US2298751A - Telephone system - Google Patents

Description

Oct. 13, 1942. 'rk F. cRocKER TELEPHONE SYSTEM Filed sept. es,y 1940 9 Sheets-Sheet l Oct. 13,' 1942.

'rf F. `czRoCKER TELEPHONE SYSTEM Filed Sept. 6, 1940 9 Sheets-Sheet 2 o .EO

rlll| NoN f mz... .3E

INVENTOR THOMAS F. CROCKER ,of ,MM ATTORNEYS Oct. V13, 1942. T. F. cRQKER TELEPHONE SYSTEM 9 Sheets-Sheet 3 l Filed; sept. 6, 1940 v z: N B22 o I\ r) T8 awww..

w .MEQ

lh VENT OR THOMAS F, cRocKER B Y E gz E Ou/lmp? 'ATTORNEYS Oct. 13, 1942. r. F. cRocKER 2,298,751v

TELEPHoNa'sYhsTEM Filed sept. e, 1940 9 sheets-sheet 4 I DIST AEX.

I DE-2 INVENTOR THOMAS F CRQCKER BY y 9mm M p( @ATTORNEYS Oct. 13, 1942.` T. F. cRocKl-:R

TELEPHONE SYSTEM Filed Sept. 6, 1940 9 Sheets-Sheet 5 INVENTOR THOMAS F.GROCKER v y BY ATTORNEYS T. F. cRocKER TELEPHONE SYSTEM Oct. 13, 1942.

9 Sheets-#Sheet 6 Filed Sept. 6, 1940 TTORNEYS 0ct. 13,- 1942, T. F. cRocKER 2,298,751

TELEPHONE SYSTEM Filed Sept. 6, 1940 9 Sheets-Sheet '7 LINK FINDER SENDER SEL. LF-I SS-I INVENTOR THOMAS F. GROGKER ATTORNEYS Oct. 13, 1942. T. F. cRocKER TELEPHONE SYSTEM 9 Seets-Sheet 8 Filed Sept. 6, 1940 OON msg

TO VARIOUS TOLL 8 TRUN( GIRS;

INVENTOR THOMAS F. cRocKER ,M m ATTQRNEYSy T. F. czRocKER 2,298,751

TELEPHQNE SYSTEM Filed sept. 6,' 1940 9 sheetssheet 9 |NVENTOR THOMAS F. cRocKER ATTORNEYS T m T Ew Ex oct. 13, 1942.4

Patented Det. 13, 1942 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Application September 6, 1940, Serial No. 355,630

V(Cl. 179-27) 20 Claims.

The present invention relates to telephone systems and, more particularly, to improved automatic switching apparatus of the character of that disclosed in U. S. Patent No. 2,167,710, Thomas li'. Crocker, granted August l, 1939, which apparatus is connected and arranged to handle switchboard traino.

The telephone system disclosed in the abovementioned Crocker patent comprises lan automatic switchboard including a number of operator positions, including a group of inward or Ytoll operator positions, a group of combined line and recording or C. L. R. operator positions and a group of delayed or point-to-point operator positions, at which the corresponding types of switchboard traino 4are handled. More particularly, each operator position comprises a group of links individual thereto and apparatus for selectively controlling the links in the associated group; whereby calls may be answered, extended; supervised yand released by way of the links in the associated group and the various control functions may be performed in conjunction with the calls by way of the links in the associated group.

Also, the system comprises distributor apparatus which is governed in response to the manual preparation for use of an idle link at a given operator position for selecting the given operator position to answer the next incoming call and which is then governed in response to the arrival of a call for routing the call to the given operator position to be answered.

While a telephone system of the type described is entirely satisfactory in operation and extremely efficient when the switchboard is re1- atively large, it requires a larger number oi operator positions at the switchboard and more attention of the operators thereat than is desirable, particularly when` the switchboard is relatively small.

Accordingly, it is an object of the present invention to provide in a telephone system comprising a switchboard including a number of universal operator positions, each operator position being adapted to handle the different types of switchboard trafc, an improved distributor 'arrangement for routing the different types of calls to the various operator positions at the switchboardto be answered.

Another object of the invention is to provide in a telephone system comprising a switchboard including a number of operator positions, an improved distributor arrangement for automatically r in a telephone system comprising an operator position including a number of links, an improved distributor arrangement for routing calls over idle ones of the links to the operator position, which requires no special conditioning ci routing calls to idle ones of the operator posi- 55 the links by the operator at the operator position.

A further object of the invention is to provide in a telephone system comprising an operator position including a number of links, an irn- 'proved arrangement which may be selectively controlled both automatically, by distributor equipment, and manually, by the operator at the operator position, for routing calls over idle ones of the links to the operator position.

A still further object of the invention is to provide in a telephone system comprising an operator position including a plurality of links, an improved arrangement for extending calls by way of the links to the operator position and for extending calls by Way of the links from the operator position and for controlling the supervision at the operator position of calls extended by way of the links.

'I'he invention is illustrated as being embodied in a telephone system comprising a central ofiice terminating various groups of trunk and toll lines and provided with a switchboard including a number of operator positions. Also, the central oce comprises automatic switching apparatus including a number of groups of links individually associated with the operator positions at the switchboard.

In accordance with one feature oi the invention, the telephone system comprises a distributor arrangement including a position distributor operative to select the ones of the groups of links 'associated with idle ones of the operator positions in a predetermined order, and a plurality of link distributors individually corresponding to the groups of links and respectively operative to select idle ones of the links in the associated group of links in a predetermined order. Also, the distributor arrangement comprises means responsive to the presence of a call on any one of the lines for connecting a selected one of the links in a selected one of the groups of links to the 'associated one of the operator positions and to the calling line, thereby to extend the call on the calling line to the one operator position to be answered. Further, the system comprises means controllable from the one operator position for connecting the one link to a called one of the lines, thereby to complete a connection between the calling line and the called line, means controlled when the one link is connected to either the calling line or the called line for rendering busy the one link, means for disconnecting the one link from the operator position, and means controlled when a busy one of the links is connected to the operator 'position for rendering busy the operator position.

In accordance with another feature of the invention, the system comprises additional means controllable from the one operator position for connecting an idle one of thelinks in the associated group to the one operatorxposition and to a calling one of the lines, thereby to extend the call on the calling line to the one operator position to be answered, whereby the call on a calling line may be routed to the one operator-position, either under the automatic control ofthe distributor arrangement or under the manual control of the operator at the one operator position.

In accordance with a further feature of the invention, each link comprises an answer switch having access to calling lines and a call switch having access to called lines; and each operator position comprises position apparatus selectively operative to answer, to extend, to supervise and to release, by way of the links in the associated group, the various calls, and to perform, in conjunction with the calls, by way of the links in the associated group, various control and supervisory functions.

Further features of the invention pertain to the particular arrangement of the circuit elements of the system, whereby the above-outlined and additional operating 'features are attained.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method -of operation, tgether 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 t0 9, inclusive, taken together, illustrate the details of a system having incorporated therein the features of the invention, as briefly outlined above; and Fig..10 illustrates the mode 0f combining Figs. 2 to 9, inclusive, to form a unified system.

