US1432618A

US1432618A - Automatic telephone selecting system

Info

Publication number: US1432618A
Application number: US272955A
Authority: US
Inventors: Winfred T Powell
Original assignee: STROMBERG CARLSON TELEPHONE
Current assignee: STROMBERG CARLSON TELEPHONE; STROMBERGCARLSON TELEPHONE MANUFACTURING Co
Priority date: 1919-01-24
Filing date: 1919-01-24
Publication date: 1922-10-17
Anticipated expiration: 1939-10-17

Description

W. T. POWELL;

AUTOMATIC TELEPHONE SELECTING SYSTEM. APPLICATION FILED JAN. 24. I919.

Patented Oct. 17, 1922 IEHII- MARGINAL INVENTOR WTNF ED T. POWELL.

ATTORNEY Patented Get. 17, R922.

entrain stares WINFRED T. POWELL, ROCHESTER, NEW] YQR-K, ASSIGNOR TO THE STRUT/[BERG- GARLSON TELEPHONE MANUFACTURING COh IPANY, ROCHESTER, NEW YORK,

A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE SELECTING SYSTEM.

Application filed January 24, 1919. Serial No. 272,955.

T 0 (all 10710-772, it may concern:

Be it known that I, lViNrRnn T. PownLL, citizen of the United States, residing in Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Automatic Telephone Selecting Systems, of which the following is a full, clear, concise, and exact description.

My invention relates to telephone systems, and more particularly to such systems as are well-known in the art as automatic telephone systems, wherein any one of a number of subscribers to the system may without the manual. aid of an operator, operate the central station switching apparatus under the control of the subscriber substation apparatus to interconnect the calling subscribers line with adesired one of the other subscribers lines.

An object of my invention is to provid an improved organism for such a system as will attain great efficiency of operation with the minimum of failures, this being accomplished with a relatively small amount of apparatus operating in a most positive manner.

It is a further object of my invention to provide a novel means of controlling the movements and release of the switch mechanism employed in interconecting the lines; other objects of my invention and the invention itself will be made apparent from the description of the same which follows, and in which description reference is made to the accompanying drawing showing a preferred embodiment of my invention.

Referring to the drawing, at A and B I show two telephone substations comprising talking and signalling apparatus, as will be later more fully described herein, these substations being connected by telephone lines to main station apparatus individual to each of the lines; this main station line apparatus being shown at L for the calling line station A, and at M for the called line station B. I

It will be understood that either of these stations might be the calling or called station, but for convenience in this description, it will be assumed that the calling station A is seeking a connection with a called station B; other telephone lines for other stations would of course be provided for such a system as herein'described.

At ON, I show a telephone line interconnecting circuit consisting of a directively operated numerical switch mechanism, not shown in detail but which may be. of any of the well-known forms of switch mechanism commonly used in the art to which this invention appertains, and it will be assumed in this description that the switch mechanism is of the type whose outgoing wipers, by which connection is made to a desired called line, are moved first in a primary direction under the control of calling substation apparatus, and thereafter moved in a secondary direction under subsequent control by the calling substation apparatus. Other equivalent forms of switching mechanism are contemplated.

through the terminals of a called line which comprise contacts associated with the called line adapted to be engaged by the traveling switch wipers of the switch mechanism CN.

The substation A comprises a transmitter t, adapted to be energized by current flowing over the line from the central station, a receiver 1', an induction coil 2', together with the usual telephone bell and serially connected condenser illustrated by the usual symbols, switch hook contacts '8 adapted to control the connection of the substation apparatus with the line conductors 1 and 2 of the calling line; also included at the substation A are contacts 7, 4L5, and 47 of a subscribers selective switch controlling mechanism, comprising the usual form of 2 wire dial.

The controlling mechanism for these contacts is so organized, that when the subscriber gives the dial the preliminary forward movement, contact 4-5 opens and con tacts 46 and 47 close. The circuit connection thereupon causes the contacts 46. to

oulse s )rin s 7 are ooened a definite redetermined number of times corresponding to the digit of the desired line number at the time being dialed, the operations of the springs 7 being but'momentary and occurring in rapid succession.

Immediately after the last interruption of the circuit by the contact 7, as described, and prior to the subsequent closure of these contacts, contacts 46 and 47 are opened, and contact 45 is closed to place the substation relay C of the substation apparatus in circuit with the line. This relay G contains normal contact 6 in circuit with the contact 7, so that when the relay C is operatively connected in circuit that the line current over the line will operate the relay C, and

its contact 6 in the circuit of the contact 7 being opened, the subsequent closure of the contact 7 will be impotent. The relay C is of relatively high resistance for a purpose to be made clear in the description of the connector switch relays T and R.

At the main station for the line containing the substation A and which leads by circuit conductors land 2 to the main station, there is provided a line switch having wipers 17, 24, 4, 14 and 10 which normally rest upon a set of home passive contacts, a plurality of which are preferably provided, although a single set willsuflice, Such a plurality of home passive contact sets will preferably be interposed between alternate sets of trunk point passive contacts to each set of which circuit conductors leading to the controlling circuits of a connector switch mechanism CN will be connected. Such a home point contact setis, for instance, at 16, 23, 3, 13 and 11. A passive set of trunk point contacts is shown at 222, 32, 35, 104 and 36, these being connected by circuit conductors to the connector switch I mechanism CN. Other sets of trunk' point contacts will be preferably provided for the switch, such another set being shown, for instance, as the set containing the contact 31. i

The line switch wipers are controlled in their movements by stepping magnet ST, designated 29, having a reciprocating armature and contacts 28. The line relay LR and the cut-off relay CO, for the line, co-operate in the control of this stepping magnet. The

line switch mechanism including the said stopping magnet and relays, is adapted to operate to connect the calling line through the line switch wipers and trunk point switch contacts of such a switch mechanism as UN as may at the time be idle, to the circuits of such a switch mechanism, connec tion being had through the circuit conductors as 33, 34, 38 and 37 for the switch mechanism ON.

Associated with the switch mechanism CN, is a primary stepping magnet PM adapted to step the connector switch wipers 57, 58 and 59 in a primary direction, and a secondary stepping magnet SM to thereafter step the said wipers in a secondary direction, whereby connection is made with the called line terminals, such as the terminals 72, 87 and 80 of the desired called line. Controlling the operation of the primary and secondary stepping magnet, is an escape magnet ESC which operates upon each deenergization to advance the side switch wipers 52, 68, 69, and from one operative position to another in thewell known manner, also a step by step switch comprising wipers 43, 41. and 44 and a stepping magnet MO therefor, also relays T andR which exercises primarily a control over the said step by step switch, the escape magnet and the primary and secondary stepping magnets.

Associated also with the switchmecha nism is a busy test relay BY, a ringing trip relay TR, a release magnet REL, a release relay RL controlling the said release magnet, and other apparatus and circuit organizations which will be more fully described in the narrative of the operation of the system which will later follow.

