US1999104A

US1999104A - Telephone installation

Info

Publication number: US1999104A
Application number: US712825A
Authority: US
Inventors: Merk Friedrich
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-02-17
Filing date: 1934-02-24
Publication date: 1935-04-23
Anticipated expiration: 1952-04-23
Also published as: BE394383A; GB419189A; DE618575C; FR750800A; DE606205C; DE635919C; US1972199A; FR44932E; GB413054A

Description

Filed Feb. 24, 1934 4 Sheets-Sheet l April 23, I,1935. F. MERK 1,999,104A

TELEPHONE INSTALLATI ON April 23, 1935. Fl MERK 1,999,104

TELEPHONE INSTALLATI ON Filed Feb. .24, 1934 4 Shets-Sheel. 5

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l V a a 50i-0 fl-JP y a ai f I y rtf-.1;

fil-J? f/f/fDR/cn MER/f gum TELEPHONE INS TALLATI ON Filed Feb. 24, 1954 April 23, l1935. f

, l contains two similarly formed partial multiples, rows of contacts. yDuring the setting, this switch` l Patented pr. 2.3, 1935 f UNITED STATES" PATENT OFFICE TELEPHONE INSTALLATION Friedrich Merk, rrankfort-on-tne-Main;

Germany ApplicationA February. 24, 1934, rsenin No. '112,825 In Germany February 25, 1933 17 olaims.- (Cuve- 18) This invention relates to multiple connection A further feature ofthe invention is to make systems for telephone installations and is intendpossible the setting of theconnector on the coned to provide certain new and useful improvetacts of its second partial multiple. For this ments in mechanismsof this character and class. purpose, the invention provides for changing the No. 656,731 filed February'14th, 1933, now yPatent tion. ,Y

No. 1,972,199, of Sept. 4, 1934, a'multiple oonnec- In order that they invention may be thoroughly tion'system for telephone installations is set forth understood and be more readily'carried into vefhaving selectors and lines subdivided intogroups feet, some examples of construction in accord- In my co-pending patent application Serial connectorgon'initiation ofthe auxiliary opera- 5 y in which provision isy made for mutual assistance ance therewithfwill now be described with ref- 10 ofy the selector groups, in that the lines of one erence to the accompanying drawings. In these group, in addition to being multipled to ,onev seexamples of construction there. is aselector havlector group, are also similarlyy multipled to aning a flat bank multiple and a multiple brush other selector group. Each selectork group thus switch member movingto and fro infrontl of its the combination of which is dilerent from se- `member moves downwards under the influence lector group to selector group. cf its own weight. The inventionA is, however, The invention is concerned with a connectiony in no way restricted to the useofspecial selectors system for connectors to the multipleoi which, in but can be used also with other selectors of other 20 accordance with the invention, two groups of types. 20 subscribers lines are connected'. In this case, Figure 1 shows diagrammatically a multiple the lines of a group of 100 subscribers lines are brush selector for 100 lines; connected to the rst partial multiple of the se- Figure 2 shows a similar selector for 200 lines;v i lectors of a group of connectors which'arer se- Figure'S is a circuit diagram for a connection lected by the characteristic figure of this groupy between asubscribers set and a current impulse 25 of 100 in the preceding group selectors. The lines repeater through a call nder arranged between of this group of 100 are, however,y in addition oonthem; nected to the second partial multiple ofthe ser Figuresi and 5 are respectively the circuit dialcctors of one or more other groups of connectors grams OI'V a group selector for 100 and 200 lines which are selected by other characteristic gures which, when the desired group of connectors is 30 in the preceding group selectors. In this way, made inaccessiblenssteppedy on to the next group all the lines in the second partial multiple of of connectors.: n v the neighbouring groups of `connectors can be Figure 6 is thecircuit diagram for a connector connected, or by sub-division of the group of 100 of-200 lines which can co-operate` with the group Si; lines into sub-groups,v each kof these sub-groups selector of` Figures 4 and 5.

can be alternatively connected to different groups Figure 7 is the circuit diagram for a group seof connectors. o lector for 200 lines whichwhen they desiredgroup With this connection system for connectors, the of connectors is made inaccessible,` lselects anproblem now arises that. the preceding group se-` other groupr o-f connectors in accordance with the 40 lectors after selection of a group of connectors tens digit Of the desired SubSCrberS line. 40 must make a further .group selection ,movement` Figure 8` is a circuit diagram for ay connector for the auxiliary operation in order to be able to for 200 lines which can co-operate with a group seize a connector to the second partial multiple selector according to Figure '7. oiy which the desired subscribers line is also con- 'I'he selector multiple of Figure 1 consists of nected. For the solution of this problem, the ve partial banks VV,` each having two groups of 45 invention provides that when the connectors of lines which are indicated bythe references I and a group are not available, those connectors are 6, 2 and Tand S0 yfOIth 0n the right hand Side. made inaccessible to precedingM group selectors Each gro-up of lines vcontains 10 lines. A switch so that the preceding group selectors are premember S having five sets of brushes B and a vented from hunting over theA connectors of this hush 10d T iS diag'lmmatially Shown 0n the left 50 group. This at the same time makes ther prehand side ofthe selector multiple.r Similar switch ceding group selectors suitable for being set on members can also be arranged on the other side of another group oi connectors to the second par-.- the multiple. The ,switch member as illustrated tial multiple of which the desired line is con-v is in the position of rest in which thexfree ends of nected. f the brush springs B which make the contact are 55 separated from the contacts of the group of lines which they serve by increasing amounts which, expressed in terms of switching steps, are indicated by the references y2 g5. The brush sets B are normally separated from the contacts and are only brought towards them when one of the levers I-I is temporarily actuated by a iinger F of the above mentioned push rod T. There are two iingers F for each lever H and the distances between a lever H and its appropriate actuating fingers F increase progressively. The distances between the levers Hand the irst fingers F which act on them expressed in terms of switching steps are indicated on the left of Figure l by the references mi, .r2 fc5. The distancebetween a pair of ngers F is equivalent to ve switching steps and this distance is indicated in Figure l by the references e5.

During the downward movement of the switch member S the sets of brushes arrive in sequence opposite the contacts of the rst group of lines reached by them and also the working points of the levers H arrive in sequence opposite the ringer F wlnch is the first to be reached.A When the switch member S is moved further, the brush sets arrive in sequence opposite the second finger F of a pair so that each set of brushes can be brought into use in two positions.

