US1595084A - Telephone-exchange system - Google Patents

Description

Aug. 10 1926. 1,595,084

C- L. GQODRUM El AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25, 1924 9 Sheets-Sheet 1 Aug. 10 1926.

c. GOODRUM ET AL TELEPHONE EXCHANGE SYSTEM Filed Nov. 25,.

Aug. 10 1926. 1,595,084

C. L. GOODR UM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25, 1924 9 sheets sheet 5 Aug. 10 1926.

C. L. GOODRUM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25. 1924 9 gh Aug. 10,1926. 1,595,084

C. L. GOQDRUM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25, 1924 9 Sheet //7l/6/770/5Z' 6/20/1931. fiaadmmdfar/JHbsm Aug. 10, 1926. 1,595,084

. C. L- GOODRUM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25, 1924 9 Sheets-Shet 6 Mar/:91. 6004/11/27 dfar/ J. 6115500 I Aug. 10 1926. 1,595,084

(2. L. GOODRUMET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25-, 1924 m fine/27W war/9:1. 6004/0/27 far/J 675500 by 7k Aug. 10 1926. 1,595,084 I c. a... GOODRUM r A,

TELEPHQNE EXCHANGE SYSTEM Original Filed Nov. 25, 1924 9 sheets-sheet s Aug. 10,1926. 1,595,084

7 C. L. GOODRUM El AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25, 1 9 Sheets-Sheet 9 lnrenfarx- Mar/e: L. 6004mm die/l J. 67 80 Fatented Aug. 10, i926.

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PAT]:

I TELEJ?HOI TE-EXCZ-LANGE SYSTEMV Application filed November 25, 1924, Serial No. 752,093. Renewed October 7, 1925.

This invention relates to telephone exchange systems in general and more particularly to telephone systems of the automatic type wherein selectively operable switches are employed in the coi'itrolling' and completion of conversational connections.

The invention is particularly applicable to telephone systems such as s'hpwn and do scribedin the patent to S. B. Williams, No. 1,517,331, issued Dec. 2 192 i, in general to telephone systems wherein coordinate switches are employed for the extension of calling lines. In these systems it has been the practice heretofore to terminate subscribers lines, ascalling lines, in vertical rows of contacts of thecoordinate' line switches, there being a plurality 0t subscribers lines appearing in a single switch. Each subscrib ers line apoearing in one of these switches has access to a number of horia 'ntal link circuits which in turn are accessible to a plurality of trunks leading to successive selective stages. It has also been the practice heretofore to multiple a subscribers line before a number of horizontal links in a particular section of the line switch, and also to multiple each of the outgoing trunks before all the links of this same section. thus a calling line would have access to an idle trunk by means of any one of a plurality of link circuits in any given section of the switch. However, should all the links in this section be busy when the subscriber initiates a call the selection or an outgoing trunk would be temporarily preventedv regardless of the number of idle trunks available.

This invention has for its object, therefore, to provide improved system for extending calling subscribers lines by means of switches automatically responsive to the removal of a receiver at a calling station.

The foregoing object is obtained by haveach subscribers lineappear before all the links in a particular section of t coordi nate line switch and by having each outgoing trunk appear before but one ink in this section.

Ateature of the invention relates to the means for controlling the selection of a trunk which is common to a number of line switches.

A. further feature of the invention resides in the means for testing available paths Fig, 8 shows the temporarily non-available when such a link or trunk 18 unavailable to acalling line.

Other teaturesand advantages of the in vcntion not specifically mentioned will be revealed after a consideration of the following descriptions and the appended claims.

Referring to the drawing, Fig. 1 shows a plurality of subscribers lines which terminate in contacts of the line switches such as shown in Figs. 2, 5 and 8. In the lower por tion of Fig. l is shown a portion of the master controlling equipment normally associable with the subscribers lines shown in Fig. l.

Fig. 2 discloses a portion of a line switch of the coordinate type together with the re maining portion of the master switch shown in Fig. 1.

Fig. 8 in the upper portion shows the cross-point test relays which are associable with the links in the different sections of switch 200 and with the group of trunks 270. This'figure also shows a number of socalled directional control relays.

Fig. 4 shows corresponding equipment to that of 1. In this instance, however, the equipment is associated with a different line switch.

Fig. 5 shows a second line switch of the coordinate type wherein a different group of calling subscribers lines terminate.

Fig. 6 shows the cross-point relays, which are associable with the links of switch 500 and with the trunks in group 280. I

Fig. 7 shows a third group of subscribers lines terminating in the contacts of athird lineswitch. V H

line switch in which the third groupof subscribers lines terminate. I

- Fig. 9 discloses the crossspoint test relays associable'with the links of switch 800 and with the group of trunks 290-. I PT Fig. 1 0 discloses the manner in hichthe various figures of the drawing are to be ar- Reynolds, No. 1,515,785, issued November 18, 1924. T his type of switch consists mainly of a number of vertical rows of contacts each row being controlled by a corresponding Vertically disposed operating member. Arranged for cooperation with the vertical rows of contacts, are a number of horizontal link circuits, each link circuit having an operating member individual thereto. Calling subscribers lines are terminated in contacts of certain of the vertical rows, these rows commonly being known as line Verticals. Outgoing trunks are terminated in contacts of other vertical rows which are known as trunk verticals. Consequently, the operation of a line vertical magnet, a trunk ver tical magnet and a particular horizontal member determine the selective operation of the switch in extending a calling line. For a more detailed description of the mechanical construction and operation of this kind of switch, reference may be had to the above mentioned U. S. Patent to S. B. Williams.

