US853818A - Automatic telephone system. - Google Patents

Description

No. 853,818. PATENTED MAY 14, 1907.

*P. MERK.

AUTOMATIC TELEPHONE SYSTEM.

APPLIOATION FILED JAN. 2, 1907'.

a SHEETS-SHEET 1.

H mam 57157227 1 J0 Pea-r54 zero/vs PATENTED MAY 14, 1907.

. 110153.818. E. MERK.

AUTOMATIC TELEPHONE SYSTEM.

APPLIOATIONIILED JAN. 2, 1907. I

8 SHEETSSHEET 2.

- Fig.5

. No. 853,818. PATENTED MAY 14;, 1907.

- 1?. MERK.

AUTOMATIC TELEPHONE SYSTEM. APPLIOATION FILED JAN. 2, 1907.

8 SHEETS-SHEET 3 PA-TENTED MAY 14, 1907.

' P. MERK.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JAN 2, 1907.

8 SHEETS-SHEET 5 PATENTED MAY 14, 1 907.

F. MERK. AUTOMATIC TELEPHONE SYSTEM.

KPPLIOATION FILED JAN. 2, 1907.

8 SHEETS-SHEET 6.

PATENTED MAY 14, 1907.

' P. MERK.

AUTOMATIC- TELEPHONE SYSTEM. APPLIUATION FILED JAN, 2 1907.

s sums-sum 7.

C %/?7e0560i JWV677WI/A m w mw PATENTED MAY 14, 1907.

F. MERK.

AUTOMATIC TELEPHONE SYSTEM.

8 SHEETS-SHEET 8.

APPLICATION FILED J'AN.'2, 1907- jwaev/ar' V W M i FRIEDRICH MERK, OF BERLIN, GERMANY AUTOMATIC TELEPHONE SYSTENL.

Specification of Letters Patent.

Patented May 14,1907.

Application filed January 2, 1907. Serial No. 350,386. I

To rt/l Ic/mm it may IIIIMrV-III:

Be it known'that l, Fiunnmcn MERK, telephone engineer, a citizen of the German Elnpire, residing at l lottwellstrasse 7, Berlin, Germany, have invented certain new and use tul lmprovements for Automatic Telephone in stems, of which the following is a specification.

in automatic telephone exchanges from about 100 subscribers upward it IS customary to arrange in groups the subscribers lines in the exchange, and to make coi'lnections from one subscriber to the other or from one group to the other by the aid of trunk-lines. subdivision of the exchanges in groups and the use of trunk-lines is'gcnerally extended the more, so much the larger the number of the subscribers' lines is. Inquite large exchanges main-groups, sub-groups and bygroups etc. are distinguished, whereat the completion ol connections is brought about, so to say, step by step in such a. manner that the complete talking circuit )asses from the calling subscriber tothe called one over a number of trunkl'ines through the desired main-group, sub-group,.by-group etc.

The grouping system widest known. and most developed, to which also the present invention rel'ers, is the Strowger system in which the cl\aracteristic diil'erencc from other systems and the advantage over them consist in the t act that the grou ing of the subscribers is based on the (ecimal system, whereat a 100-, 1000-, 10000- etc. system are distinguished and in which thc number of the trunk-lines between the group's and the switches connected thereto is reduced so nni- I formly that the number of switches, from the second stageof switching, corresponds ap proximately to the number of connections to be made simultaneously. This latter result is attainedby reason of the factthat the trunklines, at all stages of the switching, are connected in multiple to the corresponding selectors, which is a distinguishing feature of my sy'stcm.

.l n the arrangement of groups ai-cording to the decii'nal system mentioned, subscribers sub-groups are chosen as units and thus the switches for each 100 subscribers are joined on one switchlamrd. The number of switches for each switchboard is a little larger in the 1000-system than in the l00 system and again a little larger in the l0000-system than in the l000-syst'e1n. This increase is caused The l by the circumstance that, when changing from one system to the other, one switch and .one trunk-line more is necessary for every single connection. The number of trunk lines per connection in the 100-syste1nis =0, that is the subscribers lines are directly connected; in the 1000-system it is=1, in the ]0000s vste1-u=2 etc. Thus the number of switches necessary per connection in the 100- systcm is= 1, in the .]000-system=2, in the 10000-svstem etc. In order, now, to overlook the total number of switches which,

in. the case of the present invention, cuts a figure, in the following the combination of a single switchboard for the different kinds of systems is given. I

in tlul00-system one switchboard contained till now: 100 connectors. In the WOO-system one switchboard contained till now: 100 selectors and t0 connectors in all 110 switches. In the 10000-system one switchlmard contained till now: 100 first select ors, 10 second selectors and 10 connectors in all 1.20 switches. These values are valid in the 1000- andt0000-systcm under the-supposition that in every calling direction ten icrcent of trunk-lines are provided. In a higher percentage of trunk-lines, however, the total number of switches increasesbut conipa-ratively little.

A well known disadvantage of the system just characterized is that in theiirst switching stage there exists a disporportionate large expeiuiiture of switches. This expenditure is much larger than is'necessary for the talking trallic. For, since for every connection there is but one switch necessary of each kind of switches (first, second etc. selector and connector), in reality all kinds of switches in the exchange ought to be of the same number. If till now, nevertheless, for the first switching stage ninety percent more switches have been used than iorthe following stages, this is simply due to the circumstance that it was not at all an" easy matter to reduce the num- 10o berof first selectors. Naturally, however, it must bcthe endeavor of technology. to do away with this inconvenience. Among the different possibilities oifering themselves for cedence that provides, for all stages of switching, the same number of-swltches. This aim at an equal reductlon of all kinds of switches I the said purpose, that one will have the pre- IO 5 (first, second etc. selectors and connectors) is attained in the present invention, bymeans 1 w .60 tors and 10 connectors in all 30 switches; in

of a combination of the so-called doubleswitoh principle with the group arrangement -of the Strowger system.

By the expression double-switch princi ple" a method of switching is characterized which presents itself as a transferring of the swering lug in the jack of the calling subscribers inc and the calling plug in the jack of the desired line (subscribers or trunk-line). The number of cords or pairs of plugs is so proportioned for every operators place that, in the time of the heaviest trailic', all desired connections can be made. Generally for 100 subscribers lines to pairs of plugs are suflicient. When this principle is transferred to automatic telephone exchanges, the pairs of plugs are replaced by pairs of switches, the movable contacts of whiclicorresponding to the plugs of a cord-are joined. When a connection is made, one switch, the so-called prcselecter, is set on the line of the calling subscriber, and the second switch belonging thereto, a normal selector or connector, is set on the line to be called. As, for every cou nection, one pair of switches is necessar y, it is suflicient, according to the experience with the doulde-cord system, to have about 10 to 15 pairs oi. switches "for 100 subscribers lines.

