US1701635A - Telephone system - Google Patents

Description

Feb. l2, 1929.

A. J. RAY ET AL 'TELEPHONE-SYSTEM original Filed 4Feb. l22, 1925 @55 sa qwuvw 7% A m Nl \do W mlm@ Q Mv mi, wv v MWIIIIIII FQQQ* Mw uw b NN o E nU-En Drs J. Fag,

Hhur

Patented Fels. l2, 19239.

narran rieur oFFIcE.

ARTHUR J. RAY, OF CUBA, AND RUDOLPH F. TEHLIK, 0F CHGAGO, LLINOIS, AS-

SIGNORS, BY MESNE ASSIGNMELVTS, TO AUTOMTICELECTRIC INC., OF CHICAGO, ILLENOIS, A CORPORATION OF DELAVARE, Y

rnnnrnonn SYSTEM.

Application filed February 2, 1925, Serial No. 6,181. Renewed July 5, 1928.

The present invention relates in genera to telephone systems, hut is concerned more particularly with telephone systems in which ar-- rangements are provided for absorbing' one or more digits in certain of the telephone numbers, and is concerned still more particularly with telephone systems in which the absorbing arrangement comprises a socalled drop-haelt7 selector-i. e., a selector which responds to a digit and then restores to its normal position after which it responds to the nent digit dialled and selects an idle trunk in the desired level after the fashion ot any ordinary selector.

@ne feature of the present invention is the provision ot' a new and improved circuitar rangement in a` discriminating drop-hack selector which is required to drop hack from a majority of its levels, but not trom the others. Jfrccording` to thisteature, the selector is provided with circuit arrangements which normally cause the selector to drop hack in response to any first digit, in conjunction with vcontacts operated in Vaccordance with the extent ot the tlrst'movement ot the switch in response to such lirstdigit to prevent the dropping hack o'f the selector on a certain level, or certain levels, as the case may loe. I y

There isanother feature of this invention which consists in a new and improved circuit arrangement. for preventing,` the automatic rotary movement trom taking place on levels trom which it is desired to drop hack, and this ar" igjement consists in the provision oi s -controlled contacts for opening;v the circuit ot the rotary magnet when the shaft is raised to a level from which the drop hack is to he made, in conjunction with, contacts on the release magnet i'or maintaining; the circuit ot the rotary magnet open until the shart reaches its normal position.

flnother feature ot1 this case relates to the provision of a new and improved arrangement tor insuring` that the relay which operates in series with the release magnet when the normal position is reached by the shaft ot the selector after it has dropped hack to alosoro a digit does not pull up and open its -fore it is fully released.

Another feature of this case which may he considered as more or less dependent upon the preceding` one, is concerned with the provision ot circuit arrangements whereby the switching relay o'tl the switch is disconnected from the release trunk conductor during] the releasing operation to prevent its energization which would otherwise occur responsive to the grounding ot the release trunk conductor.

Referring now to the accompanying drawings, Fig. l shows a trunlring layoutillustratingl one situation in which the new and improved drop-back selector may he used to an advantage, and 2 is a circuit drawing,` ot a drop-back selector embodying the features oit' the invention.

Referring,` now particularly to Fig. l, this drawing' shows the selector D which is located in an oiiice' of a multi-oliice network embracing not more than ten automatic otlices ot an ultimatecagacity of 10,000 lines each. t'is assumed, however, that at pres; ent only the #toiiice has` more than one thousand lines assigned and that the other oiiiees are accordingly of one thousand lines capacity or less. That being the case, thousands selectors are required in the #al oiicc but not in the other oiiices.

Trunks leading to thousands selectors in the :,/gtl ol'lice terminate in the 'fourth level oi the selector D. One ot these thousands selectors is the selector E. The hundreds selector F and the connc-zctory El may he used to entend a connection to the line ot' substation A2.

Trunks leadingirom the sixth level of the selector D extend tohundredsseleetors in the sixth oiiice which, at present, has acapacity et not more than 1000 lines. Gneot these trunk lines terminates in the selector F which may be used in conjunction with the connector H to extend the connection to the line of substation A.

The remaining working levels of the selector D are understood to be connected up in a manner similar to the sixth level.

