US2072234A - Telephone metering system - Google Patents

Description

March 2, 1937. E. WOCHINGER TELEPHONE METERING SYSTEM Filed July 15, 1935 3 Sheets-Sheet 1 o; i L QE 9 mm 2 53 Sim mzw 6 22m 91 2V. :5 -25 23: H 5% 23 .6 .5 U u u ss 5 4 Q 23 2s Loumwr? m 225 [EUR] A; "2; MO E 23w wmvmm m 6 mm 2 m w h VEWMTEmE- mvmw 5 5 E E. K e2 e3 e5 ATTORNEY.

Patented Mar. 2 1937 TELEPHONE METERING SYSTEM Eduard Wochinger, Berlin, Germany, assignor to Siemens & Halske Aktiengesellschaft, Wernerwerk, Siemensstadt, near Berlin, Germany Application July 15, 1935, Serial No. 31,355 In France July 26, 1934 13 Claims.

The present invention relates to telephone systems with main and subsidary exchanges and automatic operation. The general object is directed to improving these systems by making s them more dependable and eificient by avoiding the disturbances which occur especially during the setting up of calls and during metering, by

means of auxiliary devices of the simplest possible form.

According to the invention the metering operation occurring at the end of a call is prevented from being disturbed by the premature release of the call, in that a relay located in the main exchange and associated with the con necting line between the main and subsidiary exchange, and which maintains the outgoing connections of the subscribers of the subsidiary exchange, is held energized during the metering operation which takes place after the clearing signal has been given. 'Since the meters provided for metering the outgoing calls of the subsidiary exchange subscribers are centralized in the main exchange, it is convenient also to influence these same meters in the case of internal calls, in order to avoid the necessity of additional metering devices. This isachieved according to the inven-- tion in that, in thecase of internal calls between subscribers of the same subsidiary exchange, and from among the meters centralized in the main exchange belonging to subscribers connected to the subsidiary'exchange, the meter of the calling station is connected up by switching means in the, main exchange characterizing the calling subscriber,

Besides the special formation of the switching devices of the main exchange, the construction of the subsidiary exchange devices formaking the systems withmain and subsidiary exchanges 40 more dependable and efiicient is of particular importance. Thus, for example, the necessary disconnection of the other subscribers lines from a common calling circuit has previously been efiected by relays common to several subscribers lines. Since for the satisfactory working of the system the common relays can only be provided with a definite number of contacts the arrangement of several common relays is always neces- 5 sary in those cases when the number of subscribers lines exceeds a definite number. According to the invention the number of -these common relays is reduced in that in the normal condition of the selectors of the subsidiary exchange the subscribers lines attached to these are connected to the calling circuit passing to the main exchange partly over contacts controlled by the selectors of the subsidiary exchange, and partly over the contacts of relays common toseveral subscribers.

Three separate embodiments of the invention are illustrated in Figs. 1, 2, and 3.

In Fig. 1 a subsidiary exchange UA without batteries is shown as an embodiment of the invention, which has access to a main exchange HA over the connecting line consisting of two leads. The connection of the subsidiary exchange subscribers to this connecting line takes place over a selector DBIll which for outgoing calls acts as a call finder, and for incoming calls is set by numerical impulses as a final selector.

In the normal condition of the system relay U0, and further relays (LII, LIZ) in case the contacts to be provided for each subscriber cannot be operated by one relay, is operated over one lead of the connecting line. These relays connect all the subscribers of the subsidiary exchange in common to the calling circuit through their working contacts and on deenergizing which occurs when a subscriber calls, cause a switching over of the calling circuit so that the individual subscribers can be tested. In order to reduce the number of relays of this kind to a minimum, contacts operated mechanically by the selector of the subsidiary exchange are used for this purpose, for example Iwlli (I-I'I) and which are opened on the first switching motion of selector DBIB and remain open until position The setting of selector DBIIl in the subsidiary exchange UA always takes place under the control of the main exchange HA, both in the case of outgoing calls, when the selector is acting as a call finder, and also in the case of incoming calls when the selector is acting as a final selector.

As already mentioned, in the normal condition of the system relay LII], and, if present, also relays LII and LIZ are energized, over the circuit: earth, relays LIE, LII, LIB, wiper a in position 0, winding I of relay U! 0, lead a. of the connecting line, contacts ZIcIl], 391mm, wiper dIVIIl in position 0, contact 43x10, winding I of relay XI 0, battery, earth. In this circuit only relays LII], LII and LIZ are energized, while relay XII] does not receive suflicient current.

Outgoing trajfic When subscriber AI of the subsidiary exchange takes up his receiver the following circuit is set up: earth, contact 20am, winding II of relay UIB, wiper b in position 0, lead bI, subscriber AI, lead aI, contact Iwl0 (III), wiper a in position O, winding I of relay UH), lead a, contacts ZIcIll, 39anlll, wiper dIVIU in position 0, contact 43ml ll, winding I of relay Xi ii, battery, earth. Besides the transitory energizing of relay UI U relay XII] also energizes in this circuit and locks up by the closing of contact 42:11:!0 in series with its Winding II. The circuit just described passing over the a lead is opened at contact 43mm. In the subsidiary exchange relays LIB, LI I and LIZ release so that the switching magnet Wit of the selector in the subsidiary station is connected to the 1) lead over contact 23 I II). The following circuit is thus set up through the main exchange: earth, contact 23 I I8, switching magnet WID, contact came, lead b, contacts 24cm, liaylll, relay Kill, battery, earth. In this circuit both the switching magnet Wit) in the subsidiary exchange and also relay Kit in the main exchange are energized so that the switching device in the subsidiary exchange is advanced one step. Contact 52km switches on the switching magnet DIE in the main exchange through contact 53MB, so that the wipers d I Ifid IV Ill operated by this switching magnet D I 0 also advances one step. Through contact Eldld, which is operated each time switching magnet Dill energizes, relay Ylfi is energized over: earth, contact E'Idlfi, resistance Wi l, winding I of relay YIEl, battery, earth. Thereupon the en rgizing circuit of switching magnet Wit and relay Klll, completed over the b-lead of the connecting line, is broken at contact GB' IG. Switching magnet DH! is likewise disconnected by the opening of contact 5270). The interaction would if necessary be repeated again and accordingly both the switching device DBIt in the subsidiary exchange and also the switching device in the main exchange would be advanced in step. Since, however, the subscriber AI of the subsidiary exchange, connected to the first contact is calling, the testing relay PI 0, which after the occurrence of each step is connected to the a-lead over contact ltylll, is energized in the main exchange after the first step. This testing circuit is completed through: earth, contact ZQuIIl, winding II of relay Ulii, wiper b in position I, lead bl, subscriber AI lead a I, wiper a in position I, winding I of relay UII], lead a of the connecting line, contacts Z'Iclll, 390mm, wiper cZIVIE! in positions I-II, contacts Mm), 45ylil, relay PIG, battery, earth. In the same circuit relay Ult is energized in the subsidiary exchange. By the closing of contact 58pm, relay Ylti is next maintained energized over its winding I, while by the opening of contact 2mm, the switching magnet W18 of the switching device in the subsidiary exchange is cut off. The earth previously connected over contact Zllulil is replaced by earth connected over contacts 24cm, G'Iylil, 36km and choke coil DrII, by'the opening of contact wall and the closing of con; tact ZIuIil, so that complete symmetry exists between the two speaking leads, and no unbalance occurs in the subsidiary exchange. By the closing of contact 3Iplll a loop is also closed for seizing the exchange connecting devices, so that for example a presele-ctor can be set in operation after whose setting relay Cor is energized. The subscriber receives a dialling signal. He can then commence dialling.

