US1729854A - Multioffice telephone system - Google Patents

Description

Oct. l, 1929. M. L. NELsoN 1,729,854

mnorncs umsrnoun sysrtsm l original Filed Jan. 9'. 192e '7 sneet-shee 1 Oct. 1, 1929. M. L NELsoN IULTIOFFICE TELEPHONE SYSTEM 7 sheets-shea 2 Original Fl'ed Jan. 9. 1926 #SNS QM. wil 11 Oct. 1, 1929. M. l. NELSON 1,729,854v

IULTIOFFICB TELEPHONE SYSTEM k U'ignal Filed Jan. 9. 1926 7 Smets-Sheet 5 ,edf

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Oct. l, 1929. M. L. NELSON `IULTIOF'EICE TELEPHONE SYSTEM v"I Sheets-Sheet 4 Original Fled `Jan. 9, 1926 MSSJ www1

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HULTIOFFICE TELEI'HONE SYSTEM Original Filed Jan. 9. 1926 7 Sheets-Sheet 5 g m u i :l N v .Imran Ur Oct. l), 1929. M L NELSQN 1,729,854 '3;

IULTIOFFICE TELEPHONE SYSTEM Original Filed Jan. 9, 1926 7 Sheets-Sheet 6 i Wvg-WH LUL QL @wl m NBN TQ@ Cet. l, 1929.

M. l.. NELsoN 1,729,854

IULTIOFFICB TELEPHONE SYSTEM Original Filed Jan. 9. 1926 7 Sheets-Sheet 'T Patented Oct. l, 1929 'UNITED STATES PATENT-f OFFICE y MARTIN L. NELSON,

WARE

OF PABX RIDGE, LLLNOIS, ASSIGNOB, BY MESNE ASSIGNMENTS, T0 AUTOMATIC ELECTRIC INC., OF (YIHICAGO,

ILLINoIs, A conroaArIoN or nnte- MULTIOFFICE TELEPHONE SYSTEM The present invention relates to multi-oftice telephone systems in general, but is concerned more particularly with multi-oliice telephone systems in which directors are employed to register the oice designations of the calls and direct the calls to the designated offices, and to register and retransmit the subscriber-designating digits of the number 1n order to complete the connection to the desired station.

The present invention is directed to a number of points in the operation of a comprehensive director system among which appear the following outstanding points:

One object of the invention is to bring about a reduction in the number of terminals required on the oince-register side of the intermediate distributing frame by connectino* certain contact sets inthe bank of the oiipce register to the same set of terminals in case the wipers of the office register are brought into engagement with the several sets of bank contacts in response to the dialling o equivalent designations as will hereinafter appear.

Another ob]ect of the invention is to arrange the director so thatit normally ren` sponds to and retransmits four subscriber digits, but will respond tov and retransmit five subscriber digits in case the first two subscriber digits received are such as to indicate that the number being called a five digit number.

Another object of the invention is to provide a director whichafter registering four digits in a number that is not a regularl live digit number will wait a.jsuiliciently long period of time to enablecthe calling subscriber to dial a party-designating digit before switchin through so that those lines which are reac ed by the calling of four subscriber digits may be reached by party line connectors provided with a party selecting switch operated by the `receipt of .a partydesignating digit after the connector has been set upon the called line.

Another object of the invention has to do with arrangements for freeing the director in case a calling subscriber delays dialling for longer than a predetermined time, and

consists in the provision of a desirable arrangement whereby a reasonably long time 1s allowed after the removal of the receiver and before the dialling of the' rst digit to permit the calling subscriber to recall the number, together with the arrangement whereby, after the iirst digit has been dialled, a considerably shorter time is allowed between the dialling of successive digits.

A further object of the invention is the production of a. new and improved cam-type impulse sender, and more specifically of the type which completes its cycle of .operations upon the transmission of each digit and starts over again for the following digit, as distinct from the type in which the transmission of a complete number constitutes a single cycle of operations. lt is more specifically an object to provide a cam sender of the above type having improved pick-up and lstop circuits for starting and stopping the impulses in an outgoing control circuit separate from the pick-up and stop circuits themselves.

AV further object is the production of a new and improved timin system whereby the timing devices individual to separate directors may be all operated from a common source of power to which they are connected and from which they are disconnected each under the control of the associated director.

In addition to the foregoing outstanding objects of the invention, there are a number of more or less minor objects and special features.

One ob'ect ont the latter class is the provision o suitable circuit arrangements whereby the timing device which is started into operation upon the registration of the fourth subscriber digits is prevented from switching the connection through and free- .ing the director at the end of the interval for -which it is adjusted in case all the registered the fourth subscriber digit in cases when the lpredetermined time interval hasl alreadyT .elapsed when the transmission-of the fourth subscriber digit is effected, provided the fth digit register has been operated.

There are other objects 'and features of the invention which for the. most part have to do with the circuit details, which objects and features will become apparent upon a- ;further perusal of the specification.

Referrlng now vto the accompanying drawings comprising Figs. 1,-8, Figs. 1-6 show by meansl of the usual circuitdiagralns certain apparatus in a system embodying the` principles of the invention; Fig. 7, is a top.

Z, appear through the finger holes 2-9 of the finder hold dial of the calling device. rllhese letters are placed'on the calling device so as to enable the calling subscriber to call oihce designations by means of combinations of letters rather than by means of 'combinations of numerals. For exam le, in a system in which two office-designating digits are used, the calling subscriber dials those digits by selecting the holes through which appear the corresponding letters. For example, the telephone number Main 4926 is listed. in the telephone directory as MAm 4926. It will be noted that the dialling of MA, with the calling device shown, is the same as dialling 62, but the telephone numbers are much more easily remembered in case, they are listed in this manner.

Similarly, in case three chine-designating digits are used, the first three letters of the officename are u-sed and the number Main 4926 is listed in the directory as MAln. 4926. It will be noted that the numerical equipment of the designation l is 624.

It will be noted that there are no letters appearing through the rst and tenth finger holes. The reason for this will now be eX- plained. llt often occurs that a subscriber, on removing his receiver, inadvertently jars the telephone, or strikes the receiver against the hook after it has been raised and before it has been sufiiciently removed, with the result that a single interruption is produced in the line circuit after it has been closed. rllhis momentary interruption has the same effect' upon the exchan e apparatus as the calling of the digit 1. -ccordingly it has been arranged so that no ofiice designation begin with the digit 1 with the result that the registration ofthe digit 1 at the exchange can be always wiped out in case the digit is'thel when the digit 0 isdialled is the toll-recording'o'perator. In other instances the operator reached when'the digit 0 is dialled is not the toll-recording operator but` is a special voperator known as the zero operator ,who is assigned the duty of rendering assistance in completing the `connection in case the subscriberis havin difficulty in obtaining a certain number and'therefore dials the digit O to solicit the aid of the zerofoperator.