Description of the apparatus incorporated in the telephone system Referring now more particularly to Fig. 1 of the drawings, the telephone system there illustrated comprises a central office CO and two distant exchanges DE--I and DEP-2. The central oilice CO and each of the distant exchanges DE-I and DE-2 serve a number of local subscriber substations, the central office CO serving the local subscriber substations T-l and T-Z respectively associated with the subscriber lines 20| and 406. The central oflice CO and the distant exchange DE-I are interconnected by a group of two-way toll lines, including the toll line indicated at 'IL-I; similarly, the central oice CO and the distant exchange DE--Z are interconnected by a group of two-way toll lines, including the toll line indicated at 'TL-2. It is noted that the toll line TL-I extending between the central oflice CO andthe distant exchange operator position OP-l DE--l terminates at an operator position 2|0 in the distant exchange DE-|; similarly, the toll line 'IL-2 extending between the central oice CO and the distant exchange DE-Z terminates at an operator position 4|0 in the distant exchange DE-2. Each of the toll lines extending to the central office CO terminates in a toll line circuit, the toll line TL-l terminating in the toll line circuit TLC-I.

The central office CO is of the automatic type, while the distant exchanges DE-I and DE-Z may be of any suitable type. Accordingly, the central oflice CO is provided with a local switch train, including the portions LST-I and LST- 2,

" each comprising a plurality of groups of finders,

selectors and connectors of the Strowger type arranged in the usual manner in order to set up the various connections between the local subscriber substations in the central office C'O.

Also, a group of combined line and recording or C. L. R. trunks, including the C. L. R. trunk 205, is provided in the central oice CO, which trunks are accessible to the local switch train LST-I. Furthermore, a C. L. R. trunk circuit is individually associated with each C. L. R. trunk, the C. L. R. trunk circuit CLRf-I being individually associated with the C. L. R. trunk 205.

Further, the central office C'O is provided with a toll switch train comprising a plurality of groups of finder-selector links, one of the groups including the link illustrated which comprises the finder F-I and the toll first selector TFS-I a group of toll delayed selectors, including the toll delayed selector TDS-l and a group of toll switches indicated at TST. Preferably, the switches are of the Strowger type and are connected and arranged in a manner more fully described subsequently.

An automatic dial switchboard is arranged in the central office CO and comprises a number of 'operator positions, each operator position having a group of finder-selector links individually associated therewith. For example, the nderselector link illustrated is included in the group of links individually associated with the first at the switchboard. Each of the finders of the finder-selector links has access to each of the C. L. R. trunks in the central oiiice CO, to each of the toll lines extending between they central ofiice CO and the distant exchanges DE-I and DE-Z, to each toll delayed selector and to a group of interposition transfer trunks individual to the associated operator position. For example, the group of interposition transfer trunks, including the interposition transfer trunk 40|, is individual to the first operator position OP-I and is utilized for the purpose of transferring calls from other operator positions at the switchboard to the first operator position OP-I thereat. Also, it is noted that an interposition transfer circuit is individually associated with each interposition transfer trunk, the interposition transfer circuit ITC-l being individually associated with the interposition transfer trunk 40|. More specically, the finder F-I of the finder-selector link illustrated has access to the C. L. R. trunk 205 by way of the trunk line 203, to the toll line TL| by way of the trunk line 202, to the toll delayed selector TDS- l by way of the trunk line 206, and to the interposition transfer trunk 40| by way of the trunk line 204. Furthermore, the nder F-l is accessible to the trunk circuit at the first operator position OP-l by way of the cable #1.

Also, each toll first selector and each toll delayed selector have access to each of the interposition transfer trunks, tothe toll switch train TST and to the local switch train LST- 2. More specifically, the toll first selector TFS-I and the toll delayed selector TDS-I each have access to the interposition transfer trunk 40| directly, to the toll switch train TST by way of the trunk line 402, and to the local switch train LST- 2 by way of the trunk line 403. Also, it is noted that the toll switch train TST has access to each of the toll lines extending between the central office CO and the distant exchanges DE| and DE-2. For example, the toll switch train TST has direct access to the toll line TL-2 extending between the central office CO and the distant exchange DE--2.

Preferably, each of the operator positions, including the rst operator position OP-I at the switchboard in the central office CO, is of the universal type, thereby making it possible to render toll, C. L. R. and point-to-point service at each operator position. Also, the central ofce CO comprises a position distributor PD and a group of link distributors individually corresponding to the operator positions at the switchboard. For example, the group of link distributors includes the first position link distributor LD-l individually associated with the rst operator position OP--I at the switchboard. The position distributor PD is so connected and arranged that idle ones of the operator positions at the switchboard are selected in a predetermined order to answer calls; while each link distributor is so lconnected and arranged that idle ones'of the iinder-selector links at the associated oper- -ator position are selected in Va predetermined order `for use in routing calls to be answered.

Also,` individually associated with each operator position vis a sequence control circuit SCC which has access to two individually associated sender links SL-I and SL-2. Furthermore, at each operator position, there is provided a group of operator digit keys DK individual thereto which is associated with each of the sender links SL-l and SL-Z. Finally, a group of register senders, including the register sender RS, is commonly associated with the switchboard. Each of the sender links comprises -a link nder and a sender selector, the sender links SL-l and SL-Z respectively comprising the link finders LF-l and LF--Z and the sender selectors SS-I and SS-2. Each of the link finders has access tothe trunk circuit at the associated operator position by way of cable #3 and to each linderselector link at the associated operator position by way of cable #2; similarly, each of the sender selectors has access to each of the register senders by way of cable #4. v

Preferably, each of the toll line circuits, such as TLC-4, shown in Fig. 2, is identical to that disclosed in Fig. 2 of the previously mentioned Crocker patent; each of the combined line and recording trunk circuits, such as CLR-l, shown in Fig. 2, is identical to that disclosed in Fig. 3 f the previously mentioned Crocker patent; and each of the interposition transfer circuits, such as ITC-l, shown in Fig. 2, is identical to that disclosed in Fig. 5 of the previously mentioned Crocker patent.

The position distributor PD comprises, as best shown in Fig. 8, a start relay |2|,0, a reset relay |220, a hold relay |225, three select relaysl230, |235 and |240, respectively corresponding to the first, second and third operator positions at the switchboard, and a control network.

Preferably, each of the link distributors is identical to the rst position link distributor LD| which comprises, as best shown in Fig. 8, a reset relay |245, a hold relay |250, three select re- I lays |255, |260 and |265 individually correspondsender RS, shown in Fig. 7, is identical to that disclosed in Figs. 1'7 to 21, inclusive, ofthe previously mentioned Crocker patent.

Preferably, each of the operator positions at the switchboard is identical to the first operator V,position OP|, shown in Figs. 5, 6 and 9, which operator position is substantially identical to that disclosed in Figs. 11, 13 and 14 of the previously mentioned Crocker patent. More particularly, the first operator position OP-I comprises position telephone equipment, a group of position relays and a position key set. More particularly, the position key set comprises a delay call key K-3, a cut-off answer key K-5, a transfer answer key K-B, a ring answer key K-|, a release answer key K-8, a dial answer key K-9, an emergency start key K|0, a release answer land call key K-I I, a release call key K-|2, a ring call key K-|3, a transfer call key K-H, a cut-off call key K-I5, a without key K-|0, a position group key K--I and a busy key K-IB; while the position telephone equipment comprises a headset, a talking repeater TR and a monitoring repeater NLR.. The group of position relays comprises a transmitter supply relay I0, a monitor relay H20, a talk relay H30, a call signal relay H40, two signal interrupter relays H and H60, a start relay H10, a split answer relay |3|0, a split call relay |320, a transfer relay |330, an answer pilot relay |340, a call pilot relay |350, an error relay |360, two supervisory relays |300 and |310, a call relay |380 and a cut-through relay |390. rCertain of the relays mentioned are connected and arranged for the purpose of controlling the =association of the headset at the iirst operator lposition OP-I with the trunk circuit thereat; while other of the relays mentioned are so connected and arranged that they control the transmission of tone to the receiver of the headset at the first operator position OP--l when an incoming call is routed thereto. Finally, the remainder of the relays mentioned are so connected and arranged that various types of toll and trunk -calls may be initiated, answered, released and supervised from the rst operator position OP-I, in a manner more fully described subsequently.

