US1561292A - Automatic telephone system - Google Patents

Description

F. ALDENDORFF 7 AUTOMATIC TELEPHONE SYSTEM Filed Aug. 16, 1921 4 Sheets-$het 1 Nov. 10, 1925- 1,561,292

1 F. ALDENDORFF AUTOMATC TELEPHONE SYSTEI Filed Aug. 16, 1921 4 Sheets-Sheet 2 Malian.

Nov. 10,1925. 1,561,292

F. ALDENDORFF AUTOMAT IC TELEPHONE SYSTEM Filed Aug. 16, 1921 4 Sheets-Sht 3 Nov. 10 1925. i 1,561,292

F. ALDENDORFF AUTOMATIC TELEPHONE SYSTEM Filed Aug. 16, 1921 4 Sheets-Sheet 4 EEQQ Patented Nov. 10, 1925.

UNITED STATES FRITZ ALDENIDORFF, OF BERLIN 4N ILMERSDOR-F, GERMANY, ASSIGNOR OF ONE- FOUIB/TH TO PAUL KOIJISCH, OF NEW YORK, N. Y.

AUTOMATIC TELEPHONE SYSTEM.

Appfication filed August 16, 1921.

To all whom it may concern.

Be it known that I, F nrrz ALnnNnonrF, a citizen of the German Republic, residing at 23 Brabanterstrasse, Berlin-Vilmersdorf, Germany, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

The following is a list of corresponding foreign applications and patents filed more than one year prior to the date of filing this application: Germany, Patent No; 322, 085 of June 5, 1914; Patent No. 308,802- of January 11, 1914, application G41, 340 VIII/21 3, filed March 20, 1914; Austria, application A. 7580/14, filed November 8, 1914; Switzerland, application G. 82,087, filed November 11, 1914.

This invention relates to a switching arrangement for automatic or semi-automatic telephone exchanges.

One feature of the invention consists in calls being first extended'from one point, line, or trunk to another point, line, or trunk to a bypass comprising, a line finder or the like with a plurality of collateral line-hunting elements or brushes all or a plurality of which are simultaneously in a state of readiness to seize a calling line and to extend it to a said point line or trunk whereupon a second connection extending from the same calling line to the same point, line, or trunk is established through a second part which may include a switch or switches of a dilferent character.

Another feature of the invention consists in a talking connection being established with the aid of two switches, used transitorily in establishing the connection, in such a way that the movable contact-s of the one said switch are set onto the fixed contacts of the line of the calling subscriber, and causes a talking connection switch to be set onto the calling line, whilst the movable contacts of the other said transitorily used switch causes a second talking connection switch to be set onto the line that is to be called. The movable contacts of the transitorily used switches may be set, both onto calling and called lines.

The arrangement may also be such that the movable contacts of the talking connec tion switches may be set both onto the con tacts of calling lines and onto the contacts of called lines, whilst two groups of transitorn Serial No. 492,828.

ly used switches are provided the one of which has movable contacts that can only be set onto the contacts of calling lines, whilst the movable contacts of the switches of the other group can only be set onto the contacts of called subscribers. In another modification two groups of talking connection switches and two roups of transitorily used switches are provic ed, and the movable contacts of one group of talking connection switches transitorily used switches are only set onto calling lines, whilst the movable contacts of the other group of talking con nection switches and transitorily engaged switches are only set onto called lines.

With the trunks that extend from the talking connection switches selector-finders maybe associated which hunt for a transitorily used switch that is connected by a talking trunk finder to a free trunk.

If the transitorily used switches are divided into groups the number of identifying wires used for setting the talking connection switches onto calling or wanted lines needs only be as large as the number of transitorily used switches present in each group.

Another feature of the invention relates to a circuit arrangement for conversation meters and consists in the meter current path extending over a conductor that is separate from the connector used for selecting the wanted line. A further feature of the invention consists in an arrangement by which the called subscriber on lifting his receiver, closes a current path which includes a relay of the talking connection switch that has been set onto his line and a relay of the talking connection switch that has been set onto the calling line.

Another feature of the invention consists in an arrangement of the ringing current circuit, whereby the ringing current for calling the wanted subscriber flows over a conductor that is separate from the connector.

The switches used transitorily in establishing a connection are so arranged that, after the connection has been completed up to a certain point, they are immediately restored to normal so as to be ready for further connections.

Another feature of the invention consists in identifying circuits of a special kind by means of which calling lines which. are

I 1,561,292 PATENT OFFICE.

first extended to a certain trunk, line, or position through a bypass or by-passes are subsequently connected without the possibility of confusion with other simultaneous calls to the same trunk, line, or position through another path which may include switches of different characters from those included in the transitorily used by pass.

Still another feature of the invention consists in circuits which enable calling lines to be extended through line finders without the aid of individual line relays.

The invention also includes circuit arrangements by which a rotary switch, after it has been used to extend a connection to a trunk or line and its functions with respect to this trunk or line are completed, is in all cases caused to shift its wipers onto another trunk or line.

Another feature of the invention consists in switching arrangements by which one and the same switch is automatically changed from a switch of one character to a switch of another character.

These features and others not now specifically mentioned will be described fully hereinafter by way of example with reference to the accompanying drawings.

The invention is shown in the drawing. Figs. 1 and 5 are-diagrams which illustrate the fundamental method of establishing connections when the novel system is applied. Figs. 2, 3 and i show in detail the circuits of the switching apparatus used when the system takes the form shown in Fig. 1. Fig. 6 illustrates the layout of an exchange according to my invention in which group selectors are employed.

In Fig. 1' S S are switches: which set their own wipers onto the lines of calling subscribers and then connect the latter through their associated talking trunk finder VS V8 to a free talking connection switch V V V and a free selector finder S V6 S When a subscriber, as T is connected through a switch, as S and its associated trunk finder, as VS to a free selector finder, as IVS, the selector finder S commences operating and hunts for a free trunk, as t which is connected by another trunk finder, as VS to a free switch, as S The calling subscriber then sets the second switch S onto the lines of the wanted subscriber, as T The talking connection switch V of the trunk t then sets itself onto the wanted line T Meanwhile the talking connection switch V sets itself onto the calling line also. When the two talking connection switches V V have set themselves onto the wanted and calling line respectively the switches S S are thrown out of the connection and a talking connection for the two subscribers, which extends from T through V 6, W 8 25 V to T, is maintained until the conversation is concluded. The switches S S after they are thrown out of the connection, are immediately available for other connections.

The operations that occur in the various switches S, VS, IVS, V of Fig. l in establishing a connection will now be explained in detail with reference to Figs. 2, 3 and at. In these figures all the details of one single switch only of each kind are shown, because all switches of a kind have similar circuit arrangements. A coherent diagram of the circuits will be obtained if the Figs. 2, 3 and 4 are placed biside each other.

The switches S S perform several functions. Firstly, they connect the calling subscriber to disengaged trunks (through their associated trunk finders VS) secondly, they select the line of a wanted subscriber and cause a talking connection switch V to set itself onto the wanted line. The switches S, 3*, on account of the variety of functions they perform, may be called compound switches.

The mode of operation and signifi-ance of all the other parts shown in the figures will be understood from the following description of the circuits and of the effects to which these circuits give rise.

Let it be assumed that the subscriber T wishes to establish a connection with the subscriber No. 23.