Now, the combination ol the doubkv-switch principle with the Strowger grouping method outlined above, is carried outin such a manner that, for every desired connection with another subscriber, the connection from the calling sul'iseril'iens line to' the next trunk-line is made with pairs of switches (preselectors and first selectors), whereas the further connections from the first to the second and to every following trunk-line as well as to the line of the desired subscriber are, as hitherto, made in the manner of the single-cord opera tion also customary in manual excl'ianges, that is by single switches, at the same time basing this method on the WGlh-li'llOVVi'l. Strowger grouping system.

The simplification resulting herel rom tor a switchboard of the improved Strowger type is outlined in Figure 1 of the annexed drawings. Accordingly, a. switchboard for 100 subscribers comprehends under consideration of ten percent of simultaneous possibilities of conrmctions: in the 100-system. 10 preselectors and 10 connectors in all switches;

in the lOOO-system, 1O preselectors, 10 selecthe WOOD-system, Fig. 1, 10 presele ctors, l0

first selectors, 1.0 second selectors and 10 con nectors in all 1-0 switches. To this are added, in every instance, calling and cut-ell re- In the The double-cord system is known lays, 1G little lamps and one sini 10 groupswitch'arranged laterally in a small box. As the last-mentioned arrangements are ir value as higl'i as about 10 switches, the saving. as compared with the above systems hithei'l o in use, amounts to:

100-system lOU--2(l ll) 7O switches per inn subscrilwrs.

'Ilogelhcr with this cmisiderable saving of apparatus, which is the same in exchanges of any size, the lollowing adyauiagcs are at hand:

1. The switchboards together with relays and grou 'i-switeh are reduced to more than one hall of their former size, and they can be packed, transported and mounted without being taken apart. The size of an exchange is thus reduced to more than one hall.

2. The survey ever the single switchboards is better, all the single kinds'of switches being represented in equally reduced mlmbers.

3. The percentage of possible comections can be increased, for all switching stages, to any desired capacity by simply adding new switches, provided the switchboards are kept a little broader from the beginning.

4. In every switchboard the whole supply of preselectors and first sehwtors is equally at the disposal oi every one ol the 100 subscribers connected thereto.

Among all the methods of switch-rellucing for automatic telephone exchanges hitherto known there is not one that combines so many advantages as the one above-montioned. in one older system, i. i., although the individual switches are simplified, their number is not reduced but even ii'icreascd, as, to the simplified individual switches ten to fifteen percent first selectors have to be added. in another system the subscribers are connected to relays for switching their lines on common first selectors but with such an accumulation of these relays combined with such a limitathm ol the possibility of getting connections that this invention seems to be of but doubtful value, in a third system. at last,the reduction ol first selectors is carried out, as in. the present in vention, by the addition of preselectors. but not in combination with the Strowger grouping method. This departure shows itself disadvantageously in the fact that the inunber of second selectors rises in an extraordinary manner with the increasing size of the exchanges, so that to a certain degree the switches saved in the first stage of switching have to be expended again in the second one.

, ftrrlmple of (himtruction of flzfl Invention.

IIO

a whereas all the former constructions are but 1 outhned.

" qboard such as is employed in connection with are saved, Whereas about 10 preselectors, 100 callin and cut-off relays and a snnple grou p- -t-ioned. The single parts are explained in j thefollowing by the aid of the drawings and with reference'to construction and effect.

:Ien't n the exelum'ge: Fig. 6 the group- 'shows the telephone in its outward appearthe receiver and an alternate current ringer,

altcr $310 turn the dial must revolve to its desired subscriber rings. .ll', alter a connection, the receiver is hanged on again, the

compared with the former construction of switci are added, so that the switchboards now take the form of the Fig. 1 already men- Their new features are minutely explained,

In the drawing is shown by Fig. 1 aswitch my invention. Figsi 2 and 3 two subscribers telephones No. 1523 and No. 1538'; Fig. 4 the calling and cut-oil relays in the exchange belonging thereto; Fig. 5 the sources of cur:

switch of the IOU-group to which the two te ephones above-mentioned belong; Fig. 7 "a preselector; Fig. 8 a first selector; Fig. 9 a second selector-and Fig. 10 a connector. t

-A. Equi nnmts.

I) Subscriber's apparatus. Fig. 2 is the wiring diagram 5 the apparatus and Fig. 3

ance. Besides a receiver, a microphone with battery, an induction (()]l, a movable arm for everytelephone is equipped with a'eallingde vice characteristic to the Strowger system and with a ringingbutton 1/. The calling device consists of a round dial 1: rotatory aroundi'ts axle, behind which is the device forsending impulses over the line. The dial is provided with 10 linger holes numlu-red l. 2, 3 9, 0. 'hen the telephone is to be used f ..-i. to call the number 1538, the receiver mustbe taken down and the dial be turned in a'dounward direction in succession from the numbers I, 5, .5) and s. and

norma' position. Every time the dial returns to norinal again, the impulse-semling device sends, in a manner to be described later on, successively l, 5, 3 and 8 im )ulsesover the (l-braiwhof the line and, following each return of the dial,-onc impulse goes to the exi change over the bbranch. 'l'hcsc impulses operate,.corresp mdingly, the switches in the exchange, and thus the connection to the desired subscriber is completed. After the last turning of. the dial the button (1' is to be pressed do v11, byvhich nuinipulation the a-hne; is grounded again and the bell of the downward moving receiver arm closes an impulse over a and b bywhich unpulse the eonnection 1s severed again 1n the exchange. 1

The apparatus is smilar to the Strowger telephone in all these details. A new feature is a condenser which, when the receiver is on its hook, is inserted between the cand b-line together with the ringer in order to block the common battery 1* (Fig. 5) which is instarted, when idle, between the aand b-line. Besides that contact a which, when the dial is turned, interrupts the connection between the aand Him, is mechanically so altered that a and b are only disconnected while the dial returns to its normal, but not, as till now, also when it is turned down.

