US1572222A - Telephone switching system - Google Patents

Description

Feb. 9 1926. 1,572,222

' w. T. POWELL TELEPHONE SWITCHING SYSTEM Filed March 31 lglg 4 Sheets-Sheet 1 INVENTOR WINFRED T POWELL ATTORN EY TELEPHONE SWITCHING SYSTEM Filed March 31 1919 LKC 4 Sheets-Sheet 2 INVENTOR wmFRED T. POWELL.

ATTORNE Feb. 9 1926. 1,572,222

W. T. POWELL TELEPHONE SWITCHING SYSTEM Filed March 31 3 9 9 4 Sheets-Sheet 3 IN'VEENTOR WLHFRED 1-. POWELL M 4! i ATTORNEY Feb. 9 1926.

W. T. POWELL TELEPHONE SWITCHING SYSTEM Filed March $1 1919 4 Sheets-Sheet 4 INVENTOR \NIHFRED T POWELL ATTORNEY Patented Feb. 9, 1926 UNITED STATES PATENT OFFICE.

WTNIRED T. PO'WELL, OF ROCHESTER, NEW YORK, ASSIGNOR TO THE STROMBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK,

A CORPORATION OF NEW YORK.

TELEPHONE SWITCHING SYSTEM.

Application filed March 31, 1919. Serial No. 286,359.

To all whom it may concern:

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

lVhile my invention is capable of many and varied uses its principal value I believe will be in connection with that type of auto matic telephone switching systems wherein a relatively small number of switching mechanism units is arranged. For the common use of a relatively larger number of subscribers lines, switching means are provided to switch a calling line into connection with one of the said switching mecha nisms and to isolate the said line and switching mechanisi'ns from intrusion by other switching mechanisms, or other lines until the end of the conversational period when the said switching; mechanisms may be released from the control of the said calling lino, whereupon it will revert tocommon use and may be seized by another line.

In the systems of the art with which I am aware, it has been the general practice to follow one of several courses in construct ing these systems andv swit'cjhing mechanisms, one course being to make the switches relatively large so as to provide an incoming line with possible connections to a large number of outgoing lines, Another method consists in making the system up of a series of switching mechanisms, each being of relatively smaller size and arranging 'thesc switching n'iechanisnisso that a first one, commonly called a first selector, may be operated under a calling substation control to seize asecond, and so on until 2, 8, 4:, or more switching mechanisms are serially connected to extend a talking circuit between a calling and a called line, it being common practice to arrany e these switching mechanisms according to the decimal system for convenience in assigning subscribers line numbers, etc.

lVhile my invention has many objects and secures many advantages, some of which may be employed separately of the others,

it is-a main object of my invention to provide a system in which relatively simple switches having movement in one direction only, may be used and in which switches a large number of lines may be reached without the necessity of causing the switch to make an excessive number of steps.

Another object of my invention is to provide a system in which the stepping of the switches is always in the-same direction, whereby the release mechanisms for the switches are eliminated together with the consequent trouble such release mechanisms introduce, such as getting out of adjustment, wear on the releasing pawls, excessive wear on the switch bank contacts due to the relatively high speed of the wipers when releasing, etc. 1

Other objects of my invention and the invention itself will be apparent from a dc scription of two embodiments ofthe same which I have illustrated in the accompanying drawings in which Fig. 1,- shows one embodiment wherein the switching system of my invention is illus trated in connection with what I term a grounded; dial impulse system, and in which the switching mechanisms are re turned to normal under the control of a novel switch restoring controlling means, and in which system other features of construction and operation as will later appear in the description of the same, are contained.

Figs. 2, 3 and lwhen placed together to make one drawing illustrate a second embodiment ofmy invention wherein the impulse system is controlled over the two sides of acalling line in series, and in which the rise of the switching mechanisms is ac co. iplished under the control of a pair of interrupters. common to a plurality of such switching mechanisms in which other novel features as will hereinafter be particularly set forth in detail, are disclosed.

Referring to Fig. 1, at A Ishow a calling substation and at B acalled substation, line conductors for the calling and called stations being illustrated connecting the same to a main station at C. At L, 1 illustrate a line switch for the calling line which'under the control of the calling si'ibsta-tion A is adapted to interconnect circuit conductors of the calling line to circuit conductors of a link circuit LK.

It will be understood that other lines and other link circuits will be provided for the system, but for simplicity the same have been omitted it being well understood in the art as at this time developed, how such other lines and link circuits would be arranged in connection with the lines and link circuit specifically illustrated.

In connection with the link circuit LK, I illustrate three switches, each having six contact levels and six wipers simultaneously traversing the contacts of their respective levels. The wipers lV-1, 2, 1V 8, lV l, lV and VV-6 and the contact banks associated therewith comprise a master controlling or steering switch. Other switches, two of which are illustrated but more of which may be provided in a manner whichwill be made clear in the description, are shown comprising wipers W7'I to WV12 inclusive, designated, a combined register and connector switch, and 43 to 18 inclusive, it being understood that the wipers of each switch are adapted all to traverse their respective bank contacts simultaneously and it is furthermore understood that all of the wipers illustrated in the system of Fig. 1 are preferably of the type known as non-bridging wipers, that is. they preferalily do not make contact with more than one set of contacts at a time.

Stepping magnets for the master control-' .ling switch and the auxiliary connecting switches are shown at SMiif, SMA and SMB respectively. A plurality of relays for controlling the'operation of these switches by their control upon the stepping magnets are illustrated and will be more specifically referred to in the description of the operation of the system which followsz- The subscriber at substation A, upon removing the receiver to initiate a call, completes an energizing circuit for the line relay LR of the individual rotary line switch L over the: following path :-ground G, winding of line relay LR, terminal 1 and wiper 2 of line switch L, contact 3 of cut off relay CO, line conductor 20, impulse contact 22 of substation A, transmitter 2?, switch hook contact Ql, induction coil 2', line conductor 21, 'contact 4- ot relay CO, wiper 16 and terminal of line switch L and re sistance coil 18 to the source of current. The

line relay Llt energizes and by closing coir tacts T and 8 places a shunt around con tacts 3 and 4 of relay CO and wipers 2 and 16 of the line switch so that the circuit of the line relay L will notbe opened when the cut off relay CO energizes and the wipers leave the home terminals. The line relay L also closes the following circuit: ground G, contact 5 of relay LR, terminal 26, wiper 1-l and winding .12 of relay CO to the source of current. This ground is also extended to wire 27 which leads to the incoming test terminal of this line, thereby imniediately making this line busy to incoming calls.

Relay CO now energizes and closes a circuit from ground G, contact 6 of line relay LR, terminal 28, wiper 15, contact 10 of relay CO, contact- 17 of line switch stepping magnet ST, and winding of magnet ST to the source of current. This causes the magnet ST to energize, break its own circuit at contact 17 and retract its armature which moves the wipers 2, 1 t, and 16 from the first to the second row of terminals, which second row represents-a trunk which will be assumed to be busy and therefore there will be a ground on terminal 29. This ground will lind a path over wiper 15, contact 11 of relay SO, and winding 13 of relay CO to the ent which will hold relay .1 its energized position, while ano path may be traced through Contact 7 I o relay CO, contact 17 of magnet ST e winding of ST to the sourceof current. lwiagnct ST will again operate and advance the wipers to the third row of tern als where the same circuit as traced for Wing the wipers away from the first row of terminals will now be established to move them to the fourth row. It is to be understood that the first third, etc. rows are home or normal points and the second, fourth, etc., rows are trunk points.

