US1109216A - Automatic telephone-exchange system. - Google Patents

Description

APPLIOAHON FILED DEC 11, 1909.

Patentd Sept. 1,1914.

6 SHEETSSHEET 1.

INNmIIIII G. GRABE.

AUTOMATIC TELEPHONBEXGHANGE SYSTEM.

APPLICATION FILED DEQ.11, 1909. 1,109,216. Patented Sept. 1, 1914.

6 SHEETS SHEET 2.

e. GRABB.

Patented Sept. 1, 19145 e SHEETS-SHEET 3.

lllalllllllvllllllllllllllll.l-lllllllulllllllullulilnlll' 6 SHEETS-SHEET 4.

Patented Sept. 1, 1914.

G GRABB AUTOMATIC TELEPHONE EXCHANGE SYSTEM. LPYIJGLTIO] TILED D30. 11, 1909. 1 1 09,2 1 6 G. GRABB. AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

Patented Sept. 1,191i

APPLIOATIOH FILED DEC. 11, 1909.

W, Q 1 MP.

"aims Fuzns m L'wc WAsmMY -tx n c G. GRABB; AUTOMATIC TELEPHONE EXCHANGE sys'rw APPLICATION HLBD DEGJI, 1909.

- Enented Sept. 1,1914.

8 SHEETSSHEET 6.

UNITED STATES PATENT OFFICE.

enone GRABE, or NIKOLASSEEJNEARB'ERLIN, GER-MANY, lassionon; TO SIEMENS at HALSKE a G., or BERLIN, GERMANY.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of, Letters Patent.

Patented Sept. 1, 1914.

Application filedDecember 11, 1909. Serial No. 532,711.

To all whom it may concern Be it known that I, Gnonc GRABE, subject of the German Emperor, residing at Nikolassee, near Berlin, Germany, have invented 5 certain new and useful Improvements in Automatic Telephone-Exchange Systems, 'of i which the following is a specification.

My invention relates to an automatic telephone-xchange system, in which the subjscribers are connected byway of first and second, and so on, selectors and connectors which are located in a central station or exchange office and are set; by means of impulses of current sent over the branches of the line leading from the subscribers station to the ofiice by operating a number'ed dial at the subscribers station.

' My invention relates particularly to that type of automatic telephone-exchange sys tems, in which onlya limited number of selectors and connectors are provided in the exchange oflice, the subscribers are divided into groups, and a calling subscribers line is-connected with an idle so-called first a selector by means of call-seekers which are started, when a call is present in the group of subscribers to which the switching device in question belongs, move step by step I and test. the contacts of the lines of their groups of subscribers, andare Stopped at the contacts of thecalling line. The callseeker must seek a calling line in this manner during the time which elapses between the-approach of the subscriber to his station and lifting the receiver until the first selecting impulse of current is emitted, since otherwise wrong connections would occur. As this. interval is only short, however, after moving only a limited number of steps the call-seeker must beable to reach the calling line and my invention comprehends a callseeker system which enables this in the case ofa large number of groups of subscribers.

The construction, connection and mode bf operation of theselectorsand connectors is secondary for the-essence of my invention, as my invention is equally suitable for all systems.

A primary object of my invention is to provide anarrangement' by which the idle call-seekers of a group of subscribers, which call-seekers execute, -when being'set, two

kinds of switchingsteps or movements, 6. g.

lifting and turning or large and small steps,

are automatically set ready for receiving a call by preparatory steps of the former kind to sub-groups of the line contacts, and in which arrangement, when a call is present in a sub-group, the contacts of the calling line are reached by the call-seeker set to the sub-group in question by means of a less number of steps of thesecond kind, while another idle call-seeker is automatically set to this sub-group for receiving further calls in this.

A further object of my inventionv is to provide a system in whiclnwhen only one call is present in a Sub-group, only one callseeker is moved along the contacts of the same, whereas when two or more calls are present simultaneously in the same subgroup, two or more call-seekers are started in succession for receiving the calls and are moved simultaneously along the contacts of this sub-group.

Another object'of my invention is to cause that at each sub-group only one call-seeker be set ready for receiving a call, whereas the remaining' idle call-seekers of the group are in an initial position in the reserve condition and operate in succession when a callseeker set to a sub-group is occupied receiv ing a call, the call-seeker which becomes idle after the termination of a telephonic connec tion being returned into its initial position and joining the reserve seekers, and so many call-seekers beingprovided for each group of subscribers that even during the heaviest load each sub-group has ready another callseeker for receiving calls. V Another object of my invention is to pro vide a constructional form in which each call-seeker simultaneously tests two or more rows of line contacts, but only makes a connection with those contacts which appertain to the calling line.

When carrying my invention into practice, besides the caileseekers I preferably provide additional automatic switches which,. when a call-seeker starts moving along the contacts of the subscribers lines, start simultaneously with the call-seeker and are moved until the latter is connected with an idle first selector, independently as to Whether the call-seeker is still in motion or whether it has already found the calling line. My invention will now be described more particularly with reference to' the accom-.

panying drawings.

'Fig. 4 the connection of a connector 3 9 scribers In said drawingsz- Figure 1 shows the connection for connecting the subscribers stations with the calling devices of the exchange station, Fig.- 1 is a detail view of the relay TB in larger scale. Fig. 2 the connection of the call-seekers of a group of subscribers lines for seeking a calling line, Fig. 3 the connection of a first selectorzi,

an Figs. 5, 6 and 7 show modifications 0 connections for connecting the call-seekers with the first selectors by way of automatic intermitte'nt switches, to wit Figs. 5 and 6 show theconnection of the first selector common to a number of subscribers groups by way of second call-seekers appertaining to these with the call-seekers of the group of subscribers, whereas Fig. 7 shows the connection of the call-seekers by way of preliminary selectors appertaining to these with a plurality of first selectors commonto subscribers groups. The parts of Figs. 2 and 3 in dotted lines show the supplementary means necessitated hereby at the call-seekers of the subscribers groups, and at the first selectors, respectively. The exchange oflice or central station is supposed to have a capacity for 1000 subscribers, so that the representation of second'selectors is not necessary.

In the drawings, like reference characters designate like parts.