2) Calling and cut-ofi'rela ysj As per Fig. 4,

' every subscriber has, in the exchange, a calling relay R, R and a eut-ofl' relay T each of them provided'with two contact springs. When the subscribers line is at normal, the calling relay is inserted, over the interrupting contacts of the cut-off relay and the interrupting contact e in Fig. 6, together with the battery F, between the aand bbranch of the subscribers line belonging thereto. It, therefore, a subscriber connected to a line which is at normal takes downhis receiver, the respective calling relayin the exchange is energized. The cutoil relay which is generally on the busy line 1:, rr over one' oftlle resting contacts of the calling relayyeuts'ofl', after thesetting on a subscribei"s line of one of the preselectors or selectors, the corresponding calling relay. In the drawing the two cut-oil relays 'l" and 'l are energized, as it is presumed that a connection exists between the subscribers Nos. 1,523 and 1538.

in the drawing are represented, below the calling and eut-ofl'relays, 10 main conduc tors i, 2, 3 9, 0' to which a branch'is leading from every calling relay. The connection ol 'these branches depends upon the tens of the number of the respective subscriber. 'l he branchi'rom relay lt, f. L, leads to the main conductor 2, the.corre-. 'sponding subscriber belonging to the second group of tens', whereas the branch from relay it which belongs to a subscriber of the third tens group leads to main conductor 3. ()n the left in Fig. 4 the main conductors pass through lamps, among them 1: and are then joined in one point, whence they go over li ne,6"and the relay it in Fig. 6 to the pole of the lmttery l When a calling relay, f. i. it, responds, a current flows on the stroke dotted line overt-herelay It and the lamps :11". 'l he lainps'have, as may be seen later on, the effect. ofcompensatlon resistances. Besides theyshow, at the same time, from which grou'pof tons a. call has been made.

The calling and cut-oil relays are, as per Fig. 1,, arranged in a special frame, in 10 horizontal rows of 10 pieces each, on the switchlioards below the switches. ()n the leftside of every row of relays is provided the lamp belonging thereto. a I

3) Sources of current. Fig. 5 represents the source of current in the exchange. F is the normal working battery grounded with its ole, V is a small subsidiary battery, (3

an a ternate current enerator for ringing and for the busy signa l. U is a rotatory interrupter for generating impulses from direct current.

4) Group-switch, Fig. 6. This apparatus is provided but-once for every IOU-group, i; e. foreach switchboard, and consists of four relays R, K, Z, E; one so-called tenspgler ZS and one so-called selector-finder .The apparatus are placed, as mentioned before wlth reference to the Fig. 1, in a small box protecting them when being transported and in the course of operation and making a quick replacing possible.

The group-switch has the purpose, when a calling relay responds, that is when a receiver is taken from the hook, to set on the calling subscribers line perfectly automatically and in the quickest manner possible, by the aid of the interrupter U an idle preselector, thus connecting the calling subscriber to a first selector. While the preselector remains then connected. to the calling subscriber until the receiver is hanged on the hook, the groupswitch is free again I immediately and at disposal for other calls.

In order to explain the signification of the single parts of the group-switch, the manner of operation of the preselectors is outlined in the following.

As soon as a subscriber has the intention to make a call and takes the receiver from the hook, the next idle preselector on turn in the exchange leaps out of its normal position and sets on the calling subscribers line which is connected to one of the fixed contacts of the switch, same as in the case of the Strowger switches, by a vertical and a horizontal motion of the rod. The setting on line of the preselector corresponds, as compared to manual operation, to the inserting of a free answering-plug in the jack of the calling subscrihcrs line by the operator. The perforn'iance of the operator is effected, in the present automatic system,

the group-switch? The groupswitch rcceives every callout of the respective group,

it appoints the preselector to be used, it starts the rod and limits its vertical and hori- 1 zontal motions to the necessary extent The group switch governs, so to say, the presclectors, the interrupter U and the bat tery F givingthe energy, while the calling subscriber, by simply taking off its receiver. starts the whole operation of-the presclector. This general characteristic of operation of the preselectors given, the essence of the single parts of the group-switch ought to be easily intelligible. I

Relay R is the common calling relay, which responds every time a subscribers callin relay is energized. It prepares, by the aid of the group-switcl'i, the coupling of an idle prcselector.

Relay K is the starting relay which, when being energized, makes the rod of the coupled preselector rise by closing impulses of the interrupter U. The same impulses fiow', at the same time, through the tens-finder ZS explained later on which rotates synchronous to the presclector in order to find out, by testing the single main conductors 1, 2, 3 9, 0, the calling tens-group and to reduce the impulses effective when the rod is lifted to the necessary extent.

Relay Z is the tens-relay which responds as soon as the tens-tinder ZS has found the calling tensgroup, and which then switches the impulses of the interrupter U from the lifting magnet of the prcselector to the turning magnet, so as to make the presc lector commence to rotate.

Relay E is the unitsor disconnecting rcla'y which responds in the case of a preselector arriving on the calling subscribers line, and which stops the preselector and disengages the group-switch. This relay has a low resistance for the reason which. will appear hereinafter.

The tens-finder ZS accompanies synchronously every preselector when the rod rises, in order to find out, as mentioned, the calling tens-group and to stop, at the due moment, the rising preselector. The apparatus is a rotating switch with ten fixed contacts to which the main conductors 1, 2, 3 9, mentioned before are connected successively. and over which the contact-arm tslidcs. The arm 1'- is pulled upward by a spring (not reprcscntcd in the drawings) so that, when at normal, it takes the position shown in the drawing, keeping open the short-circuit contact :1 for the common calling relay R. The nrmhi rotates when impulses pass the clcctromag net J and move to and fro the pawl engaging in the toothed wheel while, at the same tnnc, a constant current passes the solenoid J. The arm '1'. moves, with every impulse passing J, from one contact of the main conductor to the next one. As soon as the solenoid J is without current again the arm 4, under the eifect of the above-mentioncd spring, rcturns innnediatcly to its normal position.

The selcctor-fimler \VS selects an idle prcselector inv the case of a call. This apparatus is also a rotating-snitch however, with a contact-arm u always rotating in the same direction, and with so many fixed contacts arranged in a circle as may be necessary for 100 subscribers in the case of the heaviest possible trallic. As a rule, 10 to 15 contacts come in question. Thc clcctromagncl- W, whenever it has been cxcitcd, switches the arm w from one fixed contact over to the ncXl onc. To these contacts lines I, ll, III

, tor, Fig. 9 a second selector and Fig. a-

The construction of these four preselector lo I an idle preselector;

etc. areconnected, each of them leading to I another perselector. Line I, f. i, leads to the preselector. Fig. 9. When' a subscriber calls, he is connected to that preselec'tcr on the lines I, 11 etc. of which the arm 10 rests at that moment. Even during theact of setting the preselector on line the arm w rotates are employed in regular cyclic sequence.