The arrangement for a selector multiple of twice the size of that shown in Figure l is shown in Figure 2 and will be seen to be fundamentally the same. This multiple comprises 1U partial banks V whose groups of lines are indicated by the references I l and 2 l; i2 and 22; and so forth on the right, while the switch member S has 10 sets of brushes B and the push rod 'I' has l() sets of 2 iingers The distance between two ngers F in a pair is equivalent in this case to i0 switching steps and is denoted in Figure 2 by the reference gt3. Itis to be noted that in the inoperative position shown in Figure 2 the switch member is one switching step higher than in Figure l. Therefore, the distances of the brush sets from their contacts with which they first engage and also the distances of the working points of the levers H from the lingers F are by one switching step greater than in Figure l and have therefore been denoted in Figure 2 respectively by the references @3,1141 yl2 and r2, x3, :r4 .lL

The switch member is released for the setting movements by a pawl controlled by an electroinagnet which engages with a rack connected to the brush switch member. These movements can, according to the duration of the ener ization of the magnet, be step by step or continuous movements. The push rod is actuated by the intermittent actuation of a control switch (not shown in the drawings) when this switch passes through a position determined by an appropriate electromagnet. An auxiliary switch member, again not shown in the drawings, which at times moves with the brush switch member after a set of brushes has been made effective, is also provided in the selector. A selector with such an auxiliary switch member is described in Patent 1,895,265.

The circuits will now be described for various cases. in the following descriptions, the contacts of the above-mentioned rack are denoted by the reference the contacts of the control switch by the reference m and the contacts of the auxiliary switch by the reference n. These contacts, similarly to the others, are shown in the position of rest. The figures added to the reference letters lc, m and n indicate the switch position in which these contacts are actuated.

When the receiver at the subscribers set TN shown in Figure 3 is lifted, the subscribers line is connected through a call nder AS, in a manner known in itself, to an installation for repeating current impulses and speech. The relays A and Q are thus energized and the circuit is closed through the outgoing lines a, b, c. Owing to the numerical selection. the current impulse relay A swings so that the relay V responds and is held operated together with the relay Q for the duration of the series of current impulses. When the relay A again responds after the first release of its armature, the rst current impulse proceeds over the following circuit:--

marking contact v, condenser K, marking contact and line a, setting magnet F of a subsequent selector (Figure 4),

This circuit includes a condenser in order to restrict the current impulses to a paiticular length which guarantees a step by step setting of the selector and thus makes it possible to use a setting magnet for the selector which has no large current strength. At each release of the relay A, the condenser K is discharged through a resistance w. During the transmission of each series of current impulses, a current also flows through the circuitmarking contact o, the second transformer winding, the line b, a control magnet S of the following selector (Figure 4),

(1) The 100-line group selector shown in Figure 4 cany cc-operate with the 20G-line connector shown in Figure 6. In order that the switching steps may be best understood, the Figures 4 and 6 should be placed side by side.

Two groups of 100 subscribers lines are connected to the connector of Figure 6. The first group of 100 is arranged in the iirst partial multiple of the connector, while the other group of 100 is connected to the second partial multiple of the connector. In order to be set on the contacts of this second group of 100 lines, the line selector must after the selection of the brush set corresponding to the group of l0, make an additional setting movement of 10 switching steps. The multiple connection of the double groups of subscribers lines through the individual connectors is, in this example of construction, carried out in such a way that the group of 100 lines connected to the iirst partial multiple of a group of connectors is also connected to the second partial multiple of the next group of connectors in the direction in which the group selection proceeds. Thus, if there is no connector of a particular group of connectors available for the connection, then the preceding group of selectors according to Figure 4 must be again connected to the following group` of connectors for the auxiliary operation. The group selector illustrated in Figure 4 is constructed on the principle of that illustrated in Figure 1. It has in addition, however, a group testing brush gp which during the first setting movement of its switch member, wipes over a contact bank to the contacts of which a group testing line g is connected for any group of connectors to be selected.

When the current impulse repeater Shown in Figure 3 operates and the relay Q has responded, the relay C in the group selector of Fig. 4 is energized. As already described, on the rst release of the relay A of the current impulse repeater of Figure 3, the relay V is energized and thereby the b-wire of the connecting line is connected to the battery by means of the contact v. This causes magnet sor thecontrol switch m they group selector. of vFigure 4 to be energized.v Thefcontrol switch is so constructed that ateachvenergization and de-energization, it causes the controlV switch to be stepped through one step.

During the sending out of a series ofcurrent imof the first series oi current impulses, the relayv V of the currentv impulse repeater again releases and interrupts the` circuit for the control switch magnet S so that the latter releases and the control switch is stepped into the position2. In this position 2, a contact im! of the control switch is closed andthus the winding. I of a relay U and the group testingbrush gp of the selector is con-r nected to the control switch magnet S. There are two differenti cases which will be separately considered: f 1

(a) If a connector of aselected group of connectors is available for the .making of a connection, then rthe group testing line g in thek line selector kis connected .through the .contacts Htl-31 and 4c to the positive terminal of the battery. The winding Iof the relay U is thus short circuited on closing of the control switchr contact lmZ by means of the group'testingv line and'cannot respond. The control switch magnet S responds, however, in the circuit formed by the group testing line g andrsteps the kcontrol switch into the position 3 out of which the control switch immedia-tely moves into the position 4 because there is no energizing circuit for the magnet S in Y the position 3. Owing to the passing oflthe control switch from the position 3 to the position 4, the push rod T mentioned in thefdesciiption of Figure l is mechanically rotated for a short 'timeV so that the set of brushes selected by therst setting` movement of theV group selector is innuenced by the appropriate nger F and is made effective for making contact. At the same time, an auxiliary switch is coupled tortheswitch member and partakes ofthe further movement of vthe switch member.

In position 4 of the control switch, an energizing circuit for the setting magnet F isnow closed: Y- f In this circuit, the setting magnet F is continuously energized and releases the switch member kfor carrying out a uniform movement.

tors, the relay P responds in the following testing circuit:

-l-, contact |11..Il-0, Contact 5m5-6, both windings of relay P, contact3c, testing brush, linee,

contact 2kl-31 ofV the line selector of Figure 6, relay C `The relay P short circuits its high resistance winding with the contact lp in the known manner and thus vmakes the selected connector inaccessible. The contact 2p interrupts the energizing circuit of the setting magnet F so that the switch kmember is brought to rest on this contact.

