US1644968A - Measured-service telephone system - Google Patents

Description

Oct. 11, 1927. 1,644,968

J. WICKS MEASURED SERVICE TELEPHGNE SYSTEM Original Filed May 25. 1921 4 Sheets-Sheet l N s s \L LR lq A m @PIP q 1% l CQZQCJ'IF Il Q lily/mw j Q l j M flu-gp 1927. Oct 11 J. wlcKs MEASURED SERVICE TELEPHONE SYSTEM 4 Sheefs-Sheet Original Filed May 25. 1921 m um@ -Inuen m7- f Jhn Hunks Oct. 11,1927.

J. wlcKs MEASURED SERVICE TELEPHONE SYSTEM NNN 4 Sheets-Sheet 5` Original Filed May 25. 1921 Jnhn Hmks 5%; Z. .EU-

J. WICKS MEASURED SERVICE TELEPHONE SYSTEM Oct. 11, 1927. 1,644,968

original Filed May 2:3.'1921 4 sheets-sheet 4 Jahn MURE mengen oet. 11, 1927.

UNITED STATES PATENT i oFElcE.

JOHN WICKS, OF OAK PARK, ILLINOIS, ASSIGNOB, BY MESNE'ASSIGNMENTS, T0 AUTO- MATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

MEASURED-SERVICE TELEPHONE SYSTEM.

Application 'led Hay 23, 1921,.8er1a1 No. 471,775. Renewed January 5&2, 1826.

4The present invention relates in general to v measured service telephone systems, and more. particularly, vto automatic measured service systems of the type in which aystation apparatus is provided at each su scribers'station requiring the deposit of a coin for each successful connection In one well known arrangement, thecalling device at the subscribers "substation is normallyinoperative to controll the central olice switches and it is 'only by first deposit-f ing a coin that the subscriber is enabled to render his sender operative to control the. switches in the exchange to set up ay connection. Thereafter the coin deposited is either collected or refunded depending upon whether the subscriber called responds or not. If the party called is an oilicial of the telephone company or an operator the coin is refunded in any case.

Certain improvements have been devised in the above mentioned system whereby a calling subscriber must deposit a coin before making a call providedvv he desires aconnection -with another subscriber, while if he desiresl a connection with an operator no coin is required to be deposited. A particular object of the inventionis to provide new circuits for a type of repeater which is used in such an improved system'whereby the operationsfof the switch are rendered more positive and the impulsing circuits through the repeater are greatly improved. A special feature incorporated into this repeater circuit is an arrangement so that if a recordino operator is called .she is given a discriminatlng tone in order to inform her whether the calling subscriber is limited as to certain vservices or connections.

'According to another feature in the repeater if a calling subscriberl attempts to make a connection with another subscriber without first depositing a' coin he is unable to do so and he cannot, without first replacing his receiver, loperate the central oilice switches beyond a certain point even if, aft/er attemptin to extend a connection, he depos1ts t e required coin. This provision, of course, eliminates the possibility of wrong numbers being called on account of one 4or more digits being absorbed. a

Still another feature of the invention is to so arrange the repeater circuits that the trunk selecting o erations of the subscribersy rotary line switc es which have access to the repeaters are rendered much more positive a repeater not function properly or the c 'oin collecting mechanisml and subscribers subi station not be inpro er condition, an alarm is given to the atten ant, who may then ascertain 'what is the trouble. v

l Another feature of the invention relates to the provision of a meter oneach subscribers line Whichregisters each completedcharged call. This provision. is made so thatl a checkmay be had against the amount of coins collected by the subscribers paystation apparatus.

Still another feature relates to 'the' rowhereby theoperation of the connector in selecting an idle line in a group of lines is rendered more positive. y

There are certain Iother features of the invention not now specifically mentioned which Will be described together with the foregoing hereinafter with reference to the accompanying drawings. v g Referring now to the drawings comprisin Figs. 1 4, inclusive, the general scheme 'o the system shoWn-th'ereinjmay be briefly dey scribed as follows: The substation A, Fig.

l, is ofthe ordinary .automatic type having the usual talking instrumentalities, and an impulse sender S `Being a-measured service substation there is also provided a well known type of coin collecting mechanism which may be of the type shown' and dey scribed in the-U. S..patent toForsberg No. 1,043,219, granted Nov. 5, 1912.

The line 'conductors 11 and' 12 extend from" the subscribers' substation tothe exchange terminating at the lat-ter point in an individual trunkselecting or ,line switch C. This switch is of the well known rotary ty e in which the wipers have no normal position.

always remaining in engagement with the bank contacts associated with the trunk line last used; and whose function is to extend the line when callin to a trunk line which ter u minates in an id e first selector switch. One of the trunk lines to which theline switch C, in common with a plurality of other line switches, has access isshown extending to the firstl selector E', Fig. 3. The relay equipment in Fig. 2 indicated by reference char-` acter D is a repeater, there being one such repeater inserted in each first selector trunk. At T is shown a discriminating tone machine whose function is to give a discriminating tone to a recording operator should one be called by the subscriber, in order to inform her of his status, that is, whether. he is entilted to certain connections or not.

Associated with the repeater are the alarm si al and supervisory circuits shown in Flg. 2 which perform the function of noti- 1ng the attendant in the exchange imme iliately anything goes-wrong with the repeater D.

The first selectors are the first in the series of numerical switches which may comprise first selectors, second selectors, and connectors which are used to complete connections between calling and called lines. One of these rst selectors is shown at E, Fig. 3. This switch is of the well known Strowger vertical and rotary type and has access to trunk lines extending to second selectors such as E2 or E8. The second selector E2 is similar to the rst selector E', as is the second selector E, However, the circuits nf the second selector E3 differ slightly from those of the other two switches and this will be explained shortl The rotary connector i-I, Fig. 4, is one of the connector switches accessible to the second selector E8 and is of the well known Strowger vertical and rotary type which may be seized by means of a second selector in order to complete a connection to a called subscriber such as the one shown at A. This connector is capable of selecting an idle line in a group of lines or if all the lines in the group are busy to notify the calling subscriber of this fact. .The substation A is one of the substations to which the connector H has access and may be similar to the one shown at A, although, for convenience, the measured service equipment has been omitted.

It is customary in automatic exchanges to provide a special group of second selectors through the medium of which a calling subscriber may connect with the various .groups of trunk lines extending to the diferent operators and employees of the telephone company, such for example, as the information operators, trouble operators, recording operators, or the wire chief. The special second selectors are generally accessible from a certain level in the regular first selectors. In Fig. 3 a trunk line is shown which terminates in a set of bank contacts in a level of the first selector E and which extends to the second selector E2. The second selector E2 is one of a group of special second selectors which have access to the roups of trunk lines above referred to.

ne of these trunk lines is shown in the drawings and terminates in the recording operators equipment indicated by the reference character C which comprises a group of relays, an induction coil, an answering jack J, and a call signal lamp L.

