Патент USA US2405194код для вставки
Aug., 6„ E 4° J. w. DEHN ETAL. TELEPHONE , SYSTEM Filed _July 2o, 1945 @Q TIL>U| ymì ¿sheets-sheet ¿405,1 1 NWS T. .mi @Nkm. /fv VEA/Tops“v4.w» M Aug» 6, 1946« ...L> w. DEHN ETAL." TELEPHQNE SYSTEM1 Filed July ép, 194sv BN ,www 4 sheets-sheet 2 u. AT'ToR/vy Aug. 6, 1946. J. W. DEHN EVAL ¿40,194 TELEPHONE SYSTEM Filed July 20, 1945 4 Sheets-Sheet -1'?, KR.” @mew w /A/VE/VTORS BV ATTORALSV 2,405.19 Patented Aug. 6, 1946 UNITED ¿STATES PATENT ori-‘ICE TELEPHONE SYSTEM Joseph W. Dehn, Great Neck, and Myron C; Goddard, Garden City, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation'of New York Application July 2o, 1943, s_e?iai No. 495,489 (Ci. 179-18) 7 Claims. l This invention relates to telephone systems and particularly to those in which connections are established by automatic switches. In automatic switching systems using line find ers or trunk finders it is usual to have a plurality of such :ñnders in groups serving groups of lines or trunks. Associated with. each finder group is - a start circuit actuated by a line or trunk over ‘ improve the flexibility of group allotting arrange ments in automatic switching; systems in which there is a tendency to limit the operation of mechanism to a single channel during light load periods. A feature of the present invention consists in automatically operable preference control mech anisms for shifting the Vpreference for selecting which a call has been initiated and this start finders arbitrarily during light load calling peri circuit energizes a particular iinder except when 10 ods and in a sequential order during busy load this finder is in use. When the ñrst finder is in Y calling periods. use it transfers the start lead to the nextfinder Another and related feature of the invention of the group. The start lead is thus transferred consists in means associated with the preference to the next in order finder in a group or sub control mechanism automatically operated by group in a sequential manner by the preceding periodic switching operations >in the office for finder as the finders are taken for use. » ¿_ determining kwhen the order of preference for In the system disclosed herein both line finders trunk finders and senders shall be normally ad and trunk finders are used, each having other vanced and when it shall be arbitrarily advanced. mechanisms permanently connected thereto, the These and other features will be discussed more line finder having a trunk’and a dual selector 20 fully in the following description as illustrated in connected thereto and the trunk finder having a the accompanying drawings in which: sender connected thereto. This arrangement is Fig. 1 .illustrates a line finder, a line-finder selector trunk, a Vdual selector, and associated selectors and villustrates in detail the mechanism used as a matter of economy to obviate the use of links or connectors between the finders and the senders and for the sake of speed in operat 25 of'a-trunk-finder circuit; Y Y ing these mechanisms.. Both a line finder and . Fig. -2 illustrates the mechanism associated with a trunk ñnder are automatically energized by an a number o_fsubgroups of trunks Aand trunk-finder incoming call, the line finder hunting for the circuits for _shifting the preference of trunk-` calling line and the trunk finder hunting for the findercircuits in a sequential order as the finders trunk permanently connected to the hunting line 30 are taken for use; _ _ _ finder. Thus a sender is automatically connected .'Fig. 3 illustrates anY automatically operable ar with the calling line in a short space of time by rangement for arbitrar-ily shifting the preference the action of the line and trunk finders. The of trunk iinders during -light _load calling periods circuits from the sender dial tone mechanism and for placing the :ñnder preference mechanism and dial pulse responsive mechanism extend 35 in the normal sequential order during busy load through the trunk finder, the trunk circuit, the calling periods; and line under and over the line to the station mech _- » v Y ` Fig,` 4 illustrates the grouping arrangement of line finders, trunks, selectors and the trunk find anism of the calling subscriber. One group of lines is served by a particular group of line finders and a plurality of groups 40 of trunks connected to these line finders is served ers and the senders. _ _» _ General description by'a particular group of trunk finders. A start circuit for energizing the trunk ñnders is com of an automatic switching system in a small tele-A mon to the trunks of a group and also common phone vareafo'r which this invention is used is The grouping arrangement of the mechanism to the finders of this group which serve these 45 shown in Fig. 4. trunks. The finders are operated in a set se Reference may be had to my copending application, Serial No. 495,487, filed July 20, 1943, for a complete descriptionof differ quence during busy periods as the finders are taken for use. However, during non-busy periods ent units of mechanism shown herein in dia if calls come into the ofñce from a given group grammatic form and also for a completedescrip of lines over spaced periods and each call is dis 50 tion of the organization and operation of these