Referring now particularly to thecircuit drawings including Figs. 1-6, Fig. 1, shows thel selector S accessible to the line switches through the conductors 5, 6, and'7. This drawing shows the trunk circuit TC whichis insertedin the trunk between the banks of the line switches and the selector S, and'also the secondary switch SS, which is individual to the trunk. The trunk circuit TC is provided for the purposeof enabling a director to be associated with 'the connection to handle the call. The secondary switch SS has access to a number of director selectors one of which is shown in Fig. 2, and it is provided in order to reduce the number of director selectors, as the director selector is required and rotary switch having sets of bank contacts arranged in horizontal rows or levels.

The director selector is used to select the group of directors corresponding to the iirst letter dialled. That is, the directors are arranged in eight groups, one for each of the holes of the calling device through which appear the letters of the alphabet.

On one level, the director selector DS has access to the director shown in Figs. 3 6 and to other similar directors.

Since the director selector Fig. 2 responds to the first digit dialled, this switch is arranged vto absorb the digit 1. When it responds to the digit 1 the director selector DS restores its shaftand wipers to normal preparatory tov responding to a subsequently dialled digit, as the digit l does not form part of any number when it is received as the first digit. Another point in connection with the director selector DS is that, whereas the levels 2,-9 lead to eight groups of directors that handle regular calls, each of the trunk lines from the tenth level of the director selector leads to a special director which, upon being seized transmits the digits necessary to trunk the call to the zero operator. These special directors are not shown herein but they may seized immediately upon the removal of the receiver, ing device, clutch 'magnet 102, which operates the special switch-through springs 103. This timing device begins to operate when the director selec? l tor is seized, and in case no dialling occurs during thirty seconds the springs 103 closewith the result that the connection is switched through to the selector S, Fig. 1,' in a manner to be pointedout more in detail herelnafter. In case a digit is received before the 304 second time interval is up, the director selector operates in the usual manner to extend a.

connection to an idle director, for example, the one shown in Figs. 3-6. When this occurs the timing arrangement shown in the lefthand end of Fig.' 5, starts to operate with the result that if no digit is received within the next ten seconds the callv is switched through but the connection is first extended to a monitoring operator in a manner to be hereinafterpointed out. The arrangements are such that the timing device is released after the dialling of each digit so that the calling subscriber is allowed ten seconds in any case after the preceding digit has been 'dialled, except following the `fourth digit of a. number indicating a line reached by four digits. In this-case the 5-second cam of the timing device shown on,the left hand end of Fig. l5 comes into play with the result that if the calling subscriber does not dial a party selecting digit within live seconds the call is switched through under the assumption that the line called is not a party line. It will be noted that the 10-second cam is arranged to release any partially set up connection and dial up the number of the monitoring operator, whereas the 5-second cam is merely a switch-through cam as will be hereinafter pointed out.

It may be conveniently pointed out at this time that the portion of the director shown in Fig. 3 comprises the sequence switches Slt and SE,together with certain relays. The sequence switch SE is provided for the purpose of distributing the series of incoming impulses to the operating magnets of the registers in turn. The sequence switch SS is provided for the purpose of rendering the various registers of the director operative one after the other to control the operation of the sender. i

The portion of the'director shownin Fig. 4 comprises the cam sender shown on the right hand end of the sheet, together with certain relays.

The portion of the director shown in Fig. 5 comprises the office register OR and the intermediate distributing frame I.D.F. The office register mechanically is similar to the this selector is provided with a tim-v includine' the cam 101 and the' director selector DS, Fig. 2, iand to the selec; tor S, Fig. 1, in that its bank contacts are arranged in ten horizontal rows or levels with vten sets of bank contacts in' each level. This drawing shows also the timing device TD which is used to time the operations in a manner explained generally hereinbefore and to be explained more in detail hereinafter.

The portion of the director shown in Fig. 6 includes the digit registers DR1DR5 together with the relays 506 and507. The mechanical construction of each of the digit `registers shown in this drawing is substantially the same as the mechanical construction of the sequence switch SE, Fig. 3. That is, each switch has an operating magnet that moves the wiper assembly in a single plane, and a release magnet that subsequently restores the wiper assembly to normal.

Regarding the mechanical construction of the sequence switch SE', Fig. 3, it may be pointed out that this mechanical construction is indicated diagrammatically in the drawings from which it may be seen that the wipers are advanced upon the back stroke of the stepping magnet 217 and that no release'magnet is provided, the stepping magnet being merely reoperated step-by-step to advance the wipers to their normal position.

The mechanical construction of the secondary switch SS, Fig. 1, is similar to that of the sequenceswitch SE, Fig. 3. It may be pointed out, however, that no provisions are made for advancing the secondary switch SS to a normal position at the end of each call. Instead, the wipers of the secondary switch SS are advanced one step at the end of each call in a manner to be pointed out hereinafter so as to give a distribution of tratlic such that the next call coming in over .the trunk line associated with the secondary switch SS will not'take the same directorv the timing device TD, Fig. 5, it may be pointed out that this timing device includes an armature 404 associated with the clutch magnetv 405, the ratchet segment 403, and the cams 401 and 402. There is a shaft 406 constantly rotating and common to a plurality of timing devices. This rotating shaft is provided with wings 407 and 408. In its normal position the segment 403 is out of reach of the wings 407 and 408 of the common shaft, and theteeth of the segment 403 are out of reach of the retaining spring 409. When the clutch magnet 405 energizes, however, the armature 404 moves to the right bringing the segment 403 into such a position that when it is rotated in a counter clockwise direction the retaining spring'409 maintains it in its position. In this position of the segment 403, the said segment is advanced one step in a counter clockwise position each time one of the wings of the shaft 406 roasV cams 401 and 402 are brought to the-bright so that they are in position to operate the associated springs when the segment 403 has been advanceda suiiicient number of steps. Then the clutch magnet 405 deenergizes, the armature 404 moves to the` position shown in the drawings whereupon the teeth of the segment 403 are disengaged from the retaining spring 409 with the result-that the segment 403 and the cams 401 and 402 assume the position shown in the drawing. v

The timing devices TD', F ig. 2, and TD2, Fig. 3, are of similar construction, but the armatures and locking segments have not been shown so as not to unduly complicate the drawings. It will be noted that the cams of the timing devices TD and TD2 are each labeled 30-second cam, whereas the cams of the timing device TD, Fig. 5, are labeled ten-second cam and live-second cam, respectively. Accordingly, the timing devices TD and TD2 are operated at a slower rate than the timing device TD. This may be accomplished by providing a common operating shaft such as 406 except that it runs at a correspondingly slower rate.

Four-digit party-Zine @ad The disclosure in the drawings havingbeen described generally, a detailed description of the operation will now be given. For this purpose it will be assumed that a certain calling subscriber desires toconverse with'the subscriber whose number is listed in the di rectory as WIChita 6826 J. This number it may be pointed out is a four-digit party-line number. That is, in addition to the exchange designation, the number contains four digits to designate the line, and the party designating character J which designatesthe desired station on the called line.