In order to ex lain the operation of the circuits it will rst be assumed that the subscriber at substation A desires to call the recording o erator at the equipment O, it being ossi le to accomplish this connection without de ositing a coin as was mentioned hereinbe ore. When the receiver is removed at substation A the line relay 26 of the individual line switch C is energized over the two sides of the calling line in series. Relay 26 upon operating, at its armature 4() completes a circuit which includes the switching relay 25 and the motor magnet 27 in series and at its armature 39 connects the test wiper 46 to the above circuit at a point midwa between the switching relay and the sai motor magnet. The operation of the line switch C de ends upon whether the trunk line with which its wipers 44-47, inclusive, are in engagement is busy or not. Assuming this trunk line to be busy there will be a ground potential present upon the test contact engaged by the test wiper 46, the switching relay 25 will be short circuited and the motor magnet 27 being supplied with direct ground via the said test wiper will operate as a buzzer to advance the switch wipers step by step in search of an idle trunk line. However, it will be assumed in the present case when the receiver is removed at substation A the switch wipers 44-47, inclusive, are in engagement with the bank contacts associated with an idle trunk line. Under these conditions, immediately following the energization of the line relay 26 the switching relay 25 not being short circuited will ener ize. Upon energizing, relay 25 disconnects t e line conductors 11 and 12 of the calling substation from the Winding of the line relay 26 and from ground, respectively, and extends them by way of armatures 33 and 36, wipers 44 and 47 bank contacts 52 and 55, conductors 48 and 5l, armatures 145 and 144 and their resting contacts, armatures 160 and 164 and their resting contacts, windings of the differential relay 130, and thence through the winding of the line relay 135 and impedance coil 139.

The line relay 135 of the repeater D is energized over two sides of the calling line in series and at its armature 183 completes the circuit of slow acting relay 136. The latter relay upon energizing, at armature 186 places ground on release trunk conductor 50 by way of the retardation coil 138 thereby establishing a holding circuit for line switch C which extends by way of bank contact 54, test wiper 46, armature 35 and its front contact, through the winding of the switching relay 25,. and thence through the winding of the,

ing line relay 26 has had time to deenergize.

, the winding of the-motor magnet 27 to battery. It will be understood't-hat this holding circuit is completed before the slow `act- A branch of the holding circuit also extends by way ot the private normal conductor 30 to the multipled test contacts in the banks of connector switches which have access to the line of the substation A whereb the said line. 'is protected from intrusion 1n a well known manner. It will be remembered that ground is supplied to the releasetrunk conuctor 5,0 through the xatardation coil 138.

This coil is of very low. resistancev say of about 2% ohms so that the multiples of the test contact `ltaccessible to the other line switches arel made busy. Relay 136 upon I energizing, also completes a circuit for the polarizmg winding ot the electropolarized rela 132 and that Vof the polarizing winding of 't e relay 128, in series with the windingv of relay 141. The electropolarized relays 128 and 132 are so adjusted that current kiow- `ing in theirpolarizing windings does not cause thesel relays to operate their armatures, though after once operating the current flow in the polarized windings Iis lsuihcient to maintain the armatures attracted. Relay 141 is therefore the only relay operated over the above traced circuit. Relay 141, upon energizing, opens a' point in a certain shunt circuit which will be described later.

When the line relay 135 of the repeater D energizesa bridge is closedacross the trunk conductors 200-202, which may be traced as follows: armature 190 and its back con. tact, upper winding of the electropolarized 'relay 132, normally closed springs controlled by armature 172, normallyclosed springs controlled by armature 160, upper winding of the electropolarized relay 128, lower windi ing of the relay 133, front contact and arma- `lture 184, normally closed springs controlled by armature 164i, normally closed springs controlled b armature 173 to trunk conductor 202. v pon the closure of the above traced circuit the line relay 225 of the first selector E is energized. Upon operating,4

relay 225 completes the circuit of the slow actingrelease relay 226 which immediately' operates to prepare the operating circuits of the selector E at armature 238 and at armature 237 places ground on the release trunk conductor 201 through the resistance 240. This ground extends back over the release trunk conductor 201 tothe polarizing Windi ings of the relays 128 and 132.

Therelay 141 is not shortfcircuited at this time as the resistance 240 is high enough to prevent the 'relay winding from beingv shunted: .thus

ground is now supplied-to the polarizing windings of relays 128 and 132 from first selector E .and from the repeater'D.

Before proceeding further with the eX-' planat-ion. attention is called to a shunt cir- -succeeding switches.

cuit aroundarmature y184 and its front contact which, 1t may be mentioned, are the impulse springs of the repeater D which conf springs represented y armature 184 and its working Contact inrepeating impulses.

"The calling subscriber yat substation A may now operate his calling device'in accordance with the two digits which it 1s necessary to call in order tofobtain connection 4 with the recording operator. By the opera? tion of the calling'device S a series of'interru'ptions is produced in the circuit of the linerelay .135 thereby lcausing this relay to deenergize in response to such interruptions, each time opening the previously traced circuit ofthe line relay 225 ofthe first selector E."; At the first deenergization of relay 135 an impulseof current is sent to the slow acting relay 137 whichis energized and remains energized throughout the series of impulses. yRelay 137, upon energizing, completes a circuitv extending fromground by:

way of armaturel191 and its front contact, normally closed springs controlled by arma-v ture 167, and thence vthrough the winding of the relay 129 to battery.` Relay 129 is energized over thiscircuit and, upon operating, establishes a locking circuit for itself at armature 167 and at armatures 165- and 168short circuits the windings ot the differ# ential relay 'Which was previously in-V cluded in the circuit of the line relay 13 5. By this operation the line relay is given a much better impuls'ing circuit. Another result of the energization of relay 137 is that at armature a-direct bridge is placed across the trunk conductors 200 and '202 which does not include the windings of the electropolarized relays 128, 132, and the lower Winding of the relay 133. These circuit clianges aremade in order to'reduce the resistance and impedanceof'the switchv control circuits to a` minimum during the transmission of impulses. Proceeding now tothe operation of the lirst selectorvE, at each deenergization of the line relay 225 an impulse of current is sent to the verticall magnet 232 in series with the slow acting.