Regarding the selector D itself, it maybe pointed out that this is a standard two-wire selector of the usual vertical and rotary type with certain eXtra equipment consisting of an added relay 2l and the shaft springs which operate on the fourth level, together with certain other circuit arrangements, all of which co-operate together to bring about the desired action of the selector which is to release on the calling of any digit unless it is prevented from doing so by the operation of the shaft springs, and to act like any ordinary selector upon the dialling of the next digit in case it releases in response to the dialling of the digit in question.

The invention having been described generally, a detailed description of the operation of the apparatus shown will now be given. For,

this purpose, it will be assumed that the sub scriber at substation A desires to converse with the subscriber at substation A, whose number is 66461. The subscriber at substation A now removes his receiver', whereupon the individual line switch extends the calling line tothe terminals (such as 2, 3, and 4) ofan idle first selector switch, which selector, it will be assumed, is the selector D.

l/illien the selector D is seized, as above pointed out, line relay 22 energizes over conductors 5 and 7 and over the calling line and closes at armature 3l a circuit for release relay 28. Release relay 23 energizes and prepares the switch for operation at armatures 33 and and at armature 32 places ground on the release trunk conductor 6 so as to maintain the line switch C operated.

lhen the calling subscriber turns his calling device in accordance with the first digit in the desired number, in this case the digit 6, line relay 22 deenergizes momentarily for each of the six interrnptions produced in its circuit by the calling device at the calling substation. Each time it deenergizes, line relay 22 closes at armature 3l a circuit through armature 33 and its working contact and the series relay 24 for vertical magnet 47. P the operation of vertical magnet 47, the wipers 48-50 are raised step by step and they come to rest opposite the desired level of bank contacts, in this case the sixth level. Relay 24 is energized in series with vertical magnet 47 upon the first impulse of current being delivered to the latter and, being slow acting, maintains its armature attracted throughout the series of impulses. At armature 39, relay 24 disconnects the grounded release trunk conductor 6 from the off normal contacts 37, se as to prevent the premature operation of release magnet 86. At armature 40, relay 24 closes a point in the circuit of stepping relay 25 which is complet-ed at olf normal contacts 54 upon the first vertical movement of the shaft. This circuit starts from the grounded release trunk conductor 6 and includes armature 88 of release magnet 36 and its resting contact, working contact and armature 40, and. off normal contacts 54. Upon the completion of this circuit for relay 25, relay 25 energizes and closes at armature 4l a. locking circuit for itself which includes the resting contact and armature of switching relay 26, working contact and armature 4l, and the interrupter contacts 55 of the rotary magnet 56, in addition to the off normal `contacts 54. At armature 42, relay 25 closes a point in the circuit of rotary magnet 56.

Since the sixth level is the one called and since the shaft springs are operated on the fourth level, these springs are momentarily operated as the operating portion of the shaft passes by the projection on the shaft spring nearer the shaft. This, however, does not produce any effect, as may be seen upon an examination of the circuit, because relay 24 is energized at this time.

At the end of the ver vical movement on the switch, relay 24 falls back and closes at the normally closed contacts controlled by armature 40, a point in the circuit of rotary magne.. This circuit is not completed at this time, however, because the shaft contacts 9 are open. At armature 39 relay 24 closes a circuit from the grounded release trunk con` ductor 6, through off normal contacts 37, normally closed shaft contact 8, armature 27 of relay 2l and its resting contact, and olf normal contacts 35 for release magnet 36. Responsive to the closure of this circuit, release magnet 36 pulls up and at armature 38 opens a still further point in the circuit of rotary magnet 56 so as to prevent a momentary closure of the rotary magnet circuit at contacts 9 as the shaft passes the fourth level. Armature 3S of the release magnet also connects the release trunk conductor 6 to the release magnet circuit at a point between contacts 9 and armature 27, thereby preventing a momentary opening of the re lease magnet circuit at contacts 8 as the switch shz t passes the fourth level on its way 'to its normal position. As a further result of the energzation of the release magnet, the shaft of the switch is restored to its normal position, whereupon olf normal contacts 35 and 54 are opened. Contacts 54 open the circuit of relay 25 which accordingly falls back ind disconnects rotary magnet 56 at armature 42 and opens a further point in its previously closed locking circuit at armature 41.

@if normal contacts 35 open a point in the Cil contacts (not shown) in that level, which are the contacts in which the line ot substation A terminates. The usual ringer at the called substation is now actuated over the called line by the connect-or l-l in the usual manner.

