, the wipers correspondin to 513 and 514 will be tied. In view ofthe act that bank contact 511 and its multiples will constitute ground potential received from

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