US1197989A - Automatic telephone system. - Google Patents

Description

C. S. WlNSTON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED AUG.5, 15112.

Patented Sept 12,1916.

3 SHEETS-*SHEET I.

C. S. WINSTON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED AUG.5, 1912.

Patented Sept. 12, 1916 3 SHEETS-SHEET 2 WN DQ .WN

C. S. WENSTON. AUTOMATlC TELEPHONE SYSTEM.

3 $HEET$$HEET 3.

Patented Eept. 12,

ZZEUEZZZZT' HZZZU:

APPLICATION FILED AUG.5; 1912- useful am. is. -45

"a e a mmmmmmm CHIkRLEiS 5i. 'W'fllllElTUlJ, 01* CHICAGO, ELLEN 31$, ASSIGNOR T0 KELLOGG SWITCHIBOARD AND SUPPLY CQMPANY, GE QHIGAGU, ILLINOIS, A CORPORATION OF-ILLINOIS.

ilfll'l'flll'lA-IPIC TELEEEHQNE SYSTEM.

meteor To all whom it 112 (1;); concern:

Be it known that l (luxuries S. ll ius'rou, a citizen of the United States of America, residing" in l liickugo county o'l (look, State of lllihois, have invented certain new and.

luiproremcuts in Automatic Telephone Systems of which the following 13 a specification.

lily invention relates toms employing step-by.-step switches tor u'ialciug connection between subscribers lines. ilhe switches are of the well known type having preferably two (lirectious of movement and comprise a bank oi contacts and a movable wiper arlapltm'l to make connection there ith. The bank conto telephone syssists of groups of contacts, and the wiper is adapted to be moved first by directive impulses under the control oil? the subscriber to a desired group, and then moved autoi'uatically, and iiulepeudeutly of the subscriber to the first idle cont: ct in the selected lyrouo. The movement of the wiper to the group oil contacts is usually in one ilirectioh, and the .uioremcut to the idle con tact in that group is usually in another rlimotion of morcmel'it, but theparticular c011- structiou oi the switch is uotimportant to my invention as any kind of switch may be employed that selects first a group of contacts, and then an idle contact in the se lected. group.

llly in'veution is also of the two wire or metallic line type. That is, the impulses for operating" the switches are sent over the two limbs of the telephone line in series, so that no ground connections are uecessar at the subscribers stations.

l-l erctoztore in two wire automatic telephone systems it has beeu necessary to employ combinations of quick and slow relay for controlling the steuby-stcp switches. The slo Y acting relayv in such prior systems had its eircuit lu'olien each time the quick acting, or control relay received an impulse of current over the telephone line, but due to its construe-tum .it wasnot sullicieutly leenergized to release its armature during the sending of said impulses. The retarded. re lease m such slow acting: relays was secured by providing" comier shell for the core of ti relay, or a retarding winding 'tl'ieretor, either of i Ire-:guirecl special. constructiou. 'lh action in said sluggish. relays necessary to prevent the specification of Letters Patent.

a utouiatio Pa: touted Sept. 12, 1916.,

Application filed August 5, 1912. Serial No. 713,425.

armature. The release of'the armature 0fthe slow acting relay closed the circuit of the secondary magnet to automatically move the wipers ot' the switch to an idle contact in the selected group.

In my invention I still employ the meallic line circuit without ground at the sub- .l. h scribers station, sending the directive impulses over the two limbs of the telephone line in series, but I do not employ any combination of quick and slow acting relays to control the switches For this reason it is only necessary in my system to send one series of impulses from the subscribers line to control the switch in selecting; an. idle trunk, and th s single series of lmpulses preferably are all of the same character or duration. quick and slow relay systems, to have impulses of different character, that is, quick impulses to operate the quick relay, and a long impulse or circuit condition to afl'ect the slow relay. 1 am also enabled to have all of the relays for controlling the switches equally quick in action, without the addition of windings or'sleeves to make them slow to respond in one direction.

In. my system a relay which closes the circuit of the secondary magnet to move the oviper of the switch to an idle contact in the group after the directive impulses have been sent, may be of the same character and the same construction as the relay which olperates over the telephone line in response to the directive impulses from the suloseribers station. Both of these relays are equally quick to attract their armatures and equally quick to release them when deprived ot curreul'w As sta 211,1 therefore dispense with specially constructed relays des' zecl tb give a slow or sluggish action, and in alddition to this saving of expense, and simplicity olf mz'u'iufactme, I am able to accomplish the result by a single series of It is not necessary, as in the impulses sent over the subscribers line, all

. of said impulses being of the same character or duration.

In the present embodiment of my invention, I accomplish these results by providing a high resistance path for the current flowing in the winding of the relay corresponding to the slow or sluggish relay in said prior systems.