It will be assumed that when the above mentioned calling subscriber removes his receiver, the line switch individual to the calling line seizes the trunk circuit TC, Fig. 1, at the terminals 2 4. When this occurs line relay 8 of the trunk circuit TC energizes over conductors 5 and 7 and over the calling line. Upon so doing, line relay 8 closes at armature 14 a circuit from ground through release relay 9, the working Contact and armature 14, and through the switch-through relay 10 to battery. Relay 9 energizes over this circuit but relay 10 does not operate owing to the fact that it is shiftly adjusted. Upon operating, release relay 9 places ground on release trunk conductor 6 at armature 15 so as to guard the trunk against seizure and to maintain the calling line switch operated; connects test wiper 32 of the secondary switch SS to the junction of the winding of switching relay 11 and stepping magnet 30 at armature 18; and at armature 17 closes a circuit through switching relay 11 and stepping magnet 30 in series.

From this poingthe operation depends upon whether the trunk upon which the wipers of thel secondary switch SS are standing is idle or busy. If this trunk is idle, the connection of test wiper 32 to the junction of the windingof switching relay 11 and the.

stepping magnet is of no consequence and switching relay 11 energizes right away, seizing the trunk.

If, however, the trunk is busy, there is a ground potential encountered on the busy test contact by test wiper 32 with the result that switching relay 11 is short circuited, and does not energize. This same ground potential provides an operating circuit for stepping magnet 30. Stepping magnet 30, being self interrupting, operates in a buzzer like manner and advances the wipers 31- 34 step-by-step in search of an idle trunk.. Assuming that the trunk comprising conductors 35-38 is the irst one found to be idle, the wipers of the secondary switch SS stop when vthis trunk is reached on account of the fact that there is -no ground potential encountered on the test contact by test wiper 32. Stepping magnet 30 does not energize at this time owing to the high resistance of switch ing relay 11, but switching relay 11 energizes; connects up the outgoing impulse wipers 31 and 34 at armatures 25 and 29; disconnects at armature 26 release trunk conductor 6 from release trunk conductor 6 so as to enable any partially set up connection, including the selector S, to be released without releasing the calling line switch; prepares the impulse circuit at armature 28; and at armature 27 disconnects test wiper 32 from t-he junction of its own winding and that ot' stepping magnet 30 and connects it to ground instead, thereby making the seized trunk busy.

As a result of the seized trunk being'made busy by the application-of ground potential to the release trunk conductor 36. release relay 104 of the director selector DS, Fig. 2, to which the seized trunk extends, energizes over conductor 36. At armature 116, relay 104 closes a circuit for the clutch magnet 102 of the timing .device TD with a result to be described more in detail hereinafter; it opens a point in the circuit of release magnet 108 and places ground on conductor 117 at armature 121; and at armature 122 connects up the lead 137 from the dial tone transformer. When this occurs, current from the secondary winding of the dial tone transformer flows through oE-normal spring 110 and its lower contact, resistance 115, lower portion of the three plate condenser 113, normally closed contacts controlled by the eleventh-rotary-step spring 110,` conductor 37, wiper 33, armature 28 and its working contact, the small tone condenser 13, and the resting contact and armature 24 to the lower talking conductor 7. From this point, the tone current flows back to the calling line and is provided with a return path to ground over' the upper line conductor, and over conductor 5 from which point itiows throu h armature 19 and its resting contact an the v upper winding of the line relay 8 to ground through the exchange battery.

Upon hearing. the tone produced by the flow of the dial tone current, the calling subscriber knows that the exchange apparatus is in readiness for him to begin to c all the number.

When the calling device is manipulated 1n accordance with the first character W in the desired number, nine interruptions are produced in the circuit of line relay 8 of the trunk circuit TC, Fig. .1, as the letter W appears through the ninth hole in th calling device, Fig. 7. Each time line rela 8 falls back, it places ground at the normal y closed contacts controlled by armature 14 on the impulse conductor 39, at the same time disconnecting the switch-through relay 10 from such conductor at armature 14. This operation short circuits the release relay 9 and provides an operating circuit for the vertical magnet of the director selector DS, Fig. 2. The release relay 9 Vdoes not fall back during the deenergizations of line relay 8, `even though it is short circuited each time line relay 8 falls back as a short circuited relay is slow to release. The circuit of.th e vertical magnet of the director selector DS, Fig. 2, is as follows: from ground by way of the impulse conductor39, working con tact and armature 28, wiper 33, conductor 37, normally closed contacts controlled by the eleventh-rotary-step spring 110, normally closed contacts controlled by armature 129. series relay 105, and vertical magnet 118 to battery. Vertical magnet 118 and the series relay 105 are unable to operate in seriesv with the relatively high resistance release relay 10 of the trunk circuit TC, but

the series relay 105 and vertical magnet 118 both energize when the said release relay is short circuited by the line relay. Each time the line relay energizes following a deenergization produced by the calling device, it

reestablishes the circuit ofthe release relay.

through the switch-through relay 10 and over the operating conductor. The vertical magnet 118 quickly deenergizes in response to this operation,but the slow acting relay 105 remains operated throughout the series of impulses. 'At armature 124, relay 105 opens a point in the special release circuit. At armature 123, relay 105 prepares acircuit for stepping relay 106 and opens a point in the circuit of rotary magnet 114.

When the switch shaft has raised .the wipers as far as the second level, the special release-control springs shift. At contacts 111 a point in the special release circuit is ture 125 which includes the interrupter contacts 132 of the rotary magnet 114. At armature 126 relay 106 prepares a circuit for the rotary magnet. v

When the series of impulses is terminated the slow acting series relay 105 falls back an closes at armature 124 a point in the special release circuit, but this circuit is notji'completed owing to the facty that contacts 111 are open, as the shaft has been raised above the Iirst level of bank contacts. .At armature 123, relay 105 opens the initial circuit of step ping relay 106- and completes-the circuit of the rotary magnet through the working contact and armature 126. Rotary magnet 114 'asV now energizes and advances the wipers 133-136 into engagement with the first set of v bank contacts in the ninth level. Near the end of its stroke, rotary magnet 114 opens the circuit of relay 106 at interrupter contacts 132, whereupon relay 106 fallsback-and opens a further point in its circuit of armature 125, at the same time opening the circuit of rotary magnet 114 at armature 126. Rotary'magnet 114 now falls back and closes the interrupter contacts132 again. From this point the operation depends upon whether the trunk line terminatin in the first set of bank contacts is busy or ldle. If this trunk line is idle, switching relay 107 energizes in series with stepping relay 106, but stepping relay 106 does not operate on account of the relatively high reslstance, of relay 107.