If, by means of therst setting movement ci the group selector, the third line selector group was not selected by three numerical current impulses,'but for example, the 6th connector group was selected by means of six numerical current impulses, then as has already been explained byV means of Figure 1, on the passing of the control switch'from the positionl to the position 4, the

uppermost Yset of brushes of the group selector would be made effective by the temporary actuation of the push rod T. This set of brushes is,

however, still at a distance of five switching steps from the sixth contactbank of the group selector to which the desired group of connectors` is connected. The switch member` of the group selecto:` mustthus first make an additional movement of five switching steps before the testing can take place of the contacts wiped over by the set. of brushes. For this purpose, the control switch remains in the position I while the switch meinber is displaced by the numerical current impulses through more than fivev switching steps because the contact lkIr-S is open. The energizing circuit for the setting magnet F, as in the previously described case, is closed. The testing circuit is, however, closed through the ,contact 2116-45 only on the sixth step of this uniform movement of the switch member so thatthus the five contacts of the contact bank l of the group selector are run over idlyi With the energization of the relay P, therelay C in the connector of Figure 6 is also energized, At the beginning of the further current impulse transmission, the b-wire in the current impulse repeater ofV Figure 3 is again connected to the battery sothat the controlswitch magnet S of the connector of Figure 6 is energized through the contacts lp and Mnl-40. As the contact 6m2-I0 of the group selector is open, the control switch ymagnet S of the group selector is not influenced. The control switch magnet S' is energized, closes its contact s and steps the control switchfinto the position l.

Thecurrent impulses run again through ther a-wire. The setting magnet F of the group selector is not influenced, because the contact 1m2|0 of the group selector is open. On the other hand, the numerical current impulses ract on the setting magnet F of the connector and cause arstep-by-step setting of the switch member. ,p If, for example, five current impulses are sent out, then at the end of the series of current impulses, the fifth set of brushes of the connector is in front of the fth contact bank. At the end of the series of current impulses, the control switch magnet S is again devoid of current and causesthe control switch to be switched again into the position 2. On the transference from the position l tothe position 2, the push rod T of the line selector is temporarily operated soV that the selected 5th set of brushes is influenced and is made' effective for making contact. At the beginning of the `second series of current impulses, the control switch magnet S' is again energized by the b-wire and switches they controlswitch into the position 3. The current impulses pact again onthe setting magnet F' through the closed contact s; at the end of the current impulse transmission, owing to the de-energization of the control switch magnet S', the control switch proceeds to the position and by means of the contact 21:14 closes the testing circuit through the relay P'. The control switch is immediately further switched from the position 4 into the position and closes the following circuit:-

it is then held in that position by the continuous energization of the magnet S. The testing thus takes place only during the transference of the control switch from the position 4 to the position 5. if the line is free and the relay P has responded, then the calling current is sent out through the closed contact 2s of the control switch magnet. The alternating calling current runs through the windings oi the relay Y which, however,l cannot respond to the alternating current because the lower winding is short-circuited by the contacts 2s. As soon as the called subscriber answers, direct current flows in the known manner through the windings of the relay Y. The relay Y is energized, interrupts the energization of the control switch magnet S with its contact ly so that it is released, switches out the calling current with the contact 2s and switches the control switch into the position 6.

The breaking of the connection is independent oi the calling subscriber. The steps involved, however, have nothing to do with the present invention.

(b) The case will now be considered in which when the group selector is set on the third group of connectors, there is no connector in this group which is available for the further selection. In this case, the contacts HCl-3l and 4c in all connectors of this group are open. The group testing line g is thus disconnected. As soon as the control switch of the group selector has moved after the rst series of current impulses into the position 2, the relay U is energized by the winding which is not, as in the preceding case, short circuited by the group testing line g. The relay U responds, together with the control switch magnet S and by means of the contact la of its winding il closes a holding circuit. The contact 2u energizes the setting magnet F and sets up the circuit:

-i-, contact 27112, contact 2u, magnet F-.

rlhis results in the switch member being lowered through a further step. The energization of the magnet F lasts only for a short time as the magnet S is energized at the same time as the relay U and switches the control switch into the position 3, out of which it passes into the position i owing to the fact that the relay S is no longer energized. When the control switch passes from the position 3 to the position Cl, the push rod T of the group selector is again temporarily actuated. Although the switch member is lowered through three switching steps by the rst setting movement of the group selector, the fourth set of brushes from the top is now influenced because, indeed, the contact 2u causes the switch member to be stepped through a further step. Thus, not the brush set which is associated with the desired third group of connectors, but the brush set which `is associated with the fourth group of connectors is made eiiective. The desired group of 100 subscribers lines is connected to the second partial multiple in this fourth group of connectors.

The selection of a free line in this group of connectors takes place as previously described.

When a free line is found, the relay P responds by means of the contact Ip, makes the seized connector inaccessible and by means of contacts 3p and 4p connects the speech wires. The contact 2p thus causes the release oi the setting magnet F and the release of the relay U. The relay U is constructed so as to be slow to release and thus still holds its contact 3u closed when the contact 3p is closed. As a result, a relay U is energized in the seized connector of Figure 6 and the following circuit is set up:-

contact 3u, contact 3p, group selector brush, line a, contact 51m-I0, contact ls, winding I of relay U,-.

The relay U lies with its contact 2u of its winding II in a holding circuit which runs through the contact lc' of the relay C' which has been energized in the meanwhile.

At the beginning of the next series of current impulses, as described, the control switch magnet S of the connector is energized by the b-wire. The current impulses act on the setting magnet F which, on energization of the control switch magnet F, is connected by the contact I s to the a-wire. After the current impulse transmission, the control switch magnet S' releases and switches the control switch into the position 2, When the control switch passes from the position l to the position 2, the push rod T of the connector is again actuated for a short time and makes the set of brushes selected by the first setting movement effective for making contact. At the same time, the auxiliary switch member is coupled to the switch member. In the position 2 of the control switch, the following energizing circuit for the setting magnet F of the connector is closed:

contact HID-31, lu', |m2, magnet F-. The magnet F' attracts its armature and thus releases the switch member for a continuous movement. As soon as the switch member ID has made 10 steps, the contact alli- 3l opens, the setting magnet F again becomes devoid of current and the switch member stops. The selected set of brushes is thus stepped through l0 switching steps. If, by means of the first setting movement, the fifth set of brushes was, for example, selected and thus made effective, then this set of brushes is now in front of the contact bank (Figure 2) of the second partial multiple.