On operating the dial the relay P I ll in the main exchange used for testing while the selector is being set releases intermittently according to the impulses, while relay UII! in the subsidiary eximpulses to the connecting devices of the main exchange by interrupting the line loop. On the first release of relay Pill relay VII} is influenced since contact 5Izrlll is also closed. The latter relay ensures a clean transmission of the impulses by short circuiting the choke coil DTIO at contact 39MB during the emission of the impulses, and disconnecting the condensers (contacts 282219 and 29mm.

The connecting devices of the main exchange are set in the desired direction by the various impulse trains in any suitable manner}, with which we are not concerned, and the desired subscriber is then rung in the known way.

It should be noted that the meters of the subsidiary exchange subscribers are centralized in the main exchange. In order now to be able to infiuence the corresponding meter when a subscriber sets up a call the meter is connected over a wiper of the switching device in the main exchange which controls the setting of the selector in the subsidiary exchange and is thus advanced in step with the latter. When the conversation has finished a meter impulse is transmitted over the lead 0, in any way, with which we are not concerned, which influences the meter SMI allocated to the calling subscriber. A second winding of relay YII] lies in the meter circuit and on energizing maintains the connection existing between the main exchange and the subsidiary exchange so that even when the calling subscriber replaces his receiver no release of the selector DBIU in the subsidiary exchange or of the switching device in the main exchange can take place during the metering process. If at the moment that the selector of the subsidiary exchange is engaging a subsoribers line during the further switching after the termination of the conversation, the subscriber of the line in question takes up his receiver, the connecting line leading to the main exchange can immediately be seized again. Since the selector of the subsidiary exchange has advanced in step with the switching device in the exchange, in this case also the meter corresponding to the subscriber reached is again connected to the c-lead.

If a new call does not take place, both switching devices are advanced to position II through the alternating play of the above mentioned relay. In the main exchange relay HI 0 energizes in this switching position over contact 38yl0, wiper d III I I) and resistance Wz'l, and by opening contact 53MB prevents the switching magnet DIO from being operated again and the consequent further switching of the corresponding wiper. The switching magnet WID in the subsidiary exchange is further operated, however, by the alternate play between relays KIU and Ylll, since the corresponding selector has to carry out I I steps to reach the zero position. This is continued until the selector DBIll in the subsidiary exchange reaches position II. In this position relays LIB, and LII and LIZ, now energize over: earth, relays LIZ, LII, LII], wiper a in position II, winding I of relay UIIJ, lead a of the connecting line, contacts 210), 390mm, @Bhlii, resistance Wz'5, battery, earth. Relay LIII cuts off the operating circuit of switching magnet WIO, at contact 23ZIO, so that relays KIO and YII) in the main exchange can also no longer energize. By the opening of contact 38g I ll relay HID deenergizes and opens the circuit for the L-relay passing over the a-lead, at contact 41mm. Thereupon this relay again deenergizes. Through the closing of contact 231m the operating circuit of switching magnet W III passing over the b-lead of the connecting line is again closed so that the selector in the subsidiary station makes one switching step (into the normal position). By relay KIO energizing in the operating circuit of switching magnet WI ll the switching magnet of the switching device in the main exchange is now operated over contact 52km, so that this switching device also makes one step, likewise into the normal position. Thus both are now standing again in position 0. On reaching this position the condition existing when the system is at rest is again set up (L-relay energized).

The number of steps of the selector in the subsidiary exchange are known to be larger than the number of steps of the switching device in the main exchange. Since, however, in order to actually connect up the motor of the calling subscriber through the switching device in the main exchange, the switching device and the selector in the subsidiary exchange must be synchronous, the arrangement is such, as described above, that the motion is synchronous until the 11th contact, i. e. until the first contact without any subscribers connection, whereupon the selector in the subsidiary exchange travels over the, remaining contacts and then accomplishes the last switching step together with the switching device. This release motion is achieved in that up until the 11th contact the relays Kill, Yili and the magnet DH) produce impulses for advancing both switching devices,

. nections.

whereupon the magnet Dlil is disconnected from the impulse producing circuit and by a switching over process (HID) impulses are only produced through relaysKHl and Yl0 for the magnet Will. In position I! this then causes a reversal of the change-over device so that for the last switching step the circuit first operative comes into operation again, together with the switching magnet Di ii.

Incoming tm fic The subscribers attached to the subsidiary station can obviously also be called from the main station. The last digit of their call numbers corresponds, for example, to the number ofsteps which the selector DB! in the subsidiary exchange must take in order to be set on their con- If they were previously subscribers having individual lines to the main exchange they can retain their original call numbers unaltered. Only the c-lead from the finalselector has to be disconnected from their previous connections and led to a contact of wiper d I ID. The a.- and 1)- leads of all subscribers lines incoming from the final selector are connected together in parallel. Thus both subscribers attached to the same level of a final selector and also those attached to different levels of the same final selector or in particular to different final selectors are incorporated in the subsidiary exchange while maintaining their call numbers.

. If a final selector (notshown) is set in any manner on the line leading to the subsidiary exchange for the purpose of calling subscriber A5, testing is carried out, in the known way, over the lead thus seized, as to whether the line leading to the apartment house exchange is free. If this is not the case, Wiper d III H! has left its position 0, so that the lead 05 incoming from the final selector is open and the calling subscriber reveives an engaged signal in the known way.

If on the contrary, the line leading to the subsidiary exchange is free relay Anlll is energized over the lead 05 (lead 05, resistance Wi9, contact 36010, relay Anlll, wiper 01 III IE] in position 0, resistance Wi'l, battery, earth). Relay Anlil lies in a circuit dependent upon wiper d III iii, via contact Man I 0. Through the opening of contact 391ml [I the circuit existing for relays LIB, Li I and LI2 in the normal condition of the system is broken, so that these relays deenergize. seizing from the subsidiary exchange is not possible since relay Pill which is otherwise used for testing is disconnected and the selector is brought to rest through setting the switching device in the main exchange under the control of the seized testing lead. By the closing of contact 232 I I] after the release of relay LIO the operating circuit for the switching magnet passing over the b-lead is closed in series with relay KID. Both switching devices now move synchronously as was described above for the case of the call of a subscriber of the subsidiary exchange. The advancement now, however, takes place until the wiper d I I0 comes to rest on the calling lead 05. When this occurs relay ciil energizes over the circuit: lead 05, wiper, d I I0, contact 320mm, relay CHI, battery, earth. By the opening of contact 24cm the operating circuit of magnet WI!) and also the control circuit for the magnet DIB are broken. The speaking leads are switched through to the final selector by the closing of contacts 250) and 26010. The ringing current is: transmitted to the desired subscriber from the final selector in any of the known ways, and passes over the a-lead of the connecting line of the subscribers station in the subsidiary exchange and the earth in the subsidiary station connected over contact Zilulfl. If the ringing current were connected over the b-line, then obviously the a and b -leads must be interchanged.