Reference characters comprisin' letters haye indices which are omitted in t e specification when one definite apparatus or part provided with like letters is not to be denoted. f

Referring to the drawings, in Fig. 2 four call-seekers AS, A8 A8 AS of one of subscribers containing the sublines 300-399 are represented. The call-seekers are provided with test switch-levers 0 0* and line switch-levers 0 '0 0, 0 whichare attached to the switch shaft of the call-seeker and, e. can be passed by means of two motions at right angles to one another, such as lifting and turning, over the test and line contacts of a group of 100 subscribers, sliding simultaneously over two rows of test contacts and two rows of line contacts. The ten horizontal rows of line and test contacts are divided into five sub-groups, so that each .two rows form a sub-group. In connection with the call-seekers are switches SS whose switch springs or levers s s 8 are moved in the one direction'simultaneously with the movement of the switch-levers 0, whereas they.

remain stationary when the switch-levers 0 move in the other direction. By means of the switches SS SS the sub-groups are tested automatically and continuously and call-seekers for accepting or receiving the calls in these are placed ready. One idle call-seeker is set by means of preparatory steps on each sub-group, whereas the remaining idle call-seekers of the group remain in the initial position in the reserve condition. The switch spring 8 of a callseeker serves for engaging that sub-group to which the call-seeker is set; it slides over fixed contacts it, h, Z2, is, 7: is, which are connected in order with the test line 10 of the initial position. or the test- lines 11, 12, 13, 14, 15 of the sub-groups. The switch spring 8 serves for testing the sub-groups and slides over the contacts is, 76 ,10 is", which are connected in the corresponding order with the test lines 12, 13, 14, 15 of the sub-groups, and

the ground line 16, and by way of the initial contact 70, which is connected by way of contact 71, of the switch shaft of the callseeker with the test line 10, when the seeker 1n questionhas moved out ofits initial position.. Contact is at-switch SS of the 'first call-seeker. A8 is connecte in addition,

d 4 with the test line 11 of the first sub-group formed here by the two top rows of contacts and in this manner is connected through to contact 10 of that call-seeker which is 10- cated in the initial condition as the first in the row in the group of subscribers in question. Switch spring 8 serves for receiving a call in the sub-group and slides over contacts is, k, 70 7e 5, 10 connected respectively in the order stated with the lines 21, 22, 23, 24, 25 leading to the call devices of the sub-groups. Of these lines only' line 24 connected with contact 70 and line 25 connected with contact 70 are-represented in the drawings. The switch spring 8 of each call-seeker is connected with a hi h resistance relay A which connects in circuit the lifting electromagnet H of the seeker when the sub-group, on which the switch spring 8 tests, becomes free and relay A is not.en-'

ergized. Switch spring .9 'ofeach callseeker is. connectd with a relay B which connects in-circuit the turning electromagnet D for the switch shaft of the seeker as soon as its circuit by way of thecalling line of the sub-group in question isclosed.

The switch sprin s of each call-seeker keeps the test line 0 the sub-group in question f engaged as long as there .is no call in this sub-group and the rest contact 6 of the relay B of this call-seeker is closed. As shown in Fig. 2, the call-seeker A8 is moved up to the top, 2'. e. fifth, sub-group, its spring a resting on'the grounded contact 70 The-high resistance electro-magnet A connected by the conductor 26 with the common battery feeder 100 is continuously energized by way of conductor 27, spring a,

contact k and the grounded line 16 and conductor 30 and contact 6 of relay B keeps thetest wire 15 of the top sub'group engaged so that no additional seeker can.

tery feeder 100 (Fig-2), conductor 28, coil 10 of relay A conductor 29, spring 8, contacts k*-- of the switch S5, test line 15, to contact i and spring 8 of switch SS condoctor 30, contact 6 to ground. and to the grounded pole of battery-G. The contin-.. ,16 u'ously energized relay- A kee 's' the'circuit of the liitingelectroniagnet I 8 of the call-V seeker AS at the opened back rest contact and prevents this seeker moving forward to the fifth sub-group. In like manner switch 0 spring 8 0i switch Siif keeps the test line 14 grounded by way of conductor 31 and con-- tact b of relay B andprevents a second all seeker moving forward to the fourth sulr cup. In similar manner .each idle 25 calLseeker keeps engaged the third, secand and first sub-groups. All the remaining idle call-seekers of the group are in. the initial positi n- In the drawing the call-seek 'ers AS and AS occupy this position. The

0 seeker (not shown) set to the first subgroup keeps the test line 11 grounded with its switch spring 8 By way of this grounded 7 connection and the connection 9 at switch S8, conductor 8, contact it, conductor 7 of the call-seeker AS test line 10, contact 70 and spring s of switch SS conductor 32, relay A of the first call seeker A8 in the row of reserve seekers, conductors 33 and 100 there flows from battery G a current which keeps relay A energized and prevents this call-seeker movin forward. Also, the grounded springs o call-seeker AS keeps relay A of. the next reserve seeker AS energized by way of contact 70 of switch SS conductors 10, 6,,conta'ct it of seeker AS conductor 5, contact 70 andspring .9 of switch SSflconductor 34, coil;

of relay A, conductors 35 and 100, and so -on. Now when a call is present in a subgroup and relay B of the call-seeker set to this sub-group is energized, as described hereinafter, by interrupting contact 6 the grounding of'the switch spring 8 in question is done away with, and relay A testing on this sub-group and appertaining to the call-seeker next in order of the next subgroup is made eurrentless, whereby the lifting electromagnet of: this call-seeker is con nected in circuit and the seeker lifted and placed reaclyfor receiving a further call in the sub-group in which the call took place.

The lifted call-seeker releases the test line of the sub-group to which it was previously set, whereupon the call-seeker of the next 6 lower sub-group is'lifted. Thus the call,-

l seekers move up in succession until a reserve seeker is lifted from the initial position to the first sub-group. If, for example,

tery feeder 100, conductor 36, coil of electromagnet H conductor 37, rest, contact of relay A conductor 38, contact 6 of relay B, conductor 39, common circuit-breaker conductor 101 and circuit breaker U. Callseekcr A8 is lifted'unti l its spring sicontacts with contact of switch SS Relaycontact In, line 16 and ground vand discern nects the lifting electromagnet H When contact 71 to contact k the test line l5'beai comes grounded and the group obtained by ers, whereas the groundis disconnected from test line'14 so that the seeker (not shown) set to the third sub-group can move'forwardto the fourth sub-group owing to the interpolationof its lifting electromagnet. The

sub-group. Test line 11 grounded by w-a of spring 8 and contact 11 of switch S 2' is then connected by way of conductor 9 at the -first call-seeker, conductor 8 and the head contacts k h h3 of the call-seekers A8 A8 A8 with the relay A of the call-v seeker AS which is energized in this manner. 4 A

The subscribers stations are connected with the central station by way of double, lines (Fig. 1) which are combined in the central station to groups of 100, for eXam-' ple; Each line of a groupleads in multiple to. the banks of contacts of the connector and call-seeker, of its group and is connected by way of contacts :9, i of ajcut-oif relay TR to a call relay R. a Each subscribers line pos-, segses its own call relay and its own cut-oil re ay. v

The calls in the individual sub-groups are received independently one'of another and sub-groups. In order to bring when only one call is present orig subtgroup, only one call-seeker is moved along the contacts of this sub-group, and, when two or nore calls are presentthat two or more dall-seekers started in succession and moved simultaneously along the contacts of this sub-group, each sub-groupie provided with a starting relay E (Fig. 1) having two differential Relay A of the electromagnet H by way of the main batseeker AS is thus closed to other call-seekw described operation is repeated until the first reserve seeker AS is lifted to .thc first may occur simultaneously in the various about that simultaneously in the same sub-group A is then energized by. way of spring as,

spring 8 of this seeker AS -passes from coils e 6 Each cut-01f relay TB of a subscribers line is provided with a coil t of relatively high resistance and a coil t of relatively low resistance. The coil 6 is permanently connected with a test line all leading to those test contacts in the connectors which belong to the subscribers station. The coil 23 is connected with the test line 0 leading to the test contacts of the call-seekers.