The next series of current impulses sent out by the subscriber switches the switch member into the position 3 of the control switch. At the end of the series of current impulses, as already described, the testing takes place in the position t of the control switch and the calling current is sent out in the position 5.

As is obvious, when the group of connectors to the first partial multiple of which the desired subscribers line was connected is made inaccessible, hunting over the selectors of this group was prevented in the group of selectors arranged in front of it by energization of the relay U. The group selector was, moreover, automatically stepped on to the next group oi connectors and immediately a free connector is seized in the following group of connectors, this seized connector is provided with a change characterization through a speech wire. The change characterization was stored in a relay U of the connector and, after carrying out the tens selection through the connector, has stepped the connector on to the contacts of the second partial multiple to which the desired subscribers line is also connected. This storing of the change characterization can naturally also `be carried out by switch means belonging tol the group selector which transfer the characterization to the connector only after transmission of the series of current impulses necessary for the tens selection. Y

(2) The group selector illustrated in Figure 5 is made for 200 lines and can co-operate wthfthe f connector shown in Figure 6. The arrangement and operation willbe best understoodby placing ,the two circuit diagrams onebeside the other.

kThe construction Aof the connector of Figure 5 corresponds substantially with that diagrammatically illustrated in Figure 2. There are l sets of brushes and 20 groups of contacts H-Zi. In addition, a further group testing brush gp is, however, provided which is moved `during the group selection movement over a bank of 20 contacts to which one group testing line g. is connected for each group of line selectors. f j

(a) If `a connection is to be made to one of the groups of connectors! I-`20,then the series of current impulses acting first of allon the group selector consists of only one current impulse. On the seizing of thecurrent impulse repeater of Figure 3, .the relay Cof the groupr selector is energized. At the rbeginning` yof thetransmission of a rseries of current impulses, the b-wire in the current impulserepeater is connected to thebattery by the contact v, so that the switching magnet S is energized and moves the control switch into the position l. TheV current impulses acton the setting magnet F. kLf the first series ofr current impulses only comprises, as assumed, one cur-f -rent impulse, then the switch member is lowered' through one step and then the control switch magnet S is de-energized so that the control switch is moved into the position 2. y

At the beginningof the next sequence of current impulses, which also acts on the group selector, the control switchmagnet S is again energized and switches the control switch into the position 3. `The current impulses then influence the setting magnet F, while at the end of the sequence of current impulses, the control switch moves into the position 4 by the` de-energization of the control switch magnet S. If iive current impulses are sent out in this second sequence of current impulses, then the fth set of brushes' of the group selector now finds itself in front of they contact of the group ofconnectors I5. Inl the control switch position 4, the contact 3m4 is closed and thus both the winding I `of the relay U and also the group testing brush gp are connected to the control switch magnets.

y (b) Before the further switching steps are described, it will be briefly explained how the setting of the group selector on one of the line selector groups l|20 takes place. In this case,y thevrst series of current impulses which acts onthegroup selector consists of two current impulses. While the control switch is in the position I, the switch member is thus lowered through two switching steps and, in this case, the contact IkZ-IO is closed. This causes the energization of the setting magnetF in the following circuit:

contact 2ml, contact IkZ-g-ID, magnet F, The magnet F responds and releases the switch member of the selector for a uniform movement. During this energization of the setting magnet F, the control switch is held in the position l by the energization of the magnet S in the following circuit:

contact lml, contact f, magnet S, At the eleventh setting step of the switch member, the Contact No2-I0 is again opened and the vshort time in the following circuit: y f

setting magnet Fbecomes devoid of Vcurrent and holds the switch member in this position. Through this lowering ofthe switching member through switching steps, the second series of fingers lE' on the push, rod T shown in Figure 2 is now brought into operation for making effective the set of brushes to be selected by a second series of current'impulses. After this automatic further switching `movement of the switch member, the control switching magnet S again becomes devoid of current and brings the control switch into the position2, out of which it moves into the position 3 at the beginning of the secondseries of current impulses acting on the group selector. By means of this second series of current impulses, they setting magnet Fis again energized step by step. At the end of the second series of current impulses, the control switch magnet S releases as a consequence of the interruption of the circuit existing owing to the b-wire and causes the further switching of the controlswitch into the position 4. If thissecond series of ycurrent impulses consists of ffive 'current impulses, the

' fth set of brushes of the Lgroup selector is now rin front of the contact of thev group of connectors (c) If a connector of the selected groupof conthe absence offurther energization of the magnet S. On the transference from the position 5 to thel position 6, the push rod (Figure 2) istemporarilyl actuated and makes .the selected Yset `-o1. brushes effective for making contact. At the same time, thel auxiliary switch member 4is coupled to the switch member so that it partakes of the further setting movement of the switch member. Through the contact Im, the following energizingv circuit for the setting magnet F is closed:

+, contacts 2p, Inl I, 1m6f, ZIM- 31, magnet The magnet F responds and Areleases the switch member for a uniforrnmovement. This movement is limited to l0 switching steps because, on the eleventh step, the contact Intl opens. Immediately a free connector is found Vduring the wiping over of the 10 contacts of a group of connectors, the relay P responds in the following circuit: Y

contact '2m-l0, both windings of relay P, testing brush, line c, 2k| 31, relay C',

The relay P interruptsthe energizing circuit for the setting magnet F by means of its contact 2p and thus stops the switch member of the group selector. The connector is made inaccessible by the contact lp by short circuiting of the high resistance winding of the relay P, While the contacts 3p and n4p connect the speech wires. 'I'he setting of the connector according to Figure 6 now occurs in the manner already described. y

(d) If there is no connector of `the selected group of lconnectors available, then the group testing line y is disconnected. On the closing of the contact 3u4 in the group selector (Figure 5), the relay U is energized through its winding I together with the control switch magnet S. The relay U, by means of the contacty lu, closes a holding circuit for its winding II and by means of Contact 2u.energizes the setting magnet F for contact 4114, contact 2u, setting magnet F,

This energization is immediately interrupted because the control switch is moved into the position 5. The brief energization of the setting magnet F results in the lowering of the switch member through a further step. Thus, as soon as the control switch has moved from the position 5 to the position 6 as a consequence of the absence of energization of the magnet S, not the set of brushes selected by the numerical current impulses, but the set of brushes corresponding to the next group of connectors will be made effective for making contact. In the position 6 of the control switch, the automatic hunting of the group selector starts again and this is ended by the response of the relay P when a free connector of this neighboring group of connectors is found.