For a plurality of switch mechanisms, as ON, there, is provided a timing circuit controlling, means, consisting in the embodi- ,ment illustrated, of a pair of rotary commutators 121 and 122 mounted on a shaft,

113, which is continuously rotated to cause the successive operation of the contacts 92 and 93 by the said commutators, the commutators bemg so organized as to provide a definite time interval between successive operations of the twocontact sets 92 and 93 respectively.

A ringing source of current and auxiliary apparatus, common to a plurality of switch mechanisms, is shown as a ringing generator GN, an interrupter INT, and a resistance lamp LP. A. source of busy tone current BZ, common to a plurality of switch mechanisms, is also indicated in the drawing.

lVhereas aplurality of sources of operating current is shown in the drawing for the purpose of simplifying the same, it will be understood if desired only a single source of such a continuous source of current may be used, the'various circuit conductors leading to the two poles of the various illustrated sources then being multiply connected to the two poles of a singlesource, Thus having therefore set forth the various operative parts of the system of my invention, a narrative of a sample operation of the same will now be had to better describe the functions to the second row of terminals.

of the various parts and of the results achieved by the co-operative action of the various elements.

In this narrative of operation it will be assumed that the substation A is the calling substation and the substation B is the called one of a plurality of other substations, and the description will be made with the assumption that the called line is idle and a connection therefore had with the called line, and also description of the system as operated when the called line is busy will be had.

The subscriber at substation A, upon removing his receiver 9", closes a circuit to operate the line relay LR of line switch L as follows: ground G, terminal 3 and wiper 4 of line switch L, contact 5 of cut off relay CO, line conductor 2, contact 6 of, relay (1 at substation A, impulse contact 7, transmitter 2?, switch hook contact 8, induction coil 2', line conductor 1, contact 9 of relay CO, line switch wiper 10 and terminal 11 thereof, winding of line relay LR to the source of current. The line relay Llt'operates and closes the following circuit to operate the line switch cut off relay CO z-ground GA, contact 12 of relay LR, terminal 13 and line switch wiper 14, winding 15 of relay CO to the source of current. This ground GA also is extended, from wiper 14 by way of terminal 16 and line switch wiper 17, to connector terminal 18, which path causes the calling line to test busy to incoming calls the instant the line relay LR operates. The cut off relay CO operates over the previously traced circuit and breaks the original circuit of relay LR at contacts 5 and 9. Before this circuitis broken, a substitute circuit is provided for relay LR at its own contacts 19 and 21 and thecontact of relay CO. A circuit is now closed for operating the line switch stepping magnet ST as follows z-ground GA, contact 22 of relay LR, terminal 23 and line switch wiper 24, contact 25 of relay CO, contact 28 and winding 29 of stepping magnet ST to the source of current. The mag net ST energizes its armature, breaks its own circuit at contact 28. and, upon retracting its armature, moves the wipers 4, 10, 1.4, 17 and 24 one step, i. e., from the first Wiper 14 breaks the original circuit for relay CO but, assuming the trunk to which the second row of terminals leads to be busy, this relay does not release because of the following locking circuit rground GB, contact 26 of a relay like CO, wiper 24 and terminal 81 of a line switch like L which is using this trunk, by way of the line switch bank multiple to terminal 31 of this calling line switch L, wiper 24, contact 27 of relay CO, winding of relay CO to, the source of current. This busying ground .also causes the stepping .the impulses being sent.

magnet ST to operate byway of contact 25 of relay CO .and go to the third row of terminals from which point it will be advanced in the same manner as described for the first row.

' As long as the'line switch wipers are, away from their home points and on a. trunk point, ground GC is extended by way of wiper 17 to the connector terminal 18, to cause the line to test busy.

- The cut off relayCO now releases, because there is noground on either winding, and extends the line conductors 1 and 2 to. the connector CN by way of contacts 5 and 9 and line switch wipers 4 and 10. Ground connection GB is now extended through con tact 26 of relay CO, wiper 24 and terminal 32 of line switch L, to trunk wire 33 leading to the connector CN, for busying this trunk and thereby causing other line switches like L to pass over this multiple on their banks. The relay CO, upon releasing,

breaks the circuit of relay LR at contact 20 which allows LE- to release.

The closed circuit of the calling line is new extended to the connector CN and causes relays T and R to operate over the following circuit :-ground GD, winding of relay T, connector trunk wire 34, terminal 2-35 and wiper 4 of line switch L, contact 5 of relay CO, line conductor 2, previously traced closed circuit of substation A, line conductor 1, contact 9 of relay CO, wiper 1O and'terminal 36 of line switch L, connector trunk wire 37, winding of relay R to the source of current. Both relays T and 13 now energize R closing the following circuit :-ground GE, contact 39 of relay R, terminal 40. and wiper 41 of change-over switch CHO, contact 42 and winding of change-over switch stepping magnet M0 to the source of current. Mag net MO now energizes, breaks its own circuit at contact 42, retracts its armature and moves wipers 41, 43 and 44 in a clock-wise direction to the second set of terminals.

Assuming the subscriber at substation A to be calling the subscriber at substation B, lBs number being20; as the calling device is pulled forward contact 45 opens and contacts 46 and 47 close, 46 short circuitingthe transmitter t to eliminate its variable resistance from theline circuit during inpulsing and 47 short circuiting the primary induction coil 2' so that thecalling subscriber will not hear the objectionable clicks caused by As-the dial returns, the substation impulse springs 7 are operated twice (the first digit of the desired number being 2) momentarily, each time breaking the circuit of the connect-or relays T and R, both ofthem releasing. At the first break, relay Rclos'es the following circuit: ground GE, contact 48 of relay R, terminal 49 and wiper 41 of switch CHO, 0011- tact 42 and winding of magnet M0 to the" source ofrcurrent. This causes switch CHO to advance its wipers" 4-1, 43 and tt to the third row of terminals. This same ground GE by way of contact 48 of relay R also extends to wiper i lof switch CHO, terminals 50,01 51, connector side switch wiper 52,'and first position contact thereof, winding of primary magnet PM to the source of current. The wire to connector side switch v52 is multipled to points 50, 51 and 53 of switch CHO wiper 44 and is for the pur JOSG of delivering the fullimpulse of relay to the connector switch operating magnet. To prevent this circuit being interrupted as wiper Mcxmoves from one point to another,

the wiper. is "made bridging, i. e., it makes connection with the succeedmgcontact before breaking from the preceding. contact.

2&60

vT operates and, as before,.closes a circuit from ground GD, contact 54: of relay'T, te"r-' minal and wiper ell-of switch CHO, 0011- v a tact 42 and winding of magnet MO.

Calling device impulse contact 7 is now closed, whereupon relays T and R energize, T,.clos1ng. the following c1reuit:'ground GD, contact ofrelay T, terminal 55 and wiper ll of switch. CHO, contact 42 and winding of stepping magnet MO. This causes wipers MA?) and 4:4: to advance to the fourth set of terminals Where the same circuit again operates magnet MO and moves the wiipers 4:1, 43 and 44- to the fifth set of terminals. Here the following circuit is -ClOSECi :-ground GE, contact 39 of relay R,

terminal 60 and wiper 41 of switch-CHO, contact 42 andv winding of stepping magnet MU to the source of current. This causes theswitch CHO to advance to the next set of terminals, which is the first, and from here the same circuit by way of terminal 10 again steps the wipers .41, 43 and tr tothe second set of terminals.