On the calling subscriber lifting his receiver from the hook in the ordinary way, a current flows from the earth through a group relay GR to which all the subscribers of the group to which T belongs are con nected, and through the branch wire l. of the bus bar 2, contact 3 of the cut off relay 4, line 5, T ,,6, contacts 7, resistance 8 to the negative pole of the battery. The groin?) relay GR attracts its armature 9 and this brushes past the Contact spring 10 causing a momentary contact between the springs 10 and 11. ,Vhen the armature 9 subsequently falls back it again brushes past the Contact spring 10. But this time the spring 10 is moved further away from the. contact 11 so that no closure of the contact 10, ll takes place.

It will be assumed that at the monrnt the subscriber T calls, the compound switch S is engaged. In such cases, for re: sons that will appear from the detailed description of the compound switch S either the relay 12, which corresponds to the relay 1-4; of the compound switch S will be energized, 01' the oil normal switch 15, which corresponds to th' o ff normal switch 16 of the compound switch S, will be in its off normal position. The former will be the .case if the compound switch S has just been taken into use for the purpose of establishing a connection with a wanted subscriber, and the latter will be the cas: if the coin pound switch S has been taken into use for the purpose of connecting to a calling line, or it the switch, after having been seized for the purpose of establishing a connection with a wanted line, has been moved out of its normal position.

Assume that the off normal switch of the compound switch S has been brought into its off-normal position. The contact 17 will then be closed and on the momentary closure of the contact 10, 11 a current will flow from earth through 11, 10, 19, 18, 2'0, 17, 21, 24, 25, driving magnet M of the compound switch S 26, 27 to the negative pole. The driving magnet is then energized and in attracting its armature it tensions a draught spring in a known manner. As soon as the current impulse caused by the momentary closure of the contact 10, 11 to flow through the magnet M ceasis, the tensioned spring of the magnet M pulls the sets of brushes or wipers a 6 0 d 6 and a 6 0 d 6 of the compound switch S out of its normal position and these sets of wipers are then caused to touch sets of contacts that are associated with different subscribers of the particular group of subscribersi As soon as the sets of wipers of the switch S leave their normal position the oil normal switch 16 goes into its off normal position, whereby a contact 28 is closed. This causes the interrupter 29 to be connected to the conductor 30 and the driving magnet M now receives current impulses which flow from the positive pole through 29, 28, 36, 25, M, 26, 27 to the negative pole of the battery. The sets of wipers of the compound switch S are now caused to brush past the said contact sets until the wiper cl of one of the sets of wipers touches a contact connected with the positive pole, as for instance until the brush (Z meets the contact 31 which is connected through 7, 6, t 5, 3, GR with the. positive pole or earth. The relay 32 will then be energized by a current which flows from the negative pole through 33, 34, 35, 36, coil 37, contact 38, ( l 39, 7, 6, 5, 3, 1, GR to earth. The relay 32 attracts its armature and in so doing closes the contact 39 and the contacts 40, 41, 42 and 43, whilst it opins the contacts 35, 38 and 26. By opening the contact 26 the relay 32 opens the circuit of the driving magnet M so that the sets of wipers are stopped moving. The opening of the contact results in the battery lead to the energizing windings 37 and of the test relays 32 and 45 being cut oft. Hence it is never possible for more than one test relay 32 or 45 to be energized at the same moment or at one time. The opening of the contact 38 results in the current flowing through the energizing winding 37 being interrupted after a locking circuit in cluding the winding 46 has been closed by the contact 39, The said locking circuit e1:- t-ends from the negative pole through the contact 47, 49, 46, 39, 0, cut oil relay 4 to earth.

The cut oft relay 4 is also energized and opens its contacts 3 and 7, whilst it closes the contacts 49 and 50. The resistance of the winding 37 or' the test relay 32 is such that it lowers the potential on the private normal leading to the compound switches or connectors to such an extent that the calling subscribers line tests busy when other subscribers attempt to establish a connection with the busy calling line. The closure or the contact 41 results in a relay being energized in a circuit which extends from the negative pole through 41, 53, 52, to the positive pole. The relay closes the contacts 55, 56 whilst'it opens the contacts 34, and By closing its contact the relay 52 includes itself in a circuit that depends on the contact 53 of the otf normal switch 16. By the opening oi the con tact the battery lead through the contacts 33 and 34 to the test relays and 45 is cut oil so that, when the sets of wipers of the compound switch are subsequently i nored round until they are re-, stored to normal the said relays will be prevented from being energized in case the wipers d, (P brush over earthed contacts. A. renewed energization of a test relay 32 or 45 can only take place after the sets of wipers have returnedto their normal poi-iitions, because the opening of the con tact 58 of the oft normal. switch, the int ruption of the circuit (positive pole, 58,

52, 4-6, 33, negative pole) which energizes the relay and closure or the battery lead from the neg tive pole through 33, 34 and the contacts c-ii, 36 to the enei izing windings 37 and 44 will only take place after the wipers have been restored to their normal positi The closure of the contacts 42, of the test relay 32 and the simultaneous closure of the contacts 49, results in the ener tion of the starting relay 59 of the selector finder VFS by a circuit which extends from the earth through the lower winding, of the relay 59, contact 61, 62, 63, wiper 64 of the trunk finder VS, which will have been set onto the trunk belonging to the talking connection switch V in a manner hereinafter described, contact 43, b 50, 5,'T 6, 49, a 42, 65, 66, 67, 63, upper winding of the relay to the negat' e pole. The relay is thus energ d and closes the contacts 69, 70, 71'. The closure of the contact 69 results in the energization of the driving magnet M of the selector finder SW by a circuit which extends from the positive pole through 230, ll. 72 to the negative pole. The driving magnet M now moves the Wipers a 7)", c of the selector finder TVS and this movement continues until the wiper (7, which is connected to ltili the stopping relay 73, strikes a conductor 7- which belongs to a trunk that is connected by a trunk finder to a disengaged compound switch. The conductor 7% corresponds to the conductor 74: which leads to the trunk of the talking connection switch V and all the trunks an d the parts associated therewith have their circuits arranged in the same way, the functions which take place in setting the selector finder TVS onto the trunk 74, 75, 76 may be explained on the assumption that the conductor 74 is the one that has been seized by the selector finder S Connected to the trunk that has been found and seized by the selector finder WS will be a compound switch (through a trunk finder VS) which is in its normal position. Since the circuits of the compound switches are all arranged in the same way, it may be assumed for the moment, that S is the compound switch that is connected to the trunk that has been seized. The stopping relay 73 is energized when its brush strikes upon a trunk that is connected through a trunk finder to a compound switch that is in its normal position by a current which flows from the positive pole through 69, 73, c, conductor 74V or 7a, 75, 76, 77, 78, contact 79, relay 14 of the idle compound switch, resistance contact 80 to the negative pole. The relays 73 and 1% are energized. The relay 73 opens the circuit of the driving magnet M- at 72, whilst the relay opens the contacts 33, 25, 79 and 21 and closes the contacts 82, 80, 81, 23, 22, s3, s4 and s5. closure of the contact 22 the starting wire 19, 87 leading from the group relay GB is connected to the prolongation 88 of the starting wire that leads to the next compound switch so that a call from a further subscriber would result in the starting of the next compound switch.