When the called subscriber replies the ringing current is disconnected by the completion of the loop in the final selector, and by the energizing of relay U i 0 over the speaking leads contact 2 i ul III is closed so that now lead I) of the connecting line is also switched through to the main exchange. The desired subscriber is now connected to the calling subscriber.

After the termination of the conversation lead 05 is cut off from the final selector in any desired way, so that relays Cl 0 and Ania, which had established a locking circuit over contact 35cl0, release. In the subsidiary exchange relay UN) is deenergized so that the operating circuit for magnet Wlil in the subsidiary exchange and for relay K"! in the main exchange is again completed over the b-lead of the connecting line. By relay Kill, the magnet DIE} of the selector in the main exchange is switched on through contact 52km. Thus the reciprocal play between the two switching devices, already described, causes the advancement into the normal position in the manner described in the case of the release for an outgoing connection.

Special circuits If the selector in the subsidiary exchange is displaced from position or by hand, and the two switching devices thus become out of step, relays Llil, Li I, LI2 deenergize since the normal circuit is broken at wiper a of the selector. The magnet Will is connected in an operating circuit through the closing of contact 23110, the circuit being completed as in the case of a call over relay Kit in the main exchange and the lead 2) of the connecting line running between the main exchange and the subsidiary exchange. The magnet DIE} in the main exchange is switched on by relay Kill, so that both switching devices are advanced under the control of the impulse circuit in the main exchange. Since in this case both switching devicesv are not synchronous the possibility of .a sub-:

scriber who hangs up during the advancement into the normal position, causing the connecting line leading to themain exchange to be seized must be prevented, for otherwise the meter of another subscriber would be operated in the main exchange. This is prevented in that through the displacement of the selector in the subsidiary exchange by hand, in contrast to the procedure in a normal call, relay K20 is energized in the main exchange, so that the testing relay PIG in the main exchange is not connected over contact 44mm, i. e. this relay cannot test and thus the advancement of the switching device into the normal position cannot be interrupted. For the rest the release motion occurs in the same way as after the normal establishment of a call i. e., advancement in step until the eleventh contact of the switch in the main exchange is reached, then the selector of the subsidiary exchange is con trolled alone until position H, and then the last step to the zero position is accomplished by both switching devices in common. The two switches are thus again in corresponding positions.

The same switching operations take place when the switching device of the main exchange is displaced from the zero position by hand.

In this case the wiper d IV l0 cuts off the a.-lead oi the connecting line so that relay X10 cannot be energized. seizing during the release motion is thus prevented. By the interruption of the circuit existing in the normal condition relays Ll0, Li! and LI2 again deenergize, whereupon the magnet Wl0 in the subsidiary exchange is again connected in an operating circuit over contact 23 l 10, and is influenced by the reciprocal play of relays KM and Yl0, partly together with the switching magnet DH) in the main ex change, and partly independently, as mentioned above, until the zero position is reached. They can then operate synchronously again when the next call is set up.

Each seizing of the devices in the main exchange can be indicated by a seizure lamp L. If desired, each seizing direction can be indicated specifically, if the contacts 559310 for the outgoing seizing and 56anl0 for the incoming seizing are wired separately.

In Fig. 2 a subsidiary exchange UA without batteries is shown as a further embodiment of the invention. Several subscribers are attached to this subsidiary exchange who can reach a connecting line leading to a main exchange HA over a selector DB20. The setting of the selector, which for outgoing calls acts as a call finder, and for incoming calls as a final selector, is controlled in each of the two directions by a switching device in the main exchange. In order to reduce the number of relays in the subsidiary exchange as much as possible, auxiliary leads are led oii from the speaking leads to the subscriber. Moreover, the connecting line between the main exchange and subsidiary exchange is made of four wires, of which one of the two auxiliary wires serves for extending the calling impulses from the subsidiary exchange to the main exchange, and the other for extending the setting impulses transmitted from the main exchange to the selector of the subsidiary exchange. By this arrangement it is only necessary to provide the magnet W20 for the selector DB20 serving for connection to the subscribers, without further relays being necessary. These wires of the concondition of the system.

ing line (earth, key BI, contact 20lw20 |Il) which is operated mechanically by the switching device DB20 so that it is open in positions Il1,

d-lead, relay X20, wiper d IV 20 in position 0, contact 2l2h20, resistance Will, battery, earth. Relay X20 establishes a locking circuit for itself independent upon wiper dIV 20 by closing contact 2|5X20. By closing contact 213x20 the following circuit is set up: earth, magnet W20 of selector DB20 in the subsidiary exchange, c-lead of the connecting line, contacts 223y20, 224020, relay K20, contact 2| 3x20, resistance Will, battery, earth. In this circuit the magnet W20 energizes in series with relay K20. The selector DB20 in the subsidiary exchange takes a step forward whereupon its mechanically operated contact 29lw20 (l-Il) opens and its mechanically operated contact 202w20 (ll6) closes, so that the transitory depression of the key Bl suffices to bring about the calling condition.

As already stated relay K20 energized together with the magnet W20 so that the magnet D20 of the switching device in the main exchange is also switched on, over contact Zl9k20, and hence the switching device in the main exchange advances one step. By the energizing of magnet D20 contact 2l0d20 is closed so that relay Y20 is energized over this contact and resistance Wil. By the opening of contact 2231120 the current is cut ofi from the magnet W20 in the subsidiary exchange and relay K20 in the main exchange. Magnet D20 is also cut oil from its energizing current by the opening of contact 2.!97020, so that by the opening of contact 2I0d20 relay Y20 is again deenergized. Contact 223y20 is thus again closed so that the switching magnet W20 in the subsidiary exchange and the relay K20 .in the main exchange can be energized again. This alternating play is continued until the selector in the subsidiary exchange has reached the position of the calling subscriber. Since in the present example the subscriber AI attached to the first contact of selector DB20 is calling, the advancing terminates after one step, and on reaching this calling subscriber the following circuit is set up: earth, contact 205:1:20,

winding II of relay Y20, contact 206001, a-lead of the connecting line, wiper a of the selector in the subsidiary exchange in position I, subscriber Al, wiper b of the selector in the subsidiary exchange in position I, b-lead, contact 201cm, relay Lr, battery, earth. Relays Y20 and LT are energized in this circuit so that a further advancement of the switching device is prevented by the opening of contact 223y20. Relay Y20 for producing the impulses for the selector of the subsidiary exchange and for the switching device in the main exchange thus serves also as a testing relay When setting up outgoing calls. Relay Lr seizes connecting devices in the main exchange in any known manner. A pre-selector or a call finder can thus, for example, be set in operation which establishes a connection with a free numerical impulse receiver in the exchange. When such a numerical impulse receiver is reached relay Cor in the main exchange is switched on over the c-lead. Relay Y20 which maintains the connection with the subsidiary exchange is held energized through its winding III over the c-lead in parallel with relay Cor and in series with the meter SM! connected over wiper 11 II 20. The meter itself is not yet operated in this circuit. By the opening of contacts 206001 and 201001 leads aand bare disconnected, so that the subscriber of the subsidiary exchangeis switched through as a normal individual line subscriber without any unbalance.

By sending out impulses which operate on the corresponding numerical impulse receiver in the exchange (not shown) the calling subscriber can set up the desired call.