During the sending of the impulses to dlrect vely operate the switch,

the circuit of said relay is not broken, or

other-wise it would immediately release its psi" armature, but instead of having its circuit broken as these impulses are being sent, as is the case in systems employing slow acting relays, the circuit of the corresponding relay in my'system is closed through said high resistance during the intervals 'of said impulses, and sufficientcurrent flows through 120- lows its armature to fall back. The relay is not deprived of energizing current during the operation of the primary relay, and holds its-tar ature attracted solely for this reason. Th e arrangement is such that sufficient' current will not How through the high resistance path to keep said relay energized for a longer timev than during the interval betiveen said impulses. Accordingly, after (said impulses have been sent,

*and the group selected, there. is not sufficient current flowing through the path containing saidhigh resistanceto keep the relay energized, and it accordingly releases its armature, closing the path for current through the test relay T which relay immediately energizes and closes a path for current through thesecondary driving 1nagidle contact in the selected group.

For better understanding of my invention reference is had to the accon'ipanying drawings in which all parts are shown in their normal position, and in which like reference characters indicate like parts, Figure 1 comprising parts 1, 2 and 3 illustrates an automatic telephone system embodying iny invention; Fig. illustrates diagrammat1cally a mechanism adapted for use with the line circuit B; Fig. 3 illustrates in perspective a diagrammatic view ofa contact bank and wiper arrangement of the selector and connector switches.

Referring now to the system of Fig. 1, it illustrates a so-called 10,000 line system net, which moves the wipers to select an and I have shown only sufficient apparatus to connect a calling and called substation. In the preferred embodiment of my invention as here illustrated I employ line switches B, first selectors C, second selectors D and connectors E. Assuming a. system of 10,000 lines, there would be 10,000 substations A each connected by line conductors L to a line switch B, and these switches B would be divided into groups of 100 each grouped on a basis of trunking), each group of 100 having access to 10 first selectors C, which are multiply connected to the terminals of their iISSOrihtOtl 100 line switches B. That is, each group of 100 line switches would be so wired to its corresponding group of 10 first selectors that each line in any group would have access to the entire ten first selectors, and could select the first first -selector in the. group that happened to be idle. There would then be 1000 first selectors C divided into groups of 10 each, and there would be 1000 second selectors divided in the same way, ten groups, ten in each group. Referring to Fig. 3, when the subscriber removes his telephone in initiating a call, his line switch would be started and automatically select the wiper or movable contact 3% of the first idle selector in the group of ten to which his line had access. This wiper 34' through the bank contacts 41, 4-2 and 43 would have access to the wipers of the second selector switches. Each vertical row 41, .42 and 43 of bank contacts indicated upon the first selector switch in Fig. 3 corresponds to one of said groups of ten second selectors. Accordingly, after the call was extended to a first selector, the subscriber would directively operate the wipers 34 of said first selector by giving them a rotary motion to bring them opposite the vertical row of contacts thereof corresponding to the dcsired group of ten second selectors, and al ter reaching said row, the switch wipers would be automatizally operated'to select the first idle second selector in that group. There would be also 1000 Connector switches arranged the same as the first andsecond selectors in ten groups of ten switphcs in each group. After connecting with the. wiper of a second selector, the subscriber would directively operate said wiper to select the desired group of ten connectors, said groups corresponding to the vertical rows of bank contacts of Fig. 3, and after selecting said group by a. rotary movement of the wipers 34, the second selector would then be automatically operated to move its wipers in a' vertical direction o er the se- 125 lected group of bank contacts, to select the first idle connector in that group.

The connector switches have access to 100 subscribers lines, and the lines are con nected multiply to the ten connectors con- 130 LILMJMQ stituting the group at which said 100 lines terminate. The connector thus selected 18 then directively operated in both directions to select the desired line. For instance it l lo. Y

v the first selector, the subscriber would send nine impulses over'his; line to directively operate the wiper 3A. of said first selector (see Fig. 3) to bring them opposite the ninth verticelrow of bank contacts upon the selector switch. This row of bank contacts would correspond to the thousand digit of the number wanted, or to the ninth group of ten second selector switches, and sitter thus selectin this ninth group by nine directive impu see, the first selector would be automatically operated to piclr out the first idle second selector in that group. The sole-- scrilccr would then send eight directive impulses corresponding to the hundred digit of the desired line, or to the eighth group of ten connector switches. These eight directive impulses would directivcly operate the wiper 3st of the second selector (which would he the saine in construction as the first selector of Fig. 3), to select the eighth group of ten connectors, which would. he the group at which all subscribers lines in the eighth hundred terminate. After selecting this eighth hundred group of connectors by the eight directive impulses, the second selector would be automatically operated, the some as in the first selector, to move its wipers into engagement with the first idle contact in that group, thus selecting'tlie first idle connector switch therein.

