US2359625A

US2359625A - Telephone system

Info

Publication number: US2359625A
Application number: US472711A
Authority: US
Inventors: Thomas F Crocker
Original assignee: Automatic Electric Laboratories Inc
Current assignee: Automatic Electric Laboratories Inc
Priority date: 1943-01-18
Filing date: 1943-01-18
Publication date: 1944-10-03
Anticipated expiration: 1961-10-03

Description

. Filed Jan. 18, 1943 10 Sheets-Sheet 2 0 ENTRAL OFFICE 2! INTERRUPTER 501.0 SUPY as GONTROL 'swsacnsoano 200 1.254. L253 p I c292\. -0291 24| Y I 3RD LINK HOLD N J "Mai 40 N N NI 1' Hw TELEPHONE IST. TRUNK SET IST. LINK TALK K220 205 HOLD SUP'Y L53 25| '7 3 3 w N )N 23| I lsr. LINK HOLD 2321 K230 M5 {E213 2|4 FIRST Ill I OPERATOR BOOSTER i 09 POSITION BATTERY RING \2' 2m 3 '"2l6 KLQIL Q: ISI TK. T'TK ANS. usy

1.2m L255 DIAL 20g v 2o1- INVENTOR. moms F. caocxsn ATTOR NEYS TELEPHONE SYSTEM 1 Filed Jan. 18, 1945 10 sheets-sheet 4 INVEN TOR. THOMAS F. OROOKER ATTORNEYS v Oct. 3, 1944. T, c oc' 2,359,625:

TELEPHONE SYSTEM Filed Jan. 18, 1945 1O Sheets-Sheet 5 THIRD TOLL LIINK 503 T 3 FIG. 5 R53l 592 0T M5|7 C5235 5 EEZ I] TOLL SELECTOR o J 35a: 0/ 1 532 I 7 MW 584 x1- VERT A 55| if533 54| 552 V x 1 P 591" 30! $519 I 542 R550 56:

-R58O RING SLAVE 5l3 C304 R318 MECH 5l0 C98! C982 L983 L984 L985 INVENTOR. THOMAS F. OROGKER ATTORNEYS Oct. 3, 1944. CROCKER 2,359,625

TELEPHONE SYSTEM Filed Jan. 18, 1945 10 Sheets-Sheet 7 v 07623 11: gm

C763} 71o g 1 ST. com. f TRUNK ml 4 0 C764 721 i 0765 142 4; 75: 1 o o FINDER REMOTE SWITCH OFFICE 120 st 73|1 R740 SUPY. comp cvos/ gm. I USY INVENTOR.

THOMAS F. CROGKER I W, -7,M M

ATTORNEYS Oct. 3, 1944. CROCKER 2,359,625

TELEPHONE SYSTEM INVENTOR. THOMAS F. CROOKER ATTORNEYS Oct. 3, 1944.

T. F. CRTOCKER 2,359,625

I TELEPHONE SYSTEM Filed Jan. 18, 1943 10 Sheets-Sheet 9 SW. ST

TO 2ND. CONT 963 x' TRK. EQPT.

i IST CONTROL TRUNK EQUIPMENT 90l INVENTOR.

THOMAS F. GROOKER ATTOR NEYS Patented Oct. 3, 1944 TELEPHONE SYSTEM Thomas F. Crocker, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., a corporation .0! Delaware Application January 18 1943, Serial No. 412,711

27 (llailrls. (Cl. 179-27) The present invention relates to telephone systems and more particularly to such systems pro-' vided with remotely disposed operator controlled automatic oiiices or switching centers. Specifically, the present invention relates to improvements'in telephone systems of the character disclosed in the copending application of Thomas F. Crocker,,Serial No. 418,483, filed November 10, 1941-, now Patent No. 2,311,214, granted February 14, 1943.

It is an object of the present invention to provide a telephone system of the type noted comprising improved apparatus iorv selectively 'controlling any one of a plurality of links disposed at a remote point over any one of a plurality of control trunks from any one .01 a plurality of operator positions at a switchboard, whereby connections may be set up and supervised in a ready and eflicient manner.

Another object of the invention is to provide in a telephone system including a group of switching links, a group of control trunks extending to an operator switchboard and automatic means for connecting any one of the links in the group having a call signal thereon to an idle one of the control trunks in the group, an arrangement for indicating to the operator switchboard the particular link'in the group hav-. ing a call signal thereon which is connected to .the particular control trunk in the group.

Another object of the invention is to provide in a telephone system ofthe type noted an improved arrangement for registering-the identity of the link in the group which is connected to a control trunk in the group and then for transmitting the. identification mentioned to the operator position at the switchboard answering the call on the control trunk-mentioned incident to theanswering operation.

A- further object of the invention is to provide a telephone system of the type noted comprising improved switching links, each including a call switch of the numerical type, whereby the call.

switch of a switching link connected to a controltrunk may be selectively controlled directly over the control trunk from an operator position at-the switchboard to set up a connection.

A further object of theinvention is to provide in a telephone system of the type noted, control trunk equipment terminatingthe control trunks and associated with the switching links, which equipment embodies improved facilities providing for the answering of calls, the setting up of conway of the switching links over the control trunks. v m

A still further object of the invention is'to provide in a telephone system including a group of switching links and a group of control trunksand a single supervisory conductor extending to an operator switchboard, an improved arrangement whereby call signals on the links in the group are transmitted'over idle ones of the con-' trol trunks in the group and supervisory signals on the links in the group are transmitted over thesingle supervisory conductor when it is idle.

Further features ofthe invention pertain to .the particular arrangement of the circuit elements of the system, whereby the above outlined and additional operating features are attained. The invention, both as to its; organization and method of operation, together with further objects and'advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which Figure 1 illustrates the general arrangement of a'telephone. system embodying the present invention; Figs. 2 to 19, inclusive, taken together, illustrate the details or a system having incorporated therein the features of the invention as briefly outlined above; and Fig. 11 illustrates the mode of combining Figs. 2 to 10,

inclusive, to form a unified system.

apparatus incorporated in the system Description of the nected by a number of control trunks, three being illustrated at NH, 102 and 103, each of the twowire type, and a single supervisory conductor C105; and the remote ofllce 3| and the distant oflice I are interconnected by a group of toll lines, including the toll line 30!, each of the twowire type. The central oflice 2| comprises a con- -trol switchboard 200 of the automatic type including a number of operator positions, the'flrst, second and third operator positions being respectively indicated at 20], 202 and 203 and an inter-' rupter 26; the distant ofllce 41 comprises a toll operator position 42 oi. any suitable type; and the remote oflice 3| comprises a local s'witch train and toll switching equipment 01' the automatic type.