By the opening of the contact 2p, the de-energization of the winding II of the relay U is deenergized, in addition to the group selector being stepped. The relay U is made slow to release and thus holds its armature attracted for some time. On the connection of the speech wires by means of the contact 3p and 4p, the following energizing circuit for the relay U of the connector or Figure 6 is thus set up:

contact 3u, contact 3p, brush of the group selector, a-wire, contact 51m-I0, contact Is', winding I of the relay U',

The relay U responds and, in the already described fashion, stores this change characterization for the connector. By means of the next series of 'current impulses, the connector is set for the selection of the tens group of the subscribers line. For this purpose, the relay U carries out in the described fashion the automatic further switching of the connector through ten switching steps on to the contacts of the second partial multiple to which the desired subscribers line is connected. The last series of current irnpulses then makes the final setting of the selected brush sets on to this subscribers line.

(3) The group selector illustrated in Figure 7 is made for 200 lines and co-operates with the line selectors of Figure 8. The line selectors of Figure 8 are also made for 200 lines and receive in their iirst partial multiple the lines of a group of 10U subscribers lines, while to the second partial multiple, the lines of several groups of 100 subscribers lines are connected alternating from group of l0 to group of l0. These groups of 100 subscribers lines are thus subdivided into separate sub-groups of 10. To the iirst sub-group oi l0 of the second partial multiple of the connector, are connected the lines of the rst subgroup of l0 oi the iirst partial multiple of the next following group of connectors. To the second sub-group of l() of the second partial multiple of the connectors are connected the lines of the second sub-group of lO of the iirst partial multiple of the next group but one of connectors. The distance of the groups of connectors in which the individual sub-groups of 10 are connected to the first or the second partial multiple thus increases with the characterizing digit of the subgroup of l0.

This type of multiple connection of the subscribers lines in the connectors makes it necessary that the group selectors should be switched over for the auxiliary operation to various other groups of connectors when the selector of the selected group or" connectors is not available. according to which characterizing digit of the subgroup of 10 of the desired subscribers line is being dealt with. If the subscribers line lies with the first sub-group of l0, then the preceding group selector must, in auxiliary operation, be stepped on to the next succeeding group of connectors. If the subscriber-s line lies in the second sub group of 10, then the group selector must be switched on to the next group of connectors but one and if the subscribers line is in the 10th sub-group of 10, then the group selector must be stepped on to the 10th group following the selected group of connectors. In order that the group selector must be thus stepped onto the different groups of connectors, it is made for 200 lines.

As the stepping of the group selector in auxiliary operation occurs in dependence upon the characterizing digit of the tens group of the subscribers line,'that is to say, in dependence upon the current impulses which are to set the connector on the sub-group of 10, storing switch means must be provided in the group selector which store up these current impulses and, after the seizing of a connector in auxiliary operation, again transmit to the connector. Preferably, these storing devices are so constructed that they can receive both the series of current impulses sent out for the selection of the subgroup of 10 and also for the selection of the ndividual line. The storing devices can be associated in common with the selectors of a group selecting unit as they are only used in the rare case of auxiliary operation. In the connection system of Figure '7, the storing devices and the group selectors are individually t associated. For any series of current impulses to be stored, a storing switch arrangement is provided controlled by two magnets D and E. The relays U, B and J are also, however, associated with this storing switch arrangement.

(a) The steps arising in the general case when a connection is made will now be explained. When the current impulse repeater of Figure 3 isseized, the relay C of the group selector of Figure 7 responds so that the relays B and U are energized through the contact 4c. At the beginning of the current impulse transmission for setting the group selector, the b-wire in the current impulse repeater of Figure 3 is connected to the battery by means of the Contact 'D so that the control switch magnet S responds and the control switch switches into the position I. The current impulses sent out through the a-wire energize a relay A step by step which effects the step by step energization of the setting magnet F with its contact d in the following circuit:

contacts la', Znll, 2p, magnet F, The switch member lowers through as many switching steps as there are current impulses acting on the group selector. At the end of this series of current impulses, the control switch magnet S releases owing to the fact that the b-wire becomes devoid of current and switches the control switch into the position 2 in which the Contact Im2 is closed and connects the control switch magnet S to the group testing brush gp. Since, as assumed, there is a free connector in the selected group, the group testing line g is connected to the battery through the contacts Htl-31 and 4c. The control switch magnet S is energized and switches the P control switch into the position 3 out of which it moves into the position 4 owing to the absence of energization of the control switch magnet S. On the transfer from the position 3 to the position 4, the push rod T actuates, which makes and 27118 while the control switch magnet and'y y the set of brushes selected by the rst series vof current impulses effective for making contact. At the same time, the auxiliary switch member is coupled to the switch member. Through the Contact smit-i0, the following energizing circuit for the setting magnet F is closed:

contacts 5mi-I0, Znll, 2p, magnet F, The setting magnet is energized' and releases the switch member for uniform movement. This movement islimited to ten switching steps by the contact nll. `At the same time, the control switch magnet is energized through the rcontact 51nd .so that the control `switch moves into the position and out of this position,-ow ing to the absence of energization of the magnet S, into the position 6. In the position 6, the control switch magnetSfis energizedk through the contact 'Im and steps vthe control switch vinto the position 1 out of which itis again switched, due to 'the absence of ener'gization ofy the magnet S, into the position 8, in which the speech lines are connected by the contacts IImB the relay A are disconnected from the speech wires by the contacts 9m6-I0 and IDmS--IIL When the selected set of brushes arrives on the contact of a free connector, the relay P responds in the circuit:-

relay C responds in the testing circuit. At 'the beginning oi the next sequence of currentimpulses,k the control switch magnet S'l of the connector is energized by the b-wire and switches the control switch into the position l.

At the same time, the contact ls is closed. The current impulses transmitted through the awire act on the setting magnet F' of the connector. At the end of the series of current impulses, the magnet'S' releases and switches the control switch into the position 2. On. transfer from the control switch position" I to the position 2,'the push rod T is temporarily yactuated and makes the set of brushes selected by the iirst current impulse transmission effective.` At

, the beginning of the second series lof currentimso that the control ,switch moves into the position 5 in which the control switch magnet S is held energized.` Ii the relay P has been able to respond through the contacts of a free sub- 'scribers line, then theline is made inaccessible by the contact lp by short circuiting of the high vresistance winding, while the contacts 2p and 3p connect the speech wires. The sending out of the calling current now occurs through the contact-2s. As soon as the called subscriber setting magnet F.

replies, a direct current flows' through the winding of thev relay Y, the relay Y responds and 'withthe contacts 2y and 3y connects the speech wires..