relay 227. Magnet 232 operates to raise .the

i switch wipers 2554257, inclusive, step by step until they are'placed opposite-the level of bank contacts in which are terminated tru lines leading to the special group of seco 1d selectors which have access to trunk lines leading to operators positions. The slow acting relay 227 is energized in series with the vertical magnet and maintains its armature attracted throughout the vertical movement of the switch. Upon the first vertical step of the switch a circuit is completed extending from ground on release trunk conductor 244, armature 245 and its front contact, off normal spring 241 and its working contact, and through the winding of the stepping relay 228 to battery. Relay 228, upon energizing, establishes a locking circuit for itself at armature 247 and at armature 248 prepares the circuit of the rotary magnet 231. .At the termination of the vertical movement of the switch, the slow acting relay 227 is deenergized andthe circuit of the rotary magnet 231 is completed. Magnet 231, upon operating, rotates the switch wipers into engagement with the first set of bank contacts in the selected level and at armature 254 opens the locking circuit ot the stepping relay 228 which deenergizes opening the circuit of the rotary magnet 231 which deenergizes also. The further operation of the selector E depends upon whether 0r not the trunk line with which the Wipers 255-257, inclusive, are now in engagement is busy. Assuming this to be the case, there will be a ground potential present upon the test contact engaged by the test wiper 256 and a circuit will be completed extending from the said grounded test contact by way of the test wiper 256, armature 251 and its back contact, armature 254 and its back contact, off'normal spring 241 and its working contact, and through the winding -of the stepping relay 228 to battery. Upon energizing, relay 228 establishes a locking circuit for itself and completes the circuit of the rotary magnet 231. This alternate operation of relay 228 and the rotary magnet 231 will continue until the switch wipers 255-257, inclusive, are rotated into engagement with the bank contacts associated with an idle trunk line `which we will assume are the bank contacts 260-262, inclusive. As this trunk line is idle there will be no ground potential present upon the test contact 261 engaged by the test wiper 256 and no circuit will be completed for the stepping relay 228. The switching relay 229 will now be energized in series with the stepping relay 228 as it is no longer short circuitcd. It may be stated at this point that the switching relay 229 is of such high resistance that the stepping relay 228 is not energized in series with it. Relay229, upon operating, disconnects the incoming trunk conductors 200 and 202, from the windings of the line relay 225 and extends them by Way of armatures 250 and r253, wipers 255 and 257, bank contacts 260 and 262, trunk conductors 267 the slow acting release relay 281. The latter relay, upon energizing, prepares the operating circuits of the selector E2 at armature 292 and at armature 291 places ground on release trunk conductor 268 through the resistance 295 thereby establishing atliolding circuit for the switching relay 229 of the first selector E. This ground also extends by way of the release trunk conductor 201 to the polarizing windings of the relays 128 and 132 but as the resistance 295 is included in this circuit the relay 141 is still maintained energized and the shunt circuit around the impulse springs 184 is open at armature 196.

The calling subscriber may now voperate his calling device in accordance with the second and final digit in the number of the desired operator thereby producing a second series of interruptions in the circuit of the line relay 135 of the repeater D which are repeated by means of the armature 184 to the line relay 280 ot' the second selector E2. The selector E2 is exactly like the selector E and its operation will not be described in detail. lt will suflice to say that the switch shaft is raised step by step until the wipers 310-312, inclusive, stand opposite the level of bank contacts in which are terminated the trunk lines extending to the recording operators position after which the wipers are automatically rotated in search of an idle trunk line. Assuming that thev trunk line shown in the drawings is the first idle trunk line the switch wipers will nally be brought to rest in engagement with bank contacts 313-315, inclusive, whereupon the switching relay 284 will be energized. As a result of the energization of relay 284, the trunk conductors 267 and 269 are disconnected from the windings of the line relay 280 and are extended by way of wipers 310 and 312, bank contacts 313 and 315, to the upper and lower windings of the double Wound relay 320. Relay 320 is therefore energized and completes a circuit for the slow acting relay 321 which, upon energizing, in turn closes the circuit for the lamp signal L and also completes the usual holding circuit for the selectors E and E2 which may be traced as follows: ground by way of front contact and armature 328, through the primary Winding of the induction coil I', through the resistance 316, bank contact 314, test wiper 311, armature 306 and its front contact, where it joins the holding circuit previously described. The switching relays 284 and 229 are maintained energized and' the switches E and E2 are accordingly held in their operated positions.

scriber is entitled to, after operating the listening key in the cord circuit, the recording operator will throw the key K. By this operation the secondary of the induction coil lis connected in bridge of the trunk conductors and the discriminating tone on the c release trunk may be heard by the recording operator over a circuit which includes the secondary of the induction coil l. Ilhe primary of the induction coil ll is energized over a circuit which extends as `follows: from the discriminating tone machine T, terminals 32 and 31, private normal conductor 30, front contact and armature 35, test wiper 46, test contact 5ft, release trunk conductor 50, condenser 144:', conductor 201, front contact and armature 251, test wiper 256, test contact 261, release trunk conductor 268, front contact and armature 306, test vwiper 311, test contact 314, resistance 316,

through the primary inductioncoil I', and armature 328 and its front contact, to ground. It will be noted that in the above circuit there is another path for the current from the tone machine T to take, which may be traced from the conductor 50, through the winding of the retardation coil 138 to ground, by way of armature 186 and its iront contact. However, as this circuit includes the winding of the retardation coil 138 the greater part of the current from the tone machine flows over the previously traced circuit. The class of service to which the calling subscriber is entitled is determined by the particular tone whichl is connected to the private normal conductor of his line and which is induced in the secondary of the induction coil I and is audible to the recording operator. As soon as the recording operator determines the class of service that the calling subscriberis entitled to she will restore the key Ky to normal -so as to communicate'with the calling subscriber. The recording operator may now converse with the calling subscriber 1n order to ascertain his desires. The talking circuit may be traced over the heavy talking conductors and it will be noted that there isa bridge across vthe talking circuit in the repeater which includes a winding of the electropolarized relay 128 and the lower winding of the relay 133. The lower winding of the relay 133 operates asa retardation coil sov that the v transmission eiliciency of the talking circuit is not materially affected by the above mentioned bridge. From thispoint on, the

operation may take any desired course, dependin upon the wants of the subscriber, and wi l not,be described. Disconnection is eected in the usual manner by the han ing up of the receiver at substation A. 'his operation causes the relay 135 in the repeater' D to deenergize with the result that the slow acting relay 136 of the re eater is deenerg1zed to disconnect groan from the holdu ing circuit of the line switch C. Relay 135, upon deenergizing, also opens the bridge across the trunk conductors 200 and 202, with the result that the relay 320 at the recordmg operators position is deenergized followed by the deenergization or the slow acting relay 321. The switching relays in the selector switches E' and E and in the line switch C are deener ized and these switches are thereby restore to their normal position in the usual and well known manner. The operations in the repeater D which take place u ondisconnection and which have to do wit the collection and refunding oi coins are of no importance in the case of the connection just described and will therefore be explained later on.