In the remote *oflice 3| the local switch train nections and the monitoring of connections by comprises .a plurality of local links, including in the remote ofiice 3|.

the local link 3, and a local distributor 343 for distributing idle ones of the local links in a predetermined order; the local link 3 including a local finder 345 and a local connector 346. The toll switching equipment comprises a group of five toll links, including the third toll link 503 illustrated; the third toll link 503 including a toll finder 400 and a toll selector. 500. One end of each control trunk terminates in control trunk terminal equipment individual thereto disposed in the central ofilce 2|; and the other end of each control trunk terminates in control trunk equipment individual thereto disposed in the remote oifice 3 I. For example, one end of the first control trunk Hll terminates in first control trunk terminal equipment 6M individual thereto disposed in the central office 2|; and the other end of the first control trunk 1M terminates in first control trunk equipment 90! individual thereto disposed Similarly, the opposite ends of the secondicontrol trunk 102 terminate in second control trunk terminal equipment ill; and in second control trunk equipment 902 respectively disposed in the central ofilce 2| andin the remoteofilce 3|; while the opposite ends or the third control trunk [03 terminate in third control trunk terminal equipment 603- and in third control trunk equipment, not shown, re-' spectively disposed in the central ofilce II and in the remote ofilce' 3|. Finally one end of the supervisory conductor C105 terminates in supervisory equipment 605 disposed in the central oifice 2|; and the other end' 'of the supervisory conductor C105 terminates, in common equipment 80') disposed in the remote ofilce 3 I.

In the remote ofilce 3| the common equipment 800 has access to each oi! the-toll links in the group mentioned and is operative to select an idle toll link therefrom; and eachcontrol trunk equip-. ment has access to each or the toll links in the group mentionedand is operative to connect an idle toll link selected by the common equipment 8M thereto and consequently to the associated control trunk when the last-mentioned control trunk is idle. Also each control trunk equipment comprises a monitor switch and a trunk switch, each having access to each of the toll linksin the group mentioned, for purposes more fully explained hereinafter. Also the remote ofiice 3| comprises a group of toll line circuits terminating the group-o1 toll lines, this group circuits terminating'an associated group of C. L.

a R.- trlmks, this. group includingthe C. L. R.

trunk circuit 35. terminating the 0.1-. R..- trunk 33.. Also the remote oifice 3| serves a number of local subscriber substations, including the subscriber substation T, the subscriber substation T ator position at the control switchboard us;

while each equipment terminating the remote oillce 3| has. access by way oi'the individually associated monitor switch andthe individually associated trunk switch to each of the each of thetoll lines. in the group terminates at the toll operator position 42 in the distant exchange ll while the other end ofeach of the toll lines in the group-terminates in 8. corresponding one of the toll line circuits in the remote Each local finder and each local conofiice 3|. nector have access to each subscriber line terminating in the remote ofilce 3|; while each local connector has access to each oi the C. L. R. trlmks in the group. The toll finder 01' each toll link in the group mentioned has access to each of the toll, 7 line circuits and to each of the C. L. R. trunk circuits; while the toll'selector of each toll link in the group mentioned has access to each of the toll lines in the group and to each of a number 0t utility trunks, including the utility trunk I, provided in the remote ofilce 3|.

"' Preferably, .each operator position at the con-'- trol switchboard 103 is identical to the first operator position "I which comprises, as best shown in Fig. 2, a suitable telephone set 235, a'set or position keys, a suitable dial 238, and a group of signal lamps. More particularly, the set of position keys includes a common ring key Klli; a

common release key K2 l2; three trunk talk keys individual to the three control trunks, the first trunk talk key individual to the first control trunk Ill being indicated at K2; and live link hold keys individual to the five toll links the group mentioned, the first and third link hold keys respectively, individual to the first and third toll links in the'group mentioned being respectively indicated at K230 and K243. More particularly, 'the group of signal lamps comprises an answer lamp and a busy lamp individual to each ofthe 7 control trunks, the answer lamp and the busy lamp individual to the first control trunk 'I3| 4oualtoeachofthetolllinksinthegroupmentioned, the hold lamp and thesupervisory lamp individual to the first toll link, not shown, being respectively indicated at L252 and L25l, and the including the toll line circuit 3|! terminating the toil lin I; and a group of C. L; R. trunk .the other end of the ted control tnmk in 7 hold lamp and the supervisory lamp individual to the third toll link 503 being ,cated at L254 and L253. 1

Preferably, each control trunk terminal equip- 'ment is identical to the first control trunk terminal equipment Glll which comprises, as best shown in Fig. 6, a lamp switch on or the minor type, including three wipers ill to H3, inclusive, provided with individually assocated banks, a rotary magnet M6 for driving the wipers noted step by step .in the counterclockwise direction away from their normal rotary positions, and a release magnet ml! for releasing,the wipers noted and for causing them to-be returned to their normal rotary positions. Alsothe lamp switch ill have respective p to three groups of conductors respectively extend ing to the various hold lamps at th respective first, second and third operator positions at the control switchboard 2 33, for a purpose more fully explained hereinafter. Further the first control trunk terminal equipment ill comprises a relay group including an impulse relay R823, two hold relays R32! and R333, andananswerrelayRul.

toll linksin group. Oueend ol 1| Finally the first control trunk terminal equipment ill comprises a repeater 335 fl easaociatedend of the firstcontroltrunklll;

respectively indi-q an associated contact bank, a rotary magnet and a control network connected and arranged in a manner more fully explained hereinafter.

The supervisory equipment 650 comprises, as

best shown in Fig. 6, a lamp switch 660 of the minor type, including a single wiper 56! having M662 for driving the wiper noted stepby step in the counterclockwise direction away from its normal rotary position, and a release magnet M663 for releasing the wiper noted and for causing it to be returned to its normal rotary position. Also associated with the lamp switch 060 3| comprises conventional automatic substation Each subscriber substation in the remote ofilce equipment including a telephone instrument, a

ringer and a calling device or dial; and the toll operator position 42 in the distant omce 4| comprises conventional operator position equipment.

- Also, in the remote oifice 31, each of the line a control network connected and arranged in a I manner more fully described hereinafter.

The common equipment 000 comprises, as best shown in Figs. 7 and 8, a finder switch 120 of the rotary type, including two wipers HI and 122 provided with individually associated contact banks, and a rotary magnet M123 for driving the wipers noted step by step in the counter- A clockwise direction. Also thecommon equipment 800 comprises a relay group including an all-busy relay R130, a start relay R140, a, cutoff relay R150, two sender stop relays R8|0 and R820, a-

supervisory start relay R830, a sender start relay R040, an impulse relay R050 and two cycle relays R060 and R010. Finally the common equipment 800-comprlses a repeater H0 terminating the associated end of the'first control trunk 10l; and a control network connected and arranged in a manner more fully explained hereinafter.