When the called subscriber removes his receiver, the ringing` current is removed and the talking connection is completed in the usual manner, whereupon the two subscribers may converse with each other as desired.

lll/Then the conversation is terminated, the two subscribers replace their receivers with the result that the ground potential is removed trom the release trunk conductor of the established connection by the connector H and the ground is accordingly removed from release trunk conductor 52, Fig. 2. Vilhen this occurs, relays 2l and 26 of the selector D fall back. At armature 45, relay 2G closes a circuit through armature 31 and its resting contact, armature B3 and its resting co-ntact, and ott normal contacts 'tor release magnet 36, which thereupon energizes and restores the switch to its normal position. rlhe circuit of release magnet 36 is opened at oit normal contacts 35 when the normal position is attained. It will be noted that the lower winding of relay 2l is disconnected from around the ott normal contacts 85 at armature 34 of release relay 23 at this time so as to prevent any interference with the releasing operation.

Considering now a call from the line ot' substation A to the line ot substation A2, and assuming that, when the subscriber at substation A removes his receiver, the line switch C selects the selector D as hereinbe'fore described and that the selector D is accordingly prepared for operation in the same manner as before. The dialling of the first digit fl in the desired number results in the transmission of tour impulses to vertical magnet 47 through series relay 24 with the result that the wipers Lrg-50 are raised oppo-V site the fourth level ot bank contacts. Since the otllce in which the line ot substation A2 terminates is a fully equipped ten thousand line othce, no digit is to be adsorbed at this time. Therefore, the shaft springs are operated by the switch shattat this time to prevent the absorbing ot the oilice digit. The contacts 8 open a point in the circuit through which release magnet 36 was previously operated to restore the switch to normal at the end of the iirst digit, `and the contacts 9 close a point in the circuit of the rotary magnet 5G so that the rotary magnet may operate as soon as the series relay 24C falls. back at the end of the digit. For the salte of clarity it may be well to mention that the circuit of rotary magnet 56 at this time is as follows: from ground by way of the grounded release trunk conductor 6, armature 3S and its resting contact, normally closed contacts controlled by armature 40, the fourth level shaft con:

trolled contact 9, working contact and armature 42, and rotary magnet 56 to battery. The operation ot the rotary magnet 56 and the subsequent operation of the selector is the same as described hereinbe'lore, and assuming that the selector E is the one seized, this selector, together with a hundreds selector (tor example, the selector F) and a connector (for example, the connector H) are operated to extend the connection to the line of substation A responsive to the dialling et the remaining tour digits l, 8, 9, and 0.

At the end ot the ensuing conversation, the connection is released in the usual manner.

Regarding the arrangement for maintaining the release trunk conductor 6 grounded during the regular releasing operation of the selector, it will be remembered that, when ground is removed from the release trunk conductor of the trunk upon which the wipers of the switch are standing, relay7 26 falls back and closes at armature Ll5 a circuit through armatures 3l and 33 and otll normal contacts 35 tor release magnet 36; Also, relay 2l is unlocked and falls back in case it is operated t this time. Release magnet 86, upon energizing responsive to the closure of its circuit, closes at armature 38 and its front contact a point in the circuit through which it is locked to the release trunk conductor `during the dropbacl release of the switch. At this time, however, since the regular release circuitis closed, and since release trunk conductor 6 is not grounded otherwise, the eilect is entirely ditlerent; the release magnet is not locked up to the release trunk conductor 6, but instead the ground potential which is being supplied to the release magnet through armatures 3l and 33 is extended through the resting contact and armature 27 of relay 2l and the working contact and armature 38 to release trunk conductor 6 to maintain the selector D busy during its releasing operation. lt will be noted that armature 38 disconnects the lower terminal of the switching relay 26 trom the release trunk conductor G at its resting contact so as to prevent an energization ot relay 26.

TNhen the switch reaches its normal position, oil normal contacts 535 open the circuit of release magnet 36, whereupon release magnet 36 falls back and disconnects release trunk conductor G trom ground and connects it to relay 26 again. l

lt will be appreciated that ii' it were not for the provision oi' the above explained arrangement lor preventing a possible seizure of' the selector D during its releasing operation, such a seizure might well occur with the result that relays 22 and 23 mightbe energized by the time the normal posit-ion ot' the switch is reached, which case relay 2l operates prematurely (and locks up) because its lower winding is placed in multiple with ott normal contacts 35 by armature 34 ot relay 23. The

might be made higherand in thatrcase be likelihood of this occurrence, however, is ob- ,viated in the manner above pointed out.

