US1572859A - Telephone system - Google Patents

Description

Feb. 9 1926.

E. HORN ET AL TELEPHONE SYSTEM 7 File p v, 1925 7 Sheets-Sheet 1 vvvv --Inuemc rs,-. Eff? Hgrn W Feb. 9 1926.

'7 Sheets-Sheet 2 E. HORN ET AL TELEPHONE SYSTEM Flled Sept 7, 1925 IITTEFZTE-P Erna urn La/ A %W HIT?- Feb. 9, 1926. 1,572,859

E; HORN ET AL TELEPHONE SYSTEM Filed Sept. '7, 1923 7 Sheets-Sheet 5 fez m Feb. 9 1926. I 1,572,859 E. HORN ET AL TELEPHONE SYSTEM Filed p v, 1923 7 Sheets--Shee1; -4

! zVlV Feb. 9,1926. 1,572,859

E. HORN ET AL TELEPHONE-SIYSTEM Filed Sept. '7, 1923 7 Sheets-Sheet 5' Err E. HORN ET AL TELEPHONE SYSTEM Feb. 9 ,192e.

Filed P '7, 1923 '7 Sheets-Sheet. 6'

Erns Huga E. HORN ET AL TELEPHONE sYsT u Fiiled Sept. 1923 '7, Sheets-Sheet '7 v I Emma's- Er'rfii HD2117? Patented Feb. 9, I926.

UNITED STATES 1,572,859 PATENT OFFICE.

ERNST HORN, OF BERLIN, AND MAX LANGER, F HERMSDORF, GERMANY, ASSIGNQRS TO SIEMENS & HALSKE AKTIENGESELLSCHAFT, OF WERNERWERK, SIEMENS- STADT, NEAR. BERLIN, GERMANY.

TELEPHONE SYSTEM.

Application filed September 7, 19%3. Serial No. 661,43).

T 0 all whom it may concern:

Bi it known that we, ERNST HORN and MAX LANGER, German citizens, and residents, respectively, of 16 Kulmtn, Berlin,

Germany, and 58 Rodernstn, Hermsdorf, Germany, have invented certain new and useful Improvements in Telephone Systems, of which the following is. a specification.

In automatic telephone systems it is known to automatically release a connection after the expiration of a predetermined time. The present invention relates'to the application of this arrangement to a large telephone area having several exchanges and different trafiic zones. Calls to distant exchanges located in, another trailic zone are expensive calls, for which an increased fee is charged. Owing-to the length of the trunk lines required, it is necessary for reasons of economy to keep the numberof these trunklines as small as possible since the commercial efficiency of the system is largely influenced by the cost of these trunk lines. Hence it is necessary to use the trunk lines for as many calls as possible.

According to the invention therefore the established connections are automatically released by switching devices at the connecting devices or trunk lines after a predeter mined time, which is dependent on the value of the call. The maximum duration of inexpensive calls (i. e. calls to adjacent exchanges). is therefore greater than the mayimum duration of expensivecalls.

This application lso discloses various novel auxiliary switcli circuit arrangements which are claimed in a pendingapplication of Horn, Serial No. 661,445, filed September The drawings show onemethod of carrying out the invention.

In Figs. 1 to 4 are shown the circuits con;

cerned in setting up the different connections. I K

Fig. 5 shows the position of the exchanges in a telephone area. HA is the main exchange, while the connected sub-exchanges are UAI-UAVL Fig. 6 shows the connection between the auxiliary digit switch MS and the zone switch ZS ofthe meter operating devices, which are associated with the sub-exchange UAI. 4

Fig. 7 shows the connection of the auxilselector to set itself one free II'.V

\Vhen this has been done, the following ciruit is established: earth, battery, contact 1r windings I and TI of relay T wiper 2, contacts 3, 41: relay R earth. The. relay T in known manner stops the preselector, disconnects" the calling relay It, at the contacts 5 and 6t, and connects through the speaking leads (1,?) at the contacts 7 and 8t,. At the second preselecto-r IlLVVV the operated relay R at contact 9') closes the circuit of the driving magnet D and at contact 101*, prepares the energizing circuit for the test relay T The circuit of the driving magnet extends as follows: earth, battery, contacts 9r,. 11a, magnet 13,, con-' tacts 12d, 1325,, earth. The following circuit is established when the second preselector IIVTV, finds a free repeater Ue and associated therewith a free trunk line VL, leading to the main exchange HA: earth, batterv, contact 1073, windings Land 11 of relay T contact-Mu, wiper 15, contact 16,