Call ng device contact '7 lSDOWQgEL'HI opened, causingthe same series of operations as before, i. e., CHO switch wipers 41,

and 44; will advance to the third row of terminals and another impulse will be delivered to the connector primary'magnet PM; as previously described for the first break of contact?- at substation A. Immediately after this second opening of contact 7, contacts 46 and 47 are opened and contact 45 is closed. This places relay C, of

"the substation apparatus, in the line circuit for a sufficient time, before the closure of contact 7, for relay C to operate. 7 Relay C, in operating, breaks its contact (3 which T5 5 opens the path for the'short circuit around its windingplaced there byv the closure of contact 7. .Relay C is of suflieiently high resistance .to prevent the operation of marginal relay R at the connector CN, but will permit. sensitiverelay T to operate. Relay This causes CHO switch wipers 4L1, 43 and l i to change-over advance to the fourth position and here the same circuit by way of terminal 56 causes ing circuit is now closed: ground GF, off

normal contact 66, contact 67 of busy relay BY, connector s1de switch wiper 65 and first position thereof, contact 64- of the escape magnet ESC, winding of relay R to the source of current. This causes three things to happen, first, relay R energizes, second, because of the short circuit placed on the calling. line by thi above traced circuit, the

'relay G at substation A releases and short circuits itself, third, relay T tie-energizes and opens the locking circult of the escape magnet ESQ, which releases and takes the short circuit off the'line, allowing relay R to again energize; RelayC does not energize at this time because it will be short circuited by the impulse contact '7 and its own contact 6, the last" closure of impulse contact 7 having taken place before these other functions, which have been described, .had time to occur.

Ftelay R, upon energizing, causes wipers-41,.4l3 and H of switch CHO to advance to the second setof terminals over the circuit previously traced. Magnet ESC, upon tie-energizing, allows the connector side switch wipers '52, 65, 68, 9 and-70 to' advance. to the second position.

From the foregoing it .will be seen that,

operations which the different parts perform :Firstconnector seized, changeover switch moved one step. Secondopening of' calling device impulse springs, connector wipers stepped to first level and switch moved one step. Third-closure of calling device impulse springs, change-over? switch moved four steps, coming to rest on the second point. Fourth-opening ofcalling device impulse springs, connector w ipers stepped to second level and change-over switch moved one step. Fifth--closure ofcalling devicecircuit through high resistance coil C, changeover switch moved twosteps, coming to rest on the fifth point; Sixthescape magnet operates, restores the telephone and switch circuits to the starting point for the second digit, i. e., change-over switch to its second point, side switch wipers in second position and the 2000 ohms resistance at telephone short-circuited. Thus it will'be seen that the change-over? switch when the calling subscriber. dials the first digit, 2, the following is the sequence of CHO makes one complete cycle, coming to rest on the second set of terminals, for each impulse (opening and closure) sent in from the calling device: and after the last impulse of the series has been sent, this change-over switch stops at the fifth set of terminals and causes the connector circuit to be switched from the primary to the secondary operating magnet.

The calling'subscriber now operates his dial for the second digit, 0, of the called number, causing the apparatusto function as before except that this time ten, instead of 2,impulses will be delivered to secondary magnet SM because number 0 is pulled on the dial and because side switch wiper 52 is in second position. This circuit to magnet SM goes through contact 71 of relay BY so that. if the dial is again turned without releasing on acall to a busy line, the connector switch wipers will not be advanced, and a wrong connection made.

lVhen the second change-over is made, in the same way as the first, the changeover switch wipers 41, 413 and 44: are left on the second point and the side switch wipers 52, 65, 68,69 and are moved to the third position when the following circuit is closed :ground GG, side switch wiper 68 and third position thereof, connector wiper 5'7, called line terminal 72. sleeve trunk 73 to called line switch M, line switch wiper 7%, terminal 75, winding 76 of cut off relay 0G to the source of current. This energizes the called line switch out off relay 0C, opens the line switch battery bridge of the called line at contacts 77 and 78 and closes the following circuit to ring the called partys bell :-common A. C. generator GN, common interrupter INT, common lamp LP, winding of generator cut off relay TR, side switch wiper 70 and third position thereof, connector wiper 59 terminal 80, ring trunk 81 to called line switch M, called lineconductor S2, ringer 1" 2' at substation B, con denser 7c, impulse contact 83, contact 84 of relay 1), line conductor 85, tip trunk 86 of called line switch, connector terminal 87, connect-or wiper 58, side switch wiper 69 and third position thereof, ground GH, through the battery and common resistance coil SE to the other side of the common generator GN. lVhen't-he side switchwipers went to third position the following circuit was closed to energize the escape magnet ESCc-ground GF, off normal contact 66, contact 67 of relay BY, side switch wiper and third position thereof, winding 62 of magnet ESQ, resistance coil RS to the source of current.

hen the called subscriber answers, a direct current path is closed at switch hook contact 79 in the above traced circuit which causes relay TR to operate and close the following circuit :--ground GJ, contact 88 of relay TR, through resistance coil RS to battery. This short circuits the escape magnet winding 62, allowing it to release and advance the side switch wipers, 52, 65,68, 69 and 70 to the fourth position. Herethe talking current for the called party, fed through impedance coil AB, is substituted for the ringing current above described, by side switch wipers 69 and 7 0 moving from the third to'the fourth positions. The talking battery for the calling substation transmitter is fed through relays T and R and thepath for the voice currents is through condensers 105 and 106.3

After the conversation is completed the connection is released, by the hanging up of the receiver 1 at the calling substation A, in the following manner :by opening the circuit at hool: switch contact 8, relays T and R at connector switch CN de-energize, Relay R, by closing its contact e8, causes the change-over switch CHO to move ,to' position three where the following circuit is closed :ground GD, contact 89 of relay T, terminal 90 and wiper 43 of .changeover switch CHO, winding of relay BL and contact 91thereof, common interrupter contact 92, common resistance coil ES to the source of current. It may here be mentioned that interrupters 121 and 122 are common to the exchange and are turned in the. direction indicated by the arrows by the same shaft 113. Therefore when the above circuit is closed, the interrupter contact 92 may or may not be closed, if not'closed noth ing will happen until interrupter 122 gets to the point where it causes the closure of contact 92. When this circuit is completed, relay RL operates, locks by way of its contact 95, and resistance coil SE, opens its energizing circuit at contact 91 and closes its contact 94. Now, after a certain time interrupter 121 closes contact 93, this time being sufficient to inalre sure that this is the release condition and not an impulse opening. If relay RL was operated during impulsing, it would release before interrupter 121 could close its contact and cause a release of'the switch, because it would (lo-energize when relay T again energized and opened contact 89. When 121 interrupter contact 93 is closed, the following circuit is established:ground GK, interrupter contact 93, contact. 94 of relay BL, contact 96 and winding 99 of connector release magnet REL to the source of current. This energizes the release magnet which locks from ground GL, low winding 1'00- and contact 102 of magnet REL, resistance coil RE to the source of current. The connector switch wipers and side switch wipers are now restored to normal when contact 103 is opened. A circuit is also traced from ground GL, winding 100' and contact 102 of magnet REL, connector trunk wire 38, terminal 104 and wiper lt of line switch L, winding 15 ofcut off relay CO tothe source of current. This circuit energizes the line switch out off re-.

