US2299212A - Telephone system - Google Patents

Description

l Oct. 20, 1942. R. E. coLLls Erm.

9 Sheets-Sheet l Filed July 5, 1941 Oct. 20, 1942. R. E. czoLLls r-:rAL `2,299,212

TELEPHONE SYSTEM Filed July 3, 1941 9 Sheets-Shet 2 SENDER CONNECTOR FRAME lvcoMwG rRuN/fs Oct. 20, 1942. R. E. coLLls Erm. 2,299,212

TELEPHONE SYSTEM Filed July 3, 1941 9 Sheets-Sheet 5 fg L il A7' TORNEY Oct. 20, 1942. R. E. coLLls ETAL TELEPHONE SYSTEM Filed July 3, 1941 9 Sheets-Sheet 4 l um QQQ

Lf lv E R E Hmsfr a fl. KOPP @'nui- Ar rom/Ev 0d 20, 1942- R. E. col-.Lis ET A1. 2,299,212

1 TELEPHONE SYSTEM Filed July 3, 1941 9 Sheets-Sheet 5 OFF ICE OFF/CE A Caf# s /NVENTORS -HER y AT TORNEY Oct. 20, 1942. R. E. coLLls ETAL 2,299,212

LEPHONE SYSTEM wwwHUUUUUUUUUvM i LWN R. E. CLLS E. L. GETZ /NVENTORS R E HERSEY O. H. KO'PP A7' TORNEI Oct. 20, 1942. R, E, coLLls ETAL 2,299,212 l TELEPHONEv slYsTEM Filed July 5, 1941 9 Sk'Aeets-SheefI '7 ATTORNEY Oct. 20, 1942. R. E. coLLls ETAL 2,299,212

TELEPHONE SYSTEM Filed July 3, 1941 v 9 Sheets-Sheet B R. E. COLL/S ATT ORNE V oct. 2o, 1942. R E @LUS ETAL 2,299,212

TELEPHONE SYSTEM Filed July 3, 1941 9 Sheets-Sheet 9 l'HlI /NVE/VTORS Rt-HERSEY By O. H. KOPP A T TORN/ *call is routed to an intercept operator.

Patented Oct. 20, 1942 l wood, and Ralph E. Hersey, Madison, N. J., and Ottmar I-I. Kopp, Baldwin, N. Y., assignors to Bell Telephone Laboratories,

Incorporated,

New York, N. `Y., a corporation of New York Application July 3, 1941, Serial No. 400,892

11 Claims.

This invention relates to telephone systems and has for its object to facilitate the serving of special groups of subscribers.

In the crossbar system, conversational connections are established through crossbar switches under the control of common equipment such as senders and markers. 'YA telephone office normally serves a maximum of ten thousand lines for which a predetermined number of switches are required, together with a certain amount of control equipment. Where the arrangement of the community permits, two offices may be located in the same building and it has been sug-V gested heretofore that, in such a case, the control equipment may be arranged to serve both oflices with an economy in the total amount of such equipment required.

On the other hand, there may be groups of subscribers which, although served from a particular oiice, are so located geographically in the area that they require adiierent charging rate than the other subscribers.

In accordance with the present invention, such subscribers are assigned toa denite group of numbers within the ten thousand lines of the oince and in addition are given a distinctive office name; such oces being known as theoretical oices to distinguish them from the remaining numbers with their oice name which constitute the physical oce.

Where interofce calls to such theoretical of-v ces require an extra charge, individual trunk groups may be provided. InV other cases the theoretical and physical oiiices may be reached over the same trunk groups.

In accordance with one feature of the present invention, means is provided in common control equipment for indicating whether an incoming trunk is one individual to the theoretical oflice and preventing the completion of the connection if the number of the wanted line is in the physical oflice and vice versa.

More specifically, registrations are set up in the common control equipment or marker indica'- tive of the character of the incoming trunk and of the group of numbers including the wanted number. -If these indications correspond, the call is completed, but if they do not agree, the These calls are extended over trunks which indicate to the operator whether or not the call reached the terminating 'oiiice over a restricted trunk group.

certain types of ringing to one or the other ofce if desired.