5) Switches, The Figs. 7 to 10 represent the switches coming in operation in the course of the'connection' between the subscriber No. 1523 and 1538. Fig. 7 represents a preselector, Fig. 8shows a-first selecconnector.

switches is standard for, all other switches in similar to Fig.8, all second selectorssimilar to Fig. 9

the exchange.

Thus all preselectors are Fig. 7, all first selectors similar to and all connectors similar to Fig. 10..

The switches, the construction of which corresponds to that of the well-known Strowger switchesare all provided with a vertically and horizontally movable contact-arm with three contacts each. The latter can. be connected by the movable contact-arm to the contacts of 100 triple lines a, b, cfirmly arranged in ten rows of ten times three con tacts each. The setting on contacts of the arm is efiected step by step by means of the electromagnetsH and D. H lifts, whenever it is energized, the contact-arm from one row of contacts to the next one. D rotates the arm over the selected row of contacts. The, contact-arm is so ,"arrangedas to be lifted two steps and rotated three steps for a connection to No. 23, and lifted three steps and rotatedeight steps for a connection to No. 38.

The selectors Figs. 8 and 9 and the connec tor Fig. 10 have, as compared with the com paratively simpler preselector, Fi 7, the following common features: in the st place I a relay A andB for transferring .the impulses coming from. the subscribers telephones on -the local circuits in the switches; secondly a quadruple lever switch 0, i, 0, u for three pothat at first the so-called busy magnet S, af-- sitions' each, for varying the switch circuits during operation. The lever switches are so governed by the electromagnets S and M.

ter the first responding, allows the evers e, i, o, a wh ch are under the tension of a spring I to leap from the r normal position, as given by atstrokedline in the drawing, to the mid dle. position and thence, after the magnet has responded again, to the third full-drawn position, whereas the so-called release-magnet M, after having responded for a short moment, pulls bac the levers and disengages at the same instant the contact arm, as

indicated by Fig. 7, by stopping the blocking, 1 I i so as to allow the contact-arm to return, partially by the effect of a sprin and partially by its gravitation, in th' wellnown'mannerto its normal position.

The preselector'Fi with a coupling-relay G which is excited during the time a connection is completed-by a preselector, and which, by means of three levers g, 9 g lays on the lines 41, 42, 43 lead-. ing to the group-switch Fig. 8 the electromagnets G, D and H.

The connector Fig. 10 contains, specially,

' is specially provided the ringing and busy relay L and two each of small and large condensers p, p and q, q respectively. Finally there are to be mentioned, with reference to the switches Figs. 7

belonging thereto in its normal position, which, however, immediately turn upward as soon as the arm rises.

sponding first selector by five direct lines a", l)"; 44, 45 and 46. Of these the full-drawn lines a, b lead from the contact-arm of the preselector over thelevers e, i to the contact-arm of the firstselector. Line 45 connects relay A over the lever g and, similar, line 44 connects the relay B over the lever g to +F. Line 46 connects the releasemagnet M of the preselectorparallel to the release-magnet M of the first selector. five trunk-lines are comparatively short, the

The

'two switches in Figs. 7 and 8 and, similar, all i the other preselectors and first selectors are arranged in pairs one above the other on the switchboards.

From contact .17 of the first selector a first trunk-line a b, 0 leads to the second selector Fig. 9. In a similar manner a second trunk-line a, b, 0 leads from contact 57 to the connector Fig.10. The contacts 17 and 57 are singled out of the contact-rows represented in the drawing for the reason that it is presumed that the lines leaving the contacts 11 to 16 and 51 to 56 respectively are already blocked in other switcheswliere they are 'conn'ected in a similar manner. the further arrangement of other trunk-lines as well as of the position and the arran ement of the selectors and connectors to t e trunk-lines, the numerous Strowg'er exchanges and the descriptions existing thereof.(as l. i. in the E lektrotech- 'n/ische Zeitschrtft, Berlin 1903, page 724 to .734, Fig.57, and page 930, Fig. 40) arere- Of these and the 9? c and 9, contacts connected to the springs'f which are pressed down by the contact arm E ch preselector is connected to the corre-E ferred to in explanation, so that adetailed I explanation of this part of the Strowger syssented are at nornial.

- levers Z, Z --levers e, i *-contactzirin of the connector-desired subscribers line a, b to Fig. 3. The drawing clearly expresses, by the heavy lines, how the connections on the first of switching, that is between the calling subscribers line (1 b and the lirst tru11k-line all), are made similar as in double-cord operation by pairs of switches, whereas on the following switching stages, that is between the first trunk-line a, b and the second trunk-line (1., 1) same us between the second trunk-line (1., b and the desired subscribers line (1 b are made simi lar as in single-cord operation, that is by single switches.

I B. .Mcthod of Opcmt'irm.

Supposing that subscriber No. 1523 (Fig. 2) wishes to be connected to subscriber No. 1538 (Fig. 3). All of the apparatus repre- Thc'zu'in of thc selcc tor-finder to (Fig. 6) rests on line Il so that, itl, the next call, the prcselector shown in Fig. 7 comes to operation.

J The Setting on Line of the .lrcsclcctm in, Fig. 7.

This setting on line connncnccs inuncdiatcl and is entirely automatic from the beginning to'lhc'cnd as soon as the sub scriber (Fig. 2) he. taken the receiver from the hoolc.

in order to give u better survey, the stages of operation nrc described in the Following in five paragraphs (a. to c).

(1.) Tim Calling of the Snow/11min Fig. (ind the Bloc/clog of [its Iii/11cc", I) in flu Ear/1v (1 n gc.

When the receiver Fig. .2 is taken down,

the alternate currrnt ringer, being between (1 and I) togmhcr with LllC condenser, is switched out whercaltcr :1 calling curi'cnt begins to lion in (1 and l).

Liuecalltng/ circuit: l (Fig.5),coium'l '(Fig. 6),, line 4, culling rclny l\.,rcs1ing'conlziet t (T is not excited yet), line (1. icicphone in Fig. 2, line I), resting coiu'zlcl 1'. line 2 F. The calling relay it responds, cuts oil the relay T from by'nienns of the con tact spring 1- and connects 0 over the worlring contact 1*", line I, the disconnecting relsp' E, line 7 and sl'lbsidiory battery V to l By this circuit in the first pl see the line a, I)

of the calling subscriber is blocked for other described.

Ziocol calling circuit (strokwdottml l, llnc 3, contact 7", nunn conductor 2, lzunp (7 line ('3', common calling relay it, I b) The (cuding oft/u Prcsrlccfor.

The common culling relay ll responds and prepa-rcs, by closing the contuct r. the coupling oi the prcsclcctor in Fig. '2. The oouplingiis cllectod i. the aid ol the ncxt currcut inipulsc closcd by the interrupter if.