1 lay CO and keeps the connector release magnet REL locked. A circuit may now be traced from ground GL, winding 100 and contact 101 of magnet REL, connector trunk wire 83, terminal 32' and wiper 24 of line switchL, contact 25 of relay CO, contact, 28 and Winding 29 of line switch stepping magnet ST to the source of current, which causes the calling line switch L to take a step and go to its home point ready for use in again selecting an idle connector. WVhen connector (1N restored its wipers to normal, the cut oflrelay, 0C of the called line switch M was released. The following circuit is also closed to cause the release of the change-over switch CHO ground GD, terminals. 90, 114: and 115 of switch CHO, wiper 43 of switch'CHO, con-.

tacts 97; and 98 of connector release magnet REL, contact 12 and winding MO of switch CHO to the source of current. In multiple withthis circuit'is winding 99 of magnet REL to the source of current. Thus the connectorrelease magnet, upon energizing, will remain locked until the-connector shaft reaches normal, until the line switch L is released and until the change-ovei switch CHO is restored to normal, whereupon magnet REL and relay R L are de-energized. llntil magnet REL is ole-energized, ground GL, low winding 100 and contact 101 of magnet REL, is maintained in connection with multiple terminal 32 of all line switches in the group to keep thistrunkbusy.

A call to a busy line will now be described. Assuming that the same number, 20, was dialed and that, at the end of the second digit, the escape magnet ESC operates as before, relay R will be energized, relays'C and T will be (lo-energized and switch CHO will rest on point 2. Escape magnet ESQ willnot release at this time because of the following locking circuit :-ground on terminal 72, (placed there either from side switch wiper 6S and wiper 57 of some connector like CN which has called this same number or, if the subscriber having this number has made av call, a ground will be placed on terminal 72 in the same manner as was previously described for placing aground on terminal18 by line switch L} connector wiper 57 side switch 68 and second position thereof, contact 110 of relay BY, winding of relay BY, contact 108 of escape magnet ESQ, winding 107 of magnet ESC to the source of current. This circuit also causes relay BY to energize and lock itself in series with magnet ESQ, holding them both, from ground GF, off normal contact 66, contact 109 of relay BY, winding of relay BY, contact 108 and winding 107 of off, relay CO, calling line-conductor .2,-

through the substation apparatus A, line conductor 1, contact 9 of relay CO, line switch wiper 10 and contact 36, connector trunk wire 37, winding of relay B, through the battery to ground GE and then to the other side of busy induction coil BZ. This gives the calling subscriber a tone which in dicates that the called forline is busy and when he hangs up his receiver, the connection is released inthe same manner as pre-* viously described.

From the above narrative it is apparent thatI have evolved a system wherein neither primary impulse relays T and R need to be relatively slow operating, or may both operate at the same speed or at slightly different speeds, and in connection with such relays I have evolved a system wherein the change-over function is, performed positively, and wherein the release of the switch is accomplished in a positive way without dependence being placed upon the co-operation of fast and slow relays; also that this is accomplished in a system free from any necessary grounds at the substations or third wire connectionethereto; a full use of a metallic talking circuitat the same time being had.

1am aware that numerous and extensive departures may be made from the embodiment of my invention illustrated and described but without departing from the spirit thereof. -For instance, I am aware that other equivalent means may be provided for many of theelements herein specifically discussed, but what I claim as my invention is defined in the following claims 1. In a telephone system, the combination with aplurality of substations, a main station, switching mechanism at the main station adapted to make connection with a desired called substation, line conductors connecting the said switching mechanism and a calling substation, a circuit interrupter at the substation and a source of current associated with the said, switching mechanism, means to cause the said circuit interrupter to interrupt the circuit of the line conductors a definite, predetermined number of times, means operative upon the subsequent closure of thesaidline conductors by the said interrupter to interpose a high resistance in said circuit, a pair of relays for controlling the said. switching mechanism under the control of the said c rcuit lnterrupter,

each of the said relays being responsive to circuit closures with normal current flowing over the line conductors, and only one 01' thev said relays being responsive to the closure of the said line conductors through the said resistance.

2. In a telephone system, the combination with a plurality of substations, a. main sta tion, switching mechanism at the main station adapted to make connection with a desired called substation, line conductors connecting the said switching mechanism and a calling substation, a circuit interrupter at the substation and a source of current associated. with the said switchingv mechanism, means to cause the said. circuit interrupter to interrupt the circuit oi the line conductors a definite predetermined number of times. means operative upon a subsequent closure of the saidline conductors by the said interru 'iter to interpose a high resistance in said circuit, a pair of relays for controlling the said switching mechanism under the control of the said circuit interrupter, each of the said relays being" responsive to circuit closures with normal. current flowing over the'line conductors,and only one of the said relays being resoonsive to the closure of the saidv line conductors through the said re sistance, and change-oven switching means adapted to be operated under the jointcontrol oi the said pair of: relays when one of the said pair is operated and the other relay is quiescent.

3. In a telephone system, the combination with a plurality of substations, a main station, switching mechanism at the main station adapted to make connection with a desired called substation, line conductors connecting the said switching mechanism and a calling substation, a circuit interrupter at the substation and a source of current as sociated with the said switching mechanism, means to cause the said circuit interrupter to interrupt the circuit of the line conductors a definite predetermined number of times, means operative upon a subsequent closure of the said line conductors by the said interrupter to inter-pose a high resistance in said circuit, a pair of relays for controlling the said switching;- mechanism under the control of the said circuit interrupter, each of the said relays being re sponsive to circuit closures with normal current flowing over the line conductors, and only one of the said relays being responsive to the closure of the said line conductors through the said resistance. change-over? switching means adapted to be operated under the joint control of the said pair of re lays when one of the said pair is operated and the other relay is quiescent and means to prevent the operation of: the said changeover switching means when both of the said relays are operated.

i. In an automatic telephone systcm,'the combination with telephone lines, substations for the lines, a main station wherein the lines terminate,switching mechanism at the main station, means to interlinlr a calling line with the said switching mechanism, a pair oi relays controlling the said switching mechanism under the control of calling substation apparatus, a circuit interrupter at the substation, means to variably operate the said circuit interrupter to interrupt the circuit or the calling line a predetermined number of times, means to include a resistance in circuit withthe said line after the end of each series of circuit interruptions, a source of current, and circuit connections to cause the operation of each of the said relays at each normal closure of the line circuit, one of the said relays being irresponsive to the said closure through the said resistance.