There being no guarding potential on terminals or 31 of the fourth row, this being an idle trunk, magnet ST will not be again. energized and relay CO will "deenergize. It will be seen that there is a path for winding 12 of relay GO to the ground G but this path includes two relay windings and relay CO can be adjusted so as not to hold up through this resistance. Even if relay CO should hold up it would be for only an instant because, as will be later described. relay llY will operate and cause magnet SMM to step the wiper lV--2 away from the first terminal which opens this circuit to relay GO. Relay CO, upon denergizing, immediately places a guarding potential on this trunk by closing a circuit from ground G contact 9 of relay CO and wiper 15 to terminal 30. Relay CO also, by closing contacts 3 and 4, connects the line conductors 20 and 21 to the trunk conductors and 33, and now the closed circuit of substation A on the line establishes the following circuit: ground G resistance coil 3st, contact 35 of guarding relay GD, contact 36 of impulse relay IMP, winding of relay IMP, winding 37 of differential change-over relay DC, trunk conductor 32, previously traced closed circuit of substation A, trunk conductor 33, winding 38 of relay DC, cont-act 39 of relay GD, and winding 1-0 of release relay R to the source of current. Relays IMP and It energize but DO does not because it is differentially wound. At the same time that the above circuit was closed another one was closed as followsz-ground G contact 43 of auxiliary relay AX, winding 44 of stop relay SP. wiper lV-12- and first terminal thereof, winding 45 of busy relay BY, wiper lV1l and first position thereof, cont-act 46 of brush selecting relay BS, wiper VV2 and first position thereof, trunk conductor 47, line switch wiper 14 and terminal 31 thereof and the winding 12 of cut oil relay CO to the source of current. Winding-44 of relay SP is low resistance and will not operate over this circuit but relay BY does energize and closes the following circuit:-ground G winding of master stepping magnet SMll I and contact 48 thereof, contact 49 of reset relay RS, contact 50 of relay BY, contact 51 of trip relay TP and low resistance coil 52 to the source of current. The magnet SMM will now operate and advance the wipers lV-1, V\ 2, lV-3, -4, lV5 and W6 from the first to the second set of. terminals. lViper -2 has now opened the circuit of relay BY which deenergizes and off normal contact 53 is opened and 54 closed which energizes relay RS over the tollowing circuit :ground G, Winding 55 oi relay RS. contact 54 oi. oft normal springs UV and resistance coil 57 tothe source of current. Relay RS looks over the following circuit: ground G contact 58 of relay RS, winding 56 ot relay RS and resistance coil 57 to the source of current.

The foregoing operations have all occurred in response to the removal of the receiver from the hook. The subscriber at substation A may now operate the dial in accordance with the first digit of the number of the required station. When the dial is pulled torward the contact 23 at the substation is closed and remains closed until the dial returns to-normal and the contact 22 is opened and closed a number of tunes oorre spending to the digit selected. Contact 23 places a ground G on both of the line conductors 20 and 21, this ground on conductor 20 short eircuiting relay LR at line switch L, causing it to deenergize and at the same time short cireuiting winding 37 of relay DC causing it to become unbalanced and to energize. Relay IMP, being in series with winding 37 of relay DC, is also short circuited and deenergized but because relay DC operates, the following circuit is now closed to again operate relay IMP : ground G contacts 22 and 23 at substation A, line conductor 20, contact 3 o'f'line switch cut oil relay CO, wiper 2, trunk conductor 32, winding 37 of relay DC. winding of relay IMP, contact 59 of relay DC, and resistance coil 60 to the source of c1. rent. Relays DC and IMP now'being energized and their contacts 61 and 36 respectively being open,

a short circuit is removed from the winding 42 of relay GD which energizes from ground G resistance coil 34, winding 42 ot' relay GD, contact 59 of relay DC and resistance coil 60 to the source of current. Relay GD, energizing removes the short circuit from its winding 41 by opening contact 39, so that this relay will remain in its operated position while the circuit including winding 42 is being interrupted by impulse contact 22 at substation A. The circuit for holding relay GD is as follows :ground G contact 28 of substation A, transmitter 2?, switch hook contact 24, induction coil 2', line conductor 21, contact 4 of line switch relay CO, wiper 16, trunk conductor 33, winding 38 of relay DC, winding 41 of relay GD, and winding 40 of relay R to the source of current. It will be seen that relay DC, upon energizing, closed a circuit from ground G, windings 64 and 68 of relay BS in series, contact 62 of relay DC and resistance coil 52 to the source of current, but as the two.

windings of relay BS are wound dil'l'crentially it will not energize.

The foregoing has all happened as a result of the dial at substation A being turned forward and now as it runs baclcthe continuity of the loop is interrupted a number of times at impulse contact 22. As a result of these interruptions the line conductor 20, which is connected through relay IMP to'the source of current, is opened, thereby causing relay IMP to be deenergized a number of times corresponding to the digit pulled on the dial. The ground G is not interrupted and therefore relays DC, GD and It will remain energized while these impulses are coming in. At each deenergization of relay IMP an impulse is delivered to magnet SMAiWer the following circuit ground G winding of magnet SMA, wiper -45 and second position thereof,- contact 65 of relay GD, coin tact 36 of relay IMP, contact 59 of relay DC and resistance coil 60 to the source otran rent. Magnet SMA will operate at each impulse and step its wipers lV-T, lV-t lV-9, 40, lV-11 and lV12 to a point on their bank corresponding to the first d'git of the number desired.

Assuming that number 1 was turned on the dial, the magnet 'SMA will advance its wipers from the first to the second set of terminals and then the ground G 'at substation A will be disconnected from the line conductors just before the dial reaches normal. Relay DC will now again-becon' e dil terential and release but relays IMP, GD and It will be held operated over the line. Relay DC, upon deener'giz'ng, closes the fol lowing circuit :-ground G winding and contact 48 of magnet SMM, contact 66 of relay R, wiperlV-10 and second terminal thereof, 'contact'67 of relay AX, contact (38 o l relay SP, contact 69- of relay DC and resistance coil 52 to the source of current.

and VV-G to the row of terminals corresponding to the number which was recorder on the second switch, as previously described, and as this number was 1 and this second switch .was left on the second row of terminals, the first switch will be stopped at the first point of the first group which is the third set of terminals. The circuit forstopping this first switch is as follows :ground G contact 42-3 of relay AX, low winding at of relay SP, wiper iv-12 and second terminal thereof, wiper "W 5 and third terminal thereof, wiper lV- and second terminal thereof, contact 67 of relay AX, contact (58' of relay SP, contact 69 of relay DC and the resistance coil 52 to the source of current. This circuit to ground G does two things, "first it shunts the mag net SMM so that it will not aga n energize to move the wipers of the first switch and second it will energize relay SP and lock it over thefollowing circuit:ground G, magnet SMM and contact 48 thereof, contact 66 of relay R, wiper W 10, andsecend terminal thereof, contact 67 of relay AX, winding 70 of relay Si contact 69 of relay DC and r sistancc coil to the source of current. i