The operation of the system when the sub- .scriber at substation A desires connection with another subscriber will now be described it rst being assumed that the subscriber at substation A. attempts to make connection with the desired partys line without first depositing a coin in his paystation apparatus.

When the receiver is removed at the substation A the o erations by which the line of the calling subscriber is extended through the medium of the line switch C and the repeater D to a first selector E are identical with the operations described in the previous case and will not be repeated. The operation of the selector E" wherein the connection is extended to a second selector likewise alreadyV have been described and in this casel there is nothing new in the operation except that the wipers 255-257, inclusive, are ralsed oppor site a bank level in which are terminated trunk lines extending to second selectors of the regular trunking system. The second selector E is a switch of this class and it will bel assumed that the trunk line extending thereto isthe rst trunk line found to be idle and that the selector E establishes connection with the bank contacts 265-267, inclusive. The trunk ' conductors 200 and 202 will now be extended by the operation of the switching relay 229 by wayof wipers 255 and 257, bank contacts 265 and 267, to the ing-its armature 275 relay 271 closes a hold-4 ing circuit which extends as follows ground by way `01E armature 275 andA its front contact, test contact 266, test wiper 256, to armature 251 and its front contact, where the circuit divides, one path extending'through the winding of the switching relay 229 and the interrupter relay 228 in series to battery, and the other ath extending by way of release trunk con uctor 201 to junction oint 198, Where it joins the branch exten ing from round and front contact of armature 188 in ghe repeater .D. It will be observed that the above traced circuit contains no resistance such as resistances 240 and 295 and, as a result, relay 141 in repeater D is practically short circuited. This relay is therefore deenergized and atits armature 196 closes the previously described shnt circuit around armature 184 of the line relay 135 and its front contact, thereby rendering the armature 184 ineffective to open the bridge across the trunk conductors 200 and 202 when the relay 135 is deenergized. When the calling subscriber operates his dial in accordance with the next digit and roduces another series of interruptions in t e line circuit the' result-ing deenergizations of relay 135 will be of no eiect and it will be apparent that the selector E3 cannot be operated.

The difference in the two classes of second selectorsl will now be apparent. All the selectors which are required to be used in extending a connection to an o erators position or the line of an oilicial o the telephone company are provided with resistance in their release trunks similar to the resistance 240 and 295, while those switches which are used only in connections to local subscribers have the resistance omitted. It follows then, that whenever it is attempted to use a switch of the latter class, under the circumstances just described, where no coin has been deposited, the relay correspon-ding to the relay 141 of the repeater in use will be short circuited vand will deenergize to disable the operating circuit exten ing to the switch thus preventing further extension of the connection.

The operation of the system in the case where the subscriber at substation A deposits a coin before calling the desired subscriber will now be described and in this connection the process of collecting the coin at the termination of the conversation will be briefly described. The first operation on the part of the subscriber at substation A is to deposit a coin of suitable denomination in the coin collecting mechanism provided for that purpose. This mechanism is well understood and its operation need not be explained in detail. When the coin is deposited it descends p-ast the trigger mechanism which is released by the coin with the result that the polarized relay of the coin` collecting mechanism is connected from the line conductors to ground. The coin is held in suspense by a trap door where it is adapted to be either collected or refunded under control of the polarized magnet. The coin may be deposited either before or after the receiver is removed. In either case the latter operation brings about the operation of the rotary line switch C whereby the line is extended to an idle r'st selector switch. As= suming that the selector E', Fig. 3 is the switch to which connection is extended, the operations are the same as have already been described and will not be repeated, Wit one exception, however; when the line conductors 11 and 12 are connected by the operation of the line switch C with the windin s of the line relay 135 and the impedance co1ll39, of the repeater D, the ground on line conductor 12 unbalances the differential relay 130, which is included in the linecircuit, and causes this relay to energize. It may be stated at this point that the polarized magnet at the substation is of high resistance and does not materially interfere with the transmission of operating impulses or with the talking circuit but it is nevertheless suicient to cause the relay 130 to operate as described. Upon attracting its armature 170, relay 130 closes a circuit for relay 134 which, upon energizing, establishes a locking circuit for itself at armature 178. Relay 134 also grounds the holding circuit extending back to the line switch C at its armature 179 and at its armature 180 opens the shunt circuit around the impulsing springs represented by armature 184 and its front contact. This latter operation is an essential feature to be considered at this time for obviously it permits any of the switches in the exchange to be operated no matter whether they are provided with resistance in the release trunk such as the resistance 240 or not. Relays 130 and 134 therefore constitute means responsive to the deposit of the coin for rendering the repeater D operative to repeat impulses regardless of the type of switches which it is attempted to operate.

The calling subscriber may now operate his calling device in` accordance with the digits in the number of the substation A. The selector E will respond to the first digit in the same manner as has already been described. The second selector E3 will also be operated in the usual manner to the desired level in which are terminated trunk lines leading to connector switches such as connector H, Fig. 4, which has access to the line of the substation A. The selector E3 will then rotate in the well understood manner to select a trunk line which leads to an idle one of these connector switches and, which, it will be assumed, is the trunk line comprising conductors 380-382, inclusive, and terminating in bank contacts 353-355, inclusive. As this trunk line is idle, there will be no ground potential present upon the test contact 354 and the switching relay 274 will be energized. Immediately upon the energization of relay 274, the trunk con ductors 201 and 202 will be extended by way of wipers 350 and 352, bank contacts 353 and 355, conductors 380 and 382, normally closed springs controlled by armatures 420 and 421, to the upper and lower windings of theline rela 401 `0:t` the connector H. Relay 401 will e therefore energized and will operate to complete the circuit of the slow acting release relay 402 which operates to prepare the impulsing circuits of the connector H at armature 429 and at armature 428 places ground on the release trunk conductor 381 thereby establishing a holding' circuit for the selector switches E3 and E.

As before mentioned, immediately upon the first deenergization of the line relay 135 in the repeater D the slow acting relay 137 is energized and the circuit oi the relay '129 completed. The latter relay, upon energizing, establishes, a locking circuit for itself and short circuits the windings of the differential relay 130. By this provision it will be seen that should the calling subscriber attempt to extend the connection without rst depositing a coin and then after linding that he gets no connection deposits a coin he will be unable to affect the differential relay 130 without first hangingup his receiver. rEhis provision is made'so that the .possibility of the calling subscriber obtaining Wrong numbers by having one or more digits of the desiredcalled number absorbed on accountof the shunt circuit around the impulse springs 184, is entirely eliminated.