5. in a telephone system, the combination with a plurality of substations, a main station, switching mechanism at the main station adapted to maize connection with 'a desired *alled substation, line conductors connecting the said switching; mechanism and a calling substation, a circuit interrupter at the substationand a source of current associated with the said switching mechanism, means to arise the'said circuit interrupter to interrupt the circuit of the line conductors a definite predetermined number of times, means operative upon a subsequent closure of the said line conductors by the said interrupter to interpose a high resistance in said circuit, a pair of relays for controlling the said switching mechanism underthe control of the said circuit interrupter, each of the said relays being" responsive to circuit closures with normal current flowing over the line conductors, and only one of the said relays being responsive to the closure of the said line conductors through the said resistance, changeover switching means adapted to be operated underthe joint control. of the said pair of relays when one of the said pair is operated and the other relay is quiescent, locking means for the said resistance interposing means at the substation, and unlockmeans for the said locking means under the control of the said change-owl switching means.

6. In a telephone system, the combination with a plurality of substations, a main station, switching mechanism at the main station adapted to make connection with a desi d 'callcd substation, line conductors conhearing the said switching mechanism and a calling substation, a circuit interrupter at the substation and a source of current associated with the said switching mechanism, means to cause the said circuit interrupter to interrupt the circuit of the line conductors a definite predetermined number of control of the said pair of relays when one oi? ,ing means.

' the said pair is operated and the other relay is-quiescent, means to prevent the operation oi? the'said change-over switching means when both oi the said relays are operated,

locking means for the said resistance inter- 20 posing means at the substation, and unlocking means for the said lockingmeans under the control of the said change-over? switch- 7. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, switching mechanism at the main station, means to interlink a calling line with the said switching mechanism, a pair of relays controlling the said switching mechanism under the control of calling srnstationapparatus, a circuit interrupter at the substation, means to variably operate the said circuit interrupter to interruptthe circuit of the calling line a predetermined number of times, means to include a resistance in circuit with the said line after the end oi each series 01 circuit interruptions, a source of current, circuit connections to cause the operation ot' each of the said re- 2 at each normal closure of the line cir- 'cuit, one of the said relays being iii-responsive to the said closure through the said'resistanco, and changebvcr switching means adapted to be operated under the joint control ot' the said pair Oil relays, when one of the said pair is operated and the other is quiescent.

In an autoi'nat-ic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, switching mechanism at the main station, means to interlink a call- .ing line with the said switching mechanism, a pair of relays controlling the saidswitchins: mechanism under the control olicalling substation apparatus, a circuit interrupter at the substation, means'to variably operate the said .circuit interrupter to interrupt the (in cult of the calling line a predetermined numher of times, means to include a resistance in circuit with the said line after the end of each series oil circuit interruptions, source of current, circuit connections to cause the operation'ot each of the said relays ateach normal closure of theline circuit, one of the said relays beingirresponsive to the said closure through the said resistance, changeover switching means adapted to be operated under the joint control'of the said pair of relays, when one of the said pair'is' operated and the other is quiescent, and means to prevent the operation of the said -change-ove1 switching means while both of the said relays are operated.

9. In an automatic telephone system, the combination with telephone lines, substa tions for the lines, a main station wherein the lines terminate, switching mechanism at the mainstation, means to interlink a call-' 111;); line with the said switchlng mechamsm,

tions to cause the operation of each of the.

said relays at each normal closure of the line circuit, one of the said relays being irresponsi-ve to the said closure through the said resistance, change-over swltchlng means adapted to be operated under the.

joint control of the said pair of relays when one of the said pair is operated and the other is quiescent, locking means for the said resistance interposing means"at the substation, and unlocking means for the said locking means under the control ofthe said change-over switching means. V

10. In. an automatic telephone system,the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, switching mechanism at the main station, means to interlink a calling line with the said switching mechanism, a pair of relays controlling the said switching mechanism, under the control of calling substation apparatus, a circuit interrupter at the substation, means to variably operate the said circuit interrupter to'interru pt the circuit of the calling line a predetermined number of times, means to include aresistance in circuit with the said line after the end of each series of circuit interruptions, a source of current, circuit connections to cause the operation of each of the said relays at each normal closure of the line circuit, one of the said relays being irresponsive to the said closure through the said resistance, change-over switching means adapted to'be operated under the joint control oi the said pair of relays, when one of the said pair is operated and the other is quiescent, means to prevent the operation of the said change-over switching means while both of the ,said relays are operated, locking means for the said resistance interposing means at thesubstation, and unlocking means for the said locking means under the control of the said change-overswitching means. I I

11. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, switching mechanism at the main station, means to interlink a calling line with the said switching mechanism, a pair of relays directively controlling the said switching mechanism under the control of calling substation apparatus, including a substation circuit interrupter, means to variably operate the said circuit interrupter to produce successive series of calling line circuit interruptions, means including an elec tromagnet to include a resistance in series with the said line immediatelyv following each series of circuit interruptions, a source of current, and circuit connections to cause the operation of each of the said relays at each normal closure of the line circuit, one of the said relays being irresponsive to the final closure after the last circuit interruption or each series through the said resistance.

12. In an automatic telephone system,the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, switching mechanism at the main station, vmeans to interlink a calling line with the said switching mechanism, a pair of relays dire'ctively controllingthe said switching mechanism under the control,

of calling substationapparatus, including a substation circuit interrupter, means to variably operate the said circuit interrupter to:

produce successive series of calling line circuit interruptions, means lncludlng an electromagnet to include a resistance-in series.

with the said line immediately following each series of circuit interruptions, a source of current, circuit connections to. cause-the operation of each of the said relays at each normal closure of the line circuit, one of the said relays being irresponsive to the. final closure after the last circuit interruption of each series through the said resistance, and

change-over switching controlling means adapted to be operated under the joint control of the said pair of relays when one of the said pair is operated and the other relay is quiescent. v

'13. In an automatic telephone system, the combination with telephone lines, substations for the lines, main station wherein the lines terminate, switching mechanism at the main station, means to interlink a calling line with the said switching mechanism, a pair of relays directively controlling the said switching mechanism under the control of calling substation apparatus, including a substation circuit interrupter,

means to variably operate the said circuit interrupter to produce successive series of calling line circuit interruptions, means including an electromagnet to include a resistance in series with the said line immediately following each series of circuit in terruptions, a source of current, circuit connections to cause the operation of each of the said relays ateach normal closure of the line circuit, one of the said relays being irresponsive to the final closure after the last circuit interruption of-each series through the. said resistance, change-over switching controlling means adapted to be operated under the joint control of the said pair of relays when one of the said pair is operated and the other relay is quiescent, a locking circuit for the said electromagnetic resistance including means, means to maintainthesaid locking circuit operative under the control of the said electromagnet after an initial operation thereof, and circuit unlocking means responsive to the complete operation of the said change-over means to unlock the said circuit to disable the said resistance including means.

