US2421717A - Automatic telephone system - Google Patents

Description

N. H. SAUNDERS AUTOMATI C TELEPHONE SYSTEM June 3, 1947.

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AUTOMATIC TELEPHONE SYSTEM Filed April 28, 1945 17 sheets-sheet -14 CLI sS-/vs ver I June 3, 1947.

` N. H. SAUNDERS AUTOMAT I C TELEPHONE SYSTEM Filed April 28, 1943 17 shets-sheet 15 /YSG .7 27m/5127702.- /bPmanHUndez-' June 3, 1947.

N.- H. SAUNDERS 2,421,717 A'UToMATIc TELEPHONE SYSTEM Filed April 2s, 1943 ,17 sheets-sheet 1e el 7 To Homo/Pips 2 ro o CHA/fl June 3, 1947. N, H, SAUNDERS v2,421,717 v ,AUTOMATIC TELEPHOE SYSTEM Filed April '28, 1943 17 sheets-sheet 1'? Eg' y50E Patented June 3, 1947 AUTOMATIC TELEPHONE SYSTEM Norman H. Saunders, Chicago, Ill., assignor to Kellogg Switchboard and Supply Company, Chicago, Ill., a corporation of Illinois Application April 28, 1943, Serial No. 484.886

. l This invention relates to automatic telephone systems, being concerned more particularly with automatic telephone systems wherein a switching stage comprises serially related primary and secondary switches and in which the same primary switches are used to extend calling lines and to GENERAL DESCRIPTION It has been chosen to illustrate the invention as applied to an isolated 100G-line telephone system comprising ten lseparate hundreds groups interconnected through a selector stage, each hundreds group containing its own line-finder and connector switching stages.

' In the illustrated system, the lines in each hundreds group `are divided into ten subgroups of ten lines each, and a separate subgroup of primary links is provided for each subgroup of lines. The primary links are two-way links, in that each may be used to vextend connections both from and to the associated lines.

Calculations show that, for the substantial equivalent of the usual ten percent trunking arrangement, four two-way primary links in each subgroup are sufficient. Since there are ten primary subgroups of links, there are a total of forty two-way primary links serving a hundred-line group.

To complete the line-finder switching stage in a hundreds group, a number of ten-point secondary line-iinder switches are employed. They are termed finder-action secondary switches; they have access to the primary links; and they are interconnected with selector links, extending from the line-iinder switching stage to the selector switching stage. i

It is a feature of the invention that each selector link is provided with a suflicient number '(four) Aof the ten-point switching devices that it can be thereby interconnected with any one of the primary links serving the hundred-line group, whereby the call-handling efliciency of the selector links is increased.

22 Claims. (Cl. 179-18) To complete the connector switching stage at any hundreds group, further ten-point secondary switches are provided for interconnecting the connector links (incoming from the selector stage to the hundreds group) with the above-mentioned forty primary links. These further switches are termed connector-action secondary switches, In keeping with the last-named feature of the invention, four of these connectoraction secondary switches are provided for each connector link, whereby any connector link can be interconnected with any primary link, thereby increasing the call-handling eiiiciency of the connector links.

The selector stage in the present disclosure comprises a separate group of primary and secondary switching devices for each of the hundreds groups of lines, each such group of primary and secondary switching devices being arranged to interconnect any idle connector link of the associated hundreds group of lines with any selector link over which a call is received for such hundreds group.

In the usual ten-percent trunking arrangement herein disclosed, there are ten selector links for each hundreds group of lines, making a total of one hundred selector links for the complete 1000- line system. Each selector link extends to a separate selector and is represented by an eX- tension of that link, termed a selector multiple, extending through the selector into association with the primary switches of the selector switching stage.

The one hundred selectors and selector links are conveniently divided into ten subgroups, each subgroup comprising ten selectors and ten selector multiples.

Within the portion of the selector switching stage allotted to any called hundreds group of lines, a separate subgroup of primary links (four in number) is provided for each of the ten subgroups of selector multiples. These selector primary links are one-way links, being used onlyto extend connections from the associated selector multiples. The portion of the selector switching stage assigned to a given lhundreds group thus compares directly with the line-finder switching stage within a hundreds group.

To complete the port1on of the selector switching stage assigned to a hundreds group, a number of ten-point secondary selector-finder switches are employed. They have access to the associated selector primary links, and they are interconnected with the connector links extending to the connector switching stage of the associated hundreds group.

In keeping with the previously noted feature of theinvention, four of these secondary selectorfinder switches are provided for each connector link whereby any connector link can be interconnected with any associated primary link in the selector switching stage, thereby increasing the call-receiving eiiiciency of the connector links.