A circuit is now closed from ground G 'wlnding and contact 71 of magnet SMA, contact 72 of relay SF, on normal contact 5 1 and resistance coil 57 to th source of current, which circuit causes the second switch to advance to the eighth set of terminals when wiper \V10 will open winding 70 of relay SP, it will deenergize and the second switch will remain on the eighth set. of terminals. A circu't is now closed from ground G Contact elf-l of relay AX, low winding 4% of relay SP, wiper lV i2 and eighth tern'iinal thereof and winding 7?) of relay AX to the source of current. The winding 44 of relay SP, being of "very low resistance, this relay will not be affected but the winding 73 of relay AX, which is of high resistance, will energize relay A X. and lock it frol'i'i'grouml G, make before break contact 75, winding 74;, off normal contact 5% and resistance coil 57 to the source of current. 'telay AX, upon energizing, opens contact 67 which clears wiper li -10 so that it may be used for another purpose later, and it closes contact 76, the purpose of which will .be described later. The subscriber at substation A may now operate the dial for the second digit but before the results of this operation are described some things will be pointed out in connection with the oper ation of the dial for the first digit.

In'the foregoing description it has been shown that if number 1 is the first digit,

the second switch will step to the second'set 'of terminals, establish a circuit by means of its wiper il --12 to cause the first switch to stop on the third set of terminals after which the second switch will he stepped to the eighth set of terminals. It will presently be shown that as the dial is again pulled forward, relay BS will operate and connect in wipers l V-7 VV8 and lV9 which are the line and test wipers for the lines beginning with digit 1. Now if number 2 was the firstdigit, the second switch would step to the third set of terminals, the first switch would advance to the fourth set of terminals and the second switch would he stepped to the eighth set as before, but this time when the dial was pulled forward for the second digit, relay BS would remain normal which time, relay BS will operate and connect in wipers W 18, V-1 l and \V15 which are the line and test wipers for the lines beginning with digit 3. lVhen the second digit is sent in from the dial in this case, the third switch will be operated because wiper \V'6 is on the eleventh terminal which terminal is connected to the stepping magnet SMB of the third switch. Similarly, if at was the tirst'digit the wipers lV-16, :lV-17 and lV18 of the third switch. would be used.

By adding other switches connected to wires 77, 78, 79, 80, S1, 82, and 81 iaud connecting in the off normal contacts like ON and (3N other groups of lines may be served. It will also be noted that corresponding wipers of each switch second, third, etc, are connected together, but that only one of these switches will be away from normal, or the first set of terminals, at one time. therefore only one set of wipers will 'be effective. The numbers of the lines reached on these switches are represented by L-11, L-2l, etc.

Returning now to the point where the subscriber.operates the dial for the second digit, relay .DC operates, as before and, by means of its contact 59, prepares the impulse circuit for relay IMP. It will be remembered that the first switch was on its third set of terminals and now relay DC. energizing, closes the following circuit :-ground Giwinding of magnet SMM, and contact 48 thereof, contact 66 of relay R, contact 76'of relay AX, wiper 4 and third'terminal thereof, winding'63 v of relay BS, contact-62 llO of relay DC and resistance coil 52 to the source of current. This circuit will ener' gize relay BS over its winding 63, its winding 64 being sufficiently shunted by magnet SMM to unbalance it. If, however, the first switch was on the fourth set of terminals, because the first digit was 2, the wire 85 connected between the two windings of relay BS would have been open and any current received by one winding would also be received by the other and the relay would not be energized because its windings 63 and (5t are equal and opposite.

Reiay BS will lock, when energized, over the following circuit :ground G", winding 86 of relay BS, contacts 87 and 88 of relay 13 ( contacts 87 and 88 to make before break contact 89 breaks), contact 54: of off normal ON and resistance coil 57 to the source of current. Belay BS, upon energizing, closes the follow-in circuit: ground G winding of magnet SMli i and contact 48 thereof, contact '66 of relay R, contact 76 of relay AX, wiper iV--; and third terminal thereof, contact 88 of relay BS, contact 5% of off normal ON and resistance coil 57 to the source of current. This causes the first switch to operate and advance its wipers lV1, -2, W-3, ti e, W-5 and lV-6 to the fourth set of terminals from which point they are again advanced by means of the following circuit: ground G5, winding of magnet SMM and contact 4.8 thereof, contact 66 of relay R,

contact 76 of relay AX, wiper -4 and fourth terminal thereof, contact 62 of relay DC and winding of resistance coil 52 to the sourceof current. If the first switch was on the fourth set of terminals when relay DC op ated, this last traced circuit would of c -'irse move it to the fifth set but relay BS would not have been operated. It will be seen that the terminals of A -4 are divided into three groups with the corresponding points multipled, therefore the same operations will take place when the third or fourth switches are used instead of the first.

iitgain returning to the point where the subscriigier o1 crates the dial for the second digit, (assuming the numb-er dialed to be the impulse relay IMP will deliver five impulses to the stepping magnet for the sec- 'ond switch over the following circuit the first swit h atlranced to the fifth set energizes relay TP, but because of the re sistance of TP, magnet SMM will not be energized. Relay TP closes the followingcircuit to energize relay BY :ground G winding of magnet SM and contact 48 thereof, contact 66 of relay 1%, contact 76 of relay AX, wiper K -at and fifth terminal thereof, winding 93 of relay BY, contact 94 of relay TP and resistance coil 52 to the source of current. Magnet SMM does not get sufficient current to operate in this case. DC deenergizes as'before, a circuit is closed from ground G winding of magnet SMM and contact 48 thereof, contact 66 of relay R, contact 76 of relay AX, wiper W-Jr and fifth terminal thereof, contact 69 of relay DC and resistance coil 52 to the source of-current, which circuit causes the first switch to advance its wipers to the sixth set of terminals. This opens the circuit of relay TP at wiper -5, TP will deene rgize and, after a short interval, retract its armature, but before its armature restores, the called line is tested for its busy or idle condition as follows :-if the line is busy there will either be a ground or anopen circuit on the test terminal on which wiper W9 is resting. (the former if the line had been called and the latter if the line had originated a call, its test wire 27 being; open at line switch wiper 14c) and if the line is idle a path to the source of current will be found on the test wire. Therefore if the line is busy when relay TP deeneraizes there will be no circuit to hold relay BY, it w ll deenergize and give the calling party the busy signal over the following" circuit ground G common battery, secondary induction coil 95 into which a tone is induced, condenser 96, busy interrupter 97. common busy wire 98. winding; 99 of relay R, contact DC, winding 4.1 of relay GD and Winding Now when the dial stops and relay 4.0 of relay R to the source of current.

followt: b and Slfiilli terminal the called line is idle when the steps its wipers to the sixth set .1 t, a 1 v relay BY will remain energized over the a circui round G wiper l .*2 thereotl windni'." of

relay ,Y, contact 102 olrclay l7; con

a, 103 of relay BS, wiper il -4), test of called line and called line cut (rcpresented by the ninncral St?) to tu,

source 01'? current. Now when relay 'lP deenergizcs a circuit is closed troiu ground wind ng" of magnet r thereof, Contact o1 of relay AX, wiper lV-t and sixth terminal thereof, contact fit) of rel of relay T1 2 source of cuiTciuQv cut Shir r wipe a switch to the seventh. set i ternr the following circuit is losed from I a wiper rd sorei contact -i i' called line conductor 104k switch hook Contact 10601 substation ll, condei-ser ringer conductor 105, wiper Y --53, contact 108 and relay BS wiper i -f2 and seventh terminal thereof and resistance coil 3-1 to around The eli'ect of the resistance coil ill will be to force a small amount of the. rir 'iug current back through the circuit to suliistation A, thus a" cine the calling part an, indication that c led hell is he; i When the called 1 tv removes the rec .iier a direct current 1 1th closed for the above traced line is led through relays R, GD IMP.