14;. In an automatic telephone system, the combination with telephone lines, substations ior the lines, a main station wherein the lines terminate, switching mechanism at the main station, means to interlink a calling line with the said switching mechanism, a pair of relays directively controlling the said switching mechanism under the control of calling substation apparatus, including a substation circuit interrupter, means to variably operate the said circuit interrupter to produce successive seriesv of calling line cir cuit interruptions, means including an e1ectromagnet to include a resistance inseries with the said line immediately following each series of circuit interruptions, asource of current, circuit connections to cause the Operation of each of the said relays at each normal closure of the line circuit, one ofthe said relays being irresponsive to the final closure after the last circuit interruption of each series through the said resistance, change-over, switching controlling means adapted to be operated under the joint control of the said pair of relays when one of the said pair is operated and the other relay is quiescent, and means to prevent the operation of the said change-over switching means during the period wherein at any time both of the said relays are operated.

15. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main stationwherein the lines terminate, switching mechanism at themain station, means to interlink a calling line with the said switching mechanism, a pair of relays directively controlling the said switching mechanism under the control of calling substation apparatus, including a substation circuit interrupter, means to vari-f ably operate the said circuit interrupter to produce successive series of call ng line 011'- cuit interruptions, means including an electromagnet to include a resistance in series with the said'line immediate following each series of circuit interruptions, a source of current, circuit connections to cause the operation of each of the said-relays at each normal closure of the line circuit, one of the said relays'being' irresponsive to the final closure after the last circuit interruptionof each series through the said resistance, changeover switching controlling means adapted to' be operated under the joint control of the said pair of relays when one of the said pair is operated and the other relay is quiescent, meansto prevent theop'eration of thesaid change over switching means during'the period wherein at any time both of the said relays areoperated, a locking circuit for the said electromagnetic resistance including means, means to maintain the said locking circuit operative under the control of the said electromagnet after an initial operation thereof, and circuit'unlocking means responsive to the complete operation of the said change-over"means to unlock the said circuit to disable the said resistance including means.

16. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, an automatic numerical switch at the main station, anon-numerical switch to interlin'k a callingline with the sa1d numerical switch, a pair of relays for the said numerical switch, means at the sub-'- station toiproduce successive series of circuit interruptions, means at the substation to operate both of the said pair of relays substantially in unison during each circuit interruption of a series, substation controlling means for differently operating the relays for a period immediately following the-last circuit interruption of a series, a plurality of operating magnets for the said numerical switch, one of which is operative under said substation control to move the switch in a primary direction during a first series of circuit interruptions, a second of which is operative to be moved in a secondary direction during a second series of circuit interruptions, change-over means to'remove the primary 5 operating magnet from the control of the said pair of relays and to place the secondary operating magnet under the control of the said pair of relays, and means to cause the operation of the said change-over means responsive to the differently operated pair of relays under the control of thesaidsubstation controlling means.

17. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, an automatic numerical switch at the main station, a non-numerical switch-to interlink a calling line- -vvith the said numerical switch, a pair of relays for the said numerical switch, means at the substation to produce successive series of circuit interruptions,- means at the substation to operate both of the said pair of relays substantially in unison during each circuit interruption of aseries, substation controlling means for differently and continuously. operating the relays for a period immediately following the last circuit interruption of a. series, a plurality of operating magnets for the said numerical switch, one of which is operative under substation control to move the switch in a primary direction during the first series of circuit interruptions, a second of which is operative to-move the switchlin a secondary direction during a second series of circuit interruptions, change-over means to remove the primary operating magnet fromthe control of the said pair of relays and to place the secondary operating magnetunder the control of the said pairof relays, means to cause the operation. of the said change-over" means responsive to the condition of the differently operated pair of relays resulting from the control of the said substation controlling means, and separate controlling means for the said numerical switch to prevent improper operationof the said switch due to differing response rates forthe said relays to circuit interruptions.

18. In'an automatic" telephone system, the. combination with telephone lines, substations for the lines, a main station wherein the lines terminate, an automatic numerical switch at themain station, a non-numerical switch to interlink a calling line with thesaid numerical switch, a pair of relays for, the said numerical switch, means at the substation to produce successive series of circuit interruptions, means at the'substation to operate .both of .the said pairof relays substantially in unison during each circuit interruption of a series, substation controlling means for differently and continuously operating the relays for a period immediately,following the last circuit interruption of a series, a plu-, rality of operating magnets for" the said numerical switch, one of which is operative under substation control to move the switch in a primary direction during the first'series of circuit interruptions, a second of which is operative to movethe switch in a secondary direction during a second series of circuit interruptions, changeover means to remove the primary operating'magnet from the control of the said pair of relays and to'place the secondary operating magnet under the controlof the said pair of relays, means to cause the operation of the said changeover means responsive to the condition of the differently operated pair of relays resulting from the control of the saidsubstation controlling means, and separate controlling means tor'the said numerical switch to prevent improper operation of the said changeover means due to differing response rates for the said relays to circuit interruptions.

19. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, an automatic numerical switch at the main station, circuit connections interlinking a calling linewvith the said numerical switch, a pair of relays for the said numerical switch, means at the substation to produce successive series of circuit interruptions, means at the substation to operate both of the said pairof relays substantially in unison during each circuit interruption of a series, substation controlling means for differently and continuously operating the, relays for a period immediately following the last circuit interruption of a series, a plurality of operating magnets for the said numerical switch, one of which is operative under substation control to move the switch in a primary direction during the first series of circuit interruptions, a second of which is operative to move the switch in a secondary direction during a second series of circuit interruptions, change-over means to remove the primary operating magnet from the control of the said pair of relays and to place the secondary operating magnet under the control of the said pair of relays, means to cause the operation of the said changeover *means responsive to the condition of the differently operated pair of relays resulting from the control of the said substation controlling means, and correcting means under the joint control of the said pair of relays to prevent the improper operation of the said change-over means or" the said numerical switch, due to the said relays operating at different rates of speed. 20. In an automatic telephone system, the combination with telephone lines, substations for the lines, a main station wherein the lines terminate, an automatic numerical switch at the main station, circuit connections interlinking a calling line with the said numerical switch, a pair of relays for the said numerical switch, means at the substation to produce successive series of circuit interruptions, means at the substation to operateboth of the said pair of relays substantially in unison during each circuit interruption of a series, substation controlling means for differently and continuously operating the relays for a period immediately following the last circuit interruption of a series, a plurality of operating magnets for the said numerical switch, one of which is operative under substation control to move the switch in a primary direction during ill the first series of circuit interruptions, a second of which is operative to move the switch in a secondary direction during a second series of circuit interruptions, change-over means to remove the primary operating magnet from the control of the said pair of relays and to place the secondary operating magnet under the control of the said pair of relays, means to cause the operation of the said change-over means .responsive tothe condition ofthe differently operated pair of relays resulting from the control of the said substation controlling means, a step-by-step switch for the said numerical switch operating under the control of one of the said relays in response to the said circuit interruptions and circuit connections jointly controlled by the said pair of relays, and contacts of the said stepby-step switch to prevent improper operation of the said changeover means on account of the slight differences in the speeds of action or release between the said relays in response to the said circuit interruptions.