loadlT, contact 188, winding I of relay C contact 19s,, earth. The relays. T and C operate. The relay T at contact 13t opens the circuit of the drlvlng magnet D,, at con tact 152 short circuits its hlgh resistance ",winding and switches through the testing and blocking lead from the first preselector LVVV, to the repeater U6 and simultaneous- 1v disconnects the relay R at contact 425 Furthermore at the contacts 20 and Qlt the speaking leads are switched through to the feeding bridge at the repeater Ue, which comprises the relays A, and B, whereupon both these relays operate. I

Atthe repeater, the relay C closes its contact 22 and thus prepares a holding circuit 7 over its winding II. Furthermore at contact 230, the impulse contact 25a, of rela A, isconnected to the lead 24 of the trun line VL,. The operated relay A, opens the ter operates, opens its contacts 19, 30 and 33 0, and closes its contacts 31- and 3211,. The closure of the contact 320, causes the rotary magnetI D of the auxiliary switch MS, to be connected up earth, contacts 320,, 34%, wiper 35, contact 36, magnet. D (ms,),

battery, earth. The wiper 35 is moved onto the second contact 37 and thereby the following circuit is closed earth, contacts 321),,

34 11 wiper 35, contact 37 ,lead 38, winding 39 of the repeater, contact 401),, lead 41 of the trunk line VI contacts 420,, 43hr, relay V winding I, contact 44 of the auxiliary switch MS wiper 45, resistance 46', battery, earth. The relay V, operates, opens its contact 4611 and closes its contacts 471),, 481),, 4942,.and 5011,. At contact 4842,, the ro- 1 tary magnet D (ms f of the auxiliary digit switch MS is connected to the impulse contact 51 of a relay A While at the contact 491),, the first group selector of the main exchange is taken into use'over the following circuit: earth, contact 490,, relay 0,, resistance 52, contact 53s,, lead 54, ofi normal contact 55k of the firstgroup selector I.GW,, winding I of relay B winding 1 of relay C battery, earth. The relays C (Fig. 2) as well as B, and C, (Fig. 3)- operate. The

relay 0, closes the, contact 560 located in.

parallel with 491),, opens the contact 420,, and closes the contacts 57 and 580 At contact 570 the lead 41 is. connected with the lead 59 to the first group selector I.GW,,' while at contact 580 the relay V, is main-.

tained energized, after its original energizing circuit is opened at contact 420 The holding circuit, extends as follows: earth, battery, resistance 46', wiper 45, contact .44, winding I of relay V lead 60, normal contact 61, wiper,62, contact 580 earth. At the first group selector IGW, the relay C, by closing the contact 630 repares-a holding circuit over both its windings I and II, which becomes operative as soon as the contact 551: is opened at the first step .Of the group selector. Theaelay B, .at its contacts 64 and 656 connec the relay A, to thelead 66, and connects the windin II of relay B to. the lead 59. The impu see. of the first trai f transmitted by thecalling subscriber, beside; operating the first group selector the short circuit -tacts and 71, respectively. When the re- LGW, located at the main exchange, also operate the auxiliary digit switch MS locatedin front of this grou selector, and the the same trafiic zone as the sub exchange- UAI. If for instance the first train of impulses comprises three impulses, then all the three numericalswitches (I.GW,,, MS,, M8 are moved on three steps.'- The .impulses are sent in known manner by interrupting the loop at the calling subscribcrs station, so that the relays A, and B, release at each impulse and the relay A, closes its impulse contacts 2552, and 2 8a,. The circuits for.operating the difierent apparatus extend as follows:

1. For the auxiliary digit switch MS, in the sub-exchange: earth, contacts 320,, 67/; 28:1,, 36, magnet D battery, earth.