Preferably, each control'trunk equipment is.

identical to the first control trunk equipment 901 which comprises, as best shown inv Figs. 8 and 9, a monitor switch 880 of the minor type, including three wipers 08! to 083, inclusive, provided with individually associated contact banks, a rotary magnet M884 for driving the; wipers noted step by step in the clockwise direction away from their normal rotary positions, and a release magnet M885,for releasing the wipers noted and for causing them to be returned to their normal rotary positions. Also a set of switch springs S886 is associatedwith the monitor switch 080 which is actuated when the wipersnoted are driven away from their normal rotary positions.

Also the first-control trunk equipment 90| come prises a trunk switch 9l0 of the rotary type, ill-f cluding five wipers 9| i to M5, inclusive, provided with individually associated contact banks,- and a rotary magnet M9l6 for driving the wipers noted step by step in th counterclockwise direc- 'tion. Finally the first control trunk equipment 00| comprises a relay group including a connect relayR920, a hold relay R030, an impulse relay H940, a release relay R945, a cutoif relay' R950,

a step relay R955 and a switch start relay R960:

and a control network connected and arranged in a. manner more fully described hereinafter.

The signal sender I000 comprises, as best shown in Fig. 10, a relay group including a con-- circuits 342, etc., as wellas the associated local distributor343, shown in Fig. 3, is of conven tional connection and. arrangement. Further each of the local finders 345, etc, and each 01 the local connectors 340, etc., shown-inFig. 3, areof conventional connection and arrangement; pref-' erably, these switches are of the well-known Strowger type. I

Preferably, each of the toll line circuits is identical to the toll'line circuit 0, shown in-Fig. 3. which comprises a relay group, including a ringup relay R320, 9. start relay R025 and a cutoff relay R330; and a control network connected and arranged in a manner more fully described hereinafter. Preferably, each of the C. L. R.

trunk circuits is identical to the C. L. R. trunk circuit 350, shown in Fig? 3, which'comprises a relay group, including a line relay R360, a start relay R310 and a cutoff relay R380, and a repeater 35l; and a control network connected and arranged in a manner more fully described hereinafter.

" Preferably, each of the toll links is identical to the third toll link 503 shown in Figs. 4 and 5'. In the third toll link 503 the toll finder 400 comprises an access switch 410 ofv the rotary type, including three wipers 40! to. 403, inclusive, pro

vided with individually associated contact banks and arotary magnet M404 for driving the wipers noted step by step in the counterclockwise direction. Also the toll finder 400 comprises a relay group, including a, step relay R4l5, a switchthrough relay R420, a supervisory relay R430, an equipment start relay R440. a switch relay R450, and two control relays R460, and R410; and a control network connected and arranged in a manner more fully described hereinafter. In the third toll link 503 the toll selector 500 comprises a switch mechanism 5l0 of the Strowger t pe. The switch mechanism 5l0 comprises a wiper carriage mounted for bothvertical and rotary movements and supporting a wiper set including three wipers 5 to 5l3, inclusive. A semi-cylindrical contact bank. is associated with the wiper set and comprises ten vertically spacedapart rows or levels or contact sets, eachrow of contact sets including ten individual contact sets arranged in circumferential spaced-apart relationship. Further the switch mechanism I 5I0 comprises a vertical magnet M5 for driving the wiper carriage step by step in the vertical direc-g tion away from its normal vertical position, a rotarymagnet, M5l5 for driving the wiper carriage step by step the rotary direction away from its normal rotary position, and, a release -magnet M5l1 for releasing the wiper carriage and for causing it to be returned to its normal i rotary and vertical positions. 'Also the switch mechanism 5l0 comprises three setsof switch springs SSH, S520 and 852i which are actuated when the wiper carriage is moved in the vertical direction away from its normal vertical position,

trol relay Rl0l0 and fiv count relays Rl020,

Rl030, Rl040, RID-5.0 and RIOS0, the various count relays respectively corresponding to the -five individual toll links in the group mentioned.

and a set of switch springs S522 which isactuated when the wiper carriage .is driven eleven steps in the rotary direction away from its nor mal rotary position. Further the toll selector 500 comprises a relay group, including a control relay R400, a switch-through relay R500, an impulse relay R500, a release relay R505, a hold relay R550, a transfer relay R500, a ring relay the actual number of links which may be pro-.

vided will be determined in accordance with the amount of toll trafilc which is to be handled in the remote ofilce 3|. Similarly, the actual number of control trunks which will be provided, interconnecting the central fllce 2l and the remote ofiice 3|, will be determined in accordance with the amount of toll traific which is to be handled at the control switchboard 200. Finally the actual number or operator positions which are provided at the control switchboard 200 will be determined in accordance with operating practice in view oifv the amount of toll trafi'ic to be handled thereat.

A better understanding of the connection and arrangement of the apparatus incorporated in the system will be facilitated from a consideration 01' the detailed operation of the various pieces of apparatus incident to the setting up of the various toll and trunk calls, as will appear hereinafter.

Initiation of a toll call at a subscriber substation in the remote ofl'lce Considering now the initiation or a toll call at a subscriber substation, such, for example, as the subscriber substation T, in the remote. oflice 3|, the subscriber at thev calling subscriber substation T first removes the receiver of the telephone instrument thereat from its associated switch-.- hook, whereby the line circuit 302 individually associated with the subscriber line 3 operates in order to initiate operation of the associated local distributor 303. The local distributor 303 operates inorder to. assign an idle one of the local links to'the use of the calling subscriber substation T, such, for example, as the local link 3 illustrated. The local finder 305 then operates to find the subscriber line Ill extending to the callingsubscriber substation T, whereupon the local connector 300 is rendered responsive to digits transmitted thereto; and the line circuit 302 operates in order to mark the subscriber line operates to complete, at the contacts 30L an obthis point it is noted that, when the first control scriber line in to the calling subscriber substationT. I

When the line relay R300 is thus energiud it vious circuit for energizing the winding of the start relay R310, thereby to cause the latter relay to operate shortly thereafter, the start relay R310 being of the combination slow-to-operate and slow-to-release' type. Upon operating, the start relay R310 interrupts, at the contacts 313, the previously traced path for applying battery potential to the control conductor C303 of the C. L. R. trunk 390; and completes, at the contacts 312, an obvious path for applying ground potential to'the control conductor C303 of the C. L. R. trunk 390, whereby the latter trunk is marked as busy to the local connectors having access thereto; Also the start relay R310 completes, at the contacts 31!, an obvious path for applying battery potential by way of the winding of the cutofi relay R300 to the control conductor C300 of thetrunk 305 extending to the C. L. R. trunk circuit 350 and accessible to the toll finders of the various toll links,'thereby to mark the trunk 3105' as a calling trunk to the.