21. In a telephone system, the combination with a plurality of telephone lines, substations for the lines, a main station, a selective switch at the main station adapted to interconnect two of the said telephone lines, a source of current, a relay in the circuit of the said source of current leading to a substation of a connected line, a release magnet, a release relay, a timing mechanism, a pair of circuits successively con trolled thereby, there being a predetermined interval between the control exercised by the said timing mechanism on the one circuit and the control exercised by the said timing mechanism upon the second circuit, circuit connections to include in the said first circuit a. winding of the said release relay, a SOUTCG'OTf current, contacts of the said substation circuit relay and controlling contacts of the said timing mechanism, circuit connections for the second circuit comprising a winding of the said release magnet, contacts of the said release relay, and controlling contacts of the said timing mechanism.

22. Inan automatic telephone system an automatic selective switch for interconnecting telephone line substations, a telephone line substation controlled relay, a release magnet for the said switch, a release relay, a

pair of continuously successively operating controlling sets of contacts, a circuit for the said release relay comprising a first operated set of controlling contacts and contacts of said substation controlled relay, and a circuit for said release magnet comprising said second operated set of controlling contacts and contacts oi the said release relay.

In an automatic telephone system, the combination with an automatic selective switch for interconnecting telephone line substations, a'telephone line substation controlled relay, a release magnet tor the said switch, a release relay, a pair of continuously successively operating controlling sets ofcontacts, a circuit for the said release relay comprising a first operated set of controlling contacts and contacts of said substation controlled relay,'a circuit for said release magnetcomprising said second operated set of controlling contacts. and contacts of the said released-clay, and a locking circuit for the said release relay under the control of oii normal contacts ofthe said switch.

2%. In an automatic telephone system, an automatic selective switch for interconnecting telephone line substations, a telephone line substation controlled relay, a release magnet for the said switch, a release relay, a pair of continuously successively operating controlling sets of contacts, a circuit for the said release relay comprising a first operated set of controlling contacts and contacts of said substation controlled relay, a circuit for said release magnet comprising said second operated set of controlling contacts and contacts of the said release relay, and other automatic selective switches for interconnecting other pairs of telephone lines, said pair of sets of controlling contacts being common to all of the said automatic selective switches. p

25. In an automatic telephone system, the combination with an automatic selective switch for interconnecting telephone line substations, a telephone line substation controlled relay, a release magnet for the said switch, a release relay, a pair of continu-' ously successively operating controlling sets of contacts, a circuit for the said release relay comprising a firstoperated set of con trolling contacts and contacts of said substation controlled relay, a circuit for said release magnet comprising said second operated set of controlling contacts and contacts ofthe said release relay, a locking circuit "for the said release relay under the control of oil normal contacts of the said switch and other automatic selective switches for.

tacts being common to all of thejsaid automatic' selective switches.

26. In a telephone system, telephone lines,"

substations on. the lines, automatic switch- 111g mechanism for interconnecting a pair of the telephone lines, a calling substation controlled relay, means to'release the said relay when the calling substation is retired,

two sets of controlling contacts adapted to be successively operated with a definite time interval between the operation of the first set and the operation of the second set, a winding of a release relay, the first set of contacts and normal contacts of the said calling substation controlled relay in a first circuit, said second set of contacts, normally,

open contacts oi"v said release relay and a winding o1 a release magnet in asecond circuit, said first circuit controllingthe said second circuit to operate the said release magnet, and means including off normal contacts ofthe said switching mechanism under the control of the said release magnet for controlling the said release relay.

2?.) In a telephone system, telephone lines, substations for the lines, automatic switching mechanism for interconnecting a pair of the telephone lines, a calling substation controlled relay, means to release the said relay when the callingsubstation is retired, two sets of controlling contacts adapted to be successively operated with a definite time interval between the operation of the first set and the operationofthe second set, a winding oi a release relay, the first set of contacts and normal contacts of the said calling substation controlled relay in a first circuit, said second set of contacts normally open contacts of said relay. and a winding of a release magnet ina second circuit, said first circuit controlling the said second circuit to operate the said release magnet, means including off normal contacts of the said switching mechanism under the control of the said release relay-for controlling the said release magnet, and" other switching mechanisms each-having a substation controlled relay, .release relays and release magnets individual to each, but said time controlling contacts being common -to all.

28. In a subscriber operated telephone system, the combination with telephone lines, substations for the subscribers on each of the lines, a plurality of switches at a'main station,'each adapted to interconnect two of the said lines, a substation controlled relay for each switch under the control of substation apparatus oi: a calling line, normally'closed and normally open contacts for the said relay, 'a source of current, a release relay, offnormal contacts of the said switch.- a pair of 'controlling'contacts in the circuit of the normal contacts of the said relay, a second pair of controlling contacts, controlling contact operating means adapted to continuously and successively'operate the said first named pair of controlling contacts and thesecond named pair of controlling contacts, a locking circuit for the said release relay adapted to operatively lock the said release relay whenever the said release relay is operated by the closure of the said firstnam'ed pair of controllingcontacts said locking circuit also being under the control of normal contacts of the substation controlled relay, a release magnet for the said switch, a winding therefor and a circuit for the said winding including a source of current, normally open contacts of the said release relay-and the second operated pair of controlling cont-acts to operate the said release relay.

29. In a subscriber operated telephone system, the combination with telephone lines, substations for the subscribers on each of the lines, a plurality of switches at a main station, each adapted to interconnect two of the said lines, a substation controlled relay for each switch under the control of substa tion apparatus or a calling line, normally closed and normally open contacts for the said relay, a source of current, a release relay, off normal contacts of the said switch, a pair of controlling contacts in the circuit of the normal contacts of the said relay, a second pair of controlling contacts, controlling contact operating means adapted to con tinuously and successively operate the said first named pair of controlling contacts and the second named pair of controlling contacts, a locking circuit for the said release relay adapted to operatively'lock the said release relay whenever the said release relay is operated by the closureot thesaid first named pair of controlling contacts, said loclring circuit also being under the control or" normal contacts of the substation controlled relay, a release magnet for the said switch, a winding therefor and a circuit for the said winding including a source of current, nor

mally open contacts of the said release relay and the said second operated pair of controlling contacts to operate the said release magnet, and a locking circuit for the said release magnet including 0E normal contacts of the said switch.

