US1539925A - Multioffice telephone system - Google Patents

Description

June 2 1925.

B. D. WILLIS \MUL'IIOFFICE TELEPHONE SYSTEM 4 Sheets-Sheet 1 Original Filed Jul 9 B l'nug n DPMZZ Ernar 11s HIT:

B. D. WILLIS MULTIOFFICE TELEPHONE SYSTEM 4 Sheets-Sheet 2 Ori inal Filed Julv 21.

Alllll VIIIII' AAA-AAA IIIIIII 'Inuenlnr Barnard 5.1mm 15 I r June 2. 1925 1,539,925

B. D. WILLIS MULTI OFFICE TELEPHONE SYSTEM Ori ed July 21,

June 2, 1925.

B. D. WILLIS MULTIOFFICE TELEPHONE SYSTEM 4 Sheets-Sheet 4 www Original Filed July 21, 1920 Barnard D 11215 Patented June 2, 1925.

UNITED STATES PATENT OFFICE.

BERNARD D. WILLIS, OF OAK PARK, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC CGMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

MULTIOFFICE TELEPHONE SYSTEM.

Application filed. July 21, 1920, Serial No. 397,932. RenewedNovember 15, 1924,

To (IZZ ii /10m it may coacemt:

Be it ianown that I, BERNARD D. W'iL-Lis, a citizen of the United States of America, and a resident of Oak Park, Cook County, and State of Illinois, have invented certain-new and useful Improvements in Multioilice Telephone Systems, of which the following is a specification.

My invention relates in general to multiotlice telephone systems but more particulurly to such systems as comprise in one network oli'ices or exchanges of two different lcinds, the others of one kind being manual otiiccs wherein connections are completed by operators, while the other kind of ofiices are automatic o'tiices in which connections are completed by means of automatic switches, and the object or the invention is to provide new and improved circuit arrangements for handling inter-ol'iice calls between the automatic and manual ex changes.

Systems having both kinds of exchanges as above pointed out are becoming quite common and may arise either by consolidation oi existing manual and automatic systems serving the same territory, or by the process or changing over a manual system to an automatic system. Usually in the latter case only one ottice at a time is converted from manual to automatic and it tollows that during the period of transition there will nrwessarilv be both kinds of otices in operation. However this situation may arise, it is nee ary to provide suitable circuit arrangements for handling calls 'l'rom the manual oiiiccs to the automatic offices, and from the automatic o'tiices to the manual offices. The present invention is concerned only with the latter class of calls, and provides certain improvements in a system compris automatic to manual trunks which are accessible to selector switches in the automatic oiiices and terminate in plugs in front of a B operator at the manual oliice, together with call registers for registering the digits in telephone numbers called by automatic subscribers when the trunks are taken for use, and an indicating device upon which such numbers are shown to the operator one after the other as fast as she can complete the desired connections.

There may be perhaps halt a dozen call register sets assigned to each B operators position which are common to all the plug ending inter-office trunks terminating at such position, and each trunk is provided with a rotary line or trunk selecting switch which has access to the six call register sets. lVhen a call is received on any trunk the line switch associated therewith operates automatically to select an idle register set, which is thus temporarily associated with the trunk in order to register the call when it comes in. Al hough there are a plurality of register sets there is but one indicating device per position and a special object or the invention is to provide an arrangement for testing the register sets in regular or der for the purpose of switching registered calls on to the indicating device in regular order and one at a time. The means employed to accomplish this and the other improvements will be described fully herein-' after reference being had to the accompanying drawings.

In the drawings, comprising Figs. 1, f2, 3, and 4, I have shown by means of the usua1 circuit diagrams the apparatus and circuit connections thereof which is involved in a complete connection extending from the automatic substation A, Fig. 1, to a manual substation A, Fig. 2. The appara-' tus indicated in Fig. 1 is located in an automatic exchange, while the apparatus indicated in Figs. 2, 3, and 4 is located in a manual exchange. Inasmuch as the automatic switching equipment itself and the manual equipment are both well known and of the usual type. no detailed description of the mechanical features of this apparatus will be given except in so far as it is found convenient or necessary to do so in the explanation of the operation of the circuits.

Referring to Fig. 1, the substation A is one of a plurality of ordinary automatic substations terminating in the automatic exchange previously referred to, and is provided with the usual talking equipment and ringer, and also with a calling device of well known type which is indicated by the reference character S, through the medium oi' which the subscriber controls the central ofiice switches.

The line conductors 11 and 12 extend to the exchange where they terminate in the,

- of a line switch of this type is well known in the art, and its function, also well understood, is to extend its associated line when calling to an idle trunk line. In carrying out this object, a plurality of these individual line switches are given access to a group of trunk lines extending to 'first selector switches. One of the trunk lines to which the line switch C has accessis shown in the drawing as extending to the first selector '1), which is a vertical and rotary selector of the well known Strowger type. In a multi-o'ifice system of the kind herein contemplated the first selector switches are usually known as ofiice selectors and the selector D in common with a phirality of similar selectors has. access to a plm'ality of groups of trunk lines, each of which groups may extend to a different ofiice or exchange in the system. Some of these rou s of trunk lines ma extend to' automatic exchanges, while other groups may extend to manual exchanges. A trunk line in one of the latter groups is shown in the drawing, and comprises conductors 76, 77, and 78, which extend to the manual exchange in question and there terminate in V the plug ending cord circuit 0, Fig. 2. The

cord circuit 0 is one of a pluralit of. similar cord clrcults at a B op'erators position inthe manual exchange and constitutes the means whereby the trunk line shown may becon'nected by "the operator with any one of the manual lines terminating in the manual exchange. One of these lines is the line of substation A, which with its associated line equipment is shown at the right of F ig. 2. V

From the foregoing it will beunderstood that the operation of an oflice selector, such as the selector 1), in response to the calling of the first digit in the telephone number of, a line in the manual exchange, will result in extending the connection from the line of the calling automatic subscriber to an. idle plug ending cord circuit in the manualexchange. In order'to take care of the rcmaining digits in the numbers there is provided for each 13 operators position a pluralityof register sets as hereinbefore stated, each set being capable of registering all the digits in a telephone'number, with the ception of course, of the first digit, which controls theoihce selector in the automatic exchange. In Figs. and 4 I have shown one of these registersets complete. prises register switch R, Fig. 3, andregister switches R R and R 'Fig. 4. The register switch R is a simple 10 point rotary switch, having'the operating magnet 306 and It comthe release magnet 305. \Vipers 307 and 808 have a step by step movement over their associated banks of contacts under control of the operating magnet 306, and are re stored to normal position by the release ma et 305. Register switch R responds to this second digit of the called number and after it has operated transfers certain control circuits to register sWitchR which is thus prepared for operation in response to the third digit. Register switches R R, and R are similar in construction to the register switch R and are actuated'in re sponse to the calling of the third, fourth, and fifth digits in 2). called number, respectively.