Moreover, the test lines of the call-seekers are connected by way of contacts t of the cut-off relays TR and by way of individual series resistances a with the coil 6 of the common starting relay E of the sub-group in ques.-' tion, whereas the coil 6 is connected with a series resistance 9 common to the sub-group. When a call relay R operates both the coils of relay E are connected in circuit, the ac tion of the current in coil e exceeding that,

of the current in coil 6 If, for example, call relay R of subscriber T operates, it closes the contacts r 1 Then a current flows from the grounded battery G by way of feeder 100, conductor 40,-and from here 7 common series resistance g conductors 46,

47, contact of relay R thence together with the current suppliedby way of coil 6 by way of conductor 48, contact i .ground and back to the battery. The coils 6 e are alike, whereas resistance 9 which is in series with winding 6 is "greater than the individual resistance 2 in series with coil 6 Consequently the current in coil 6 exceeds that in coil 6 and relay E is energized. Relay TR which only operates when there is a materially stronger current in coil t cannot, however, attract its armature. Owing to the contact 0 at relay E being closed relay B of the call-seeker AS set to the fifth sub-group, to which the calling subscriber belongs, is energized. Referrin to Fig. 2,'current flows from battery G by way of feeder 100, conductors 26, 49, coil of relay.

B rest contact If, conductor 50, switch spring 8 contact is, conductor 25 (Fig. 1),

contact a conductors 51, at, 47, contact 1 of relay R conductor 48, contact i to ground. By 'attracting its armatiire the energized relay 13 brings about the following changes in connection: By

opening contact 6 and closing contact 5 the coil of relay B is'd-isc onnected from switch spring 8 and connected in a local holding circuit by way of contact 3), conductor 52, contact 7?, ground, and kept energized during the connection; by opening contact 6 ground is disconnected from spring 8 whereby the next call-seekersis 55, contact p of relay p, conductor 56,

winding of turning electromagnet' D conductor 56', contact I), conductor 57 conductor 101, circuit-breaker U, ground. After the first rotary step of call-seeker AS the test levers 0 0* contact with the first contacts of the test lines of the ninth and tenth rows of contacts, and then there are two shunts to the coil 6 of relay E to wit, currentfiowing by way of the individual resistance 2 branches at conductor 41 and flows on the one hand by way of resistance 2 contact t of relay TB line 0 switch spring a, conductor 58, coil of relay P series resistance w conductor 59, contact 12 of'relay P conductor 60, contact n of relay N, conductor 53, feeder 100, and on the other hand by way of resistance 2 contact 23 of relay TB line 0 switch spring 0, conductor 61', coil of. relay P series resistance w conductor 62, contact 19* of relay P conductor 60, contact of of relay N conductor 53, feeder 100 to battery G. The individual resistances 2 and 2 and the resistances w w of relays PHI are so proportioned relatively to the coil 6 that the current in this coil 0 is now equivalent to that in coil 6 whereby the armature of re-. lay E is caused to fall. When the contacts 0 o are turned farther along the test contacts of the sub-group, instead of the resistances 2 2 the individual resistances of the subscribers lines 382 and 292, and so on,

are connected in series. Relay B of the call-seeker AS raised in the meantime from the rear sub-group to thisone on account of the current of relay A being switched off onto contact 5 of relay B would thus obtain no current and not connect in series its turn ing electromagnet.

At the short transition moment of the switch-lever from one test contact to the other two individual resistances are each time connected in parallel. The short time of transition, however, does not sullice for influencing relay E. In addition, the currents in the coils of relays P, P serving for testing, the lines and in the relay TR are not sufiicient to operate the relays. Only when switch-lever 0 has arrived at contact 89 does a stronger current flow from battery G by way of feeder 100, conductor 53,

contact a of relay N conductor 60, contact 29* of relay-P conductor 59, resistance to, relay P conductor 58,'s\\-'1tch-lever 0 line 0 0011 I5 conductor 4.5, contact W,

conductor 48, contact if to ground. Relays TB and P are consequently energized.

, When relay TR attracts its armature it at contact 13 and ground from conductor 48 at contact it. At the same time it connects test line 0 with the relatively high resistance coil t and with the test wire (Z at contact t leading to the connector."

The disconnected relay R likewise releases its armature and. the circuits of the coils e. e of relay E and also of coil 13 of relay "TR are finally disconnected. Test relay P disconnects the turning electro-magnet D at contact 72 test relay .at contact I),

' and effects the connection of the lines a the switch-levers 0103 and battery G, while these lines.

5 0 leading to the first selector by way of thecontacts p 79 p respectively, with resistance w becomes short-circuited at contact p. The subscribers line a, 12 is now connected by way of switch-lever 0 contact 0 line a?, line at. (Fig. 3), and by way of switch-lever 0 contact-p line 6 line I) (Fig. 3), to the line relays A B, X of a first selector GW (Fig.8). By

short-cir'cuiting resistance 10 a fall of potential is brought about at the test lines a and (Z thereby preventing a second callseeker or a connector/being connected to If, on the contrary, two calls are present simultaneously in one sub-group, the current in coil 6 of the starting relay exceeds the current in coil c even when the test relays of the call-seeker moving over the contacts of this sub-group are connected in parallel 'with coil 6 by way of the individual resistances of the test lines which are contacted at any time while the seeker rotates. For example, if the subscriber T call simultaneously with the station T R01 during the rotationof the switch-levers of call-seeker AS relay R (Fig. 1) also closes its contacts r 1*. While only the series resistance 9 is interpolated in the circuit of coil 6 of relay E, the series resist- 50 ances 2 and a? are connected in parallel in the circuit of coil 6 Consequently, in spi" 3 of the shunts by way of the individual resistances to the contacts contacted at any time by the switch-levers 0 0* of call-seeker AS and'by way of the test relays P P connected with the switch arms 0 0 the current in coil 6 will be stronger than that in coil 6 Thus relay E will remain energized so thata'elayB ofthe call-seeker AS now lifted to this sub-group also receives current and its turning electromagnet is at once connected in circuit, whereas at the contact Flirt-relay B, owing to the ground being disconnected from the test line of the lifting steps are added.

