US1799175A - Automatic telephone system - Google Patents

Description

April 7, 1931. MERK AUTOMATIC TELEPHONE SYSTEM Filed Jan. 30, 1929' Patented Apr. '7, 1931 PATENT OFFICE FRIEDRICH Manx, or rnAnKFonr-oN-THn-MAIN, GERMANY AUTOMATIC TELEPHONE SYSTEM Application filed January 30, 1929, Serial No. 336,237, and in Germany February 25, 1827.

' The invention relates to automatic telephone systems and, in particular, to so-called final selectors or connectors. It relates to means on these selectors, by which. it is possible to select a free final connecting line when adjusting the selector to the'call number of a v subscriber, whose stationisconnected to the contact area of the line selectorby a plurality of the subscribers lines. The invention provides for improvements in the arrangements the adjustment of the line selector concerned to a free subscribers connecting line. 7

The invention is hereinafter described with reference to the accompanying circuit diagrams which diagrammatically. represent two constructional forms of the invention, and particularly for a small automatic telephone system in which thesubscribers are directly connected, by means of so-called line finders, with connectors, which the calling subscriber adjusts, in a manner well-known to the expert, to a definite subscribers num' ber. That the invention may be used for larger systems, in which other types of selectors are connected inseries with. the connectors, is apparent to the expert inthe art.

Referring to the drawings, Fig. 1 shows the circuit arrangement of a line finder with a lineselector, in which the line selector is of the so-called panel type, in which thezadjustment to groups of subscribers and individual lines is done by a step-by-step movement in a vertical direction. i

Fig. 2 shows the circuit arrangement of an auxiliary switch according to the invention which is allotted to a'set of line selectors as shown in Fig; 1 that is, to a set of selectors in which the bank contacts are in multipleconnection, as usual, with the same subscribers lines.

Fig. 3 shows another circuit arrangement of an auxiliary switch which can be used for this purpose. It is to be observed that the switching device according to Fig. 1 can cooperate either with an auxiliary switch according to Fig. 2 or with an auxiliary switch according to Fig. 3. In this case the ends of the lines in Fig. 1 indicated by IVI and emphasized by small circles may be assumed to be connected either with the ends of the similarly indicated lines in Fig. 2 or with those in Fig. 3. r

The mechanical part of the line selector is diagrammatically shown in the drawing for better representation. Line selectors of the type assumed here are described in British Patent No. 275,255. The invention is not bound to this particulartype of line selector, but'it appeared appropriate for simpleillustration, to use such a line selector as 'a basis for the description of the invention.

It may be assumed that the subscribers lines are combined. in groups of 100 subscribers and that the bank contacts of'a set of, for instance, line selectors are connected in multiple in the well-known manner, so that each line selector of a set can make connection with each subscribers line of the associated 100 group of subscribers.

Further, it may be assumed that not only a single line leads from the contact banks of the associated set of line selectors to a particularsubscriber but a whole group of such lines, for example, four, five or six lines, making it immaterial to the calling subscriber as to which line "of this plurality of lines he selects, since he can speak over any of the lines to the subscribers station required.

The difi'erent subscribers lines which lead to the one point of connection which is connected to the contact banks of the line selectors, in the above mentioned manner, by'several lines, may obviously either be connected to points located in succession in the contact area'or may be distributed irregularly in the contact area, as desired. The connecting with a tree line of the multiple-connection subscriber is effected in the first case by means of the auxiliary arrangement according to Fig. 2, and in the second case by the aid Ofthe auxiliary arrangement according to Fig. 3, as described in detail in the followin It may be assumed that a subscriber N of a telephone exchange desires to make connection with a subscriber who is connected to the contact area of a line selector FS with a plurality of lines. It may then be assumed that the several connections are successively connected to the bank contacts and that only one definite call number is allotted to the subscriber.

lVhen the calling subscriber N picks up his receiver, a relay T, connected to his line in the oflice, is operated in a well-known man ner, which relay, in a manner likewise wellknown to the expert, causes a line finder LF, which need not be described here in detail, since it is absolutely well-known to the expert and forms no part of the invention, to set itself on the contacts of the calling line. This line finder as usual, consists of three rotatable brushes which are diagrammatically indicated in the drawing in the usual The devices which cause the mechanical adjustment of the line finder have not been represented for the sake of simplicity.