By the opening of the contact 33 the lower windings of the test relays 32 and of the compound switch are disconnected from the battery so that these relays cannot be energized if the wipers d strike upon earthed test contacts. By the opening of the contact 25 and the closure of the contact 82 a new circuit is prepared for the driving magnet M of the compound switch which is to be set onto the wanted line in the manner of the type of switch, which, in known automatic systems, is named a connector. The circuit that has thus been prepared for the driving magnet M is controlled by the dial impulse wire 89. By the closure of the contact and the contact 23 a locking circuit for the relay 14 is closed which extends from the negative pole through 80, 14, 23, 57 to the positive pole. The closure of the contact 81 results in the closure of a circuit extending from the positive pole through 81, 90, 91, 92, relay 93, 94K, 95 to the negative By the pole in which the relay 93 is energized so as to close the contacts 96, 97, 98, 99, 197 whilst opening the contacts 100, 61, 60, 92 and 75. By the opening of the contacts 75 and 92 and the simultaneous closure of the contact 97 a new circuit for the stopping relay 73 is closed which extends from the positive pole through 73, c, 74:, 97, 93, 94, 95 to the negative pole. The parts 69, 73, c and the .parts 7%, 97, 93, 94, 95 are, of course, located in two difiercnt selector-or connector-finders, the parts 69, 73, 0 being located in the con nector finder to whose trunk the calling subscriber connected, whilst the parts 7a, 97, 93, 94-, 95 are located in the trunk that is connected through a trunk finder with an idle compound switch.

It must now be pointed out that the relay 59 which was energized in the manner already described by a flow of current through the calling subscribers instrument did not only start the operation of the associated connector finder S- but also the operation of the associated talking connection switch V The driving magnet M of the talking connection switch V was energized by a current which flowed from the negative pole through 70, 101, M 102 to earth. The driving magnet M operates to move the wipers of a", 5*, 0*, a e and this motion continues until the wipers reach the contact set of the calling subscriber T A current then flows from the positive pole through 40, wiper e identifying wiper e70, identifying wiper a 106, winding 105 of the identifying relay, contact 107, identifying wire 10S, identifying wiper 109 to the negative pole. The identifying relay is energized and opens the circuit of the driving magnet M at the contact 102 so that the wipers stop on the line ta, tb of the calling subscriber. By closing its contact 109 the identifying relay closes a locking circuit for itself which extends from the positive pole through the cut- elf relay 4, 51, 0, 109, 110, 111, 112, 94, 95 to the negative pole. By its contacts and 116 the identifying relay closes a dialling circuit which extends from the battery B in the compound switch connected to the trunk with which the connector finder \VS has established connection, through the impulse relay 118, 85, 65, 66, contact 67 of the trunk finder of the trunk with which the connector finder S has established con nection, contact 7 6 of this trunk, wiper a of the connector finder S 119, contact 120 of the connector finder 8 100, 121 (Fig. 3) 123 (Fig. 2) 115, a m, 6, T 5, :56, 12*, 11c, 12l, 125 (Fig. 3), 60 (Fig. 4), 126, release relay 127 to the positive pole of the battery. Before the circuit of the impulse relay 118 which has just been traced was closed through the wipers of the compound switch V another dialling circuit was closed which may be traced as follows: battery B (Fig. 3)

in the compound. switch connected to the trunk with which the connector finder S has established connection impulse relay 118, 85, wire 101, 190, 65, 66, 67, 76, a 119, conductor 66 of the trunk to which the connector finder S belongs which is connected to the calling line, the par-ts 65, 42, a of the compound switch that has set its wipers onto the calling line, 49, 6, T 50, the parts Z2 4-3, 6 1, of the compound switch the wipers of which have been set onto the calling line, or of the associated trunk finder 63, 126, release relay 127 to the positive pole. It will be evident that in a system like the present one in which a calling line 5, 6 is first temporarily connected through a bypass S to a certain trunk or switch VVS and is then connected over another path or switch V to the same switch S the second switch V must be provided with some special means not merely for hunting for a line that in a calling condition but for identifying the particular calling line as a result of whose call it (i. e. the switch V) has been starting operation. In other words a started switch V must not set its wipers onto any calling line but only on the particular calling line whose call has been extended to it.

The means for enabling a switch or line finder V to pick out a particular calling line amongst any number of calling lines comprises the identifying wires @713 e 2', 2' 1'6 108, 104, and the identifying relays I and I. The identifying circuits are arranged in such a manner that a wiper connected to the energizing winding of an identifying relay and traveling over a row of bank contacts can never encounter any line contact during its travel except a line contact belonging to the particular line upon which the wipers are to be stopped.

t will be seen from Fig. 2 that the bank contacts over which the wipers 6 6, of the line finder V travel may be connected to the positive pole of battery through the wires eh, 6/11 the wipers 6 and 6 and the wires 2' and The switch S, can apply battery through 6 only to eic, and the switch S can apply battery through 6 only to @16 The identifying wires 670 and 670 multipled in the banks of the line finders V V etc. but not in the banks of the switches S 8,. All the wires @712 (one only is shown) emanating from the switch S are connected to contacts travelled over by the wiper e, and similar wipers in other finders V etc., whereas all the wires @70 (only one is shown) emanating from the switch S are connected to bank contacts travelled over by the wiper 6 and similar wipers in other finders V etc. Now if only two switches S S be employed it will be evident that only one wire 67.: and only one wire 6,70 can be connected to battery at any certain moment. It will also obvious that current may be made to flow through'the wire elc over the wiper 6, of a certain switch V, or V etc. only, if the wiper 6 of this certain switch only is connected to battery. Similarly current may be made to flow through wire @70 over the wiper c of a second certain switch only, if the wiper e of this second switch only is connected to battery. The function of connecting only the wiper c of one switch or finder V and only the wiper c of another finder V to battery, so that only the wiper c of a certain finder will encounter certain line wire @70 and only the wiper 6 of a certain second finder will encounter a certain line wire ck, is performed by the switches VS V8 Identifying wires 108, 104 which are not multipled in these switches emanate from their contact bank. The wire 108 from switch VS leads to through the top winding of the identifying relay 1, to the identifying wiper 6 and the wire 104: leads from the switch VS through the lower winding of the identifying relay I to the identifying wiper e Thus whether the wiper 6 or 6 of a finder V V is connected to battery or not depends upon whether the finder V V or its corresponding trunk has been seized by the switch V8 or V8 If the switch V is seized by the switch VS the identifying wiper will be connected to negative battery over the top winding of the identifying relay 1,, 108, 109, and 2'6; but if the switch V is seized by the switch VS the other identifying wiper 6 will be connected to negative battery over the bottom winding of the identifying relay 1,, 104, 170,

and 2'6 So if a calling line is extended to the trunk associated with the finder V through the switches S and VS the identifying wire 67:: will be connected to the positive battery pole and the wiper 6 of V will be connected to the negative pole. If at the same time another calling line is extended through the switches S and V8 to the trunk associated with the finder V the identifying wire 670 will be connected to positive battery and identifying wiper c of the finder V will be connected to negative battery, sothe finder V will only be stopped when its wiper e strikes the bank contact of the calling line as a result of whose call it has started travelling, whilst the finder V 2 will only be stopped when its wiper e, the bank of the particular second calling line whose call has caused it to operate.

The description of the operations involved in the connection desired by the calling subscriber T will now be resumed.

If the calling subscriber sends in his selecting impulses before the talking connection switch V has set its wipers onto his line, these impulses will flow over the path that has just been traced. After the talking connection switch has set'its wipers onto the calling line the selecting impulses flow through both of the above traced circuits simultaneously and through the impulse relay 118. hen the relay 118 is energized a relay 128 which was energized by a current from the negative pole through 84, 129, 128 to the positive pole is short circuited by the contact 132. The relay 128 is deenergized, but no effect is caused hereby at this time. The relay 133 is energized, when the relay 118 attracts his armature, by a current whlch flows from the negative pole through 133, 132 to earth and opens the contact 134, whilst it closes the contact 135.