Prcpor(ltor i/ (UH/Ili/(f/ circuit: +1, coupling relay (r (Fig. 7), lower contact ol spring f (the :ovitch-rod is still :lt nornnil), linc l, ttl'lll o'lsolcctordiiulcr u' (Fig. (i), closcd coutzict and /r (Fig. 6), interrupter l l Coupling relay (1 rcsponds and nltrncls the three :u'nniturc lcvcrs y, 5 g. 1 the rclziy (l is connected to line ll, uud thus the coupling and locking currcnl mcntioncd horcnllcr is prcpurcd; by 5 the lilting lungnct ll is conncclcd to line 42 and, in n siinilzu innnncr, l; g thc turning uniguct l) is connected lo line 43. ll and l). hon'iwcrfrcccivc no (lll'l'llll us \'cl. .\l lcr rclny (i has respondcd and us soon us the current is inlcr (ihl/il'lllj/ um/ {Tor/king g'ii'cur'l. l rcluy (l (l ig. 7}, lci'cr 5/, linc l l, solenoid J (Fig. ti), cmnluou coupling relay Ii, resting coulucl c, l 'lhis c'urrcul ltccps (1, us prcpurcd bcl'orc, excited, \vhilc -l uud h are also cx cited and, together will: (i, :u'c lwpl so until thc prcselcclor is dcliuitclr scl on liuc. .Xt the sznnc lilnc lhc common willing rclu)" ll closcs, lll(llpllul(!lll oi the coupling cur rout, n circuil through norkiug iuugucl ol lhc selector-lindcr, so lhul nrur (1 moves on already in the next pousc mode by the current in tho i11i'crrLu. lcr lroin linc l lo lino ii and thus prepares the plcsclcclor councclcd thciclo l'or lhc ucxl cull.

lower contact ol spriugf" ol ull prcsclcclors in uorunil position, linc l--ll, working niugucl W and thence logclhcr with the pro;n'irotorv coupling currcnt to contact r and fit", interrupter t h.

, ruptcd :tt l the coupling and locking curl rent mentioned bclorc is brought about.

IlO

:' 5 and 5 position.

' c) The Setting of the Preselector in the Vertical Direction. 1

After relay K'has responded the inter- 5 rupter U sends current impulses through the lifting magnet H and the working magnet J.

Working impulses over H ar'zdJ: F, lever g'-, lifting magnet H, line 42, working magnet J, contact k and z, interrupter U, F. The

:6 current impulses lii t the rod of the preselector eo selectorand the tens-fin or can be followed up, the following,'by-operations are also to be taken into'consideration. The common relay K interrupts, when being at work, at It,

the way of thepre'paratory coupling circuit.

:5 This way isinterruptedagain, later on, at r,

the relay B being cutout at 'v by a short circuit after the first working of J. By this opening of the contacts at k and r it is effected that, at every call, only one preselec- ;o tor'operates; and that other preselectors can in no way be influenced before the tens-finder has returned to its normal position. \Vith the first impulse through the lifting magnet H the springs f and f move inan upward In consequenceof the opening of the lower contact of f being eillected at this moment, relay .l is cut oil from line I, so that the preselector of Fig. 7, until it returns to normal position, cannot he coupled again.

vo By the closing of the upper contact off line I is connected to' the interrupter U which causes the arm iv of the selector-finder, whenever it touches line I again before the releasing of the preselector, not to remain on.

next line H by the interrupter U. If the preselector of this line is also busy, arm 10 moves on again until it finds the line to a reselector that is not busy. In order not to et the arm o w turn without necessity when all of the pre selectors are busy the working ina'gnet W is not fed immediatelyby +F, but over a line which has connection to F'over the preselector contacts arrangedin parallel onlyso long, asat least one preselector is-at normal. The current impulses, of the interrupt'enU through the lifting magnet H and the working magnet'J have continued meanwhile. Thus the second impulse has set the contact- 0 arm ofthe preselector in height of the contact row containing the su'nscrilrers lines 21, 2'3 and, simultaneously, the arm i ol" the tens-finder has been placed on the main conductor 2which, as will he remembered, is 5 connected to +F since the call of ,the sub- 5 this line but to immediately be turned on the .and immediately energized by the prese-' are connected,

scriber No. 1523 over the working contact 1'? and the line 3.

d) -The Setting of the Preselector in the Hora} zontal Direction; p.

When the arm i touches the mainconductor 2, the tens-relay Z is energized. 7,

Circuit over the tens-relay Z: +F, line 3, I

working contact rains-in conductor 2, arm i,

relay Z, -F. The tens-relay Z, by turning over the contact spring z, cuts. the lifting magnet H andthe working magnet J out of, the interrupter circuit and inserts the turning magnet'therein instead. .8

.Working impulses over I): +F, lever 9 turning magnet D, line 43, working contact 2. interrupter U, F. the contact arm of the prselector until, when D is energized the third time, it. reaches the gpnt acts 23 of the calling subscribers line it,

The impulsesrotate U e) The Disco nncction c the Pres elector and the Disengaging of t .e Group-Switch.

arrives on line (1, b, c, the units or' discon-f" nectingrelay E (Fig. 5)' responds.

'(Jirr uit over the units or disconnecting relay '1']: V. line 7 relay E, line 1, working 9 contact 1*, line 0, contact-arm of the preselectol', V By opening the contact ate, the coupling and locking current is interrupted so as to make G, J and K simultaneously currentless. in Fig. 7' is cut off from the common lines 41,

42 and 43, while J" causes the'arm i of the tens-finder to return to its normal position".

By opening the contact at e the line calling made current-less. The resting contact then? closingat r, relay T is connected-to line 0 lector. I

Ont-ofl current over T.: -F, contact-arm' When the contact-arm of the preselector f1 By G the "preselector 1C3;

circuit is interrupted,-and thus relay R is 95 of the nreselect'or, line 0', restin contact r w relay T, line 5" and 3, +F. y the fact that T is excitecL-the calling relay R is out 1 off from line a, h as long as the subscribers thus preventingbesi des other effects-that the calling of the sub scriber No. 1523 does not further affect the group-switch, which would cause other pre. v,

selectors to commence operatzon. lndependi ently of the excitation of Tgtthe connection of line 0 to F, or ground, in the preselector has'the further effect that the .subs'tiibers line a, b continues tobe blocked after the blockingof 0 over working contactr'-,line 1,' relay E, line 7 battery V, Fwhich has" been inieilecttill now-has been stopped. While the preselectol in Fig. 7 remains set, the common apparatus has returned to'its normal position in ;which it is ready to .re'-. 13o

ceive a new call.