-When the testing brush of the three mentioned movable brushes of the line finder engages with the contact at, which is allotted to the calling subscriber N, then a current flows from the negative pole of the battery through the right winding of the relay T, the closed. working contact of the relay, the contact a, the testing brush of the line finoer, the right winding of a relay V the closed inner right working contact of a relay G1, (which, in a manner of no interest here, is only excited during the operation of the line finder) the left winding of the relay V to the positive pole of the battery. It may be mentioned here that, for the sake of clearness, the working contacts belonging to each re lay are shown separated from the relays. The association with the relay is indicated everywhere by a fine dotted horizontal line. In the circuit just mentioned, the relay V operates and, through its left working contact, directly connects its right winding to the positive pole, so that it now becomes independent of the condition of the relay C The relay V connects, through its right working contact, a. current circuit from the positive pole of the battery through the contact mentioned and the left outer resting contact of a relay V the closed right outer working contact of the relay C (excited as mentioned above) and the winding of a relay R, to the negative pole of the battery. The relay R is excited.

At the same time, a relay A, bridged across the speaking wires, is connected with the subscribers line through the other two brushes of the line finder, located in the speaking wires of the line, and is excited by a current, which flows through its left and middle winding in series connection. The relay A isthe so-called impulse relay of the subscriber which, in a well-known manner, is repeatedly deenergized by operating the dial at the calling subscribers station. At each deenergization, it closes, through its right outer resting contact, the current circuit for the working magnet of a line selector FS allotted to the line finder.

The current for the working magnet H flows as follows: from the positive pole of the battery through the closed right Working contact of the excited relay V the closed inner right working contact of the relay R, the closed right resting contact of the relay A, the closed right outer resting contact of the testing relay P, the winding of the magnet H to the negative pole of the battery. The magnet H is repeatedly energized and deenergized and lifts the movable contacts of the selector F8, in a well-known manner. At the first lifting step, the movable part of the line selector FS allows the foot contact k, to close (which is shown separated from the movable part of the line selector for the sake of clearness), whereby a current circuit is provided for the relay V which is connected to the outer right working contact of the impulse relay A, which circuit is closed at the attraction of the armature of the re lay A, following the first falling off of the armature, as follows :from the negative pole of the battery, through the two windings of the relay V arranged in parallel, the contact a choke coil D,, the right outer working contact of A, the right inner working contact of R, the right working contact of V to the positive pole of the battery. The special arrangement of the parallelly connected windings and the series connection of the choke coil Dr in this circuit prevent the relay V from being operated by the current impulses flowing during the dialling operation, so that it only responds if, at the end of the first series of impulses, the right outer contact of A remains closed for a longer period.

The first series of impulses moves the movable part of the line selector FS as far as the lower group (comprising ten lines), in which the several connections of the wanted sub scriber must be located. It may be assumed, for example, that these lines are located in the third tens group it is unimportant, however, whether the connections are located in the first, second or a following group.

When the corresponding series of inniulses is completed, the relay V will operate in the circuit explained above. Due to the excitation of V a current circuit is completed from the positive pole of the battery. through the right working contact of V the magnet S in the line selector, the left inner working contact of the relay V the left inner working contact of the relay R, the left inner rest In this circuit, the magnet S and. the relay V., are excited. The magnet S is these-called brush releasing magnet of the line selector which, in the well-known manner, operates that set of the different movable parallellyconnected contact brushes of the line selector, which co-acts with the selected tens-group of lines, as explained in detail in the above-mentioned British patent.

The relay V by its left inner resting contact opening, opens the short circuit of its left hi gh-ohmic winding, so that the latter is now inserted in the current circuit indicated through the magnet S, which thus becomes deenergized. By again operating his dial 1),, the subscriber sendsout a second series of impulses by means of which the movable set of brushes ofthe selector FS, selected by the magnet S, is brought to the desired connection number of the subscriber with multiple connection.