2. For the impulse receivin relays A (Fig. 2) and A (Fig. 3) in t e main exchange: earth, contacts 25a,, (Fig. 1) 230,,

lead 24, thence over relay A contact 502),, resistance 68, battery, earth, and also thence over contact 6%,, lead 66, contact 641),, relay A,, battery, earth. i

The relay A in known manner brings. aboutthe setting-of LGI V, on the third level. The relay A (Fig. 2 closes the cirlciiit for the driving magnet 3 (mm) as follows: earth, contact 51a ,windin II'of-relay V contact 482),, magnet D ma batter of impulses the wipers 45 and 62 of the auxiliary digit switch MS stand 'on' the conlay V, has released, it cannot be again energized during the further setting u of the connection. It should however here be noted that as soon as the relay C is energized, the, relay U is also energized as follows over its win'din I: 'earth, contact 720,, winding I of relay il contact 73hr, driving magnet D, of the counting switch Z8 battery,- earth. The magnet D, is not ener- -gized owing to the high resistance of Winding I of relay U The relay IT, has therefore opened its contact 7 4a and thereby prevents the magnet D (ms being connected up after relay V releases.

The transmission of the first, impulse from the calling station and the opening 'of the contact 26a, by the impulse receiving relay A,, causes the removal of the short circuit round the winding I of relay V,. Hence relay V can operate and it opens its con 'tacts34'v,' and 40v,- and closes the contact 744),. Battery is thereby connected over resistance 7 5 to the lead 41 of the trunk line VL, and the relay B, (Fig. 3) is thereby. maintained energized over its winding II as follows: earth, battery, resistance 75, conearth. Hence at. the end of the train tact 74o lead 41, contact 570,, normal contact. 76 and wiper 77 of the switch Z8 junction point 7 8, contact 7%,, lead 59,'con tact 65b winding II of relay B earth.

The relay B, is also connected to the junc the connection is completed by the positioning of the other numerical switches (e.

the ILGVV, and LVV, shown in Fig. 3).

It is assumed that the final selector LVV, is provided with a sideswitch and that the impulse relays A and B, are disconnected till after the transmission of the trains of impulses for operating the driving magnets. It is also assumed that position 13 is the speaking position of the side switch, into which it goes after the wanted subscriber Tn has answered and in which position a feeding relay Y for the subscriber Tn, is connected up. In position 13 of the s de switch, battery is connected to the lead'82 over a resistance and the side switch con tact 81, 'so that the relay B, in Fig. is energized as follows: earth, battery, resistance '80, side switch contact 81 (position 13), lead 82, contact 83 and wiper 84 of the second group selector H.GW,, contact 85;) contact 86 and wiper 87 of the first group selector T.GW,, COntflClIf 881),, lead 59, contact 79t junction point '7 8, relay B earth. The relay B, operates and causes the switch ZS, to move on to the next contact since the circuit for the driving magnet D, (2311) is closed as follows: earth, interrupter 89, contact 907),, 0d normal contact 91k2sTLof the switch ZS,, magnet D, (2811) battery, earth. Hence the wiper 7] of ZS, is moved to the contact 92. The magnet D cannot be again operated, since the contact 91152811 has now been opened. The relay l3, furthermore at its contact 936, connects earth to the relay A, "In addition the relay S, is connected over contact 104?), to the lead 54. The relay S, operates, opens its contact 538, and closes its contacts 998, and 1128,. At the contact 1128, the relay U, is maintained energized over its winding IT.

To return new to the circuit changes, which take place in the calling sub-exchange UAI: it has already been described how the first train of impulses, whichoperated the first group selector I.GW,, alsolmoved on the digit switch M8,, for instance to the contact 94. At the end of this train of impulses, the relay U, is energized as follows:

earth, contacts 321),, 34 0,, wiper 35, contact,

94-, relay lU, contacts 119; and 1200,, bat tery, earth. The relavU, connects itself in a holding circuit at its contact 121%,; this circuit can, however, only be closed so long net .D (cell), battery, earth.

as local connecting devices LlV, accessible:

switch MS, to be operated in the same mannor as did the first train of impulses. Thereby the Wiper 35 reaches for instance the contact 118. After the release of relay V, due to the prolonged short circuit of its winding ll at contact 526a,, the relay F is energized: earth, contacts 327),, 3411,, wiper 35, contact 118, windings Land II of relay F, battery, earth. The relay F closes its contact 95 and thereby connects itself in a-holding circuit dependent on the contact 9611, of the slow releasing relay V,. Furthermore the relay F opens the contact 67,, so that the rotary magnet D, (1718,) cannot be operated further by other trainsof impulses.