As previously noted, a group of finder-selector links is individually associated with each operator position, the finder-selector link illustrated comprisingthe finder F-I, shown in Fig. 3, and the toll rst selector TFS-L shown in Fig. 4, being included in the group of finder-selector links individually associated with the rst operator position OP-l. Preferably, each of the f finder-selector links is identical to the finderselector link illustrated, the nder F--I of this link being operatively associated with cable a# 1 extending to the trunk circuit at the `first operator position OP--|.

The finder F|, shown in Fig, 3, corresponds to that shown in Fig. 6 of the previously mentioned Crocker patent and comprises a switching mechanism of the ZOO-point Strowger type including a wiper carriage capable of both vertical and rotary movements, a vertical magnet for moving the wiper carriage in the vertical direction, a rotary magnet for moving the Wiper carriage in the rotary direction and a release magnet for releasing the wiper carriage and for causing it to be returned to its normal position. Also, the lnder F| comprises a group of relays, including two electropolarized relays 6 0 and 620, a change-over relay 630, a step relay 640, a supervisory relay 650, a start relay 660, a connect relay 010, a cut-through relay 630, an automatic start relay 000 and an automatic answer relay 505. Moreover, the finder F-I has individually associated therewith at the first operator position OP-l a link listening or talk key K-I and a monitoring key K-Z which are operative to associate the nder F-I with cable #1 extending to the rst operator position OP-l. Finally, a number of lamps, including a call lamp 60|. an answer lamp 602 and a link-busy lamp 603 are associated with the finder F-l for supervisory purposes.

The toll rst selector TFS-I, shown in Fig. 4, is identical to that disclosed in Fig. 7 of the previously mentioned Crocker patent. Preferably, each of the toll delayed selectors is identical to the toll delayed selector TDS-I, shown in Fig. 4, which is in turn identical to the toll rst selector TFS-I, shown in Fig. 4. Also, the apparatus at the operator positions 2| 0 and 4|0, respectively shown in Fig. 2 and Fig. 4 and respectively disposed in the distant exchanges DE--I and DIE-2, is entirely conventional; and each subscriber substation in the central oflice CO is provided with conventional automatic subscriber substation equipment.

A better understanding of the connection and arrangement of the apparatus incorporated in the telephone system will be facilitated from a consideration of the detailed operation of the various pieces of apparatus incident to the handling of the various toll and trunk calls at the switchboard, as will appear hereinafter,

Operations of the position distributor and *he Zink distributors Considering now the operation of the position distributor PD, when the first operator position OP-l at the switchboard is idle, this position being idle when the operator thereat is not engaged in answering or extending a call and when there are idle links in the associated group of links, no ground potential appears upon the guard conductor |210 of the iirst operator position OP-I in cable #1. On the other hand, when the first operator position OP-I at the switchboard is busy, due either to the fact that the operator thereat is engaged in answering or extending a call, or the fact that all of the links in the associated group are busy, ground potential appears upon the guard conductor |210 of the rst operator position OP-I in cable #1. Similarly, ground potential appears upon the guard conductors |212 and |214, respectively, when the intermediate and last operator positions at the switchboard are busy. Thus, when one of the operator positions is idle, one of the select relays |230, |235 or |240, together with the hold relay |225, are operated.

Assuming that the first operator position OP-l is idle and that the position distributor PD has operated to select the first operator position OP-l at this time, a circuit is completed for energizing in series the winding of the hold relay |225 and the upper winding of the select relay |230. The last-mentioned circuit extends from ground by way of the contacts |22|, the winding 0f the hold relay |225, the contacts |236 and |232 and the upper winding of the select relay |230 to battery. The operated hold relay |225 retains interrupted, at the contacts |226, a p-oint in an obvious circuit for energizing the lower winding of the select relay |230.` The operated select relay |230 retains completed, at the contacts |232, the previously traced holding circuit for energizing the upper winding thereof in series with the winding of the hold relay |225. Also, the operated select relay |230 retains interrupted, at the contacts |23 a point in a holding circuit substantially identical to that previously traced for energizing the upper winding of the select relay |240 in series with the winding of the hold relay |225, and retains prepared, at the contacts |233, a circuit traced hereinafter for energizing the lower winding of the select relay |235. Finally, the operated select relay |230 retains completed, at the contacts |234, an obvious connection between the common link start conductor 290 and the individual link start conductor |21|, the individual link start conductor |21| extending to the lirst position link distributor LD-I.

When the rst operator position OP| is rendered busy, ground potential is applied to the guard conductor |210 thereof in cable #1, thereby to complete an obvious circuit for energizing the lower winding of the select relay |235 in order to cause the latter relay to operate. Upon operating, the select relay |235 completes, at the contacts |231, an obvious holding circuit substantially identical to that previously traced for energizing the upper winding thereof in series with the winding of the hold relay |225, interrupts, at the contacts |236, the previously traced holding circuit for energizing the upper winding of the select relay |230 in series with the winding of the hold relay |225 in order to cause the select relay |230 to restore, prepares, at the contacts |238, an obvious circuit for energizing the lower winding of the select relay |240, and completes, at the contacts |239, an obvious connection between the common link start conductor |290 and the individual link start conductor |213, the individual link start conductor |213 extending to the intermediate position link distributor, not shown.

In the event the intermediate operator position is idle, further operation of the position distributor PD is arrested, whereupon the intermediate operator position is selected at this time. On the other hand, in the event the intermediate operator position is busy at this time, ground potential appears upon the guard conductor |212 thereof, thereby to complete the previously mentioned circuit for energizing the lower winding of the select relay |240, in order to cause the latter relay to operate; whereupon the last operator position is selected in the event it is idle at this time, in the manner previously explained.

In the event the last operator position is busy at this time, ground potential appears upon the guard conductor |214 thereof, thereby to complete an obvious circuit for energizing the winding of the reset relay |220. When thus energized, the reset relay |220 operates to interrupt, at the contacts |22I, the previously mentioned holding circuit for energizing the upper winding of the select relay |240 in series with the winding of the hold relay |225, thereby to cause the select relay |240 to restore immediately and the hold relay |225 to restore shortly thereafter, the hold relay |225 being of the slow-to-release type. Upon restoring, the select relay |240 interrupts, at the contacts |243, the previously mentioned circuit for energizing the winding of the reset relay |220, thereby to cause the latter relay to restore shortly thereafter, the reset relay 220 being of the slow-to-release type. Upon restoring, the reset relay |220 completes, at the contacts |22|, an obvious circuit for energizing the lower winding of the select relay |230, thereby to cause the latter relay to operate and complete, at the contacts |232, the previously traced holding circuit for energizing the upper winding thereof in series with the Winding of the hold relay |225. When thus energized, the hold relay |225 operates to interrupt, at the contacts |226, the previously mentioned circuit for energizing the lower winding of the select relay |230.

In view of the above description of the mode of operation of the position distributori PD, it will be understood that idle ones of the operator positions at the swtichboard are selected thereby in a predetermined order.