The calling vsubscriber at substation A i may now operate `his calling device for the response thereto.4 Atp each deenergization,

next "digit of the desired number. By this operation a series of interruptions is pro-l duced in the circuitvof the line relay 135 of the repeater D and these interruptions are then repeated by means of: the armature 184 to the line relay 401 ofthe connector H which deenergizes a plurality of times in an. impulse of current is sent over a circuit extending from ground by way of armature 424and its back contact, armature 429 and-its front contact, o normal springs "436 and 437, winding of the slow acting relay 404, and thence through the Winding of the vertical magnet 413v to battery. .The

above Iis the circuit over which the iirst im 470473, inclusive, stepl by step until they and maintains are placed opposite the level of bank contacts in which is located the contact set associated with the line of the substation A. The slow acting relay 404 is energized in series with the vertical magnet 413 its armature attracted throughout. the vertical movement of the switch, and at the termination thereof deenergizes transferring the operating circuit to the rotary magnet 412.

The subscriber at substation A may now dial the next and iinal digit of his desired number. As before, a series of interrup tions is produced in the circuit of the line relay 135 of the repeater D and these are repeated to the line relay 401 of the connector H by means of armature 184 and its front Contact. At each retraction of its armature 424 an impulse of current is sent to the rotary magnet over a circuit extending from ground by way of the said armature and its back Contact, armature 429 and its front contact, olf normal springs 436 and 438, armature 435 and its back contact, back contact and armature 447, winding of the slow acting relay 407,` back Contact and armature 460, through the winding of the rotary magnet 412` to battery. The rotary magnet 412 operates to rotate the switch wipers the set of bank contacts associated with the line of the substation A which, we will assume, are the bank contacts 474-477, inclusive. llhe slow acting relay 407 is energized in series with the rotary magnet and at its armature 451 completes the circuit of the slow acting relay 408. .The latter relay, upon energizing, connects the test wiper 472 to the winding of the test relay 406.

Assuming that the desired line vis busy at the present time, there will be a ground potential presentupon the test contact 47 6 engaged by the test wiper 472 and the test relay 406 w'ill be energized. Relay 406, upon operating, prepares a locking circuit for itself atits armature 446 which is completed upon the deenergization of the slow acting relay 408, and at its armature 448 places the busy tone on` the lower heavy talking conductor whereby the calling subscriber is notified that the desired line is busy and he will replace his receiver upon the switchhook thereby initiating the release of the operatedswitches in a manner which will be'described later. i

It will now be assumed that the line of the substation A is one of the group of lines listed under the same number.y The circuits of the connector H must then be changed in order to enable it to select the first idle one of these lines. This is accomplished by connecting the test contacts -similar to test contacts 475 and 476 together on all except the last line of the group.. Thus-` and thence a5 y 470-473, inclusive, into engagement with when a line becomes busy ground is present upon both these test contacts. Assuming that the test contacts 475 and 476 are so connected and that the line of the sub-station A was busy when connection thereto.

was attempted by connector H the test relay 406 will be energized as before described md will operate to establish a locking circuit for itself at armature 446. Following the deenergization of the slow acting relay 407, there being a ground potential present upon the test Contact 475 engaged by the test wiper 471, a circuit may be traced eX- tending from the said grounded test contact by way ofl said test wiper 471, back contact and armature 450, armature 445 and its front contact, armature 464 and its back contact, and thence through the winding of the stepping relay 403 to battery. Relay 403 is energized over this circuit and, upon operating, establishes a locking circuit for itself at armature 432 and at armature 433 completes the circuit of the rotary magnet. Magnet 412 operates to rotate the switch wipers into engagement with the next set of bank contacts in the selected level and at armature 464 breaks the locking circuit of the stepping relay 403 which relay deener` gizes opening the circuit of the rotary magnet 412 which deenergizes also. The slow acting relay 408 is energized in multiple with the rotary magnet and operates to maintain the test wiper 472 into connection with the test relay 406. If this next line is busy the test relay 406 will remain energized, the stepping relay 403 will be again energized and the connector switch wipers will be rotated into engagement with the contacts of the next line 1n the group. The alternate operation of the stepping relay 403 and the rotary magnet 412 will continue until an idle line in the group is found or until the switch wipers are rotated into engagement with the last line in the group. In the latter event if the last line is busy, since the test contacts similar to 475 and 476 are not joined together, there will Vbe a ground potential present only upon the test contact engaged by the test wiper 472. The test relay`406 will be the only relay operated and a busy tone will be given to the calling subscriber in the same manner as was described hereinbefore. It will be noted that the slow acting relay 408 maintains the test wiper 472 in connection with the test relay 406. This circuit renders a very fine and accurate adjustment of the rotary magnet unnecessary and at the same time secures a very positive operation. This is for the reason that even if the test wiper 472 is rotated slightly past the bank contact of the connected line the slow acting relay 408 maintains it in connection with the test relay 406 so that the latter relay may deenergize, but if the line is busy it will be again energized upon the switch wipers attaining thelr roper position.

It will now assumed that the line ofthe sub-station A was idle when connection therewith was attempted by the connector H. Under these circumstances there will be no ground potential resent upon the test contact 476 'engaged gy the test wiper 472 and no circuit will be completed for the test relay 406. Then, following the deenergization of the slow acting relay 408, a circuit is completed extending from ground on release trunk conductor 381, by way of armature 446 and its back contact, upper winding of the switching relay 409, back contact and armature 454, test wiper 472, test contact 476, through the winding of the switching relay 480 of the line switch C', and thence through the winding of the motor magnet 482 to battery. Relays 409 and 480 are energized over this circuit. However, due to a mechanical interlocking device controlled by the armature of the line relay 481 which is now normal the armatures of the relay 480 are only attracted enough to disconnect the line of the sub-station A from its normal battery and ground connections in the line switch C. Relay 409, upon energizing, establishes a locking circuit for itself at armature 461 and at armatures 457 and 463 completes `the ringing circuit. Ringing current is now intermittently Projected over the line of the substation A rom the ring` ing equipment V.