It will be understood that the number of register switches in the register sets may be changed at will to provide for any desired numbering system. -As shown herein the registers R R and R are intended to be controlled responsive to digits which correspond to the line designation of the called station, while the register R is operated only in case the called station is a party line station. As shown, therefore, provisionis made for registering three regular digits and an additional party line or selective ringing digit. In case the numbers contain four regular digits an additional register switch similar to register switch R may be inserted 'betweenregister switches R and R The function of the registers will-be pointed out more fully in the detailed explanation, when it will be understood fully how the scheme may be changed to provide for any desired numbering scheme.

As before stated there is provided a plural-ity of register sets for each B operators position, and in order to show the relation between the register sets I; have shown in Fig. 3 the first register switch of the second register set. This register switch is indicated by reference character R and is exactly like the register set R The means-for switching registered calls on to the indicating device comprises what may be termed a consecution control switch, which is a rotary line switchsimila'r to the line switch C, Fig. '1, except that it has only a single Wiperand somewhat different circuits. The consecution control switch 'is indicated by reference character R, Fig. 2. The connections between the differentregister sets and the consecution control switch are made at the first register switches in each set, as shown in Figs. 2 and 3, and will be explained fully later on.

Each register set is provided with a-time controlled switch which in the case of the register set shown in Figs. 3 and 4 is indicated by the referencecharacter RfFig. 4. The switch P is similar in construction to the register switchesbut isoperatedlby the timing mechanism instead of by means of Ill) impulses corresponding to digits in the called telephone numbers. The timing mechanism, which may be common to the exchange, is indicated by the reference character 'l, and may consist of any suitable kind of clockwork controlled mechanism which is adapted to produce impulses at the rate of two per second.

in order to properly extend calls which are received at the manual exchange to the register sets each cord circuit is provided with an individual rotary'line switch hereinbefore explained, and these line switches have common access to all the register sets. The reference character C, F 3, indicates a rotary line switch which is individual to the cord circuit O, Fig. 2, and which has access to the lirst and second register sets shown, and also to the other register sets which are provided at the B operators position in which the cord circuit 0 terminates. Line switch C is of the same construction as the line switch C, Fig. 1, although the circuits are modified somewhat in order to take care of the somewhat dill'erent requirements.

'ihe indicating device by means of which called telephone numbers are shown to the l; operator is shown in Fig. 4:, where it is indicated by the reference character V. It comprises essentially a plurality of banks of switchboard lamps, there being one bank of lamps for each register switch in a register set. It will be readily understood that the lamps have the function of illuminating the digits in the called numbers and causing them to stand out so as to be readily distinguished. The digits are preferably marked in black on the reverse side of a white semi-transparent surface, and ordinarily are not very conspicuous. But when the switchboard lamp immediately behind any character or figure is lighted, such character or i'igure will stand out very clearly, and is read with great facility. in view of the tact that the connections are extremely simple they have not actually been drawn out, but will be briefly explained as iliollows: 'ihe conductors 851 and 352, etc., which terminate in the ten bank contacts associated with the wiper 308 of the first register switch, are connected, respectively, to the lamps 1, 2, etc., of the first digit group of lamps. The conductors 371, 372, etc., which come from the ten bank contacts associated with .viper 366 of the register switch R are connected, respectively, with lamps 1, 2, etc., of the second digit lamp group. In a similar manner the conductors coming from the banks of the register switches R and R are connected to the lamps of the third and fourth digit groups. It should be stated furthermore that each group of lamps is not only connected to bank contacts in a certain register switch oi the first set, but is multipled to corresponding register switches in all the other register sets at the position.

Having described in a general way the layout 01" the system herein discloseththe operation of the circuits will now be described more in detail, it being assumed for this purpose that the subscriber at substation A, Fig. 1, desires to obtain a connection with the manual subscriber at substation A, Fig. 2. It will be convenient to as sume in the first instance that the station A is a party line station, having the telephone number 23451, as this willafl'ord an opportunity for explaining the operation of the party line register switch R Afterward certain modifications having to do with the calling of other numbers will, be considered also. When the receiver is removed at substation A, a circuit is completed over the line conductors 11 and 12 for the line relay 1% of the individual line switch C. Upon energizing, the line relay completes at its armature a circuit which extends through the switching relay 13 and the stepping 111agnet 15 in series to battery, and at its armature 19 connects the test wiper 26 to the above circuit at a point midway between the switching relay and the said stepping magnet. The operation now depends upon whether the first selector trunk with which the wipers of the line switch are in connection is busy or is not busy. If this trunk line is busy the test contact 31 associated therewith will have a ground potential upon it, the switching relay 13 will be-short circuited, and the stepping magnet 15, which interrupts its own circuit, will operate as a buzzer to advance the switch wipers 27, inclusive, step by step in search of an idle trunk line. This operation will continue as long as the test wiper 26 continues to engage grounded or busy test contacts. I-lowever, we may assume that in the present case when the call is initiated the selector I) is idle, and the test contact 31 therefore is not grounded. Under these circumstances, when the line relay 1st is energized the switching relay13 is energized immediately afterwards, with the result that the line con ductors 11 and 12' are disconnected from the Windingof the line relay 14 and from.

ground, respectively, and are extended by way of armatures 16 and 18 and their working contacts, wipers 25 and 27, bank contacts and 82, and armatures and 62 and their resting contacts, to the upper and lower windings of the linerelay 50 of the selector D.