connected before another call comes into the office units of mechanism.v Two groups of lines 400 the same finder would be used for all of these and 4H are shown served by two subgroups of successive calls. In the case of the trunk finders line finders each of which may comprise ten line which each have a sender permanently connected finders. The ten line finders dill-402 have ten thereto this would mean that the same sender 55 trunks M13-404 and Aten dual selectors 405-406 would be'repeatedly connected to the calling lines permanently connected thereto’. of a group if the calls in the group were spaced apart so that each switching connection is com pleted and disconnected before another call from this group of lines enters »the oiiice. The same ar rangement is used for each subgroup'as shown for' the :ten line finders 4i8-4I9 which served the group of lines 4H and -have- ten trunks 420 60 nl.The object -of thisrinvention is, therefore to _ 42| and ten .dual selectors 422-423permanently connected thereto.Y »The sequence of operation of e a line finders in a subgroup of li-ne'iinders is well known inthe art and therefore only 'a general description of this operation need be given. The energization of line equipment responsive to an incoming call actuates what is known as a group \ start relay which energizes a line iinder and marks a segment on the line-finder commutator to guide the line finder to a particular level >of* switch tter 4 permanently connected thereto. -.As an example, let it be assumed that during a light load period the first trunk ñnder 4I2 of a subgroup is ener -. gized repeatedly by successive calls because these calls .are spaced so that there is only one call ` in the subgroup alt any one time. Since a sender 426 is permanently connected to this trunk ñnder ' this sendervwill be continuously used to the ex clusion of the other senders and if this sender minals where the calling line may be found. '- The becomes faulty in its operation it may prevent line iinders are allotted for use in -`a 4sequential 10 completing a number of telephone connections. order depending upon the busy `condition of the An auxiliary preference shifting mechanism is line iinders in the subgroup. This allotting is shown in- Fig. 3 which is automatically respon controlled by the transfer of the line-finder start sive to light and heavy load conditions. During circuit sequentially as the finders become busy normal heavy load conditions this mechanism 15 which circuit` is carried through contacts of a causes the regular sequence starting mechanism relay in each line iinder. to function as described above but during light In the presentlsyste'm the operation of a line load periods when calls are' spaced apart it alters finder such -as 40| .fromy its start circuit auto fthe. preference for thev trunk finders after each matically energizes mechanism in its associated call and thus alters the preference for senders trunk 403 which establishes a start circuit for a 20 connected to these trunk finders. This not only trunk -iinder so that both the-line finder and the has the advantage of using different sender mech trunk Afinder are hunting simultaneously. The anism for successive calls but has the advantage line iinder 60| hunting for the calling line and the trunk finder, Figs. 1 and 2,-hunt for the trunk . of providing telephone service at all times even 403 connected to the hunting line îñnder 40|. 25 though a sender mechanism _is faulty in an un attended oiiice. The trunk-iinder start circuitis common to the line ñnders and associate-d 'trunks of the line iind Detailedv description er subgroup as shown‘and thereforefany trunks One of a group of lines is shown in Fig, 1 con in this-subgroup will `establish a start circuit for to a subscriber’s station‘A which causes subgrouprstart relay` 4|4. Likewise any trunk in 30 nected the energization of a line ñnder and line iinder a second group 420-42Iwi1l establish» a circuit selector trunk circuit such as |00 and IílI respec for group» start relay’ 4I3. Each start relay con tively when the subscriber A removes the receiver trols a subgroup of trunk finders. from the switchhook. The line ñnder and line Trunk iinders 4I I-4I2 are diagrammatically selector trunk circuit operate in a manner shown for serving theiirst subgroup of trunks 35 ñnder fully .described in copending application Serial and trunk iinders- 4 I 5 and-4 I 6 for serving the sec No. 495,487, filed July 20, 1943, and therefore need ond subgroup of trunks, each of these trunk lind not be described herein. VThe energization of the ers being the same as shown in'Fig. l of the draw line finder |00 by a subgroup start relay also ings associated With the sequence circuit and sub group start circuits of Fig. 2. A 'shown diagram 40 causes the energization of the line finder selector trunk IUI which connects ground to the start lead matically in Fig. ‘4, -thel’operation `of `'subgroup |45 for energizing trunk ñnder subgroup start start relay 4I4w-i11 actuate trunk finder 4|2 if relay 203. Four such relays are shown 200, 20|, it is idle and if Ait is busy will actuate trunk ñnder 202 and 203 for four subgroups of trunks and 4I I or another trunk finder in the subgroup and therefore for four subgroups of trunk iinders. 