When the called subscriber answers a circuit for the ring cut oli' relay 405 is completed over the called line loop. Relay 405,

upon energizing, establishes a locking circuit for itself at armature 441 and at armatures 440 and 442 cuts off the ring and at the front contacts of these armatures finally completes the talking connection. The back bridge relay 400 is immediately energized over the line of the substation A and supplies talking current to the called subscriber. Relay 400, upon operating, reverses the direction of current flow over the calling subscribers line. The direction of current iow in the bridge of the repeater Dis therefore reversed causing the electropolarized relays 128 and 132 to operate. Relay 128, upon operating, establishes a locking circuit for itself at armature 163, completes the circuit of the slow acting relay 127 at armature 162, and at armatures. 160 and 164 removes its upper winding and the lower winding of the electropolarized relay 133 from a bridge across the trunk conductors and also disconnects the incoming line conductors 48 and 51 from the windings of the relay 135 and the impedance coil 139 and extends them direct to the windings of the line relay 401 of the connector H. Another result of the energization of relay 128 is that acircuit is completed extending from ground by way of :front cohtact and armature 161, conductor 49, bank contact 53, wiper 45, front contact and armature 34, and through the windmg of the meter magnet 28 to battery. Magnet 28 operates to register the completed call .in the usual manner. Relay 127, upon energizing, at its armature 156 completes an additional holding circuit for the line switch C, and at armature 155 prepares certain of the coin lcollect circuits which will be described later. Relay 132 is ,an electropolarized relay so adjusted `that it will attract its armatures when the current is reversed in its upper Winding and will maintain its armatures attracted by means of its polarizing vvlnding even if the circuitoi' its upper winding is opened. However, i the current flow in its upper Winding is restored to normal it will retract its armatures. Relay 132, upon operating, opens a point in the circuit of the relay 131 thereby preventing the latter relay from energizing at this time.. rlhe up er Winding of relay 132 is included in the ta king circuit but 1s shunted by the non-inductive resistance 193 which affords a path or voice currents so that the talking eihciency oi the circuit is not materially affected.

When the conversation is terminated both subscribers will replace their receivers upon their respective switchhooks. When the receiver is replaced at the calling substation A. the line relay 401 in the connector H is deenergized as is the slow acting relay 402. The latter relay, `upon deenergizing, closes apoint in the release circuit of the connector H at armature 429 and at armature 428 removes ground from the release trunk conductor 381. By this operation the holding circuits of the selector E and E are opened and these switches released. Ground being removed from the release trunk conductor 201 the relays 128 and 132 in the repeater D are deenergized. Relay 132, upon deenergizing, completes the circuit of the rela-y 131 at armature 175. The latter Arelay upon energizing, reverses the trunk conductors 200 and 202 with regard to the conductors of the calling line. This provision is made so as to prevent the line relay 401 from remaining energized Yeven after the receiver is replaced at` the substation A` over a circult which includes the polarized relay ofthe coin collecting mechanism at the substation to ground and the upper winding of the line relav 401, supposing that the called subscriber had hung up before the calling subscriber. Relay 128, upon deenergizing, opens the circuit of the sloW acting relav 127 but, before this-relay has had time to deenergize, an impulse of current is sent over the following path: ground by Way of armature 162 and its back contact, armature 157 and its front contact, and thence through the winding of the slow acting relay 125' to'battery. Relay 125, upon energizing, places an additional ground on the release trunk conductor 50 extending back to the line switch C at armature 146, and atthe same armature opens the locking circuit of the slow acting relay 134 which deenergzes and at armature 147 completes a circuit extending from ground by way of front contact and said armature, conductor 107 and through the Winding of the relay 71 to battery. Another result of the energization of relay 125 is that at armatures v145 and 144 both sides of 'the line of the substation A are opened and at the front contact of armature 144 the battery lead 105 kfrom the battery B2 is Aconnected to the line conductor 12 over the closure of the above traced circuit current flows from the battery B2 through the relay 140 and the polarized magnet at substation A in series to ground energizing both the relay 140 and the said magnet. Relay 140 closes at its armature 195 a circuit for the slow acting relay 126. Relay 126,upon energizing, closes at its armature 149 a circuit for the supervisory lamp L, at its armature 150 completes a locking circuit for the relay 127 which, being slow acting, has not yet deenergized, and at armature 152 connects the incoming line conductors by Way of the condenser to ground. Ordinarily the polarized magnet at substation A will respond at once to current from battery B2 and will operate to collect the deposited. coin and restore the entire coin collecting mechanism to normal condition instantly at the same time disconnecting itself from line conductor 12. However, it sometimes happens that the armature of the polarized magnet will stick and the relay 133 is provided to insure the collection of the coin in such case. The interrupter I causes vrelay 133 to rapidly vibrate its-armature and interrupt the circuit of the battery B2 'or the battery B in case thisbattery is included in the circuit with the object of intermittently energizing the polarized magnet this operation being ordinarily eii'ective to free the armature in case it should stick. However, should the armature of the polarized magnet continue to stick the relay 126 will remain energized. It will be remembered that vrelay 125, upon energizing, completed a circuit extending from ground by way of front contact and armature 147, conductor 107, through the winding of relay 71 to battery. Relay 71, upon energizing, closes the circuit of the high resistance relay 69 at armature 91, at armature 93 completes a locking circuit for itself, and at armature 92 closes a circuit which extends over the following path: ground by way of front contact and armature 92, resistance 97, through the winding of relay 68 to battery. Relay 68, upon energizing, completes a circuit extending from ground by way of front contact and armature 88, through supervisory lamp L3, through the winding of relay 67, and through the winding of relayv 66 to battery. Relay 66 is of such high resistance that the relay 67 is not energized or the lamp Ls lighted in series withV it-though it receives sulicient current to energize. Relay 66, upon operating, completes the circuit of the solenoid 60. The solenoid immediately operates to pull up its plunger arm 75. This operation takes considerable time as it is retarded by means of a dash pot. The relay 69, upon ener izing, closed a circuit for the relay 70 whici relay energized and opened the locking circuit of the relay 71. If the coin is not collect/ed at the substation A there will still be ground resent upon the conductor 107 and the re ay 71 will be maintained energized and consequently the solenoid will finally attain its operated position. When this occurs the springs 77, 78, and 79 will be forced into engagement by the arm 76. When this occurs a circuit is completed eX- tending from battery by way of springs 77 and 78, winding of relay 65, windin of relay 67, lamp L8, armature 88 and its ront contact to ground. It will be seen that this circuit short circuits the relay 66 which deenergizes. The lamp L3 is lit and the relay 67 operated over this circuit. Relay 67, upon energizing, completes the circuit of the supervisory lamp L2. The lamp L2 is ageneral supervisory lamp and is common to several groups of switches, while the lamp La is individual to a particular group of switches. Relay 67, at its armature 89, also closes the circuit of an alarm whereby the attention of the exchange attendant is attracted. The attendant, upon seeing the lighted condition of the lamps L2 and L3, will note the nature of the trouble and will go to the particular group of switches designated by the lamp Ls. A lamp L is individual to each repeater such as D and by the lighted condition of this signal the attendant will know it is this particular switch or rather the coin collecting mechanism at the subscribers substation whose line is as sociated with this switch which is causing trouble.