As soon as the line is extended to the selector D as above described, the line relay 50 will be energized and will close the circuit of the slow acting release relay 51. Upon energizing, the latter relay prepares the circuits of the selector for operation in its vertical movement in the usual manner, and also completes a holding circuit extending back to the line switch G as follows: ground at G working contact of armature 63 and the said armature, conductor 64, bank contact 31, test wiper 26, armature 1'7 and its Working contact, winding of the switching relay 13, and the winding of the stepping magnet 15 to battery. It is understood that the above holding-circuit is completed before the slow acting relay 14- has had time to deenergize. In addition to maintaining the switching relay energized, the holding circuit also serves to provide ground to the multiples of test contact 31 and also to the multiple test contacts in which the private normal conductor 28 terminates in the banks of the connectors whichv have access to the line of substation A,

thereby guarding the connection against in-,

two steps,ivhereupon the wipers 70-72, in: elusive, will be standing opposite the level of bank contacts in which are terminated the trunk lines extending to. the manual exchange. ,The slow acting relay 52 is energized in series with thevertical magnet, retaining the armature attracted throughout the vertical movement of the switch, and upon the closure of the vertical ofl normal springs 59 completes a circuit for, the stepping relay 53. Uponcnergizing,'relay 53 prepares a circuit for the rotary magnet 54 at its lower armature, and at its upper armature establishes a locking'circuit for itself-L At the end of the vertical movement of the vswitch the slow acting relay 52 is deenergized and closes the circuit ofthe rotary magnet, which is thereupon energized to ad Vance the wipers 70-72, inclusive, into engagement with the first set of bank contacts in the level opposite which they were raised. The rotary magnet 54 also breaks the looking circuit of the stepping relay 53 which accordingly deenergizes and breaks the'circuit of the rotary magnet, which thereupon deenergizes also and again closes its interrupter contact. The operation now depends upon whether the trunk line with which the wipers have connected is'busy or is not busy.

If this trunk line is busy the test contact associated therewith will be grounded and the stepping relay 53 will be energized over a circuit which extends by way of the test wiper 71, armature 61 and its resting contact, interrupter contact of the rotary magnet, off normal springs 59, and the winding of'the stepping relay '53 to. battery. The stepping relay will therefore again close the circnit of the rotary magnet 54 which will operate to rotate the switch wipers into ongagement with the next set of bank contacts. This operation in which. the stepping relay and the rotary magnet are alternately energized and decnergized will continue as long as the test wiper 71 continues to engage grounded or busy test contacts. In the present case it'will be assumed that the trunk line shown in the drawings is the first idle trunk line, and when therefore the test wiper 71 arrives at test contact 7 4 and the rotary magnet is deenergized, the stepping relay 53 will not again be operated, but instead the switching relay 55, which heretofore has been short-circuited, will be energized by current flowing over the following path: grounded conductor 64, winding of the switching relay 55, interrupter contact of the rotary magnet 54,. oifnormal springs 59,

and the winding of the stepping relay 53.

to battery. Owing to the high resistance of the switching relay 55, stepping relay 53 is not operated. Upon energizing, relay 55 disconnects the incoming line conductors from the windingsof the line relay 50 and extends them by way of armatures 60 and 62 and their working contacts, wipers 70 and 72, bank contacts 73 and 75, trunk conductors 76 and 78, left hand windings'of the repeating coil-in the cord circuit 0,, Fig, 2, and normally closed contacts of the reversing relay 204 to the upper and lower windingsof the line relay 203 in the cord circuit.

When the calling l-ine'is extended to the line relay 203 as aboie explained the said line relay is operated, and completes parallel. energizing circuits for the slow acting relays 201 and 202. These relays are therefore energized at the same time and may be considered as one relay, but in view of the large number of contact springs it is advisable in practice to use two, relays with the contact springs dividedf between them. Relay 20]. prepares a circuit for the reversing relay 204 at its armature 219, and at its armature 245 connects ground to the release trunk conductor 7 7. By the latter operation the trunk line is made busy and a holding circuit is established in the usual manner for maintaining the switching relays 55 and 13 energized during the call. Relay 201 also closes a circuit for relay 211 at armature 246.

Upon energizing, relay 211 prepares a circuit for the trunk or call signal lamp L at armature 239.

Relay 202, which is energized in parallel with relay 201, as before stated, prepares at its armature 217 an operating circuit for the register switches of whichever setislater selected; and its armature 218 closes an operating circuit for the individual line switch C which extends as follows: ground at G, resting contact of armature 236 and the said armature, working contact of armature 2'18 and the said amature, conductor 2-12, armature 256 and its resting contact, and the winding of the line relay 251 to battery. Upon the completion of the above circuit the line relay 251 is energized and at itsarmature 258 closes a circuit for the switching relay 250 in series with the stepping magnet 252. At the same time, at its armature 257, the line relay connects the test wiper 262 with the above mentioned circuit at a point midway between the switching relay and the said stepping magnet, whereupon a trunk selecting operation will take place similar to that which has already been described in the case of the individual line switch G. For the sake of simplicity it will be assumed that the wipers of the line switch C are already in connection with the bank contact set associated with the first register set, as shown in the drawing, and it will be assumed furthermore that this register set is idle. It will be evident therefore that test contact 266 will not be grounded, and no rotation of the line switch 0' will take place. The switching relay 250 is at once energized and establishes a locking circuit for itself at its armature 255. Relay 250 also performs a number of other circuit changes which may be mentioned briefly as follows: At armature 25% ground is connected to the test wiper 262 for the purpose of rendering the multiples of test contact 266 busy in the banks of the other rotary line switches. At armatures 253 and 265) conductors 24. 3 and 241 are extended through to wipers 260 and 263, respectively, and at armature 256 the conductor 242 is disconnected from the winding of the line relay 2:31 and is extended by way of the working contact of armature 256, wiper 261, bank contact 265, and the winding of relay 300 of the register switch R to battery. Upon the closure of its circuit relay 300 is operated and at its armature 309 disconnects ground from the minmon conductor 450, at its armature 311 disconnects ground from a releasinn: circuit extending over conductor 330 which will he described later on, and at arinalure 310 closes an operating or control .cuit for the register switch R which will shortly he traced. in full.-