(bl The case will now be considered in which there is no connector available in the desired group of connectors. y When the current impulse repeater is seized, the relayy C is ,again energized in the group selector (Figure 7) and also. the relays B and U connectedup thereby. During the first currentimpulse transmission, the kcontrol switch magnet S is energized through the b-wire and holds the control switch in the position l. The current impulses running through .the a-wire influence the relay A .which with its contact la transmits the current impulses to the If, for example, ilve current impulses are sent out, then the switch member of the selector is lowered through fivey switching steps so that the fifth brush set finds itself in 's frontY of the contact field of the group l5 (Figure 2). At'the end of the series of current impulses, the control switch magnet S is devoid of current v so that the control switch moves into' the position 2. If, as is assumed, there is no connector of this group which is available, then the group testing line g is disconnected and the control switch magnet S cannot be energized by the contact l.m2.

If now the-current impulses sent out by the subscriber which, in normal operation, serve for setting y.the connector on the tens group vof the .rsubscribers line, then these current impulses act again on the group selector. f At the beginning of the series rof 'current impulses, the control switch magnet S is again energized through the b-wire and moves the control switch into the position 3. The-current impulses transmitted through the a-wire are now transmitted by the relay A first by means of a contact la to the setting magnet F andv secondly'by means of the contact 2a to the setting magnet DI of the first storing switch device. This storing switch device is so constructed that a switch member is displaced step by step by a setting magnet DI while a force is stored, that is to say, against the action of a spring or gravity. The switch member.` is also influenced by an electromagnetxE, the armature of which controls an escapement which, on attraction and repulsion of the armature, releases the switchk memberfor a movement amounting to half a switching step so that after a setting by the setting magnet DI, it is returned by alternate energizations and deenergizations of the electromagnet EI by half switching steps back into its normal position, under the action of the previously stored force.

The switch member ofthe storing. switch device I is also displaced step by step during the further displacement yof the switch member of the group selector. If the desired subscribers line lies for example in the ninth sub-group of ten of a group of 100 subscribers lines, then nine current impulses are transmitted in this series of current impulses so that the switch member of the group selector is lowered through nine further switching steps. At the end of this movement, the fourth set of brushes from the top of the group selector thus lies in front of a nger F of the second series of ngers on the push rod T so ythat after a temporary actuation of the push rod,

the contact eld 24 can be wiped over. The group of connectors 24 which i'sseparated by nine group selection steps from the first selected group of line connector I5 is connected to this contact iield 24 as, from the assumed multiple connection, the ninth sub-group of the 10U-group l5 is connected to the second partial multiple of the connector which in the preferred operation, serves the 1GO-group 24. If, for example, there are only IG groups of connectors, then in this contact group 24, the lines which lead the group of connectors I are, however, repeated because the assumed multiple connection of the subscribers lines to the first and second partial multiples of the connectors is made cyclically through all the groups of connectors present.

At the end of the series of current impulses which transmits the characteristic digit of the tens sub-group of the desired subscribers line, owing to the de-energization of the control switch magnet, the control switch moves into the position 4. On the transfer from the position 3 into the position 4, the push rod T is temporarily actuated so that thus the selected fourth set of brushes of the group selector is now made eiective for making contact. Owing to the displacement of the storing switch device by means of the setting magnet DI, the contacts IwI, 2wI and 3wI are also thrown. The contact lwI has the the effect of preventing an energizing circuit for the control switch magnet from being closed in the control switch position 4 and the control switch thus then remains in the position 4. On reaching the control switch position 4, an energizing circuit for the setting magnet F of the group selector is immediately closed through the contact Gm4-i, the magnet F responds and releases the switch member of the group selector for a uniform movement. This movement is limited to It switching steps by the Contact 271| l as the auxiliary switch member which controls the contacts 1t was coupled to the group selector switch member on the transfer of the control switch from the position 3 to the position 4. The selected set of brushes is thus moved on by the contacts of the Contact group 24. As soon as the set of brushes iinds a tree connector, the following testing circuit is closed:

contact Inl-IQ, both windings of the relay P, contact 3c, testing brush, c-wire, 21d-31, relay C of the connector,

The relay P responds, makes the seized connector inaccessible by closing the contact Ip, interrupts the energizing circuit for the setting magnet F of the group selector with the contact 2p and connects the speech wire with the contacts 3p and 4p.

las soon as the contact 3p is closed, the following circuit for the setting magnet F of the connector is set up:

contacts lwI, lu, 3m4, 3p, brushes of the group selector, a-wire, cont-act Ski-31, contact haii-iii, magnet F' The setting magnet F' is energized and releases the switch member of the connector for a uniform movement. After the first switching step oi this switch member, the energizing circuit for the setting magnet is broken at the contact Ski-37. The electro-magnet F is, however, maintained energized in the circuit:

contacts ly, ic', Imi-IU, j', EMD- 3l magnet F', until this circuit is interrupted at the lOth switching step. By the setting of the storing switch device I in the first gro-up selector', the connector will be stepped through ten steps immediately after being seized so that the brushes oi the connector come in front ci the contacts of the second partial multiple. This change contact takes place through an energization of the setting magnet without previous energization of the control switch magnet, that is to say, in the control switch position D.

In the group selector, the control switch nds itself during these switching steps in the position 4. If now the current impulses corresponding to the units digit of the desired subscribers line are sent out by the subscriber, then the control switch magnet S is energized again by the b-wire so that the control switch is transferred into the position 5. The current impulses running through the a-wire are now transmitted through the relay A' only to the setting magnet DII of a second storing switch device. The setting magnet F of the group selector can no longer be iniiuenced by these current impulses because the relay P is energized. The setting magnet DII of the second storing switch device is actuated step by step and the storing switch device moves through as many switching steps as there are current impulses which have been transmitted. At the end of the current impulse transmission, the control switch magnet releases in consequence of the interruption of the circuit running through the b-wire and switches the control switch into the position 6. With the setting of the second storing switch device, the contacts lr/JII and 2wII are reversed. In the control switch position 6, the energizing circuit for the relay B is interrupted at the contact 8m6-|0. The energizing circuit for the relay U is, however, maintained by the contact ZwI and the resistance wl. The relay B allows its armature to release and closes the contact b.

At the same time, in the control switch position 6 there is an energizing circuit for the control switch magnet S' of the connector:

-l-, contacts IwI, iu, l3m6--|0, 4p, brushes of the group selector, b-wire, contact 4m4-I0, magnet S',

The control switch magnet of the connector is energized and brings the control switch into the position I.