Considering now the operation of the first position link distributor LD-I, when the first link, the link illustrated, at the rst operator position OP-I is idle, no ground potential appears upon the guard conductor |28| of the first link in cable #1. On the other hand, when the rst link at the first operator position OP-I is busy, ground potential appears upon the guard oo nductor |28I of the rst link in cable #1. Similarly, ground potential appears upon the guard conductors |283 and |285, respectively, when the intermediate and last links at the rst operator position OP-I are busy. Thus, when one of the links at the first operator position OP-I is idle, one of the select relays |255, |260 and |265, together with the hold relay |250, are operated.

Assuming that the first link at the rst operator position OP-I is idle and that the first position link distributor LD-I has operated to select the rst link at the first operator position OP--I at this time, a circuit is completed for energizing in series the winding of the hold relay' |250 and the upper winding of the selectJ relay |255. The last-mentioned circuit extends from ground'by way of the contacts |241, the Winding of the hold relay |250, the contacts |262 and |258 and the upper winding of the select relay |255 to battery. The operated hold relay |250 retains interrupted, at the contacts |25|, a point in an obvious circuit for energizing the lower winding of the select relay |255. The operated select relay |255 retains completed, at the contacts |258, the previously traced holding circuit for energizing the upper winding thereof in series with the winding of the hold relay |250. Also,

`the operated select relay |255 retains interrupted,

at the contacts |251, a point in a holding circuit substantially identical to that previously traced for energizing the upper winding of the select relay |265 in series with the winding of the hold relay |250, and retains prepared, at the contacts |250', a circuit tracedl hereinafter for energizing the lower winding of y the select relay |260. Finally, the operated 'select relay |255 retains completed, at thecontacts |256, an obvious connection between the individuallink start conductor |21| extending between the position distributor PD and the first position link distributor LD-I and the `start conductor |282 extending tothe first link at the rst operator position OP-l.

When the first link at the rst operator position OP-I is rendered busy, ground potential is applied to the guard conductor |28| thereof in cable #1, thereby to complete an obvious circuit for energizing the lower winding of the select relay |260 in order to cause the latter relay to operate. Upon operating, the select relay |260 completes, at the contacts |263, an obvious holding circuit substantially identical to that previously trace-d for energizing the upper winding thereof in series with the Awinding of the hold relay |250, interrupts, at the contacts |262, the previously traced holding circuit for energizing the upper winding of the select relay |255 in series with the winding of the hold relay 250 in order to cause the select relay |255 to restore, prepares, at the contacts |264, an obvious circuit for energizing the lo-Wer winding of the select relay |265, and completes, at the contacts |26|, an obvious connection between the individual link start conductor |21|, extending between the position distributor PD and the rst position link distributor LD'-|, and the start conductor |284 extending to the intermediate link at the first operator position OP|.

In the event the intermediate link at the rst operator position OP-I is idle, further operation of the rst position link distributor LD| is arrested, whereupon the intermediate link at the rst operator position OP--I is selected at this time. On the other hand, in the event the intermediate link at the rst operator position OP-l is busy at this time, ground potential appears upon the guard conductor |283 thereof, thereby to complete the previously mentioned circuit for energizing the lower winding of the select relay |265, in order to cause the latter relay to operate; whereupon the last link at the first operator position OP-I is selected in the event it is idle at this time, in the manner previously explained.

In the event the last link at the first operator position OP-I is` busy at this time, ground potential appears upon the guard conductor |285 thereof, thereby to complete an obvious circuit for energizing the winding of the reset relay |245. When thus energized, the reset relay |245 operates to interrupt, at the contacts |241, the previously mentioned holding circuit for energizing the upper winding of the select relay |265 in series with the winding of the hold relay |250, thereby to cause the select relay |265 to restore immediately and the hold relay |250 to restore shortly thereafter, the hold relay |250 being of the slow-to-release type. Upon restoring, the select relay 265 interrupts, at the contacts |261, the previously mentioned circuit for energizing the Winding of the reset relay |245, thereby to cause the latter relay to restore shortly thereafter, the reset relay |245 'being of the slow-torelease type. Upon restoring, the reset relay |245 completes, at the contacts |241, an obvious circuit for energizing the lower winding of the select relay |255, thereby to cause the latter relay to operate and complete, at the contacts |258, the previously traced holding circuit for energizing the `upper winding thereof in series with the winding of the hold relay |250. When thus energized, the hold relay |250 operates to interrupt, at the contacts |25I, the previously mentioned circuit for energizing the lower winding of the select relay |255.

In View of the above description of the mode of operation of the first position link distributor LD-l, it will be understood that idle ones of the links at the lirst operator position OP-l are selected thereby in a predetermined order. Furthermore, it will be understood that the intermediate position link distributor and the last position link distributor operate in a manner identical to that of the first position link distributor LD-i, described above.

Also, itis noted that when the first operator position at the switchboard is busy, due either to the fact that the operator thereat is engaged in answering or extending a call or the fact that all of the links in the associated group are busy, the application of ground potential to the guard conductor |220 thereof in cable #1 completes an obvious circuit for energizing the winding of the reset relay l2|5 in the first position link distributor LID- i. When thus energized, the reset relay |265 operates to reset the first position link distributor LD-l, in the manner previously explained. Also, the reset relay |245 prepares, at the contacts IZeS, a point in a chain circuit for energizing the winding of the reset relay |220 in the position distributor PD. The above-mentioned chain circuit is completed when the reset relay in each of the link distributors is operated, thereby to cause operation of the reset relay |220 in the position distributor PD, in the manner previously explained. Thus, it will be understood that, when all of the links in the group associated with a given operator position are busy, the operation oi the associated link distributor is arrested; and that when all of the operator positions at the switchboard are busy, the operation of the position distributor PD is arrested.

Extension of a call from a local subscriber substation in the central oce to the switchboard therein in order to establish a connection between a local subscriber substation in the central oliice CO, such as the subscriber substation T-l, and

the switchboard, the subscriber at the subscriber substation T-l first initiates a call in the regular manner, thereby to cause the local switch train LST-l to seize the subscriber line extending to the subscriber substation T-I, in a conventional manner. The subscriber at the subscriber substation T-l then dials a predetermined digit or digits into the local switch train LST-I, thereby to cause the local switch train LST-l to operate and seize an idle C. L. R. trunk, such as the C. L. R. trunk 205. When the C. L. R. trunk 205 is thus seized, the combined line and recording trunk circuit CLR-I individually associated therewith operates, thereby to cause ground potential to be applied to the start conduotor SIS and to cause the trunk line 203 extending thereto to be marked for selection. The application of ground potential to the start conductor 3|3 completes, by way of a corresponding one of the start leads |200, an obvious circuit for energizing the winding of the start relay |2|0 in the position distributor PD. Assuming that the position distributor PD has preselected the rst operator position OP-I at the switchboard and that the first position link distributor LD-I has preselected the first link at the rst operator position OP-I, the call from the subscriber substation T-l is routed to the first operator position OP-l at the switchboard by way of the first link in the associated group. More particularly, upon operating, the start relay |2|0 completes,

- associated group at this time.

at the contacts l2 I2, a path for applying ground potential to the start conductor |282 of the first link at the first operator position OP-I at the switchboard in cable #1, this path extending from ground by way of the contacts |2I2, the common link start conductor |200, the contacts |234, the individual link start conductor |2H, and the contacts |256 to the start conductor |282 of the first link at the first operator position OP-I at the switchboard in cable #1. Also, the start relay |2I0 completes, at the contacts |2| obvious multiple circuits for illuminating the answering lamps |204, etc., at the various operator positions at the switchboard, thereby to indicate the presence of an unanswered call to the operators thereat.