In the drawing are shown a number of these switches namely, switches 200, 500 and 800. An inspection of the drawing will reveal the fact that each trunk is multipled before a corresponding link in each of the switches; and furthermore, that each trunk is multipled before one link in each section of the switches. For example, trunk 221 which is the first trunk in group 2T0, has an appearance before the first link in section 214 of switch 200. This same trunk has an appearance before a corresponding link in a corresponding section of switch 500. The same holds true of the appearance of this trunk in switch 800. Furthermore trunk 221 has an appearance before the first link in section 234: of switch 200, and before a corresponding link in each of the switches 500 and 800. A similar arrangement holds true of the remaining trunks. It will be observed that each subscribers line is multipled to have an appearance before all the links in any one section, for example, line 110 has an appearance before all the links of section 21 1- in switch 200. Similarly, line 410 has an appearance before the group of links including link 501 in switch 500. It will be noted, therefore, that each subscribers line is accessible to all the links of the section before which it is multipled and to all the outgoing trunks in each of the groups 270, 280 and 290. For example, line 110 is accessible to trunks 225, 220, 229, 230, etc., by means of link 217. Line 110 is also accessible to trunks 223, 224, etc., by means of link A similar arrangement obtains with trunk groups constitutes a first, second and third choice for extending a calling line through switch 200. When a subscriber whose line terminates in switch 200, for example the subscriber at station 101, removes the receiver, line relay 103 operates, in turn causing the operation of start relay 202. Relay 202 is individual to the row of contacts as 219, wherein the calling line terminates. Relay 202 operates relay 204:, which looks in series with master relay 109 and prevents a second calling line from being extended until the extension of the line 110 is completed through switch 200. Relays 109, 110, 112 and 113 form part of a master controlling circuit which is normally inclividual to switch 200. This master circuit times and controls the operation of switch 200 to select a trunk in group 2'70. The master circuit having been seized by the operation of relay 109, line vertical magnet 205 is operated as well as the directional relay 303. Relay 303 associates the group of links 21 1 and the trunks in group 2'70 with the test relays 300. Each of the test relays is double wound, the upper winding being con nected to the sleeve conductor of a corre sponding trunk, while the lower winding is associable by means of directional relay 303 with the group of links before which the calling line appears. The particular group of horizontal links to be associated with relays 300 is determined by means of the operation of one of the relays 105, 165, etc. 'lhe test relays are designed to operate when either one or both of their windings are energized, that is, when the upper winding is connected to a busy trunk or the lower winding is connected to a busy link.

Should all the trunks in group 270 or all he links in the selected group be busy when the call is initiated, the selection of a trunk in the second choice group, namely, group 280 is begu However, trunks 280 constitute the iii t choice for switch 500. Accordingly, with all the cross pointrelays 300 operated, a circuit is completed for relay 114;, causing the master circuit of switch 500 to be associated with switch 200. This is accomplished by operating a transfer relay 412, which in turn operates directional relay 601 and releases directional relay 803. Relay 601 associates the test relays 600 with the links in section 21-5 and with the trunks in group 280. Should there e fist an idle cross point, then the proper trunk vertical jun switch, a second choice "for magnet and horizontal magnet in switch 20 are actuated under joint control of the nuts ter circuits of witch 200 and switcl 50. which release when the id e trunk is SEZGQ. Should all the cross point relays 600 be operated when directional relay 601 is actated, indicating that either all linlzs in so; tion 214 or all trunks in group 280 be a third transfer relay is operated. lay 713 causes the master circuit of switcn 700 (which controls the group of trun 290 as first choice) to be associated w switch 200. Relay 601 is thereupon releas and relay 901 operated'instead. l .i associates the linlrs of section an: the trunks in group 290 with test relays 900. Should there exist an idle cross point, the the corresponding relay remains 110i and switch 200 is actuated to seize the trunk in group 290. In this case the seis': of the idle trunk is under joint control it the master circuits of switches W and 700.

Should the calling subscribefis line he l oated in switch 500, then the selection 0: trunk is made in group 280 first choice, or in group 290. as second choice, group 270 as third choice. Similarly, shoind the calling line be located in switch 800, the se lection of an idle trunk is begun in group 390 as first choice, group 270 as second choice and grou 280 as third choice. For example, should all trunks in the first choic of switch 800, nainely, group 200 be busy, transfer relay 181 is operated the mas ter circuits of switches 200 and 800 operate to seize a trunk in group 2?0. Should all trunlrs in group 270 be busy, transfer rely 482 is operated and the seizure a in group 280 is placed under control of the master circuits of switches 5-00 and 800. Thus, it will be seen that any given group of trunks constitutes a first choice torone an other switch another switch.