Assuming that the trunk line is busy, switching' relay 107 is short circuited and stepping relay 106 is' operated by the ground potential encountered on the bu test contact by test wiper 135. The operation of stepping relay 106 results in the closure at armature 126 of an 'energizing circuit for rotary Ymagnet 114. vThe wipers are accordingly advanced another step whereupon relay 106 again lfalls back when itis opened at contacts 132. y

This alternate operation of relay 106 and magnet 114 continues until an idle trunk line is' reached, which trunk line, it will be assumed, is the one comprisin conductors 3538. When this idle trun is reached, switching relay v107, being no longer short circuited, energizes in series with relay 106 which, as above pointed out does not energize on account of the relatively high resistance of switching relay 107. Upon operating, switch r ingv relay 107 opens the circuitl of clutch magnet 102 at armature 128; it disconnects test wiper 135 from the test circuit at armature 130 and connects it to ground, thereby making the seized trunk busy; extends the incoming impulse conductor 37 throughto wiper 134 at armature 129, at the same time cutting oi the branch leading to the vertical magnet 118; and at armatures 127 and 131 connects the outgoing impulse conductors 35 and 38 to the wipers 133 and 136. This latter operation results in the energization of the line 51 of thc selector S, Fig. 1, over conductors 5 and 7 through contacts of relays 10 and 11, wipers 31 and 34, conductors 35 and 38, armatures 127 and 131 and their working contacts, wipers 133 and 136, conductors 35 and 38', and the outgoing impulse control circuit of the director, which includes the resting contact and armature 222, Fig. 3, conductor 242, armature 308 and its resting contact, Fig. 4, and arma'- ture 317 and its resting Contact ot relay 306, in multiple with the sending contacts controlled b cam 341. Line relay 51` of the selector upon energizing, closes at armature 56 a circuit for release relay 52. Relay 52 energizes and places ground on the release trunk conductor 6 at armature 57, and atarmature 58 opens a point in the circuit ot release magnet 66 and prepares a circuit for vertical magnet 68.

ln the seized director, the grounding oit" release trunk conductor 37 by switching relay 107 of the director selector DS, Fig. 2, results in the energization of release relay 304, Fig. 4, through armature 315 and its resting contact. Upon operating, relay 304 opens certain normal restoring circuits at armature 312 and 314; it places ground on conductor 247 at armature 313, which results in a ground potential being extended over conductor 247 and through armature 226 and its resting contact to wiper 212 of the sequence switch SE; and at armature 322 it closes a circuit over conductor 252 and through the jumper 418 for the clutch magnet 405 of the timing device TD, ground potential being applied to the working contact of armature 322 from armature 203 of relay 201 and its resting Contact, resting contact and armature 230, and conductor 249.

When the calling subscriber dials the second character 1 of the number, four impulses of current are transmitted over the impulse conductor 37 to the director selector DS and through the director selector DS to the wiper 134. From this point the impulses traverse the operating conductor 36', armature 307 and its resting contact, conductor 241, series relay 201, Fig. 3, armature 231 and its resting Contact, wiper 231 of the sequence switch SE and its first bank contact, conductor 262 to vertical magnet 420 ofthe office register OR. ln response to the four impulses of current, the vertical magnet 420 raises the oiiice register wipers 426-429 opposite the fourth level of bank contacts. Series relay 201, Fig. 3 energizes upon the receipt of the lirst impulse and maintains its armature 203 attracted throughout the entire series ot impulses. At

armature 203 relay 201 closes a circuit for the associated slow acting relay 202 with the result that relay 202 energizes and prepares a circuit for magnet 208. It will be noted that armature 303, at its resting contact, opens the previously traced circuit for clutch magnet 405 of the timing device TD so that the tlming device TD is returned to normal.

When the slow acting relay 201 falls back upon the termination of the series of impulses, it opens the circuit of relay 202 and closes, through the resting contact of armature 203 and through armature 204 and its working contact, a circuit for stepping magnet 208. Magnet 208 energizes and advances the wipers 212 and 213 of the sequence switch SE one step. After an interval, relay 202 falls back and opens the circuit of magnet 208. When the calling subscriber dials the neXt character C, two impulses of current arc transmitted to the director over the previously traced circuit as far as wiper 213 of the sequence switch SE, and, since wiper 213 is now on its second bank contact, the impulses are delivered over conductor 263 to the rotary magnet 419 of the oce register OR. Accordingly, the wipers 426-429 are rotated two steps and are brought into engagement with the upper set of bank contacts shown in the drawing and labeled (42) By the operation of relays 201 and 202 the magnet 208 of the sequence switch SE receives another impulse of currentJ and steps the wipers 212 and 213 into engagement with the third set of bank contacts. The grounded wiper 212 at this time places ground on vconductor 354, thereby starting the transmission of impulses in a manner to be subsequently pointed out.

The seriesof impulses representing the first subscriber digit 6 is transmitted over the previously traced circuit to wiper 213 of the sequence switch SE and this series of impulses is delivered over conductor 264 tothe stepping'magnet 501 of the digit register DR-l,

Fig. 6; the series of impulses representing the second subscriber digit 8 is transmitted over conductor 265 to the stepping magnet of the digit register 13R-2; the series of impulses representing the third subscriber digit 2 is transmitted over conductor 266 to the stepping magnet of the digit register Dlt-3; the series of impulses representing the fourth subscriber digit 6 is transmitted over conductor 267 to the stepping magnet of the digit register Dlt-4; the series of impulses representing the station-designating character J and comprising five impulses is transmitted over conductor 268 to the stepping magnet of the digit register IDR- 5. In the above manner the digit registers DR-l-DR- are set in accordance with the thousands, hun- Y series of impulses; Thatl being' the case, the removal of the shunt from around the Wiper 213 lands on a dead contact at the. end

of the setting of the digit register DR-5 and the wipers 212 and 213 remain in this' position until the director is released.

The description Vof the registration of the number havingjbeen completed, a description of the operation of the sending portion ofthe director Will non7 lie-given. v Returning now to the point at which the Wipers of the sequence switch SE advance from the second to the third position at'the end of the rotary movement of the" ofiice register OR, the grounded Wiper 212, upon coming into engagement With its third ban contact, places ground on conductor 354.

'conductor 342.