sub-group, a thirdcall-sceker iscaused to move up at once to this subgroup. @111 after the first rotary step or call-seeker AI and after the interpolation of its test relay iupar= allel with coil 6 by way of two additi nal dividual resistances is'thc current withdrawn from winding c to such an extent that the armature of relay E can fall.- If, for es= ample, the coils e and c are of equal re;

sistance and like numbers ofturns, and if the resistance is twice as large as an individual resistance togetherwitliccoil t of: a

relay TR, audit-anindividual resistance together with thc winding of a test rela and the resistance in series with this coil twice as great as the resistance of co the diifercnce or the current in cells. 6 6? when calllng may be designated :1. w n

the switch-lever of a call iseekcr slides Over the test contacts the difference of the currents in these windings is zero- If, on the contrar there are two cal s, the difference of the currents inthe coils e, 8 during the parallel connection of: the two test relays to coil e is againequal to J- and re ay E re-' mains energized until, afteraconnection in parallelwith coil 6 of the test relays of the call-seeker which started second, the current in this 0011 c is diminished to such an extent that the armature of the relay canfall.

As follows from the abo for reaching the contacts of a calling line after the operation of a call-relay the call-s'eker has only to make the rotary steps in th sub-group,

whereas when two calls are present simultaneously in one subgroup, for reaching the second calling line the second calhseeker has to'make in addition the lifting step from the lower sub-group toward this sub-group.

When the call-seeker is raised from sub-- group to sub-group by one step, only the time of a lifting step is added to the rotary steps; on the contrary, if the callseekcr is lifted from Contact row to'contact row two During the connection of the calling line by wav of the contacts of the test relay P with the first selector GrW (-Fig. 3) the operative electromagnetS of the side controlling switch ST of. this selector is at once energized in the following circuit: bat" tery G (Fig. 2), feeder 100,- conductor 53,

contact n of relay N conductor 60, contact 79 conductor 0", conductor 0 (Fig. '3),

electromagnet S lever s of the side switch ST in its first position, conductors 63, 101,

circuit-breaker U, ground. After the cirreleased, a current flowing from battery G (Fig. 2)'by way of feeder 100, conductor 6%, electromagnet M serving for releasing the seeker, conductor 65, releasing relay 1 contact 71 line m conductorm (Fig. 3), rest contact b of relay B conductor 66, contact p of test relay P conductor 67, lever S in its second position, ground and back to the battery. The energized relay N holds the releasing circuit by way of contact n conductor 68 and contact it closed until the call-seeker returnsinto its initial position and opens contact k The test relays P, P and the lifting and turning electromagnets H and D are kept cut-out, while the call-'seeker returns, by the contacts 11), n which are interrupted when relay N operates. After contact it has been opened by the falling switch shaft of the seeker, the current in electromagnet M and in relays B and N is interrupted, whereas the connection of contact lv with test line 10 is done away with by opening contact k call-seeker'AS then remains in'the initial position as first reserved seeker. Simultaneously with the described closure of the releasing circuit forthe call seeker, the releasing electro-magnets N9 1V 81 of side switch .ST and of selector (JWV are connected in circuit by way of conductor 69, so that the side switch also returns into its normal position. The object of this testing of the telephone branches of the calling line is to return the call-seeker into its normal position when the calling subscriber, without selecting, replaces his receiver on the hook-switch.

For connecting into circuit the releasing circuit by way of the electromagnets M and N there is provided at every call-seeker a contact i which is closed every time the callseeker, when rotating, is not stopped at any of the subscribers contacts of a sub-group and has been rotated beyond the row of the same. This might be the case when the test line of the calling subscriber at this callseeker is faulty or when the subscriber breaks off the call while the call-seeker is rotating. The same case can also occur, if, when oneof the test levers passes over an engaged line, on account of the disconnected individual resistance of the same insufiicient current is withdrawn at this moment from coil e of relay E, so that the call-seeker which is set in the meantime to the same sub-group likewise connects its turning mag net in circuit. The last mentioned callseeker which then finds no calling line closes contact 2' after running through the row of contacts so that it is released and thrown down.

In the modified system according to Figs.

5 and 6 the callseekers of the groups of subscribers are not connected permanently with first selectors, but are connected with these by way of a system of second call-seekers. In this manner the same first 7 selectors are made accessible for several groups of subscribers. Since the number of call-seekers per group of subscribers must be greater by a certain amount, on account of the arrangement of sub-groups, than the number of the connections proceeding sin'iultaneously from one group oi.

subscribers, as a seeker must always remain set in front of each sub-group the number of the first selectors must be correspond ingly greater when the call-seekers of the group of subscribers are connected directly with the fir seiecttns. When employ-- ing autoi'natic switches for connecting the call-seekers of the groups of subscribers with idle first selectgrs, on the contrary, the number of the required first selectors may be considerably less than that of the call-seekers. For, on the one hand, found in practice, the per .ntage or mutz'ineously-speaking subsnn'ibers out of a large number is less than, for example, in a group of only 100 subscribers, so that for this reason a less number of first selectors is groups of subscribers, but, on the other hand, the number of the same does not. re quire to be increased corresponding to the greater need for call-seekers, since each of the idle seekers does not engage a first S8 lector as in the case of a fixed connection of seekers and selectors The arrangement according to Figs. 5 and 6 is to be thought of as inserted be-- tween the arrangement according to 2 and 3. The lines running out at the right of Fig. 2 now lead to Figs 5 and 6, whereas the lines running out of Fig. 6 lead. fir t to the similarly designated tines of Fig. In addition, unimportant changes in the connection according to Fig. 2 are. necessary and indicated therein in dotted lines. A calling line is also now connected without any delay with a first selector by way of the contacts of the call-seeker of a group of subscribers and by way of the contacts of the additional automatic switching devices the setof contacts oi? these switching devices are also divided into sub-groups and here also one switchingdevice or apparatus is set by preparing steps to each sub-group. The switching devices thus likewise tori n call-seekers and are designated second call-seekers hereinafter. hen a call is present, a second call-seeker is started at once simultaneo sly with the first callseeker. -As every second call-seeker can reach 10d lines- 0f the first call-seekers, whereas in each group of subscribers about 13 call-seekers are required. the second call-seekers and the first selectors connected with these can serve for, say, 7

required when they are accessible to several lines a 3, .6183 ncctcd to the fifth sub-group of the same sethe lines of the call-seekers of the groups of su'bsci ibers are led to different groups of the second call-seekers and for the purpose of mixing them better are connected to different sub-groups in the same group. Thus in Fig. 6 the lines a 6 of call-seeker AS and the lines a 5 of call-seeker A8 are connected to the sets of contacts of the second call-seekers AS, AS, and