The application of ground potential to the start conductor |282 in cable #l completes a circuit for energizing the winding of the automatic start relay 600 in the finder F-|, this circuit extending from the grounded start conductor |282 by way of the contacts 621 and 6|`| and the winding cf the automatic start relay 600 to battery. When thus energized, the automatic start relay 600 opcrates t0 complete, at the contacts 602, a circuit for energizing the lower Winding of the connect relay B70, this circuit extending from ground by way of the contacts H33, the test conductor B04 in cable #1, the contacts 602 and the lower winding of the connect relay 610 to battery. When thus energized, the connectrelay 610 operates to complete, at the contacts 619, a holding circuit for energizing the upper winding thereof in series with the winding of the talk relay H30, this circuit extending from ground by way of the winding of the talk relay |30, the hold conductor 605 in cable #1, the contacts 60| and 619 and the upper winding of the connect relay 610 to battery. When this holding circiut is completed the talk relay H30 operates shortly thereafter, this relay being of the slow-to-operate type, to complete, at the armatures H3| and H32 and the front contacts associated therewith, an obvious connection between the tip conductor and the ring conductor H8| of the trunk circuit at the rst operator position OP-l and the talking repeater TR. thereat, thereby operatively to associate the operator headset at the first operator position OP-I with the tip conductor'l |80 and the ring conductor H8| of the trunk circuit thereat. Also,

^ the talk relay H30 interrupts, at the contacts |33, the previously traced circuit for energizing the lower winding of the connect relay 610, thereby positively to prevent the operation of the connect relay in the nder of any other link in the Further, the talk relay H30 completes, at the contacts H35, a circuit for energizing the winding of the start relay H70, this circuit extending from ground by way of the contacts H35, the conductor H85, the contacts |35! and |343, the conductor H84, the winding of the start relay H10 and the contacts of the delay call key K-3 to battery. When thus energized, the start relay H'l'0 operates shortly thereafter, this relay being of the slow-to-operate type, to prepare, at the contacts H'H, a point in a circuit traced hereinafter for energizing the winding of the call signal relay H40.

Also, upon operating, the automatic start relay 600 completes, at the contacts 604, a circuit for energizing the upper winding of the automatic answer relay 605, this circuit extending from ground by way of the contacts 604, the upper winding of the automatic start relay 605 and the resistor R1 to battery. When thus energized, the

automatic answer relay 605 operates to complete, at the contacts 606, an obvious holding circuit for energizing the lower winding thereof, including the resistor R1. Also, the automatic answer relay 635 completes, at the contacts 601, an obvious circuit for illuminating intermittently the linkbusy lamp 603 by way of the interrupter 600, thereby to cause the link-busy lamp 603 to flash. The hashing link-busy lamp 603 indicates to the operator at the rst operator position OP-I that a call is being extended to the rst operator position OP-I by the position distributor PD and the first position link distributor LD-l by way of the rst link in the associated group.

Also, upon operating, the connect relay 610 completes, at the contacts 612 and 614, an obvious connection between the finder F-I and the ring answer conductor 654 and the tip answer conductor 653, respectively, in cable #1, the ring answer conductor 654 and the tip answer conductor 653 being respectively connected by the armatures |3|2 and |3|| and the back contacts4 associated therewith to the ring conductor ||8| and the tip conductor H80, respectively, of the trunk circuit at the rst operator position OP| at the rst operator position OP--I is operatively connected to the nder F--|. Also, the connect relay 6'i0 interrupts, at the armature 615 and the back contact associated therewith, an obvious path for applying ground potential to the marking conductor |551 in the cable #2, thereby to mark the rst link at the rst operator position OP--l as a calling link to the link nder of the selected sender link, for a purpose more fully explained hereinafter.

Also, upon operating, the automatic start relay 600 completes, at the contacts 603, an obvious circuit for energizing the winding of the start relay 660, thereby to cause the latter relay to operate. Upon operating, the start relay 660 interrupts, at the contacts 66|, a point in an obvious circuit for energizing the release magnet of the iinder F-I, and completes, at the contacts 663, obvious multiple circuits for energizing the lower windings of the electropolarized relays 6|0 and620. Also, the start relay 560 completes, at the -contacts 663, a circuit for energizing the vertical magnet, this circuit extending from ground by way ofthe contacts 663, 625, 6|5 and 64|, the armature 635 and the back contact associated therewith and the vertical magnet to battery. When thus energized, the vertical magnet operates to drive the wiper carriage of the nder F-I one step in the vertical direction, and to complete, at the contacts 698, an obvious circuit for energizing the winding of the step relay 540. When thus energized, the step relay 640 operates to interrupt, at the contacts 64|, the previously traced circuit for energizing the vertical magnet, thereby to cause the vertical magnet to restore. Accordingly, the step relay 640 and the vertical magnet interact in the manner described above, thereby to cause the wiper carriage of the finder F-l to be driven step by step in the vertical direction until the control wiper 6|1 engages the contact in the associated contact bank terminating the start lead |200 marked by the application of ground potential to the start conductor 3|3 in the combined line and recording trunk circuit CLR-I When the wiper carriage of the nder F| is operated to the level terminating the trunk line 203 extending to the combined line and recording trunk circuit CLR-I, the control wiper 6|1.en

Accordingly, at this time, the operator headset '25 gages a contact in the associated contact bank having ground potential thereon, as previously noted, whereupon an obvious circuit is completed for"energizing the lower winding of the changeover relay 630 in series with the winding of the step relay 640 when the vertical magnet restores. Shortly after the change-over relay 630 is thus energized this relay operates, the changeover relay 630 being of the slow-to-operate type, to complete, at the contacts 632, a holding circuit for energizing the upper winding thereof, this circuit extending `from ground by way of the upper winding of the change-over relay 630, the off-normal springs 645, the post normal springs 646, the contacts 632 and the resistor R4 to battery. Also, the change-over relay 630 interrupts at the armature 635 and the back contact associated therewith, the previously traced circuit for energizing the vertical magnet, and completes, at the armature 635 and the front contact associated therewith, a circuit substantially identical to that previously traced for energizing the rotary magnet, whereupon the rotary magnet and the step relay 640 interact in a manner similar to that previously explained, thereby to drive the wiper carriage of the nder F-I stepV by step in the rotary direction.

When the wiper set 6|8 carried by the wiper carriage of the nder F-l engages the contact in the associated contact bank terminating the trunk line 203 extending to the combined line and recording trunk circuit CLR- L a circuit is completed for energizing the upper winding of one of the electropolarized relays 5|0 or 620, depending upon which one hundred line group includes the trunk line 203, in a well-known manner. Assuming that the trunk line 203 is included in the first one hundred line group, a circuit is completed for energizing the upper winding of the electropolarized relay 6|0 in series with the lower winding of the supervisory relay 650, this circuit extending from ground by way of the contacts 634, the lower winding of the supervisory relay 650, the armature 623 and the back contact associated therewith, the upper winding of the electropolarized relay 6|0 and the control wiper CI of the wiper set 6|8 carried by the wiper carriage of the finder F--l to the control conductor of the trunk line 203, battery potential being present upon the control conductor of the trunk line 203. When thus energized, the electropolarized relay 6|0 operates exceedingly fast due to the previously completed circuit for energizing the lower winding thereof to complete, at the contacts 6|4, an obvious holding circuit for energizing the intermediate winding thereof, and to interrupt, at the contacts 6|5, the previously mentioned circuit for energizing the rotary magnet in order to arrest further operation of the wiper carriage of the nder F-I at this time. Also, the electropolarized relay B|0 completes, at the contacts 6|| and 6|2, an obvious connection between the line conductors of the trunk line 203 seized by the line wipers of the wiper set 6|8 carried by the wiper carriage of the finder F-I and the ring answer conductor 654 and the tip answer conductor 653 in cable #1, and, consequently, an operative connection between the subscriber substation T-I and the headset at the rst operator position OP-|.