circuit which causes relay T1 to operate and, b means of its contact 91-, close a circuit troni ground G. wn ling: a magnet til-EM and contact 48 thereof. contact 66 of relay Contact 76 oi relay AX, wiper W'al and s. CQDtll tei,"-.- iinal thereof. contact Set of relay T1 and resistance coil to the source oilcnrrent. This operates magnet SMlii and moves the wipers of the P nrst switch to the eighth or talitmg position. The talking: batte y ted to the called party over the above traced 111351111 circuit except that'the battery teed coil Br is substituted for the ringing); circuit bymeans of wipers Wl and 1V being on the eighth et of terminals; talking battery for the ca DC and thetwo are connected together. for voice currents by means of condensers 109 and 110.

The calling party releases the connection by hanging up the receiver which opens the line and allows relays R, G1) and IMP to dcenergize. Relay R closes the following circuit to energize the cut off relay C0 of the line switch L:ground G contact 111 out relay RS, contact 112 of relay R, trunk wire lT, terminal 31 and wi or 14: of line switch L, an; yin-ding .2 0t relay CO to "re source of current. The magnet ST of :re line switch is now operated to advance s wipers to the home point from ground contact 113 of relay RS, terminal and ripcr 15 of line switch L, contactlO of re- .a CO, Contact 1'? of magnet ST and the r 'inding of magnet ST to the source of ourt It will be noted that this ground G will also 'keep'this truni-t busy until relay 9 ceenergizes. Another circuit may now re traced froin'ground G winding of mag- Slilldi andcontact d8 thereof, Contact tacts and 54; being switched at each.) A circuit is now closed from ground G windmg OfZDflQ'llQt SMA and contact 71 thereof,

contact 116 of otli' normal ON, contact 53 of oil normal ON and resistance coil 57 to the source of current, which will cause the second switch to advance its wipers to the ialv point. if the third orv fourth sii'nichcs had been need it can be seen that a corresporuliug operation would take place" by meansv of oiii' norn'ial ON for thethird s :itch or 0H for the TIGOHI' QlL' lVitlrall switches at normal the following circuit is closed :ground G contact 58 of relay RS, contact 119 of of? normal 0N contact 118 of off normal ON contact 117 of oil" nor-11ml ON, contact ot oli' normal ON and the resistance coil 5'? to the source of current i 1 ulnch short circuits winding of relay RS causing itto release. Relays A'X and BS are released when contact 5% 0t ofi normal ON is opened, all circuits now being in their normal condition ready for use again. l'letcrring now to the system of Figs. 2, 3 Piit 4. at 1*; I show a calling; substation nstrumen extending interconnecting.

line conductors to a; main station where there is located 2. line switch forthe; line LS,

rrlay contact 115 eta-slay RS,

ted to interconnect conductors of theline circuit of the calling line having the substation N, to an idle one of a plurality of link circuits of which the link circuit conductors LKC are associated with one of the said link circuits, other link circuits being provided which are accessible to the traveling wipers of the line switch LS, but which are not specifically illustrated. The circuit conductors LKC of the selected link circuit are shown extended in Fig. 3, where they terminate in circuits and. apparatus of relays which control the various operations of a plurality of traveling switch mechanisms illustrated in Fig. 1, the relay controlling means for various switch mechanisms of Fig. at being illustrated in Fig. 3. A plurality of circuit conductors are shown extending from the relay controlling means of Fig. 3 to the continuation of these circuit conductors leading into the switch mechanisms of Fig. 4. A called line substation is illustrated at O in Fig. 1, and the line conductors leading therefrom to connector switch bank contacts of one of the switch mechanisms of Fig. 4 being correspondingly illustrated.

Referrin particularly to Fig. 4c, a plurality of switches each having one direction of movement is illustrated, the first master controlling switch having wipers lV2l, W-22, F423 and ll 2 l respectively. A pair of auxiliary switches operating under the control of the master controlling switch is illus rated having wipers VV', 7 26, -27, lV-23, VV29, il and 431, lV32, lV33, VV3, F435 and EV-36 re spectively. Each of the three switches is of the type having a plurality of wipers adapted to be simultaneously moved to simultaneously traverse their associated contacts under the propelling actuation of a single stepping magnet, the same stepping magnet being used to restore the switch to normal by stepping the switch in the same direction in the stepping which accompanies the selective function. The stepping magnet for the master controlling switch is illustrated as SliliS, and for the auxiliary switches SAS and S138.

It will be understood that in order to increase the number of lines which maybe reached by the switching mechanisms of Fig. 1, it would be only necessary to add the required number of auxiliary switches in addition to the pair of auxiliary switches illustrated.

In order to convey' a better understanding of the system of my invention and the invention itself, a description will now be had of the operation of the same.

Upon the removal of the receiver 1* at substation N, Fig. 2, preparatory to making a call, an energizing circuit is closed for the line relay LLB of line switch LS as follows:-ground G terminal 150, wiper 151, contact 152 of cut off relay COR, line conductor 153, induction coil id, switch hook contact 154-, transmitter tr, impulse contact 155, contact 156 of relay ch, line conductor 157, contact 158 of relayCOl-Z, wiper 159, terminal 160 and'winding of relay LLB to the source of current. The line relay LLR when energizing, closes a circuit to cause the line switch wipers 151, 159, 161, 162 and 163 to be advanced from the home point to the next adjacent row of terminals, which.

is a trunk point, said circuit being as follows: ground G contact 16 1 of relay LLB, terminal'166, wiper 161 and winding 167 of relay COR to the source of current which energizes relay COR'and then ground G extends through contact 172 of relayLLll, terminal 173, wiper 162, contact 170 of re lay COR, contact 169 of line switch stepping magnet SST and the winding of magnet SST to the source ofcurrent,causing the switch to advance its wipers to the second row of terminals. If this trunk is busy there will be a ground on terminal 17 1- which will keep relay C ll energized and. will cause the magnet SST to again operate, bringing the wipers to the third row of terminals which is another home point, from which the wipers will be stepped as from the other home point on to the fourth row which represents the idle trunk shown on Fig. 3 and Fig. 4:. l'V hen relays LLB and COR operated they closed a holding circuit for the line relay LLR by means oftheir contacts 165, 175 and 176 so that the line relay LLR would not deenergine when the wipers 151 and 159 opencdthe original circuit. When the idle trunk is reachet there will be no ground potential on terminals 177 and 178, therefore the wipers will come to rest and relays COR and LLB will deenergize. This line was innnediately made busy to incoming calls by. the line relay LLR closing contact 16% and as long as wiper 163 is standing on a trunk point,