When the calling subscriber has finished his conversation the call metering takes place. The meters of all the subsidiary exchange subscribers are centralized in the main exchange. The meter corresponding to the calling subscriber is connected through a wiper of the switching device 1120 which is set synchronously with the selector in the subsidiary exchange. Metering now takes place in that metering impulses are transmitted to the meter SMI of the calling subscriber AI which is connected through the switching device, by increasing the strength of the current. Relay Y20 is held energized in this circuit over its winding III during the metering. Relay Y20 does not release until, after the metering, the c-lead is disconnected. By the closing of contact 2231 20 the circuit of relay K20 and switching magnet W20 passing over the c-lead to the subsidiary exchange is then again closed. The switching device is now advanced into the rest position as in the case of setting on the calling subscribers line in that the circuit for both switching devices is again made and broken through the alternating play between magnet W20 and the relays K20, Y20 and themagnet D20. Both run synchronously so that when the selector DB20 comes to a calling subscribers line both switching devices are immediately brought to rest in the manner already shown, and connecting devices are seized in the main exchange. If no new call has been initiated, relay H20 is energized in position ll of the switching device in the main exchange, the circuit being: earth, battery, resistance Willi, wiper (2 III 20 in position ll, contact 2251120, relay H20, earth. By the opening of contact2l8h20 the magnet D20 is cut off, so that the impulses produced in the main exchange only through relays K20 and Y20 now only influence the magnet W20 in the subsidiary exchange. When the selector in the subsidiary exchange reaches position I 'l the mechanically operated contact 202w20 (I IB) is opened,

among others, and thereby relay K20 is deene ergized in the main exchange. Since contacts 213.120 and 2|2h20 are open a further operation of the magnet W20 in the subsidiary exchange 2l2h20 a circuit is again set up through: earth,

main exchange is also operated, over contact.

2l8h20, and by taking one step is brought to the normal position. Thus both switching devices are brought to the normal position together through the last step.

Incoming traffic The subscribers who are attached to the subsidiary exchange receive as the last digit of their call numbers the number of the steps which the selector in the subsidiary exchange has to make corresponding to the setting of the final selector in the main exchange. have been individual subscribers they can retain their previous call numbers unaltered. Only the c-lead ofthe final selector is disconnected from the previous subscribers bank positions and is led to a contact of the Wiper d1 20, which corresponds to the contact of the selector in the subsidiary exchange. The aand b-leads of all incoming subscribers lines are connected in parallel.

If the line leading to the subsidiary exchange is already seized, the wiper d III 20 is away from the rest position so that the testing final selector finds no potential for testing. The calling subscriber receives the busy signal in the normal way. If on the other hand the line is free then assuming subscriber A6 is the desired subscriber the final selector tests on lead 06, whereupon relay An20 is energized. Relay A1120 locks up independently of wiper (1 III 20 over its contact 226 c.1220, while contact 2I4cm20 connects battery to the c-lead leading to the subsidiary exchange. Relay K20 is thus energized in themain exchange and switching magnet W20 in the subsidiary exchange. the magnet W20 and relays K20 and Y20, which is operated through the magnet D20, and which has already been described in the case of establishing an outgoing call, now sets in, so that both switching devices are rotated synchronously until wiper d1 20 stands on the incoming lead 00. Relay C20 connected through contact 222an20 now energizes over this lead and at contact 224020 breaks the operating circuit (lead 0) for the magnet W20 and the relay K20. Both switching devices are brought to rest. Previously contact ZZTG'ILZU connected earth to the winding of relay C01 so that this relay energized and prevented the connecting line from being seized from the subsidiary exchange, by opening con-.

tacts 200001 and 201001. Through the closing of contacts 203020 and204c20 the desired subscribers line is switched through to the final selector. It is now connected to the final selector contact bank just as a normal individual subscriber. The subscriber can now be rung in any known way, after which, when the desired subscriber replies, the speaking connection is established.

On the termination of the conversation lead 06 is cut off in the final selector, so that relay C20 releases. Contact 224020 again closes the operating circuit for the switching magnet W20 in the subsidiary exchange and relay K20 in the main exchange, passing over the 6- lead of the connecting line, so that the selector in the subsidiary exchange and the switching device in the main exchange are both advanced under com- [1, while the switching device in the main ex change remains still. The last step i. e. the ad- Should they previously The alternating play between vancement into the normal position is again accomplished synchronously with the switching device of the main exchange. A fresh seizure in either direction can only occur when both switching devices have reached the normal position.

Special circuits If the selector in the subsidiary exchange is displaced from the normal position by hand, the two switching devices are thus brought out of step, and earth is attached to the d-lead of the connecting line leading to the main exchange, by means of contacts 202w20 (ll0) whereupon relay X20 is immediately operated as in the case of a call proceeding from a subscriber in the subsidiary exchange. The locking circuit of relay X20 is completed by the closing of contact 2 I 5x20. By contact 2|3x20 the magnet W20 is held until relay K20 has also switched the wiper of the switching device in the main exchange into position I, so that they are once more in. step. When relay Y20 then energizes over contact 2l0d20, the c-lead is then cut oil so that the circuit over the c-lead is broken. Through this alternating operation the switching devices are returned to the rest position synchronously as in the case of the release motion.

If on the other hand the switching device of the main exchange is brought to the normal position by hand the c-lead to the subsidiary exchange is likewise'connected up over Wiper ct IV 20, and the magnet W20 in the subsidiary exchange is energized in series with relay K20. In this case also both switching devices are controlled in the manner already described until they reach the normal position. Since, however, in this case, under some circumstances the switching devices are not working synchronously i. e. they have become out of step, because the switching device in the main exchange can be moved on by hand quicker than the switching device in the subsidiary exchange, the possibility of seizing under these conditions must be prevented. This is achieved in that the testing relay Y20 of the connecting line can only draw up over the loop of the calling subscriber when the contact 205x20 has been connected to the a-lead of the connecting line. Since, however, relay X20 is not energized this is not possible, so that the line of a subscriber of the subsidiary exchange who is calling under these circumstances is prevented from being seized.

Each seizure of the connecting line lights up the seizure lamp L. In series with this lamp the seizure can also be recorded. If desired each seizing device can be recorded separately, in which case contacts 220x20 and 22|c20 are wired separately.

In Fig. 3 a system with a main and subsidiary exchange is illustrated as an additional embodiment of the invention. This in addition to the outgoing and incoming calls enables connections to be set up between subscribers of the same subsidiary exchange. For this purpose, in addition to selector DB30 which serves for setting up outgoing and incoming calls (exchange calls) and thus works as a double purpose selector, a second selector LW30 is provided in the subsidiary exchange which serves to set up internal connections within the subsidiary exchange. This auxiliary selector is connected over an auxiliary line (112 hi?) between the subsidiary exchange and main exchange to the connecting line leading to the main exchange which is seized by calling subscribers.

In order to differentiatebetween the difierent call directions i. e. outgoing exchange calls and internal calls, an additional switching device is provided (magnet Di30, wipers dz I 30d2' IV 30) in the main exchange which is switched round according to the characterizing number dialled so that either a call is set up over the connecting devices of the main exchange, or the auxiliary selector Lw30 in the subsidiary exchange can be set on the desired subscribers connection. In the present embodiment the characterizing is arranged so that by dialling the digit 1 an outgoing exchange call is characterized, while by dialling the subscribers number directly i. e. any digit except 1, an internal call and thereupon the subscriber desired in the internal call, is characterized.