The apparatus is now ready for the reception of the series of impulses correspondi i to the first digit in the local number of t called line in the manual exchange. lt is understood. of course, that the first digit i the telephone nun'iber which operated the D at the automatic exchange has to wit' the office selection only and does not appear in the multiple at, the B opera tors position. \Vhen the dial of the calling device S is operated in accordance with the next digit therefore another series of interruptions, three in this case, will be produced in the line circuit and will bring about a like series of deenergizations of the line relay 203 in the cord circuit 0. At each de- 'energization the said relay transmits an impulse of current to the stepping magnet 306 of the register switch R over the follow duced by the calling device S, the stepping magnet 306 will receive three impulses of current and the wipers 307 and 308 will be rotated three steps and will come to rest in engagement with the third contacts in their respective banks. The operation of wiper 308 produces no result at this time, but wiper 307 when it'moves out of normal position closes a circuit for the relay 301 which upon energizing changes the operating circuit so that it extends by way of the armature 310 and its working contact, work ing contact of armature 312 and the said armature, armature 315 and its working contact (slow acting relay 302 being now energized), winding of relay 302, and the winding of the stepping magnet 306 to battery. Relay 301 also prepares a circuit for the release magnet 305 at armature 313, and at armature 314 connects ground to test con tact 266 and its multiples in the banks of the other individual line switches. The latter operation is for the purpose of maintaining these test contactsgrounded during the releasing operation in the register set, as will be pointed out more fully hereafter. The slow acting relay 302, which is energized in series with stepping magnet 306 and which remains in operated position while operating impulses are being received, deenergizes after the operation of the register switch R! is completed and at itsarmature 315 extends the operating circuit to the next register switch R as follows: armature 315 and its resting contact, conductor 329, contact springs controlled by armature 368, winding of the slow acting relay 361, and the winding of the stepping magnet 364 to battery. The apparatus is now ready to receive the next series of impulses. When the calling device is operated again, this time in accordance with the digit 4,2 series of four interruptions is produced in the circuitof the line relay 203, with the result that four impulses of current are transmitted to the stepping magnet 364 of register switch R In response to these impulses the stepping magnet 364 is operated to rotate the wipers 365 and 366 four steps, and the wipers are brought to rest in engagement with the fourth contacts in their respective banks. When the wiper 365- leaves its normal position a circuit is completed for relay 360 which, upon energizing, prepares a circuit for the release magnet 363 at its armature 367 and at its armature 368 prepares the operatingjci-rcuit for transfer to the next register switch by the slow acting relay 361. This latter relay is energized in series with the stepping magnet 364 while the said magnet is being operated and deenergizes at the end of the rotary movement as was described in the case of the slow acting relay 302 of register switch R The slow acting relay 361 having deenergized, the operating circuit is extended to the register switch R as follows: conductor 329, working contact of armature 363and the saidarmature, armature 369 and its resting contact, conductor 329, contact springs controlled by armature 387, winding of the slow acting relay 381, and the winding of the stepping magnet 384 to battery.

The next digit to he called is the last digit which is included in the line. designation of the line of substation A which appears in the multiple at the B operators position, the final digit being a party line digit having to do with the selective ringing, as before stated. The calling subscriber may now call the digit 5 with the result that five operating impulses are transmitted to the stepping magnet 384 of the register switch By the operation of the stepping magnet .384, wipers 397 and 398 are rotated step by step until they come to rest in engagement with the fifth contacts in their respective banks. When the wiper 397 leaves its normal position a circuit is completed for the relay 380, which, upon energizing, changes the operating circuit at its armature 387, the same as was done in the case of the tworegister switches previously operated, prepares a circuitfor the release magnet 383 at its armature 386, and at its armature 385 prepares a circuit for the timing switch Pf The slow acting relay 381 is energized in series with the stepping magnet 384, remaining in operated position while impulses are being received, and at the end of the operation of the register switch R is deenergized, whereby the operating circuit is transferred to the register switch'R as follows: conductor 329*, working contact of. armature 387 and the said armature armature 3'88 and its resting contact, conductor 5529*, contact springs controlled by armature 408, winding of the slow acting relay 401, and the stepping magnet 404 of the register switch R 'to battery.

Register R is now ready for operation in response to the calling of the party line selecting digit.

When the slow acting relay 381 deenergizes at the end of the operation of the register switch B it closes at its armature 389 a circuit for the stepping magnet 433 of the timing switch P as follows: grounded conductor 399, working contact of armature 385 and the said armature, armature 389 and its resting contact, armature 410 and its resting contact, armature 436 and its resting contact, and the winding of the stepping magnet 433 to the common conductor 435. Since the common conductor 435 is connected to battery at half second intervals by the time mechanism T, the stepping magnet 433 immediately begins operating to advance the wipers 437 and 438 step by step over their associated banks of contacts. As soon as wiper 4'37 leaves its normal position it completed a circuit for the relay 430 which upon energizing prepares a circuit for the release magnet 432.

The calling subscriber may now operate his calling device in accordance with the digit 1 which is the last digit to be called.v By this, operation a. single impulse of current is transmitted through the stepping magnet 404, of the register switch R over a circuit previously traced, and the said magnet is operated to advance the wipers 41.7 and 418 into engagement with the first contacts in their respective banks. When the wiper 41.7 leavesits normal position a circuit is completed for relay 402 which upon energizing prepares a circuit for release magnet 403 at its armature 406, changes the operating circuit in the usual manner at its armature 408, prepares a circuit at its armature 409 which is closed later by armature 407 of relay 401 andwhich will be described hereinafter, and at its armature 410 breaks the circuit of the stepping magnet 433 of the timing switch P. By the latter operation the movement of the timing switch is stopped, and it may be ALMA.

mentioned here that its operation in. the v present case, where the party line substation A is being called, is of no utility. The function of this switch. will be pointed out later on. The slow acting relay 401 is energized in series with the steppingmagnet 404 6 off the register switch It and when it deenergizes at the end of the rotary moven'ient of said switch a circuit closed at its armature 407 which extends as follows: grounded conductor 419, working contact of armature 409 and the said armature, armature 407 and its resting contact, conductor 323, and the winding of the, relay 303 to battery. A branch of the abovecircuit may also be traced by way of conductor 340, register set pilot lamp L at the operators position, and the common relay 504: to battery. When the above traced circuit is completed the pilot lamp L is illuminated to indicate that the register set associated therewith has a connection set up on it, and the relays 303 and st are energized.