Another condition that this alarm signal provides for is that in case either one of the batteries B or B is out of order the relay 69 will not be energized and the locking circuit of the relay 71 will be maintained closed even though ground is immediately removed from the conductor 107. Therefore the signals LB and L2 will be operated but as there is no lamp similar to lamp LE5 operated ati this time the exchange attendant will know the nature ofthe trouble.

Returning now to the operation of the repeater D, when the polarized magnet at the .coin collecting mechanism at the calling substation is finally disconnected from the line, the relay 140 will deener 'ze and open the circuit of the relay 126 wich relay will deenergize also thereby opening the locking circuit of the slow acting relay 127. Relay 127, upon retracting its armatures, .opens the circuit of relay 125. Relay 125, upon de- .l

energizing, removes groundvfrom the conductor 107 at armature 147, and at armature 146 removes ground from the ,release trunk conductor 50 whereby the holding circuit of the switching relay 25 of the line switch C is broken. In this manner all the apparatus is reored to normal and is ready for anotherl ca As was previously mentioned, the relay 131 in the repeater D is provided in order to prevent any lockin up of the switches when the called subscrlber at substation A replaced his receiver before the calling subscriber. Assuming this to have occurred, the back bridge relay 400 in the connector H will be deenergized and battery from the line relay 401 will be on the lower heavy talking conductor. The battery flow over the calling subscribers line is therefore restored to normal and the relay 132 in the repeater D will be deenergized to complete the circuit of the relay 131. Relay 131, upon energiz ing, reverses the conductors 200 and 201 with regard to the subscribers line in order to prevent the line relay 401 of the connector H from remaining energized, after the calling subscriber hangs up, in series with the polarized magnet at the subscribers substation. When the calling subscriber hangs up the release of the connection and collection of the coin will take place in the same manner as was before described.

Returning now to the operation of the connector H, it will be assumed that the calling subscriber at substation A replaces his receiver upon the switchhook before the called subscriber at substation A does. The line relay 401 immediately deenergizes and opens the circuit of the slow acting relay 402. Before the deenergization of relay 402 an impulse of current is sent to' the slow acting relay 408 in series with the slow acting relay 407. However, relay 408 is of such resistance that it only is energized over this circuit. Relay 408 operates to remove ground from the release trunk 381 for a short interval in order to enable the selectors E3 and E to be released, after which the connector is protected from seizure immediately upon the deenergization of relay 408, ground being again replaced upon the release trunk 381 through the upper winding of rela 409. When the called subscriber at substation A' hangs up the back bridge relay 400 is deenergized and the release magnet circuit closed. The connector H is thus restored to normal by the last party to replace his receiver.

In case the called subscriber did not answer it will be necessary to reiund the deposited coin rather than collect it when the calling subscriber replaces his receiver, and this refunding operation will now be explained. Since the called subscriber did not answer neither the polarized relay 128 nor the polarized relay 132 will be energized and uo circuitI will be completed for the slow acting relay 127 or the meter magnet 28 associated with the line switch of the calling subscriber. Now when the calling subscriber hangs up v his receiver the line relay 135 deenergizes and sends an impulse ot current to the slow acting relay 137 at thel same time opening the circuit ont the slow acting relay 136. The latter relay, upon deenergizing, completes a circuit extending from round by way of armature 188 and its bac contact, rontcontact and armature 192, and through the winding oi the slow acting relay 125 to battery. Upon ener izing, relay 125 operates as before describe except that in the resent case since relay 127 is deenergized t e battery lead 106 from the battery Bv is lconnected to the line conductor 12 instead of the battery B2. Current iow from the battery B now operates relay 140 and the polarized magnet at the calling substation in series, the latter bein now actuated to refund the deposited com rather than'collect 1t. Upon energizing, relay 140 completes the circuit of relay 126 which operates toh the slow actin close the holdmg circuit of the relay 125. The energization of relay 126 also produces certain other circuit changes which have been explained before. When the c1rcu1t is finally broken by the polarized magnet at the calling substation bein disconnected from the line conductor 12 t e relay 140 deener gizes and opens the circuit of relay 126 which deenergizes also. gization of relay 126 the holding clrcult of relay 125 is o cned and this relay restores to normal there y removing ground from the holding conductor 50 and the line switch C 1s thenallowed to restore to normal whereupon all the apparatus will have been released.

Having fully described and ascertalned the features of the invention what is considered to be new and desired to have protected by Letters Patent will be appended claims.

What I claimis': y

1. In a telephone system, a subscribers station, a paystation device at said station,

pointed out inthe Vautomatic switches at the exchange, a repeater interposed between said line and switches, a control circuit extending from said repeater for operating said switches, and means in certam of said switches for As a result of the deener- ,rendering said control circuit inoperative unless a coin has beendeposited in said device' before any of said switches have been operated.

2.. In a telephone s stem, a subscribers station, a paystation evice at said station, automatic switches at the exchange, a repeater interposed between said line and switches, a control circuit extending from said repeater for operating said switches, an operators position accessible to certain of said switches, a called subscribers line accessible to certain other of said switches, and means in the said latter switches only for rendering said control circuit inoperative unless a coin has been deposited in said device before any of said switches have been operated.

3. In a measured service telephone system,

a repeater and associated first selector switch at the exchange, trunk lines accessible to said switch each terminating in a second selector switch, a release trunk conductor in each trunk line, resistances in the release trunk conductors extending to certain of said second selectors only, and means in said repeater for preventing a calling subscriber fromoperating those selectors whose associated release trunk conductors have no resistances unless the connection has been paid for before the said first selector is operated. A

4. In a telephone system, a subscribers line extending to a central exchange, coin collecting` mechanism at the station on said line, serially related automatic switches at the exchange, a repeater interposed betweenV the said line and switches, a normally operative control circuit extending from the repeater to the first one of said switches, means in the lirst switch for extending the control circuit to the next switch, the extended control circuit being normally inoperative, means responsive to the deposit of a coin in said mechanism for rendering said extended control circuit operative, and means for preventing the deposit of a coin from rendering the extended control circuit operative unless the coin is deposited before saidY first switch is operated.

5. In a telephone system, a calling station, a paystation device at the said station, selector switches at the exchange, a repeater interposed between said line and said switches, a control circuit normally inoperative extending from said repeater for operating saidselectors, adiiierential relay in -said repeater for rendering said control cir- @ill said trunk line, a release tiunk conductor in said trunk line, a condenser at 'said repeater dividing said release trunk into twosections, means operated over a calling line for causing the associated automatic switch to select said trunk line, means in the said first selector for applying ground to one section of the said release trunk through a resistance, a relatively low resistance retardation coil, and means in said repeater for applying ground to the other section of said re ease trunk through said coil.