toll finders of j the various toll links. Further the start relay R310 completes, at the contacts 314, an obvious path,'including the contacts 302,

energizing the winding of the start relay R in the event the common equipment 000 and at least one control trunk equipment are idle at this time; which circuit extends, when completed, from the grounded start conductor C155 by way of the' contacts 13l,' thewinding of R100, and the contacts'0ll, "I and 032 to battery: whereupon the start relay R100 operates. At

trunk equipment '90! is busy due to a busy condition of the first control trunk 10l, either the' connect relay R020 or the hold relay R030 occupies its operated position, as explained more fully hereinafter. When the connect relay R020 busy relay R; and when the hold relay R030 3 as busy to the local connectors having access thereto. The subscriber at thecalling subscriber substation T then dials one or more digits into the local connector 300, thereby to cause'the local connector 300 to seize an idle' C. L; R. trunk in the associated group, such, for example, as the C. L. R.'trunk' 300; the C. L. R. trunk 300 being marked as idle by the presence of battery potential upon the control conductor C303 thereof viathe contacts 313 and the resistor 305. Whenthe C. L. R. trunk 300 is thus seized a series circuit conductor C302 and from battery by way or the" lower -winding of R300 and the winding 302 of the repeater'35l to the line conductor 03", the.

line conductors C30l and C302 01 the C. L. 'R.

trunk 300 being connected by way of the local connector 300, the local finder 300 and the suboccupies its operated position there is prepared, atthe contacts 035, a point in a circuit traced hereinafter for energizing the winding of the all-busy relay R130. Accordingly, when the first control trunk equipment "I is busy the conductor C001 extending to the'winding of the allbusy relay R130 in the common equipment 000 is connected. by way of the contacts 021 or, 035 of the respectively associated relay R020 or R030 in the'first control trunk equipment 001 to the conductor C030 extending tothe second control trunk equipment 00:. Hence it will be understood that, when each of the three control trunk equipments is busy, 'the previously mentioned chain circuit, including the conductors C001 and 0 C030, is completed for energizing the winding of the all-busy relay R130; whereupon the latter relay operates to interrupt, at the contacts 131, a point inthe previously traced'circuit for energizing the windingof the start relay R100. In

the last-mentioned event, the application of ground potential to the start conductor C is ascaaas ments becomes idle in an obvious manner.

Continuing now with the operation of the common equipment 800, when the start relay R140 operates it completes, at the contacts 142, an obvious holding circuit, including the contacts 13l, 8! I, 82! and 832, for energizing the winding thereof. Also, upon operating, the start relay R140 prepares, at the contacts 143, a circuit for energizing the rotary magnet M123 of the finder switch 120; the last-mentioned circuit extending from the wiper 122 of the finder switch 120 by way of the contacts 152, 143 and 124 and the rotary magnet M123 to battery. The above-mentioned circuit for energizing the rotary magnet M123 is completed in the event the wiper 122 of the finder switch 120 engages a cont t in the associated contact bank terminating a, test conductor having ground potential thereon extending to a busy toll link in the associated group. Assuming thaipthe fifth toll link inv the associated group is busy at this time, ground potential appears upon the test conductor thereof, whereby the above-traced circuit for energizing the rotary magnet M123' is completed. When thus energizedtherotary magnet M123 operates,

thereby to condition the wipers noted of the,

finder switch 120 to be driven one step in the counterclockwise direction and to interrupt, at

the contacts 124, the above-traced circuit for energizing the rotary magnet M123. The rotary magnet M123 then restores, thereby to drive the wipers noted of the finder switch 120 one step in the counterclockwise direction and toreprepare, at the contacts 124, theabove-traced cirfrom ground by way of the contacts 144, the winding of R150, the contacts-143 and 152, the

' wiper 122 of the finder switch 120 and the engaged contact in the associated contact bank,

' 0166, the contacts 421 and the winding of R440 to battery. When the circuits mentioned are completed the cutoff relay R150 operates. However, the equipment start relay R440 and the rotary magnet M123 do not operate due to the high series resistance of the winding of the cutoff relay R150. Accordingly further operation of the finder switch 120 is arrested at this time.

' Upon operating, the cutoff relay R150 interrupts,

cuit for energizing the rotary magnet M123. At

this time the wipers noted of'the finder switch 120 engage the first contacts in the associated 395 extending to the'C. L. R. trunkcircuit 350 contact banks, whereby the idleor busy condition of the first toll link in the associated group is tested. Further operation of the finder switch 120 continues untilan idletoll link in'the associated group is tested.

Assuming that the third toll link 503 illustrated is the first idle toll link in the group, the v rotary magnet M123 continues to operate intermittently until the wiper 122 thereof engages the contact in the associated contact bank terminating the test conductor C156 individual to the idle third -toll link 503, the test conductor at the contacts 152,'the previously traced series circuit for energizing the winding of the cutoff relay R150 and the winding of v the equipment start relay R440; however, the cutoff relay R150 remains in its operated position due to the previously completed holding circuit for energizing the winding thereof in series with therotary magnet M123. Also the cutoff relay R150.completes, at the contacts 153, an alternative circuit, including the wiper 122 of the-finder switch 120 and the engaged contact in the associated contact bank, C163 and the contacts 421, for

energizing the winding of the equipment startrelay R440, whereupon the latter relay operates. Upon operating, the equipment start relay R440 completes, at the contacts 445,- a holding circuit for energizing the winding thereof; the last-mentioned circuit includin the contacts 15l, the wiper 12! of the finder switch 120 and the engaged contact'in the associated contact bank, and the hold conductor C165. Accordingly, at this time, the common equipment 800 has operated to select theidle third toll link 503 in'the associated group to the used the calling trunk connected to the calling subscriber substation T.

Continuing now with the operation of the third toll link 503, upon operating, the equipment start relay R440 completes, at the contacts I, "an

' obvious path for applying ground potential to 0166 having battery potential applied thereto by way of the winding of the equipment start relay R440 and the contacts 421. Also, it is noted that, upon operating, the start relay R140 completes,

at the contacts 144,- a path, including the contacts 143 and 152 and the wiper 122, for shortcircuiting'the winding of the cutoff .relay R150 as long as the wiper 122 engages a contact in the associated contact bank having ground po-- tential thereon. In the present example, when the wiper 122 of the finder switch engages the contact in the associated contact bank terminating the test conductor C163 having battery potential thereon, the above-mentioned path for short-circuiting the winding of the cut-oil relay R is interrupted; whereupon a series circuit is completed for energizing th winding of the cutoff relay R150 and the rotary magnet M123 of the-finder switch 120 and a multiple series circuit is completed for energizing the winding of the cutoff relay R150v and th winding of the equipment start relay R440. The circuits mentioned extend from ground by way of the contacts 144. the winding of R150, the contacts 124 and the rotary magnet M123 to battery; and

the hold conducto'rC485, thereby to complete .an obvious circuit, including the resistor 4", 'for energizing the lower winding of the switchthrough relay R420-in the toll finder 400. When the lower winding of the switch-through relay R420 is thus energized the latter relay is rendered exceedingly fast to operate when the upper winding thereof is'subsequently energized; Also the application of ground potential to the hold conductor C485 completes an obvious circuit, including the contacts 482 and the set of switch springs S520, for energizing theupper winding of the transfer relay R560 in the toll selector 500, thereby to cause the latter relay to operate Further the equipment start relay R440 com:

energizing the lower winding of the supervisory relay R430, thereby'to cause the latter relay to .-operate and interrupt, atthe contacts 43|,- any obvious path for short-circuiting the ing thereof.