lVe now come to the operation of the co'nsecution control switch R and before proceeding it will be advisable to describe this switch and the wiring of its single con tact bank a little more fully. As hereinbelore stated, the switch R is similar in construction to the rotary line switch C, Fig. 1. 'ie'terence characters 501, 502, and 503 indicate the usual line and switching relays and the stepping magnet. The single wiper 505 moves in a forward direction only and is not released when the switch becomes idle but remains standing in its advanced position. Although the switch may have any desired number of contacts in its bank, as usually constructed it has twentylire, and these contacts are wired as follows: Conductor 321 which may be termed a testcondiutor extends from armature 316 01" relay 303 to the first contact in the bank of switch R. In a similar manner conductor 322 extends from armature 316 of relay 303 to the second contact. Relays 303 and 303 are located, respectively, in the first register switches of the first and second register sets, as is understood. The ren'iaining test conductors, conductors 323, 321-, and 325, ettend from corresponding relays in the first register iwitches of the third, fourth, li't'th and sixth register sets, respectively, to the third, fourth, fifth, and sixth contacts. These connections are clearly indicated in the drawing although the last :t'our conductors are not shown complre because only the first and second regi er sets are shown. This tills up the first sir; l auk contacts. The next six are connected in multiple with the lirst six, and the multiple is continued until all the bank contacts are wired. It there is an. odd number let't it makes no dilierence as they are sim ply multiplcd in regular order as far as they go.

l r'ith the foregoing explanation in mind the }')(l'2ltl011$; may he proceeded with. When relay 303 is energized by the grounding of conductor 323 as hereinbetore explained, the said relay removes ground from the test conductor 321 and thus removes the ground potential. normally existing on the tirst contact in the bank of the consecution control switch E. The common relay 501 is also energized by the grounding of conductor and connects up the wiper 505 by n cans of its armature 506, while at armature 507 a circuit is closed for the line relay 501. Upon energizing, the line relay closes at its armature 511 a circuit which extends through the switching relay 502 r l the stepping magnet- 503 in series, and

by means of its armature 510 the said line relay connects the wiper 505, which is in the nature of a test wiper, to the above circuit at'a point midway between the said switching relay and magnet. The latter operation provides for advancing the wiper 505 in case the contact with which it is in engagement is grounded, but it will be assumed in the present case that the wiper is standing on the first contact in its bank, as shown in the drawing, and since ground has been removed from this contact by the energization of relay 303, no rotation of the switch will take place. Instead, the switching 502, which is'ot high resistance, is at once energized in series with the'stepping magnet 503, the latter remaining inoperative, and breaks the circuit of the line relay at armature 508. The line relay is slow acting, however, and before it has time to fall back relay 304; is energized over the following circuit which is completed at the same time that the line relay circuit is broken: from ground at armature 511 of the line relay by way of the working contact of armature 509 and the said armature, working contact of armature 506 and the said armature, wiper 505 and bank contact engaged thereby, conductor 321, armature- 316 and its working contact, and the wineing of relay 3041- to battery. Upon energizing, relay 304 looks itself to the grounded conductor 328 by means of its armature 317. This operation connects conductors and 321 together and a circuit is thus completed for supplying ground to the switching rclay 502 of the consecut-ion control switch in order to maintain this relay energized after the line relay 501 has fallen back. Relays 303 and 304 are now both energized, and the switch R is standing in operated position (switching relay energized) with its wiper 1n engagen'ient with the bank contact corresponding to the first register set. 0thor calls may be registered on the other reg:- ister sets at any time now and as soon as registration is complete the lamps L L", c-tc., corresponding to the register sets in use will be lighted, but this has no ell'ect on the oonsecutimi control switch R. This switch makes no further n'ioven'ient until the, call on the first register set has been dis posed of.

Relay 30 1: is the relay which switches over the registered call to the indi \ating lamps, and the manner in which this is done will now be explained, it being recollected that the wipers of register sets 11 -1 inclusive, are now resting upon the third, fourth, fifth and first contacts in their respective banks. When the armature 319 of relay 304 is attracted ground G is connected by way of conductor 3418, the common conducting strip in the bank of register switch R with which "grounding a common strip in the bank of its associated switch, as shown in the draw.- ing, and it willbe clear therefore that when these relays are energized, the wipers being operated as previously stated, conductors 374, and 411 will be grounded, 'These last three conductors extend to the #4 lampof the second group, the #5 lamp of the third group, and the B lamp (black) ,of the fourth group. The other side of all the lamps is connected to battery as shown in the drawing, and the lamps mentioned are accordingly illuminatedand indicate to the operator the number 345 black.

VlVhen the relay 382 of the register switch R" is energized it closes a circuit for the trunk or call signal L in the cord circuit 0 over the following path; ground at G armature 396 and its working contact, conductor 331, bank contact 267, Wiper 263, working contact of armature 269 and the said armature, conductor 241, resting contact of armature 234 and the said armature,

working contact of armature 239 and the said armature, and the lamp L to battery. The lamp L, which is individual to the cord circuit 0, is therefore lighted simultaneously with the lamps in the indicating device V and enables the operator to know which one of her cord circuits is being used by the auto matic subscriber whose wanted number is at this particular time being shown on the indicating device, llaving observed the numher 345 black, and knowing by the lighting of the lamp If that the cord circuit 0 is the one in use, the operator will test the multiple jack oi? line 345 with the tip of the plug in the usual manner to ascertain whether or not the line is busy. In case the line is busy the plug will be inserted in a busy jack of well known form and function, in order to give the calling subscriber a busy signal.

. The busy machine associated with the busy jacks at the 1) board is preferably of the same type and giving the same kind of a liuisy signal the busy machine in the automatic exchange, so that the calling subscribers will get uniform busy signals in all cases, Assuming, however, that the line of substation A is found to be idle, then the operator will press the black ringing button, indicated by reference character B in the drawing, and will insert the plug of cord circuit 0 in the multiple jack #345,;this

being the jack J in which is terminated the line of substation A. It may be mentioned at this time that each cord circuit is prothe condenser to conductor 243, and closes a,

vided with the usual black, white, green and red selective ringing buttons as shown, which correspond to the 16, 33, 50, and 66 cycle ringing frequencies, respectively. The ringing keys are of the self locking type and when anykey is depressed it remains locked in depressed position until another key'is operated.