Incident to operation of the change-over relay 630, and prior to the operation of the electropolarized relay 6|0, a circuit is completed for energizing the winding of the answer pilot relay |340, this circuit extending from ground by way of the winding of the answer pilot relay |340, the release answer conductor 608 in cable #1, the contacts 616 and 632 and the resistor R4 to battery. When thus energized, the answer pilot relay |340 operates to complete, at the contacts |34|, an obvious circuit for energizing the winding of the call signal relay H40. When thus energized, the call signal relay H40 operates shortly thereafter, the call signal relay ||40 being of the slow-to-operate type, to complete, at the contacts I |43, an obvious circuit for energizing the winding of the signal interrupter relay ||50. When thus energized, the signal interrupter relay H50 operates shortly thereafter, this relay being of the sloW-to-operate type, to complete, at the contacts |52, an obvious circuit for energizing the winding of the signal interrupter relay H60. When thus energized, the signal interrupter relay H60 operates to complete, at the contacts H52, an obvious holding circuit for energizing the winding thereof. Also, upon operating, the signal interrupter relay H60 interrupts, at the armature H52 and the back contact associated therewith, the previously mentioned circuit for energizing the winding of the call signal relay H40, thereby to cause the latter relay to restore and interrupt, at the contacts H43, the previously mentioned circuit for energizing the winding of the signal interrupter relay H50, whereupon the latter relay restores. The sequential operation of the call signal relay ||40 and the signal interrupter relays ||50 and H60, and the subsequent sequential restoration of the call signal relay |40 and the signal interrupter relay H50, cause tone current applied to the call tone conductor ||9| alternately to be connected to and disconnected from the talking repeater TR, whereupon a distinct zip-zip tone is produced in the headset at the rst operator position OP-|, thereby to indicate to the operator thereat that the finder F-I is searching for the trunk line over which the call is routed and that the call will arrive at the rst operator position OP-I shortly thereafter.

Also, upon operating, the answer pilot relay |340 interrupts, at the armature |343 and the back contact associated therewith, the previously traced circuit for energizing the winding of the start relay |10; thereby to cause the latter relay to restore and interrupt, at the contacts ||1|, the previously mentioned holding circuit for energizing the winding of the signal interrupter relay H60, whereupon the latter relay restores. Further, the answer pilot relay |340 completes, at the armature |343 and the front contact associated therewith, a path for applying ground potential to the sequence control conductor |304 extending to the sequence control circuit SCC, this circuit extending from ground by way of the contacts H735, the conductor H85, the contacts |35|, the armature |343 and the front contact associated therewith and the contacts |362 and |393 to the sequence control conductor |304. This application of ground potential to the sequence control conductor |304 causes the sequence control circuit SCC to operate and select one of the sender links, such, for example, as the sender link SL-i. When the sender link SL-l is thus selected, operation of both the link finder LF-l and the sender selector SS-I is initiated. The link finder LF-I then operates to nd cable #2 extending to the rst link at the rst operator position OP-I; and the sender selector SS- operates tond a cable extending to an idle register sender, such, for example, as cable #4 extending to the register sender RS.

Continuing with the operation of the nder F-l incident to the operation of the electropolarized relay 6|0, it is noted that, upon operating, the electropolarized relay 5|0 also completes, at the contacts 6|8, a multiple holding circuit for energizing the upper winding of the connect relay 610 in series with the winding of the talk relay 30, this circuit extending from ground by way of the winding of the talk relay ||30, the hold conductor 605 in cable #1, the contacts 689|, 6|0 and 619 and the upper winding of the connect relay 610 to battery. Also, the electropolarized relay 6|!! interrupts, at the contacts 6H, the previously traced circuit for energizing the winding of the automatic start relay 600, thereby to cause the latter relay to restore. Upon restoring, the automatic start relay 600 interrupts, at the contacts 60|, the previously traced original holding circuit for energizing the upper Winding of the connect relay 610 in series with the winding of the talk relay H30; and interrupts, at the contacts 603, the previously mentioned circuit for energizing the winding of the start relay 660. However, the start relay 660 does not restore, at this time, due to a completed holding circuit for energizing the winding thereof, this circuit extending from ground by way of the armature |344 and back contact associated therewith, the start conductor |302 in cable #1, the contacts 611 and the winding of the start relay 660 to battery. Also, the automatic start relay 600 interrupts, at the contacts 604, the previously traced circuit for energizing the upper winding of the automatic answer relay 605. However, the latter relay does not restore at this time, due to the previously traced completed holding circuit for energizing the lower winding thereof.

Further, the electropolarized relay 6|0 completes, at the armature 6|3 and the front contact associated therewith, an obvious path for shortcircuiting the upper winding thereof, thereby to complete a path for applying ground potential to the control conductor of the Seized trunk line 203 extending to the combined line and recording trunk circuit CLR-l, this path extending from ground by way of the contacts 634, the lower winding of the supervisory relay 650, the armature 6|3 and the front contact associated therewith, and the control wiper Ci of the wiper set 6|8 carried by the wiper carriage of the finder F-I to the control conductor of the trunk line 203. This application of ground potential to the control conductor of the trunk line 203 causes the combined line and recording trunk circuit CLR-I to operate, thereby to remove ground potential from the start conductor 3|3 extending to the position distributor PD. When ground potential is removed from the start conductor 3|3, the previously traced original circuit for energizing the winding of the start relay |2| 0 in the position distributor PD is interrupted. Accordingly, at this time, the start relay |2| 0 restores in the event there are no other calls waiting to be answered at the switchboard, and remains operated in the event there are other calls to be answered at the switchboard.

Finally, the electropolarized relay 6|0 completes, at the contacts 6|9, an obvious path for applying ground potential to the guard conductor |28| of the first link at the first operator position OP-|, thereby to initiate further operation of the first position link distributor LD--I at this time; whereupon the first' position link distributor LD-I operates to preselect the next idle link at the first operator position OP-I, in the manner previously explained. Further, it is noted that, when ground potential is applied to the guard conductor |28| of the first link at the first operator position OP|, ground potential is also applied to the guard conductor |210 of the first operator position OP-I due to the connection between the guard conductorv |28| and the guard conductor |210, at the contacts 610 of the operated connect relay 610. The application of ground potential to the guard conductor |210 in cable #l initiates further operation of the position distributor PD; whereupon the position distributor PD operates to select the next idle operator position at the switchboard, in the manner previously explained.

In view of the above description of the operation of the nder F-I of the first link at the rst operator position OP-I to seize a calling trunk line in the rst one hundred line group accessible thereto, it will be readily appreciated that the finder F-l will operate, in a similar manner, to seize a calling line in the second one hundred line group accessible thereto. In the last-mentioned case, the electropolarized relay 620, instead of the electropolarized relay 6| 0, is operated in the iinder F-|, whereupon the subsequent operation of the finder F-l is the same as that previously explained.