For a more comprehensive understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 shows schematically subscribers lines terminating at three originating ofces, together with the line link, district and voilice frames of crossbar switches, sender link, sender and marker at one office;

Figs. 2 to 9, inclusive, disclose such portions of the equipment of the terminating oices as are necessary to an understanding of the invention; Fig. 2 showing schematically a plurality of incoming trunk circuits, a terminating sender link and controller for associatingl any incoming trunk with an idle terminating sender, and relay equipment for transmitting to the terminating sender an identification of the group of incoming trunks seized for the completion of a connection;

' Fig. 3 showing the means for transmitting to the In addition means is provided for restricting marker an indication of the nature of the incoming trunks; Fig. 4 showing an incoming link frame and two number group units; Fig. 5 showing a plurality of line link frames in each of two line choices and subscribers lines terminating in three oiiice units; Fig. 6 showing such portions of the terminating sender as are of particular interest in connection with the present invention and a marker connector by which an idle terminating marker is associatedwith the sender; Fig. 7 showing the marker equipment for checking the trunk class against the number group and Figs. 8 and 9 showing further marker relays and circuits; and

Fig. 10 is a chart indicating how the several figures of the drawings should be arranged to completely disclose the invention.

In the disclosure it has been assumed that the incoming links, line choice connectors, line links, senders and markers are common to two oices, A and B, one of which, namely oflice B, is further divided into a physical oice BP and a theoretical office BT. In order to illustrate the operation of the circuits for a number of types of trunk groups, three originating oilices X, Y and Z are indicated. Ofce X is represented as a full selector crossbar oilice and has groups of trunks individual to office A, oflce BP and oiiice BT. Oice Y is represented as a vmanual oflice and has a group of trunks individual to oice A and a second group common to oiiice BP and oiiice BT. Olice Z is represented as a full selector States Patent 2,232,371 to J. W. Dehn et al.,

February 18, 1941, and to United States Patent 2,261,370 to R. E. Hersey et al., November 4, 1941. In general, the operation of the system is as follows: Upon the initiation of a call, for example on line |20, the line is extended by the primary and secondary line switches to an idle district junctor, and through the primary and secondary switches of the sender link to an idle originating sender. When the subscriber dials the wanted line designation, the digits of the designation are registered in thel sender, an idle marker is attached to the sender by the marker connector and the oillce designation is transferred to the marker. The marker in turn connects, by means of a frame connector (not shown), to the district frame. It translates the oicedesignation and operates a route relay. Under the control of this route relay, it connects with the ofce frame having access to van idle trunk extending to the wanted ofiice, selects an idle channel between the district junctor and the idle trunk and releases. I'he functions above described take place substantially as described in United States Patent 2,235,803 to W. W. Carpenter, March 18, 1941.

According to the previous assumption, oiice X v is connected with the terminating ofce building by three groups of trunks. One trunk in each group has been indicated, trunk |24 belonging to 40 lished over which the digits of the registered.

the group individual to oiiice A, trunk |23 to the group individual to ofiice BP and trunk |22 to the group individual to omce BT. y

Assume further that thel wanted line is in oilice A,v and that the call has been extended to trunk |24 which terminates in incoming trunk circuit 224. When the connection reaches trunk circuit 224 the trunk operates relay 233 which initiates the connection of trunk 224 over a set of conductors indicated by conductor 228, a primary sender switch 240 and secondary switch 24|, conductor 228 to an idle terminating sender such as that Of Fig. 6.

In addition relay 233 grounds conductors 242 and243 to identify the frame on which trunk 224 is located and grounds conductor 244 to indicate that the incoming trunk is individual to omce A. When the sender is seized ground is connected to conductor 248, operating relay 602 to connect the sender equipment with the sender link circuits. At the same time relay 2 38, which is individual to this sender groupin the link cir- 60 cuit, is operated, connecting conductors 242, 243

and 244 to conductors 245, 246 and 241, respectively. f

With relay 602 operated, conductor 245 is extended to the winding of relay 603, conductor 246 is extended to the 'frame register and conductor 241 is extended to the winding of relay 6|0. Relay 803 locks to conductor 606 and relay 6|0 locks f to conductor 6|4, lconductors 606 and 8M being grounded under the control of off-normal relay 6|2. The operation of relay 603 indicates that the number of the frame on which trunk circuit 224 is located is less than ten while the setting of the frame register records the units digit o1' the vframe number. The operation relay 6|0 indicates that the incoming trunk is individual to oflice A. y