Regarding the utility of the resistance element 29, it may be pointed out that, in many cases, double wound relays arek available which have their low resistance windings placed upon the armature end ot' the cores and their lock-ing,` windings uponthe heel end of the cores. A relay of this type is usually wound so that the low resistance winding has sutlicient turns to produce a comparatively heavy pull when the winding` is inserted into the circuit in series with the release magnet. lt, has been found by experiinentthat the flux generated by this low resistance winding is suflicient to attract the armature ont the relay so quickly thatthe relay operates to close its locking circuitaiid toopen the circuit ci its energizing winding with the portion et the core encircled by the locking winding practically unmagnetized and with the armature being,` attracted only by the leakage flux which takes `a path excluding' the heel end of the core. Under such conditions, the magnetism in the armature end of the core dies away responsive to breaking` of the circuit ot the low resistance winding and permitsthe armature of the relay to be retracted before the flux can be built up through the heel end of the core sufficiently to exert a holding` iniiuence upon `the armature. As a result, the lockingV circuit is again opened and the initial circuit is again closed and the relay merely buzzes instead ot operating` `ullyand locking up as desired. u

ln orderto prevent the above occurrence, i

the low resistance winding` or' the relay may be made (in relays constructed esiiecially for operation in this circuit) of a smaller nuinl bei t turns ot wire, so that the flux generated by this winding when it is connected in sei-ies wiih the release magnet ot the switch isnot :liuiiiricnt to operate the armature oil the relay until it has permeated the entire core and heel piece. When the circuit of the locking winding is `closed under these conditions, the this is already built up, and it is vonly necessary Ytor the locking` wii'iding to maintain the established'iiiii; in order to hold the armature in its operated position. Y

ln order to adapt relays for use in this circuit which have not been wound especiallyv tor this'speciiic circuit,vit'is deemed best to shunt the low resistance windingwith the low resistancer element 29 which cuts down the current flow through the windingto such` an extent that the relay operates in the desired 1placed in series with thelower winding of the relay 2l, but, in this case, the releasemagnet Sifi'would probably not remain energized in series with theliigh resistance necessaryvto the lower winding ot the relay tooperate as desired, and there would be a likelihood that the release magnet might fallback and open the circuit oi the lower winding of the relay before sufficient time is allow-ed tor the relay to operate and become locked up.

Vihat is claimed is:

l. In an automatic switch ot the drop-back type, circuit arrangements whereby K `the switch normally restores to its nerim-l `position to absorb a digit, except when a certain digit is called, and contacts controlledin ac cordance with the extent of the movement of the switch when the saine is operated in accordance'witli such certain digit prevent such restoration of the switch tonornnil. i

2. ln a drop-back switcli, circuit arrange ments including contacts at whichthe rotary magnet ,circuit is open and contacts at which the release magnet circuit is closed atthe end oic the primary movement of the selector, said contacts .in the rotary magnet circuit being` closed during the release ct the switch, and contacts fon the release magnet for main- ,tainingl the rotary magnet circuit open until plying? ground to 'said conductor. yduring` Vthe releasing operation e, of the,` selector, and

contacts on said release/magnet ioij disconnecting the switchingv relay fromkthe said release trunk conductor. i, o A

il. In a `Vdrop-back 4switch of the type in which a relay has its winding shunted around oil' normal contacts to efectthe energization of the relay when the :off normal contacts ti'stnaihcd winding` so to adapt the relay tor operation asabovc set tOrth.

5. ln' an automatic switchhaviiig wipers,

means including' a rotary magnet for movingthe wipers from their normal `positiona re lease magnet for restoring' the wipersto their normal position, a guarding` conductor 1for said switch, and contacts on saidrelease maggnet for applyinga guarding potential to said guarding conductor and tor opening` the cireuitof said rotary magnet during the releasin?)` operation.

' (i.V ln Vaftelephone systeiina selector switch,

and means `for operating the same, f said switch primary movement anddeenergized on the vin av primary movement andan automatic selecting secondary movement a y' 'y slow actingrelay energized during the initial cut down the current flow suilicieiitly t'oradapt tor preventing the automatic release of said switch and for starting the automatic selecting secondary movement.