ground G wiper 163, terminal 18?, 1'36,

etc, will be on the incoming test wire 187. Relay LLB upon deenergizing, opens the battery bridge ofthe line switch at contacts 165 and 175, and relay OCR, upon deenergizing, extends the line conductors 153 and 157 to trimk'conductors 1841 and 183 respectively. Relay COB. also closes the following circuit to make this seized trunk busy:- ground G wiper 168, terminal 186, con-- tact 171 of relay COR, wiper 162, terminal 177 and trunk conductor 181. It is of course understood that trunk wires LKC are multiconductors 18s and 183 may be traced on Fig. 3 to ground G5 at sensitiverelav SN and the sourceof current at marginal relay MG causing them both energize. It will here be mentioned that relays SN and MG feed talking battery to the calling party over the above traced circuit and that condensers 1.90 and 191 are used for the voice current path between the calling and called parties. 1 circuit is also closed from ground G wiper 163, terminal 186, contact 171 of relay COR, wiper 162, terminal 177, trunk conductor 18 1, contact 192 of secondary release relay SR, wire 193, wiper 1V21 and first terminal thereof, contact 203 of the stepping magnet SMS of the first switch and the winding of said magnet to the source of current. This circuit causes mag-net SMS to operate and advance the wipers W 21, 1V 22, 1V23 and 1V-2l of the first switch to the second set of terminals.

Relay MG. being energized, now closes a circuit to move the wipers of the first switch to the third set of terminals as follows ground G contact 209 of relay MG, wire 20st, wiper lV-21 and second position there of, contact 203 and winding of magnet SMS to the source of current.

lhe calling subscriber now operates the calling device, whereby the substation im pulse springs 155 are interrupted a number of times corresponding to the first digit of the called number. Assuming this number to be 1, these springs 155 will send one impulse which will, on the opening, deenergize relays SN and MG, whereupon HG will close the following circuit :ground G contact 210 of relay MG. wire 205, wiper -21 and third terminal thereof, contact 203 and winding of magnet SMS to thesource of current, which advances the wipers of the first switch to the fourth set of terminals. Just after this opening of contact 155, contact 188 closes which inserts relay ch 11111116 conductor 157, this relay will immediately energize and by opening its contact lhfi, will open the c-ircuitto the impulse contact 155. sistance relay (2000 ohms for instance) in the line, marginal relay MG will not energize but sensitive relay SN will energize and cause the first switch to advance its wipers to the sixth set of terminals over the following circuit :-ground G contact 21].. of olfnormal ON, (off normal contacts ON and ON are associated with thefirst switch and are closed when the wipers are on any but the first set of terminals) contact 213 of relay SN, wiper N21 and its fourth and fifth terminals in turn. contact 203 and winding of magnet SMS to the source of Gli- With this high re-.

and locks over the following circuit:- ground G contact 211 of off normal ON, contact 216 of relay CHO, winding 217 of relay CH0, and resistance coil 218 to the source of current. A circuit is also closed from ground G contact 211 of off normal ON, low resistance coil 221, contact 222 of cut-in. relay Cl, contact 220 of relay CHO, wire 20?, wiper lV21 and sixth terminal thereof, contact 203 and winding of magnet Shin to the source of current.which circuit *auses the first switch to advance its wipers to the seventh set of terminals. Relay CHO closes another circuit from ground G contact of stop relay STP, wire 202, contact 227 and winding of magnet SAS, wire 201, contact 228 of busy test relay BT, contactof relay CHO, contact 224 of relay ST? and resistance coil 219 to the source of current, which circuit will cause the second switch to advance its wipers to the first set of terminals, assuming that the second switch was left on the second normal pointon the previous call, (second and third switches 11' re a first normal point, first set of terminals. and a second normal point, thirteenth set ofterminals) when the following circuit is closed :-ground G contact 230 of auxiliary relay A X, low winding 231 of relay STP. contact 232 of relay CI, wire 233, wiper il -2e and seventh terli'illltll thereof, wiper 1V3O and first terminal thereof to a point between magnet SAS and the resistance coil 219 to the source of current. This effectively shunts out the magnet SAS, causing it to come to rest and at the same time energizing relay STP. It

,will be noted that if the second switch was resting on the first set of terminals (first normal point) when relay CHO operated, the above traced shunt circuit would have been immediately established which would have caused relay STP to operate as before but magnet SEAS would not he stepped. lie-- lay ST? will loclr over the following circuit:ground G contact 257 of relay AX, contact 255 of relay CHO, contact 258 and winding of relay STP to the source of current. Before proceeding with the operation after relay STP energizes, it will now be pointed out what happens when other numbers such as 2, 3 or 4 are turned on the dia for the first digi Assuming the calling subscriber to operate the dial for number 2, the impulse springs 155 at substation M will be opened and closed twice, the first opening, as before described, will cause the first switch to advance its wipers to the fourth set of terminals. Impulse springs 155 are now closed causing relays 5N and MG to energize and will again cause the first switch toadvance'its wipers to the sixth set/of terminals. Relay MG'inthisj case being energized, winding 215 or relay CHO is shunted by ground G contact 211 of off normal ON, low resistance coil 221, contact 222 of relay CI, contact 246 of relay MG to the winding 215 of relay CHO, so that CHO will not energize. This circuit from ground G is also traced from contact 246 of relay MG, wire 207, wiper -21 and sixth terminal thereof, contact 203 and winding of magnet SMS to the source of current, which circuit causes the first switch to advance its wipers to the seventh set of tern'iinals. A circuit is now closed from ground G contact 209 of relay MG, wire 204, wiper lV2l and seventh terminal thereof,'contact 203 and winding of magnet SMS to the source of current, which circuit causes the wipers of the first switch to be advanced to the eighth'set of terminals. Now when impulse contact 155 is opened for the second impulse,'relays SN and MG will deenergize, and relay MG, by means of contact 210 will step the first switch to the ninth set of terminals. Relay oh at substation N will now. be energized as before, prevent relay MG from energizing but allowing relay SN to operate and, by means of the previously traced circuit through its contact 213, this time cause the first switch to step to the eleventh set of terminals. A circuit is now closed, as before, for energizing the lockingrelay QHO which relay now causes the first switch to take another step and go to the twelfth set of terminals where the circuit is again closed to cause the second switch to advance to the second nor mal point (the thirteenth set of terminals) stop the third switch on its first set of terminals. If 4 was the first digit the first switch would have stepped to the twentysecond set of terminals and the stopping circuit would have been byway of wiper lV-2l, as before, this time through wire 24%) to stop the. third switch on its tl'iirteenth set of terminals which is the second normal point. The starting circuit for the magnet SAS of the second switch is by way of contact 228 of relay BTas before traced but if either 8 or 4. is the first digit, relay Bl will be operated and switch the starting circuit to contact 250 which leads by way of wire 200 to the magnet SBS of the third switch. Relay ET is energized as wiper w ee passes the. fourteenth and fifteenth termina e the foll g eircuit;-

ground G contact 230 of relay AX, low winding 231 of relay STP, (not affecting the armature of relay STP) contact 232 of relay CI, wire 233, wiper VV24C and fourteenth and fifteenth terminals thereof, Wire 24%, winding of relay BT and resistance coil 251 to the source of current. Relay BT locks from ground G contact 211' of off normal ON, contact 252 of relay BT, winding of relay BT and resistance coil 251 to the source of current.