When the plug is inserted in the jack J a circuit is completed for the relay 208 in the cord circuit 0 as follows: ground at G, windingof the cut olf relay230, sleeve of the jack J, sleeve of the plug, and winding of relay 208 to the junction point 231, where the circuit divides, one branch extending by way of the supervisory lamp L to battery,

(and the other branch extending byway of armature 220 and its working contact, work ing contact of armature 228 and the said arn'aature (closed as soon as relay 208 energizes), armature 225 and its resting contact, contact springs controlledby armature 226, and the winding of relay 205 to battery. By current flow over the above circuit, relays 2130 and 208 are energized in series, the former relay being effective to clear the line of substation A of its normal battery and ground connections, and the relay 208 being efl'ective to disconnect the operators telephone set and close the upper talking strand of the cord circuit at armature 227. The lampL is lighted when the circuit isfirst closed by the insertion of the plug, but as soon as the branch circuit through relay 205 is closed by the energization of relay 208' the lamp is extinguished by the shunting oi the current through this relay, which is of relatively low resistance. Relay 205 is the ringing relay, and is energized at this time to close at its armatures 223 and 224 the usual automatic ringing or signalling circuit which, since the black ringing key has been depressed, 'will include the 16 cycle generator. The ringer at substation A is tuned to the 16 cycle frequency and responds to signal the called subscriber.

The required connection has now been established and the desired party is being signailed automatically in the usual way; Be fore proceeding with the operations which take. place when the called subscriber answers it will be well to consider the release of the register switches which takes place as soon as the connection established. by the insertion of the plug in the jack of the called line, \Vhen the plug of cord circuit 0 is inserted in jack J a branch path may be traced from the sleeve of the plug by way of conductor 232 and the winding of relay 200 to battery. Relay 200 is therefore enertendsfrom trunk conductor 76 by way of circuit for relay210 at its armature 21 1. Upon energizing, relay opens the circuit of lamp if a armature closes a locking circurt it m: at armature 235, and at its :50 opens the holding circuits 01 50 and 300 oi the individual line and the register switch il respectively. Upon dc icing, relay 250 disconnects the wipers or c e line switch C 19 a 1 the switch is thus i ed to normal condition. li'hen relay 300 deenergizes ground G is connected to conductor with the result that the previously prepared circuits for the release magnets 363, 2 0 and 432 Oil register switches PG, in and timing switch 1 respectively, are completed and the said switches are restored to normal position. Nhen the reach normal position relays 301,

4:02, and e are decncrgized and se :a net circuits of the several 11'0 broken. Relay 301 also disconound from the test contact 266 and their y rendering the No. 1 srer sec accevs le to other li hen register switches are released as above and is removed from conducand relays 303 and 30d, and b pr 0 r: ,a tuner 111$; 1%}; -12 O Lire cOIlSQLllbiCil 011- trol switch ll all deenergized. The register pilot lamp L is extinguished at lhe same time and it there is no other call waiting the common relay will fall back. in case another call is waiting 50% remains pulled up of course, but :iurther explanation ot the operations which then taice pla will 3e deferred until rel a y turning new to the established connecwhiie the called subscriber is being lied automatically as before explained, ing subscriber in the automatic en;- is given the well known rin ng d; induction by means of the circuit through the high resistance 233 which bridges the open contact in the upper strand circuit at armature 228 of the clay 205. This resistance permits inging current to leak bark in the ii n of the calling subscriber to give lible signal each time ringing current plied the called line. ant he is there 'see that the ringing operation is ur. so called ring :n is standard praitice in auto:

ms and by provii'ling for the same in the B operators cord circuits l seirm operating conditions, To pro ring out off relay 200 is included circuit, but does not enerlong the receiver at substation A rem us on the 1 When T e called subcurrent flow and opens the back contact of its armature 225, thereby including relay 207 in the circuit of the relay 205. Relay 20? therefore is at once energized and upon attracting its armature 226 shortcircuits relay 205 and locks itself in the circuit over the sleeve of the cord. In other words, relay 207 is substituted for relay 205, and it may be mentioned that relay 207 is of the same resistance as relay 205 and the supervisory lamp L therefore remains shunted out. W hen relay 205 deenergizes the ringing circuit is broken and the upper and lower talking strands of the cord circuit are connected, whereupon the talking circuit vill have been completely established. The calling subscriber is supplied with talking battery through the windings of line relay 203 and the called subscriber is supplied with talking battery through the right hand windings of the repeating coil at the cord circuit C. Relay 209 is included in the latter circuit and is operated by current flow through the transmitter at substation A to attract its armature 222 and close the circuit oi' the reversing relay 20 1. By the op eration of the reversing relay 204 the trunk conductors 76 and '78 are reversed as regards their connections with the windings of the line relay 203 and the direction of current flow in the calling line is therefore reversed. This operation may be used for operating a meter or supervisory apparatus and is provided for according to standard practice, although it is of no utility in the particular circuit shown.

The required connection having been established, the subscribers may now converse as desired. lVhen the conversation'is fin-v ished both subscribers will hang up their receivers. l Vhen the receiver is replaced at substation A the circuit of the line relay 203 at the cord circuit O is broken and the said relay is deenergized resulting in the dcenergization of slow acting relays 201 and 202 also. Relay 202 by retracting its armature 220 opens the shunt path around the super visory lamp L which extends through the relay 207 to battery, and thereby causes the lamp L to be lighted to give the operator a disconnect signal. lielay 201, upon deenergizing, removes ground from the release trunk conductor 7'7, whereupon relays and 13 in the selector D and line switch C. respectively, are deenergized. Relay 55 closes the circuit of the release magnet 57 and the selector D is restored to normal in the usual manner. Relay 13 disconnects the wipers of the line switch C and again connects up the line relay in readiness for another call. Relay 201 also breaks the circuit oi the slow acting relay 211, and since relay 200 is still energized, when relay 211 falls back it connects ground to therelease trunk conductor 2''? again by means of armathis contact is connected with. the registered t'ure 238; This renders the trunk line busy so that no more calls can come in while the plug is in the jack.

" The automatic switches have now been released, a disconnect signal has been given to the operator, and the trunk line in use has been made busy pending the pulling down of the connection at the B board. When the operator observes the lighted supervisory lamp L she will remove the plug of cord ci rcuit from the jack and relays 230 and eoswrn be deenergized, and the lamp L will be extinguished. Also the relay 200 will be deenergized' and ground provided for flashing the lamp L to call her 7 attention to the error. hen the plug is withdrawn relay 200 is deenergized as explained but sincethe connection has not yetbeen released by the calling subscriber relay 201 will be in energized position and relay 210 will remain locked up. Under these conditions a circuit for lamp L will be closed atarmatures 237 and 215 of the relays mentioned, This circuit includes the interrupter I and the lam will be flashed to attract the attention ottheoperator. It the operator remembersthe jack from which the plug was withdrawn she can replug 1mniediately; otherwise she will plug into a special jack (not shown) "which connects with her head set so that she'ean talk to the calling-party and ask him what number he was disconnected from.