so on, while the lines a 6 of call-seeker- AS and the lines a I)? of call-seeker AS of the same group of subscribers are connected-to the sets of contacts of the second call-seeker AS, and so on, of another group, to witthe lines a flfi are connected to the fourth sub-group of the callseekers AS, AS, and so on, while the of thecall-seeker AS are conlector. In like manner as the call-seekers according to Fig. 2, the second callseekers which are driven only in the one direction and examine the sub-groups, so that on 'each sub-group only one free call-seeker to be set on the contacts of a first callseeker occupied at a group of subscribers for a call. In similar manner, here also the test line of the sub-group is engaged by the switch spring 8" and the .tcst line of the advance or higher sub-group is tested b means of the'switch spring 8" and the re-' lay A, whereas the calls at the sub-group are received by means of relay B by way of the switch spring .9 The second callseekers are also provided with test levers 0 0 and test relays p, p in order simultaneously to test two horizontal rows of contacts of one-sub-group.

When arelay B of a call-seeker for the subscribers lines operates a starting relay in the corresponding sub-groups of the second call-seekers is switched into circuit, whereby a second call-seeker is started simultaneously with the first call-seeker. As soon-as relay B of call-seeker AS has been energized when subscriber T is be ing called, as described above, it closes the contacts 6 I) provided for the second 7 call-seekers, when a current flows from battery G on the one hand by way of feeder 100 (Fig. 5), conductor 105, coil 6 of relay E conductor 106, resistance c0 conductor 107, contact If of relay TR conductor 108, coil 25 conductor 109, contact 2f of relay TH conductor 110 (Fig. 2), contact I) of relay B bconductor 52, head contact 0 to ground, and, n the other hand, by way of feeder 100 (Fig. 5), conductor 105, coil c of relay E, series resistance 9", conductors 111, 112, contact 25 of relay TI-I con 7 second way of contact 5*,

are also provided with switches SS is ready.

relay A of call-seeker sistance g 'is greater than resistance w the current in coil e exceeds that in coil 6 and by attracting its armature relay E closes cqntact 6 whereby relay B of the call-seeker AS set to the fourth sub-group is energizedin the following circuit:battery G, feeder 100 (Fig. 6), conductor 11 1, relay B, rest contact 5 conductor 115, switch-lever 8H3, conductor 116 (Fig. 5),-contact e of relay E conductors 117, 111, 112, contact t of relay TH conductor 113 (Fig. 2), B ground. The energized relay B switches its own coil for the duration of the connection into a holding circuit by conductor 118, head contact 12 to ground and the turning electromagnet D the seeker by way of feeder 100, conductor 119, contact n of the releasmg relay N conductor 120,. contact of.

the test relay P conductor 121, contact of the test relay P conductor 122, electromagnet D, contact 6 ofrelay B conductors 123, 101 and circuit-breaker U to the battery 'G, and causes the switch-levers 0 to o to rotate at the contacts of the fourth sub-group, whereas by opening contact 6 AS is made currentless, whereby the lifting electromagnet H of seeker AS is cut into circuit and this seeker is lifted to the fourth sub-group.

As soon as switch-lever 0 of call-seeker AS contacts with test line '0 a stronger current flows, from battery G by way-of feeder 100 (Fig. 6), n of relay N conductor 124, contact 1) of test relay P conductor 125, resistance we, test relay P conductor 126, switchlever '0 conductor 0 (Fig. 5'), coil t of relay TR", conductor 109, contact t of relay TH, conductor 110 (Fig. 2), concontact 6" of relay conductor 119, contact I tact b of relay B conductor 52, contact h to ground, whereby relays TR and P are energized. By attracting its armature relay TR" interrupts at the contacts t t the circuit of the coils e and e interpolates by way of contact t and conductor 127 its relatively high resistance coil- 25 in the circuit of the test relay P and at contact 25 interpolates the auxiliary cut-out relay TH in the following circuit: batteryG, feeder 100 (Fig. 5) conductor 128, relay TH conductor 129, contact conductor 127, (Fig.2), contact I) of relay B conductor 52, contact 7L ground. By breaking contact 1) relay TH thus energized, cutsout coil t test line .0 and maintains the'circuit of its own coil by way of contact i By attracting its armature the energized relay P disconnects the turning electromagnet D at contact 39 cuts out test relay P at of relay E",

of relay TR from' lines a 6 leading to the first selector -GVV by way oft-he contacts p 79 '0 respectively', with the switch levers 0 0 and battery G, whereas resistance w is shortcircuited at contact p. Call-seeker AS now remains on lines a 6 of call-seeker AS independently as to whether the latter is still moving or has already arrived at the contacts of the calling line. Electromagnet S of the first selector GW is connected to the battery Gr in the following circuit: feeder 100 (Fig. 6), conductor 119, contact n of relay N conductor 124, contact 72 of relay 12, conductor 0 (Fig. 3), electromagnet 8, lever 32 of the'side switch ST in itsfirst position,-conductor 63, feeder 100, circuit-breaker U, battery G, and moves controlling switch ST from thefirst into the second position. If, in the meantime, the

relays A, B of the selector connected with lines a 6 are not ener ized call seeker 7 D 7 AS is at once released, current flowing from battery G by way of feeder 100 (Fig.

6), conductor 130, releasing electroinagnet M releasing relay N contacts n", m, m (Fig. 3), rest contact Z) of relay B conductor 66, contact 22 of test relay P conductor 67 second position of lever S to ground and back to battery. In order that relays A, B can be energized when callseeker A8 is still rotating and the connection with the calling line is not yet made, lines a 6 (Fig. 2) are connected by way of rest contacts p", p of relays P and P and a'contact n at relay N But if, after call-seeker AS has reached the calling line and lines a 6 have been connected by I Way of contacts 29 p of relay P and the switch-levers 0 0 with the lines (L b relays A B of selector GlV are not energized, the above described interpolation of releasing electromagnet H and releasing relay N of the second call-seeker By interrupting its confalls and closes contact 25 whereby the following releasing circuit of call-seeker 118 is closed: grounded battery G, feeder .1180