In the line-iinder and connector switching stage, and in the selector switching stage, the disclosed arrangement is that each primary link is provided with a separate primary finder switch. Each such primary nder switch is a ten-point switch, having access to the ten lines or selector multiples in the associated subgroup. This arrangement is preferred over an arrangement wherein the primary switches are individual to the lines or selector multiples. The preferred arrangement results, in the illustrated system, in the reduction ofthe number of primary switches in the ratio of ten to four; that is, four primary switches suffice for ten lines.

Other objects and features of the invention will become more apparent as the description progresses.

THE DRAWINGS Referring now tothe accompanying drawings comprising Figs. 1 to 20, they show suicient trunking diagrams and circuit diagrams of the apparatus involved in a system embodying the invention to enable the invention to be understood.

Fig. 1 is a general diagram of a 100G-line telephone system comprising ten hundreds groups of lines arranged according to the previous discussion;

Fig. 2 is a trunking diagram of the switchingstage portions local to hundreds group one of the 100G-'line system;

Figs. 3 to 16 are circuit drawings of certain of the apparatus of Fig. l;

Fig. 17 is a chart showing thesequence of relay-operations in a register such as HR of Fig.y

` Fig. '18 is a code'table showing which of the counting relays of a register,Y are operated for each of the several digit values; i

Fig. 19 shows h'ow the two parts of Fig. 2 are intended to be arranged; and

Fig. 20 shows the way the sheets on which Figs. 3 to 16 are drawn are intended to be arranged.

Figure 1 Referring now particularly to Fig. l, ten hundreds groups are represented respectively by rectangles 1 to 0. Each such hundreds group includes its own primary and secondary equipment -as previously discussed, comprising a line-finder hundreds group.

Cable Iliu carries the selector links from the 'hundreds groups to the selector stage. This cable has a branch incoming thereto from each hundreds group. Each such bra-nch includes ten selector links. For example, the branch incoming from the first hundreds group includes selector links SLI to SLII), while the branch associated with the tenth hundreds group includes selector links SL9I to SLIIJIl. Included within the selector stage are one hundred selectors which terminate the selector links SLI to SLIUI), respectively.

Ten cables are shown outgoing from the selector stage to the hundreds groups respectively. Each such cable carries ten selector links, which extend respectively to connectors within the hundreds group. For example, the cable extending from the selector stage to the first hundreds group carries connector links CLI to CLIU, while cable extending from the selector stage to the tenth hundreds group carries connector links CLSI to CLIIJEI.'

The above-noted trunking arrangement will be recognized as providing the usual ten-percent trunking for each lof the hundreds of a 100G-line system.

Figure 2 Part l of Fig. 2 shows the primary and `seccndary switches comprising the line-finder and connector switching stages of one of the hundreds groups (group 1) of Fig. l, together with connectors CI to CID in such hundreds group.

The switching equipment shown in part 1 of Fig. 2 comprises the line primary `group LP and the line secondary group LS, while the switches shown in part 2 of Fig. 2 comprise the selector primary group SP and the selector secondary group SS.

Part 2 of Fig. 2 shows the first twenty (SI to S20) and the last twenty (SSI to SI00) of the selectors at the selector switching stage, together with the portion of the selector switching stage associated with hundreds group l of Fig. l.

Referring particularly to partY l of Fig. 2, the switches of the line primary group LP comprise forty ten-point primary line finders divided into ten subgroups of four switches each. Of these, subgroups 1 and 2 and subgroups 9 and 0 are shown, the intervening subgroups being omitted for the sake of compactness of the drawing. The switches in any primary subgroup are termed for convenience switches A, B, C, and D. For eX- ample, the switches in thefirst subgroup `of the line primary group LP are indicatedin the drawing as being switches IA to ID, while the switches in the tenth subgroup are indicated asv being switches 0A to 0D.

All of the switches comprising group LP -are similar, the circuits of switches IA to `ID thereof being shown in detail in Fig..9.

The one hundred subscriber lines served by the switches in the line primary group LP yare divi-ded into ten subgroups corresponding to the subgroups into which the primary switches are divided. The lines in the rst subgroup (accessible to the switches IA to ID comprising the first subgroup of primary switches) are lines I-I to I0 within the hundreds group; the lines inthe second subgroup are lines 2l to 20,; the lines in the ninth subgroup are lines SVI to and thelines in the tenth subgroup are lines DI to 00.

Each hundreds group of lines, is indexed .by a separate hundreds digit. VThus, all of the lines in the rst hundreds group have the Vcommon hundreds digit 1. Accordingly. the illustrated subscriber lines II and I0 inthe rst subgroup of hundreds group 1 have the indicated, directory numbers lll and 110, respectively.

Each of the forty primary switches in group LP terminates a primary link accessible to the secondary switches in the line secondary group 15S. These links are represented by the cables LA, LB, LC, and LD. Cable LA contains the ten links terminating in the ten "A primary switches, cable LB contains the ten links terminating respectively in the ten B primary switches; and so forth, to cable LD, which contains the ten links terminating in the D primary switches.