2) The Setting on Lines qftlte First'aml Secoml Selector (Figs. 8 and 9 and 0f the Connector (Fig.

The preselector being set on line as per 5 Fig. 7, the calling subscriber is connected to +F over line a, b--contact-arm oi the pre' select0r-line a, b"lever 0 i (stroked first position)relay A, B -line 45, 44-- resting contacts g", 9 Thus the same condition is brought about as in the case of the Strowger system in its usual form. only existing difference is in the fact thatbetween the calling subscriber and the first selector-there is not a lasting but only aingly.

a) .Tlre Sett'lng on Line of the First Selector,

. Fig.

This setting on line follows the first turn ing of the dial of the subscribers telephone No. 1523 fronrfinger hole 1, the impulse sending device in the subscribers apparatus grounding once line a and, thereafter, also grounding once line b. Correspondingly, each of the relays A and B are also ener- 0 gized once.

Impulse over relay A F, resting contact 9 (Fig. 7), line 45, relay A lever 6 line a", contact-arm of the preselector, subscribers line a, impulse sender in the subscribers apparatus, ground, and back to -F.

Impulse over relay B +F, lever o line 44 rela B lever L line 7) contact-arm of.

I 7 l I the preselector, subscribers line b, impulse sender, ground, and back to F.

Relay A transfers the impulse received to the lifting magnet H lever a closing a circuit +F, a 8, H ,F. ll responds and lifts the contact-arm one stop in front of the contacts of lines 11;, 1 2, 13

Relay B transfers the impulse received to the busy magnet S lever closing a circuit over +F, S b ,.-F. Magnet S attracts the lever s and the busy escapement. The lat ter, when S is made currentless, allows the levers 2 i 0,-u to go over from the stroked position 5 to the middle position. At the same time u inserts the turning magnet D in the interrupter circuit +F, u D, U, F.

The contact-arm rotates under the efl'ect of the impulses which the electromagnet D Th e receives from U. The lines connected to. the contacts 11, 2 16-as has been prosun1ed-being busy, the contact-arm turns in the well-known manner until it reaches the contact 1? oi the line (1, I), c, at the same time completing, by cutting oli' the relays A, B as shown in the drawing, a direct connoction from the calling subscribcn' to the second selector.

l) T he Setting on Line oftlic Second Selector, Fig. .9.

Then follows the second turning of the dial oi the sub cribers apparatus No. 1523 from finger hole a, the impulse sender of the telephone grounding c five times and, following this, grounding I) once. Thus relay A is grounded five times and relay B once.

impulses over relay A F, relay A, lever (stroked position), line a, contact-arm ol' the first selector, lever (2, line a, contactarm of the preselector, subscribers line a, impulse sender, ground, and back to F.

Impulse over 13*: +F, B lever 1", line b, contactarm oi the first selector, lever i line b", contact-arm of the preselector, subscribers line I), impulse sender, ground, and back to F. Relay A trausfers'the live impulses to the lifting magnet H and B transfers its impulse to the busy magnet S The impulses flow on in a similar Way as in the first selector (Fig. 8) the wiring of which is identical to that of Fig. 9 with the exception of the contact f K The lifting n'lagnet H by being energized five times, lifts the contact-arm to the height of the contacts of the lines 51, 52,

'53 3* being excited, the contact-arm then slides over the lines 51 to 56 presumed to be busy to the contact 57 of the line of, b, 0. Then the calling subscriber is con-- nected to the connector of Fig. 10.

c) The SIZllll'If/OHLl'ltcqfllt Connector, Fir .10.

This is attained by the third aiul iourth turningof the dial from 3 and 8. Corrcspond ingly relay A" is energized three times by the first and eight times by the. second turning of the dial, and, following each turning, relay B is energized once.

form/lacs orcr relay A: l, A, line a", contact-arm oi the second selector, lover 1:, line a, contact-arm ol' the first selector, lover line (1", contact-arm of tho prcsolector, sul.)scribei"s line a, impulse sender, ground, and back to l.

Impulse over relay 1) +l, .B, line b", contact-arm ol' the second selector, lever if, line t contact-arm oi' the first selector, lever 'i, line b, contact-arm of the preseleotor, subscribers line I), impulse sender, ground, and back to F.

The first three impulses over relay A are transferred to tholii'ting magnet 'H, the contact-arm being lifted up to the contact-row 3]., 32 shown in the drawing. Relay B being excited once hereafter, this causes also the busy magnet S to beenergized, so as to make the levers e, i 0 m go over from the stroked to the middle position, lever u inserting the turning magnet D inplace of the lifting magnet H", The following eight impulses over relay A are transferred to the turning magnet D the contact-arm being rotated as far as the contacts38 of the line a, b, c5. The relay B, being excited once hereafter, attracts its armature and thereby includes the busy magnet S in a ciscuit F,'S", b F, whereupon the said busy.

named over S is interrupted by a the quadgrounding line a and bsimultaneously. The relays A and B Fig. 10 are tlien*as de-- ruple lever switch is brought into the osi -:tion shown in full lines and at 0 cc the rlnger relay L is energized by a current over the circuit F, L, 16 a, F. If the desired line is already busy, that is to say, if c is connected in another connector or preselector to F, a circuit is closed over L while the levers 0 i 0 and a are in their middle positions, which closes the contact at lever Z3, and

thereby prevents the calling subscriber from interruptin the current o'ver S thus making itimpossible for such calling subscriber to cause the levers to pass to the extreme position shown in full lines in the drawing.

When the ringing relay responds, it connects line a, I) over the levers 0 i and Z Z to the alternate current generator 0, Fig. 5. Thus alternate current is made to flow to the desired subscribers telephone No. 1538, so that the bell rings as long and as often as the calling subscriber presses his button d. When the leverse, i 0 u turnover to the third position, line 0 is connected to F or ground over the contact-arm and lever 0 and thus line a, l) is blocked for other subscribers. Atthe sain'e time a constant v current F, lever 0 contact-arm of the connector, line 0, resting contact of the relay It, cut-off relay T, lines 5 and 3, +F

commences to flow which energizes the cutoff relay'T and thus cuts the calling relay R out of the line, a, b which prevents, when the called subscriber No. 1538-takes off his receiver, that a preselector is made to operate.