ud a third choice for still lVhilc the invention has been shown applied to three line switches and three groups of trunks, it is understood that a greater number of switches and the same number of groups of trunks may be employed. .Also for the sake of preserving simplicity in the drawing there has been shown a comparatively number of trunks in a group and each group has been shown occupying but two vertical rows of contacts. In practice, however, afar greater-number of trunks occupying a correspondingly greater number of vertical rows may be employed. it will be noted that the relays of groups 300, 600 and 000, etc.,'are each individual to a trunk even though this trunk is inultipled before a number of switches. @onsequently, the number of cross point test relays is siderably less than the possible number of available cross points through the several line switches. This is accomplished by at hereinafte and the selection 01 a t ll it-h relay 20 i operated pelowing the test rela s to be associated'by nieans 01" the directional relays 301, 302, 803, 601, 602, 603, etc., with the links of any switch. I

Detailed description.

ion the subscriberat station 101 re s the the purpose of initiating a call, line operates by means of a circuit 'nclurles the closed loop or" the call- .;.nd the'left grounded contacts of ut-on relay Assuming that there an idle inlr, such as 21'4", in secs itch 200, then relay 10'? is norexist tion rial, and the-operation or" the line relay completes a circuit from vground throug tie left contacts or" relays 107, 103 andl-Su,

to battery through the winding of start re- 202. Assuming that the master control circuit shown in the lower portion of Figs.

and 2 is idle at the time the call is initi- As soon, therefore, as relay Alas attracted its arinatures, a circuit is completed from ground, through the left ter c ntact of relay 11.1,right cont-acts of relay 113, thence through the normal contacts of elay 109, contacts of relay 1S2, conduct-or right inner contacts of re 202 to battery through the left winding of relay 5204i. Relay 2041 upon attracting its arinatures closes a locking path which may be traced through the right winding and inner right contacts tor 1Z5, winding of relay 109, to gror the normal contacts of relay 110. Belay operates in this circuit. With relay 100 actuated an energizing circuit i coinplet d for directional relay This circuit may be traced from battery, through the winding of relay B03, conductor rightinner armature and back contact or relay 114:,lett ari iature and Iront contac of relay 109 to the grounded conductor Belay 303 out *ds'this re ground through its left armature and front contact to conductor winding; oi relay 119 to battery.

Relay 119 is slow to operate and req lll'CS an appreci contacts. it will be observed that the cir- 'cuit above traced for operating directional relay 503 includes nornial contacts of relay 11 Should there have been no avilable paths to the group of trunl-r 270 appearing in rows and 211, then relay 114: wi-nild 1. o 'g. i be operated in tneinannei to be u d 21 SLlCQ ecing group would be il ll tor the present it may be ass; e that there exi ts such an idle path. relay 114 is non; al and the above tra-e operating circuit is coin leted for relay 80'.

completed through-the vino receiver from the switchhooh,

or". said relay, conductical magnet 205, and through the right winding of relay 203, thence through the left middle contacts of relay 204, conductor 162, right armature and front contact of relay 109, to the grounded conductor 159. Should a subscriber whose line is in a different vertical group from that including line 101, have initiated a call subsequent to the actuation of line relay 103, then the vertical start relay individual to the second group and similar to relay 202 is operated, thus providing a locking circuit for relay 203. In addition, relay 203 in operating brings about the release of start relay 202, thus preventing a second calling line in the first vertical group being extended before the calling line in the succeeding vertical group has been extended.

Horizontal group relays 105 and 106 now operate in a circuit traceable from battery, through their operating windin s in par allel, thence through contacts of relays 107 and 108, right contacts of relay 103, con ductor 157, left outer contacts of relay 201, left normal contacts of relay 112 to the grounded conductor 159. Relay 105 locks through its right winding and locking contacts, thence through the winding of master switch relay 112 to ground as above traced. Relay 112 operates in this circuit. A locking circuit is now completed for relay 106, which may be traced from battery through the left winding and locking contacts of said relay, left outer contacts of relay 105, right contacts of relay 110, left armature and front contact of relay 112 to the grounded conductor 159. Itwill be noted that the above traced circuit is also extended in parallel through the winding of relay 108, which operates. lVith relay 112 operated a circuit is completed from battery through the winding of relay 30d, conductor 152, right contacts of relay 110, left armature and front contact of relay 112, to grounded conductor 159.

It will be assumed that all the trunks having an appearance in vertical row 210 are busy, either as a result of their being connected to calling lines through contacts of switch 200, or through switch 500, or through switch 800. For example, trunk 221 may be connected to line 410 by means of a link, as 501 in switch 500, thus rendering trunk 221 nonselectable at switch 200. Similarly, the remaining trunks which ap ,pear in vertical row 210 of switch 200 and in corresponding vertical rows 510 and 810 of other line switches are assumed to be nonselectable. It will be further assumed that trunk 226 which appears in vertical rows 211, 511 and 811 of the several line switches is the first idle trunk in the first group of trunks 2?0. It will also be assumed that horizontal link 215 is busy, while horizontal links 216 and 217 are idle.