It may be assumed that the first contact allotted to this called subscriber is the second contact in the selected tens-group. This tens-group is the second one from the bottom in the diagrammatic illustration. Whilst, as usual, each connecting point in the contact area has three contacts and consists of the two speaking wires [6 and b and a test line connection 0, only two wires are connected to the contacts of the multiple connection which correspond to the adjusted number, in the assumed case 32, and the two wires are really connected to the contacts ofseries of contacts Z2 and c. This two-wire line, as indicated in Fig. 1 to the right at I), and 0 is the so-called starting line.

I Vhen the subscriber, for the purpose of adjustment to this starting line b 0 sends out current impulses, in the case assumed, two current impulses, then he again causes repeated deenergization of the relay A and thus immediate deenergization of the relay V (which slowly attracts according to the above but is of such a construction that it quickly releases its armature at the interruption of the current). The relay V however, holds its armature firmly, since it is traversed by current in a circuit from the positive pole to the magnet S, in the manner described above, and, from here, through the inner left resting contact of the relay V and its own left working contact as well as its two windings in series connection to the minus pole. At the same time, due to the deenergization of V the relay B, connected to the left outer the positive pole, after the relay 0 had released its armature.

On the completion-of the second series of impulses, the relay V again slowly attracts its armature in the manner already indicated and by this means interrupts, at'its left innor resting contact, the currentcircuit for the r'elayV which as mentioned, isa slowly releasing relay. In the period between the disconnection of the relay V and the falling off,

' of the'armatures of V the relay P is connect-ed in the following current circuit: posi tive pole of the battery, right working contact of the relay V left outer working contactof V left outer working contact of V bothwindings of the relay P in series, right resting contact of the relay Y, testing wire 0 and testing brush of the line selector FS,

testing wire 0 of the above described starting line, at VI to the testing wire 0 in Fig. 2 and through the right'arm S of a con trol switch Sttof the auxiliary switch AS, Fig. 2 and having, for example, five brushes) in the first position as shown, the relay C to the negative pole of the battery. The five brushes of the control switch St arediagrammatically illustrated next to one another and, by means of small figures on the contacts wiped over by the brushes, the position in which a control brush touches the corresponding contacts is indicated' At the twelfth step, the control switch again comes intothe position 1. In this circuit, the reits right inner working contact and thus makes the testing line C, of the startingline set for further calls.

The relay C in Fig. 2 connects, through its left outer working contact, a current circuit for a relay U which circuit extends from the negative pole of the battery, through the right winding of the relay U, the left resting contact of the working magnet D for the switohing arms of the auxiliary switch AS, the outer left working contact of the relay C the second controlswitch arm in the first position, as shown, to the positive pole of the battery. In this circuit relay U responds and completes the circuit for the working magnet D mentioned through its right inner working contact. The working magnet D consequently moves its four contact arms forward by one step. At the same time, the left resting contact of the magnet D is opened, so'that relay U becomes deenergized and due to its right inner working contact opening, the magnet D also becomes deenergized. By this means,

the resting contact of D is again closed, relay U 1S again excited and the workmg magnet D likewise again inserted,so that the brushes of the switch are moved forward st'ep-by-step over the contacts, due to the repeated energizing and deenergizlngof the magnet 1),, until the third brush comes on the line 12 which leads over the connecting point I to the line selector FS adjusted to the starting line. At this moment a current circuit is made from a transformer T9, through the relay W third brush of the switch AS, line 12, left middle working con tact of the relay P of the line selector FS, starting line 5 left inner working contact of the relay C to the transformer. To the primary winding of the transformer, a source of alternating current G is connected through the middle working contact of the relay C so that an alternating current, which energizes the relay VJ, flows in the current circuit completed according to the above. The relay V connects, with its left outer working contact, a current circuit for the working magnet D of the control switch St which moves the control switch brushes into the second position. In position 211 of the control switch St, a current circuit for the relay U is now closed through the first control switch arm, which runs from the negative pole of the battery, through the left winding of the relay U, the right resting contact of the magnet 1),, the first control switch brush, to the positive pole of the battery. By moving the switch St forward into the position 2, the current circuit for the working magnet D of the switch AS is interrupted at the second control switch brush, so that the brushes ofthis switch remain in the selected position. Furthermore, the current circuit for relay C and relay P has been interrupted at the fifth brush S of the control switch St, so that relay P is deenergized and its middle left working contact opens, whereby the current circuit for relay is interrupted.