If at the end of the conversation the wanted subscriber is the first to hang up, the side switchof the final selector LW reaches the position 14. The circuit for the relay 1%, (Fig. 2) is however maintainedfsince in this position also the contact 81 (Fig. 3) is closed. When the calling subscriber 'T'n,

(Fig. 1) also hangs up his receiver, the reclosed 'earth, battery: windingll of relay, ,V,, contact'970,, lead 24, winding 1 of relay A-,, contact 93b,. earth, so that the relay V, remains energized in this circuit. The relay A, also operates and gives a metering impulse to the meter impulse repeating relay ZR at the repeater U6 of the exchange llAl over the following route: earth, battery,

contacts 998,, 100a,, relay HR, contact 570,,

lead 41, contacts 402),, 980,, relay ZR, contact- 31 0,, earth. The relay ZR closcs its contact 1012 and thereby connects the low resistance 102 in parallel with the high resistance 103 to the lead 17 coming from .the second preselector ll.VlV,. Thereby the current flowing over the meter Z at the first preselector TVVV, is increased to such an extent that the meter .can operate and the conversationcan be metered. After the"relay HR has been energized, the driving magnet D (2811) of the switch ZS, is energized as follows: earth, contacts 510,, 1057193 mag- The relay HR at its contact 106M short circuits the relay A,,hence it releases. The wiper 77 is moved on one step by themagnet D and reaches the contact 107. The relay B is now short circuited because earth is connected to the junction point 78 over the contact 580 manner. \Vhen the contact 936 is opened,

the relay V at the repeater U is de-energized and releases. I

The digit switches MS and MS as well as the counting switch ZS are released in 'the foll owing manner:

After the reIease of relay V ,.the relays V and 18 are energized in the following lay V ofi' normal contact 107767729 of the digit switch MS winding II of relay S, battery, earth. Botlbthe relays S and V operate and close their contacts 108 2.. and 109.9.

the rotary magnet D (ms earth, contacts 110 0 1098,1081) 67;", 28a,, 36, magnet D battery, earth. The magnet I) operates, moves on the digit switch and at its contact 111([ short circuits the relay V The relay V releases and opens its contact 108, whereby the magnet D releases and opens the contact 111. The relay-Y now again operatesland again closes ;the contact 1080 This -cycle.is repeated until the, auxiliary digit switch reaches its normal position, I wherein the off-normal contact 1077mm, is opened. After the release of the rotary magnet D it is impossible'for the relay V to again energize.

The relay U. .i Fig. 2, was as already mentioned, maintained energized during conversation over-a contact 112 of relay S and its winding II. Since the relay S was de-energized after the release of relay B the relay U is also de-energized and closes the following circuit for theimagnet I) (mag: earth, battery, magnet 1),, contact e64) off normal contact 113767768 of the digit switch MS contact 74%,, winding II of relay HR, earth. The magnet D operates and closes the following circuit: earth, battery,-

winding II of relay U contact 1l4d winding III of relay HR, earth. The relay U at contact 7411- opens the circuit of the magnet D whereupon the magnet releases and opens the circuit of the relay U This cycle is repeated until the digit switch reaches its normal position, H in which i the contact 11:31am; is opened.

The switch ZSyis moved into ,itshnormal.

osition at the same time as the 'digit switch K/[S since the circuit of driving magnet D (2811) is closed as follows: earth, battery,

magnet .Dl, ofi riorm'al contact 1157702811, norsucceeding switches are released in known route: earth, contact 332),, winding II of re- "Thereby the following-circuit is closed for- 46 o,, 113701128 '74u relay opens the contact 11401,.-

mal contact 11670231, contact 11711,, winding II of relay HR, eartlnv The magnet D, also closes a. contact 118d, in the circuit of winding 11 of relay U so that the moving on-of the switch ZS, is dependent only on the operation of the magnet D and the relay U The drivingcircuit for the magnet D, is finally opened when the switch ZS reaches its normal position since the contact llfilt'zs is then opened.

Consideration will now be given to the casewhen a connection is set up with a subscriber who is connected to an exchange located in a different trafiic zone. Exchanges for which a zone payment has to be made are, for instance, reached over the eighth level of the first numerical. switch. Hence the first group selector is set on the eighth level, in which it takes into use a free trunk line V L The continuation of the trunk line VL is indicated by VL in Figure-3. At the point (200, 201, 202) where these two lines meet,a trunk line VL, is connected coming from the bank contacts of those first numerica-l switches ,(LGW that are accessible to subscribers of the main exchange. Be-

tween the contacts 208, 204 and 2.05 at the last mentioned first numerical switch LGrW and'the meeting points 200, 201' and 202 are located'the meter operating devices that are only operated for calls originated by the nialn exchange subscribers. These meter operating devicesf '(MS ZS ,/ZS are therefore not employed for theqaresent connection. When the first group selector LGrW is set on the eighthlevel, the digit switch MS is at the same time set on to the eighth contact, which is for instance the contact lls. After the relay V, has released, the relay F is energized as before and prevents the rotary magnet D being operated by further trains of lmpulses.