Both relays 603 and 605 and both relays 6|0 5- and 8|,l should not Ilue simultaneously operated and therefore, with relays 603 and 8|0 operated and relays 605 and 8|| not operated, a circuit is established for relay 8|3 extending from battery through the winding of relay 6 I 3, upper i'ront l contact of relay 6| 0,*back contact of relay 6H, back contact of relay 605 to ground. Relay 6|3 operates, locks under the control of relay v6|2 and conditions the sender for operation. As fully disclosed in the Patent 2,089,921` to Carpenter l lhereinbefore referred to, the terminating sender proceeds to transmit series of revertive impulses to the originatingsender of Fig. 1 to satisfy the sender with respect to its numerical digtt registration. -Five series of impulses are transmitted, the second of which is recorded on the incoming group register 630. For a call to olce A the precise numerical designation is of no interest, but it may be noted that one of the lower four crosspoints will be closed, for example cross-point 63|. When the complete numerical designation has been transferred, a signal is transmitted to the originating sender to cause its release and the terminating sender is associated lwith an idle terminating marker over the marker connector 620. It will be assumed that the marker shown in Figs. 7, 8, 9, and the lower part of Fig. 3 is available and becomes connected with the sender of Fig. 6. Following the connection of the marker with the sender, circuits are closed for transferring the numerical and frame designations to the marker, and for giving the marker an indication of the oiiice in which the called line is located.

Upon the association of the sender with the marker, a plurality of control circuits are estab- Whether the hundreds digit is greater or less than' fly@` by operating relay 8 i8 for digits greater than ve and indicates the position of the digit in either series by operating one of ve relays such as relay 820. The thousands relay 8| 5 marks one of ten conductors, such as conductor 82|, which is extended to either conductor 852 or 853 according as relay 8| 9 is oris not operated.

The tens register represented by relay 8|'| discriminates between even and odd digits by operating relay 826 for odd digits and identies blocks of twenty'numbers by operating one of a set of five relays such as relay 821 which in turn operates relays such as relay 828. The units register relay 8|8 grounds one of ten conductors which are extended toftwenty conductors according to the operated or non-operatedcondition of relay 826. Theframe register 604 transfers its registration to a frame register in the marker repreconductor 624, upper front contact of relay 603, 'l

conductor 625, through the marker connector 620, conductor 805, to the winding of relay 808.

Ground on conductor 803 completes a circuit frame relay 84,0.

' through the marker connector 620, to conductor 623, inner right contact of cross-point 63|, conductor 626, lower contact of relay 6|0; conductor 621, through the marker connector 620 to conductor 801, Winding of relay 8| to battery. A fter the completion of the test, ground is removed from conductors 88| to 804 and relays 808 and 8|| release.

Following the release of relay 8|| ground is connected to its armature, completing a circuit over the back contact of relay 8| to the Winding of office A relay 8|3 and battery. With relay 8|3 operated conductors 852 and 858 are extended to the windings of relays 822` and 823. Therefore, the joint operation of the thousands and hun dreds register relays and oice A relay 8|3 identies one of twenty groups of lve hundred lines each by operating one of the set of twenty relays such as relays 822 and 823 allocated to office A. A similar set of relays is provided for omce B.

The joint operation of relay 820 and either relay 822 or relay 823 selects a number of group frame in the oilice unit A by completing a circuit for a marker preference relay such as relay 402 or 406. In each number group connector, there is a marker preference relay for each mark-- er and these preference relays are arranged in a chain circuit so that only one marker can attach itself to a number group frame at a time. As-

suming that relay 8|!) has been operated, a circuit was closed from ground over the back contact of relay 338, conductor 38|, contact of relay 8|5, front contact of relay 8|3, contact of relay 8|3 to the winding of relay 823 causing the operation of relay 823. The circuit of relay 406 is closed to battery'on conductor 330 as soon as frame 40| becomes idle. Relay 406 operates multicontact relay 401, which closes' the necessary circuits between the marker and the number group frame. With relay 401 operated, the hundred block relay 408 is operated under the control of relays 823 and 820, there being one relay 408 for each one hundred numbers included in the number group. With relay 408 operated, twenty block relay 403 is operated under the control of relays 828 and408, there being one such relay for each twenty numbers in the number group frame.

As soon as the number group frame has been seized, ground is supplied to cause the marker to connect with the frame on which the incoming trunk circuit is located. To this end a marker preference relay 308 is operated, when the frame i's free, over conductor 33|, back contact of frame tens relay 808, and the front contact of Relay 308 operates multicontact relay 309 which closes through circuits for testing and operating the incoming switches shown in Fig. 4 and other control circuits in addition to the circuits shown. At the same time a signal is transmitted to the incoming trunk 224 which causes it to connect with the incoming frame connector by operating relay This relay establishes test and control circuits which .are not shown and also grounds two circuits. At

its outer contact it grounds conductor 332 completing a circuit over a contact of relay 309 for relay 3|5 in the marker to indicate that the calling olce, office X, is a full selector type oflice. At its inner contact it connects ground over a contact of relay 300 to conductor 333, theA winding of relay 100 and battery to indicate that the trunk group is individual to a physical oiice (cnice A).