The working magnet D of the control switch S5, in spite of the opening of the left outer working contact of the relay W, is again energized in a current circuit which runs from the negative pole of the battery, through the winding of the working magnet D the left working contact of the relay U, the left brush of the control switch St in the position 211, to the positive pole of the battery. hen the working magnet D responds. the latter opens its resting contact and thus interrupts the current circuit of the relay U, which, in turn, again interrupts the current circuit of the magnet l) by the opening of its left working contact. By this means the nmgnet D an .in closes its resting); contact and again :cites relay U, so that in this changing operation the relay U periodically excites the working ma; iet D2, and this latter then moves the b Wires of the control itch St each time by one step. At each excitation of the relay U, a current circuit for the working magnet H of the line selector FS is closed, which runs from the positive pole of the battery, third brush of the control switch St in positions 2 5, the

right outer working contact of the relay U, second brush of the switch AS, line 13, point III, line 14, right outer resting contact of the relay P, working magnet H, to the negative pole of the battery. It may be assumed that, in the contact area of the line selector FS connected to the starting line 7),, four lines are arranged in succession, these lines leading to the same subscriber. In this case, the current circuit (just described) for the working magnet H of the line selector is completed in the four positions 2-5 of the control switch St, so that the brushes of the line selector are moved successively over the individual lines of the wanted subscriber. Such a line is diagrammatically represented by three wires, indicated by m, in the centre of the contact area of the line selector FS. If the brush of the line selector engages with a free line, then the testing relay P responds in well-known manner, and the testing current flows from the testingline connected with the negative pole of the battery through the testing contact of the line selector, the testing brush, the line 0, the right resting contact of the relay Y, the two windings of P in series connection. the point IV, the fourth contact arm of AS, the fourth brush of the control switch St in the positions 2-5, to the positive pole. The relay P short-circuits its left winding with its right inner working contact and thereby prevents, in the well-known manner, any further connections to the line laid through the line selector FS. A source of calling current G is connected to the wanted subscribers line through the inner and middle left working contact of the relay P. In the calling current circuit is located, in well-known manner, the left winding of a relay Q, which only responds when the called subscriber lifts his receiver. When the relay Q becomesenergized due to the communication of the subscriber, it connects the speaking lines through its inner and middle left working contacts, so that the feeder relay Y becomes energized, which, due to the opening of its right resting contact, inserts the right winding of the relay Q in the current circuit through the line 0. The relay Q connects the positive pole of the battery to the line 0 with its right contact, so that the line is now prevented, in the well-known manner, against further wiring, independent of the condition of the testing relay P.

The responding of the relay P in the line selector FS when the brushes of the line selector meet against a free line m, causes no alteration whatever in the auxiliary switch AS in Fig. 2. lhe working magnet D of the control switch is further excited stepby-step in its current changing operation with the relay U, and switches the brushes of the control switch St further as far as the resting position. This may be, for instance, the position 12 which corresponds to .contact of the relay U to the working magnet D V I If the connecting lines leading to the same subscriber are not all arranged in succession in the same line group, of the contact bank of the line selector and connected to the starting line 0 t then, according to my inven tion, the auxiliary switch illustrated in 3 is used, theline connections IVl of-which are supposed to be connected in the same way with the correspondinglyindicated line connections of Fig. 1, as was previously'the' case with Fig. 2. i v