45 at the same time will mark a commutator seg As shown in Fig. 4 the start lead |45 and there ment for guiding the trunk ñnder. As previously fore the start ground relay 203 are common to all stated each‘trunk -ñnder `has a sender perma trunks in a subgroup. The operation of relay 203 nently connected thereto and therefore the send is shown for connecting íground to segment I of er 426 is connected through the trunk to the call ing line when the trunk finder-412 is actuated. 50 commutator |22 and for energizing relay I32 of the trunk ñnder which latter circuit may be Sender 421 may be connected through the trunk traced from ground on'contact I of the start to the same calling lline when trunk ñnder 4II ground relay 203, contactl of relay 205, contact is actuated because trunk cfin1deri4l2 is in use. 2 of jack 233, lead 25|, contact 3 of relay |35 This may be any trunk of the group which actu winding of relay I32 to battery. If this trunk ates the trunk finder for associating a sender iinder is busy and relay |35 of this trunk ñnder throughÍ the trunk to the line. The second and is operated the ground from contact I of start other groups of line ñnders, trunks, trunk finders relay 203 extends to the ’next sequential trunk and senders are Aoperated and associated together finder 245 for operating a relay the same as relay as outlined for the ñrst group. From the foregoing it may be seen-that the 60 I32 in the latter trunk ñnder. This circuit would extend from contact I of relay 203, Contact I of normal sequence of operating finders is econom relay 205, contact 2 of jack 233, contact 3 of relay ical 'for'all automatic switching oiiîces and' would |35 operated, contact 2 of relay |26 thence over not> require any auxiliary transfer devices in a large o?ce in which more than one ñnder is nor lead 253, contact 3 of jack 233, contact 2 of jack mally in use. However, in smaller telephone areas there are periods when incoming calls over lines- in a group are spaced apart and the ñrst trunk finder is the same as relay |35 in the first ñnder in a subgroup is taken for use on each incoming call over this period of light load. In the case of the present automatic switching sys tem such as is fully described in copending patent application," Serial No. 495,487, íiled July 20, 1943, 234, contact of relay 26, to a relay such as relay |32 in trunk finder 245. Relay 206 in this second ì trunk finder of the subgroup. 'The‘sequence circuit or preference circuit for otherv trunk ñnder subgroups is shown in Fig. 2. Relays 201 and 208 are in an intermediate sub group of trunk finders and are the same as relay |35 shown in Fig. 1. lRelays 209 and 2|!)A are in another intermediate'subgroup and relays 2| I and overwerk particular trunk‘ñnders 'and senders 75 2 I2 lare in the end subgroup. VStart ground relay and particularly to this system when used as an unattended «oñice this normal procedure would 5 2,405,194 ' 6 200 operates from a start circuit common to one subgroup of trunks and extends this start ground through the mechanism of the subgroups of trunk finders represented by relays 2|| and 2|2. Relay 20| energized by the start circuit of another sub group of trunks extends its start circuit through the group of trunk finders represented by relays 209 and 2|0. Relay 202 extends its start circuit upper winding of relay ’|36V to batteryv on contact 5 of relay |35. This holds relay ‘|36 in an oper ated position to prevent further- stepping. Relay> |26 is made slow in operating to give a short time interval between the last ,vertical step and the first rotary step which is brought about by the operation of relay |26. Relay |26 locks through its lower winding in series with the vertical mag to the subgroup of trunk ñnders represented by relays 267 and 208 as shown. Relay 203 extends 10 net to battery on contact 5 of relay | 35. This places relay |26 under the control of relay |35 its start circuit to the subgroup represented by and causes its release when relay |35 operates. the trunk ñnder in Fig. 1 and the trunk finder The operation of relay |26 transfers the stepping represented by relay 206. These relays 200 to 203 circuit from the vertical to the rotary magnet. also connect ground to segments of commutators in the respective trunk ñnders depending upon 15 'I'his circuit may be traced from battery through rotary magnet |30, contact 4 of relay |26, con which trunk ñnder is energized, By reference to tact of relay |36 to ground on contact 2 of relay diagrammatically grouped units shown in Fig. 4 it | 32. The rotary magnet thus lsteps the shaft may be seen that the operation of start ground around until the sleeve wiper |51 reaches a ter relay 4|4 representing a relay such» as 203 mayr associate ground from its contact I with any corn 20 minal whichis connected to battery through-the winding of a cut-off relay in the trunk circuit mutator segment of the trunk ñnders in the group. When trunk finder 4| 2 is energized by relay 4|4, the trunk ñnder is arrested in its mo tion when it reaches the ñrst level of terminals. These terminals _are indicated as terminals 409. 