At the number group frame the hundred block test relays.

relay 408 connected ground over a contact of relay 401 to conductor 400, operating relay 10| as an indication that the group of one hundred numbers requires no discrimination, since oflice A includes no theoretical office.

With relays 408 and 401 operated, twentysets of three terminals` each on the number frame 40| such as 4|0 to 4|2 and 4|3 to 4|5 are marked by connecting them to equipment in the marker. For example, terminal 4|0 is connected over front contacts of relays 400 and 401 and the back contact of relay 820 to the winding of busy test relay 83|, while terminal 4|3 is similarly connected over a back contact of relay 830 to the winding of busy test relay 832. The corresponding terminals on the other eighteen sets are also connected to intermediate relays in the set of busy Terminals 4| and 4 4 are connected to armatures of selecting relays 829 and 830, respectively, and the corresponding terminals of the remaining sets are connected to armatures of intermediate relays of this group. Terminals 4|2 and 4|5 lare connected over back contacts of relays 828 and 830 to the windings of relays 833 and 834 which become effective only in case of terminal hunting groups.

In order to connect with a wanted line it is necessary to select the choice, the frame andthe level of the frame on which the line is located and also to determine whether the called line is one of a terminal hunting group or not and whether ringingiis to be sent on the tip or ring side of the subscribers line. Therefore, there is provided in the marker a group of line choice relays- 900, etc. there being one for each choice. Since each choice includes four frames with ten levels on each frame, a set of twenty double wound relays 902 to 905 is provided, each pair ofr relays 902 and 003 or 804 and 905, representing one of the ten levels and each relay representing a pair of frames, the two windings of each relay distinguishing between frames of the pair. In

order to diierentiate between the types of service, the line choice relays 900, 90|, etc., have three windings each and are energized over the diierent windings in accordance with ,the type of service to which the line is entitled. Therefore, there is a maximum of thirty conductors leading from the line choice relays and a maxi- :num of forty conductors outgoing from the frame or level relays. These conductors are extended in multiple to all of the number frame connector relays such as 401, 403, 451 and 453 and over contacts of these relays to sets of terminal strips on the number group frames. The operating conductors 306, 801 and 908 for relay 900 extend to terminal strips 4|1, 4|8 and 4|9 and similarly the operating conductors 909 to SI2 for the frame level relays 902 and 003 are connected over contacts of relay 401 to terminal strips 420 to 423, it being assumed that connector relay 401 is operated.

The subscribers line 530` of the oli'ce unit A Where it enters the office is connected to a distributing frame 503 from which the line is extended to one of the primary line switches 50| in accordance with the traflic requirements. The line itself is connected to the line terminals 504 and 505 while individual to the line terminals 504 and 505 are the sleeve or busy terminal 506 and the message register terminal 501,

At the number frame, assuming that the set ated, operates horizontal level relay 5H.

minal 506 individual to the position in the primary switch 50| assigned to the line 630. According to the present disclosure line 5,30 appears in the No. level of the No. 0 frame in the No. 0

choice andv is an individual message rate line. Therefore, terminal 4I| is connected over jumper aaoaaia 425 to strip 420 and terminal 4|2 is connected A over jumper 426 to strip 4| 1.

When'the twenty block relay 409 operates as above described, 'the sleeve test circuit for line 530 extends from battery through the Winding of relay 83|, back contact of relay 829, over front contacts of relays 401 and 409, terminal 4|0,

i jumper 424, to the sleeve terminal 506 individualto the line. If the line is busy relay 83| operates fromr the busy ground on-the sleeve of the line. At the same time, battery through the winding of relay 833 is connected over the back contact of relay 829, conductor 836, over contacts of relays 401 and 409, terminal 4|2, vthence over jumper 426, strip 4|1, contact of relay 401, conductor 906, left Winding of relay 900 to battery. Therefore, relay 833 does not operate. After an interval to permit the busy test relays 83|, 832, etc. tor operate, relay 340 operates and ground is 'connected over the front contact of relay'340, back contact of-relay 339, to conductor 342, and thence under the control of the units register to conductor 835, thereby operating relay 829, provided relay 83| is not operated. With relay 829 operated, ground is connected to conductors-836 and 831. Conductor 836 extends to terminal 4|2,

' lays. The marker tests the check relays against stricted group, a circuit is closed from ground' over the lower front contact of relay 315, conductor334', inner left contact of relay 10| to conductor 104 which leads to the operating circuit for the trunli: ringing relays and the check'rei the ringing registration, releases a relay in the jnnctor to permit it to connect with the incoming thence over jumper 426, strip 4|1, lconductor 906,

left winding of relay 900 to battery.AV Relay 900 aoperates over this circuitr to identify the No. 0'..

line choice and thereupon extends its operating ground tothe Winding of relay 9|3 .to indicate that the wanted line is to be handled as an individual line. Conductor 831'extends to terminal 4||, thence over jumper 425 to strip 420, conductor 909, left winding of relay 902 to battery.- Relay 902, upon operating, identies the No. 0 level and extends its operating ground over its inner left contact to the winding of relay 9I4 to identify the No. 0 frame. It may be noted that relays 9|4.

toA 9|1 represent'the four frames of a choice and are operated from the corresponding energizing circuits for each pair of frame level relays.