The characterizing digit for the outgoing exchange call is not taken up by the connecting devices in the main exchange, but only by the characterizing switching device and the auxiliary selector Lw30 is provided in the subsidiary exchange.

In the normal condition of the system all the selectors both in the subsidiary exchange and also the switching devices in the main exchange and in addition all the relays, are uninfluenced.

Outgoing calls When a subscriber takes up his receiver and momentarily depresses the key, for example B2 in the case of subscriber A2, earth is connected to lead al of the connecting line leading to the main exchange. In the main exchange relay X30 energizes over the circuit: earth, battery, resistance W119, wiper d II 30, winding I of relay X30, contacts 345x30, 348M130, 350030, lead al, winding I of relay U3l, wiper al of selector DB30 in position 0, key B2, earth. Relay X30 locks up over its winding II on closing its contact 375x30. Contact 345.1130 disconnects battery from the lead al of the connecting line. Contact 337x30, however connects battery to the bi lead. The following circuit is then set up: earth, magnet W3l, contact 300u3l, bl lead of the connecting line, contacts 335030, 331x31, 3300230, 3421130, relay K30, battery, earth. In this circuit the magnet W3l energizes in the subsidiary exchange and relay K30 in the main exchange, so that selector DB30 in the subsidiary exchange advances one step. Similarly the switching device influenced by the magnet D30 in the main exchange is advanced one step, after this magnet has been energized over contact 3|6lc30. On the energizing of this magnet contact 3l0d30 is closed and thus relay Y30 is switched on over resistance Wz'24. This relay opens its contacts 3421/30, among others, so that the operating circuit of magnet W3I and relay K30 is broken, so that these are both deenergized. By the opening of contact 3l6k30 magnet D30 is also deenergized which again results in the opening of contact 3| M30 and hence the deenergizing of relay Y30. Contact 342y30 is again closed and thereby the operating circuit for magnet W3! and for relay K30 is set up afresh, so that selector DB30 in the subsidiary exchange and the switching device in the main exchange which is influenced by relay K30, advance a further step.

Since the calling subscriber A2 is connected to the second contact of selector D330, on reaching this contact, after relay Y30 has operated as before after the completion of the second switching step, the following circuit is set up: earth, battery, relay P30, contacts 3411 30, 346x30,

held energized so that by the opening of contact 342y30 further transmission of impulses for advancing the switching device is prevented. Earth is connected to lead bl over contact 3401/30 and the choke Dr3l, so that after opening contact 301u 3l and closing contact 303u3l the following locking circuit is set up for relay UM, energized in the above testing circuit: earth, choke coil Dr3l, contacts 34lk30, 3401/30, wiper 11 IV 30 in position l--| I, contact 335030, lead bl of the connecting line, contact 308u3l, winding II of relay U3l, wiper bl of selector DB30 in position 2, subscriber A2, wiper a! of selector DB30 in position 2, winding I of relay U3l, lead al of the 3 connecting line, contacts 350030, 348an30, 3465030,

3411130, relay P30, battery, earth. At contact 3541130 a loop is closed for the connecting devices of the main exchange so that, just as in the case of a subscriber having an individual line, a preselecting device, for example a call finder, is set in operation. After the setting of such a preselecting device, if the calling subscriber is connected to a free connecting device he received a signal from the exchange.

Since it is an outgoing call which is being set up in the present case, the subscriber must dial the characterizing digit I. It should be added that relay J30 was energized over contacts 3243030 and 3261130 and also over wiper dz III 30 in position 0, so that contact 3541030 which was closed by the testing relay P30 which operates as the impulse relay during the numerical selection is shunted by contact 355730. The selection of the characterizing digit I is accordingly not transmitted to the connecting devices of the main exchange. On the first impulse i. e. on the first deenergizing of relay P30 the magnet Di30 of the characterizing switching device is operated in the main exchange over contacts 324x30,

321.p30, and 328730, and relay V30 is operated in parallel with the magnet; moreover, by the transitory closing of contact 3151230, battery is connected over contact 374730 to the b2 lead of the auxiliary connecting line and hence magnet W32 of the auxiliary selector LW30 is operated.

By means of relay V30, energized during the impulse emission, the choke coil D130 is short circuited by the closing of contact 352030, and by the opening of contacts 35lv30 and 3531230 the condensers in the speaking leads are disconnected so as to insure a more clear impulse emission. After the one impulse has been given relay V30 deenergizes on account of the prolonged opening of contact 3211930, so that relay J30, which after one step has been made holds up over wiper dz III 30 in position I and over contact 325030, is deenergized. The short circuit of impulse contact 35 lp30 is accordingly removed by the opening of contact 355:!30 so that the next impulse trains can be transmitted to the connecting devices of the main exchange. The magnet W32 in the subsidiary exchange, which previously displaced the auxiliary selector LW30 one step, can no longer be efiected since the corresponding impulse is broken at contact 374730.

When the desired subscriber is reached, after testing on the contact in the normal way, ringing current is transmitted and the speaking connection is established on the desired subscriber replying. When the conversation has finished a metering impulse is transmitted on the c-lead in any desired manner which does not concern us here. This is extended to the meter SM2 in the main exchange corresponding to the calling subscriber of the subsidiary exchange. The connecting of the corresponding meter takes place on the setting of selector DB30 in the subsidiary exchange by the switching device in the main exchange controlling this selector.

By the switching on of winding II of relay Y30 in the c-lead, which relay assists in sending out the control impulses, theexisting connection is prevented from being released during this metering even when the calling subscriber replaces his receiver and thereby releases relay P30 which lies in the circuit of the speaking current. When the metering is completed and the calling subscriber replaces his receiver relays P30 and 133i deenergize. Since a locking circuit no longer exists for relay Y30 in the c-lead it is disconnected by the opening of contact 3|3p30 so that it deenergizes. At contacts 342y30 and 309u3! the operating circuit through magnet W3! and relay K30 in series is closed again, so that now, in the same way as for the setting of selector DB30 on the calling subscriber, this is again controlled synchronously by the switching device in the main exchange.

which the subscriber has just taken up the receiver, seizing can at once take place again, since both the selector in the subsidiary exchange and the switching device in the main exchange are both in the same switching position, so that the meter in the main exchange corresponding to the calling subscriber is also connected up when the switches are brought to rest. If such a call does not occur,- and selector DB30 and the controlling switching device in the main exchange accord- 'ingly reach position H, relay E30 energizes in the main exchange over: earth, battery, relay,

E30, wiper (1 III 30 in position I I, contact 324x30,

earth. Relay E30 establishes a locking circuit.