This operation renders the stop conductor control Wiper 221 of the sequence switch SE alive and extends a ground potential through lthe first contact in the bank 'of Wiper 220,',`

conductor 251, armature 310 of relay 302 and its resting contact, and start conductor 321 `to the pick-up springs controlled bythe pickup cam 330 of the sender. This does not produce any particular results until the sender arrives in its pick-up position, at Which time acircuit is closed through the springs con trolled by the pick-up cam 330 for the upper winding of relay 306. Relay. 306 energizes over its pick-up Winding and closes a locking circuit for itself at armature 319to the stop Stop conductor 342 is at this time grounded over the following circuit: from ground by way of the grounded conductor 354, Fig. 3, Wiper 321 of the sequence switch SE and its first bank Contact, conductor 270, Wiper 426 of the oflice register OR, the bank contact on which ,it is standing, the associated jumper which connects the bank contact -terminal of the With the terminal on the opposite side corresponding to four impulses and leading to the fourth impulse stop conductor (as indicated by the numeral 4 placed Within the circle to the left of the I.D.F.), the fourth impulse stop conductor, the springs controlled b the fourth impulse stop cam 334 of the sen er, stop conductor 342` armature 319 and its Working contact, and theloWer Winding of relay 306 to battery.

v As -a further result of the energizationy of the combined .pick-up and stop relay 306, a

i circuit is closed at armature 318 and over sending contacts", the cam 341 permits the sending contacts to open once after which they are again closed andthe cam 331 disconnects thefirst impulse stop conduc-tor from' conductor 342 so that', if the locking circuit of relay 306 is controlled over the first impulse stop conductor, relay 306 will fall back. The locking circuit is through the fourth impulse stop conductor at this time,-however, and relay 306 therefore remains energized until four interruptions have been produced in the outgoing control circuit at the sending contacts controlled by armature 341. At the end of the fourth interruption, the cam 334 opens the associated contacts with'the result that relay 306 falls back and opens a further point in the locking circuit at armature 319; stops the transmission of impulses at armature 317 by shunting the sending contacts; and at armature 318 opens the'circuit of `stepping' magnet 217 of the sequence switch SE, with the result that magnet 217 falls back and advances the Wipers 218, 220', and 221, one step. y

' The cams of the sender continue to advance, but nothing more is done toward the transmission of'impulses until the pick-up position is reached the next time. It may be conveniently pointed out at this time that the spacings of the cams and cam cuttings are so arranged that invca/ se th'e digit 0 is transmitted, which is lthe longest'digit, enough time elapses following the termination of the last interru tion of the outgoing control circuit to enabie a selector switch to complete its trunk hunting operation before the pick-up position is reached the next time.

The eHect-of the transmission of the lirst code digit 4,4Will now be considered. Referring now to the selectors S, Fig. 1, line relay 51 falls back each time the outgoing control circuit is opened by the sender. Each time it falls'back, line relay 51 closes at armature 56 a circuit through armature 58 and its Working contact, and series relay`53, for

vertical magnet 68, which magnet is connectedto battery through armature 21 and its resting Contact of the switch-through relay 10 of the'trunk circuit TC. By the operation of vertical magnet 68, the Wipers 72-74 are raised opposite the fourth level of bank contacts, l-elay 53 is energized upon the l'irst impulse of current and maintains its armature attracted throughout the series of impulses. At armature 59, relay 53 opens a point in the circuit of rotary magnet 69 and prepares a circuit for stepping relay 54, which is completed at ofi' normal contacts 71 through the interruptor contacts 70, upon the closure of the off-normal contacts 71 when the shaft moves from its normal position. Relay 54 energizes over this circuit and prepares a circuit for rotary magnet 59 at armature 6l and it locks itself to ground at armature 60 independent of armature 59 andits Working contact.

At the end of the vertical movement of the selector S, relay 53 falls back and closes at armature 59 the circuit through armature 61 and its working contact for rotary magnet 69. Rotary magnet 69 energizes and advances the Wiper 7 2-7 4 into engagementwith the first set of bank contacts in the fourth level. Near the end of its stroke, magnet 69 opens the interrupter contacts 70 with the result that relay 54 falls back and opens the circuit of the rotary magnet at armature 61. From this point the rotary operation of the selector S is similar to that of the director selector DS hereinbefore described. lt will suiiice to say that the rotary movement of the selector S continues until an idle trunk is reached, which trunk it will be assumed, is the one terminating in the bank contacts 7 5 7 7 When this idle trunk is reached, switching relay 55 operates, but the stepping'relay 54 does not 'due to the relatively high resistance of relay 55. At armature 63 relay55 opens the test circuit and prepares the holding circuit, thereby grounding test wiper 73 to make the seized trunk busy immediately; opens at I armature 64 the circuit of the slow acting release relay 52; and at armatures 62 and 65 disconnects conductors 5 and 7 from the windings of line relay 51 and extends them by way of wipers 72 and 74 and the bank contacts 75 and 77 to the line relay of the selector to which the seized trunk extends.

'lhe line and release relays of the seized trunk now energize and the latter places ground on the associatedrelease trunk conductor which closes a circuit through contacts 76, wiper 73, and armature 63 and its working contact to maintain the switching relay 55 energized after the slow acting release relay 52 has fallen back as it does shortly. y

When the pick-up position of the sender is again reached, the pick-up winding of relay 3 06 is energized over the same circuit as before except, that wiper 220 of the sequence switch SE is'now standing inits second position instead of the lirst. Upon operating relay 306 locks up over the following circuit. From ground by way ot the grounded wiper 221 ot the sequence switch SE the second bank Contact, conductor 271, wiper 427, the bank contacts on which it is standing, the

associated jumper, the third impulse stop` conductor, the springs controlled by cam 333 of the sender, conductor 342, armature 319 and its working contact, and the lower winding of relay 306 to battery. The shunt remains disconnected at armature 317 Jfrom varound the sending contacts until three inand terminates thesecond code digit 3. The

sequence switch SE is advanced one step in the usual manner and the \wip`ers are now in their third position.

Responsive to the transmission of the second code digit 3, the selector seized in response to the transmission of the first code digit 4 raises its wipers to the third level and selects an idle trunk line leading to an oce selector. When the sender arrives in the pick-up position again, pick-up relay 306 again operates and at. this time locks itself energized over the following circuit: from ground by way of the grounded wiper 221 of the sequence switch SE and its third bank contact, conductor 272, wiper lt28 of the oiiice register f 0R, the bank Contact on which wiper 428 is `digit raises its wipersopposite the eighth level of bank contacts and selects a trunk line leading to an incoming selector in the Wichita oce.

The wipers ot the sequence switch SE take another step at this time and wiper 221 places ground on the fourth wiper 429 ot the office register OR over conductor 273. rlhe bank Contact on which wiper 429 is standing is connected by means of a jumper on the IDF. to the skip conductor 260. IThe result is that a circuit is closed over conductor 260 through the fourth contact in the bank of wiper 218 of the sequence switch SE for stepping magnet 217 through the interrupter contacts 219. Magnet 217 energizes over this circuit and opens the circuit at armature 219, whereupon the said magnet deenergizes and advances the wipers 218, 220, and 221 past'the fourth code-digit position. Wiper 221 now places ground on the top wiper of the digit register DR-l through conductor 278, preparatory to controlling the transmission of the first subscriber digit 6. Wiper 220, it will be noted, breaks away from the grounded conductor 354i and makes contact with the grounded conductor 279 which is grounded at this time because the digit register Dlt- 2, Fig. 6, is 0H normal. Utherwise the transmission ot the first subscriber digit is delayed until the second subscriber digit register has gone' oli'- normal, so as to insure that the sender does not attempt to send out a digit before it is registered.