Also the application of ground potential to the hold conductor C485 completes a circuit, including the

contacts

426 and 6, for energizingthe rotary magnet M404 of the access switch 410, thereby to cause the latter magnet to operate. Upon operating, the rotary magnet M404 condiupper windtions the wipers noted ofv the access switch 0 a to be driven one-step in the counterclockwise direction; and completes, at the contacts 405, an.

obvious circuitfor energizing-the winding of the step relay R415, thereby to cause the latter relay to operate. Upon operating, the step relay R4l5 interrupts, at the contacts 410, the previously traced circuit for energizing the rotary magnet M404, whereupon the latter magnet restores. Upon restoring, the rotary magnet M404 drives the wipers noted or the access. switch one step in the counterclockwise direction and interrupts, at the contacts 405, the previously mentioned circuit for energizing the winding of the step relay R4l5, whereupon the latter relay re-- stores. Accordingly the rotary magnet M404 and the step relay R4|5 interact, in the manner described above, whereby the wipers notedof the access switch' 410 are driven step by step in the counterclockwise direction until they engage the contacts in the associated contact bank terminating the trunk 305 extending to, the calling C. L. R. trunk circuit 350.

When the access switch 0 finds the trunk 305 extending to the calling C. L. R. trunk circuit 350 a circuit for energizing in series the upper winding of the supervisory relay R430, the upper winding of the switch-through relay R420 and the winding of the cutoff relay R380 is completed; the last-mentioned circuit extending from the grounded hold conductor C405 by way of the upper winding of R430, the upper windingpf R420. the wiper 403 of the access switch 0 and the engaged contact in the associated contact bank, the control conductor C300 of the trunk 305, the contacts 3" and the winding of R300 to battery.

" When this series circuit iscompleted the supervisory relay R430 is retained in its operated position and the switch-through relay R420 operates exceedingly, fast as it is- 01' the polarized type, as previously noted. Upon operating, the switchthrough relay R420 completes, at the contacts 424, an obvious path in the above-traced series circuit for short-circuiting the upper winding thereof; whereby the upper winding of the supervisory relay R430 is energized in series with the winding of the e ter: relay am, in an obvious manner. The cutoff relay R300 then operates to complete, at the contacts l, an obvious mul-' tlple point around the contacts 3" in the previously traced circuit for energizing the winding thereot in series with the upper winding of the supervisory relay R430. Also, upon operating, the cutoff relay R380 interrupts, at the contacts 382. the previously traced original path for applying ground potential in the C. L. R. trunk circult 350 to the start conductor C155 the common equipment 000. p

\Also, upon operating, the switch-through relay R420 interruptgat the contacts 420, a point in the previously traced circuit for energizing the extendingto I rotary magnet M404, thereby positively to arrest J iurther'operation oi the access switch 0 at this time. Also the switch-through relay R420 com pletes, at the contacts 423, an obvious multiple path for applying ground potential to the hold conductor C405; and completes, at the contacts 425, an obvious multiple holding circuit for enersizing the intermediate winding thereof. Also,

-the-switch-through relay R420 interrupts,at the contacts 421, the original circuit forenergizing the winding of the equipment start relay R440; however, the latter relay-remains in its operated position at this time due to the completed holding circuit for energizing the winding thereof, including the hold conductor C105. Further the gswitch-through relay R420 completes, at the contactsi'428, an obvious path for applying ground potential to the testvconductor C150 extending to the finder switch 120, thereby positively to mark the third toll link 503-as busy to the common equipment 000. Further the switch-through relay R420 completes, at the contacts 422, an obvious circuit for energizing the winding. of the switch relay R450, thereby to cause the latter reexplainedhereinafter. J

Upon operating, the control relay R410 completes, at the contacts 412, an obvious path for applying battery potential by way of the wind-,

ing of the control relay R480 to the test conductor C005 and an obvious multiple path for applying battery potential by way of the resistor 400 and the contacts 403 to the test conductor C085. the contacts 4", an obvious path ior'applying ground potential to the control conductor C004. The application or battery potential to the test conductor C005 marks the third toll link 503 as a calling link to the trunk switches of the various control trunk equipments; while the application of the switch start relay R080 in the first control trunk equipment 00l inthe event the associated first control trunk "I is idle at this time; in which event the hold relay R030 and the cutoff relay R050 in the first control trunk equipment 0" occupy their restored positions. .Also' the application of ground potential to the chain start conductor C082 is connected by way of the con 05401 the restored switch start relay R080 in the first control trunk equipment "I to the conductor C000 extending to the second control trunk equipment 002; whereby a multiple circuit substantially identical to that traced above is prepared ior'energizing the winding of the switch start relay in the second control trunk equipment 002. Further it is noted tha the application of ground potential to-the ch start conductor C082 is similarly extended from the second control trunk equipment 002 to the third control trunk equipment, not shown, in order to prepare a further multiple circuit for energizing the winding of the switch start relay in the third control trunk equipment. Accordingly it will be understood that the application of ground potential to. the chain start conductor C062 prepares multiplecircuitsfor energizing the windings oi the switch start relays in the various control trunk equipments; and that the circuit for energizing the winding of the switch start relay in each idle control trunk equipment is completed. -At this point it is noted that the various switch start relays R080 etc. in the corresponding control Also the controlrelay R410 completes, at.

trunk equipments are of the slow-to-operate type; and that these switch start relays are graduated progressively in their slow-to-operate characteristic; whereby the first idle control trunk equipment 90| in the chain is preferred. In other words, the switch start relay R960 in the first control trunk equipment SM is slightly faster to operate than the switch start relay in the second control trunk equipment 902, and the switch v to operate than the corresponding switch start relays. in the'second and third control trunk equipments, as previously noted. Upon operating, the switch start relay R960 completes,'at

the contacts 963, an obvious holding circuit, including the grounded chain start conductor C862, for energizing the winding thereof; and interrupts, at the contacts 964, the'previously traced connection between the grounded chain start conductor C862 and the conductor C980 extending to the second controltrunk equipment 902; whereby the initiation of operation of thesecond and third control trunk equipments is efiectively cut off, in an obvious manner.