for itself over its contact 363e30. The operating circuit passing over the bi lead is broken by contact 330630, and also battery is connected to lead M of the auxiliary connecting line, so that now magnet W32 of selector LW30 which stands in position i is influenced in series with relay K30 of the main exchange. The impulse circuit previously operating magnet D30 is correspondingly opened at contact 3l2e30 and is switched over to magnet Di30 of the characterizing selector by the closing or contact H3630. The auxiliary selector LW30 is accordingly switched on one step, and through the energizing of relay K30 in the same circuit magnet D is operated over contact 3167030, and likewise advances the characterizing selector one step. Relay Y30 is operated by the closing of contact 3i'ld2'30, and by opening contact 3421/30 breaks the operating circuit for the magnet W32 and relay K30. Contact 3l6lc30 is accordingly opened, so that by the disconnection of. magnet D230 and the associated opening of contact 3i'ldi3, relay Y30 is deenergized and the operating circuit for magnet W32 and relay Y30 is again closed. This alternating play is repeated until the characterizing switching device has reached position H. When this occurs relay H30 is operated over wiper d2 I30 If the selector- DB30 thus moves on to a subscribers line in and contact 3161 30, and hence contact 3Mh30 is opened which now breaks the impulse circuit for magnet D230 and connects relay Y30 directly in this impulse circuit. Relay X30 deenergizes on the opening of contact 3l2h30. The auxiliary selector LW30 is moved on further by means of impulses from the main exchange, but there the characterizing switching device does not move with it. The switching device LW30 continues to be advanced until it reaches position H. In this position earth is connected to the lead a2 over wiper a2 of the switching device LW30. Thus relay U32 is energized in the following circuit: earth, wiper a2 of switching device LW30 in position l'l, winding I of relay U32, lead a2 of the connecting line, contact 3447130, resistance Wil9, battery, earth. By the opening of contact 302u32 the switching magnet W32 is disconnected and also the circuit of relay K30 is broken. The current is cut off from relay Y30 by the opening of contact 3l0k30 so that this relay opens contact 3611/30 and deenergizes relay H30. Contact 344h30 is opened and the energizing circuit of relay U32 described above is broken down. Contact 302u32 again closes the operating circuit for magnet W32 and relay K32, so that selector LW30 in the subsidiary exchange advances one step and likewise the magnet D energized over contact 3l07c30 advances the characterizing switching device in the main exchange by one step. Accordingly both switching devices accomplish the last step into the normal position together. In the position 0 of wiper 031' I 30 relay E30 remains energized over contacts 364. 139 and 365e30 until, since relay Y30 is energized over contact 3lldz'30 through the last switching step, relay H30 is again energized over: earth, wiper (ii I 30 in position 0, contacts 305e30, 368x30, relay H30, battery, earth. By the opening of contact 36471.30 the locking circuit for relay E30 is broken and this relay therefore deenergizes. Relay H30 holds up, after the opening of contact 365e30 over contact 31171.30. After contact 3lldi30 has opened relay Y30 again deenergizes. By the closing of contact 339e30 relay K30 is furthermore again connected to the bl lead of the connecting line and also preparation is made for switching in the magnet D30 of the switching device in the main exchange in the impulse circuit already described, over contact 3l2e30. Thereupon only magnet W3l is operated in series with relay K30. The latter causes relay Y30 to energize over contact 3l6k30, so that this opens the energizing circuit of magnet W3l by opening contact 3421 30. By the alternate play of these relays the switching magnet is influenced until the selector DB30 reaches position l1. In this position the following circuit is set up: earth, wiper al of selector DB30 in position 11, winding I of relay U3l, lead al of the connecting line, contacts 330030, 2400,1130, 345x30, 34471.30, resistance Wil9, battery, earth. Relay U3l energizes and by opening contact 309u3l disconnects the magnet W3l. Relays K30 and Y30 then also release so that now relay H30 is deenergized by the opening of contact 3611 30. Through the closing of contact 3l4h30 the switching magnet D30 in the main exchange is connected up while the energizing circuit just described for relay U3l is broken down at contact 3 3M130. The operating circuit for magnet W3l and relay K30 is accordingly closed again at contact 309u3l. The selector DB30 is thus advanced one step and moves into the normal position. At the same time magnet D30 is also influenced by the closing of contact 3l6h30 so that the switching device in the main exchange similarly make one switching step which takes it into the normal position. Since the wiper d IV 30 of this switching device has now left contact segments l-l I further advancement of the switching devices is not possible. All the devices both in the subsidiary and also in the main exchange are now again in the normal position.

Incoming trafiic If a subscriber of the subsidiary exchange, for example A2 is called from the main exchange, a final selector, which is not shown, is set by the corresponding numerical selection. If the connecting line leading to the subsidiary exchange is already seized the wiper d I 30 is not in the normalposition, so that the final selector cannot test over the c-lead. (02) corresponding to the desired subscriber. The wiper d I 30 remains away from the normal position as long as any of the switching devices of the connecting line either in the main exchange or in the subsidiary exchange are displaced from the normal position. Seizing the connecting line over a final selector is only possible when all these switching devices have reached the normal position. In the present case the final selector tests over the lead 02 corresponding to the subscriber A2. The circuit passes over resistance Wi20, contact 350030, relay A1130, wiper d I 30 in position 0, contact 369a1t30, resistance Wz'22, battery, earth. Relay A1230 energizes in this circuit and locks up independently of wiper d I 30 over contact 3590,1130. At contact 348cm30 battery is disconnected from the al lead of the connecting line, so that no seizure of the connecting line can take place from the subsidiary exchange. At contact 336111230 battery is connected to lead bl of the connecting line, through relay K30. The following circuit is thus set up: earth, magnet W3I, contact 309u3l, lead bl of the connecting line, contacts 335030, 336an30, 3391130, 3421 30, relay K30, battery, earth. By the alternate play between magnet W3l and the magnet D30 in the main exchange operated by relays K30 or Y30 (as described in the case of outgoing traffic), the selector DB30 in the subsidiary exchange is now advanced synchronously with the switching device in the main exchange operated by magnet D30. This advancement is continued until the wiper d'I 30 has reached the lead 02 seized by the final selector. At this moment the selector DB30 has also reached the second contact, to which subscriber A2 is connected. When this occurs relay C30 tests over contact 36 lcm30 and by opening contact 335030 prevents both the switching devices mentioned from being further advanced. At contacts 334030 and 349030 the speaking leads of the connecting line are switched over on to the speaking leads of the final selector. Relay A1130 now holds up over contact 351030. Ringing current can now be sent from the final selector, which is not shown, to the desired subscriber A2 of the subsidiary exchange in the known way. When the desired subscriber replies the ringing current is disconnected in the final selector in any manner with which we are not new concerned. Relay U3l is operated over the subscriber's loop by the feeding current connected in the final selector, so that the bl lead of the connecting line is switched through at contact 308u3l, and magnet W3l is disconnected at contact 300u3l. The subscriber A2 is now connected to the final selector of the main exchange just as a normal subscriber having an individual line.

When the conversation has finished the 02 lead is disconnected in the final selector, relay C30 being thus deenergized. Contacts 334030 and 33903!) open and break the circuit for the feeding current, so that relay U3! deenergizes. One effect of this is that the operating circuit for magnet W3! and relay K3t is closed through the closing of contact 339ml. Through the alternate play of the corresponding relays the selector D1333 in the subsidiary exchange is advanced synchronously with the switching device in the main exchange. Thus, in the same way as was explained in the case of outgoing traffic, the selector in the subsidiary station is first advanced synchronously with the switching device in the main exchange until position is reached. Then it is moved on as far as position I! alone by means of impulses from the main station, whereupon it completes the final step into the normal position together with the switching device of the main exchange. During the release motion of the switching devices seizing cannot take place again until the two switching devices have returned to the normal position, since, in the case of an incoming call, relay Y33 which takes up the initiation of a call is otherwise not energized.