It will be convenient now to revertto the consecution'control switch R and consider its operation a little more in detail. It will be understoodof course from what has been said already that when a call is received and is registered on a certain register setground is removed from the test contact'corresponding to such register set in the bank of the switch R, and at the same time the proper pilotlainp is lighted in series with the comnionrelay 504.. It the switch P is idle, that is,i't no call is switched on to the indicating lan'ips. the switch at once operates to advance its wiper into eng'agi rment with the non-grounded test contact and, as soon as call isswitched over. But it a second call is received and registered while a prior call which'has been switched on to the indicating'lamps is waiting undisposed of, the call last registered will have to wait. This does not'occ'ur veryotten, for the operator can plug up connections very rapidly; never theless it sometimes happens thattwo or three calls or perhaps even more are received and registered nearly at the same time and registered calls may thus accumulate faster than the operator can handle them. This as the operator can plug up the connections.

The consecu'tion' control switch R itakes care oi this. lVith one or more registered calls waiting the common relay 504 is maintained continuously energized, and as soon as a 'con- I nection is completed by the operator, the register set on whichthe call was registered being then released, relay 5020f switch R is deenergized as previously explained and the line relay 501 will at once pull up. By

the operationot' the line relay the switch R? is caused to advance its wiper into engage ment with the test contact which is assoeiated with the next register set upon which a call is waiting, distingijiished by the removal of ground at an armature such as 316 or 316, and this call is then switched on to the indicating lamps. As soon as the call is handled the register set is released, relay 502 is deenergized, and the switch R moves its wiper ahead to test for the next waiting call, and so on until all the accumulated calls have been taken care of.

I will now explain certain details of the system which it was not convenient to go into fully before; and the first thing which will be considered is the function of the timing switch P, Fig. 4. The necessity of providing one or these switches tor each register set is occasionedby the fact that the system herein contemplated include-s both party lines-and straight lines, the party lines having one more digit in their-telephone numbers than do the private or straight lines. It is understood that means must be provided in "each register set for switching over onto the indicating lamps as soon as the registering of a telephone number is completed. The registering of a telephone number is completed when the final digit is called, and in the case of party line numbers which have :1 maximum number of digits, the problem is a simple one, it being only necessary to provide means in the last registerswitch, register switch R for example, for closing the circuit of the relay which places the reg ister set in condition to be switched over. This relay is the relay 303 in register set No. 1, and it has already been explained fully how the circuit of this relay'is closed as soonas the register switch 11* has finished 'closes the circuit of the relay 303.

operating. But when a private line is being called the proposition is not so simple. The telephone number oi a line of this kind will have one less digit than do the party line telephone numbers and when the number is registered therefore the register switch P." will never be operated. It will not do ordinarily to have the register switch R close the circuit of relay 303 directly. be cause in case. a party line number is called instead of a private line number this relaywould be operated prematurely. In order to take care of his din 'ulty we provide the timing switcl'i which is started operating as soon as the re Jter switch R has finished its operation. as previously explained. and

which atter a certain definite time interval- This time interval is calculated in accordance with the average length of time reouired to call the final digit in a telephone number, and may be of about tour seconds duration, or less. To explain the operation a little more tullv let it be assumed that some telephone number is being registered and that the register switch R has just completed its operation. The timing switch P will now be set in motion by the closure of the circuit oi its stepping magnet in a manner which was already described, and will ad vance its wipers step by step over their associated haul: contacts. lit the number being called is a partv line number the calling subscriber will immediately call the final digit in the telephone number. which is registered on the r 'ster switch R and the operation of the timing switch P will be stopped as soon as relay 4-02 energizes, the circuit of stepping magnet 4 33 being opened at armature 410. Suppose now that a private line number is being registered. in which case the digit which operates register switch R will be the final digit. The timing switch continues its ope ration in such case without interference and after an interval ,ot four seconds the wiper 438 will place a ground on conductor 430. The circuit of relay 431 is therebv closed. which relay operates to open the circu it ot the stepping magnet 433 at its armature 436. At the same time a circuit is completed for relay 303 as follows: grounded conductor 439, resting contact of iirniature 442 and the said armature restlug contact oi armature 409 and the said arn'iature. armature 4-07 and its resting con tact conductor 323. and the winding of relay 303 to battery. By the closure of the above circuit relay 303 is energized, and in case the indicating lamps are not in use relay 304- will be ene gized also by the operation ot the cousecution control switch to switch the call over onto the lamps. The operations 1" i n w on are the as have been prey described.

An alternative method of switchin on which may be employed at the option or the B operator during day time busy periods will. now be briefly explained. it such times the number of calls for party line stationsis at a minimum because as a general rule all the business houses will have individual private lines; and it is found that the service may be speeded up greatly without causing any particular trouble by cutting out the timing switches, which it is understood are provided solely for the benefit o't' those parties who are calling party line numbers. In order to accomplish this the B operator will operate key K which places a ground potential upon conductor 332 and operates the relay 4&1. There is a similar relay operated over the same conductor for each of the other register sets at the position; Relay 441 being in operated position, let it be assumed that a call is received and is registered on the #1 register set. As soon as the register switch R finishes its operation. a circuit for relay 303 is completed as follows: grounded conductor 399, working contact of armature 335 and the said armature armature 389 and its resting contact, armature 410 and its resting contact working contact of armature 4A2 and the said arma ture, resting contact of armature 409 and the said armature, armature 407 and its resting contact, conductor 328, and the winding of relay 303 to battery. Relay 303 is theretore energized as soon as the register switch R completes its operation, and the call may be switched over immediately without waiting for another digit to be called, or for the time mechanism to operate. Should it happen that a party line number is being called, no great harm is done by the switching over onto the indicator lamps, should this have taken place. The calling subscriber will generally start to call the final digit before the operator has had time to insert the plug into the supposed number of the called line, or perhaps even before she has fixed the number in her mind, and as soon as the register switch R starts operating the circuit of relay 303 will be broken (at armature 407 of relay 401) and the lamps will be extinguished. If another call is waiting it will be switched onto the lamps at once, while if no call is waiting the call under consideration will be again switched onto the lamps as soon as the register switch R has been operated. Since the lamps ordinarily are extinguished only when the plug is inserted in the jack oi the called line. it the lamps go out automatically before she has plugged in, the operator will know that another digit is being called and that she will have to wait for the complete number to be flashed on before she can handle the connection.