An inspection of Figs. 2 and 3 will render clear the relation of the various cross point test relays to the corresponding trunks. For example, relay 321 is individual to trunk 221 and is in an operated condition when this trunk is non-selectable. Relay 323 is individual to trunk 223, relay 325 to trunk 225 and similarly for the remaining relays. While but two sections of switch 200 are shown and but six trunks terminating therein, it will be understood that there may be a greater number of sections and a greater number of trunks, dependent on traffic conditions. Since trunks 221, 223, 225, etc., in vertical row 210 are busy, then the corresponding cross point relays 321, 323, 325, etc., are operated. Accordingly, the operating circuit for trunk vertical magnet 231 is broken at the upper inner armatures and back contacts of these relays. Since, however, trunk 226 is assumed to be idle, relay 326 individual thereto is normal, and a circuit may be treated from battery, through the winding of trunk vertical magnet 218, conductor 251, contacts of relay 303, conductor 357, upper inner armature and back contact of relay 326, upper inner armatures and front contacts of relays 324, 322, 325,

etc.,in series, conductor 353, left inner contacts of relay 204, conductor 156, contacts of relay 119, to ground through the right armature and front contact of relay 109. lVith magnets 205 and 218 operated, the release of the master switch is initiated, under the control of the timing relays 110 and 113, which are designed to be slow in operating. The period elapsing between the initial energization of relay and the complete operation of relay 113 is suflicient to ,permit a test to be made of the horizontal links in section 214: of switch 200 and to permit the operation of a horizontal magnet corresponding to an idle link in this section. Accordingly, relay 110 is energized by means of circuit which may be traced from battery through its winding, conductor 158, lower inner armatures and front contacts of magnets 205 and 218 to ground. After an interval when'relay 110 has completely attracted its armatures, it closes an obvious energizing circuit for relay 113, which also attracts its armatures after an interval has elapsed. I 7

Since the calling line is accessible to a plurality of links in section 214, including links 215, 216, 217, etc., and since the idle trunk 226 has an appearance before link 217 alone in this section and furthermore, since link 216 has been assumed idle, While link 215 has been assumed busy, it becomes necessary to render link 216 momentarily non-selectable. This is accomplished by the operation of the start wire advance relay 116, which is individual to link 216. Since link 215 has been assumedbusy, relay 115 is ene 'ized through both it igs of magnet lett wlndn of relav 116, contacts of relay 106,

conductor 161, contacts of relay 303, lowermost armature-s and front contacts of relays 32-1: 3 conductor 361, right outer contacts of l .v 114.. to the wounded conductor 150. Should there be other idle intervening lllllKS'bQiWcQll link 2 6 and link 217 the relays similar to relay 116 are energized in circuits corresponding to that already traced tor'relay 116. It to be noted that the resistance or" the left windings or relays 115, 116, etc, is sulliciently high to prevent the operation or" the corresoonding horizontal magnets 225, 226,etc. ltelays 115 and 1 6 lock through their right windings and locking contacts thencethrough the left inner contacts of relays 105 and 108, right contacts of relay 103, conductor 157, left outer contacts of relay 201;, lower outer armatures and front'contacts of magnets 205 and 218 to ground. Sine trunk2 6 is idle, relay 117 ren ains normal when magnet is energized, whereupon a circuit is completed fronrba-ttery through the right winding of magnet 237, right armature and back contracts of relay 117, right armatures and front contacts ot preceding. relays 116-, 115. etc., to ground, as above traced. Magnet 22? completesalocking' circuit traceable from hattery hrough both windings in series with the left winning of relay 117, thence through contacts-in row 210, test conductor of link 21?, contacts in row 211, sleeve conductor of trunk upper outer armature and'back contact of relay 326, lower outer contacts of 30%, upper inner armature and front 5 of relays 324, 322, 325, etc., in seri sto'ground over conductor 353, as hereinoetore traced. Relay 117 does not operate at this time, however, since it is shunted by the original energizing circuit traced for magnetili 'l. The calling line 110 is now cry to ed means. of link 21'? to the idle trunk w ereupon the sleeve conductor of this trunk is maintained grounded at a suc.- roding selective switch, as described in deail in the above me tioned patent to S. B. 'Villiams.

At the end of the interval determined by heoperation of relay'113, when this relay s completely attracted its armature, the iolding circuit for relay 201 and master relav 109 broken, these relays thereupon release. The holding circuit of horizontal oup relay 105 and master relay 112 is also lnoken at this time. The release of relay 20% opens the energizing circuits of relay 203 and. the line vertical magnet 205. Magnet- 205..thereupon restores to normal. Relay 10am relea iopens the energizing circuit of the directional control relay 303, which in turn causes the release of trunk vertical magnet 218. lVith relay 105 normal the shunt is removed from around the winding '11? and this relay energizes in seall 'nhetore traced. Since link 216 was aseration, the locking circuit through the right vinding of this relay is broken by the release of the master switch, thus releasing relay 116 and restoring link 216 to its seloct'ble condition. 1t will be noted, however, that link 215 which was assumed busy when the. master switch was seized, is still ed to he idle at the initiation of the 010- the windings of magnet 237, as

maintained busy by the continued energizetion of the horizontal magnet 235 in series with the left Winding of relay 115 to the grounded sleeve test conductor of the busy link 215. ll ith the in ster switch restored to normal, relay 30% releases, whereupon the shuntis removed from around the upper wining of relay .d this relay now 0 crates in a circuit which may be traced from battery, tirough the upper winding thereof, to the grounded sleeve conductor of trunk As soon as through switch 200, cut-oil relay 104 operates and releases the line relay 103. The connection is now in a stable condition and the master switen associated with frame 200 is rendered available in controlling other connections.