It may be assumed thatthe starting line to which the line selector is adjusted by means of the numerical current impulses of the subscriber, corresponding to the number of the wanted subscriber, is again the line' (indicated by the wires 6., and c in the middle group of lines of the line selector FS, and that one of the connecting lines leadin g from the various lines (not represented) to the same subscriber is connected in'the upper contact area group, as is diagrammatically indicated by the lines 0 leading, to the'stat'ion N l l V On adjusting the line select'o'r to the starting line, the relay P of the line selector FS and a relay C again become-energized through the wire 0 With its left outer working contact, relay C closes a current circuit for the Working magnet D of the fourarmed switch AS of Fig. 3, this circuit running from the positive pole of the battery, through an interrupter U (Fig. 3), the middle resting contact of a relay W3, the left outer working contact of the relay C ,'the winding of the working magnet D to the negative pole of the battery In this current circuit, the working magnet D is intermittentlyexcited and moves the'four brushes of AS forward step-by-step, until the third brush meets the line 12 leading over I, which line is connected with the line selector FS which is adjusted to the starting line "0 6 At this moment a current circuit is completed, which runs from the transformer Tr, through the left winding ofthe relay lv the middle working contact of the relay C the third brush of AS, the 11119.12, the left middle working contact of the relay in the selector FS, the line and the brush b of this selector, the wire t of the starting line to the transformer Tr. An alternating current generator G is connected to the primary coil of the transformer, Tr, through the left inner working contact of the relay 0 so that an alternatingcurrent flows in V the current circuit mentioned andexcites the relay WV which, due to its left inner resting contact opening, interrupts the current circuit for the working magnet D so that the brushes of the switch remain on the lines leading; to theadjustedline selector FS. The relay W completes, with its left outer worklng contact, a current circuit, in which a relay K is excited and which runsfrom the negative pole of the battery through both windings of the relay V in Fig. l and the closed foot contact of the line selector FS, line15, the left brush of the switch AS,

winding of relay K, left outer Working contact of the relay Wgto the positive pole of the battery. The relay 'K is energized and with its left .inn'er working contact com pletes a current circuit for the working magnet D of a'three-armed control switch St,

from the positive, through the interrupter T1,, the left inner Working contact of the relay K, the left inner resting contact of a relay P the working magnet D to the negative pole of the battery. v

In this current circuit, the working magnet D isintermittently energized and moves for- Ward the brushes of the switch Ststep-bystep. Connected to the contacts wiped over by the third brush of the switch St arelines c which emanate from the testing wires of the different connecting lines 0 leading to the subscriber N These lines lead, in a wellknown manner, to the 0 contacts in the contact area of the line selector alloted to the connecting line, and also, to the one winding of the relay T0 of each connecting linev 0, the other endof which is connected with, the negative pole of the battery; As soon as the brush contacts on a line a to which a line selector is not already connected, a current circuit is completed in which relay- P is energized. This current circuit runs from the negative pole of the battery, through, the leftwinding of the relay T0 line a, third brush of St, both windings of the relay P the left outer working contact of the relay. K to the pole of the battery. The relay P becomes energized and, with itsleft inner resting contact, interrupts the current circuitfor the working magnet D so that the switch St remains in this position. Relay P short-circuits its right winding with its right inner working contact and by this means bars the line 0 against'further connection.

When the relay K responds the current circuit for the relay in line selectorFS and for the relay 0 41118 to: the opening of the right outer resting contact of the relay K, had already been interrupted. Thus the relay P has fallen off and, with its right outer resting contact, completes a current circuit for the Working magnet H. of the line selectors FS. This current circuit runs from the positive pole of the battery through an interrupter U, the right outer resting contact of relay R, the left outer resting contact of relay Q, the right til resting contact of the relay V the right outer resting contact of V a closed running contact 10 (which is closed in a well-known manner when the selector FS leaves the resting position and is opened when it is moved as far as the maximum position), the line lei, the right outer resting contact of the relay P, the working magnet H, to the negative pole of the battery. The working magnet H is intermittently energized and moves the brushes of the line selector FS as far as the end position, in which the contact 101 is opened, in a wellknown manner, by mechanical means, and the switch pawl of the inaget H is removed from the rack, so that the brushes of the line selector fall back into the normal position. On reaching this position, the foot contact in, of the line selector is opened, in well-known manner, so that the previously described current circuit of the relay K is interrupted and the relay K falls oil. With its middle right resting contact the relay K completes a circuit for the relay A from the negative pole of the battery, through the right winding of the relay A the left arm of a further fourarined switch SA in the first position, the middle right resting contact of the relay K, the left winding of the relay A the left outer working contact of the relay P the third brush of the switch AS, line 12 point 1, line 12, magnet S of the line selectors FS, right working contact of the relay V to the positive pole of the battery. In this current circuit the control magnet S of the line selector FS does not respond, but the relay A is energized, which, with its right inner working contact, closes a current circuit for the working magnet D of the switch S6 from the positive pole of the battery through an interrupter U the right inner working contact of the relay A theworking magnet D to the negative pole. The working magnet D is thus intermittently energized and moves the brushes of the switch S6,, forward step-bystep. After the first step, the current circuit for the working magnet Dv is kept closed directly in the position 2-33 ot' the switch S6 over the second brush oi the latter. The 'connectionfof the contacts, which are wiped over by thethird brush of the switch St, and by the first brush of the switch St is made in such a way that the switch S6 must carry out a number of steps corresponding to the tens figure of the connecting line connected through the third brush of the switch St, in order to be conductively connected with the first brush of the switch St. The connection ofthe contacts which are wiped over by the fourth brush of the switch St, and the second brush of the switch St is likewise made in such way, that from the moment when the third brush of the switch S25 has been connected with the first brush of the switch St, the switch St must carry out a number of steps corresponding to the units figure of the line, in order to be connected with the second brush of the switch St.