By the closing of the contacts b, the electromagnet EI is energized in the circuit:

+, contacts b, i, 2u, 3wI, magnet EI,

The magnet EI responds, closes the contact eI and returns the switch member of the storing switch device I through half a step. The relay J is energized by the contact eI and reverses its contact i and thus closes the following energizing circuit for the setting magnet F of the connector of Figure 8:

contacts b, i, 3p, brushes of the group selector, a-wire, contact Is', contact 51114-10, magnet F',

By the reversal of the contact i, the energizing circuit for the magnet EI of the storing switch device I is at the same time interrupted, so that the latter releases and the switch member of the storing switch device is again released for half a step. Owing to the release of the magnet EI, the relay J is, however, also devoid of current. In this alternating operation of the magnet EI and of the relay J, the switch member of the storing switch device is thus at times released for a return movement of half a switching step, while for the carrying out of a whole switching step, a current impulse is sent out to the a-wire. The setting magnet F of the connector receives thus as many current impulses as there are current impulses stored by the storing switch device through the series of numerical current impulses sent out for characterization of the tens group.

kso

If,` as assumed, nine currentimpulses are stored,

switching stepsr so thatthe ninth set of brushes is in front of the contacts of the ninth group of 10 ofthe second partial multiple. i

By` the return of the storing' switch device I into the position vof rest, the contactswI are again reversed. The circuit; running through the b-wire for the control switch magnet S is vinterruptedy at the. contact IvwI so that the control switch ofthe connector is transferred into the position 2, the push rodi T is thus temporarily actuated and the ninth set of brushes of the connector is made effective for making contact. The contact 2wI interrupts the energization of the slow to release relay U.

As soon as after a given time the relay U has allowed its'armature to release, the following energizing circuit for the control switch magnet S of the connector is closed:

contacts IwII, lu, ISnG-IU, 4p, brushes of the group selector, b-wire, contact 5m4`-I0, control switch rmagnet S-, so that the control switch of the line selector is transferred into the position 3.' `A t the same time, the following en ergizing circuit for the magnet EII of the secondv storing switch device is closed bythe contact ZwII:

contacts b', I, 2u., ZwILmagnet EII, This magnet EIIk also co-operates with the relay kJ so that the set switch member Vof the second storing switch device II is returned in half vswitching steps into its position of rest, while'at the same time, after each full switching step, a current impulse is transmitted to the setting magnet F of the connector through the a-wire. The switch member of the connector is thus lowered through as many switching steps as there are current impulseswhich have been senti out for characterizing the units digit and the desired subscribers line. After returny ofr the storing switch device II into its position of rest, the contacts wII are reversed.y The contact l'wII interrupts the circuit through the b-wire so that the controlswitch of the connectoris transferred into the position 4.. At the same time, the contact I'wII closes the following energizing circuit for the control switch magnet S of the group selector; contact IwII, contact 1m6, magnet S,

so that the control switchis transferred into theV position ll and immediately out of this position in-to the position 8 owing, tothe absence of energizationof the control switch ymagnet S, in which position the-*speech lines are rconnected through the contacts I Ima-and l2m8. .y

In the position 4' of theV control switch of the connector, theitesting circuit :for the relay P' is closed through the contact 2121.4. The control switch is at the same time transferredto the position 'by energization of the magnet S through the contact @m4-5 in which position the magnet S is maintained energized. If the subscribers. line is free, then the relay P responds,

makes thedesired subsoribers line/inaccessible by means of the contact Ip and switches the calling current on to the speech wires by means of the contact 2p and 3p which runs over the Contact 2s' and the windings of the relay Y. f As soon as the subscriber replies, Vthe relayy Y is energi'zedf by the direct current owing through the windings` of the relay Y, interrupts kthe circuit i'or the control switch magnet S by opening its contact Iy so that the latter releases, interrupts the calling` current'by means of the contact 2s', and steps the control switch intoy the position 6;

The contacts `2y and 3y connect thespeech wires.V

It will be seen that in this example inwhich the lines of a group of subscribers lines are `both series of current impulses necessary for setting the connector are stored in the group se-V lector; The arrangement can be so designed that in the group selector only thecurrent impulses` characterizing the tens group which aresent` out immediately after the seizingof a free connector are storedsothat the units current impulses act directly on the connector.

In the described example, the group selector is, for the auxiliary operation, stepped through as many group selection steps as there are current impulses which have been sent out for characterizing the tens group' of the desired sub'- scribers line. group selector are thus made as simple current impulse repeaters. The multiple connection of the subscribers lines can naturally also be carried out in other ways,l for example,r so vthat the lines of the tenth sub-group of l0 of a group of 100y subscrbers lines are arranged in the second partial multiple of the neighbouring group of connectors randthe lines of the rst'sub-group of 10 oi this groupof 100 subscribers lines are connectedy to the second partial multiple of the connector group, 10 group selection steps away. In this case, it is necessary to provide `inthe group selector for a translation of the storedv current impulses.'

In the described examples, thecharacterizaoperation is always carried out from the pre- The storing switch means ofthe ceding group selector in dependence upon the inaccessibility of a particular group of connectors from this group selector. This sort of chang' ing. ofthe connector is not absolutely essential, as it is moreover also possible when all the connectors of a group are unavailable to change over directly to auxiliary operation, for example, through a call distributing connection from this group of connectors to a connector of another r group to the second partial multipleof which subscribers lines divided into groups, said con;l nectors in each group forming two like partial multiples, a connection between each two groups of. subscribers lines, and said two partial multi# ples of each of said connector groups, a group selector adaptedto select said groups of connectorszand to seize a free connector within ther selected group, means for making said group'of connectors inaccessible from said group selector when all connectors of said group to the first partial multiple of which the desired line is connected are unavailable, said means being adapted to prevent the initiation of hunting by said group selector over the connectors of said group and being adapted to make said group selector suitable for selecting another connector group to the second partial multiple oi which the desired line is also connected.

2. A telephone installation comprising in combination connectors subdivided into groups and subscribers lines subdivided into groups, said connectors in each group forming two like partial multiples, a connection between each group of subscribers lines and the first partial multiple of a group of said connectors and to the second partial multiple of another of said groups of connectors, a group selector adapted to select a desired group of said connectors and to seize a free connector Within the selected group, means for making inaccessible said group of connectors from said group selector when all connectors oi said group are unavailable, said means being adapted to prevent the initiation of hunting by said group selector over the connectors of said group to the rst partial multiple of which the desired subscribers line is connected and means for stepping said group selector onto a group of connectors to the second partial multiple of which said group of subscribers lines which contains the desired subscribers line is connected, said stepping means being controlled by said iirst mentioned means.