25 When trunk iinder 4| I is energized by relay 4|4, it is arrested on the second row of terminals indi cated at 4|0 since the ground from contact I of connected» to sleeve lead |50. This circuit extends from ground on contact 3 of relay |32, lower winding of‘relay |36, contact 2 of relay |35, re sistance |2|, upper winding of relay |20, sleeve brush |51 to battery through the cut-01T relay winding in the trunk circuit. The trunk circuit cut-01T relay operates in this circuit and in so doing connects ground with the sleeve lead |50 start relay 4 I 4 is connected to the second segment in place of battery. Relay |36 is thus held op of the commutator of trunk finder 4| I. . The trunk ñnder shown in Fig. 1 operates in 30 erated to prevent further stepping of the brushes in a rotary movement. Relay |20 is also suffi the following manner for connecting a sender to ciently operated to close its contact 9. 'I'his ener the calling line. For this connection it may be gizes the lower winding of relay |20 over a circuit assumed that the trunk ilnder shown Ain Fig. >1extending from battery through this winding and is used and that therefore the start circuit is contact 9, contact | of the rotary magnet, con~ extended by relay 203 through contact 3 of relay tact of relay |36 to ground'on Contact 2 of relay |35 and the winding of relay |32 operating the |32. The operation of relay |20 connects leads latter relay, and that segment I of the commuta |46 to |49 and |5| to |53 directly to the mecha tor |32 is connected with ground by the operation of relay 203. Relay |32 associates ground with 40 nism of sender 320 and establishes an operating circuit for relay |35. This operating circuit may the sleeve lead ||| extending to the sender and be traced from battery through the upper winding operates the stepping relay |36. The circuit for of relay |35, contact I0 of relay |20 to ground on operating relay |36 may be traced from ground contact 2 of the olf-normal contacts |25. The through contact 2 of relay |32, contact of Vertical magnet |3|, Contact 2 of rotary magnet |30, up 45 operation of relay |35 closes _the sleeve lead ground from the trunk to the sender which may ped winding of relay |36 to battery connected to be traced from ground on sleeve lead |50, brush contact 5 of relay |35. The stepping relay |36 |51., contact 4 of relay I 20, contact 2 of relay |35 establishes a circuit for the vertical magnet which to sleeve lead ||| extending through the sender. steps the shaft up one step placing the 'commuta tor brush |23 on the first segment. l'I'hecircuit 50 Relay |35 also closes a locking circuit for relay |20 traced from battery through its lower wind for the vertical magnet may be traced from bat ing and contact 9 of relay |20, contact 4 of relay tery through contact 5 of relay |35, vertical mag |35 to sleeve lead |||. Relay |35, as has been net |3I, contact 4 of relay |26, contact of relay previously described, transfers the start lead 25| |36 to ground on contact 2 of relay |32. The vertical off-normal springs |25 are closed and the 55 to the next in order trunk ñnder. The start lead extends from lead 25| through the associated circuit for relay |36 is opened by the contact armature, contact 2 of relay |26, lead 253, contact of the vertical magnet |3I. Relay |36 releases 3 of jack 233, contact 2 of jack 234, through the which causes the release of the vertical magnet contact of relay 206 to a relay the same as relay which now recloses the circuit to relay | 36. If brush |23 is not associated with-ground on the 60 |32 of the preceding trunk ñnder. 'I'he opera tion of relay | 35 removes battery through its ñrst terminal, relay C and the vertical magnet contact 5 from the upper winding of relay |36 continue to step the brushes ofthe trunk ñnder and from the vertical magnet circuit and relay in 4an upward movement until the commutator |26 and also releases relay |36 by short-circuit brush reaches the segment which is grounded by the operation of the group start relay which 65 ing its lower winding through its contact 2. This releases relay |26 so that the start circuit may in this case is relay 203. Since, for this exam extend through its contact 2. The circuit for ple, segment | of commutator |22 is connectedrelay |32 is opened through the continuity con with ground, the brushes |54 to |6| of the trunk tact 3 of relay |35 and relay |32 is made slow finder are arrested on the first level of terminals. to release so that ground is'held on the sleeve A circuit fory relay |26 is established through its 70 lead extending to the dual selector and the sender upper winding in series with the upper winding until a short period of time has elapsed so that of relay |36. This circuit may be traced from the mechanism of the associated circuits has had ground on contact 2 of relay 203, segmentl >of commutator |22, brush |23, upper windingof relay | 26, contact 2 of the rotarymagnet-|36.;- time to function. l _ The sleeve circuit in the trunk |0| has ground extended thereto, ñrst, by the line länder,B_.ndsec-y 2,405,194. 