tact m (Fig. 2), contact t of relay (Fig. 12), conductor 641, electromagnet conductor 65, relay N contact 92 con- TH contact t of relay TR, conductors 1 27, 110 (Fig. 2) contacts 6 of relay B conductor 52, contact 71}, ground, and both call-seekers are brought into the rest position, while relay TH likewise becomes currentlessi after contact if at call-seeker AS is broken. In like manner call-seeker AS would be released if when rotating it found no call-seeker which has been started for receiving a call at a subscribers line and closes; ontact 5 If, on the contrary, callseekernAS when rotating found no calling line and closed contact 11 when relay N is being energized the connection of the lines a If at contact of is opened and relays A B are rendered currentless' In the modified system according to Fig. .7 the switching devices for connecting the call-seekers with idle first selectors are formed as pie-selectors which are moved at the same time as the call seekers are started and are stopped at the contacts'of the lines leading to an idle first selector, it being indifferent whether the call-seeker is still moving or has already stopped at a calling line. The pre-selectors according to Fig. 7 are to be thought of-as arranged between Figs. 2 and 3, the lines proceeding from Fig. 2 leading to Fig. 7, Whereas the lines leading to Fig. 3 proceed from Fig. 7. In addition, the unimportant changes indicated'by dotted lines in Figs. 2 and 3 must be taken into "consideration. The pre-selectors connected to the call-seekers -of one and the same groups of subscribers select at various groups VW", vw V'W, respectively, each of which tests the lines "of 10 first selectors; pre-selectors VVV, VW connect with a group of first selectors, pre-selectors VW VlV withanother group of the same. The lines of the first selectors are, moreover, displaced relatively to one another at the contacts of the pre-selectors, as shown in Fig. 7, from pre-selector to pre selector, whereby a better mixing and consequently more uniform utilization of the first selectors is obtained. When relay B of callseeker AS is operated relay B of the selector is simultaneously energized in the following circuit: grounded battery G, feeder (Fig. 7), conductor 131, rest contact 91 of the pre-selector switch shaft, conductor 132, relay B conductor 113 (Fig. 2), contact b of relay B ground. The energized relay B interpolates the turning electromagnet D of the pre-selector in a circuit leadin from battery G, by way of rest contact i conductor 132, contact 6 electromagnet D conductors 133, 101, circuitcurrent, from conductor 132 to conductor I 134 byclosing contact? i andopening 71 The currents in the coils ofrelay B and turning electromagnet D are "maintained by way offconductor 131, contact11 ,conductor 134, contact p of the test relay 1?, conductor 135 and contact 6 of relay B. As soon as switch-lever has reached the test line 01, of'a free first selector, the following circuitis closed: grounded battery G, feeder 100, conductor 136, contact 6 of relay 13, resistance to, relay P switchlever 0 test line n (Figs. 7 and 3), relay V first position of the switch-lever s of the controlling switch ST, ground. The relays P and V areopcrated. The energized relay 21 disconnects at contact p the relay B a d turning electromagnet D connects by way of contacts 12 p the lines a 12 with the lines a, b, and directly connects at contact pthe battery to the coil of relay p by way v of feeder 100, conductors 131, 134 and contact p. The energized relay V interpolates electromagnet- S in the following circuit; battery G, feeder 100, conductor 137, contact 11 of relay V conductors 138, 0 electromagnet S switch-lever 32 in the first position, conductor 63, circuit-breaker U, ground. If, after the controlling switch ST has been broughtint'o the second position, the relays A, B have not been energized in the meantime, the releasing electro magnet N 31 is out in and test line a isdisconnected at switch-lever 8 The relay P? which has become currentless dropsits armature and closes again the circuit of turning electr'o-niagnet D at contact 79 and connects the releasing magnet M of the callseeker AS in the following circuit: battery G, feeder 100 (Fig. 2), conductor 64;, electromagnet M, conductor 65, relay N, contact n conductor m (Fig. 7), contact 2', conductor 139, contact 4 of relay P conductor140, contact b of relay B conductor .110 (Fig. 2), contact I) of relay 13, conductor 52,"contact it, ground, whereby the call-seeker is thrown back, while the preselector rotates further until the current for n the turning electroniagnet of the switch shaft is cut off by opening contact 71 The numbered switch at the subscribers station comprises a finger dial whichwhen wound up grounds both branches a, Z) of the line and when returning makes interruptions in the 'a-branch,whereas the b-branch remains continuously grounded in the meantime. When the numbered dial returns into its-rest or normal position the ground is disconnected from both the branches and the latter are connected in series by way ofthe microphone at the. station.

At the first selectors GW, e. GW 81 in Fig. .3, are arranged three line relays A, B, X, of which relay X has differential coils which neutralize one another "when both coils are connected in series by way of a subscribers line. lVhen the iinebranch is grounded at the number switch of the stations the armature of relay X is attracted and closes a local holding circuit for the coil of relay B. In like manner, at the consubscribers'line and in addition a super-;

visory relay Y for the called subscribers line. Backward testing-of the branches 0, b. has not been provided at the connector, and the controlling switch' of the same makes no preparing step when the connector is engagcd by a selector.'

Making a complete telephonic connection between two subscribers will. now be described with reference to Figs. 1, 2, 3 and 4, the lines proceedin from Fig. 2 being thought of as leading directly to Fig. 3. The telephonic connection of two subscribers in the modified system according to Figs. 5, 6 or 7 will then be readily understood having regard to what has been explained above. The system operates as follows: Subscriber '389 of the fifth sub-group in the fourth group of subscribers wlshes to be telephonically connected with subscriber 456.. He takes up his telephone R from the hookswitch H and rotates his dial F by inserting his finger in the fourth hole. After removing the telephone R from the hookswitch H a current flows from battery G by way of feeder 100, conductor 141, coil 1 of relay R conductor 1412, contact i of relay TR- line branch a hook-switch H, primary induction coil p, microphone M and the choking coil D in parallel with the latter, line branch 6 contact 15 of relay TR ,'.c0nductor 143, coil 2 of relay R to ground and back to the battery. The energized relay R whose coil 1 remains energized while numbered dial F is being wound up and the line branch is being grounded by way of spring f, closes the contacts 1, 7, whereby current traverses the coils e of relay E The stronger current in coil 0 closes contact 6 and relay B of call-seeker S is hereby energized. The latter cuts into circuit the'turning electromagnet D at contact: b and simultaneouslyreleases the test line 15 of the sub-group in question by opening contact 2), whereby. another call-seeker is lifted toward this. ,The turning electromagnet D moves the switch-levers 0 to 05 of the call-seeker over contacts of the fifth sub-group until the switch-lever 0 has reached theftest-line 0 The test relay p and the coil t of the cut-out relay TR are then energizedby way .of the test line. Relay TR disconnects relay R? from the line branches and interrupts the current in the coils e 0 of relay E, and also connects to the test line 0 9 the high resistance coil 23 and the testline (Z of the connector of this group of subscribers connected with this coil.