3. A telephone installation according to claim 2, wherein group testing means are provided within the group selector which are adapted 'to prevent the initiation of hunting by said selector over the connectors of a selected group of connectors rendered unavailable and in which the stepping means of the group selector are controlled by said group testing means.

4. A telephone installation comprising connectors subdivided into groups and subscribers lines subdivided into groups, the connectors of each group forming two like partial multiples, the lines of each group of subscribers lines being connected to the iirst partial multiple of a group of connectors and to the second partial multiple of another group of connectors, means for changing the connectors, said means influencing the connectors for being set onto lines connected to said second partial multiple, said means being controlled when all connectors of a group of connectors to the iirst partial mi' ltiple of which the desired subscribers line is connected are unavailable.

5. A telephone instaiiition comprising coninectors sub-divided into groups and subscribers lines sub-divided into groups, the connectors ci each group forming a first partial multiple and a second like partial multiple, the lines of each group of subscribers lires being connected to the first partial multiple of a group of connectors and to the second partial multiple of a second group of connectors, the conne' tors of each group being adapted to be set onto fr. line of its iirst partial multiple and to be set onto a line of the second partial multiple by stepping the selector brushes, means for changing a connector of a group of connectors to the second partial multiple of which the desired line is connected, said changing means innuencing the connector for being set onto lines of its second partial multiple by stepping the selector brushes, said means being controlled when all connectors of a. group of connectors to the rst partial multiple of which the desired line is connected are unavailable.

6. A telephone installation comprising in combination, connectors subdivided into groups and subscriber lines subdivided into groups, said connectors in each group forming two like partial multiples, a connection between each group of subscribers lines and the first partial multiple of a group of said connectors and to the second partial multiple of another of said groups of connectors, the connectors of each group being adapted to be set onto a line of its rst partial multiple and to be set onto a line of its second partial multiple, means for changing the connectors, said means being associated with the connectors and adapted to influence the connectors for being set onto lines connected to said second partial multiple, a group selecto-r adapted to select a desired group o1 connectors and to seize a free connector within the selected group, said selector having group testing means for preventing tne initiation of hunting by said group selector over the connectors of the selected group when all connectors of said group are unavailable, and said selector having further means for stepping said group selector onto a group of connectors to the second partial multiple of which the desired subscribers line is connected, and having means for transmitting a change characterization to a seized connector, said stepping means and said transmitting means being controlled by said group testing means.

7. A telephone installation according to claim 6 wherein the changing means of the connectors are controlled by the transmitting means of the group selectors.

8. A telephone installation according to claim 6 wherein the change characterization is transmitted immediately upon the seizing of a free connector by said group selector and in which the said changing means influence the connector for being set onto lines connected to its second partial multiple after the setting of the connector under the influence of current impulses characterizing the tenth group of the desired line.

9. A telephone installation comprising connectors sub-divided into groups and subscribers lines sub-divided into groups and sub-groups, the connectors of each group forming a first partial multiple and alike second partial multiple, both partial multiples being sub-divided into subgroups, the lines of each group of subscribers lines being connected to the first partial multiple of a first group of connectors and to the second partial multiple of another group of connectors, means for changing a connector to the second partial multiple of which the desired line is connected, said means causing the further switching of the connector onto the contacts of the second partial multiple, a group selector adapted to select the groups of connectors and to seize a free connector within the selected group, means for preventing an initiation of hunting by the said group selector when all connectors of the selected group of connectors to the first partial multiple of which the desired line is connected are unavailable, means controlled by said second mentioned means for stepping said group selector over a connector group to the partial multiple of which the desired line is connected, and said means for changing the connector being likewise controlled by said second mentioned means.

10. A telephone installation according to claim 9, in which said means for changing the connector are controlled by said means for preventing the initiation of hunting by the group selector between the setting operations of the connector in dependence upon the current impulses characterizing the sub-group of the desired subscribers line and upon the current impulses characterizing the desired line within the subgroup.

11. A telephone installation according to claim 9,'in which the means for changing the connector are controlled by said means for preventing Lthe initiation of hunting by the group selector through the speech wires of the line between the group selector and the selected connector.

12. A telephone installation according to claim 9, in which the means for changing a connector are controlled by the means for preventing the initiation of hunting by the group selector immediately upon the seizing of the said connector.

13. A telephone installation comprising in combination connectors sub-divided into groups, subscribers lines sub-divided into groups, said oo nnectors in each group comprising a rst partial multiple and a second like partial multiple, said ygroups of subscribers lines being subdvided into sub-groups, the second partial multiples of each of said groups of connectors being subdivided into -sub-groups, all sub-groups of a group of subscribers lines being connected to all sub-groups of the first partial multiple of a vgroupfof said connectors, the individual subgroups of a group of subscribers lines being also connected from sub-group to sub-group alternately to the second partial multiple of other diierent groups of connectors, a group selector adapted to select a group of connectors and to seize a free connector within the selected group,

l means for making a group of connectors inaccessub-group of subscribers lines, said stepping means being controlled by said rst mentioned means.'k

14. v.A telephone installation comprising in combination connectors sub-divided into groups, subscribers lines sub-divided into groups and subgroups, the connectors of each group forming ay rof connectors, the individual sub-groups of a group of subscribers lines being connected in addition from sub-group to sub-group alternately to said second partial multiple of other subsequent groups of connectors, a` group selector adapted to select the group of connectors and to seize a free connector within the selected group, means for preventing the initiation of hunting by said group selector when all connectors of the selected group of connectors to the first partial multiple of which the desired line is connected are unavailable, means for stepping the group selector in dependence upon the current impulses sent out for determining the sub-group of the subscribers line, said means being controlled by said first mentioned means and means controlled by said rst mentioned means for storing the current impulses for determining the sub-group of the desired subscribers line.

l5. A telephone installation according to claim 14, comprising storing means associated With said group selector for storing a plurality of sequences of current impulses.

16. A telephone installation according to claim 14, comprises storing means associated with all group selectors of a group selection unit.

17. A telephone installation according to claim 14 wherein said storing means are adapted to transmit the stored current impulses in the same number and sequence.

f FRIEDRICH MERK.