When the sender again arrives in its pickthrough the upper windingxof relay 306. .Re-

lay 306 at this time locks itself energized over the :following circuit: from ground by way vrof the grounded wiper 221 ofthe sequence switch SE', the fifth bank contact, conductor 274, upper wiper of the digit register Dlt-1,

the sixth associated bank contact, the sixthy impulse stop conductor, contacts controlled by cam 3 5 of the sender, and then to battery A through armature 319 and its working contact and lower winding of relay 306.

Relay 306 accordingly remains energized until six interruptions have been produced in the outgoing control circuit at which time its circuitis opened by cam 335 thus terminating the iirst subscriber digit 6.

In a similar 1nannerthe sender obeys the registration of the digit registers Dit-2, Dlt-3,1)R-4, and Dlt-*5 and transmits the characters setup on these registers. it may be pointed out that, with the sequence switch SE in position 6, corresponding to the register DFL-2, the pick-up ground potential is placed on the pick-'up Wiper 220 of the sequence switch SE through oH-normal contacts 503 of the digit register DR-3 and through conductor 280; the pick-up ground potential for starting the transmission of the third subscriber digit is obtained throughoff-normal contacts 504 of the digit register Dlt-4 and through conductor 281 with the sequence switch SE in its seventh position; the pick-up ground potential for the transmission of the fourth subscriber digit is obtained over the same path as the pick-up ground potential for the starting of the trans mission of the third subscriber digit, as the fourth digit register Dlt-4 will have been in 'all cases sufficiently operated to insure that it cannot be overtaken by the sender as the sender must transmit the digit stored on the third digit register after the third digit register has gone off normal before it can start the transmission of the fourth subscriber digit; and the pick-up ground for starting the transmission of the digit representing the stations designation as registered on the digit register Dlt-5 is obtained through armature 203 of relay 201, Fig. 3, and its resting contact, conductor 257, off-normal contacts 505 of the digit register Dit-5, conductor 282, and the ninth Contact in thebank of Wiper 220.

The sequence switch SE advances another step at the end of the transmission of the stations-designating character, and wipers 218, 220, and 221 come into engagement with the tenth set of bank contacts. When this occurs a circuit is closed from the grounded wiper 221, through the tenth associated bank contact, conductor 250, normally closed contacts controlled by qarmature `309, and the lower winding of swltching relay 302 to battery. Switching relay 302energizes and locks itself to the release trunk conductor 37 at armature 309, at the same time opening'its lnitial circuit; opens at armature 310 a point in the pick-up circuit; introduces at armature 308 the resistance 301 in the outgoing-control circuit so as to cut down the current flow in this circuit preparatory yto the operation of the switch through relay 10 of the trunk circuit TC, Fig. 1, and at armature 307 discon nects the incoming operating conductor 36 from the branch 241 and connects it to ground instead. This latter operation results in the energization of switch through relay 10 of the trunk circuit TC and in the short circuit' ing of the release relay 9. Release relay 9, however, remains operated for van interval. Upon energizing, relay 10 locks itself to re- -lease trunk conductor 6 at armature 40; joins the release trunk conductor 6 to the release trunk conductor 6 at armature 22; removes battery at armature 21 from vertical magnet 68 of the selector S for a purpose to be hereinafter explained; connects the incoming conductors 5 and 7 with the corresponding conductors 5 and 7 at armatures 20 and 23; disconnects line relay 8 at armatures 19 and 24.; and at the normally closed contacts controlled by armatures 20 and 23 disconnects the conductors. and 7 from the outgoing control circuit of the director.

A Line relay 8 falls back vdue to being cut off at armatures 19 and 24, and release relay 9 subsequently falls back due to its being short circuited initially vupon the operation of the caving release trunk conductor 6 grounded from the release trunk conductor 6A through armature 22 and its working contact; opens a point in the previously established test circuit of the secondary switch SS at armature 13; vand at armature 17 opens the circuit of the switching relay 11 and closes through armature 39 a circuit for the stepping magnet 30 of the secondary switch SS. Stepping magnet 30 now energizes preparatory toy ad vancing the wipers 31-34=. A moment later the switching relay 11 .falls backand disconnects the wipers of the secondary switch SS, at the same time opening the circuit of the steppingmagnet 30 atl armature'39. Stepping magnet 30 falls back and advances the wipers By the operation of the switches in the Vichitaoiiice the connection hasnow been lextended to the called line and the 'desired substation is now being signalled in the usual manner. Q

Responsive to the dlsconnection of the wipers of the secondary switch SS, release relay 104 of the director selector DS, Fig. 2, falls back and opens at armature 121 the circuit of switching relay 107 with the result that switching relay 107 falls backand disconnects the associated wipers. At armature 121 and its resting contact, relay 104 closes a circuit through off-normal contacts 109 for the release magnet 108 with the result that release magnet 108 energizes and restores the shaft and wipers of the director selector DS to their normal position in the usual manner. The circuit of release magnet 108 is opened at offnormal contacts 109.

In the director, the ground potential is removed from release trunk conductor 37 at the director selector DS when relay 107 falls back. There is a guarding potential maintained on conductor 37 at the director notwithstanding the removal of round potential at the director selector. 'l is alternate guarding potential is connected to conductor 37 through offnormal contacts 211'of the sequence switch SE, conductor 246, and relay 303. The resistance of relay 303 is fairly low, with the result that the director is maintained guarded for the time being. The net result of the removal of the ground potential from conductor 37 at the director selector is the removal of the shunt from around relay 303. Relay 303, therefore, energizes in series with release relay 304 and at armature 311 places ground through the low-wound relay 305 on the restoring conductor 320. rllhis operation closes circuits for the release magnets of the digit registers DR-1DR-5, for the release magnet 420 of the oitice register OR through oft-normal contacts 425, and for the release magnet 209 of the sequence switch SE through armature 225 and its resting contact and oilnormal contacts 210. As a result, the series guard relay 305 operates and disconnects release trunk conductor 37 from release relay v 304 and connects it directly to ground again at armature 315. By this operation relay 304 0R is permitted to fallback whereupon itplaces a shunt around armature 311 and its working Contact of relay 303 atarmature 314; it closes.

at armature 312 a restoring circuit over conductor 245 for the sequence switch SE which includes the multiple restoring bank, wiper 218, interrupter contacts 219 and stepping magnet 217; opens the circuit of the clutch magnet 405 of the timing device TD at armature 322; and at armature 313 it again removes the ground potential from wiper 212 of the sequence switch SE.

Responsive to the closure of the above mentioned restoring circuit, the various switches of the director are brought to their normal positions and when the last switch has been oil"normal contacts 211 of the sequence switch Regarding the established connection, the two subscribers are able to converse with each other over the connection set up when the called man removes his receiver.