As the calling subscriber wishes to call subscriber No. 23 he sends in the digit 2 and thus causes the interruption of the diallingcircuit. At each interruption the relay 118 lets its armature drop back and at each retraction of the armature a current flows from the negative pole through 8.4, 130, 135, 89, 136 (Fig. 2)., primary magnet ZM to the positive pole. The primary magnet moves the wipers 137, 138 onto the second set of contacts 139, 140.. This set of contacts 15 connected to conductors which lead to the test relay of the particular set of wipers of the compound switch that wipes over the group of contact sets in which the contact set of the wanted subscriber is located. After the calling subscriber has thus selected the tens group of the wanted subscriber a short pause ensues during which the relay 118 keeps its armature attracted. Hereby the relay 128, which, is energized during the interruptions of the dialling circuit by a current that flows from the negative pole through 84, 133, 128 to earth, is shortcircuited and lets its armature drop back. This results in a closure of the contact 141 and in a subsequent interruption of the contact 142, and a current impulse flows from the negative pole through 84, 131, 142, 141, 143, 144, 145, contact146 (Fig. 2) which was closed when the wipers 137 and 138 were moved off their normal positions, relay 147 to the positive pole. The relay 147 is thus energized and closes a lOCkiIlg circuit for itself which extends from the positive pole of the battery through 148, contact 83 to the negative pole. At the same time the relay 147 opens a contact 136 whilst it closes a contact 149 The calling subscriber new sends in the second digit, which, as the line he desires. is No. 23 is 3, so that he causes three interruptions of the dialling circuit. At each interruption a current flows from the negative pole through 84, 130, 135, 89, 149, 82-, magent M, 26, 27 to the negative pole. The sets of wipers of the compound switch are caused to take three rotary steps so that, the set of wipers selected by means of the primary magnet ZM is set onto the contact set 01"? the wanted line number 23. The rotary movement of the sets of wipers G11, 72 0 d, 0 etc. of the compound switch set onto the wanted line results in the associated off normal switch 16 being moved out of its normal position. By this means the changeover circuit which includes the relay 147 is opened at the contact 144, whilst a test circuit is prepared at the contact 145 or a busy tone circuit is prepared at the contact 146. At the same time a locking circuit for the relay 52 of the compound switch is prepared at the contact 58.

After the calling subscriber has caused the wipers of the compound switch to be set onto the wanted subscribers line in the manner described, another pause ensues during which the relay 118 keeps its armature pulled up and causes the relay 128 to deenergize. This results in the closure 01' the contact 152 and in the subsequent opening of the contact 153, and a test current flows from the earth through the cut oil relay of the wanted subscriber, wiper 0 which is set onto the test wire of the wanted subscriber, contact 139 of the tens selector, wiper 137, coil 155 (Fig. 3), contact 153, 152, 145, 138, 140, winding 156 01 the test relay 45 associated with the wiper c conductor 157, contacts 48, 47 to the negative pole. If the wanted subscriber is disengaged the relays 155 and 45 will be energized. The relay 45 closes its contact 158 and thus closes a looking circuit for itself which extends from the negative pole through 47, 48, 157, 156, 148, 0 test wire 01 the wanted subscriber, cut-0t? relay of the wanted subscriber to earth. At the same time the closure of the contact 158 effects the short circuiting of the left winding of the relay 155. .But this relay remains energized by a locking circuit which extends trom the positive pole through its right winding, 159, 83 to the negative pole. On energizing the relay 155 closes a contact 160 and thus establishes a starting circuit for the talking connection switch that is connected to the compound switch that has been set onto the wanted subscribcrs line. This starting circuit extends from the negative pole through 160, 161, 162, 101, driving magnet M 102 to earth. The driving magnet M and the contact 102 of course belong to a talking connection switch which is quite independent of and separate from the talking connection switch that is set onto the calling line. The talking connection switch that is connected to the compound switch which is set onto the wanted line now starts moving and its wipers will only stop when its identi fying relay is energized by one of its identifying wipers 1 1 striking upon an identifying wire corresponding to the particular compound switch just mentioned. It must be pointed out, that each compound switch has a special identifying wire similar to the wire 070 leading to the contacts of the talking connection switches. If it be assumed for instance that the connection between the talking connection switch to be connected Iii to the wanted line and the compound switch that has been set onto the wanted line is es tablished through the trunk finder V8 the lower winding 103 of the relay of the talking connection switch will be connected through the wiper 170 of the trunk finder V5, to the negative battery pole and the identifying re lay of the talking connection switch can only be energized if the identifying wiper c strikes upon the identifying wire which is connected by a wiper a, and a contact 171 of the compound switch S belonging to the trunk finder VS to the positive pole. Such a co-operation of a talking connection. switch with a compound switch 8,, would of course only occur if the compound switch S is not engaged at that particular moment and if the same is connected by its trunk finder to the particular talking connection switch V with which the connector finder W8 has established connection. If there are more thaif two compound switches S S there will be more than two identifying wires 626, 610 leading to the fixed contacts of the talking connection switches V V etc. As has already been pointed out, a special identifying wire leads from each compound switch S 3,, etc. to the talking connection switches V,, V The identifying relay of the particular talking connection switch V which is set onto the wanted line is thus energized through a different identifying wire from the one which leads to the compound switch that is set onto the calling line, this energization taking place through an energizing circuit that leads to the compound switch which has been set onto the wanted line in the manner already described. At the moment when the identifying relay is energized in consequence of its wipers striking upon the line of the wanted subscriber, the starting relay 172 of the trunk finder which belongs to the compound switch that has been set onto the wanted line is energized by a current which flows from the negative pole through. 117, 17 1, contact 175 of the off normal switch 176, wiper 177, 172, to earth. In addition to this the starting relay 172 of the trunk finder which belongs to the switch that has been set onto the calling line is energized by a current which flows as follows: from the negative pole through the contact 117 of the talking connection switch set onto the wanted line, 174:, 178, wiper (L, of the connector-finder S contact 17%) of the off-normal switch 176 of the connector finder WS, which has been moved out of its normal position, wiper 177 of the trunk finder that belongs to the switch which has been set onto the calling line, relay 172 to the positive pole. The two relays 172 of the two trunk finders are thus energized simultaneously and close their contacts 180, 181, whilst opening their contacts 47 and 182. By the closure of the contact 180 circuits are closed in the two trunk finders which extend from the negative pole through the interrupter 188, contacts 180, driving magnets 184 to earth. By this means the wipers of each of the two trunk finders are set in motion and this motion continues until the wipers 185 strike upon conductors 186 which are not connected with the negative pole of the battery. The conductor 186 belonging to each trunk will be connected to the negative pole of the battery if one of the relays 59 or 98 is energized, or in the case of the off normal switch 17 6 being out of its normal position. The conductor 186 of a trunk will also be connected to the negative pole of the battery if some other trunk finder has previously seized it. In such a case the connection between th conductor 186 and the negative pole would be established through the contact 182 and the wiper 185 of the particular trunk finder which had previously seized the trunk. As long as the wipers of a started trunk finder continue striking upon the contact sets of previously seized trunks the relay 17 2 of the hunting trunk finder remains energized by a current which flows from the negative pole of the battery through the conductors 186, wiper 185, contact 181, relay 172 to earth. But as soon as the wiper 185 reaches a con ductor 186 which belongs to a trunk that is notbeing used for conversation and that is not engaged the connection between the negative pol-e and the particular conductor will be missing and the relay 172 will be deenergized. As soon as the armature of the relay 172 falls back it will establish a connect-ion at its contact 182 between the conductor 186 of the free trunk and the negative pole of the battery so that other trunk finders will now no longer be able to stopupon the seized trunk. When the armature of the relay 172 falls back the'contact 180 will be opened, whereby the circuit of the driving magnet 18 1 of the trunk finder is interrupted and the wipers of the trunk finder are stopped.