The wiper 45 of the digit switch MS is likewise set on to the eighth contact, which in- Fig. 2-is designated by 121. The winding III of relay HR is short circuited for the dui'ation ofthe impulse train by the contact 4742 The relay HR is however energized upon the release of the relay V earth, battery, resistance 46, wiper 45, contact 121, relay HR, winding III, earth. The relay HR operates and by opening the con tact 73hr interrupts ,the clrcuit over the winding. I of rela U The relay U releasesv and closes t e contact 74%, whereby the following circuit is closed for the magnet D.,,: earth, battery, ma net 1),, contacts fin, winding 11, earth. The magnet D by closing its contact 114d energizes the relay I I over its winding II in series with the winding III ofrelay HR. The relayU operates. and opens the contact 7.411,, where y the circuit for the magnetD is opened, 50 that it de-energizes and Thereupon the reated over the contact 1046 in the manner lay U releases and closes contact Hu This cycle is repeated until the wiper reaches the contact 122'. This contact cannot be reached b'y the first train of impulses trans mitted by the calling subscriber which will never exceed ten. As soon as the wiper 45 reaches the contact 122, the following circuit is established: earth, battery, resistance 4G, wiper 45, contact 122, winding 1 of relay V lead 60, contact 123, wiper (32, contact 580,, earth. The relay V operates, opens the circuit for the automatic rotation of the "digit switch MS .by opening the contact 4612 and at contact 4811 connects the rotary magnet D to the impulse contact 51%. The digit switch MS has now been brought into aposition in which it can be opera'ted,by the second train of impulses. The transmission of the second train of impulses causes the relay A, to be operated in the manner already described, and the relay at its contact 5100 sets the rotary magnet D in operation. The circuit of the rotary magnet D contains the winding 11 of relay V so that this relay remains energized for the duration of the train of impulses. The energization of the relay V, after the switch 45 has been set on the con tact 122 a'lsocauscs the relay HR- to release, thus preventing the rotary magnet 1),, of the switch ZS being operated by the relay A Let it be assumed thatthe second train of impulses comprises only a single impulse and hence the wiper 62 of the digit switch MS has been set on the contact 124, over which is connected u thereafter wiper 125 of the zone switch Z After the connection has been set up and the wanted subscriber has answered in the manner already described, the relay B is energized and causes the switch ZS to take one step as before, hence the wiper 7 7 of ZS stands on contact 92. Furthermore the contacts 126 and 127 are closed in this position of ZS Therelay S, has been again operalready described and has connected up the relay U, over .its winding H so that the contact 128w is opened and the contact 129w is closed.

The meter operating device has a time switch associated with it, which is moved on by the magnet D at fixed intervals of time. After the contact 12921, has been *closed, the time switch is moved out of its normalposition' since the magnet D is energized as follows: earth, interrupter 130, contacts 1316,, 1262s,, normal contact 13226, contact 129a,, rotary magnet D (ze), batt'ery, earth. :At the firststep of the time switch ZE the contact 132.26 is opened and the contact 133% is closed. I

It is assumed in thepresent example that r the time switch has 36 contact positions and is moved on by a time. contact 134u7:, which is closed every 5 seconds; it may for instance be operated by an electric clock. Hence one rotation of the time switch correspo ids to a duration of 3 minutes, which has been assumed to be a unit of time for the calls. The contact. 134is closed shortly before the time switch has completed a rotation. Thereby the corresponding subscribers are given a buzzer tone, from which they recognize that a 3 minute period will he completed in a r'ew seconds and that fursubscribers. When the time switch upon its rotation reaches the last contact (the 36th) the driving magnet D of the zone switch ZS, is energized as follows: earth, 135, contact 713625,, wiper 1337', contact 138%, magnet D (281), battery, earth. The zone switch ZS, is moved on one step. The circuit changes just described are repeated at each rotation of the time switch Zl l.