Internal calls Seizing the connecting line leading to the main exchange by the calling subscriber attached to the subsidiary exchange takes place in the same way as has already been described in the case of outgoing trafiic. While in the case of outgoing trail-lo (exchange calls) the subscriber had to dial the characterizing digit in the case of internal calls he must now dial the number which the desired subscriber has for internal calls, immediately. Since the digit is employed for outgoing traific, the internal numbers of the subscribers are limited to the numbers 2 to 10. Thus in this case 9 subscribers can be attached to the subsidiary exchange.

As described above, relays J33 and V are energized during the calling, while relay P30 is intermittently deenergized by the impulses, so that if, for example, the calling subscriber A2 desires a connection to subscriber A3 and accordingly dials the digit 3, magnet W32 received three impulses over the lead 172 and contacts 31473!) and 3151030 (impulse contact). The auxiliary selector LW33 is thus set on the third contact. The characterizing switching device is advanced synchronously by its magnet D539 to the third contact. After the dialling relay V33 is deenergized and relay Z33 is influenced over: earth, battery, relay Z33, contact 3631133, wiper dz I 30 in position 3, earth. Since the impulse contact 3541033 in the main exchange loop is shunted during the dialling, by contact 355133, the connecting devices of the main exchange are not set. By the opening of contact 356233 the pro-selecting device in the main exchange is now no longer seized. Since relay J 3!! remains energized over: earth, contacts 3231/30, 322733, 32ip3l, wiper di III 33, relay J33, battery, earth, relay R33 is operated over: earth, battery, relay R3!) contacts 339733, 373233, 3 seconds switch. Subscriber A3 is called by ringing current transmitted from the main exchange: ringing current source, contacts 353133, 332233, 3331030, lead a of the connecting line, winding I of relay U32, wiper c of the auxiliary selector LW3B in position 3, subscriber A3,

wiper b of the auxiliary selector LW3 in position 3, winding II of relay U32, contact 303u32, earth. Since relay R33 is influenced over a second switch ringing current is transmitted to the desired subscriber every three seconds. The calling subscriber receives part of this ringing current as a free signal over contact 3!!)1'30.

If the desired subscriber replies within a pause in the ringing i. e. at a moment when relay R3!) is deenergized the following circuit is set up: earth, contact 503i/L32,winding II of relay U32, wiper D2 of the auxiliary selector LW30 in position 3, subscriber A3, wiper c2 of the auxiliary selector LW30 in position 3, winding I of relay U32, lead a of the connecting line, contacts 3331233, 332233, 33lr33, winding I of relay P3l, battery, earth. In this circuit relays P3! and U32, energize. Since contact 303u32 is opened on the energizing of relay U32, the earth necessary for holding relays U32 and P32 energized is connected through contact 3Hp3! and winding II of relay P3! after the lead D2 of the connecting line has been switched through. Meanwhile relay J33 is deenergized by the opening of contact 32!;13! and relay R33 is deenergized by the opening of contact 369733, so that further transmission of ringing current is prevented. The feeding current for both subscribers is supplied from the main exchange. For subscriber A2 the circuit runs from the battery connected to lead a! and relay P30, to the earth connected through the choke coil D13! to lead 221, while for subscriber A3 current is fed from the battery connected through winding I of relay P3! to lead (12 of the connecting line, to the earth connected through winding II of relay P3! to lead 122.

Metering of internal calls takes place by the meter SM2 of the calling subscriber A2, connected through the switching device of the main exchange (wiper d II 33), being influenced over contacts 362233, 323133, 3233133, and earth.

On the termination of the conversation, when the calling subscriber replaces his receiver relays P33 and U3! deenergize. Contact 3l9p30 opens and relay Y3!) is thus deenergized, while by the opening of contact 3331230 relay P3! is decnergized. By the closing of contact 342y33 battery is connected to the b! lead of the connecting line over relay K30, so that the magnet W3! of selector D1333 in the subsidiary exchange is energized. By the alternate play which has already been described above, the selector of the subsidiary exchange is advanced synchronously with the switching devices of the main exchange so that both switching devices are stepped round as far as position !I. In position relay H30 again energizes and causes the auxiliary selector LW33 in the subsidiary exchange to be advanced in the manner already described, under the influence of the corresponding magnet W32. The characterizing switch-ing device is switched on together with this selector. When these two switching devices reach the normal position by the switching operations described above, the selector DB3!) of the subsidiary exchange is moved on automatically under the control of relays K33 and Y3!) in the main exchange until it reaches position II. It then completes the final switching step into the normal position together with the switching device in the main exchange.

This short description of the release motion should sufiice, since a detailed description has already been given of the release in the case of an outgoing call.

If the called subscriber of an internal call does not reply, relay P30 releases when the calling subscriber replaces his receiver, while relay J30 is only released after the release of relay Y30. Accordingly the earth is disconnected from the metering circuit by contact 3201 30 before contact 323730 closes so that in this case metering does not take place.

Special circuits If the selector DB30 in the subsidiary exchange is displaced from the normal position by hand, earth is connected over contact 30lw3l to lead a2 over wiper a of the auxiliary selector LW30, so that relay X30 is energized in the main exchange and locks up over contact 313x30. Battery is connected to the bl lead over contact 331x30 and. thus the magnet W3l in the subsidiary exchange is influenced in series with relay K30 in the main exchange. The selector DB30 is now held until magnet D30 in the main exchange has been switched on through the closing of contact 3ll5k30 whereupon both switching devices are advanced synchronously as in the case of a subscribers call, until they reach position I I. In this position relay E30 energizes, as in the case above, and causes the auxiliary selector LW30 in the subsidiary exchange and the characterizing selector (rotary magnet D2) to advance synchronously to position ll, whereupon the auxiliary selector continues to advance alone into position I! in precisely the same way as in the case of the release of an outgoing call, the last step into the normal position being executed together with the characterizing switching device. After this selector DB30 is advanced into position I! and then finally into the normal position the last step being made together with the switching device of the main exchange. If the magnet W32 of the auxiliary selector is displaced from the normal position by hand contact 305w32 (l0l7) connects earth over wiper al of the selector DB30 to the al lead of the connecting line, so that relay X30 is again influenced. In a manner corresponding to that above, selector DB30 and the switching device in the main exchange which is operated by magnet D30, are again advanced, whereupon after reaching position ll, the magnet W32 of auxiliary selector LW3I is influenced synchronously with the characterizing switching device D2'30. The release motion thus takes the same course as is described above. If both selectors in the subsidiary exchange are displaced from the normal position simultaneously, then since contacts 0 and l are connected together in the auxiliary selector, earth is connected to the lead a of the connecting line over contact 30lw3l, so that again relay X30 is operated and the release motion de' scribed above takes place.

If the switching device in the main exchange which is operated by magnet D30 is displaced from the normal position by hand, battery is connected to lead bl over wiper d IV 30, and hence the selector D1330 in the subsidiary exchange and the switching device in the main exchange are advanced by the known interaction. All other operations take place as above. In contrast with the movements described above, the connecting line cannot be seized during this return motion, because relay X30, which prepares a circuit for the testing relay P30, is not energized. If the characterizing switching device which is operated by magnet D is displaced by hand from the normal position, relay E30 energizes over wiper di IV 30, and through contact 338e30 completes a circuit for magnet W32 in the subsidiary exchange and relay K30 in the main exchange, so that now the characterizing switching device in the main exchange and the auxiliary selector LW30 in the subsidiary exchange are advanced synchronously by the interaction as above. If, for example, at this moment seizing takes place on the part of the final selector, in the main exchange, relays A1230 and C30 can be energized but the selector DB30 in the subsidiary exchange can only be set when the characterizing selector Di30 is in the normal position, so that relay Z30 releases and by closing contact 339030 connects battery to the bl lead of the connecting line. Each seizure is indicated by the lighting up of the seizing lamp L. seizing can also be recorded. If seizing in the incoming and outgoing directions is to be recorded separately the contacts 3'l2h30 and 3'lan30 can be led separately to a recording device.