AZZ pat/ts busy in, first group. I

It will next he assumed that both trunks 2 and 226, which are the last trunks appearing in rows 210 and 211, respectively, are alone idle, when the master switch is seized, b 217 givi ac ess to these 311": while preceding linlzs, as 216, The sequence of operations onditions is similar to that alueseriher, as far as the point where iest niadc. In this case, not selectable, line 110 cannot he ezi to either of the trunks and 226, even though these trunks are idle at the time. Accordingly, with relays 303 and 106 operated, s hereinhefore described, a circuit is coi'n leted from battery, through the lower windings of relays and 326 in parallel. contacts of: relay 303, conductor ht inner contac sleeve conductor of link 217. Since link 2 17 is the only link in section 21-1 that gives the calling line access to the idle trunks 225 and 226 and since both these trunks have been thus rendered non-selectable by the operation of relays 325 and 326, line 110 cannot be extended to any trunk in the first group with wnich the master switch shown in Fig. 1 is associable. It will be seen, therefore, that all the cross-point test cs 0t relay 106, thence the connection is'established relays associated with the first group of trunks are operated either as a result of the corresponding trunks being busy or as a result of the available links being busy- Tl'iereforc, it is necessary to perform a test of the trunks in group However, since the selection of a trunk in group 280 is controlled by the master circuit of switch 500. this master circ -.it must be associated temporarily with switch 200. Accordingly with all the cro s-point test relays of the first groin) oper' d, above described, a circuit is completed from battery through the right winding of relay 114i, conductor 656, lower inner arn'iatures and front contacts of relays 326, 324, etc., in series, to ground. Relay 11 1 is as; ciated with switch 200 and is individual to the first group of trunks 270 which includes trunks 221', 222, 223, etc. A locking circuit is completed for relay 11% which may be traced from battery through the left winding and locking contact thereof, thence to the grounded conductor 159. Assun'iing that there exists an idle trunk in group 280, then relay 41% which is individual thereto is normal, and it becomes necessary to associate the master switch shown in Fig. 4t with switch 200. The association of this second master switch is initiated by the operation of transfer relay 4:12. This relay operates in a circuit traceable from battery through its winding, left contacts f relay 126, left armature and back contacts of relay 41 i, conductor 435 right inner armature and front cont ct of relay 114:, left armature and front contact of relay 109, to grounded conductor 159,. Assuming the master switch shown in Fig. l to be idle when relay 4:12 operates, a circuit is now closed through the right winding of relay 4125, left outer armature and front contact of relay 4112, right outer armatures and back contacts of relays 502, 508, etc, in series, contacts of relay 433, right armature and back contact of relay 109, left normal contacts of relay 410, conductor 452, to ground at the armature of relay 111. Relay 125 operates and thereupon closes a locking circuit: through its left winding and locking contact, winding of relay 438, to ground tl'irough the left contacts of relays 410 and 111. Relay 4:33 operates in this circuit and renders the master switch associated with switch 4-00 busy. he preceding circuits were completed under the assumption that no subscriber. whose line tern'iinates in switch 400, had initiated a call at the instant that the master switch was seized by the operation of relay 412. Should such a subscriber have initiated acall immediately prior to the operation of the relay 182, a corresponding start relay 502, or 503, would be operater'l, thus preventing relay 125 from operating: and seizing this master switch. The calling subscriber, whose line terminates in switch 200, must, therefore, await the release of the master switch which is individual to switch 1:00.

i /hen relay 1-25 operates an energizing circuit is closed for relay 126 which may be traced from battery through the left winding thereof, right outer contacts of relay 4-25,

left outer armature and back contact of relay d1 1, conductor 451, rightinner armature and front contact of relay 11st, to ground through the left armature and front contact of relay 109. Relay 496 looks through its right winding and locking contact provided another rela similar to relay 412 is ener gizcd. Bela also closed an operating circuit for d1:ectional relay 601. This circuit may ll-' traced from battery through the winding thereof, conductor 652, right outer contacts of relay 125, left armature and back contact of relay e14, to the groundcd conductor 4:51. Relay 601 extends this same ground through itsleft contacts to conductor 656, thence to battery through the winding of slow operating relay 419.,

The relation of the cross-point relays 627, 628, 629, etc, to the group of trunks 280 is similar to that already described in connection i 'ith relays 321, 322, etc., and the trunks in group 270. The drawing shows trunk 227 as l'iaving an appearance before the first link in section 214, while trunk 229 is shown as appearing before the last link in this same section, it being understood that other trunks will. haveran appearance in row 212, each before a different link in section 2141. A similar arrangement holds truefor the trunks appearing in vertical row 213. It will be assumed that link 217 is the only idle link in section 21d, and that trunks 227, 228 and 230 are the only idle trunks in group 280. Since, however, link 215 which gives access to the idle trunks 227 and 228 is busy, it becomes necessary to render these trunks momentarily non-selectable while a test is being made of the available cross points in switch 200. 7