The operations which occur in setting a trunk finder that b longs to the compound switch set onto the calling line onto a free trunk, and the operations involved in the seizure of a free trunk by the trunk finder belonging to the compound switch which has been set onto the wanted line are preciselv similar.

As soon as the starting relay of a trunk finder is energized the opening of the contact 17 causes the interruption of the locking circuit of the particular test relay 32 or 45 of the associated compound switc In the compound switch which is set on the wanted line a circuit is closed for the driving magnet M which extends from the positive pole through 29, 28, M, 26, 27 to the negative pole. Since the batery leads to the relays 32, 15 etc. is open at the contact 34: no ener gization of the relays 32, etc. take place when the wipers or a compound switch are moved past the contacts of other lines. Hence the driving magnet M remains energized until the wipers are restored. to their normal posit-ion and the off normal switch 16 is restored to normal. hen this has taken place the contact will be opened and the interrupter 22 will be disconnected from the magnet M. At the same time the locking circuit of the relay 52 will be interrupt-ed at the'coutact 58 and the battery lead from the negative pole through 32-), to the test relays 32, 15 will be reestabli. l The relay 52 was energized by a cm which flowed from the negative pole through contact 191, 53, 52, 5 1 to the positive pole.

It must be mentioned that at the moment when the relay 17 2 was energized a contact at the point indicated by the numeral 190 in the conductor leading to the impulse relay 118 was opened and that the current flowing through the impulse relay 118 was thus interrupted. hen this happens this relay causes the relay 133, which was deprived of current by the opening of the contact 84 to be short circuited by the contact 129 so that it opens the contact 135 and closes the contact 1341-. The closure of the contact 134 results in the energization of the release magnet 192 of the tens selector and in its restoration to normal by means of a current which flows from the negative pole through 13%, 193, 192 to the positive pole. When the armature of the relay 133 falls back the locking circuit of relay 1st which extends from the negative pole through 80, 1t, 23, 57 to the positive pole is opened. This is caused by the armature of the relay 133, in falling back, brushing past the contac spring 57 and momentarily opening the contact closed by this spring. This causes the de-energization of the relay 14. By the opening of the contact 83 of the relay 1 1 belonging to the compound switch set onto the wanted line, the locking circuits oi: the relays 155 and 1 17 are opened so that these relays are energized. All the parts of the compound switch, which was set onto the wanted line, will now have been restored to their normal positions.

fit the moment when the relay 17 2 of the truck finder associated with the compound switch that is set onto the calling line is energized, the opening 01 the contact 4:7 of the said trunk finder causes the de-cnergization of the particular test relay 32 belonging to the set of wipers that is set onto the calling line. The contact 26 is then closed and the driving magnet M of the compound switch is energized by a current which flows from the negative pole to the contact 27, 26, M, 25, 28, interrupter 29 to the positive pole of the battery. The driving magnet M now moves the wipers of the compound switch past the fixed contact sets or bank contacts of the compound switch until they are restored to normal, when the circuit of the driving magnet will be interrupted by the restoration of the off normal switch and the opening ot' the contact 28 caused hereby. During the motion of the wipers into their normal position the battery lead to the energizing winding of the test relays 32, 15 is open at the contact 31 so that no stoppage of the compound switch is liable to takeplace by the energization of a test relay. The battery lead to the test relays is only re-connected through the contacts 32, of the test relays due to the opening at contact 58 of the locking circuit of relay 52 extending through 51 and 58, when the compound switch is restored to its normal position.

It will appear from the above description that as soon as a talking connection switch has set its wipers onto the calling line and another talking connection switch has set its wipers onto the wanted line the two com pound s itches which took part in the establishing of the connection are immediately restored to their normal positions and become available for other connections. The arrangement could also be such that in cases where a talking connection switch sets its wipers onto the calling line before the selecting impulses are passed on to the compound switch that is to be set onto the wanted line, the compound switch which has made connection with a calling line is thrown out of the connection before the second compound switch is set onto the wanted line. In such cases the selecting impulses or some of them might flow over the wipers of the talking connection switch set onto the calling line.

When the relay 172 of a trunk finder is energized in the manner described above it is kept energized by a current that flows from the earth through 172, 181, 185, 186 and thence either over the contact 71 or 90, or through the wiper of another trunk finder and through the relay contact 182 of this other trunk finder to the negative pole. This current will, as has already been said, flow through the relay 172 until the wiper 185 01? the trunk finder strikes upon a conductor 186 which is not connected to the negative pole of the battery, i. e. a conductor 186 which belongs to a trunk which is neither being used for conversation nor has been seized by another trunk finder. The relay 172 then allows its armature to fall back and by opening the contact 180 deenergizes the driving magnet 184. The wipers ot the trunk finder will then connect the associated compound switch with a free, unused trunk which may now beused for another talking connection.

After the compound switches have been thrown out of the connection the talking subscriber will be supplied with current which flows from the positive pole through the relay 127 (Fig. 4), 126, 60, conductor 125, 1'1, 124, 116, I), H), 5, T 6, ta, (1., 115, 123, conductor 121, 100, 120, 110, a contact 76 of the trunk which is connected by its associated talking connection switch to the wanted line, contact 67 this line, 196, 197, retardation coil 198, contact 199 (Fig. 2) to earth 200. The earth 200 was connected through the retardation coil 198 only at the moment when the talking connection switch set its wipers onto the wanted line.

At the moment when the talking connection switch set its wipers onto the wanted line a circuit was closed at the contact 113 for the ringing relay 114 which extends from the positive pole through 113, 114, 201, interrupter 102 to the negative pole. The relay 114 now intermittently closes the contacts 203, 204 and at each closure of these contacts a ringing current is sent from the ringing current generator LM through 203, 115, a ta, 6, T 5, tb, Z), 116, 204 back to the ringing current generator. When the called subscriber lifts his receiver from the hook and the contacts 123, 124 are closed, a current will flow from the earth through the upper winding of the relay 210, contact 99, conductor 121, 123, 115, a, ta, 6, T 5, tb, b, 11.6, 124, 125, 98, contact 211, 62, contact 75 onto which the connector finder has set its wipers that is associated with the talking connection switch that has established connection to the calling line, wiper b of the connector finder, contact 213, relay 212 of a connector tinder to the negative pole. The relay 210 associated with the trunk connected to the called subscriber and the relay 212 associated with the trunk connected to the calling subscriber are energized simultaneously. The relay 212 establishes a new transmitter feed circuit for the calling subscriber which extends from the negative pole through 212, 215, 120, 100, 121 3),a5",123 (Fig. 2), 115, at, m, 6, T 5, 2%), b, 116, 124, b, 125 (Fig. 3), 60, (Fig. 4), 126 and through 127' to the positive pole. At its contact 213 the relay 212 opens the current path leading through the wiper b to the called subscriber. A. new current path is now closed for this subscriber through the relay 210 which may be traced as follows: from the earth in the trunk which is connected to the called subscriber through the upper winding of the relay 210, contact 99, 121 (Fig. 3), a, (Fig. 2), 123, 115, a, m, 6, 5, 25?), b, 116, 124, b, 125 (Flg. 3), 98, (Fig. 4), 217, lower winding of the relay 210 to the negative pole. By opening the contact 201 the relay 210 interrupts the circuit of the ringing relay 114 and the calling subscriber will now have a talking connection with the called subscriber which may be traced as follows: from the calling subscriber T line 6, ta, wiper a of the talking connection switch set onto the calling line, 115, 123, a, 121 (Fig. 3), 100 (Fig. 4), 120, condenser 220, wiper at, contact 76 of the trunk which is connected by its associated talking connection switch to the called subscribers line, 67, condenser 218 (Fig. 3), contact 115 (Fig. 2) of the talking connection switch set onto the called line, wiper a of this talking connection switch, con-' ductor m of the called subscribers line, conductor 6, called subscribers station, 5, conductor th of the called line, b, 116, 124,.condenser 219 (Fig. 3), contact 62 (Fig. 4), contact 75, wiper b of the connector finder associated with the talking connection switch set onto the calling subscribers line, contact 216, condenser 222, 126, 60, 125 (Fig. 3), b, 124. (Fig. 2), contact 116 of the talking connection switch set onto. the calling line b of this talking connection switch, conductor 6?) of the calling line, conductor 5 back to the calling subscribers instrument T \Vhen the calledsubscriber at the end of the conversation replaces his receiver on the hook in the ordinary way the relay 210 associated with thetrunk connected to the called line is de-energized. When the arm ature of the relay 210 falls back the contact 94 is momentarily opened and the locking circuit of the relay 93 is thus interrupted. It will be remembered that this locking circuit extends from the negative pole through the contact 95 of the trunk that was connected to the called line and through the contact 94, relay 93, contact 97, 74', test contact, wiper of the connector finder associated with the talking connection switch set onto the calling line, test relay 73 to the positive pole.