What is claimed is:

1. In an automatic telephone system, a main and a subsidiary exchange, a trunk line connecting said exchanges together, means controlled by a calling subscriber in the subsidiary exchange for establishing a connection over said trunk line with a subscriber in the main exchange, a meter at the main exchange individual to said calling subsidiary subscriber, means for operating said meter responsive to the calling subscriber replacing his receiver to terminate the established connection, a relay at the main exchange, and means controlled by said relay for maintaining said connection established during the operation of said meter. I

2. In an automatic telephone system, a main and a subsidiary exchange, a trunk line extending betwen said exchanges, means for establishing a connection from a subscriber in the subsiduary exchange over said trunk line to a subscriber in the main exchange, a meter at the main exchange associated with the calling subsidiary subscriber, a relay at the main exchange associated with said trunk line and operated to maintain the established connection between the subscribers, means for operating the calling subscribers meter when the established connection.

is to be released, said relay remaining operated to maintain said connection over said trunk line during the time said meter is being operated.

3, In an automatic telephone system, a main and a subsidiary exchange, a trunk line extending between said exchanges, means controlled by a calling subscriber for establishing a connection over said trunk line with a called subscriber in the main exchange, a meter at the main exchange individual to the calling subscriber, a relay at the main exchange associated with said trunk line, said relay controlled by said calling subscriber and operated to maintain the established connection over said trunk line, means responsive to the replacement of the receiver by the calling subscriber for operating said meter and for maintaining said relay operated to hold the connection over the trunk line until said metering operation has been completed although the calling subscriber has replaced his receiver.

4. In a system according to claim 3 wherein the relay is operated under control of the calling subscriber upon the initiation of a call, and held operated for the duration of the call under control of the calling subscriber and in the circuit of the meter, while when the calling subscriber disconnects the relay is held energized in the meter operating circuit alone.

5. In an automatic telephone system, a main and a subsidiary exchange,- a trunk line extending between said exchanges, means controlled by a calling subscriber for establishing a connection over said trunk line with a called subscriber in the main exchange, a meter at the main exchange individual to the calling subscriber, a relay at the main exchange associated with said trunk line, said relay controlled by said calling subscriber and operated to maintain the established connection over said trunk line, means responsive to the disconnection of the calling subscriber for operating said meter and for maintaining said relay operated to hold the connection over the trunk line until said metering operation has been completed although the calling subscriber has disconnected, said relay being connected in series with said meter and maintained energized for the duration of the call by current means to which said meter is non-responsive.

6. In anautomatic telephone system, a main and a subsidiary exchange, a trunk line connecting said exchanges, a selector switch in said trunk line at the subsidiary exchange, a relay at the main exchangeassociated with said trunk line, said relay operated responsive to the initiation of a call from a subsidiary exchange subscriber to a main exchange subscriber, means controlled by said relay for operating said selector switch to establish the connection with the calling subscriber, a meter for the calling subscriber at the main exchange, said meter operated responsive to the disconnection of the calling subscriber, and means for holding said relay operated until said metering operation is completed, said relay maintaining the connection over said trunk line and said selector svwtch operated during said metering operation.

7. In a system according to claim 6 wherein the relay is responsive to the initiation of the call to transmit impulses to the selector switch at the subsidiary exchange to operate the same to establish the connection and also serves as a testing relay for said selector to test for the calling line.

8. In an automatic telephone system, a main and a subsidiary exchange, a trunk line extending between said exchanges, means controlled by a calling subscriber in the subsidiary exchange for establishing a connection over said trunk line between the exchanges to another subscriber in the subsidiary exchange, switching mechanism at said main exchange associated with said trunk line and operated to control the setting up of the connection, a meter at the main exchange for each of said subsidiary subscribers, the meter of said calling subscriber selected and connected up by said switching mechanism, and means for operating the selected calling subscribers meter.

9. In a system according to claim 8 wherein the switching mechanism controlling the selecting and connecting up of the meter of the calling subsidiary subscriber also is operated to determine whether the call is to be extended to another local subsidiary subscriber or to a main exchange subscriber.

10. In an automatic telephone system, a main and a subsidiary exchange, a trunk line extending between said exchanges, means controlled by a calling subscriber in the subsidiary exchange for establishing a connection over said trunk line between the exchanges to another subscriber in the subsidiary exchange, switching mechanism at said main exchange associated with said trunk line and operated to control the setting up of the connection, a meter at the main exchange for each of said subsidiary subscribers, the meter of said calling subscriber selected and connected up by said switching mechanism, and means for operating the selected calling subscribers meter, said switching mechanism comprising a selector switch operable to determine whether the call is to be extended to another local subsidiary subscriber or to a main exchange subscriber, said meter operating means comprising a relay operated only by said switching mechanism in the position it assumes when it determines that a call is to be extended from one subsidiary subscriber to another subsidiary subscriber.

11. In an automatic telephone system, a main and a subsidiary exchange, a trunk line extending between said exchanges, means controlled by a calling subscriber in the subsidiary exchange for establishing a connection over said trunk line between the exchanges to another subscriber in the subsidiary exchange, switching mechanism at said main exchange associated with said trunk line and operated to control the setting up of the connection, a meter at the main exchange for each of said subsidiary subscribers, the meter of said calling subscriber selected and connected up by said switching mechanism, means for operatingthe selected calling subscribers meter, and a relay at the main exchange operated responsive to the answering of the called subsidiary subscriber for operating the calling subsidiary subscribers meter.

12. In a measured service telephone system, a main exchange, a sub-exchange, a trunk line connecting said exchanges, a finder switch in the sub-exchange, sub-exchange subscribers lines terminating in the banks of said finder switch in the sub-exchange, means responsive to the initiation of a call by one of said subscribers lines for operating said finder switch to connect said trunk line to the calling line, an auxiliary switch individual to said trunk line in the main exchange, a meter individual to each said subexchange subscribers line terminating in the banks of said auxiliary switch, and means for operating said auxiliary switch in synchronism with said finder switch to select the meter individual to the calling subscribers line.

13. In a measured service telephone system, a main exchange, a sub-exchange, a trunk line connecting said exchanges, a finder switch in the sub-exchange, sub-exchange subscribers lines terminating in the banks of said finder switch in the sub-exchange, means responsive to the initiation of a call by one of said subscribers lines for operating said finder switch to connect said trunk line to the calling line, an auxiliary switch individual to said-trunk line in the main exchange, a meter individual to each said subexchange subscribers line terminating in the banks of said auxiliary switch, means for operating said auxiliary switch in synchronism with said finder switch to select the meter individual to the calling subscribers line, means for completing the connection over said trunk line to a called subscribers line, and means for thereafter operating the selected meter individual to said calling subscriber to charge for the completed connection.

EDUARD WOCHINGER.

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