\Vhen attracting'its armature, relay P disconnects the turning-electromagnet D and test relay P short circuits series resistance w connects the line branch of thecalling subscriber with the line branches of the first selector Gil- 3, and also closes the circuit of the selector electromagnet S connected to the circuit-breaker US By short-circuitingresistanczefc and disconnecting coil 27- of relay TR t relay R a fall otipotential is brought about at the test line 0 (Z preventing .the interpolatlon of-- nether "call:

seeker or a 'connector'ln the line, W hile,'0 w l' ing to the interpolation of electroniagnet S controlling switch ST is moved from-the,

first into'the second position when the circuit is subsequently broken at the C1I'C111t breaker U. Immediately after .test relay has been energizedthe following clrcurt 1s 1 closed: battery G,'fecder1O0 '(F1g. 3), con-'- ductor 14-1, relay A coil 00 of relay-X conductor 145, switch-lever 8 of controlling conductors b (Fig. 3)','switch-lever a, ,coil 00 of, relay m, relay B ground, and

the relays A, B become energized.

-When winding up th dial F at the subscribers station, by grounding the line branch current is withdrawn from coil 00 ed that coils traversed by current energizes relay X and contacts m at are closed. By closing contact 0: current in relay B is maintained from battery Grby way offeeder 100, conductor 146, seriesresistance w", contact 0'2 relay B and ground, and simul-' taneously a weak current flows in the reverse direction in the coil x and line branch b preventing the' armature of relay X falling even during impulses of current by Way of the line branch (1 In the second position of the controlling switch ST 'Q electro-magnet S is energized again by way of switch-lever s conductor l4i7,'co'ntact at,

ground.- The energized relay B3111 hereby keeps the releasing circuit of selector GVW' and call-seeker AS open When the num-' ber switch returns branch line a is interrupted four times and relay A which becomes currentles's connects each time, owing to armature falling, "thelifting electromagnet H tobattery G byway of feeder 100,1 condli'ctor "148, switch-lever 8, conductor-'1 9,'electromagnet H rest contact of relay At, conductor 1&7, contact w and ground.- After the last interruption of the branch line 12 the ground is disconnected from -the branch lines at the number switch at the station; Both branch lines are then connected' in series'again .by way of the microphone, and relay X allows its armature to fall whereas relays A, B remain energized. Owing to the interruption of the current in the coil of the electromagnet moved into the third position. magnet S3 is again energized by relayP, conductor 67, contact h, of' the switch shaft and ground. The turning elec-v tromagnet is then connected to battery G by tromagnet D conductor 101, circuitbreaker U" and ground and rotates the the test and telephone lines of the connectors. .As soon as switch-levef 0" has reached line c *'6f-the first free connector Lw rtesf relay P is energized in the following cir'cuit: battery G, feederlOO (Fig. 4), conductor 202, rest contact hf of the @0 line 0 switch-lever o test'r'elay P 31 and ground. By opening its contacts 7)- and p the energized relay P renders'the electromagnets S D 'currentle'ss and shortcircuits at contact; 79 the resistance to. A fall of potentialithen exists at the line/0 and prevents a'second testing relay on this line being energized, while electromagnet S which has become currentless brings the controlling switch ST to the fourthposition, in which the-relays A B, X of the selectorGW, are disconnected from thelines a, b, andthe' lines a, I) connected with the branch lines a 6 are connected by 'way of switch-lever 8 conductor 152, switch-lerero or switch-lever s 5, conductor 153, switch-lever o fi respecthus with the relays A, B, X of the connector LW. lin'spite of relay B having become currentless, theQclosure of the releasing circuit for the selector GrW"? and the ,call-seeker AS cannot take place on account of the open contact 12 at relay P In like manner as previously the corresponding relays of selector GW, the relays A, B* ,X are now energized bwayof the subscribers branches, by closing contact an relay X, which is energized corresponding' to the tens of therequirednumber when the numbered dial is wound up, interpolates electromagnet S, in the; following circuit battery G, feeder 10Q,{ conductors 204, 205,

series resistance "w C0 ndl1 0t01" 207, electro- 9, at each interruption of the branch line a electromagnet' H switch-lever 8, conrelay Y ground. After the first lift the rest S314 at contact w the controlling switch is way of conductor 1 18, swit ch-lever 33, con'-' ductor 150, contact 1r of test-relay P elec switch-levers e 0 0 over the contacts of switch shaft, conductor 203, series resistance resistance w, conductor 151, switch-lever contact an, conductor;-;206, switch-lever s,

oundlf When the dial returns,

Electroway of switch-lever 8 conductor 66, contact of tively, with the branch lines a, ba -and relay'A connects the lifting electromagnet HP-in 'the cir cnitzr Battery G, feeder 100,- conductors 20, 205, contact an, conductor 206, rest contact of relay A conductor 208,

ductor' 2.09, contact 3 of the supervisory contact h of the switch. shaft is opened, Whereas the 'o1. erative'eontact h is closed. The test line 0 remains connected to the battery, in spite o'f'contact' h being opened byway of conductor 210, contact 12 of relay B, conductor 211, switch-lever 8, conductor 212, contact 1 of relay Y, conductor 213, feeder 100;. v

After the'numbered dialhas returned into its rest position electromagnet S becomes currentless owing to contact 00 being opened and moves the controlling switch'ST into the second position, electromagnet S being connected again to battery G'in the following circuit: battery G, feeder 100,. conductor 214', contact 32 of test relay-*P,. conductor 21-5, switch-lever s, resistance w electrocontacty of relay Y to ground; As-soon as relayX becomes currentless again after the sixth rotary "ste'p,- '=owing' to'contact-az becoming closed the-lline dfof the desired subscriber is;tested,' and When-this is-free the following c'ircii'itjs closed: battery G,

feeder 100, 'conductor213, contact 3 of relay Y, conductor 212,-. switch-lever 8, conductor 11, contact 6 of relay B, conductors 210,203," Contact 00 of relayX, conductor 216, resistance 10, relay-LP, sWitchlever 0, line d coil '6 of relay-T11 ground. The relays P, TR are when 'd gized, and 'W'hilethe latter disconnects the call-relay R at the contacts I? from the branch lines (6 ,16 and the individual series resistance 2 from the test line e leading to the sets of'c'ontacts of the callseeker and connects together the test lines 0 J? by attracting itsar'matu're, relay p short icircuits" the series resistance w at contact p interpolates the choking coil Dr at contact p and interrupts the cur-' rent in. electromagnet S 'at contact 79 B short-circuiting resistance "10 afall of potential is produced at:';t,e st lines 1Z and c".n1aki1 ig the line appear engaged and preventing the excitation of the test relay of anotherconnector or-call-se eker testing on this, hereas o'wingto electromagnet S becoming currentless controlling switch ST is' brought from the second into the third position. Electromagnet S .is herebyagain energized in thefollowingcircuit: battery G, feeder 100, conductor 213, conof contacts 1 'L with the conductors 220, 221. .as the called subscriber takes his telephone :110111 the hook-sWitclnthe following feed- 'tact y conductors 212, 2125, switch-levers s, resistance w, electromagnet- S, ground.