As above stated, the connector switches of each group are "multiply connected so that each connector of the group has access to any one the 100 lines terminating thereat, the 100. contacts upon, each connector representing 100 subscribers lines. After selecting tin idle connector, the subscriber would then directively operate the wipers of the said connector switch in both directions, sending four directive impulses to move the wipers in a rotary direction opposite the fourth row of vertical contacts shown in Fig. 3, which would correspond to the tens digit of the desired line, and would then send six directive impulses over the line to move the wipers in a vertical direction to the contact in said selected group corresponding to the units digit of the desired line, this contact being the line of the c: lled subscriber.

'l'l\o construction of the switches and the grouping; there f, as above des ilie l. well as the operation of the wiper tit rectivcly to a desired group, and then onto musically to an idle contact in the selected group, are old anclwell known in the art, but have been set out in detail for a clearer understanding of my invention. It is to a new method of operating the first and second selectors in a two wire system, that my invention relates.

In prior two wire systems quick and slow relays were employed, the quick relay was vibrated by impulses over the line to move the wipers opposite the desired group of contacts (corresponding to the vertical. rows of Fig. 3), and the slow relay was made suiiiciently sluggish in action so that its armature did not drop back when. its circuit was broken by the sending of said directive impulses. When the desired group was selected, however, the (:ircuit of the sluggish relay was broken for a suilioient length of time to allow its armature to drop back, and this closed the circuit of the automatically operated driving magnet, to more the wipers over the selected. group in search of on idle contact.

The dcrelopmein; oi the art at the present time demands :1 two wire or metallic line circuit without grounds at the suhscribefs station, and said quick and slow relay systems are adapted to operate over such in'e' tallic lines. My invention consists of means for operating said switches over metallic line circuits without the necesty oit'using slow or sluggish acting relays Instead of quiclc and slow acting relays forobtaining the movement of the wipers first to e. desired group, and then to an idle contact in that group, I employ two quick acting relays, both of said reluys being equally quick to attract and equally quick to release their urmatures. 'lhus copper sleeves, coils, or other adjuncts to make the relays sluggish in action are dispensed with. One of these quick acting relays in my system is en'iar gized over the metallic line to directivcly operate the wipers to uiove them to the desired.-

armature would drop back, and the wipers of the switch would be started automatically to select an idle contact, before the desired group of contacts had been reached.

ii" the pit out form my invention, the main hing oi? the urmuture ot .his SQCOiiCl quick acting relay, which corresponds to the sluggish relays in said prior systems) in attracted position, while the impulses are being sent from the subscribers station, and

the subscribers stations said impulses being.

of uniform duration. A plu 'ality of series of lmpulses of unequal duration are not necessary.-

Referring now more in detail to the appa- 1 ratus and circuit arrangement preferably employed in thisembmliment of my invention, substations A are of the well known Kellogg type having a calling device 1 with its interrupter contacts 2 connected in circuit with the line conductors, the impulse wheel 3,. being so arranged that when advanced, its teeth will not interrupt the contacts 2 but upon being restored by its spring it will interrupt said contacts '2 according to the number of teeth on its periphery which were initially moved beyond said contacts. The line L comprising line conductors 4 and 5 extends from substation A to its line switch B.

Line switch B comprises a line relay Llt, cut-oif relayGO, motor magnet M, otf-normal contacts ()N, and a pair of line wipers 9 and 12 and cooperating contacts together with a test wiper 10 and cooperating contacts.

Fig. 2 illustrates diagrammatically a switch mechanism adapted to operate in connection with circuit B, like reference characters indicating correspomling parts. This switch comprises sets of bank contacts and cooperating wipers mounted upon a central shaft carrying a ratchetwvheel 6 adapted to be driven by motor magnet M. It will be noted that two check pawls 7 and 8 are employed, pawl 7 being normally in engagement with ratchet (3 while pawl S is normally out .of engagement with said ratchet. In the preferred operation of Fig. 2, which is in accordzmcc with circuit 13, upon initiation of a call by removal of the receiver from the switch hook. line relay LR is energized thus causing the associated pawl 8 to engage ratchet wheel (3 and tl'icreaftcr cut-off relay CO is energized causing its associated ratchet 7 to disengage from ratchet Wheel 6. Thereafter the motor magnet M advances the wipers over the contacts followed by the de'energization of CO, but LR is maintained energized so that both pawls 7 and 8 are engaging ratchet (3. To release switch B line relay LR is deenergized thus withdrawing pawl S'from engagement with 'atchet 6 and thereafter cut-off relay CO is again energized moving pawl. 7 out'of engagement with ratchet 0, allowing the wipers to be restored by a suitable spring. On the first step cit-normal contacts ON assume their alternate position and are maintained thus until the wipers are restored whereby said contacts ONare again moved to their normal position. Other forms of line switch may be employed without in any way a fleeting the principle or operation of my invention.