7 ous' senders maintains -relay 30|‘constantly oper ated` and .the normal preference circuit shown in 0nd,.' by aïrelay in they dual. selec-.tor~ |02. `When this 'ground is initially- connected iîrorrr'the- line li‘igfZ1 for the trunk‘ñnders is in use so that when one îiinder is busy the next in order finder in the sequence is energized in the Vmanner previously C71 the trunk liinder’ andïat the same time‘connects explained. ' finder to the trunk" circ >'t, a' 'trunk start relay-is operated which establishes -the’start circuit? for battery through the> winding of the trunkY cut off Vrelay Wi'thïthe sleeve lead |50 extending to the sleeve terminal of the Vtrunk` finder terminal-bank. As previously described fwhen "theV 'trunk finder ñndsthis terminal, relay '|20 »is operated'suñl ciently »to close 'its contact 9. 'This operation takes pla‘ce‘through the 'upper winding of relay |20, During light load periods when the incoming calls are spaced apart and only one sender is ener gized at' Va time Y'the following procedure takes 10 place .in the `ñnder preference control circuit as follows. During vthis period the ñrst sender ener gized operates its relay 32| which connects ground through the winding of relay 30| which operates. Relay 322 is operated to release the sender. The latter relay holds'ground through lower winding of `relay |36 to' ground on contact 3 of relay |32 and when this circuit is established the cut-off >relay in the trunk is operated in such a manner as to connect -ground instead of-battery with ïthe sleeve -lead |50 and relay |20 -is «locked through its lower winding as described. The ground extends over lead |50 through contact 4 of relay >|20 and contact 2 of relay |35 after the 'i latter relay is operated, thence over -sleeve llead ||| tothe sender for holding the off-normal ground sender relay 32| 'and' as noted on the drawings the operationl of relay 32| operates relay 324. The energization of -relay |32 in the trunk the winding of relay 30| until the sender has re leased- which releases both relays 32| and 324. Relay 322 is slow to release after the other mech anism of the sender has been released and there fore .the release of -relay 324 causes a circuit to be established from’ground through contact 2 of re lay 322, contact of relay 324, contact of relay 323, contact 2’of relay 30 I, rotary :magnet 304 to bat tery energizing the rotary> magnet 304.l The sender having released causes the release of relay 322 thus removing ground from rotary magnet 304; removing ground from the winding of relay 30| and contact 3 of relay 302. When ground is removed from the rotary magnet'304 the brush finder causes the operation of off-normalrelays 32| and 324 so that the sender is prepared to func tion 'as soon as it is connected Vto the trunk cir 308 steps from its normal position to terminal |. The removal of ground from the winding of relay cuit and line‘finder. This automatically ‘estab lishes the dial tone >circuit and Vcauses dial tone to be connected with conductors extendingrto "the 33|and from'armature 3 of relay 302 causes a cir cuit to be established for‘ relay 302 from battery subscriber’s line and thereafter establishes a con through resistance 3| I; winding of relay 302, con nection between vthe calling subscriber’s line and tact V3 of relay 30| to ground on contact 2 of relay pulse responsive equipment in the 'sender for set ting the ’sender according to dial pulses trans 35 309. Thus, both relays 30| and 302 are operated. mitted by the calling subscriber. l Y Y The ñnder preference control circuit j 300 is shown connected to one sender rcircuit 320 and it is also -'shown that this control circuit is corn mon to all senders of the telephone office. Since each trunk ñnder has lasender permanently con nected. thereto the device 300 is a sender prefer 40 ence‘control circuit as well as a trunk-finder con trol circuit but'will be known hereinafter as the The operation of relay 302 establishes a circuit to arbitrarily change the preference lof all trunk ñnder circuits by operating relays 204 and 205. It will now be apparent that if start ground re lay 203 'is'energized the start circuit extends 'from ground on contact I of relay 203 through the in ner contact | of relay 205, contact 2 of jack -234 to trunk iinder Y245 which -is the second trunk finder in the sequence of the start circuit. Like Wise ifany of >relays 200, 20| -or 202 are energized the start circuit extends to the second trunk the copending application, Serial No. 495,487, ñled'July 20, 1943,'may be had for the detail oper finder of the subgroup instead of the first trunk finder. `By vreference to Fig. 4 it will be seen that ation of the senders shown diagrammatically in Figs. 3 and 4. For convenience in referring to 50 the second :trunk iinder 4| l `has sender 421 per the larger disclosure, relay numbers-'are shown manently connected thereto whereas the ‘ñrst in the sender 320 in brackets which are the 'same trunk finder 4|2 has sender 426 permanently con as the numbers given to these relays in the afore nected thereto. Therefore, in shifting the prefer mentioned copending patent application, the ence of the trunk finder arbitrarily as above-out numbers which are not »in brackets will be used 55 lined the preference is shifted Vto a different in this description. The control features ofV the sender than would be used if this preference had finder preference control circuit. Reference to mechanism of the ñnder preference control' cir cuit 300 depend upon the frequency with which senders of the oilice are taken `for use by incom ing