There is one other condition whit/- may be discussed before concluding. This ,is the case wherea call is received at the operators ,osition when all the register sets are busy. e common conductor 450 is normally 7 rounded at each of the :IYB lSiQl' sets, the

round connection being shown in the case of the No. 1 register set at the resting contact of armature 3090f relay 300,.and at the corresponding armature in the case of the No. 2 registerset. If all register sets -are busyit will be evident that all of these ground connections in the different zrcgistei' sets willbe opened and :the common conductor 450 will be clear of ground. normally short circui'ted-relay 453 is thereupon energized and disconnects ground from 'the test contacts of a special group of busy signalling contact sets. The trunk line switches, such astlie line switch C, have twent efive sets of contacts in their banks and t e six register sets :may be inultipleifl three. times through the banks. .This takes up eighteen sets of contacts and the remain ingseven are wired like the first three sets shown ust below relay 4 53. The fourth set shown s of course one of the other eighteen.

The top contact inea'chof theex'tra jseven contact sets is wired to the busy signalling machine and the test contacts of all such sets are normally, grounded so that the line switches will not ordinarily stop on then'i.

7 But if all the register sets are busy when a call is received over a trunk line, the trunk terminating in cord circuit 0 for example, the line switch C will not be able tojfinld an idle register set but will stop on one of the busy signalling contact sets, these contact sets being now accessible by reason pf the energization of relay 453. A circuit will then be completed from the busy signalling machine by way of the upper contact of the set connected with and the wiper 260 in en-' gagement therewith, working contact of armature 253 and the said armature, conductor 243, armature 217 and its working contact, armature 213 and its resting contact, and thecondenser totheuppe'r trunk conductor 76. The completion of this rir' cuit givesthe calling subscriber an audible busy signal which indicates to him that for the time being the desired connection can not beobtaincd and he will replace his receiver.

troller for switching registered calls on to register sets accessible to calling automaticsubscribers for registering called telephone numbers, an indicating dGVlCB'COlDIIlOIl tosaid register sets for indicating registered calls to an operator, a consecution controller COlIi-* prising an automatic step by step switch adapted to test saidregi ster sets in 'a definite predeterminedorder for the purpose of 10- catin registered calls, and means .for'

switc' ing SUOGGSSiVely located calls on to said ndicating device one at a time. 7

3. In a telephone system, a plurality of register sets accessible to calling automatic subscribers for registering called telephone numbers, an indicating device common to said register sets for indicating registered calls to an operator, a 'consecution controller comprising an automatic step bystep switch, means for causing said switch to test said register sets in a definite orderwhen a callis registered in order to locate the call, means for stopping the testing operation and for switcliingthe call on to said indicating device, means whereby the operator can complete the required connection, and means for then causing said switch to continue the testing of said register sets to locate an other registered call. a

4. In a telephone system, an automatic exchange and a manual exchange, means for connecting a calling subscriber in the first exchange with a called subscriber in the second, said means comprising an interofiice trunk line accessible toswitches in the automatic exchange and terminating in a plug ending cord circuit in the manual exchange, a lampsignal in said cord circuit adapted to be lighted over the sleeve of the plug, means for maintaining a shunt around said lamp to prevent it from lighting, means for opening the shunt to cause saidv lamp to give a [steady disconnect signal when the calling subscriber hangs up his receiver, and means for flashing said lamp when the operator pulls down the connection before the calling subscriber hangs up. 7

,5. In a telephone system, a plurality of re ister sets accessible to callin automatic subscribers and responsive to t e subscribers calling devices for registering called telephone numbers, an indicating device common to said register sets for indicating registered calls to an operator, and a consecution controller for switching registered calls, on to said indicating device one at a time, said controller comprising a step by step. switch adapted to test said register sets in a definite predetermined order.

6. In a telephone system, a pluralityof register sets accessible to calling automatic subscribers for registering called telephone numbers, an indicating device common to said register sets for indicating registered calls to an operator, and a consecution controller for switching simultaneously registered calls on to said indicating device one at a time, said controller comprising a step by step switch adapted to test said register s ts in a definite predetermined order.

7. in a telephone system, automatic and manual exchanges, an interconnecting trunk line, a plurality of register sets accessible to calling automatic subscribers over said trunl: line for registering called telephone Hl'iIHiJClS, an indicating device common to said register sets for indicating registered ells to an operator, consecution controller comprising an iutomatic step by step switch adapted to test said register sets in a definite predetermined order for the purpose of locating registered calls, and means for switching successively located calls on to said in dicating device one at a time.

8. In a telephone system, a plurality of register sets accessible to calling automatic subscribers for registering called telephone numbers, an indicating device common to said register sets for indicating registered calls to an operator, a consecution controller comprising an automatic step by step switch, means for causing said switch to test said register sets in a definite order when a call is registered in order to locate the call, means for stopping the testing operation and for switching the call on to said call indicatin device, means for delaying the indication of subsequently registered calls, means whereby the operator can complete the connection corresponding to the indicated call, and means for then causing said switch to continue the testing of said register sets to locate another registered call.

9. In a telephone system, a group of circuits, automatic hunting switches by means of which calling lines are given access to said circuits, said circuits terminating in sets of contacts in the banks of said switches, additional sets of contacts in said banks, each such additional set including a test contact and a line contact, a busy signalling current source associated with said line contacts, means normally effective to maintain a busy potential on said test contacts to prevent said switches from seizing any of said additional sets of contacts, and means responsive in case all said circuits become busy for removing the busy potential from said test contacts.

10. In a telephone system, means including a selector switch and a plug ending trunk circuit for connecting a calling and a called line, a test contact for said trunk circuit in the bank of said selector, a relay in said trunk circuit controlled over the calling line for placing a busy potential on said test contact, a slow acting relay having circuit completed by said first relay, a third relay energized as long as the plug oi said trunk circuit remains inserted in the' jack of the called line, and a circuit for placing a busy potential on said test contact after the selector is released and while said plug remains in said jack, said last circuit including serially related contacts on the said second and third relays.

Signed by me at Chicago, Cook County, Illinois, this 16th day of July, 1920.

BERNARD D. WILLIS.

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