At this time, an operative connection is completed between the calling subscriber substation T--I and the operator position telephone equipment at the rst operator position OP--L The sender link SL-l is operatively associated with the first link and with the register sender RS; and the operator digit keys DK are operatively associated with the sender link SL-I. Accordingly, at this time, the operator at the iirst operator position OP-I communicates with the calling subscriber at the subscriber substation T-l and is advised concerning the extension of the call; and the apparatus at the first operator position OP--I is in readiness to extend the call by way of the toll first selector TFS--I of the first link at the first operator position OP-I in the event this is necessary.

Extension of a caflZ from the switchboard in the central oice to a distant exchange Assuming that the incoming call from the call- After all of the digits registered in the register sender RS have been transmitted by the sender link SL-|, the sender link SL-I operates to cause battery potential to be connected to the control conductor |553 in cable #2 and ground potential to be connected to the control conductor |556 in cable #2 in the manner fully explained in the previously mentioned Crocker patent. The application of battery potential to the control conductor |553 in cable #2 causes the toll switch train TST to operate and transmit ringing current over the toll line TL-Z in orderv to signal the operator at the operator position 4|0 in the distant exchange DE2. The application of ground potential to the control conductor |556 in cable #2 completes an obvious circuit for energizing the upper winding of the cutthrough relay 680. When thus energized, the cut-through relay 680 operates to complete, at the contacts 685, an obvious holding circuit for energizing the lower winding thereof and to complete, at the contacts 63| and 682, a connection between the toll rst selector TFS--I and the operator position telephone equipment at the first operator position OP|. More particularly, the line conductor 11| of the trunk extending to the toll first selector TFS-l is connected by way of the contacts 68| and 61|, the'ring call conductor 655 in cable #1 and the armature |322 and the back contact associated therewith'to the ring conductor 8| of the trunk circuitat the first operator position OP-|; and the line conductor 112 of the trunk extending to the toll first selector TFS-I is connected by way of the contacts 682 and 613, the tip call conductor 656 in cable #1, and the armature 32| and the back contact associated therewith to the tip conductor |00 of the trunk circuit at the first operator position OP-I. Also, the cut-through relay 680 interrupts, at the contacts 689, the previously traced alternative holding circuit for energizing lay 610 interrupts, at the contacts 612 and 614,

ling subscriber substation T-I is to be extended to the distant exchange DE-2, the operator at the iirst operator position OP-I initiates the extension of the call by actuating the operator digit keys DK, as previously noted. More particularly, the operator digit keys DK are operated in order to cause the register sender RS to register a predetermined number of digits corresponding to the switch train route to the distant exchange DE--2. The register sender RS then operates, thereby to cause the sender link SL-I to transmit the digits registered over cable #2 to the toll rst selector TFS-I of the rst link at the first operator position OP-I. The toll first selector TFS-I operates to seize an idle trunk line, such as the trunk line 402 extending to the toll switch train TST. The remaining digits transmitted to the toll switch train TST cause the toll switch train TST to seize an idle toll line, such as the toll line TL-Z extending between the central oiice CO and the distant exchange DE--2, the toll line TL-2 terminating at the operator position 4|0 in the distant exchange DEI-2.

the previously traced connection between the calling subscriber substation T-l and the operator position telephone equipment at the rst operator position OP-|; interrupts,l at the contacts 61| and 613, the previously traced connection between the operator position telephone equipment at the first operator position OP-I and the toll first selector TFS--I of the first link at the first operator position; and completes, at

the armatures 612 and 614 and the back contacts associated therewith a direct connection between the calling subscriber substation T--I and the toll iirst selector TFS-I in the first link at the rst operator position OP-|, independently of the operator position telephone equipment at the first operator position OP-l More particularly, at Athis time, the line conductor 11| of the trunk extending to the toll first selector TFS--I is connected by way of the contacts 68|, the armature 612 and the back contact associated therewith, and the contacts 6|| to one of the line wipers of the wiper set 6| of the finder F-|; while the line conductor 112 of the trunk extending to the toll rst selector TFS-l is connected by way of the contacts 682, the armature 614 and the back contact associated therewith, and the contacts 6|2 to the other line wipers of he wiper set 6|8 of the finder F-L Accordingly, at this time, an operative connection ,is completed between the calling subscriber substation T-l and the operator position M inthe distant exchange DE-2.

Also, upon'restoring, theV connect relay 610 interrupts, at the contacts 610', the connection between the grounded guard conductor |28| of the rst link at the iirst operator position OP--I and 'the' guard conductor |210 of the .first operator 'position OP|, thereby to mark the rst operator position OP-I as idle to the position distributor PD, in the manner previously explained. Also, upon operating, the cut-through relay 680 completes, at the contacts 681, an obvious multiple path for applying ground potentialto the guard conductor |28| of the iirst link at the iirst operator position OP-l; and interrupts, a't the contacts 688, the previously traced holding circuit for energizing the lower winding of the automatic answer relay 605, thereby to cause the latter relay to restore. Upon restoring, the automatic answer relay 605 interrupts, at the contacts 601, the previously traced circuit for intermittently illuminating the link-busy lamp 603; and completes, at the Vcontacts 608, an obvious multiple circuit for steadily illuminating the linkbusy lamp 603, thereby to indicate to 'the operator at the iirst operator position OP-l that the connection has been cut through to the toll first selector TFS-I of the first link thereat.

Incident to operation of the cut-through relay 680, and prior to release of the connect relay 610, a circuit is completed for energizing the upper winding lof the call pilot relay |350, this circuit extending from ground by Way of the W- er winding of the cut-through relay 680, the contacts 685 and |559, the release call conductor |355 in cable #l and the upper windingY Yof the call pilot relay |350 to battery. When thus energized, the call pilot relay |350 operates to interrupt, at the contacts 135|, the previously traced path for applying ground potential to the sequence control conducto-r |384 extending to the sequence control circuit SCC; whereupon the sender link SL-l `and the register sender RS are released. Further, it is noted that when the connect relay '670 restores it interrupts, at the contacts 611, the previously traced holding circuit for energizing the winding o'f the start relay 660, thereby to cause the latter relay to restore; interrupts, at the contacts 616, the previously traced circuit for energizing the Winding of the answer pilot relay |3410, thereby to cause the latter relay to restore; and interrupts, at the contacts 650, the previously traced circuit for energizing the upper winding of the call pilot relay |350, thereby to cause the latter relay to restore. When the talk relay H30, the answer pilot relay |3'l0 and the call pilot relay |350 restore, the signal interrupter relay H60 restores, thereby completely to release the operator position telephone equipment and the operator position relays at the first operator position OP--L At this time, an operative connection is completed. between the calling subscriber substation T-I inthe central oice CO and the operator position 4|0 in the distant exchange DE-Z, whereupon the operator at the operator position 4|0 extends the call, in accordance with conventional practice.

Etenst'on of other calls to and from the switchboard in vthe central oce Vand supervision vIn View of the above description of the mode of operation of the apparatus at the first operator position OP-I at vthe switchboard .in the central cnice CO to extend a call thereto from the Vcalling tri subscriber substation T--I in the central oice CO, it will be readily appreciated that the apparatus at the rst operator position OP-I at the switchboard in the central cnice CO is operative, in a similar manner, to extend other calls thereto. For example, a call may be extended from the operator position 2|0 in the distant exchange DE-l to the first operator position OP-I in the central oiilce CO, by way of the toll line TL| extending between the distant exchange DE-I and the central oince CO, the toll line circuit TCL-I, the trunk line 2|0 and the iinder F-l of the iirst link at the first operator position OP|, the operation of the apparatus at; the rst operator position OP-I at the switchboard in the central office CO, in the present example, being substantially identical to that previously explained.