if, on the contrary, the test relay 1* cannot be energized owing to the subscribers line being engaged, the subscriber hears an f? engaged signal, since when the controlling switch .reniains in the second position the secondary coil of the common buzzer device SM (Fig. 4) emits current by way 'of condenser 0 contact i.\vhich is-closed alter the first rotary step of the connector,

conductor 217-, switch-lever s, condenser to the branch 6 and by way of this to the subscribers. station, which current produces a buzzing noise in the telephone of the station. v

In the third position of the controlling switch the turningelectroniagnet D and the common buzzing device SM are disconnected and the li'nes I) are connected by way of condenser 0 switch-lever a or by way of condenser 0 switch-lever s with the-lines 220, 221, while a call relay L is interpolated in a local circuit proceeding from battery G,'by Way of feeder 100, conductor 222, a call distributing switch RV, conductor 223, call relay L, switch-lever s, conductor 209, contact y of relay Y to ground. Vhenever line 222 is connected with line 223 at the call dis jtributer relay L is energized. By attractjing its armature this relay causes a calling current to be sentto the station which is --tobe called from the calling source-of current. Q. byway of conductor 221, contact Z of ;relay L, conductor 225, switch-lever 0, line (6456, call-bell of station T line 6*, jsWitch-lever 0 conductor 226, contact Z of relay L, conductor 227 and back to the gcalling source of current. pauses in calling, on the contrary, the co During the uctors 225 and 226 are connected by Way and I. Yes GClilVGlV AS S0011 111g circuit to the microphone of the same is switch-lever 0 line 0 microphone of station T line 6 switch-lever- 0,

conductor 226, contact l of relay L, con-- of relay ductor 221, switch-lever s, conductor 228,

relay Y, ground. The energized relay Y disconnects relay L at contact 3 and affects the direct connection of line 211- with the battery Gat'contact- 2 disconnects the battery from line 212 at contact 1 and short-circuits the coil of electromagnet S at contact 3 Electroinagnet S Whichv has become cu-rre ntle'ss hereupon moresswit'ch ST into the fourth position and the subscribers are finally telephonically. connected. The telephonic circuit is as follows: station TW, line a igs. 1 and 2), switch-lever contact 12 line a line a (Fig. 3), switch-lever s conductor. 152, switch-lever "0 line o condenser 0 switch-lever a, conductor 220, contact 1 conductor 22o, switch-lever a, line a subscribers station T line 6*, switch- -lever 0 conductor 226, contact 1', con ductor= 221', switch-lever s condenser 0 line if, switchd'ever 0 conductor 153, switch-lever .9 line 6 line 6 (Fig. 2),

- contact p ,switch-lever 0 line b line b ductors 232,230, electromagnets N, M,

(Fig. 1),-- and back to subscribers station T P. By replacing the telephone and.mak- 'ing currentless the relay B and relay Y,

the calling and called'subscribers can each close the circuit of the releasing electro- -magn'ets M, N at contact 5 and 11 respectively, and'interrupt the current in line 0 at contact :6 and contact 3 respectively. If subscriber T replaces his telephone first, the electromagnets M l l are connected to battery G in the-following circuit: battery Gffeeder 100, conductor 213,

conductor 231, contact h, ground. Subscriber T can close the releasing circuit even when subscriber ,T has not announced himself, to wit by way of feeder 100, conductor 213, .7 contact 3 conductor 212 switch-lever, s in the first, second and third positions, conductor 211, contact 6 conductors 232, "230, electromagnets N, M,

conductor contact h, ground. Owing to test line 0 becoming currentless after the interruption of the battery line at contact 7 org relay]? allows its armature to fall. Contact p is hereby closed and the circuit for the releasing electromagnets M, N of selector GrWV and electromagnets M N of call-seekers AS is simultaneously closed. Both selectors return into their rest or' normal positions and callseeker AS is connected in its initial position to the reserve seekers of the subscribers group e For the purpose of fully disclosing my invention I have explained and described in .lletail some illustrative embodiments of the same which I consider necessary in order that'it may be understood; but it is not to be understood that I limit myself to such illustrative embodiments in detail, as my invention con'iprehends a universalsystem, the specificiorms of which admit of many variations without departing from the spirit and scope of my invention.

. I claim:

1. In an automatic telephone system the combination with a plurality of subscribers lines and selecting and connectingdevices for connecting a desired line with a calling line, of a call seeking switching device,

adapted to niovein two kinds of switching steps to seek a calling line, banks of cOntacts in said switching device connected with subscribers lines, said banks being devided in sub-groups, said switching dev ces moving in one kind of step independently of a call being present, relays and connections for moving a switching device-in the other kind of step, when a call is received, to find the contacts of said bank connected with the calling line.

2. In an automatic telephone system comprising subscribers stations, calling devices in each subscribers station, an exchange, lines connecting said stations with the exchange, one calling device for each line in the exchange, call seeking devices adapted to move in .two kinds of switching steps to seek a calling line, selectors and connectors for connecting in the exchange a calling station with the called station, said. selectors and connectors being set by the calling devices in the stations the combination of banks of contacts arranged in rows ,to which tire lines of a group of subscribers are led in multiple connection, a call seeking switch provided with switch arms for each bank of contactsand means for setting said switch to a calling line, with means for setting one call seeking switch automatically to each part of the rows of contacts, Whic parts each form a sub-group in the group independently as to whether -a call is present in the sub-group.

3. In an automatic telephone system, the

combination of a plurality of subscribers lines, switching means in each subscribers station, 'an exchange, lines connecting said stations with the exchange, selectors and connectors for connecting in the exchange a calling station with thecalled station, of call-seeking devices to seek the calling line and to connect said line with an idle selector, combined with banks of contacts devided in sub-groups, connected with a group of subscribers lines, relays for automatically setting call-seeking devices to eachsubgroup of contacts independently of a call set and for moving them to the contacts of a calling line, a suflicient number of call seekas the call seeking device in reserve at this 10 ing devices being provided-for each group sub-grouphas been started by a. call.

of subscribers lines so that at least one idle In testimony whereof I have signed my 4 reserve call seeking device is free for enname-to this specification in the presence of gagement, and releasing means to unlock two witnesses. the locking device of a Sub-,grO-up when the GEORG GRABE. call seeking device is started to take charge Witnesses: of a call, and relays for setting a reserve HENRY HASPER, call seeking device to asub-group as soon 1 -WOLDEMAR HAUPT.

Copies 61' this patent may be obtained for live cents each, by addressing the Commissioner of Patents,

Washington, D. 0. I

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