The momentary opening of the contact 94 also deprives the winding 105 of the identifying relay of the talking connection switch set onto the called line of its connection with the negative pole through the contact 111, so that the said identifying relay is de-energized. At the same time the cutoff relay 4 of the called subscriber which was energized by a circuit which extended from the earth through 4, 51, 0, 109, upper winding of the identifying relay, contact 111, conductor 112, contact 94, 95 to the negative pole, is de-energized. All the parts belonging to the trunk connected to the called subscriber have now been restored to normal.

When the calling subscriber replaces his receiver the relays 127 and 212 of the trunk connected to the calling line are de-energized. On the de-energization of the relay 212 which was energized when the called subscriber responded, the armature 225 in brushing past the contact 223, caused the negative pole of the battery to the directly connected to the wiper c of the talking connection switch set onto the calling line. By

of the talking connection switch setonto the calling line is opened so that this relay and also the cut-off relay 4 and the meter Z are tie-energized. it the same time the driving magnet of the connector fnder lVS is encrgized by a circuit extendin from the earth through 102. off normal contact 227, driving magnet m 72. to the negative pole. When theconnector i'inder is r tored to its normal. position the contact and hence the circuit of the magnet M is opened so that the wipers of, 7f", c are stopped. All parts of the switches used for the connection have now been restored to normal. The talking connection switches have no definite normal position. The connector finders can also be arranged so as to have no definite normal. position.

To provide for cases in which a wanted line is found ei'igaged when a compound switch is set onto the same a busy tone device "2:30 is furnished. if the wanted line is engaged the relay does not get suiticient current to be energized and the busy tone device is connected through the contacts 2251, 1&6, 154C to the dialling circuit leading to the calling subscriber. The calling subscriber then receives a busy signal which causes him to replace his receiver. This causes the de-energization of the impulse relay 118 in the compound switch set onto the called line and of the relay 127 associated with the trunk connected to the calling subscriber, and results in the restoration of the used apparatus to normal.

In the above described form of the invention each talking connection switch. is connected to a simple connector finder. In larger exchanges group selectors could be provided in place of the connector finders which perform their operations before the compound switches carried out their selecting function. Another modification of the invention may comprise, instead of the compound switches which operate either to conncct a calling subscriber to an unseized line or to select a called subscriber, two special sets of switching apparatus of which the one set operates to connect the calling subscriber to unseized trunks whilst the other set is only used for selecting the wanted subscribers line.

A layout diagram of this modification is giren in Fig. 6. The swit hes 8, s represent the switching devices by which calling subscribers are connected to free trunks 19,, Z9 Z9 and the switches LlV LVV represent the apparatus which are used only for selecting wanted subscribers lines and will therefore be called wanted line selectors. The switches s 8 are preferably constructed in the form of quick-acting switching apparatus such as relays or quick-acting line finders, and are connected through trunk finders VS VS vith free unseized trunk lines Zg Z9 Z9 leading to group selectors. Each wanted line selector LVV Llv is always kept in connection with a free trunk Z Z Z Z. by its associated finder VS VS in the same way as the transitorily engaged switches of Figs. l-at. The trunks Z Z Z 1,, are connected by intermediate switches ZV ZV ZV,,, ZV with. other free trunks r Zg. Z9 The trunks Z Z Z 5 are connected to the subscribers lines by talking connection switches V V V V lVhen a subscriber T calls he is connected by a quick-acting finder (such as S and its associated trunk finder V with a free trunk such as Zg By means of dialling impulses the calling subscriber then sets the group selector lrlV onto the wanted group, say the group to which the trunks f f f 7'. lead: The group selector Gril then hunts for a free trunk which has been seized by a trunk tinder, say the finder VS It will be supposed that this is the trunk Z The calling subscriber now sends in further dialling impulses by which the wanted line selector is set onto the desired line, say T The switch V associated with the trunk Z, is now caused to set its wipers onto the line of the wanted subscribers T which is identi fied by the wanted line selectors LVV \Vhen the calling subscriber T was connected through the switches S and VS to the trunk lg a free intermediate switch, say ZV associated with a trunk that had not been seized by a finder VS V8 was caused by suitable means to set its wipers onto the trunk lg] whereupon the switch V associated with the trunk Z establishes a connection with the line of the calling subscriber T lVhen the switch V has set its wipers onto the line of the wanted subscriber T, a talking connection is established which extends from T, through 4) l ZV Zg GlV f Z V to the wanted subscriber T As soon as this connection is established the switches S LlV are disconnected from the talking connection and connected by their associated trunk finders S VS to other free and unseized trunks.

For cases in which the calling and called subsiribers are both in the same group the arrangement may be such that the group selector, when set onto the wanted group (which in this case will also be the group in which the calling subscriber is located),

lot,

effects a special switching function by which the talking connection instead of being established through the bank contacts leading to the various groups is confined to a local path within the group in which the call has originated. This local path may be established by causing the two intermediate switches say ZV ZV. (associated with the switches V V whose wipers are set onto the calling and, called lines respectively) to both set themselves onto a free multiple wire.

lVith switches of the kind described with reference to Fig. 6 a semi-automatic system could be built in which each. switching apparatus which is used only for connecting the calling subscribers with unseized trunks is associated with a dial switch or selecting impulse sender for controlling the selectors.

The compound switches which perform a double function are advantageous in large exchanges in that the efiiciency of the exchange is increased in cases where the calls are chiefly either outgoing calls or incoming calls. I

Another form of the invention is shown in Fig. 5. In this figure Vl, Vl-V2, V2 V3, V3 -V l, V41 are pairs of talking connection switches which are adapted to establish connections between any two subscribers T T etc. S S are line finders or switches which, when a subscriber makes a call, set their wipers onto the called line, and W ll are selectors which operate toselect the wanted line. V r VS are trunk finders which connect their pairs of switches S or S respectively to unseized pairs of talking connection switches. Hence each pair of switches SlV is always connected to afree pair of talking connection switches.