In view of the above description of the mode of operation of the apparatus at the rst operator `position OP-I at the switchboard in the central oice CO to extend a call therefrom to the operator position 4|0 in the distant exchange DE-Z, it will be readily appreciated that the apparatus at the rst operator position OP| at the switchboard in the central office CO is operative, in a similar manner, to extend other calls therefrom. For example, a call may be extended from the first operator position OP-I at the switchboard in the central ofiice CO to the subscriber substation T-Z in the central oiice CO by way of the toll rst selector TFS-l of the first link at the rst operator position OP-|, the trunk line 403, the local switch train LST-2 and the subscriber line 406, the operation of the apparatus at the rst operator position at the switchboard in the central oice CO, in the present example, being substantially identical to that previously explained.

At this point, it is noted that the operator at the rst operator position OP-I at the switchboard in the central office CO has answer and release 'supervision of the calling line seized by the iinder F-I of the first link thereat by means of an arrangement including the answer lamp 602, the answer and release supervision arrangement being identical to that disclosed in the previously mentioned Crocker patent; also, the operator at the first operator position OP-I at the switchboard in the central oiiice CO has call and release supervision of the called line seized by the toll rst selector TFS-I of the first link thereat by means of an arrangement including the call lamp 60 the call and release supervision arrangement being identical to that disclosed in the previously mentioned Crocker patent.

Further, it is pointed out that the operator at the first operator position OP| at the switchboard in the central cnice CO may release a connection extended to her position instead of extending the connection therefrom, in the manner previously explained. For example, in the event a connection extended to the rst operator position OP-l at the switch board in the central office CO, by way of the rst link thereat, is to be released prior to extension of the call from the iirst operator position OP--|, this may be accomplished by the operator at the first operator position OP-I by operating the release answer key K-B in the operator position key set. More particularly, when the release answer key K-8 is operated there is completed, at the contacts |408 thereof, an obvious path for short-circuiting 1n multiple the winding of the answer pilot relay |340, the upper winding of the change-over relay 630 and the lower winding of the automatic answer relay 605, thereby to cause the relays mentioned to restore. Upon restoring, the changeover relay 630 interrupts, at the contacts 634, the previously traced holding circuit for energizing the intermediate winding of the electropolarized relay 6|0, thereby to cause the latter relay to restore. Upon restoring, the electropolarized relay 6 |0 interrupts, at the contacts 6|8, the previously traced holding circuit for energizing the upper winding of the connect relay 610 in series with the winding of the talk relay H30, thereby to cause the latter relays to restore, Upon restoring, the answer pilot relay |340 interrupts, at the armature |344 and the front contact associated therewith, the previously traced holding circuit for energizing the winding of the start relay 660, thereby to cause the latter relay to restore. Upon restoring, the start relay 660 completes, at the contacts 66 I, an obvious circuit for energizing the release magnet, thereby to cause the wiper carriage of the finder F-l to be released. Upon restoring, the automatic answer relay 605 interrupts, at the contacts 606, a further point in the holding circuit for energizing the lower winding thereof; and interrupts, at the contacts 601, the previously traced circuit for intermittently i1- luminating the link busy lamp 603. At this time, the iinder F-I of the rst link at the first operator position at the switchboard is completely released when the operator thereat returns the release answer key K-8 to its normal position.

In the foregoing explanation of the mode of operation of the finder F--I of the first link at the first operator position OP-l at the switchboard, it was assumed that the operator thereat desired the connection to be switched through automatically from the calling line to the called line, exclusive of the first operator position OP-\-|, incident to the extension of the call from the rst operator position OP-I. However, it may occur that the operator at the first operator position OP--I desires the connection to be switched through automatically from the calling line to the called line, and including the first roperator position OP-|, incident to the extension of the call from the first operator position OP--L In this event, when the operator at the first operator position OP-| answers the call on the first link thereat and determines that she f desires the first operator position OP-I to be included in the completed connection between the calling line and the called line, the operator at the first operator position OP--I first operates the talk key K-l of the finder F-l of the first link prior to operation of the operator digit keys DK. At this time, when the talk key K-I is operated, a further holding circuit is completed at the contacts of the talk key K-l for energizing the upper winding of the connect relay 610 in series with the winding of the talk relay H30, this circuit extending from ground by way of the winding of the talk relay H30, the hold conductor 605 in cable #1, the contacts of the talk key K-l, the contacts 619 and the upper winding of the connect relay 610 to battery. Subsequently, when the cut-through relay 680 operates to interrupt, at the contacts 689, the previously traced alternative holding circuit for energizing the upper winding of the connect relay 610 in series with the winding of the talk relay |30, the talk relay I |30 and the connect relay 610 remain in their operated positions due to the completed further holding circuit, including the contacts of the talk key K|, for energizing the upper wind- 'ing of the connect. relay 610 in series With the winding ofthe talk relay |30; ,Hence at this time, the cut-through relay 680 completes, at the contacts 68| and 682, the previously traced connectionl between the toll first selector TFS-I of lthe first link and the trunk circuit at the first operator position OP|, the finder F--I of the first link being connected to the trunk circuit at'the first operator position OP-|, due to the operated connect relay 610 at this time. Accordingly, at this time, both the calling line and the called line are interconnected at the trunk circuit at the first operator position OP-|; and the operator thereat may communicate in either direction selectively or simultaneously over either the calling line or the called line. After the operator at the firstoperator position OP-I satisfies herself concerning the routing of the connection, she may complete the previously traced direct connection between the finder F--I and the toll first selector TFS-I of the rst link independently of the first operator position OP-I, and consequently the direct connection between the calling line and the called line, by restoring the talk key K-I of the finder F-|, in the manner previously explained.

It is contemplated that the operator at the first operator position OP-I will permit automatic switch-through of the links thereat, exclusive of the first operator position OP-I, primarily in connection with inward and through toll connections; and that, in conjunction with other connections, particularly C. L. R. connections, the

operator at the first operator position OP-I will cause automatic switch-through of the links thereat, including the first operator position OP-'|, whereby the setting up of the connections is supervised.

Inthis connection, it is noted that the operator at the first operator position OP-l at the switch- `previously mentioned Crocker patent.

Further, it is pointed out that the release of the rst link atthe first operator position OP-I `at the switchboard is under the control of the operator thereat and that either the finder F-l or the toll first selector TFS-l may be selectively 'released In order to effect the release of the first link at the rst operator position OP-I at the switchboard, the operator thereat first operates the talk key K--l of the finder F--I of the first link, thereby 'to complete an operative connectionr between the first link and the operator position key set, the circuits completed being fully described in the previously mentioned Crocker patent, At this time, the operator may release the finder F-I and, consequently, the answer end of the first link by momentarily operating the release answer key K-S; or the operator may releasethe toll first selector TFS-I and, consequently, the call end of the rst link by momentarily operating the release call key K|2. Further, the operator may release substantially simultaneously both the finder F-I and the toll first selector TFS-I of the first link by momentarily operating the release answer and callr key K'-|,|. j Y

' "Further, it'is noted that, while the talk key K--I of the finder F-I of the first link at the

Images