7. In a telephone system, a subscribers line, a paystation device on the said line, an automatic switch in the exchange, called lines, a repeater interposed between said line and switch, means for extending a connection through said repeater and switch from said subscribers line to one of said called lines after a coin has been deposited in said device, a battery at the exchange, means in said repeater adapted to impress current from said battery on the said subscribers line to collect the coin when the receiver is replaced, a signal, and means for operating said signal if said battery is out of order at the time the collection of the coin is attempted.

8. n a telephone system, a subscribers line, a paystation device on the said line an automatic switchV in the exchange, called lines, a repeater interposed between said line and switch, means for extending a connection through said repeater and switch from said subscribers line to one of said called lines after a coin has been deposited in said device, a battery at the exchange, means iii said repeater adapted to impress current from said battery on the said subscribers line to collect the coin when the receiver is replaced, a sifgnal, and means :for operating said signal i said coin is not collected by the said device.

9. ln a telephone system, a subscribers line, a paystation device on the said line, an automatic switch in the exchange, called lines, a repeater interposed between said line and switch, means for extending a connection through said repeater and switch from said subscribers line to one of said called lines after a coin has been deposited in-said device, a battery at the exchange, means in said repeater adapted to impress current from said battery on the said subscribers line\ to collect the coin when the receiver is replaced, a signal, an-d means for operating said sigi nal at the expiration of a predetermined time interval beginning with the replacement of the receiver in case the coin is not collected in the meantime.

10. In a telephone system, a calling line, a paystation device on the said line, a meter for said line, automatic switches in the exchange, called lines, a repeater interposed between said calling line and switches, a control circuit whereby the subscriber on said calling line mav control said automatic switches to complete a connection to one of said called lines if a coin is de osited in said device, means controlled b t e res nse of the subscriber on said ca ed line or operating said meter, and'means in said repeater controlled when the subscriber on said calling line hangs up for collecting said coin.

11. In a telephone system, a calling subscribers station, a called station, a paystation device at the said calling station, a trunk line leading to an automatic switch at the exchange, a repeater included in said trunk line, means whereby the calling station can extend a connection to said called station by way of said repeater and switches when a coin as been deposited in the said device, and means in said repeater controlled by the subscriber at the called station in replacing his receiver upon the switchhook for reversing` the conductors of the trunk extending from said repeater to the automatic switch.

12. In a telephone system, a series of automatic switches for connecting a calling and called line in conversation, means in the final switch for reversing the direction of current flow in the calling line when the called man answers, said means being operative only while the receiver is o at the called station. and additional reversing means operated after the called man hangs up to maintain the current How in the calling line in the reverse direction.

13. In a telephone system, means including an automatic switching mechanism for connecting a calling and a called line in conversation, a relay in said mechanism supplying talking current to the calling line, a relay responsive whenthe called man hangs up for reversin the direction of current flow in the calling line, and additional reversing means operated when the called man hangs up in order to -prevent such current reversal.

14. In a telephone system, means includ ing an automatic switching mechanism for connecting a calling and a called line in conversation, a relay in said mechanism supplying talking current t0 the calling line, a relay responsive when the called man hangs up for reversing the direction of current flow in the calling line, talking conductors over which the talking current is supplied, and means for reversing said conductors at a point between the calling line and said first relay in order to maintain the iow of talking current in the same direction notwithstanding the operation of said second relay.

15. In a telephone system, means including an automatic switching mechanism for connecting a calling and a called line in conversation, a relay in said mechanism supplying talking current to the calling line, a relay responsive when the called man hangs up lilnece-,eee

ior reversing the direction et current dow in the calling talking conductors over which the talking current is supplied, a polar relay having a winding in one of sai-d conductors and responsive to said current revernal, and a second reversing relay controlled by said polar relay for reversing said g conductors a point between the s. polar relay and the calling line.

16. lin a telephone system, a calling line, a paystation thereon, automatic switches at the exchange, a repeater interposed between said line and said switches, a circuit over which said switches are controlled by said repeater in response to a plurality of impulses sent thereto, means or disabling said control cir cuit, a relay, means for operating sa1d relay to render said disablin means inoperative when a coin is deposited in said paystation, and means tor rendering said relay unresponsive to the deposit of a coin upon the iirst impulse being sent to said repeater.

17; ln a telephone system, a subscribers line, a trunk terminating in an automatic switch, means for extending said line when calling into connection with said trunk, a repeater inserted in said trunk, a release trunk conductor in said trunk, a condenser in said release trunk conductor at said repeater dividing said conductor into two inductively coupled sections, a `source of tone current associated with said line, means for sending tone current therefrom over said release trunk conductor and through said condenser to said switch, and means for applying a holding potential to the first section at said repeater to maintain said line in connection with said trunk, said holding potential be ing supplied through a retard coil that prevents said tone current from being shuntedv away from the second section of sa1d release trunk conductora 18. In a telephone system, a subscribers line terminating in a central exchan e, automatic switches accessible to said ine and responsive .to impulses to extend connections from the calling line to other lines, and means operated to control one of said switches alsooperated to prevent the init-iated connection being extended beyond certain of said other switches unless a special act has been previously performed by the subscriber calling, but ineective to prevent a connection being established via other of said switches.

19. In a telephone system a subscribers line terminating in a centra exchange, automatic. switches accessible to said line and responsive to impulsesto extend connecill@ tions :trom the calling line to other lines,

and means operated to control onel of said switches also operated to linaily determine whether the connection can be extended via any oi said other switches or whether it can be extended via only certain ci said other switches.

20. in a telephone system, a calling station, a paystation device at the said station, selector switches at the exchange, a repeater interposed between. said line and said switches, a. control circuit normally inoperative extending from said repeater for operating said selectors, a differential relay in said repeater for rendering said control circuit operative when a coin is deposited in said device, and means in said repeater operative to transmit an operating impulse to one of said selectors also ei'iective to cause said diderential relay to become short circuited.

21. ln a telephone system, a calling line terminating in a central exchange, a paystation apparatus at the station of said line, means including a trunk and an automatic switch for setting up a connection with called lines of either 'of two classes, a relay included in a series bridge across the talking conductors of said trunk line, said relay` operative contingent on the call being answered and ot a particular class, and contacts on said relay for causing it to disconnect itself from the bridge and prepare circuits "lli subsequently used in collectlng a deposited connecting said release trunk in inductive` relation to the tallnng conductors of the trunk, and means in the said repeater and 1.10

selector, respectively, for causing the inductively connected current to be transmitted to the talking conductors of the trunk upon said manually operable means being operated.

In witness whereof, I hereunto subscribe my name this 17th day of May, A. D., 1921.

JOHN W'ICKS.

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