Assuming that a subscriber T calls with the intention of establishing a connection with a subscriber T hen the subscriber T makes the call a free switch S sets its. wipers onto the calling line- C Then the selector lV associated with the switch S is subsequently set onto the wanted line T by the digits sent in by the calling subscriber the talking connection switch V3, which is connected by the trunk finder VS to the line finder S sets its wipers onto the calling line. After the selector has been set onto the wanted line C the talking connection switch V8 associated with the talking connection switch V3 is caused to set its wipers onto the wanted line. hen the talking con nection switch V8 has set its wipers onto the selected line, the trunk finder VS connects the pair of switches S with some other pair of free talking connection switches and the selector W is caused to return to normal.

The switching arrangement shown in Fig. 5 has the advantage that separate identifying wires can be used for the talking connection switches that co-operate with the line finders S S and for the talking connection switches which co-operate with the selectors W W. The talking connection switches V1, V2, V3, V4 in such an arrangement would only need to have as many identifying wires as there are line finders S S In a similar manner the talking connection switches V1 V2 V3 V4 would only require as many identifying wires as selectors W are provided in the particular group.

W hen compound switches of the kind illustrated in Figs. 1 to t are used, the talking connection switches have to be provided with as many identifying wires as compound switches are furnished. In. an exchange in which two connections are to be set up simultaneously, that is where four compound switches have to be provided, four identifying wires would have to be provided for the talking connection switches.

In smaller exchanges a switching arrangement of the kind shown in Fig. 5 offers the additional advantage that the selector finders VVS (Fig. 1) can be dispensed with. Besides in small exchanges where not more than one call. is put through at the same instant one single identifying wire would be sutficient for the talking connection switches V1, V2, V3, V4 and another single identifying wire would be sufficient for the talking connection switches V1 V2 V3 Va It must also be mentioned that the compound switches may be provided with sepa rate test relays for setting the switch onto a calling line and for testing a wanted line.

Another detail in connection with the starting of the compound switches S S when a subscriber calls will now be described:

In the preceding description an explana tion was given of the manner in which a group relayGR is energized when a subscriber calls and it was shown that the armature 9, in brushing past the spring 10, sends a starting impulse to the next compound switch in the group through the wire 19. The armature 9 can only send a further impulse over the wire 19 after it has fallen back. Now it may happen that a second subscriber calls before a compound switch has set its wipers onto the line of the subscriber who first called. The result of this would be that the group relay GR would have no opportunity to fall back in the period between the first and second call and as the group relay would be kept energized by thecurrent flowing of the line of the second subscriber, this second subscriber would wait in vain to be put through because no second eompound switch would be started. To prevent such cases from happening the cut off relay of each subscriber could be provided with a contact, which on the cut off relay being energized, closes the circuit oi a relay which is common to the group and which. in any case momentarily opens the circuit oi the group relay or disconnects it from the bus bar 2. By this means, in cases in which a second subscriber is waiting to be putthrough whilst a compound switch is setting its wipers onto a line, the armature 9 of the group relay will be caused to retract. It would be immediately de-energized by the current flowing through GR and the line of the second subscriber, and in so doing would send a starting current impulse over the wire 19.

I claim:

1. In a telephone system, calling lines, talking conductors to which the lines are adapted to be extended, transitorily-engaged two-way call-advancing devices, means for simultaneously advancing a pinrality of calls from a plurality of said lines through said call-advancing devices to a plurality of said conductors, and connecting devices for interconnecting talking conductors to which calls have been advanced and the lines from which the calls have proceeded.

In a telephone system, calling means, talking conductors to which the said lines are adapted to be extended, transitorily-engaged two-way call-advancing devices, means for simultaneously advancing a plurality of calls from a plurality of the said lines through said call-advan'cing devices to a plurality of said conductors, and connecting devices for interconnectlng each talking conductor to which a call had been advanced only with that particular line from which the call has proceeded.

3. In a telephone system, calling lines, wanted lines, common means for electrically marking both calling and wanted lines, and connecting devices separate from the marking devices for interconnecting marked calling and wanted lines.

14:. In a telephone system, calling lines, numerical impulse transmitters associated therewith, wanted lines, talking trunks for effecting talking connections between the calling and wanted lines, selecting devices for selecting wanted lines, transitorily engaged two-way trunks for conducting numerical impulses from calling lines into a plurality of selecting devices simultaneously, means for temporarily associating each tran sitorily engaged trunk with a talking trunk, and means for connecting each talking trunk only with the same calling line to which the transitorily engaged trunk with which it is temporarily associated is connected.

5. In a telephone system, wanted lines, two-way swit hes with bank contacts associated with the said wanted lines, calling means, call-advancing means for advancing calls to the said switches, wipers in the switches adapted to travel over the said bank contacts, a battery, means for connecting said wipers to battery, and means by which in cases of several calls being advanced to the said switches a wiper connected to battery can enounter only one certain bank contact that is also connected to battery.

(5. In a telephone system, calling lines, wanted lines, a group of talking-connection line finders, a group oi? talking connection switches with bank contacts and coo ierating wipers, and transitorily engaged two-way switching apparatus for setting the wipers of line finders onto calling line, and the wipers of the said talking connection switches onto wanted lines.

7. In a telephone system, calling lines, impulse transmitters, wanted lines, transitorily engaged numerical switches with bank contacts connected to the wanted lines, circuit arrangements in the numerical switches for receiving a primary and a secondary series of numerical impulses from the impulse transmitters, wipers in numerical switches adapted to be set onto wanted lines in response to the said series of impulses, and means for changing the manner of opera tion of the switches so that their wipers execute an automatic hunting operation to ind a calling line in any of the contact rows in its bank.

8. In a telephone system, lines, calling means associated with the said lines, primary switching apparatus for establishing a plurality of simultaneous talking connections between pairs of the said lines, and separate two-way transitorily engaged secondary switching apparatus for simultaneously advancing a plurality of calls from calling lines and controlling the primary switching apparatus when establishing connections, the primary switching apparatus comprising talking trunlcr and switching devices for directly connecting these talking trunks to (ailing lines, and the secondary switching apparatus comprising call-advancing trunks and switching ap paratus for directly connecting these trunks also to calling lines.

9. In a telephone system, lines, calling means associated with the said lines, switching apparatus forestablishing a plurality of simultaneous talking connections between pairs of the said lines, and separate two-way transitorily engaged secondary switching apparatus for simultaneously advancing a plurality of calls from calling lines and mutrolling the primary switching apparatus when establishing connections, bells associated with the lines, and ringing circuits confined to the primary switching apparatus for operating the said bells.

10. In a telephone system, a plurality cf calling and wanted lines, a plurality of contacts in whichsaid lines terminate, a trunk, means for electrically identifying a certain one of said contacts as a calling'or wanted contact, and means tor connecting said trunk with the electrically identified con tact.

11. In a telephone system, a plurality oi calling and wanted lines, a plurality of contacts in which said lines terminate, a trunk, numerically and nonnumerically operable means for electrically identifying the .contact of a wanted line, and means for connecting said trunk to an electrically identified contact.

12. In a telephone system, a plurality of calling and wanted lines, a plurality of con tacts in which said lines terminate, a switch, another switch, means for operating said switch in accordance with the designation of a calling or wanted line for selecting the contact of the wanted line; means operated thereupon tt'or actuating said other switch to connect the calling line with. the selected contact, and an identifying circuit closed by said other switch for identifying the calling line.