The links in each of the cables LA to LD may be numbered from 1 to 0 in accordance with the respective numbers of the subgroups to which the links extend. For example, the cables in link LA are numbered 1 to 0, and they extend-respectively `to the primary switches IA to A, each such primary switch being located in a separate ten-line subgroup.

The switches making up the line secondary group LS comprise a total of eighty ten-point secondary switches designated respectively AI to A20, BI to B20, and so forth, to DI to D20. The A secondary switches have access in common to the ten primary links in cable LA; the B secondary switches have access in common to the primary links in cable LB; and so forth, to the D secondary switches which have access in common to the links in cable LD.

The first ten switches in each of the subgroups A to D in group LS are specic to the line-iinder switching stage. They are connected by fours with the ten selector links SLI to SLIUv in the associated branch of cable 1000, over which connections are extended to the selector switching stage. For example, selector link SLI is connected in common to the four switches AI to DI 5 selector link SL2 is connected in common to the four links A2 to D2; and so forth, to the tenth selector link SLI D, which is connected in common to the four switches AIIJ to Dill.' Accordingly, each selector link can be interconnected with any one of the forty primary links contained in cables LA to LD, representing respectively the forty primary switches in line primary group LP.

The links outgoing from the connectors CI to CIU toward called lines are termed connector multiples to distinguish them from the connector links CLI to CLID incoming respectively to these connectors. These connector multiples are labeled CMI to CMIU.

The secondary switches I I to 20 in each of the subgroups A to D of group LS are specific to the connector switching stage. They are connected by fours with the connector multiples CMI to CMI 0. For example, connector multiple CMI, the outgoing pat-h of the connector CI, is connected to each of the secondary switches AII to DII;' the connector multiple CM2 is connected to each of the secondary switches AI2 to DIZ; and so forth, to the connnector multiple CMH), which is connected to each of the secondary switches A20 to D20 in group LS, Accordingly, the outgoing path of each ofthe connectors CI to CIU can be connected through the connector stage secondary switches with any one of the primary links contained in cables LA to LD and extending respectively to the forty primary switches in group LP.

Referring now particularly to part 2 of Fig. 2, one hundred selectors (SI to SIDO) are indicated, but selectors S2I to SBI) are omitted for convenience. These. one hundred selectors are divided into ten subgroups of ten selectors each.V The incoming paths of the selectors SI to SIDI) are the selector links SLI to SLI lli] respectively, while their outgoing paths areVv the selector multiples SMI to SMIDU respectively. i

' Cables are shown extending to the right from the illustrated subgroups of selectors. 'I'here are ten such cables, each of which carries ten selector multiples. Selector multiples SMI to SMII) `are carried in the rst of these cables; SMII to SM2!) are carried in the second; and so forth, to selector multiples SMSI to SMI 00, which are car- 'ried in the tenth of these cables.

The selector primary group SP contains forty ten-point primary switches divided into ten sub- -groups 2 to Opas indicated by the associated bracket andlabel.

Forty primary links, associated f respectively with the primary switches in group SP, are contained in cables A to D extending to the selector secondary group SS, ten links in each cable. Cable A carries the primary links associated with the respective A switches in the primary subgroups; cable B carries the links associated with the B switches; and so forth, to cable D which carries the primary links associated with the D primary switches.

The selector secondary group SS contains forty ten-point selector secondary switches bearing designationsfrom AI to DIU. The subgroups A to D of secondary switches have access to the links carried in cables A to D, respectively.

'I'he secondary switches in group SS are connected by fours with the connector links CLI to CLI 0, extending from group SS to the connectors AC I to CIU of Fig. 2, part 1. For example, switches AI to DI of group SS are multiply connected to connector link CLI; switches A2 to D2 are multiply connected with connector link CL2; and so forth, to the switches AI Il to DI Il, which are multiply connected with connector link CLIU. Accordingly, any connector link can be connected, through its associated secondary switches, with any one of the forty primary links contained in the cables A to D extending from group SP to group SS.

It is obvious that the switching operations to be performed incidental to the setting up of connections in a system such as hereinbefore discussed in connection with Figs. 1 and 2 can be performed by switching mechanisms oi' any one of a number yof different constructions. It has been chosen to illustrate the invention as applied to a system employing throughout the vten-point switching mechanism commonly known as the plunger line switch. `Such plunger line switches are well known. For example, they are described in the book entitled, Telephone Theory and Practice, Automatic Switching and Auxiliary Equipment, by Kempster B. Miller, rst edition, published Ioy McGraw Hill Book Company, Inc., 1933. These plunger `line switches are associated together in practice in groups of any size up to one hundred, and a mechanism known as :a master switch is provided to control the selecting operation of the associated group of plunger line switches.

In the above-noted book, a discussion of plunger line switches and of the controlling master switch may be found on pages 32 to 48, the discussion being accompanied by illustrative drawings, Fig-

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