30. In a subscriber operated telephone system, the combination with telephone lines, substations for the subscribers on each of the lines, a plurality of switches at a main station, each adapted to interconnect two of the said lines, a substation controlled relay for each switch under the control of substation apparatus of a calling line, normally closed and normally open contacts for the said relay, a source of current, a release relay, off normal contacts of the said switch, a pair of controlling contacts in the circuit of the normal contacts of the said relay, a sec- 0nd pair of controlling contacts, controlling contact operating means adapted to continuously and'successively operate the said firstnamed pair of controlling contacts and the second-named pair of controlling contacts, a locking circuit for the said release relay adapted to operatively lock the said release relay whenever the'said release relay is operated by the closure of the said first-named pair of controlling contacts, said locking circuit also being under the control of normal contacts of the substation controlled relay, a release magnet for the said switch, a winding therefor and a circuit for the said wind ing including a source of current, normally opencontacts ol the said release relay and the said second operated pair of controlling contacts to operate the said release relay, a locking circuit for the said release magnet including off normal contacts of the said switch, both of sa-idpairs of controlling contacts being common to a plurality of the said switches.

31. In a subscriber. operated telephone system, the combination with telephone lines, substations tor the subscribers on each of the lines, a plurality of switches at a main'station, each adapted .to interconnect two of the said lines, a substation controlled relay for each switch under the control. or substation apparatus of a calling line, normally closed and normally open contacts for the said relay, a source of current, a release relay, off normal contacts of the said switch, a pair of controlling contacts in the circuit of the normal contacts of the said relay, a second pair of controlling contacts, controlling contact operating means adapted to continuously and successively operate the said first named pair of controlling contacts and the second-named pair ot'controlling contacts, a locking circuit for the said release relay adapted to operatively lock the said release relay whenever the said release relay is operated by the closure of the said first-named pair of controlling contacts, said locking circuit also being under the control of normal contacts of the substation controlled relay, a release magnet for the said switch, a winding therefor and a circuit for the said winding including a source of current, normally open contacts of the said release relay and the second operated pair of controlling contacts to operate the said release magnet, said controlling contact operating means being common to a plurality of the said switches.

32. In a subscriber operated telephone system, the combination with telephone lines, substations for the subscribers on each of the lines, a plurality of switches at a main station, each adapted to interconnect two of the said lines, a substation controlled relay for each switch under the control of substation apparatus of a calling line, normally closed and normally open contacts for the said relay, a source of current, a release relay olf normal contacts of the said switch, a pair of controlling'contacts in the circuit of the normal contacts of the said relay, a second pair of controlling contacts, controlling contact operating'means adapted to continuously and successively operate the said firstnamed pair of controlling contacts and the second-named. pair of controlling contacts, a locking circuit for the said release relay adapted to operatively lock the said release relay whenever the said, release relay is operated by the closure of the said first-named pair of controlling contacts,

said locking circuit also being under the control oi normal contacts or the substation controlled relay, a release magnet for the said switch, a winding therefor and a circuit for the said winding including a source of current, normally open contacts of thesaid release relay and the said second operated pair of controlling contacts to operate the said release magnet, a locking circuit for the said release magnet including oil normal contacts out the said switch, both of the said pairs of controlling contacts being common to a plurality of the said switches. I

In a subscriber operated telephone system, the combination with telephone lines, substations for the subscribers of each of the lines, a plurality of switches at a main station, each adapted tointerconnect two of the said lines, a substation controlled relay for each switch under the control of substation apparatus ofa calling line, normally closed and normally opencontacts for the said relay, a source of current, a release relay, of? normal contacts of the said switch, a pair of controlling contacts in the circuit of the normal contacts of the said relay, a second pair of controlling contacts, controlling contact operatingmeans adapted to continuously and successively 0P? crate the said first-named pair of controlling contacts and the second named pair of controlling contacts, a locking circuit for the said release relay adapted to operatively lock the said release relay whenever the said release relay is operated by the closure of the said first-named pair of controlling contacts, said locking circuit also being under the control of normal contacts of the substation controlled relay, a release magnet for the said switch, a windingtherefor and a circuit for the said winding including a source of current, normally open contacts of the said release relay and the said second operated pair of controlling contacts to op erate the said release" magnet, a locking circuit for the said release magnet including oil normal contacts of the said switch, both of the said pairs of controlling contacts being under the control of common control contact actuating means for a plurality of said switches.

34. In a telephone system, incoming circuits, a plurality of outgoing circuits, means including directively controlled automatic switches for interconnecting said incoming circuits with any of said outgoing circuits, acontrolling circuit for'each switch'including two sides of an incoming circuit in series, each switch being advanced in responseto momentary interruptions of its controlling circuit and arranged to be released in response to a long interruption of its controlling circuit, and a mechanical device common to a plurality of said switches for preventing the release of any of saidautomatic switches during momentary interruptions of its controlling circuit.

35. In a telephone system, an incoming line, a plurality of outgoing :lines, an automatic switch for interconnecting said incoming line with any of said. outgoing lines, a controlling circuit for. said switch including two sides of said incoming line in series, said switch being advanced in response to momentary interruptions of said controlling circuit and arranged to be released in response to a long inter-- ruption of its controlling circuit, and a constantly'operating device for preventing the release of said automatic switch during momentary interruptions of its controlling. circuit.

36. In atelephone system, an incoming line, a plurality of outgoing lines, an auto.- matic switch for interconnecting said incoming line with any of said outgoing lines, a controllingcircuit for said switch including. two sides of said incoming line in series, said switch being advanced in response to momentary interruptions of said controlling circuit and arranged to be released in response to a long interruption of its controlling circuit, and a constantly rotating device for preventing the release oi said automatic switch during momentary int'erruptionsof its controlling circuit.

T 37.-In a telephone system, an incoming line, a plurality of outgoing lines, an automatic switch forinterconnectingsaid incoming line with any of said outgoing lines, a controlling circuit for said switch I in: cluding two sides of said incoming line in series, said switch being advanced in response to momentaryinterruptions of said controlling circuit and arranged to be released in. response to a long interruption-of its controlling circuit, and a uni-directional rotary circuitclosing switch for preventing the release of said automatic switch during momentary interruptions of its controlling circuit. v

38. In a telephone system, an incoming line, a plurality of outgoing lines, an automatic switch for interconnecting said incoming line with any of said outgoing lines,

a controlling circuit'for said switch includ-- ing two sides ofsaid incoming line in series, said switch beingadvanced in response to momentary interruptions of said-controlling circuit and arranged to be released in response toalong interruption of its controlling circuit, and a constantly rotating interrupting device for preventing the release of said automatic switch during momentary interruptions of its controlling circuit.

39. In a telephone system, an incoming line, a plurality of outgoing lines, an automatic switch for interconnecting said incoming line, with any of said outgoingvlines, a

telephone line circuit, a cut-off relay associated with each telephone line circuit and controlled over a selected trunk circuit to disconnect said line relay from its associated line during conversation and to re-connect said line relay to said telephone line at the close of conversation, releasing means for said non-numerical switch, a timing device common to a plurality of non-numerical switches and means including said timing device and a cut-off relay for operating said releasing means.

In testimony whereof, I hereunto subscribe my name this 22nd day of Jan, A. D. 1919.

- lVINFEED T. PO /VELLQ