13. In a telephone system, a plurality oi calling and wanted lines, a plurality of contacts in which said lines terminate, a switch, another switch, means for operating said switch in accordance with the designation oi a calling or wanted line for electrically identifying the contact in which the line terminates and temporarily associating the line therewith, means operative thereupon for actuating the other switch to seize the electrically designated contact and permanently connect the line therewith, and means operative thereupon for releasing said switch.

1 1-. In a telephone system, a plurality of calling and wanted lines, a connector switch having bank contacts connected to said lines, a calhng and wanted line marking switch having bank contacts connected to certain bank contacts of said connector, means for operating said line marking switch in accordance with the designation of the line to mark the contact of the line, and means for operating said connector toseize a marked bank contact.

15. In a telephone system, a plurality of calling and wanted lines, a plurality of stationary contacts in which said lines term1nate, a set of movable contacts, means, for op-.

eratin said movablecontacts electrically to identity a certain, stationary contact of a calling or wanted line, other sets of movablev contacts, andmeans for operating the other sets of movable contacts vfor successlvely engagingsaid stationary contacts and tonal-- lowing only a, certain set to stop at the ele ctrically identifiedcontact. V

16. In a telephone system, a plurality of calling and wanted lines, contacts in which said lines terminate, twoswitches, means operable upon the initiation of a call on one of said lines for actuating one of said switches electrically to identity the contact of the calling line by a certain potential, and means for operating the other switch to seize the electrically identified contact.

17. I11 a telephone system, a group of calling lines, a trunk line, contact sets in which said calling lines terminate, means operative upon the initiation or completion of a call for electrically identifying a contact set by a certain potential, and means operative thereupon for connecting said trunk line to said contact set.

18. In a telephone system, calling and wanted lines, a plurality of trunk lines, a contact in which a said line terminates, means operative upon the initiation or completion of a call for electrically identifying a contact by applying a certain potential thereto, means for preselecting a trunk line for use, and means for connecting the preselected trunk with the electrically identified contact.

19. I11 a telephone system, a plurality of calling and wanted lines, a plurality of trunk lines, a switch, means operative upon the initiation or completion of a call for actuating said switch to select a calling or wanted line respectively, a second switch connected with said switch, means for operating said second switch to select an idle trunk line, a third switch, and means for operating said third switch to connect the trunk line selected by the second switch with a calling line selected by the first switch.

20. In a telephone system, a plurality of calling and wanted lines, a' plurality of trunk lines, a first switch, means operative upon the initiation or completion of a call for actuating said switch to select a calling or wanted line respectively, a second switch connected with said first sivitch,jmeans for operating said second switch to select an idle trunk line, a third switch, meanstor operating said third switch to connect the trunk line selected by the second switch with a calling line selected by the first switch, and means operative thereupon for actuating said second switch to select another idle trunk line. I

21. In atelephone system, a plurality of calling and wanted'lines, a plurality of trunk lines, a first switch, means operative upon the initiation or completion of a call for actuating said switch to select a calling or wanted line respectively, a second switch connected with said first switch, means for operating said second switch to select an idle trunkline, 'a' third switch, means toroperating "said third switch, to connect the trunk line selected by the second switch with the calling line selected by the first switch, and means operative thereupon for restoring said first switch: and for operating said second switch to select another idle trunk line.

22. In a telephone system, calling and wanted lines, a called line, a trunk line leading towards said called line, a switch, a contact in said switch in which said trunk line terminates, a second contact in said switch in which the calling line terminates, a third contact in said switch, means operative upon the initiation or completion of a call for connecting said third contact with the contact of the calling or wanted line respectively, and means operative thereupon for extending the calling line to said trunk through said first mentioned contact.

23. In a telephone system, calling and wanted lines, link circuits, connecting switches, two-way marking switches for marking both calling and wanted lines, and means for establishing a connection between a said trunk and a marked calling or wanted line through a said connecting switch.

24. In a telephone system, calling and wanted lines, link circuits, two-way connecting switches, two-way marking switches for marking both calling and wanted lines, and means for establishing a connection between a said trunk and a marked calling or wanted line through a said connecting switch. c

25. In a telephone system line, numercial switches, line finders with a plurality of test brushes which simultaneously test different lines, means for extending only one said line at a time through line finder to a numerical switch, and selecting impulse transmitters associated with said lines for sendin selecting impulses through said line findersto the numerical switches.

26. The combination with impulse transmitters in a telephone system having calling and wanted lines of a two-way switch com prising passive contacts connected to said lines, groups of active contacts, means for setting an active contact onto a passive contact when the line connected to it makes a call, and means responsive to an impulse transmitter for selecting any said group of active contacts.

27. The combination with impulse transmitter's in a telephone system having calling and wanted lines, of a two-way switch comprising bank contacts connected to said lines, sets of wipers that co-e, rate with tlifie rent groups of said bani contacts, means for setting a set of onto a bank wneu th'e to it a call," means ms'ponsive to an impulse transmitter for selecting any of said sets of wipers and setting them onto a said line.

28. In a telephone system, lines, talking trunks, finders with movable contacts connected to said trunks and fixed contacts connected to said lines onto which the movable contacts can be set, a switching device for selecting a tree trunk, numerical switches accessible through said trunks, and unimotional switching apparatus for connecting a calling line through the switching device to a free trunk and for starting the operation of the movable contacts of a finder of this trunk independently of said numerical switches.

29. In a telephone system, lines, talking trunks, finders with movable contacts con nected to said trunks and fixed contacts connected to said lines onto which. the movable contacts can be set, a switching device for selecting a free trunk, uni-motional apparatus for connecting a calling line through the switching device to a tree trunk and for starting the operation of the movable contacts of the finder of this trunk, and a numerical switch connected to a said trunk and adapted to receive numerical impulses from a calling line during the operation of said movable contacts.

30. In a telephone system, subscribers lines, link circuits, two-way connecting devices for connecting a calling line to a link circuit or for connecting the link circuit to a called line, a switching device for select ing a free link circuit, numerical switches accessible through said link circuit, and. switchingapparatus for connecting a calling line through the switching device to a free link circuit and for staring the operation of a said connecting device inde pendently of said numerical switches.

31. In a telephone system, subscribers lines, link circuits, connecting devices both for connecting calling lines to the link circuits and for connecting link circuits to wanted lines,'a switching device for selecting a free link circuit, switching apparatus for connecting a calling line through a switching device to a free link circuit and for starting the operation of a said connecting device, and numerical switches connected to said link circuits and adapted to receive numerical impulses from calling lines during the operation of said connecting de vlces.

32. In a telephone system, subscribers lines, link circuits, connecting devices both for connecting calling lines to link circuits and for connecting link circuits to wanted lines, numerical. switching apparatus for.

marking wanted lines, means for associatin a f -ree niunerical switching apparatus witfi a link ;.circuit, and means tor preventing a connecting device associated with a numeri cal switching apparatus from connecting to any Wanted line excepting the one marked a link circuit and means for preventing a by said associated numerical switching apconnecting device associated with a said paratus. switching apparatus from connecting to any 33. In a telephone system, subscribers wanted line or calling line excepting the one lines, link circuits, connecting circuits both marked by said associated switching ap- 15 for connecting calling lines tolink circuits p l'atus.

and for connecting link circuits to wanted In testimony whereof I have signed this lines, switching apparatus for marking both specification.

calling and wanted lines, means for as- V g g 10 sociating a free switching apparatus with FRITZ ALDENDORFF.

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