The switching steps of the switch S6 act on the working magnet H of the line selector F8 in a current circuit from the positive pole of the battery, through the right outer working contact of the relay A the right inner work contact of the working magnet D the second brush of the switch AS, point 111, line 14:, right outer resting contact of the relay P, working magnet H, to negative pole.

At each excitation of the working magnet D this current circuit is completed through the right inner working contact of this n1agnet, so that, at each step of the switch S6 the line selector FS is also switched forward one step, and thus a current circuit is completed from the positive pole through the left inner working contact of the relay A the first brush ot' the switch AS, line 15, point II, the contact 71,, both windings of the relay V to the negative pole. The relay V is energized and, at its right resting contact, prepares the circuit for the restoration of the line selector.

At the moment when the third tens-brush oi the switch 3% meets on the contact which is connected with the negative pole through the corresponding (first) brush or the switch S26, the magnet S of the line selector FS is energized in a current circuit from the negative pole, through the two brushes mentioned, right outer resting contact of the working magnet D left outer working contact of the relay P third brush of AS, line 12, line 12, magnet S, right working contact of the relay V to the positive pole. As already described herein, the magnet S operates that brush set of the line selector FS which corresponds to the group of lines in which the desired connecting line is located.

Then, after further current impulses, the fourth (units) brush of the switch St engages with the contact to which the corre sponding brush of St is connected, then a current circuit is completeditroin the positive pole, through the right winding of the relay W the two mentioned brushes or the switches Eli and S, the right middle working con- 7 tact the relay A the right winding of the relay A to the negative pole. In this current circuit, relay W 3 is energized and, with its right inner working contact, completes a urrent circuit fl'OIIl the positive pole of the battery, through the contact mentioned. and through the fourth arm of AS, point IV, both windings of the relay 1 right resting contact of the relay Y, line 0, c brush of the line select-or ITS, owire of the connecting line, left winding of the relay To to the negative pole. The relay P responds and sends, through inner and middle left working contacts, a calling current from the source G into the speaking linc,whereupon the further completion or" the connection is effected as previously described.

The calling subscriber is thus connected with one of the connecting lines 0 dist-ributed to the Contact area of the line selector FS, these lines being quite free at the time of his call. 1

The energizing circuit of N3 is immediately again interrupted when the switch S6 is switched forward into the normal position, that is until the position 33 is passed, in which its second arm disconnects the interrupter U All the relays f the auxiliary switch of Fig. 3 are now again in their normal positions, so that the auxiliary switch AS, St St is available for another call.

I claim:

1. An automatic telephone system comprising lines of calling subscribers and lines of subscribers to be called; line selectors hav ing contact areas with which the lines of the subscribers to be called are connected; means for connecting the lines of acalling subscriber with a free line sel ctor; a plurality of subscribers lines from the station of a subscriber to be called, which lines lead to contacts in the said contact areas of the line selectors; a starting line allotted to said station and connected to the contact area of the line selector; an auxiliary switch connected to said starting line; means for connecting the auxiliary switch to the line selector connected to the starting line; and means in the auxiliary switch for effecting the connection of said line selector to a free line of the said plurality of lines of the subscriber to be called.