With relay 900 operated, if the incoming con-l nector has been operated, the No. 0 lline choice isv selected by operating the marker preference relay 508 individual to the marker shown in the No. 0 line choice connector. The marker preference relay operates the multicontact relay 509 which extends all of the control circuits from the marker through to the choice. 'I'he frame-relay 9|4 closes a circuit from ground through the winding of relay 9|8 to the winding of relay 5|0 which is individual to the No. 0 frame, over equipment (not shown) which determines whether the frame equipment is free to handle a terminating call. Relay 9I8 operates if the frame equipment is idle and connects ground to the outer left contacts of the level relays 902, 904, etc. and, since relay 9021s assumed to be oper- Relay 5H connects the operating circuits for the ten select magnets, corresponding to the ten line junctors which serve the wanted line, through to the marker where one-will be selected as described in detail in the Dehn et al. patent. The hold magnet 5|2 of this line is operated over the front contact of relay 829 after an idle channel has been selected.

When the class relay such as relay 9 I3 is operswitches and then releases.

If the subscriber at oiiice X wished to call a subscriber in oiilce BP, one of the group of trunks |23, terminating in trunk circuit 223 would be se lcted. Trunk circuit 223 operates relay 235 which for convenience is shown as grounding the frame identifying conductors 242 and 243 which were grounded previously. Relay 235 also grounds conductor 250 which vis extended by sender group relay 238 to conductor 248. When relay 6020:)- erates, relay 6H operates over conductor 248 and locks to conductor BIE. When the sender and marker are connected,relay 6H connects direct ground to conductor 621 so that relay 8H 4remains operated. after the temporary ground is removed from conductors 80| to 804. With relay 8|| held operated, oilce B relay 8|4 is operated in place of:relay,8l3 to prepare the circuits of the relays 824, 825, etc. in place of relays 822, 823, etc. Assuming that the same number has been registered, the five hundred group relay 825 is' operated, followed by marker preference relay 456. Relay 456 operates multicontact relay 451 whereupon hundred block relay 458 and twenty block relay 459 are operated. Hundred. block relay 458' connects groundto conductor 46|, completing a circuit for relay 105.

In the incoming connector, trunk circuit 223 operates relay 302 which again operates relay 3|5 4to indicate that the calling oiice is a full selector olce, and grounds conductor 333 to operate relay 100 to'indicate that the incoming trunk relates With rel y 105 operated from the number group 'Y to a physlel ofce.

and relay operated from the incoming connector, the ringing control circuit extends Vas previously traced to conductor 334, jover the middle left contacts of relays 100 and 105 to con- I ductor 104.

For a call to the theoretical oillce, oilice BT, one of the group of incoming trunks including trunk circuit 222 is used. Relay 236 is operated, grounding conductor 250, which results in the operation of relay 8|| as before. In this case a number is registered which is within the group constituting the theoretical office. Assuming that this group of numbers is the one hundred numbers to which hundred block relay 454 is 'in-- ated, the ringing control circuit extends as above,

traced to conductor 338, over the middle left contacts of relays 101 and '|06 to conductor 104.

It may be noted that the lines constituting the theoretical oilice may be located anywhere desired in the office unit, since the number group transmits the necessary information for selecting these lines in the same manner as for the physical lines.

The physical ofiice BP and the theoretical oflice BT being really portions of the same ten thousand line oilice unit, it would be possible to reach a line in either of these ofilces from any trunk incoming to the unit. Since the purpose of establishing the theoretical oiice is to cause the oilce unit to be selected over trunks equipped to make a special charge, means must be provided to discriminate between the two olces.

As above described, trunks incoming to omce A or to physical oilce BP operate relay 100, while trunks incoming to theoretical ofiice BT operate relay 101.