Since link 215 is busy, a circuit may be traced from battery through the lower windings of relays 627 and 628 in parallel, contacts of relay 601, conductor 651, conductor 152, right outermost contacts of relay 106, to the grounded test conductor of link 215. The operation of relays 627 and 628 renders trunks 227 and 228 momentarily non-selectaale. Since it has been assumed that all remaining links in section 21 1 are idle, it is necessary to render all these links tempo-- rarily non-selectable with the exception, however, of link 217 before which the idle trunk .30 appears. Accordingly, relay 116 is operated by means of a circuit completed from battery through the windings of magnet 236, left winding of relay 116, rightconta ts of relay 106, conductor 161, contacts of relay 601, lowermost armature and front contacts of relays 632 and 631, conductor 653, right outer contacts of relay 414 to ground through the left contacts of relay 410. Similar circuits may be traced for succeeding relays corresponding to 116 and associated with remaining idle links ,in' section 214. The corresponding circuit for operating relay 117, however, -is broken at the lowermost contacts of relay 630, which relay is normal at this time. l/V hen relay .419 has closed its contacts a circuit for trunk bring about the release of the master switch associated with the frame 200. At this time also a parallel operating circuit is com- )leted through the winding of the release relay 410. This circuit may be traced from battery through thewinding of relay 410, right inner contact of relay 425, conductor 455, thence to the grounded conductor 158. Relay 410 after an interval causes relay 413 to operate, whereupon ground is removed from the windings of relays 425 and 433 and these relays release. Relay 425 causes release of directional relay 601. The master switch of Fig. 4 is thus released for controlling other connections. The connection through the switch 200 is maintained by magnet 237 which is locked in series with the left winding of relay 117, contacts or" switch 200 to the grounded sleeve conductor of trunk 230. It will be noted that release of directional relay 601 opens the previously traced operating circuits for the relays 116, etc, associated with the idle links in switch 200. lVhenthe group relay 106'releases the locking circuit of these relays is broken and the same release to render .the associated links selectable.

All pat/ 2s busy-in first and second groups.

tions it will be noted that because of thebusy condition of link 215, trunk 228 can not be selected regardless of its being idle.

The onerations in this case are similar to those already'described in connection with. the selection of a trunk 1n group 280, relay contact of .r

412 operating as already described to asso ciate the master circuit oi switch 500 with lWltCh 200. in this case, however, when the ss-point test is to be made and since trunk alone is assumed to be idle, then all of cross-point relays shown in Figs. 3 and re operated with the exception of relay 28 which is individual to the cross-point deermined by trunk 228 and link 215. i-rcco dingly, when directional relay 601 oper- GDCD I ates as above described, a circuit is closed irom battery through the lower winding of relay 028, contacts of relay 601, conductors 651 and 152, right outer contacts 01 relay 106 to the grounded test conductor of link 215. All the cross-point relays having thus been operated as an indication that no available paths exist to group 280, relay 414 is oper' ated by means of a circuit which may traced from battery through the right wind- J th reof, conductor 655, lower inner ar- .res and front contacts of relay 630, 032, etc, in series to ground. Relay 414 immediately locks through its left winding and locking contact, to ground through the left arinatures of relays 410 and 111. Relay 414 at its left armature and back contact opens the previously described enei lug circuit o1 relay 601 which thereupon releases in turn causing the release of relay 628. All the reiainin cross-point relays shown in Figs.

3 and 6 being maintained energized b means of the grounded sleeve conductors of the associated busy trunks.

The master switch shown in Fig. 7 which is individual to switch 800 is next associated with the third group of trunks 290. Assun. ing that an idle trunk exists in this group. relay 714 is normal, and transfer relay 713 operates, by means of a circuit completed from battery through the winding thereof, left contacts of relay 72*", middle armature and back contact of relay 714, cond .ctor 751', left outer armature and front co tact of relay 414, conductor nence to ground through the right inner armature and front 4 elay i4.

shown in Fig". 7 to be idle t en this'latter relay locks by means oi s cuit completed through its left winding and in l ng contact in series with the winding of relay 715. Belay 715 perates in this circuit and renders the associated master switch busy. Di-

rcctional relay 901 is now operated in a cir cuit traceable from battery .hrough the winding of said relay, conductor 952, right outer contacts of relay 725, left middle armature and back contact of relay 714, to ground over conductor 751 above traced. 901 in turn causes energization of slow operating relay 719. l Vith relay 901 operated the cross-point test relays 900 are associated.