Also, uponopcrating, the switch start relay R960 completes, at the contacts 962, an obvious circuit, including the contacts 952 and 956, for energizing the rotary magnet M9l6 of the trunk switch 9| 0. When thus energized the rotary magnet M9! 6 operates to condition'the wipers noted of the trunk switch M to be driven one step in the counterclockwise directionand to complete, at the contacts 9l1, an obvious circuit for energizing the lower winding of the step relay R955, whereby the latter relay operates. Upon operating, the step relay R955 interrupts, at the contacts 956, the previously traced circuit for energizing the rotary magnet M9l6, thereby to cause the latter magnet to restore in order to drive the wipers noted of thev trunk switch 9I0' one step in the counterclockwise direction and to interrupt, at the contacts 9", the previously mentioned circuit for energizing the lower winding of the step relay R955, whereupon the latter relay restores. Accordingly the rotary magnet M9l6 and the step relay R955 interact in the manner described above until the wipers noted of the trunk switch 910 engage the contacts in the associated contact bank terminating the conductors extending to the third toll link 503. More particularly, when the wiper 9| of the trunk contact bank terminating the test conductor C985 extendingto the third toll link 503, a series circuit is completed for energizing the lower winding of the cutoff relay R950, the upper winding of the step relay R955 and the winding of the control relay R460; this circuit extending from ground by way of the lower winding of R950,

. the upper winding of R955, the contactsv96l,

the wiper 915 of the trunk switch m and the engaged contact in the associated contact bank,

C985, the contacts 4'12'and the winding oi. R460 to battery. When this series circuit is completed switch'9l0 engages the contact in the associated the step relay R955 is retained in its, operated position and the cutofi relay R950 operates; and shortly thereafter the control relay R460 operates, the latter relay being of the slow-to-operate typ Upon operating, the cutoff relay R950 interrupts, at the contacts 952, a further point in the previously traced circuit for energizing the rotary magnet M916, thereby positively to arrest further operation or the trunk switch 910 at this time;

and interrupts, at the contacts 953, a furtherpoint in the previously traced original circuit for energizing the winding of the switch start relay R960, thereby to mark the first control trunk equipment l as busy at this time. Also when the wiper 9 of the trunk switch 9l0 engages the contact in the associated contact bank ter minating the grounded control conductor C984 extending to the third toll link 503 an obViOllS circuit, including the contacts 932, is completed for energizing the winding of the connect relay R920, thereby to cause the latter relay to operate.- Also, upon operating, the cutofi relay R950 com-1, K plates, at thecontacts !,an obvious holding circuit, including the wiper 9| 4 of the trunk switch 9l0 and the engaged contact in the associated contact bank and the grounded/ control conductor C984, for energizing the upper winding thereof. a

Upon operating, the connect relay R920 interrupts, at the contacts 923 and 925, a normally completed connection between the winding "2 of the repeater H0 and the

wipers

883 and 882 of the monitor switch 880; and completes, at the contacts 924 and 926, an obvious connection between the winding 1| 2 of the repeater 1| 0 and the wipers 9l2 and 9I3 of the trunk switch 9l0.

More particularly, at this time, the repeater 1H1 terminating the end of the first control trunk 10l in the remote oflice 3| is operatively connected to the repeater 35! in the C. L. R, trunk circuit 350; the winding N2 of the repeater .1|0 is connected by way of the conductors C162 and C163 and the contacts 924 and926 to the wipers 9|2 and N3 of the trunk switch 9l0;'the wiper -9l2 of the trunk switch 9l0 is connectedby way of the engaged contact in the associated contact bank,

C992 and the contacts 45! to the wiper 402 of the.

access switch M0; the wiper 9I3 of the trunk switch M0 is connected by way of the engaged contactin the associated contact bank, C983 and the contacts Hi to the wiper 40l of the access switch' ,0; and the wiper 402 of the access switch 0 is connected by way of the engaged contact in the associated contact bank, the line conductor C391 of the trunk 395, the winding 355 of the repeater 35i, the condenser'351, the

winding 354 of the repeater 35l and the line conductor C396 of the trunk 395 to the contactengaged by the wiper 40! of the access switch 0. Also, upon operating, the connect relay R920 interrupts, at the contacts 92L an obvious connection including the conductor C16l between the simplex of the winding 1ll of the repeater H0 and the windings oi the' impulse relay R940 and the release'relay R945; and completes, at the contacts 922, a connection between the simplex of the winding 1, of the repeater 1l0 and-"the code conductor C863 extendingtothe common equipment 800. More particularly, the simplex of the winding 1 .of the repeater H0 is connected by way of thehco'nductor C161, the contacts 922, the wiper 9H of'the trunk switch M0 and the engaged contact inthe associated contact bank, can and the contacts 444 to thecode conductor C863 extending to the common equipment 880. Finally the connect relay R920 prepares, at

the contacts:821, a further point inthe previously traced chain circuit for energizing th winding of explained.

Accordingly, at this time, the first control trunk equipment-M has been selected for use by the chain start arrangement described above; the

trunk switch 8I0 of the first trunk control equipment 80I has operated to seize the third toll link 503; and the connect relay R820 has operated to the all-busy relay R130, for the purpose previously connect the trunk switch 8! to the first control 1 trunk 10I extending to the remote ofiice 8| and the central oihce 2 I Upon operating, the control relay R460 interrupts, at the contacts 463, the previously traced 'path for applying battery potential by way of the resistor 466 to the test conductor C885; and completes, at the contacts 462, an obvious alternative holding circuit, including the contacts 564, for energizing the winding thereof. Also the control R468 completes, at the contacts 464, an obvious path, including the contacts 448, iorapplying ground potential to the start conductor C164 extending to the common equipment 808; and com-,

pletes, at the contacts 465, an obvious path, including the contacts 448 and the resistor 461, for applying battery potential to the third markin conductor C865'individua1 to the third toll link 588. and extending toithe signalsender I000.

mentioned cii'cuit for energizing thewinding of the impulse relay R858,- thereby to'cause the latter relay to restore. Upon restoring, the impulse relay R850 interrupts, at the contacts 85I,

the previously mentioned circuit for energizing the winding of the cycle relay R860, thereby to cause the latter relay to restore. Upon restoring, the cycle relay R860 recompletes, at the contacts 86I, the previously traced original circuit for energizing the winding of the cycle relay R810, thereby to cause the latter-relay to reoperate. Accordingly the cycle relay R810, the impulse relay R850 and the cycle relay R860 interact in the manner described above; whereby the impulse relay R850 is operated and restored intermittently one or more times until operation of the relays mentionedis arrested, in a manner more ,fully explained below.