Returning now to the point where relay STP was energized after number 1 was turned on the dial at substation N, it will be remembered that the first switch was left on the seventh set of terminals and the second switch on the first set. Relay CHO, being energizechcloses the following circuit :ground G wiper 'VV22 and seventh terminal thereof, wire 236, contact 25a of relay CH0 and winding of relay MG to the scurse of current, this ground also go- .ing back on truck conductor 183, through the line switch LS, line conductor 157 which short circuits relay ch at the substation N. Relay ch deenergizes, short circuits itself,

relay MG energizes and oloses'a circuit from ground G flco-ntaot 209 of relay MG, wire 204e, wiper fi -21 and seventh termi-' nal thereof, contact 203 and winding of mag net SMS' to the source ofcurre'nt, which circuit causes the wipers of the first switch to be advanced to the eighth set of termi nals. Relay STP, upon energizing, closes the following circuit to cause the second switch to advance its wipers to the second setof terminals: ground G contact 230 of relay AX, low winding 231 of relay STP, contact 232 of relay CI, wire 233, wiper lV--24 and'sixth, seventh or eighth terminal thereof, wiper 30 and first terminal thereof,- winding of magnet SAS and contact 227 thereof, wire 202, contact 225 of relay STP and resistance coil 219 to the source of current. It will be seen that if the first digit was 2 this-above traced circuit would be by way of wire 24:7, causing the second switch to bestepped to its fourteenth set of terminals, and similar circuits maybe traced for the third" switch when the first digit is :9 O1, :4 V ,7

When the first switch is advanced to th eighth set of terminals, as above described, a circuit is closed from ground G ,'wiper \V-22 and eighth terminal tl'iereof, wire 238, contact 226 of relay STP, contact 256 of relay AX, andresista-nee coil 218 to the source of current, which groundshort circuits winding 217 of relay CHO, causmg it to deenergize. Contact 255 of relay CHO now ovens and disconnects the ori inal locking circuit of relay STP but relay STP will remain energized and relay AX= will now'energizeoverthe following circuit: ground G coptactflll of ONfQwindin-g giff relay.AX contact 258 and wind-ing%259 or relayysTPr-to the source of current, which. circuit also holdsrelay STPQ The-subscriber at substation N may now operate the dial for the second digit when relays-SN -and MiG-will; functionthe same as before: *Relay -MG, upon. deenergizing, closes acircuit from; ground GFfl-contact 210 of relayiMG- wiper W-2l and eighth terminal thereof, contact 203 and- Winding of magnetSMS 'to the. source of current, which circuit eausesthewipers. of the first switch" I to be advanced .to'the ninth set of terminals. A circuit is ;1 1ow-;closedfrom *ground G Wiper W' 22- and :ninthterminal thereof,

Wiper 3V-30 and second terminal thereof, (thistermina l is multiplied to the other termmal of this secondw switch which follows-nthesecond-normal point, and *to corresponding termin-als'of the third switch,

and-isfort-he purpose of causing the proper switch :to be 'steppecl no .inatterwhich normal point it had-1been--set'on,) winding of magnet SAS and-contact 227 fthereof, wire 202, contact-2250f relay STP, and resistance coil 219-to the, source? of current, which'circuit causes unagnet'SAS to operate and ad- Vance-the wipers of thensecond switch to the third set. of .terminals;-' Relay SN,-now= I being energized, will cause the v first switch to advance -rts 'w1pers-pastthe nlnth and tenthsets of -terin'1njalsover the previouslytracedw'circuit; @Theswitch will be -steppedpast' -wthe eleventh set if relay; 'MG" is energized. Thus it will-the seen that the first witch follows the -iniipulses of the dial until" the 'change-oyerpoint is reached when relay hflG remains" deenergized- 'as before described- It will also he seelrtliat for each impulse, wipeifiVV23 of the first-switch travels over a multiple ;of wire 260 (thiskvireis multiplied to twoterminals and "a bridging ibrush: used so as to deliveralong "i'nu uilseto the magnet-SAS or SBSg') andin so doing closes a circuit from ground-G contact 211 of oil normal ON, :c0ntaift' 261 of relay *GHO ,-'wrre 239,

wiperdV-23 and terminal :tliereo f, wire 2G0,

multiple .tern-iinals' and wipe-r -\V-'3O, wind-= ing of magnet SAS, multiple terminals and" wiperi 29, "wire: 195,*'contacts 2G3, and" and resistance coil- 219 to the source of currents-' This circuitr ausesthe second switch to step *lt'S-Wl1w19' 111"ZICCOlKliUlCQ with: the

nui'nberof impulses-sentinfor the second (llgliigg';

It will be seen+that2-the wire 2t5O"-is con nected to gmultiple; terminals of wiper VV'36 andi -tl1at magnet wSB-S is fconneeted to mu] tipleite-rminal's o f wiper 2VV-35, and if the thirds switch, *insteadof the second, was

stepped: away hfrom its normal point, these i grounder-impulses =I-throngh-; wipe-r: -23 would he delivered to the magnet Whenthe lastdmpulse is sent in from the dial, relay CHO energizes as before and closes the following r circuit-i ,ground- G winding of secondchangeroyer relay CV,

contact 255- of relay CHO, contact 258 of relay STP and winding 259 of relay STP j to the source of current, which circuit ener-- glzes relay CV. No matter where the wipers of the first switch are resting when this happens (they may have made more than a completrevolutionor they may have made less than a complete revolution depending onthe 'numberfof impulses sent in r for the second digit,) they will now be advanced to the twenty-fourth set of terminals, the following circuits to ground being found on the different terminals of wiper '1V-21i 1ground G -from line switch LS 2, 7,12, 17 and 22ground G through contact 209 of relay MG, 3, 8, 13, 18 and be openat contact-2390f relay AX. Relay BT will however be operated from ground 29 as wiper V 22 passes the sixteenth terminal. 7

When the wipers of theiirst switch get to the twenty-fourth set of terminals :1. test is made-of the calleddine as followsz-li said line isbusythere will'be ground on the :tern'iinal on which wiperWV-QT (or \V 33) is resting, placed there either by :1. ternrinat 111g call, as willbe presently shown, or be cause; the calledlrnefhad originated a' call when this ground wouldhare been placed on the test'terniinal as previously described in connection with-wire 187 of Fig. 2. With wiper 1V -22on its twentyefourth terminal a circuit is closed from ground G wiper l -22 and tucnty-foui'fli terminalthereof,

wire 235, contact of relay CV, and re' sist-ance coil .251 to the source of current,

saidcircuitshort circui-t-ingrelay RT which 'relayK-beingslow acting,- after 'a short intervalwretrac s-jits armature. The calling part-y 'now'hears the busy-signal which is on coinmonwire 266 (placed on wire 26% in ':-the same or a similar i'nanneras described for the operation of Fig. 1), by way of condenser 267, Contact 232 of relay "Cl, wire 233, wiper. 2 1 and twenty-fourthlernnnal thereof,w1re.-2-ft0, condenser 191, trunk conductor '184, through the line switch LS and substation N, trunk conductor 183, winch ing of relay 'MG and throughthe battery to, the other side of the bus sfi;induction coil. Disconnection takes place when the calli g party hangs up as will be presently described.