with the group of trunks 290 and with the links in section 214-. In a manner similar to that already described in connection with the cross-point relays of groups 300 and 600, an idle path is determined in section 214 which gives access to a trunk in group 290 and the proper horizontal magnet corresponding to this idle path is actuated. As soon as a trunk vertical magnet, for example magnet 233, is operated ground is extended as hereinbefore described over conductor 158, to operate relay 110, and over conductor 455 to operate relay 410. This same ground is extended by means of conductor 755 and the right inner contacts of relay 425 to the winding of release relay 710. In a manner deemed to be already familiar, rela s 1.10, 410 and 710 bring about the release of the associated master switches and also the release of magnets 20'") and In the foregoing detailen description. it has been assumed that the calling subscribe ers line terminates in contacts of sw .ch 200 with which the master switch shown in the lower portions of Figs. 1 and 2 is rmrinaly associated. Should, however, tln. calling no be located in a different line srmh, for example, switch 500 the s of an idle trunk in group 280 will take plac. since the master circuit of switch 500 is normally sociable with this group of trunks. Should all available paths in this group be busy when the subscriber at station 401 initiates a call, then relay 414 operates. The circuit for operating relay 414 may be traced from battery, through the right winding thereof, conductor 655, thence through the lower inner contacts of all the busy cross-point relays 600 to ground. Relay 414 locks and brings about the release of directional relay 602, which it will be noted is operated in a circuit similar to that hereinbefore described in connection with relay 301. Assuming there to he an idle trunk in group 290, then relay 714 is normal, and a circuit is closed for transfer relay 723. This circuit may be traced from battery, through the winding of relay 723, left contacts of relay 724, left outer armature and back contact of relay 714. conductor 752, r' 'ht inner armature and front cont-act of relay 414, left armature and front contact of relay 4-09 to ground through the left contacts of relays 410 and 111. In a manner deemed to be already familiar, the operation of transfer relay 723 brings about the actuation of directional relay 902 and the subs quent association of the master switch'of Figs. 7 and 8 with switch 500 whereby an idle trunk in group 290 is selected. Should, however, all paths to trunks in groups 280 and 290 be simultaneously busy, then relays 414 and 714 are operated. Relay 714 locks and causes the release of directional relay 902. A circuit is also completed for transfer relay 121 which may be traced from battery, through the winding thereof, left contacts of relay 123, left middle armature and back contact of relay 114, conductor 756,

left outer armature and front contact of relay 714, conductor 752, right inner armature and front contact of relay 414 to ground. Relay 121 causes the successive actuation of relays 122, 123 and directional relay 302. Relay 302 associates the cross-point relays 300 with the horizontal links of switch 500 for the purpose of selecting an idle path in switch 500 as hereinbefore described.

Similarly, should the calling line terminate in switch, 800 then upon the removal of the receiver by the calling subscriber start relay 803 operates in turn causing the operation of relay 804 which looks in series with relay 709. A line vertical magnet as 805 and directional relay 903 thereupon operate and the cross-point relays 900 are associated with the links in switch 800 and with the group of trunks 290. Sho-uld there be an idle trunk in this group, and an available link giving access thereto, then the corresponding horizontal magnet is operated to complete the extension of the calling line. The release of the master switch as brought about by the actuation of relay 710 subsequent to the operation of a trunk vertical magnet as is already described. -The release of the master switch in turn causes the re-- circuit of directional relay 903 which re leases. Should one of the relays 300 be released indicating an idle trunk in group 270, then relay 114 is normal and transfer relay 131 operates. the actuation of directional relay 301 and the association of cross-point relays 300 with the links of switch 800 and the trunks in group 270. Should all the relays 300 be operated, indicating an all-trunks busy condition in group 270, then relay 114- operates in turn releasing relay 301. l-Vith relays 1.14 and 714 operated, a circuit is closed for transfer relay 432 which associates the mas-' ter switch. of Figs. 4 and 5 with the switch 800. Subsequently, a trunk and horizontal magnet of switch 800 are operated should there be an available path to an idle trunk in group 280, and this idle trunkis seized. as already described in detail.

hat is claimed is:

1. In combination, subscribers lines arranged in groups, an automatic switch for extending said lines comprising groups of link circuits corresponding to said groups of Relay 131 brings about.

lines, outgoing trunks each accessible to but one link in each of said groups of links, testing devices for said trunks and each associable with a link in any of said groups of link circuits, and means dependent upon the condition of said testing devices for causing said switch to operate to seize a trunk.

In combination, subscribers lines arranged in groups, an automatic switch responsive to the initiation of a call on any of said lines for extending the same, groups of link circuits in said automatic switch corresponding to said groups of lines, a plu rality of outgoing trunks, each trunk accessible to but one link in each ofjsaid groups of links, testing devices for said trunks and each associable with a link inany of said groups of link circuits, and means for actuating said switch to seize one of said'trunks de endent upon the condition of the assosiated testing devices. 7

3. In combination, subscribers lines arranged in groups, an automatic switch responsive to the initiation of a call on any of said linesfor extending the same, groups of link circuits in said automatic switch corresponding to said groups of lines, a plurality of outgoing trunks each trunk accessible to but one link in each of said groups of links, testing relays for said trunks and each associable with a link in any: of said groups of link circuits, and means for actuating said switch to seize one of said trunks dependent upon the condition of the associated testingrelay. y

4:. In combination, subscribers lines arranged in groups, an automatic switch for ergtending said lines and comprising groups of link circuits corresponding to said groups of lines, outgoing trunks, each trunkaccessible to one link in each of said groups of links, a plurality of testing devices, each associable with a trunk and associable with a link in any of said groups, means dependent upon the condition of said devices for operating said switch to connect a link to a line and to an idle outgoing trunk.