The zone switch ZS, which is controlled bythe time switch Ze, has its contacts connected with the contacts of the counting switch ZS The wiper 125 of ZS, is connected up for calls to the second traitic zone. The normal contact 139 is connected with the fourth contact 140 of the switch ZS Since this switch is set on the first contact 92 as already mentioned, it has to take three steps before the wiper 77 reaches the contact' 140. Hence for connections in the traflic zone II, three metering impulses have to be transmittedfor each conversation unit. When the zone switch ZS, has been advanced onestepat the end of the first unit of time, the wiper 125 stands on the contact 141 which is connected with the seventh contact 142 of ZS,.

For calls to the traflic zone III the wiper 143 is connected up, as has been assumed in Fig. 2. The normal contact 144, upon which this wiper is standing, is connected to the sixth contact145 of ZS, Hence for calls to the third tratlic zone five impulses are trans mitted for each time unit.

For calls to the fourth trafiic zone, for which the wiper 146 of ZS, is connected up,

seven metering impulses have to be trans.

mittedfor each time unit, and for calls to the fifth traffic zone nine metering impulses have to be transmitted.

In the present system, devices are also provided for limiting: the duration. .ofsthe difi'erent calls according to their value. Thisis achieved by means of the; switch Z8 In the present example this switch has 32 positions. The last five contacts 147 to 148 are multipled together and are connected with a relay T Since the zone switch ZS, is always moved on one step at the end of a three minute period, the wiper 125 ofthe zone switch ZS reaches the ninth contact 149 at the expiration of 8 time units in the case of calls to the traflic zone II; the contact 149 is connected to the contact 147 of the switch ZS When the call has lasted so long, i. e. 24 minutes, the relay T is energized in the following circuit: earth, contact 580 wiper 62, contact 124, wiper 125, contact 149, lead 150, contact 147, relay T battery, earth. The relay T operates, opens its contact 136 and connects the buzzer tone at. its contact 151 to the wind- 111g; II of the relays A and B .The calling subscriber therefore immediately receives the buzzer tone.- In addition however the contacts 69 and 7 9t are also opened and the contact 15211, is closed, hence the speaking connection is interrupted. Nevertheless, however, the relay B is maintained mnergized over the contact 1525 and the resistance 68. If a connection has been set up to the traflic zone V, then the wiper 62 of the digit switch MS stands on the contact 153, so that the wiper 154 isconnected up. The normal contact 155 of this switch is connected with the tenth contact 156 of the switch ZS It is assumed that for a connectionof such high value the max mum duration of a conversation is two units of time. The wiper 154' of the switch ZS is at-the'end of the first time unit moved, on to the contact 157, which is connected with the contact 158ofZS At the end of the sec- )ond time unit the driving magnet D .of ZS againsreceives an impulse and. the wiper 154 reaches the contact 159, which is connected with-the contact 160 of ZS The relay T is then at once energized and brings about the circuit changes already described. V When the calling subscriber hahgs up his receiver at the end of a COIIVGI'SfitlOIT- in one ofthe traffic zones '11 to V the relay A is energized as already described and transmits a metering impulse over the lead 41 to the metering repeat relay ZR in- Fig. 1. Thereby the relay HR is againcenergized, and by closing the contact 105 connects the driving magnet D of ZS -to the impulse contact 51a, The relay HR at its contact 10672.1" short circuits the relay? A so that the relay A, slowly releases and opensthe contact 51a in the circuit of the magnet D and also the contact 100a in the clrcuit of the relays HR and ZR.

The magnet D, releases and-after a little while the slow acting relay'HR also releases. Thereupon the relay A again operates and causes the transmission of a second metering impulse and the moving on of the switch ZS This cycle is repeated until the wiper 77 reaches a contact, over which the relay B is short circuited. If the zone switch ZS was moved on three times during a conversation in the second trafiic zone, the wiper 125' stands on the contact 161, which is connected with the contact 162 of the switch ZS When the Wiper 77 reaches this con tact, the relay B is short circuited, since earth is connected to the wiper 77 over the contact.58c wiper 62, contact 124, wiper 125, contacts 161 and 162. The relay B releases, opens contacts 93 and 1045 where" by the relays C and S are permanently'deenergized. l i