When the calling subscriber replaces his receiver, the ground potential is removed from the release trunk conductor of the established connection with the result that relay 55 ofthe selector S and relay 10'of the trunk circuit TC falls back. Relay 55 closes at armature 64 a circuit through armatures 56 and 58 and offnormal contacts 70 for release magnet 66 with the result that the wipers and shaft of the selector S are restored to their normal position in the usual manner.

Four-digit straight-Zine call The description of the operation of the system in setting up a four-digit party-line conn ection having been given, the method of setting up the connection when a four-digit straight-line number is called will now be given. For this purpose it will be assumed that a calling subscriber desires connection with the subscriber whose number is listed in the director as W'IChita 6926.

It will be assumed that the calling subscriber removes his receiver with the hereinbefore described results, and that when the iirst letter W is dialled the director selector DS, Fig. 1, seizes the director shown in Figs. 3-6. That being the case, when the second and third letters l and C are dialled, the wipers of the ottice register OR, Fig. 5, are brought into engagement with the secondset of bank contacts in the fourth level, as before, and the transmission of the code digits is started upon the advance of the wiper 212 of the sequence switch SE into its third position at the end ot the rotary movement of the office register The calling subscriber now dials the remaining portion of the number with the result that the digit registers DR-Ql-DR-i are set in accordance with the designation 6926.

After transmitting the code digits in the hereinbefore described manner, the sender transmits the registered subscriber digits portion of the number, after which the wipers of the sequence switch SE (which have, as hereinbefore described, advanced one step at the end of each digit) advance another step from their eighth position to theirninth position.

1n the ninth position of the sequence switch SE the sender is unable to start to transmit another digit owing to the fact that wiper 220 of the'sequence switch SEI is in engagement with the ninth contact` which is assoclated with the ungrounded: conductor 282. .This conductor is ungrounded it ma be pointed out owing to the fact 'that the igit register D12- 5 is in its normal position.

.Referring now to the timing device TD, the clutch magnet '405 of this timingdevice is energized upon the seizure of the director as hereinbefore pointed out. For convenience at this point, it may be pointed out that the circuit of the clutch magnet 405 is as follows: from ground by Way of armature 203 of relay 201,A Fig. 3, and its resting contact, resting contact and armature 230 of relay 216, conductor 249, Working contact and armature 322 of relay 304,'conductor 252, jumper 418, and clutch magnetl 405 to battery. Since the circuit of the clutch magnet includes normally-closed contacts'of the relay 201, Fig. 3, the timing device TD is restored to its normal position each time a series of impulses is received. y

It Will be noted that the right hand spring of the Contact set 410 'associated With the five second cam 402 is normally ungrounded, and that ground is placed on this springonly -When the fourth digit register DR-4 goesy off-normal. This means that the operation of the five-second'timing device is not effective until the setting of the digit register DR-4 has been completed, the timing device TD being restoredto its normal position during the receipt of the series of impulses to operate the digit register DR-4.

New, at the end ofthe settingof the digit register DR-4, relay 201 falls back and closes the above traced circuit for clutch magnet 405 of the timing device TD. The armature 404 is attracted and it swings the segment 403 and the cams 401 and 402 to the right so that the retaining springs 409 becomes effective, and so that, each time one of the wings 407 and 408 of the rotating shaft 406 passes up on the left-handside of the shaft, the tooth segment 403 is advanced one step. The speed of the rotation of the shaft 406 is such that the enlarged portion of the five second cam 402 comes under the left-hand spring of the contacts 410 at the end of five seconds. When this occurs, a circuit is closed from ground through the off-normal contacts 504 of the digit register Dlt-.#1, conductor 281, springs 410 associated with the cam 402 of the timing device TD, conductor 430, resting Contact and armature 510 of relay 506, relay 507, and the associated resistance 511 to battery. Relay 507 energizes and at armature 512 closes a circuit from the grounded conductor 278 (this conductor is noW grounded by Wiper 221`in its ninth position) ,armature 512 vand itsworking contact, conductor 250, normally closed contacts controlled by armature 309 of the switching relay 302, Fig. 4, and relay 302 to battery. `Switching relay 302 noW energizes with the result that the con- Assuming now that the director shown in ,the drawings is seized and operated in connection With a call to the subscriber Whose number is WIChita 60266, the oice register OR- is set upon the secondset of bank contacts in the fourth level and the digit registers DR-l--DR- are set in' accordance with the subscriber digit of the number. Since the second subscriber digit is 0in this case, the lower Wiper of the digit register DR1 comes into lay to determine Whether the number is a our digit number or a five digit number so as to prevent the simple switchthrough operation at the end of the transmission of the fourth subscriber digit in case the number is a five digit number.

It is assumed that the trunk'ing layout in each of the offices is such that the tenth level of the hundreds selectors in' the thousands groups 6-0 lead each to a special group of hundreds selector instead of to connectors l as they do on the otherv levels. This is done so as to increase the capacity of the offices concerned beyond the ten thousand-line limit of a four digit system. Tt isassumed further that the 0 level of the hundred selectors in` is 0 the director is transformed to a five-digit director in case the first digit is anything from siX to 0, but is retained as a four-digit director in case the first digit is anything from one to five. v

Now, since the second digit of the number at present under consideration is 0, and, since the first digit is six, the director must be prevented from switching through until the fifth digit register Dlt-5 has been operated.

The transmission of the digits necessary to complete the connection takes place in the manner` hereinbefore described until the code digits have all been transmit-ted and until the digit registered on the digit register DR-l has' been transmitted. At the end of the transmission of the first subscriber digit, the Wipers of the sequence switch SE advance from their, fifth position to their sixth position and the grounded Wiper 221 places ground on conductor 275 leading to the vviper of the digit register Dlt- 2. This results in a closure of a circuit 'through said Wiper and through tenth contact in the associated bank, lower Wiper and sixth contact of the digit register DR-l, normally closed contacts controlled by armature 509 of relay 506, and relay 506 to battery. Relay 506 ener-- i gizes over this circuit and'locks` itself to the l tered subscribery digit will be transmitted in the usual manner. It will be noted that relay 506 at armature 510 opens a point in the circuit of relay -507, which is the relay that brings about the switch-through of the connection at the end of the transmission of the fourth subscriber digit as hereinbefore pointed out. That being the case, the switchthrough operat-ion cannot be performed until the end of the transmission of the impulses representing the registration of the digit rc ister DR-5. l The retransmission ot' the digits registered on the digit registers DR-3-DR5 takes place in the hereinbefore described manner after which the grounded wiper 221 of the sequence switch SE comes into engagement with the tenth associated bank contact with the result that the switching relay 302, Fig. 4, is operated in the hereinbefore described manner and with the result described.