Assuming the number dialed to be 41 and this number represented by the substation O, the circuit operation after the first switch reaches the twenty-fourth set of terminals will now be described. Relay BT will be short circuited as above described but before it releases, a circuit will be closed from ground G Contact 211 of OH normal ON, contact 213 of relay SN, contact 268 of relay CV, winding 269 and contact 270 of relay CI, wire 239, wiper lV-23 and twentyfourth terminal thereof, wire 2 11, contact 271 of relay BT, wire 197, wiper 7-33 (or \V-27 ii": the first switch was used) terminal and resistance coil 272 to the source of current. This circuit energizes relay Cl and, by means of contact 273 which makes before contact 270 breakes, it looks from ground G contact 211 or off normal ON, resistance coil 221, contact 273 and winding 27-1 of relay CI to the source of current. The first switch now advances its Wipers to the twenty-fifth set of terminals over the following circuit, before the armature of relay ET is retracted :ground G contact 211 of off normal ON, contact 253 of relay B'l, contact 275 of relay CI, wire 2 15, and winding of magnet SMS to the source of current, which circuit energizes magnet SMS and, when relay BT releases and opens contact 253, magnet S-MS deenergizes.

A circuit is now closed formaking the called line busy to other calls and for opcrating the cut off relay of the called .line switch (represented by coil 272) from ground G contact 211 of off normal ON, resistance coil 221, contact 276 of relay CI, wire 197, wiper W33 and terminal thereof and cut off relay 272 to the source of current.

The called partys bellis now rung over the following path: ground G battery, re sistance coil 279, generator GEN, interrupter IT, lamp LM, ringing trip relay TRY, wire 243, wiper -2 1 and twenty-fifth terminal thereof, wire 233, contact 277 of relay CI, wire 198. wiper lV32, called line conductor 280, ringer rg at substation O, condenser on, line conductor 281, wiper lV-31, wire 199, contact 278 of relay CI, wire 239, wiper il -=23 and twenty-fifth terminal thereof to ground ti hen the called party answers a direct current path is closed which energizes relay TRP, closing the following circuit: ground Or, contact 280 of relay TRP, to the winding of relay AX short circuiting AX which deenergizes. This ground G also goes through contact 2535 of relay CHO to the windingof relay CV, short circuiting it, causing it to deenergize and the short circuit is now maintained for relays AK and CV by ground i and conln l 257 of rel y AX, so that when relay TRIP deenergizes neither of these relays AX and CV, will again energize. Relay CV, upon deenergizing, closes a circuit from ground G contact 211 of oil normal ON, contact 213 of relay 2N, contact 281 of relay. CV, wire 208, wiper -21 and twenty-fifth terminal thereof, contact 203 and winding of magnet @MS to the source of current, which circuit causes the first switch to operate and advance its wipers to the twenty-sixth set of terminals. The talking battery is now fed to the called party from ground G winding 282 of battery feed coil BF, wire 2 10, wiper W 23 and twenty-sixth terminal thereof, wire 239, contact 278 of relay CI, wire 199, wiper W-31 and te-ii'ininal thereof, called line conductor 281, through the usual substation apparatus O, line conductor 280, wiper lV32 and terminal thereof, wire198, contact 277 of relay CI, wire 233, wiper lV-24l and twenty-sixth terminal thereof, wire 242, and winding 283 of coil BF to the source of current. The wires leading into coil BF are connected to condensers 190 and 191 which condensers are also connected to the calling line as previously described. The talking .circuit is now established between the calling and called parties.

The release of the connection will now be described. The calling party, hanging up the receiver, causes relays SN and MG to be deenergizeol' and the following circuit closed by relay SN: ground G contact- 211 of oil normal ON, contact 21% of relay SN, contact 212 of off normal ON, winding o't primary release relay PR, contact 28% of relay PH, common interrupter contact 296, and resistance coil 295 to the source of current, which circuit energizes relay PH andloclzs it with battery through resistance coil 286 and con tact 285. Relay PR could be energized over the above circuit during the time that relay SN was deenergized as the impulses were being sent, but-tho circuit would be'again opened, allowing relay PR to deenergize, when relay SN was energized. In this case however, relay SN will remain deenergized v fora sufficient time to allow the common interrupt-er contact 297 to extend ground by way of contact 287 of relay PR, contact 290 and winding 294, 01 secondary release relay SR to the source of current. Relay SR will energize and lock lroin ground. (i contact 211 or ofi' normal ON, contact; 291 and winding 29st to the source of current, this loci;- ing circuit holding relay SE in its ()Ptltllt-(l position until the first switch restores to normal when, by the opening of otl normal contact 211, the current will be disconnect cd from winding 294. A circuit is now closed from this oft normal ground G? and contact 292 of relay SR by way of wire196, wiper lV28 and all off normal terminals thereof, winding and Multan-11227 .ot m gnet SAS,

wire 202, contact'225 of relay STP, and rcsistance coil 219 'to the source of current,

normal point. It the third switch was the one used instead of the second, this ground would go through wiper \V28 and normal (first or thirteenth) terminal thereof, wiper \V34: and all off normal terminals thereof, Winding and contact 23 1 of magnet SBS, wire 202, contact 225 of relay STP, and resistance coil 219 to the source of current, which circuit would cause the wipers of the third switch to he stepped to their normal point. above traced path from ground by way of the normal terminal of wiper 1V3t, contact 203 and winding of magnet SMS to the source of current,-which circuit causes the Wipers of the first switch to be advanced to its first set of terminals when off normal contacts 211 and 212 open 'and break the stepping circuit for the first magnet and the locking circuit for all relays. Relay SR, by

opening contact 298, releases relay CI which deenergizes and keeps the line wipers -25 and 1V-26 or lV-31 andld -32 clear while they are stepped over terminals of lines which may be in use.

The line switch LS is released fron' ground G low winding293 of relay SR,-

contact 289 of relay SR, trunk conductor 182, line switch terminal 17 8, wiper 161 and -winding 167 of line switch cut oft relay COR to the source of current, thereby energizing relay COR which in turn closes a circuit from ground G low winding 293 of relay SR, contact 288 of relay-SR, trunk conductor 181, line switch terminal 177, wiper 162, contact 170 of relay COR, contact 169 and winding of magnet SST to the source of current. The line switch wipers are now given one step which takes them to a home point and, by opening the circuits of line switch terminals 177 and'17-8, relay SR is deenergized. The circuits are now in normal condition ready to again be used.