As soon as the transmission of metering impulses commences, the contact 12728,. was opened this contact being closed only in the first position of the switch ZS that is when the wiper 77 stands on the contact 92. Thus the operation of the time switch Z0 is pree vented during meter impulse transmission. The switches MS ZS and Z0 are moved on into their normal position when the relay is de-energized after the release of relays B and S The moving on of the time switch Z6 is effected by the alternate operation of the drivin magnet D and .the relay U The c-ircult of the driving magnet D of the time switch Z6 is closed over: earth, battery, magnet D contact 12814,, oif normal contact 1707026, relay HR, twinding II, earth. The magnet D closes its contact I 1710i and thereby energizes the relay U which opens the contact 12810,, so that D is de-energized. The relay U is now de-energized and again closes its contact 128%,, so that the magnet D receives another impulse. The contact 170kze is opened when the time switch Ze reaches its normal position. The circuit for the driving magnet D, of the zone switchZS is closed over: earth, battery, magnet D contacts 1727020, 117 u,,, winding II of relay HR, earth. The magnet D energizesthe relay U over its contact 17 3d,. The contact 1727628 is opened 115 when the zone switch ZS, reaches s normal position and the magnet D cannot again e energized. The circuits for the. magnets D and D which movethe digit switch MS,- and. the zone switch ,ZS, respectively at there eaterlle (Fig. 1).. As already mentione the relay S is energized'over' the 01f normal contact 1071mm during thereleasing motion of the digit switch S When the digit switch MS reaches its normal position, the contact 1077mm is opened and the contact 17575-1228 is closed. It at this time the rela HR in Fig. 3 is still energized, the relay S is maintained energized as follows: earth, resistance 176, contacts 146M, 420,, lead 41, contact 175kms relay S, battery, earth; The relay S therefore maintains its contact 18sopen, so that it is impossible for the trunk line VL to be taken into use by a testing second preselector II.VlV

If a call is set up between the subscriber Tn, of the main exchange HA (Fig. 4E) and a subscriber of an exchange accessible over the trunk line VL the relays C A and B are energized after the preselecting devices IVV (Fig; 4:) and II.V\V have been positioned. Thereafter, in known manner the first numerical switch lLGrlV is set on a levelto which the trunk line VL, is connected. has been found, the following circuit is established: earth, windings I and II of relay P contact 2064),, wiper 207,'contacts 205 and 2082),, relay C lead 209 of the trunk line VL junction point 202, lead 210 of the trunkline VL to battery over switching devices of the selectors in the distant exchange. The relay C closes the contact 2110 located in parallel with the contact 208i; and energizes the relay V over the contact 2120,, the contact 213 of the digit switch MS and the wiper 214, Relay V opens the contact 5208i) and at contact 215e,,

connects the relay A, to battery over the resistance 216. Between the trunk lines VL and VL, lie the switching members of the meter opera-tingdevices, comprising the switching devices MS ZS, and ZS The method of operating these meter operating devices corresponds to that shown in Fig. 2, so that it is unnecessary to describe the circuit changes. The relay l8, corresponds to the relay l3, and the relay 'I corresponds to the relay T lVhat we claim is:

1. In a measured service telephone sys- When such a free trunk line I tem, a calling line located in one exchange,

- with.

2. In a telephone system, a plurality of exchanges, lines terminating in said exchanges, means for transmitting impulses from a calling line in one exchange to position automatic switches to complete a connection to a desired line'in another exchange, and an automatic switch responsive to the impulses transmitted to one of the switches used in setting up a connection to determine the maximum time the connec tion can be maintained.

3. In a telephone system, a plurality of exchanges, lines terminating in said exchanges, means :tor transmitting impulses from a calling line .in one exchange to position automatic switches to complete a connection to a desired line in another exchange, and an automatic switch responsive to the impulses transmitted to one of the switches used in setting up a connection to determine the maximum time' the connection can be maintained,

.' 4. In atelephone system, a telephoneexchange, a calling line equipped with a meter, means controlled from said calling line for extending connections to called lines located in other exchanges, and Irieans for automatically releasing a' ,connection after the expiration of a predetermined period, said means comprising an automatic switch used in operating the said meter a number of times dependent on the value of the connection set up.

-Signed by me at Berlin, Germany, this 17th day of August, 1923.

ERNST Home 17th day of'August, 1923.

MAX LANGER.

o Signed by me at Berlin, Germanyythis

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