calling-lines. The‘energiaaticn of relay 32| not been altered. The rotary oft-normal contact 336 is closed when brush308 steps to the iirst terminal and with both relays 30| and 302 oper ated a circuit is established for release magnet when thev sender is taken for use, establishes .a 60 335 :from ground on contact | of relay 30|; This circuit >for relay 30| from ground on `the contact causes the brush 308 to restore to its normal posi of relay 32|, contact | of relay 303, contact 3 and tion but ydoes not cause the release of either 're winding of relay 30|, resistance 3|0 to battery. lays 30| or 302. This ground places a shunt on relay 302 through When the next trunk finder and sender are its contact 3 so that relay 302 does not operate 65 taken for use relay 132| of this sender is oper atthis'time. The operation `of relay 324 opens ated which again connects ground to lead 330 which in vthis case short-circuits the winding of relay 30| causing its release. Relay 302 is, how ever, held operated from ground over lead 330, 70 the rotary magnet 304 is energized `and deener continuity contact 3 of relay 33| released, wind gized and requires. the lenergization. of release ing of Arelay-332, resistance 3|I to battery. This magnet 305 >to return it to its normal position. trunk liinder and sender are the second preference During normal busy load periods more than-one finder and sender since relays 204 and.205.;are sender is in constant useY and -?thereîorej-the 75 operated. «Uponlthe-operation of? relay322 for a circuit at one point which is later established for the rotary magnet 304 of switch 301. Switch 301 is of the type which is moved `one step when `the release of this sender and the release of relays 32| and 324 a circuit is again established ’over lead 33| for the rotary magnet 304. In this case the circuit extends through contact 3 of relay 302, rotary magnet '304 to battery. When relay 322 releases, the brush 308 again steps from its normal position to terminal | and, since the . f l0 cessive sender operated vand released-on overlap ping calls associates `ground with the stepping circuit for energizing rotary magnet 304 and the switch is advanced as each sender is released. The circuit for energizing the rotary magnet 304 is over conductor- 33|. Assuming that relay 30| is operated this circuit extends from contact 2 ground is removed from lead 330, the circuit for of relay 32-2, contacts of relays 324 and 323, lead relay 302 is opened and the latter relay releases. This constitutes the ñrst cycle of preference 10 .33| to Contact 2 of relay 30|, rotary magnet 304 to battery. Upon the release of each sender shifting by relays 30| and 302. The release of this circuit is closed and opened causing the relay 302 returns the sequence circuit shown in switch to advance one terminal. Under this con -Fig. 2 to normal by releasing relays 204 and 205 dition if the switch advances to terminal 6 re and thus the first trunk finder is the preferred finder for the next successive call.v The third 15 sponsive to the operation and release of six consecutive senders without any spaced periods spaced call which is the next successive call in the operation of 4these senders, relay 309 is again operates a sender relay 32| causing- the operated from ground connected to brush 30S. operation of relay 30| and the release of this Relay 309 in operating establishes a locking cir sender brings about the operation of relay 302 and the operation of the rotary magnet 304 20 cuit to ground on contact | of relay 32| _of the energized sendersl so that the continuous over causing the brush 308 to step forward. The lap operation of 'senders maintains relay 309 operation of relay 302 _again shifts the sequence locked in an operated position. Relay 309 in circuit by the operation of relays 304 and 305 operating opens the circuit extending over lead and the release of relays 30| and 302 by the sub sequent operation and release of a sender again 25 330 to relays 30| and 302 and opens the ground circuit from its contact 2 which is used to oper shifts sequence circuit of the trunk finders as ate relay` 302 as previously described. This explained. When the switch 301 moves away causes the release of relay 30| establishing a from its normal position, the rotary oñ-normal circuit for restoring switch 301 to normal by contact 306 is closed and therefore, at any time that relays 30| and 302 are both operated or 30 energizing the release magnet 305 'and prevents any further arbitrary shifting as long as there are both released, the release magnet 305 is energized overlap operations of the senders. If relays 204 through contacts 2 of relays 302 to ground on and 205 were operated they are now released and contact | of relay 30| and therefore this switch the normal 'sequence operation as shown in Fig. is released very often during calls which'are spaced apart. In fact, this release occurs after 35 2 remains in use as long as this busy condition ensues. The next light load period when thelast each cycle of operation when relays 30| and 302 sender in use has released and no other sender are both operated or both released for shifting of the office is in use for a switching connection the preference circuit of Fig. 2. However, when removes