' 3 it. Releasing of the Switches. This is effected every time the calling su bseribor hangs on his receiver, the downwardmoving receiver arm of the telephone shortly scribed previously-energized simultaneously and an impulse +F, M lever b and a, F is closed, causing the releasing magnet M to respond; The electromagnet.M transfers the impulse, by closing the contact at m to the releasing magnets M Fig. 9, M, Fig. 8 and M, Fig. 7 of the other switches, so as to energize, simultaneously, the releasing magnets of all four switches. Then each of the magnets causes the corresponding contactarm and the quadruple lever-switch to retdrn, in the well-known manner, to their normal positions, the blocking of all the lines a,

ba,.ba", ba,, I) being suisipendedsimultaneously, and also the cut-0 relays T" and T ceasing to be energized.

0. Closing Remarks.

The described types, of apparatusand the Wiring diagrams serve particularly as is expressly mentioned here-but for an ex lanation of the invention. Specially in p ace'of the wed-known Strowger switches with con tact-arms movable in the vertical as well as in the horizontal direction, any other auto-.

matic switching telephone system can be taken as equivalent. Also the described method of the setting on line of the preselec tors combined with the arrangement of a group-switch is, although a new feature and an essential improvement as compared to the methods hitherto known with reference to simplicity and rapidity of operation but to be regarded as a special solution of the problem treated by the invention.

To illustrate the rapidity of operation of I tens-finder and alsothe arm of the preselector start as hereinbefore described for a single call, but always stop at the first live contact which they reach. In consequence of this, the calling line having the lowest number is given the first choice of a preselector and then follow the others one after another.

Owing to the rapidity of operation, it will rarely happen thatcalls occur at the same time in a group and even when this does occur, there is no delay worthy of notice.

The fundamental and characteristic feature of the invention consists in the combination of the double cord principle with the welt-known Strowger group arrangement by whrch is attained, as will be clear from Fig. 1 of the drawings, and according to the demands of tho tra'llic, a uniform equipment of all kinds of switches, such as preselectors,

v switches rst 'andi, second selectors,- arid connectors T which by any other system.-

.Bythis invention, the total number-of is reducedto a minimum never obtained heretofore, without the necessity of employing any further means except a-call- 1 in and cut-off relay for each subscriber and cup switch.

r hus fully described my invention,

'wha't- I ela'im is:

' i' 1. In anautomatic telephone system, the

, a; simple combination, with thev subscribers lines dil I vided ingroups, of a plurality ofpreselectors i '15 .anclfirstselectors for. t-ach line group, each preselector com rising line contacts con- Iiected to the sulgscribers lines of the group,

.a vtraveling contactdevice and means for moving tsald contactdevice to cause it to 2o make contact first selector Comprising line contacts, a traveling contact device in electrical communication with the traveling contact device of ohe of the preselectors, and means for moving this traveling contact to its line contiicts, trunk lines connected in multiple to the line contacts of the first selectors, an auxiliary switch common to a plurality of preselectors, coupled for a call with one of said preselectors and working simultaneously with the same, and means connected with the trunk lines and arranged, to make the final connection over'the selected trunk line to the desired subscriber.

2. combination, with the su scribers lines divided in groups, of a plurality of preselectors for each line group, each comprising line contacts connected in multi 49 sp'ective subscribers lines o' the group, a

traveling contact device and means for mov-.

' ing said contact device to cause it to make contact with the line contacts, a plurality of first selectors for each line grou each having 5 line contacts, trunk lines divi ed in sets and connected in multiple to the line contacts of the first selectors, a traveling contact device 7 for each first selector, the traveling contact device of each first selector being in electrical 5c communication w i-th'the traveling contact device of one of the preselectors, an auxiliary switch common to a plurality of preselectors,

coupled for a call withone of said preselecs tors and working simultaneously with the same,'means for moving thetraveling contact device'of eac first selector'into engagement with the contacts of an unoccupied trunk line of the desired set, and lneans connected with the contacts of the first selectors "6c and arranged to ake the finalconnect'ions l to'the desired subscriber. y 3. In an automatic tele ho system, the combination, with the su scriifers lines di- -vided in groups, and for each line group a plurality of pairs of switches, each pair comresult has not'been obtained hitherto.

with-the line contacts, each In an automatic telephone system, the

le to the re prising a preselector and a first selector, each preselec or and first selector comprising line contacts, a traveling contact device coacting with the individual line contacts and means for moving the traveling contact device, the traveling contact device of each preselector being in electrical communication with the traveling contact device of its companion first-selector, an auxiliary switch common to a plurality of preselectors,. coupled for a call with one of said preselcctors and working simultaneously with the same, the line contacts of the preselectors being connectml to the respective subscril'uers lines of the group, of trunk lines divided in sets and connected in multiple to the line contacts of the first selectors, and means arranged to make the final connection to the desired subscriber.

4. In an automatic tele hone system, the 8 combination, with the su scribcrs lines divided in groups, of a plurality of pairs of switches for each line group, each pair comrising a preselector and a corresponding first selector, each preselector and first selector comprising line contacts, a traveling con- I tact device and means for moving the traveling contact device into el'igagemcnt with the single line contacts, the traveling contact device of each preselector being in electrical communication with that of its companion first selector, the line contacts of the preselectors being connected to the corresponding subscribers lines, trunk lines connected to the line contacts of thefirst selectors, an [O0 auxiliary switch common to a plurality. of

preselectors, coupled for a call with one of said preselectors and working simultaneously with the same, a calling relay foreach sub-1 scriber arranged to set in action said auxiliary x05 switch and the means. for moving the traveling contact device of an idle preselector, and means actuated at the calling station for operating the traveling contact device of the corres onding first selector.

5. nan automatic tele )hone system, the combination, with the subscribers lines divided in groups, a luralit of preselectors and first selectors or eac line group arranged in pairs, each preselector and first se 1 I 5 ctor comprising line contacts, a traveling contact device and means for moving its traveling contact device, the traveling contact,de cc of each preselector being in electrical-communication with thatof its corre- 12o sponding first selector, the subscribers lines of the roup bein connected to the line contacts'oi the preseliectors, trunk lines connected to the line contacts of the first selectors, an auxiliary switch common to a plurality of I 2 5 preselectors, coupled for a call with one of said preselectors and working simultaneously with the same, a calling relay forjeach subscribers line arranged to set in action said auxiliary switch and anidle preselector 1 c upon a call, means at the-subscribers sta "lDlODS- to actuate automatically the corre* iswi'tches for each linegroup, each'pair comprising a preselector and correspondin first selector, each preselector and first se ector siponding-callirig relay when the receiver is taker-1:11p, and means at the subscribers staselector and for making the final connection tionsflfor'operating and controlling the first over the selected trunk line. 6. In an. automatic tele hone system, the

, combination, with, the su scribers lines divided' in groups, of a plurality of pairs of.

comprisi line contacts, a traveling contact device an means for moving the traveling contact device into engagement with the single line contacts, the traveling contact de- ,vice ofeach preselector being in electrical lector being communication with that of its companion first sel.ector, the line contacts of the preseconnected to the corresponding subscribers lines, trunk lines connected to the line contacts of the first selectors, an auxiliaryswitch common to a plurality of preselectors, coupled for a call with one of said preselectors and Working simultaneously with the same, a calling relay for each subscriber arranged to set in action said auxiliary switch and the means for moving the traveling contact device of an idle preselector, and to stop the said preselector upon the arrival of its traveling contact device at the contacts of the calling subscribers line,

and means'at the calling station for controlling the traveling contact device of the corresponding first selector.