It will be understood that whereas I-have illustrated specific embodiments of my invention, that the same is capable of being embodied in systems varying widely "111 ,struc-' tural details from that specifically illus trated and described, but what I claim is my invention is defined in the following cl a nus 2- v 1. In an electromechanical telephone switching system, the combination with a main station trunk circuit, of a telephone line adapted to be connectedthereto, of a telephone substation for the said line, a sending device at the said substation, switching mechanism for the said trunk circuit under.

the control of the saidsending device, the

said switching mechanism comprising a plurality of switches, one of the said switches w A circuit is now closed over this 'being'a steering switchand another of the said switches being a combined register and connector switch, means to operate the substation sender to give the said combination switch a predetermined setting in accordancewith the first digit of the called line number, means responsive thereto, to cause the said steering switch to take a setting cor-' responding to the setting of the said combination switch, means operative after the said setting of the steering switch to cause the said combination switch to always take a second setting which is the same for every case being independent of the first position setting of the said combination switch, and means responsive to the second operation of the said substation dial to operate the said ing device at the said substation, switching mechanism for the said trunk circuit under, the control of the said sending device, the

said switching mechanism comprising a plurality of switches, one of the said switches being a steering switch and another of the said'switches being a combined register and connector switch, means to operate the sub station sender to give the said combination switch a predetermined setting in accordance with the first digit of the called line number, means responsive thereto, to cause the said steering switch .to take a setting corresponding to thesetting of the said combination switch, means operative after .the said setting of the steering switch to cause the said combination switch to always take a second setting which is-the same for every 7 case bei independent of the first position setting ot the said combination switch, a plurality of other connector switches, means responsive to the saidsetting of the said steering switch to select a given one of the said other connector switches or the said combination switch, and means responsive to the second action of the substation sender to cause the said selected switch to operate to make connection with the terminals of the desired called line. i

3. In an electromechanical telephone switching system, the combination,with a main station trunk circuit, of? a telephone .line adapted to be connected thereto, ofa telephonesubstation for the said line, a sending device at the said substation, switching mechanisnrfor the said trunk circuit under the control of the'said sending device, the said switching mechanism comprising a plurality of switches, oneof the said switches being a steering switch and auother of the telephone switching system, the combination with aof the said combination switch, a pluralityof other connector switches, means responsive to the said setting of the said steering switcn to select a given one of the said other conneitor switches or the said combination switch, means responsive to the second action of the substation sender to cause the said selected switch to operate to make con-.

nection with the terminals of the desired called line, a plurality of brush sets on each of the said switches, and a relay responsive to the setting of the said steering switch to determine which brush set of the selected switch shall be used to make connection with the terminals of the desired called. line.

4-. In an electromechanical telephone switching system, the combination with a main stationtrunk circuit, of a telephone line adapted to be connected thereto, of a telephone substation for the said line, a sending device at the said substation, switching mechanism for the said trunk circuit under the wntrol of the said sending device, the said switching mechanism comprising a plurality of switches, one of the said switches being a steering switch and another of the said switches being a combined register and connector switch, means to operate the sub- "ion sender to give the said combination ,h a predetermii'ied setting in accordance with the first digit of the called line number, means responsive thereto, to cause the said steering switch to take a setting corresponding to the set-ting of the said combination switch, means operative after the said setting ot' the steering switch to cause the said combination switch to always take a second setting which is the same for every case being independent of the first position setting of the said combination switch, and means responsive to the second operation of the said substation dial to operate the said combination switch to cause it to make connection with the terminals of the desired called line, a plurality of brush sets for the said combination switch, only one of which is used to make the above desired con-- nection with the called line, and relay means responsive to the said steering switch setting to select a particular brush set to make connection with the desired called line.

5. In a telephone system, the combina' tion with a-telephone line, a plurality of central oflicc trunk circuits, at line switch for the said line adapted when the said line is a calling line, to interconnect the said line with an idle one of the said link circuits, a line relay for the said line switch, substation apparatus for the said line\ means under the control of the said substation apparatus to operate the said line relay, means under thecontrol of the said line relay tooperate the said line switch, normal circuit connections from the line conductors of the said line to thesaid line relay, substitute circuit conductors for connecting the said line relay to the said line conductors when the said switch is operating, the said substitute conductors comprising normally open contacts of the said line relay, substation apparatus to disable the said line relay, whereby the said line re-v lay is operatively dissociated from the telephone line conductors by the rupture of the said normally opencontacts. I y

6. In a telephone system, the combination with a telephone line, substation apparatus for the said line comprising a sub station sending device, an idle trunk circuit, a line switch for the said line adapted to make connection with the said idle trunk circuit, switchingmeans in the said trunk circuit under the control of the said send ing device, a line relay controlling the said line switch, substation apparatus adapted to operate the said line relay when the said line is a calling line, normal connections for the said line relay to the said line comprising normal contacts of the said line switch, secondary circuit connections to connect the said line relay with the said line conductors when the said switch is operated, the said secondary circuit connections comprising normally open contacts of the said line relay, which contacts are closed when the said relay is operated, and disabling means for the said .line relay under the control of the said sending device.

7. In a telephone system, the combination with a telephone line, substation apparatus for the said line comprising a substation sending device, an idle trunk circuit, a line switch for the said line adapted to make connection with the said idle trunk circuit,

as v

switching means in the said trunk circuit under the control of the said sending device, a line relay controlling the said line switch, substation apparatus adapted to operate the said line relay when the said line is a calling line, normal connections for the said line relay to the said line comprising normal contacts of the said line switch, secondary circuit connections to connect the said line relay with the said line conductors when the said switch is operated, the said secondary circuit connections comprising normally open 'con'tactsot the said line re- .lay, which'contacts are close drwhen-the said relay is operated disabling means for the said.:line relay :under the control of the "said sending 'device,the said disabling means operating to disable the'said' line relay to rupture the said SBQOIldiLIjZgOOIHlBCtlOIlS when t-liexsendin x device is operated to control 1 I l the said switching ineans.

8, In a telephone system, an incoming ci'rcuit, inulti-brush automatic switch- ".glnd-lylCll la l to isaidf incoming ClICult, a

pluralityf of outgoing circuits arranged in groups iterminating in said automatic switch, a'set of brushes on said switch for each group of outgoing clrcuits terminating .the eat, -I11G&1IS .IO1 moving all of said'sets' of brushes into/successive engagement with the terminals of;said'outgoing circuits, means including a progressively 'movable switch '.associated with said nulti-brnsh switch for controllin g'the operation" of said automatic. switchjand means including said progressively movable switch for selectively rendering one orianother of said sets of brushes effective to connect said incoming.

circuit to a 'wanted foutgoing circuit.

In a telephone" system, an incoming circuit, a plurality of automatic, sw tches individual to said incoming circuit, groups of loutgoing' circuitsterminating in each of {said automatic switches, each automatic switch being provided. with a, set of brushes for ea'ch egroup ofoutgoing circuitsterimi -a i gf t er at, m ns? nclu ng a p gressively movable switch n'dividu'al to said .incomingcircuitfor rendering; effective one or another of said jaut-omatic' switches to select a group of trunks, and means 'includ ing said PIQgI SSIVBb IIIOVablGSwltch for ,rendering effective 'aset of brushes off the said incoming selected switch for extending circuit of the circuit to awanted outgoing selected group. I

10; In, a telephone system, a subscribers telephone line, a plurality of trunk lines, a non-numerical switch for extending said subscribers-line to an idle trunk line on the initiation of acall, a plurality of struc 'turally independent switches individual to each trunk, groups of outgoing circuits terminating in each of said automatic switches, means including a progressively movable switch individual to a selected trunk for rendering one or more of said automatic progressively movable switch associated with said incoming circuit and means includingsaid'automatic switch for variably setting said progressively movable switch in accordance with its own ad ustment, and

means including said progressively movable switch for selectively rendering effective one of said setsof brushes of said automatic switch for connecting said incoming circuit a to a wanted outgoing circuit.

In testimony whereof, I. hereunto subscribe my name'thisf29th day of March A. D. 1919.

A WVI'NFRED T. POWELL.

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