Each time the impulse relay R850 operates and restores it completes and then interrupts, at the contacts-853, an obvious path for applying ground potential to the conductor CI01I extending to the signal sender I000; and completes and then interrupts, at the contacts 854, an obvious path,

.including the

contacts

8, 824 and 843, for applying ground potential to the conductor C I 012 extending to the signal sender I000. Also at this time ground potential is applied by way'of the contacts 8I4, 828 and 842 to the conductor CI018 extending to the signal sender I008. The first time ground potential is connected to the conductor CI01I an-obvious path, including the contacts I0 and the grounded conductor CI018, is

' completed for short-circuiting the lower winding R858 in orderto retain the latter relays in their operated positions. Further the control relay The application of ground potential to the start conductor C164 completes an obvious circuit, including the contacts 14 I for energizing the wind-,

' ing of the sender start relay R840, thereby to cause the latter relay to operate. Upon operating, the sender start relay R848 completes, at the contacts 842, an obvious circuit, including the

contacts

8, 824 and 86I, for, energizing the winding of the cycle relay R810, thereby to cause the latter relay to operate. Uponoperating, the' cycle relay-R810 completes, at the contacts 812, anebvious holding circuit, includingithe contacts I, for energizing the winding thereof and completes, at the contacts 8", an obvious circuit for energizing the winding of the impulse relayR858. when thus energized the impulse relay R858 operates to complete, at the contacts I, an ob yious circuit for energizing the winding of :the

cycle relay R060, thereby to cause the latter relay to operate. Upon operating, the cycle relay R868 interrupts, at the contacts I, the previ-- ously traced holding circuit for energizing the winding of the cycle relay R810, thereby to cause r the latter relay to restore. Upon restoring, the

cycle relay R810 interrupts, at the contacts 812, a further point-in the previously traced holding circuit for energizing the winding thereof; and interrupts, at the contacts 81I, the previously of the control relay RIOI0; and the first time ground potential is connected to the conductor CI812 a circuit, including the contacts I068, I 054,

I044, I034 and I624, is completed for energizing the'winding of the first count relay RI020. When thus energized the first count relay RI020 operates to prepare, at the contacts I02I, a holding circuit traced hereinafter ,for energizing the winding thereof in series with the lower winding of the control relay RI8I8; prepares: at the contacts I022, a circuit traced hereinafter forenergizing the winding of the second count relay.

RI880; completes, at the contacts I020, an ohand the grounded conductor CI012, for energizing the winding thereof; and interrupts, at the contacts I024, the. previously traced original operating circuit for energizing the winding thereof. g

- .The first time ground potential is disconnected from the conductor CI812the previously traced holding circuit {or energizing the winding of the first count relay RI828 is interrupted; and the first time ground potential is'disconnected from 'vious' holding circuit, including the contacts IOI4 the conductor CI01I the previously traced path for short-circuiting the lower winding of the control relay'RIlIl is interrupted. At this time the previously mentioned holding circuit for energizing the winding of the first count relay RI020 in series with the lower winding of the control relay RIOI0 is completed and extends from the grounded conductor CI013 byway of the lower .winding of RIOI0, the contacts I08I and I82I and the winding of RI020 to battery. When this holding circuit is completed the first count relay RI028 is retained in its operated position and the controlrelay RI 8| 8 'operates. Upon operating, the control relay RI 0I6 interrupts, at the contacts III I, a further point in the previously traced path for short-circuiting the lower winding thereof; prepares, at the contacts -IOI2, a

circuit traced hereinafter for energizing the upper winding thereof; interrupts, at the contacts IOI4, a point in a circuit traced hereinafter for energizing the Winding of the third count relay RI040; and prepares, at the contacts IOI0, a iur-' ther point in the previously mentioned circuit for energizing the winding 01' the second count relay The second time ground potential is' connected to the conductor CIO'II an obvious circuit is completed for energizing the upper winding of the control relay RIOI; and the second time ground-potential is connected to the conductor CI 012 the previously mentioned circuit, including the contacts IOI0 and I022, is completed for energizing the winding of the second count relay RI030. When thus energized the second count relay Rl030 operates to complete,

at the contacts I002, an obvious holding circuit, including the contacts I0 and the grounded conductor CIOI3, for energizing the winding thereof. Also the second count relay, R1030 interrupts, at the contacts I03I, the previously traced holding circuit for energizing the winding of the first count relay RI020 in series with the lower winding of the control relay RIOI0, thereby to cause the first count relay RI020 to restore; the control relay 'RIOI0 remaining in its operated position due to the completed holding circuit for energizing the upper winding thereof. Further the count relay RI000 prepares, at the contacts I000, a point in a circuit traced hereinafter for energizing the winding of the third count relay RM; and interrupts, at the contacts I004, a further point in the previously traced original circuit for energizing the winding of the first count relay RI020. Upon restoring, the first count relay RI020 interrupts, at the contacts I02I, a further point in the previously traced holding circuit for energizing the winding thereof in series with th lower winding of the control relay RIOI0; interrupts, at the contacts I022, the previously traced original oper'- ating circuit for energizing the winding 01" the second count relay RI000; interrupts, at the con-,

tacts I020, a' further point in the previously count relays R I020, Rl000, RI040, BMW and Rl000 are successively operated in response to a corresponding number of operations of the impulse relay R050 in the common equipment 000. 'As the count relays Rl020, RI030, etc., in the signal sender I000 operatesequentially the cor-' responding toll links in the associated group are tested in order to determine which of the toll links mentioned is connected at this time to the trunk switch 0l0 of the first control trunk equipment SM and consequently to the first control trunk 10l extending between the remote ofiice 3| and the central ofiice 2|. Hence, in the present example, when the third count relay RI040 is operated the third toll link 503 is tested as connected via the trunk switch 0I0 of the first control trunk equipment 00I to the first control trunk 'IOI. More particularly, when the third count relay'RI040 operates it completes, at the contacts I045, a circuit for energizing the wind.- ing of the senderstop. relay ROI0; the lastmentioned circuit extending from ground by way of the winding of ROI0, the contacts 154 and I045, the third marking conductor C000 individual to the third toll link 503, the contacts 440 and 405 and the resistor 401 to battery. When thus energized the sender stop relay R0l0 operates to complete. at the contacts '0I2, an 4 obvious holding circuit, including the contacts 0 and the resistor 844. for energizing the wind ing thereof. Also the sender stop relay ROI0 interrupts, at the contacts 0, the previously traced circuit'for energizing the winding of thecycle relay R010, thereby tocause the latter relay to restore and remain restored; whereby the impulse relay R050 and the cycle relay R000 are restored andremain restored. Also the sender stop relay ROI0 interrupts, at the contacts 0, thepreviously traced path for applying groundv potential tothe conductor CNN; and the impulse relay R050 interrupts, at the contacts 053 and 054, the previously traced paths for apply-- ing ground potential to the conductors CI01I and CIO'I2. when ground potential'isremoved from the conductors C! 0', CM" and CI 010 extending to the signal sender I000 the control traced original holding circuit for energizing the winding oi the first count relay RI020; and prepares, at the contacts I024, a further point in the previously traced original circuit for'englgggigig the winding of the first count relay The second time ground potential is disconnected from the conductor CI01I the previously traced holding circuit for energizing the upper winding of the control relay RIOI0 is interrupted, thereby to cause the latter relay to restore. Upon restoring, the control relay Rl0l0 interrupts, at

the contacts] IOI2, a "further point in the previously traced holding circuit for energizing the upper winding thereof; prepares, at the contacts IOII, a further point in the previously traced original path for shdrt-circuiting the lower winding thereof; interrupts, at the contacts IOI3. a further point in the previously traced circuit for energizing the winding. of the second count re lay RI030; and prepares, at the contacts 10,

- times under the control of the signal sender I000 relay RIOI0 and the operated one of the count relays R1020, RI 030 etc. restore.