From the number groups of oilice A, which has no theoretical omce, relay 10| is operated to indicate that no discrimination is required. Physical oiilce number groups constituting oice BP operate relay 105, while the number groups in the theoretical oilice BT operate relay 106. Y

If now, a subscriber dials the code of the oice BP followed by a number in office BT accidentally or in an attempt to avoid the charge, relays 100 and 106 will be operated. Relay '|00 closes an obvious circuit for relay 102 which locks to ground over conductor 103. Relay 102 also extends ground from conductor 103 over its second front contact, conductor 109, back contact of relay 320, conductor 336, back contact of relay 10|, outer right` front contacts of relays 106 and 100, back contact of relay '108, conductor 1|0, back contacts of relays 32|, 3|9, 3|4 and 3|3, inner upper back contact of`relay 3H, upper back contact of relay 3I6, upper front contact of relay SI5, to the winding of relay 3|| and battery. Relay 3I| controls the routing of a call to an intercept operatol'. At its outer lower contact it operates relay 338 which opens the circuit of the fivex hundred relay 823, for example, thereby causing the release of the previously operated number frame and in "turn, of the incoming connector and the line choice connector. When all of these connectors are normal, relay 339 operates over the left contact of relay 338. At its upper contacts, relay 3| I prepares circuits for operating a marker preference relay, a hundred block relay, a twenty block relay and one of the group of relays 829, 830, etc. These circuits are completed .by relay 339 and are extended in multiple to relay 8|3 and relay 0IA. Since the call was directed to office unit B. relay 0M will be operated to further extend these circuits in multiple to contacts of relays 102 and 1| With relay 102 operated the circuits are extended to the second group of cross-connecting terminals which are so connected as to cause the calling line to be connected with one of a group of trunks at an intercepting position which are individual to the B physical office.

If y-a call were attempted in which code of oflce BT were,` dialed followed by a number located in.

oflice BP, relays 101, 105 and 1|| would be operated and the circuit above traced for relay 3|| would? be closed, extending in this case from ground to conductor 336 over the back contact of relay 10|, outer right front contacts of relays '|05 and 101, back contact of relay 108 to conductor 1 I 0 and thence to the winding of relay 3| I.l

Intercept relay 3|| is also used for calls from manual ofilces which operate relay 3 I 0, the circuit in that case extending over the back contact of relay 3|5, and the front contact of relay 3|B but otherwise as above traced. Relay 3|2 is used in intercepting calls from a toll oiilce and when operated prepares circuits for selecting one of a group of trunks individual to toll calls appearing at an intercept operators position. Relay 8|3 or 8N distributes the circuits to either A or B oflice and relays '|02 and 1|| further distribute them to physical or theoretical office trunks.'

Since under the present assumption there is no theoretical ofiice associated with oice A, the two outer sets of cross connections controlled by relay 1I| would not be completed. l y

Relay 3|! is also operated whenever an unused number is dialed resulting in the operation of relay SIS or if the ringing relays are not set properly. The latter circuit is indicated as a contact of relay 322 but may be traced in detail in the above-identied Dehn et al. patent.

Relay 3I3 or relay .3M is operated under the control of relay 3|8 if the line called is in trouble and has been so marked by the maintenance force. These relays extend such calls to the in tercepting operators position over different groups of trunks from those employed by relays 3|| and 3|2. Discrimination is made between office unit A and omce unit B but not between the physical and theoretical line groups.

In the case of groups of trunks from ofces for which no discrimination is desired between the physical and theoretical offices, relays such as 306 or 301 are operated in the incoming connector. These relays connect ground over a contact of relay 308 to conductor 331, operating relay 108. This relay closes the `ringing control circuit at its inner left contact and opens the circuit for the intercept relay 3|! at its back contact. Similarly relay 10 I, which operates from number groups requiring no discrimination, opens the circuit of relay 3| l.

Relay 'H2 is the four-party ringing control relay. 'Ihis relay is operated, for example, over the third contact of relay 1|I, conductor 1|3, second contact of relay 8N, front contact'of relay BIS to ground. It may also be operated over contacts of relay 102 and contacts of either relay 8|3 or 0M. This circuit is carried over contacts of relays 8|3, 8|4, 1|| and 102 in order to furnish four-party ringing to the ofce units as desired. As shown, it is furnished to all three oiice units but by opening any one of these circuits fourparty ringing may be` restricted to one or two As pointed out in the Hersey et al. patent above identified, if the incoming frames are individual to the A and B ofces so that each oiice will have ten or 'less incoming frames, the frame tens relays 603 and 605 may be used to set up the oiiice registration while relays BII and 6|0 may be omitted or used to control relays 100 and 101 in place of the incoming connector. In that case 75 trunks. Where a trunk group is common to the ing oflice discriminates by adding ve pulses to those normally transmitted for the incoming group selection. For such a registration, one of the upper five cross-points is closed, and direct ground is connected over the inner right contact of the cross-point and the lower front contact of relay 6|0 to conductor 621 to hold relay 8H operated and cause the call to beA routed to office B. f