ground from lead 330 and the locking a busier period occurs the switch may advance a number of steps without having the trunk 40 circuit for relay 309 is thus open and this relay now releases. The next sender operated will finder preference shifted. " thus operate relay 30| >and if a spaced light load Let it be assumed now that after a number period 'follows the busy period, the arbitrary of spaced operations of the switching equipment shifting of ‘the preference again takes> place of the oñice including senders, when only one switching equipment is operating at one time, 45 under the control of relays 30| and 302 as oper ated. by the spaced operation of the senders.v a busy period occurs and that there are a num Frequently, during light load periods three .or ber of over-lapping calls and therefore that more than one sender is in operation at one time for four calls may enter the office in an overlapping order and thereafter the calls> may be again completing switching connections. These over lapping operations hold ground continuously on 50 spaced apart. During this period when more than one sender is in operation at the same time, lead 330 since a relay the same as relay 32| is relay 30| or relay 302 would .remain .operated operated in more than one sender and the oper and the other relay of this pair would remain ation of relay 32| in one sender overlaps the normal. Each of the four senders during.. this operation of relay 32| in another sender. If relays 30| and ‘302 are normal, the ñrst sender 55 overlapping period would, upon releasing, ad vance switch 301 one step so that at the time the operated during this busy period will operate fourth sender released'brush 308 would'have relay 30| and place the shunt ground on contact reached the fourth terminal. Assuming that re~ 3 of relay 302 to prevent the operation of relay lay 30| had been operated during this' overlapping 302. If relays 30| and 302 are operated, the first sender operated during the busy period will 60 period, relay 302 is operated at 'the time of re leasing the fourth- sender by removal of ground release relay 30| by placing a ground shunt from lead 330 which removes the shunt from re through contact 3 of relay 302. This will con lay 302. This voperates relays 204 >and 205130 tinue until such time as all of the senders in arbitrarily shift the preference of the trunk operation at any one time have released and the finders and Vassociated senders. On the other preference for the trunk finders and senders will 65 hand if relay 302 was operated during kthe over be according to the position of the relays in the lapping period ‘and relay 30| was released, then finder preference control circuit 300, that is, with the release of the fourth sender would cause the relays 204 and 205 operated, the second finder release of relay 302. In either case both of relays and associated sender are preferred and with relays 204 and 205 released the first trunk finder 70 30| and 302 wouldv either be operated or released and consequently a circuit is established for the and associated sender are preferred. This, of release magnet 305 to cause Athe switch 301g`to course, depends upon whether relay 30| is held restore to normal. Therefore at this> time the operated at the time or whether relay 302 is normal shifting arrangement of preference shown held operated. During this temporary busy4 period each suc 75 in Fig. 2 is >not used sincev the light load’period , of 'incoming calls continues even'though’iîor'a- 2,495,194 short period a small number of calls enter the ofiice in overlapping order. y - r12 ating a finder, the lines of. each group preferring said finders in a particular order, mechanism for normally advancing the order of preference se quentially as said finders and senders are taken `From thel foregoing it is vaplîlarent that’ the auxiliary device 30D is common to and under con trol of thev senders in the. oflice for arbitrarily Ul for use during busy load calling periods, an aux iliary device common to and under thel control of switching the order of preference of trunk iinders the senders in said ofñce for arbitrarily switching and senders during light -load calling periods on said order of preference during'light load calling each occasion after the release of the sender when no sender in the oñice is in use for a switching connection so that the senders serving each group of lines are used in successive order during light load periods but automatically control the re version to the normal preference shifting con trol shown in Fig. 2 during heavy load calling periods on each occasion after the release of a Isender when no other sender of the oliice is in use ‘for a switching connection so that the send ers serving each group of lines are used in a suc cessive order during light load periods and a con~ trol mechanism automatically operated by' peri odic sender operations in said office for deter periods. What is claimed is: l. In an automatic switching telephone oflice, , mining when the order of preference for finders and senders shall be normally advanced and when switches, groups of lines, a plurality of senders, a it shall be arbitrarily advanced. plurality of iinders in groups each having one of said senders permanently _connected thereto op flce, groups of lines. a group of line iinders serv erable for connecting said senders to said lines, means responsive to a call overa line for operat ing a finder, the lines of each group preferring 5. In an automatic switching telephone oi ing each group of lines. each line ñnder having a trunk permanently connected thereto, senders. a group of trunk iinders common to each group of line finders and trunks, each- trunk iinder hav saidiinders in a particular order, mechanism for normally advancingr the order of preference, se. 25 ing one of said senders permanently connected thereto, means responsive to a call over a line quentially as` said finders and sender-sare taken for operating aline finder and a trunk finder for for use during busy load- calling periods and an connecting a sender to thev calling line, said trunk auxiliary device for arbitrarily advancing said finders and senders being operated in a preferred order of preference during light load- calling 30 order, mechanism for normally advancing the order ot> preference sequentially as ysaid trunk 2. In an. automatic switching telephone, office. iinders and senders are taken for use-during busy switches, groups of lines, a plurality of'Y senders, load calling. periods, an auxiliary device for ar afplurality of finders in groups each having one bitrarily advancing said order of preference dur of said senders permanently connectedthereto operable for connecting said senders to said lines, 35 ing light load calling periods on each occasion after lswitching connection is completed and' no means responsive. to acall over a linev foroperat other switching connection is in progress of com ing a finder, the lines of each group preferring pletion and a control mechanism automatically said iinders in a particular order, mechanismrfor operated by switching operations in said oiilce normally advancing the order of preference se for. determining when the order of preference for quentially as said iinders and senders are taken trunk iinders and senders shall be normally ad for use during busy load calling periods, an auxil vanced and when it shall be arbitrarily advanced. iary device for arbitrarily advancing saidorder 6. In an automatic switching telephone oflice,A of preference during light load calling periodsand groups of lines, a plurality of finders inV groups, a control mechanism automatically operatedu by periodic switching operations in said cnice for 45 means responsive to a call over-a line for operat ing a iinder, the lines of each ñnder group pre determining when the order „of preference for ferring said ñnders in a particular order, mech ñnders and senders shall be normally advanced anism for. normally advancing the order of pref and when it shallbe arbitrarily advanced. ` erence sequentially as the findersl are taken for 3. In an automatic switching telephonek office, use during busy lead. calling. periods andan auX switches, groups of lines, a plurality of senders, iliary mechanism for arbitrarily advancing said a plurality of iinders in groups each having one order. of preference after each call when. one of said senders-permanently connected thereto finder. completes a telephone connection and is operable for connecting said senders tosaid lines, periods. - , Y ' f , released before another call requires the use of 55 a finder. erating a finder, the lines of each group preferring means responsive to a call over a line for4 op 7.. In an automaticswitching telephone office, groups of lines, a plurality of iindersin groups, said finders in a. particular order, mechanism for normally4 advancing the order of preference se quentially as said finders and senders are taken for use during busy load calling periods, an auxil means responsive to a call over a line for operat ing a finder, the lines of each finder group pre iary device for arbitrarily advancing said order 60 ferring said finders» in a particular orden. mecha nism for normally advancing the order of prefer of preference during light load calling periods on ence sequentially as the iinders are taken for use each occasion after a switching connection is during busy load calling periods, an auxiliary completed and no other switching connection is in mechanism for arbitrarily advancing` said order progress of completion and a control mechanism automatically operated by periodic switching op 65 of preference after each call when one finder completes a telephone connection and is- released erations in said oiiice for determining when the order ofI preference for finders and senders shall before another call requires the use of a finder, and a control mechanism automatically operat be normally advanced and when it shall abitrarily ed by periodic switching operations responsive to be advanced. each call for determining when the order of pref 4'. In an automatic switching telephone office, 70 erence for ñnders »shall be normally advanced switches, groups of lines, a plurality of senders, and when it shall be arbitrarily advanced. a plurality of finders in groups each having one 0f said senders permanently connected thereto operable for connecting said senders to said lines, means responsive to a call over a line for oper 75 JOSEPH W. DEHN'.y MYRON C. GODDARD.