Accordingly, in the present example, the impulse relay R050 operates and then restores three in view of the fact that the third toll link 500 in the associated group is connected to the first control trunk 10| extending between the remote oflice 3| and the central ofiice 2|, as explained above.

Each time the impulse relay R050 operatesand a point in the previously mentioned circuit for gileirgoizing the winding of the third count relay In view'of the foregoing explanation of the mode of operation of. thecontrol relay RIOI0 in conjunction with the first count relay RIM. and the. second count relay vRI000 inthe signal sender I000, it will be understood that the five restores it completes and then interrupts, at the w contacts 052, an obvious path, including the resistor 045 and the contacts'033, for applying battery potential to-the code conductor C003 which is connected by way of the previously traced path to the simplex. of the winding 1 ll of the repeater H0. Accordingly, in the present example, three battery impulses are transmitted over the code conductor C000 to the simplex of the winding Ill of the repeater I I0. The three batteryimpulses transmitted to the simplex of the winding III of the repater H0 are conducted over the two line conductors in parallel over the first control trunk "I to the simplex of the winding 00'! of the repeater 005; and therefrom by way of C090,

the contacts 042' andthe winding of the impulse relay R020 to ound. Accordingly the impulse relay R020 in the first control trunk terminal equipment BM in the central oifice 21 operates and then restores three times.

Also, upon operating, the sender stop relay Rl0 interrupts, at the contacts 0l l, the previously traced holding circuit for energizing the winding of the start relay R140, thereby to cause the latter relay to restore. Upon restoring, the

start relay R140 interrupts, at the contacts 142, a further point in the previously traced holding circuit for energizing the winding thereof; and interrupts, at the contacts 144, the previously traced holding circuit for energizing the winding of the cutoff relay R150 in series with the, rotary magnet M123 ofthe finder switch 120 in order to cause the cutofl relay R150 to restore. Upon restoring, the cutoff relay R150 interrupts, at the contacts L the previously traced holding circuit for energizing the winding of the equipment start relay R440 in order to cause the. latter relay to restore. Upon restoring, the equip ment start relay R440 interrupts, at the contacts I, the previously traced original path for applying'ground potential to the hold conductor C485; and interrupts, at the contacts 442, the

at this time, ground potential is connected by way of the winding of the release relay R045, the winding of the impulse relay R540, the contacts 440, 000i, the wiper 0 of the trunk switch 0" and the engaged contact in the associated contact bank, the contacts 022 and C1" to the simplex of the winding 1| I of the repeater H0, for a purpose more fully explained hereinafter. Further the equipment start relay R440 interrupts, at the contacts 445, the previously traced path for applying ground potential to the chain start coninterrupts, at the contacts 000,-a further point in the previously traced holding circuit for energizing the winding thereof; and recompletes,,at

' the contacts 004, the previously mentioned conductor C002; thereby to interrupt the previously traced holding circuit for energizing the winding of the switch start relay R000 in the first control trunk equipment 00 i, whereupon the a .operated position at this time due to the completed holding. circuit for energizing the upper v winding thereof in series with the winding of the nection between the chain start conductor C852 and the conductor C000 extending to the second control trunk equipment 002; whereby the second and third control trunk equipments are rendered available to the use of the next calling toll links in the associated group. Also the switch start relay R000 interrupts, at the contacts "I, a previously completed path for short-circuiti-ng the lower winding of the cutoff relay R050 in series with the upper winding of the step relay R055. The last-mentioned path was completed incident to the operation of the control relay R400, previously explained, and extended, when completed,-

from ground by way of the

contacts

564, 402 and 412, C005, the wiper N5 of the trunkswitch M0 and the engaged contact in the associated contact bank, the contacts 05 i, the upper winding of R955 and the lower winding of R050 to ground. When the above-mentioned path for shortcircuiting the lower winding of the cutofi relay R050 in series with the step relay R055 was completed incident to the operation of the control relay R460, the step relay R055 restored; however, the cutoff relay R050 remained in'its operated position due to the previously completed holding circuit for energizing the upper winding thereof. Upon restoring, the sender start relay R040 interrupts, at the contacts 0, the previously traced holding circuit for energizing the winding of the sender stop relay R0 I 0, thereby to cause the latter relay to restore.

at the contacts 0| i, the previously traced circuit gorfnergizing the winding .01 the start relay Accordingly, at this time, the common equipment 000 is completely released and available for further use; the first control trunk equipment 00| is busy, the connect relay R020 and the cutoff relay R050 therein occupying their operated positions; the second and third control trunk equipments are rendered available to the use of calling toll links in the associated group: the signal sender i000 is completely released: and the third toll link 50.0 is operatively connected via the trunk switch N0 of the first control trunk equipment 001 to the first control trunk 1" extending Upon re-- storing; the sender stop relay R0l0 reprepares,

between the remote ofiice 0| and the-central o winding of the hold relay R025, therebyto cause cutoif relay R300 in the C. L. R. trunk circuit 050. Further-the equipment start relay R440 interrupts,'at the contacts 440, the previously traced path for applying ground potential to the start conductor C104, thereby to interrupt a further point in the previously traced circuit for energizing the winding of the sender start relay R040;

the sender start relay R040 then restores shortly thereafter as it is of the slow-to-release type. Finally the equipment start relay R440 interrupts, at the contacts 440, the previously traced path for applying battery potential to the third marking conductor C005 individual to the third toll link 500 and extending to the signal sender I000.

.-Upon restoring, theswitch start relay R000 the latter relay to operate: the hold relay R025 remains operated during impulsing as it is of the slow-to-release t p Also each time the impulse relay R020 operates and restores it completes and then interrupts, at the'contacts 022, an obvious circuit for energizing the rotary magnet M0 l 4, whereby the latter magnet operates and restores. Hence, in the present example, the rotary magnet MM 4 is operated and restored three times, thereby to drivethe wipers noted of 'the lamp switch 0| 0 into eng sement with the third contacts in the associated contact banks. At this time the wipers 0H, "2 and "0 respectively select the conductors extending to the first, second and third operator positions at the control,