7. In an automatic tele honesystem, the

-- combination, with the su scribers lines divided in groups, of a plurality of pairs of switches for each line group each pair comprising a preselector and a: corresponding first selector, each preselector' and first sev with the single linecontacts, the'traveling lector comprising line contacts, a traveling contact device and means for moving the traveling contact device" into engagement contact device'of each preselector being in electrical communication. with that of its companion first selector, the line contacts of the preselectors beingconnectcd to the corresponding subscribers lines, trunk lines connected to the line contactsof the first selectors, an auxiliary switch common'to a tion for operating the traveling contact device of the corresporlding first selector.

8. In an automatic telephone system, the

scriber arranged to set in action themeans in (pairs, each pair comprising a preselector combination, with the subscribers lines divided in groups, of a plurality of switches for each line group, said switches being arranged in (pairs, each pair comprising a preselector an a first selector, each preselector and its first selector comprising line contacts, a travauxiliary switch common to a plurality of preselectors, coupled for a ,call with one of said preselectors and working simultaneously with the same, a calling relay for each sub- 5 for moving the traveling contact device of a preselector, a cut-off relay for each subscriber arranged to cut out the calling subscribers calling relaywhen the preselector is, set on the calling line, means at the calling station for controlling the traveling contact device of the first selector, and means operated over the selected trunk line for making the final connection to the desired subscriber.

9. In an automatic tele hone system, the

combination, with the su scribers lines divided'in groups, of a plurality of switches for each line group, said switches being arranged a corresponding first selector, each reselector and its first selector comprising ine contacts, a traveling contact device arranged to engage said line contacts, the traveling contact device of ea'c'hpreselector being in electrical communication with that of the corresponding first selector, the line contactsof each preselector being connected to the corresponding subscribers lines, trunk lines connected to the line contacts of the first selectors, an auxiliary switch common to a plurality of preselectors, coupled for a call with one of said prcselectors and working simultaneously with the same, means for moving said traveling contact devices, a calling relay 1 r 5 for each subscriber.arranged to set in action said auxiliary switch anti the means for moving the traveling conta t device of a preselector, a cut-off relay for each subscriber arranged to out out the called subscribers calleach comprising line contacts,

and a first selector, each preselector and its first selector comprising hne contacts, a traveling contact device of each preselector being in electrical communication with that of the corresponding with one of said preselectors and working simultaneously with the same, and a pair of relays for each subscribers line, each pair comprising a calling and a cut-off relay, the calling relay being arranged to set in action said auxiliary switch and an idle preselector upon a call, the cutoff relay being arranged to cut out its calling relay when th6.C01I6- spending subscribers line is occupied.

11. In an automatic telephone system, the combination, with the subscribers lines, divided in groups, of a plurality of preselectors and first selectors for each line group, each comprising line contacts, a traveling contact device arranged to engage its line contacts, and means for moving the traveling contact device, the traveling contact device of each preselector being in electrical communication with that of one of the first selectors, the contacts of the preselectors being connected to the corresponding subscribers lines, trunk lines connected in multiple to the first selectors, an auxiliary switchcommon to a plurality of preselectors, coupled for a call with one of said preselectors, and arranged to control its travelingcontact device to bring the same as needed in engagement with the contacts of a calling line, means actuated at the calling station for moving the traveling contact device of the first selector and for making the final connection over the selected trunk line to the desired subscriber.

12. In an automatic telephone system, the combination, with the subscribers lines divided in groups, tors and first selectors for each line group; i a traveling contact device arranged to engage its line contacts, and means for moving the traveling contact device, the traveling contact device of each preselector being in electrical communication with that of one of the first selectors, the contacts of the preselectors being connected to the corresponding subscribers lines, trunk lines connected in mul tiple to the first selectors, an auxiliar switch common toa plurality of preselect: rs, coupled for a call with one of said preselectors andarranged to drive its travehn contact device to. the. contacts of the cal ing subs'cribers line, a coupling device for each pre selector to bring its means for moving the traveling contact device in communication with said 'uxiliary switch ready for a call,

the first selectors,

of a plurality of preselec with an idle device arranged to engage its line contacts,

and means for moving the traveling contact device, the traveling contact device of each preselector being in electrical communication with that of one of the first selectors, the contacts of the preselectors being connected to the corresponding subscribers lines, trunk lines connected in multiple to an auxiliary switch com mon' to a plurality of preselectors, coupled 'for a call with one of said preselectors and arranged to drive its traveling contact device to the contacts of the calling subscribers line, a prcselector finder controlled by the preselectors and arranged to couple an idle preselector for the next call with said auxiliary switch, means actuated at the calling station for moving the traveling contactdevice of the first selector, and means operated over said trunk lines for making the final connection between subscribers lines.

14. In an automatic telephone system, the combination, with the subscribers lines divided in groups and in sub-grou s, and, for each line group local circuits equa in number to the number of the sub-groups; for each line group a plurality of preselectors, each comprising subscribers line contacts arranged in series corresponding to the sub-groups, a

traveling contact device and means for moving the traveling contact device to the series of contacts and along these, a calling relay in each subscribcrs line arranged to set in acreselector upon a call and to tion an idle alter the con ition of the ocal circuit of the.

sub-group to which its line belongs; for each line group a common auxiliarv switch coupled Iln'eselector ready for a call and working sync ironously with the preselector and. arranged to stop the traveling contact device of the preselector'at the series of contacts of the calling subscribers subroup and for causing said traveling contact evice to come over the contacts of the calling subscribers line.

15. In an automatic telephone system, the combination, withsubscribers lines divided in groups and sub-groups, and, for each line group, ocal circuits equal in number to the sub-groups; for each line group a plurality of pieselectors, each comprising subscribers line contacts arranged in rows corresponding to the sub-groups, a traveling contact device and means for moving said traveling contact device to a desired row and along such

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