2. An automatic telephone system comprising lines of calling subscribers and lines of subscribers to be called; line selectors having a contact area with which the lines of subscribers to be called are connected; means for connecting the lines of calling subscribers with a freeline selector; a plurality of subscribers lines from the station of a subscriber to be called, which lines lead to contacts in the said contact, areas of the line selectors; a starting line allotted to said sta tion and connected to the contact area of the line selector; an auxiliary switch connected to said starting line; contacts in said auxiliary switch; lines leading from these contacts to the dilierent line selectors, with the contact area of which said lines to be called are connected; means for moving the contact arms over said contacts of the auxiliary switch; a testing current circuit which is.

completed when the contact arms are adjusted to the line selector connected to said starting line; means for stopping the contact arms in the adjusted position; and means in auxiliary switch for effecting the connection of said line'selector to a free one of said plurality of lines of the subscriber to be called.

3. An automatic telephone system comprising lines of calling subscribers and lines of subscribers to be called; line selectors with contact areas to which the lines of subscribersto be called are connected; means for connecting the lines of calling subscribers with a free line selector; a plurality of subscribers lines from the station of a subscriber to be called, which lines lead to contacts in the contact areas of the line selectors; a starting line allotted to said station and connected to the contact area of the line selector; an auxiliary switch connected to said starting lines; contacts in said auxiliary switch; lines leading from these contacts to the difierent line selectors, with the contact area of which said lines to be called'are connected; means for moving the contact arms over said contacts of the auxiliary switch; a testing current circuit which is completed when the contact arms are adjusted to the line selector connected to said starting line; means for producing a flow of alternating current in said testing circuit for testing purposes; means for stopping the switching arms in the adjusted position; and means in the auxiliary switch for effecting the connection of said line selector to a free one of said plurality of lines of the subscriber to be called.

4. An automatic telephone system comprising lines of calling subscribers and lines of subscribers to be called; line selectors with contact areas to which the lines of subscribers to be called are connected; means for connecting the lines of calling subscribers with a free line selector; a plurality of subscribers lines from the station of a subscriber to be called which lines lead to contacts in said contact areas of the line selectors; a starting line allotted to said station and connected to the contact area of the free line selector; an auxiliary switch connected to said starting line; means for connecting the auxiliary switch to the line selector connected to said startling line; means in the auxiliary switch for effecting the connection of said line selector to a free one of said plurality of lines of the subscriber to be called; and means for releasing and restoring the auxiliary switch to the normal position directly after the connection of the line selector to a free line.

5. An automatic telephone system comprising lines of calling subscribers and lines of subscribers to be called; line selectors with contact areas to which the lines of subscribers to be called are connected; means for connecting the lines ofcalling subscribers with a free'line selector; a plurality of subscribers lines from the station of a subscriber to be called,'which lines lead to contacts in said contact areas of the line selectors; a starting line allotted to said station and connected to the contact areas of said line selectors; an auxiliary switch connected to said starting line; means for connecting the auxiliary switch to the line selector connected to the starting line; means in the auxiliary switch for testing the plurality of subscribers lines from said station 7 of the subscriber to be alled; means in the auxiliary switch for offecting the connection of said free line selector to a free one of said plurality of lines; and means for releasing and restoring said auxiliary switch to normal position directly after the connection of sail line selector to a free line.

6. An automatic telephone system comprising lines of calling subscribers and lines of subscribers to be called; line selectors with contact areas to which the lines of subscribers to'be called are connected; means for connecting the lines of: calling subscribers with a tree line selector; a plurality of subscribers lines from the station of a subscriber to be called leading to contacts in said contact areas of the lines selectors; a starting line allotted to this station of the subscriber to be called and connected to the contact areas of the line selectors; an auxiliary switch connected to said starting line; means for connecting said switch to the line selector connected with the starting line; means in the auxiliary switch for restoring said line selector; means in said switch for automatically testing the plurality of subscribers lines; means in the switch for setting the line selector onto the contacts of a tested tree line of said plurality of lines; and means. for releasing and restoring the switch to normal immediately after connection of the line selector with a tree line.

In testimony whereof I have hereunto atfixed my signature.

FRIEDRICH MERK.

Images