5. In combination, subscribers lines arranged in groups, an automatic switch for extending said lines comprising groups of link circuits corresponding to said groups of lines, outgoing trunks, each trunk forming a cross point with one link in each of said groups of links, testing devices each individual to a trunk and associable with the corresponding link in each of said groups of links, means dependent upon the condition of said devices for operating said switch toconnect a line and to a trunk, and means responsive to said connection for rendering all cross points involving said link non-selectable.

6. In combination, subscribers lines arranged in groups, an automatic switch for extending said lines comprising groups of link circuits corresponding to said groups of lines, outgoing trunks each trunk having an appearance before one link in each group of links, each appearance forming a cross point for completing connections, testing devices each individual to a trunk and as sociable with a plurality of said cross points, and means dependent upon the condition of said testing devices for causing said switch to operate to extend a calling line through an idle one of said cross points.

7. In combination, subscribers lines arranged in groups, automatic switches for ex-- tending said lines, said switches comprising groups of link circuits corresponding to said groups of lines, a plurality of trunks com: mon to all of said switches, each trunk having an appearance before one link in each group of links in all of said switches, testing devices accessible in common to all of said switches and each individual to one of said trunks, means responsive to the busy condition of a trunk for operating the device individual thereto to render said trunk non-selectable at all'of said switches. and means dependent upon the condition of said devices for operating one of said switches to seize an idle one of said trunks.

8. In combination, subscribers lines arranged in groups, automatic switches for extending said lines each switch comprising groups of link circuits corresponding to said groups of lines, a plurality of trunks common to all of said switches, each trunk having an appearance before one link in each group of links of all of said switches, a plurality of testing device-s each individual to a trunk and associable with a link in any of said switches, and means dependent upon the condition of the trunks and the links with which said devices are associated for operating one of said switches to seize an idle one of said trunks.

9. In combination, subscribers lines arranged in groups, automatic switches for extending said lines, each switch comprising groups of link circuits corresponding to said groups of lines, a plurality of trunks common to all of said switches, each trunk having an appearance before one link in each group of links of all of said switches,

a plurality of testing devices each individual to a trunk and associable with a link in any of said switches, and means responsive to the initiation of a call and dependent upon the condition of the trunks and the links with which said devices are associated for operating one of said switches to seize an idle one of said trunks.

10. In combination, subscribers lines ar ranged in groups, automatic switches for extending said lines, each switch comprising groups of link circuits corresponding to said groups of lines, a plurality of groups of trunks each trunk having an appearance in all of said switches, testing devices each individual to a trunk, means for associating certain of said devices with a particular group or" links in any one of said switches, and means dependent upon the condition of said group of links and the corresponding group of trunks for associating in succession other of said test devices with said group of links, for the purpose of extending a line to a trunk in another group of trunks.

11. In combination, subscribers lines arranged in groups, automatic switches for extending said lines each switch comprising groups oi link circuits corresponding to said groups of lines, groups of trunks each trunk appearing in all of said switches, said groups constituting a plurality of successive choices for extending one ot said lines, testing devices arranged in groups corresponding to said groups of trunks, each "device individual to a trunk, means for associating a first group of devices with any group of link circuits, means dependent upon the condition oi said group of link circuits for successively associating other groups of devices with said group of link circuits, and means dependentupon the condition of any group of devices for operating one of said switches to extend a line by means of a link in said group of links to an idle one of said trunks.

12. In combination, subscribers lines arranged in groups,automatic switch-es for extending said lines comprising groups of link circuits corresponding to said groups of lines, groups oi trunks constituting successive groups oi choices i or extending said lines, testing devices each individual to a trunk, means for associating a portion of said devices with a particular group of links in one of said switches, means dependent upon the busy condition of said links in said group and the condition of the first choice trunks for associating other portions of said devices in succession with said group of links to seize a trunk in a succeeding choice group.

13. In combination, subscribers lines ar ranged in groups, automatic switches for extending said lines comprising groups of link circuits corresponding to said groups of lines, a plurality of trunks, eachtrunk ada ted to form a junction with one link in each group of links, testing devices less in number than the number ofsaid junctions, means for associating said devices in succession with diilerent groups of junctions forthe purposeoi making a test thereof, and means dependent upon the finding of an idle junction for operating said switch to seize said junction to extend a calling line there through.

let. In combination, subscrihe rs.,lil es arranged in groups, an automatic'switch in which said lines terminate andxconiprising groups o-filin'k circuits, groups of trunks appearing in contacts of said switch, said trunks and links forming groups of junctions for extending calling lines, testing de vices arranged in groups corresponding to said groups of trunks each device individual to a trunk, means iorassociating a group of devices with a first group of junctions, means dependent upon a busy condition of said first group of junctions for associating in succession other groups of testing devices with remaining groups of junctions, and means effective upon the finding of an idle junction in any group for operating said switch to extend a calling line therethrough.

In witness whereof, we hereunto subscribe our names this 24th day of Nov-ember A; D.,

ARLES 'L. GOODRUM. EAR-L S. GIBSON.

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