[.D.F. arrangement Regarding the novel arrangement of the terminals on the right hand side of the IDF. Fig. 5, it may be pointed out that sometimes a calling subscriber, in dialling the letters of a number, mistakes the digit 0 for the letter O with the result ten impulses are sent instead ofthe intended siX. At other times, the calling subscriber may mistake the digit 1 for the letter I with the result that only one impulse is transmitted instead of four. In order to correct this difficulty, the conductors joining the bank contacts of the oce register to the right-hand side of the IDF. have been arranged so that the calling of the digit 0 has the same eeet as the calling of the letter O and so that the calling of the digit 1 has the same eiiect as the calling of the letter I. For example it will be noted that in Fig. 5 the second set of bank contacts in the first level .and the second set of bank contacts in the fourth level of the oliice register OR connect to a common set of terminals on the right-hand side of t-he IDF. This may be seen in Fig. 8, wherein the space corresponding to the second set of bank contacts in the first level is left vacant and the designation 12 is placed in the same square with the designation 42, similarly the placing of the designation 13 in the same square with the designation 43 is to indicate that the third set of bank contacts in the irst level occupies the set of pins occupied by the third set of bank contacts in the fourth level. A study of Fig. 8, .will reveal that only 64 sets of pin terminals are needed instead of lthe usual 100 sets. vIt will be understood of course that the regular 100 set could be provided in which 'case the combinations could be taken care of by jumpers at the I.D.F., but, since it is a permanent proposition, there is no need to combine the contact set by means of the more or less temporary Jumpers, and as before stated, there is considerable saving in a reductionl 1n the size of the terminal space necessary on the right hand'side of the IDF. Delayed dialling before )i1-st clz'gil It will be assumed 4now that a calling subscriber removes his receiver with the result that the secondary switch SS, Fig. 1, takes the director selector DS, Fig 2, into use, and that the calling subscriber fails to. dial Within the thirty 'seconds allotted for the rst digit to be received. It will be remembered that release relay 104, Fig. 2, pulls up when the director selector is seized and at armature 116 closes a circuit for the clutch magnet 102 of -the timing device TD. This timing device is similar to the timing device TD, Fig. 5, except that the common actuating shaft of the timing device TD (corresponding to the shaft 406 associated with the timing device TD) runs at a correspondingly slower rate.

At the end of thirty seconds, the cam101 closes the contact 103 with the result that ground is placed on conductor 37. This results in the usual operation of the vertical magnet of the director selector DS. A further resultis that, since the line relay 8 of the trunk circuit TC is energized at this time, the switching relay 10, being connected to conductor 39, is energized to switch the connection through in the usual manner. It will be noted that armature 21 of the trunkcircuit switch-through relay 10 removes battery from vertical magnet 68 of the selector S. This is done so as to prevent the calling subscriber from operating the selector S directly romhis calling device in case he later starts to dial.

It will be noted that the `batterysupply of Delayed dialling after 1am/diga It will be assumed now that a calling subscriber removes his receiver and that the secondary switch SS, Fig. 1, responds by seizing the director selector DS, Fig. 1. It will be assumed further thattheponnection maas is extended to the director shown in the drawings when the calling subscriber dials the first digit. It will be assumed still further, that the calling subscriber, either beforeor after dialling other digits, stops dialling before he has dialled the complete-number. In this case the timing 'device TD is not released before the springs 411 are o erated, as is the caseuwhen the calling su scriber continues to ldial until the complete number has been registered. Upon the closure of the contacts 411, a circuit is completed from the grounded conductor 252 through the contacts 411, conductor 258, and the winding of relay 215 to battery. Relay 215'energizes and at armature 227 connect ground to conductor 249 independent of armature 2,03 and its resting contact of relay 201 so as to insure that the cycle of operations will be completed even though the calling subscriber should now begin to dial again. At 'armature 225, relay 21.5 disconnects the release conductor 269 from the branch leading to the release magnet 209 of the sequence switch SE and connects the main conductor 269 to ground, thereby releasing the operated registers. At armature 223, relay 215 connects ground to the bank of the restoring wiper 218 of the sequence switch SE so as to restore that sequence switch to its normal position'in case it` has operated to transmit the stored portion, in case a part of the number has been dialled. At armature224, relay 215.. closes avlocal current for magnet. 208 of the sequence switch SE, causing wipers 212 and 213 tontake one step. At armature 226, relay 215 disconnects ground from wiper 212 of the sequence switch SE and closes anv energizing circuit for relay ,216. Relay 216 energizes and locks itself to the grounded release trunk conductor 248 at armature 220; prepares Vat armature 229 a start circuit independent of wiper 212; breaks the connection between conductors 257 and 249 at armature 230; opens the impulse circuit at armature 231; and at armatures 232-p-235 connects the first four conductors 270-273 leading from the banks of wiper 221 ofthe sequence switch SE to the upper hight-hand set of contacts at the I.D.F. preparatory to transmitting the digits .necessary to trunk the call to the switchboard of the monitoring operator. K

As a further result of the above energization of relay 215, it opens at armature 222 the outgoing control circuit, with` the result that any partially-set-up connection is released.'

After an interval which is suiliciently long to insure the release of any partially set up connection, the ten second cam 401 of the timing device TD, Fig. 5, permits the contacts 411 to open again, whereupon relay 215 falls back, leaving relay 216 locked up to the grounded release trunk conductor at armature 228. At armature 227, relay 215 removes ground from conductor 249 whereupon the clutch -magnet 405 bf the timing device TD deenergizes and restores the timing device to normal. At armature 226, relay 215 connects ground from the grounded. conductor 247 through the working contact and armature 229 of relay 216 to wiper 221, and through the first contact in the bank of wiper 220 to conductor 251. The result is that the sender transmits the digits determined by the connection of the upper right-hand contacts of the I.D.F. The first three contacts of this contact set are jumpered to the fourth, ninth, andv second impulse stop conductors. The sender therefore, transmits the digits 4, 9, and 2 after which the grounding of the fourth contact by the wiper 221 of the sequenc switch SE results in a closure of a circuit rector beingreleased'in the hereinbefore de-` scribed manner.

'and in the director selector DS and in the di- It may be pointed out that the release of the i sequence switch SE, Fig. 3, is prevented as hereinbefore pointed out so that the oiinorf' mal contacts 211 will supply ground to operate the relay 303, Fig. 4, to bring about the release-of the apparatus in the director before the ground potential is removed from the release trunk conductor 37 in the manner here'- inbefore described; and that the wipers of this switch are advanced one step by relay 215 u to that, in case the sequence switch SE is not already off l-when the series relay falls back atethe end of thedigit 1, va circuit is closed at armature 124 through the contacts 111'and the off-normal contacts 109 for the release mag,

normal it will be moved off normal. Y

net 108. -This results in the release of the di- .rector selector. In case the wipers of the director selector are raised opposite any other lever, the contacts 111- are separated and the above special release circuitl is not closed. It

is to be noted also that the circuit` of stepping relay 108 remains open-at contacts 112 when the digit 1 is received.

Two-digit oce-destnation .system iis case, the secondary switch SS, Fig. 1, extends i the connection to a director'upon the removal of the receiver. Therefore, Fig. 1, may be iso

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