If morethan one trunk group relay or more than one numbergroup relay is operated a i trouble condition is recorded, the trouble indicator operated and the marker released to permit a second trial. Thus, if relay 108 is operated with either relay 100 or relay 101 a circuit is closed from ground at the right contact of relay 108,

I over the inner left contact of either relay 100'or relay 101 tothe winding of relay 1M and battery. Relay 1l4 calls in the-trouble indicator. If relays 100 and 101 are both operated a circuit is closed from ground over the inner right contacts of relays 100 and 101 to tlie winding of relay 1 I4. Similarly, if relay 10| is operated with either relay 105 'or relay 106 or if relays'105 and 106 are operated together a circuit is completed for lrelay 1M, thereby insuring the proper functioncontrol equipment to any one of said trunks,

means to connect said control equipment with any one of said lines, switching equipment under the control of said control equipment by which a connection may be extended from any one of said trunks to any one of said lines, and meansl in said control equipment for preventing the connection of a trunk incoming to one of said ofllces with a line in the other of said omces.

2. In a telephone system, a plurality of oiiices,y

trunks incoming to each of 'said oiiices, called ,lines in each of said oilices, control equipment common to saidk oiices, means to connect said control equipment to any one of said trunks, means to connect said control equipment with any one of said lines, switching equipment under l thelcontrol of said control equipment by .which a connection may be extended from any one of said trunks to any one of s'aid lines, means in said contr'l equipment operated by said trunk connecting means in response to connection with a calling trunk for identifying the oilice to which said trunk' is incoming, means operated by said line connecting means to identify the office in which the called line is located and means operated if said two identifying means identify different oflices to prevent the connection of said trunk with said line.

3. In a telephone system, a plurality of ofiices, trunks incoming to each of said omces, called lines in each of said oilices, control equipment common to said offices, means to connect said control equipment to any one of said trunks, means `to connect said control equipmentwith any one of said lines, switching equipment under the control of said control equipment by which a connection may be extended from any one of said Y e 2,299,212 two ciiices, relay 6l0 is operated and the originattrunks toany one of saidlines, means in said control equipment operated by said trunk connecting means in response to connection with a calling trunk for identifying' the office to' which said trunk is incoming, means operated by said line connecting means toidentify the Voiiice in which the called line is located, an operators position, and means operated if said two identifying means identify different oflices to connect said trunk with said operators position. Y

4. In a telephone system, a plurality of offices, trunks incoming to each of said offices, called lines Yin each of said oiices, control equipment common to said oices, means to connect said 'control equipment to any one of said trunks,

means to connect said control equipment with any one of said lines, switching equipment under the control of said control equipment by which a connectionm'ay be extended from any one. of said trunks to any one of said lines, means in said control equipment operated by said trunk connecting means in response to connection with a 'calling trunk for identifying the oce to which said trunk is incoming, means operated by said line connecting means to identify the oiiice in which the called line is locate'dj, an operators position, means operated if said-two identifying means identify different oiicesvi-to connect said trunk with said operators position, and means at said position to indicate to'Iy which oiice said trunk was incoming.

v5. In a telephone system, an ofce unit identil vlied by one office code, lines terminating at said oice 'unit, a group of lines within said oiiice unit requiring a special charging rate and identied by a second oiiice code, groups of trunks incoming to said office unit individual to each of said oce codes, switching means for connecting an incoming trunk with a wanted line, control equipment for operating, said switching means, a trunk connector for connecting said control equipment with an incoming trunk, a line con-` nector for connecting said control equipment with a called line, means in each connector for setting up a. registration in said control equipment and means responsive to said registrations iorcontrolling the completion of a connection between said trunk and said line.

6. In a telephone system, an office unit identined by one oilice code, lines terminating at said -oice unit, a group of lines within said oice unit requiring a special charging rate and identied by a second oilice code, a group of trunks selectable by said one ofce code, .a second group of trunks selectable by said second oilice code, a third. group of trunks selectable by either of said oilice codes, switching means for connecting an incoming trunk with a wanted line, control equipment for operating said switching means, a trunk connector for connecting said control equipmentv with an incoming trunk, a line connector for connecting said control equipment with a called line, means in said trunk connector operated in accordance with the type of trunk group for setting up a corresponding registration in said control equipment, means in said line connector for setting up a registration in said control equipment indicating that the called line is or is not in said group of lines and means controlled by said registrations for preventing the completion of a connection if a line in said group of lines is called over a trunk of said first trunk group. "g