7. In a telephone system, a selector switch and means for operating the same, said switch having a primary movement and an automatic secondary movement, a release magnet for said switch, circuit arrangements whereby a circuit for said release magnet is normally closed after an initial primary movement of said switch to automatically release the same, la relay lor preventing the automatic release of said switch on a subsequent primary movement, contacts on said release magnet and contacts on said relay, an energizing circuit for said release magnet including said relay contacts, a locking circuit for said release magnet including said relay contacts and said contacts on said releasemagnet, and an energizing circuit for said relay including the windings oit said release magnet and relay in series.l

8. In a digit absorbing or drop back selectorhaving /rimary and secondary movements, a release magnet, a change-over relay energized during the primary movement and deenergized on the completion thereof, a circuit or said magnet normally closed by the deenergization of said relay to cause said magnet to energize and automatically release the switch, a second relay, contacts on said release magnet closed when said magnet is energized for closing a circuit to operate said second relay, and contacts controlled by said second relay Jfor altering the switch circuits so that a subsequent primary movement will be Jfollowed automatically by the secondary movement upon the subsequent deenergization of said change-over relay.

9. In a telephone system, a selector switch for use in connecting calling and called lines, groups of trunk lines, said switch having directive primary movement to select a group and automatic secondary movement, to select an idle trunk line in the selected group, a stepping rela-yV for controlling the automatic secondary movement, a sufitching relay for electrically connecting said switch with said selected trunk, a circuit for said stepping relay controlled by said switching relay including contacts on said switching relay, an energizing circuit for said switching' relay'includ- `ing the winding and a Contact of said stepping relay, the circuit of said switching relay adapted to be opened at said contact when the stepping relay is energized, and 'a'.shunting circuit for said switching relay including theA said contact in said stepping relay.

l0. In a telephone system, a selector switch and means tor operating the same, said switch having a primary movement and an automatic secondary movement, a release magnet for said switch, a change-over relay energized during the primary movement and deenergized on the completion thereof, contacts on said relay closed on its deenergization for energizing said release magnet to automatially release the switch, a guarding conductor in said switch, contacts on said magnet for Vclosing a locking circuit for itself which is er"- tective until the switch is restored, means whereby the switch may be rcoperated to set lup a connection and can be released thereafter, and a circuit including the said contacts on said magnet tor placing a guarding potential on said guarding conductor during the last mentioned releasing operation. i

il. In a telephone system, a selector switch having primary and secondary movements, means including a rotary stepping circuit for operating said switch to establish a connection, guarding conductor for said switch, a release magnet for said switch, means for placing a guarding potential on said guarding conductor, means in said switch 'responsive to the removal of guarding potential Jr'rom said conductor tor operating sai-d release magnet to release said switch, and contacts on said release magnet for replacing` guarding potential on said'guarding conductor and tor disabling said rotary stepping circuit during the release of said switch.

l2. In a telephone system, a selector switch, means for operating said switch to establish a connection, a release magnet operated to release said switch once during the establishment of said connection and once thereafter, a guarding conductor in said switch, contacts on said release magnetfor closing a locking cir- 'uitlor itself upon its lirst operation, means for opening said locking circuit, and means for placing a guarding potential on said guarding conductor during the last operation of said release magnet, said. last means including said contacts. n

13. In a telephone system, a selector switch, means tor operating said switch, a guarding conductor in said switch, a release magnet in said switch, means for operating said release magnet under dierent conditions to release said switch, and contacts on said release magnet for closing a locking circuit for itself when the magnet is energized under one condition land for placing a `guarding potential on the guarding conductor during the' release of said switch when the magnet is energized under another condition.

lll. In an automatic switch oic the drop-back type having primary and secondary movement-s, circuits normally closed after the primary movementrtocause said switch to restore to normal position to absorb a digit, and contacts controlled in acordance withthe exswitch responsive to a particularly primary 10 e movement.

in witness whereof, hereunto subscribe my name this 29th day of J anuary, A. D.. 1925. n ARTHUR J. RAY.

In Witness whereof, I hereunto subscribe my 15 name this 29th day of J anuary7 A. D. 1925.

RUDOLPH F. STEHLIK.

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