. 7. In a telephone system, anoiii'ce 'unit identied by one ofce code, lines terminatingatsaid omce unit, a group of lines Within saidgoiice 'requiring a special charging rate and identied by a second omce code, a group of trunks selectable by said one oiilce code, a second group of trunks selectable by said second ofilce code, a

'third group of trunks selectable by either of said office codes, switching means for connecting an incoming trunk with a wanted line, control equipment for operating said switching means, a trunk connector for connecting said control equipment with an incoming trunk, a line connector for connecting said control equipment with a called line, means in said trunk connector operated in accordance with the type of trunk group for setting up a corresponding registration in said control equipment, means in said line connector for setting up a registration in said control equipment indicating that the called line is or is not in said group of lines, meanscontrolled by said registrations for preventing the completion of a connection if a line in said group of lines is called over a trunk of said iirst trunk group and means for permitting the completion of a connection if aline in said group of lines is called over a trunk of said second or third trunk groups.

8. In a telephone system, an oiiice unit identified by one oiiice code, lines terminating at said oillce unit, a, group of lines within said oflice unit requiring a special charging rate and identiiled by a second ofiice code, a group of trunks selectable by saidv one cmce code, a second group of trunks' selectable by said second oiiice code, a third group of trunks selectable by either of said oiiice codes, switching means for connecting an incoming trunk with a wanted line, control equipment for operating said switching means, a trunk connector for connecting said control equipment with an incoming trunk,a line connector for connecting said control equipment with a called line, means in said trunk connector operated in accordance with the type of trunk group for setting up a corresponding registration in said control equipment, means in said line connector for setting up a registration in said control equipment indicating that the called line is or is not in said proup of lines and means controlledby said registrations for connecting said incoming trunk with a trunk leading to an operators position `if a line in said group of lines is called over a trunk of said rst trunk group.

9. In a, telephone system, an oillce unit identield by one ofiice code, lines terminating at said oiiice unit, a group of lines within said oilice unit requiring a special charging rate and identied by a second ofiice code, a group of trunks selectable by said one omce code, a second group of trunks selectable by said second oiilce code, a third group of trunks selectable by either of said ofilce codes, switching means for connecting'an incoming trunk with a wanted line, control equipment for operating said switching means, a trunk connector for connecting said control equipment v with an incoming trunk, a line connector for connecting said control equipment with a called linel means in said trunk connector :operated in accordance with the type of trunk group for setting up a corresponding registration in said control equipment, means in said line connector for setting up a registration in said control equipment indicating that the called line-is or is 'not in said group of lines and means controlled bysaid registrations for connecting said incoming trunk with a trunk leading to an operators position if the code of said trunk group and the code of the called line do not correspond.

10. In a telephone system, an oiilce unit identiiied by one cnice code, lines terminating at said oiilce unit, 9. group of lines within said oice unit requiring a special charging rate and identiiied by a second oice code, a group of trunks selectable by said one oice code, a second group of trunks selectable by said second oice code, a third group of trunks selectable by either of said oice codes, switching means for connecting an incoming trunk with a wanted line, control equipment for operating said switching means,

a trunk connector for connecting said control equipment with an incoming trunk, a line connector for connecting rsaid control equipment with a called line, means in said trunk connector operated in accordance with the type of trunk group for setting up a corresponding registration in said control equipment, means in said line connector for setting up a registration in said control equipment indicating that the called line is or is not in said group of lines and means controlled by said registrations for connecting said incoming trunk with a trunk leading to an operators position if the code of 'said trunk group and the code of the calledv line do not correspond, and means under the control of said trunk group registration to select the trunk to the operators position.

11. In a telephone system, an oiiice unit identifled by one omce code, lines terminating at said omce unit, a group of' lines within said cnice unit requiring a special charging rate and identified by a second oiilce code, a group of trunks selectable by said one office code, a second group of trunks selectable by said second ofiice code, a third group of trunks selectable byeither of said oiiice codes, switching means for connecting an .incoming trunk with a wanted line, control equipment foroperating said switching means, a trunk connector for connecting said control equipment with an incoming trunk, a line connector for connecting said control equipment' with a called line, means in said trunk connector operated in accordance with the type of trunk group for setting up a corresponding registration in said control equipment,v means in said line connector for setting up a registration in said control equipment indicating that the called line is or is'not in said group of lines and means controlled by said registrations for connecting said incoming trunk with a. trunk leading to an operators position if the code of said trunk group and the code of the called line do not correspond, and means under the control of said trunk group registration tov select a trunk to said operators position individual to the type of incoming trunk.

, RAYMOND E. COLLIS.

EMIL L. GETZ.

O'I'I'MAR H. KOPP.

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