In Fig. 3 I have illustrated diag animatically the contact bank and wiper arrangement of one form of selector and connector switch that maybe used with my invention. and for a more complete understanding of the switch structure reference is to be had to an application of \Villiam Kaisling for automatic switch for telephone systems, Serial No. 000,604, Patent No. 1,131,140, filed January 3rd, 1911.

Any form. of switch adapted to select a group of contacts. and then an idle contact in the group, would be equally within my invention.

My preferred switch, referred to in the previous paragraph (see Fig. 3) in general comprises a bank of contacts (which I have indicated inclosed in dotted lines), made up of 100 sets of contacts, arranged in ten vertical groups, ten sets in each group. Each set consists of three contacts 41., l2 and 43, (which for clear illustration I have spread apart at the first set in Fig. 3, and which correspond to contacts 41, 42 and 43 in Fig. 1, Part 1, contacts 41, 12 and 43 in said figure corresponding to the next set 25 in Fig. 3). A set of wipers 34- consisting of wipers 34, 35 and 36 are provided to.

wipe over the corresponding contacts in the vertical groups. (These wipers correspond to wipers EH, 35 and 3G in Fig. 1, Part 1).

A primary magnet (PM. Fig. ,1, Part 1) is adapted to rotate the wipers through the medium of a primary shaft PS to bring them opposite one of the vertical groups of contacts. This group selecting movement is in response. to directive impulses sent over the line from the subscribers station. A secondary magnet (SM, Fig. 1, Part 1) is provided to step the wipers in a vertical direc tion through the medium of a secondary shaft SS to select an idle contz'ict set in the selected group. This secondary moven'lent to select an idle set of contacts in the selected group is accomplished automatically, without the aid of directive impulses from the subscribers station. The switch construction is preferably such that the i e-ls are advanced against the tension of a. pair or so-calied Watch springs, one spring opposing each movement respectively.

To release the switch Wipers, and restore them to normal position after connection with one of the sets of contacts in a group,

ment of the switcl'i wipers. Relay 3R operates on the same principle as relayMRR,

as will be more particailarly pointed out.

Second selector l) Fig. 1, Part prefm'ably of the same cmistxrimtion as the first the secondary magnet is again actuated to step the wipers beyond the last or top con tact of that group, whereby they are automatically restored to normal by the springs referred to, the wipers in being restored taking the path indicated by arrows in h i Thus, in the operation of the switch the contacting ends of the wipers travel in a primary direction (rotary) to select a group of contacts, then in a secondary direction (Vertical) to select a contact in that group and in the release of the wipers this sec-- ondary travel is continued until the 1001' tacting ends have passed beyond the last or top contact in the group, when they are automatically released as shown.- by the arrows to normal position A set of primary oil-normal spring; contacts PON are moved upon the first priina-ry step of the switch while a set of secondary oil-normal spring contacts SON are 'mored upon the first secondary step of the switch, being restored upon restoration of the wipers from their respective movements as will be clear from the diagram. It to be understood that for a more detailed description of this switch,reference. is to be had to the above identified. application.

First selector C comprises, besides its wipers and bank contacts, a primary magnet PM, asecondary magnet SM, .a primary relay PR adapted to be energized by current over a calling line upon connection made with said switch C, a main release relay MRR which is adapted to be energized responsive to the initial cncrgization of relay PR, a release relay R t ada' 'ited to be energized responsive to the initial energization of MR1 and a secondary relay SR adapted to be energized 't'ollowii'ig the cncr gization of RR. An ximpulse relay lll is also provided being controlled by the primary relay PR and adapted to transmit directive impulses for causing an operation of the switches, while a. test relay T is adapted to be energized to elicct the secondary movement of switch 0 to cause a scoondary travel thereof to select an idle set of contacts in the selected group.

Upon the initial energization of relay Milli a locking circuit for itself is provided. through its contact 25 and high resistance R, so that when its initial energizing circuit is interrupted due to the vibration of relay PR, a maintaining circuit through this high resistance It is closed. The current flowing through the winding of MRR maintains its armature attracted while relay PR is vibrating in response to impulses over the tele phone line, whiohcausethe primary moves selector, and comprises wipers and suitable bank contacts, operatingmagnets PM SM, 2, release relay ltlt and test relay '1. Oil normal switches PON and blUll are also provided.

Connector switch E of the same construction, com prises, besides its wipers and 0061 crating; contacts ell-nornml switches PON and SON, operating magnets PM, BTW, release relays llltflillll, switching relays Fill and till a linetcst relay LT, a relay ll, controlled by relay LT, and maintained energized while U5. is energized, a llipdlop or interrupter relay Fl il or intermittently connecting ringing generator G andthe bridged control relay (it across the terminals ofthc called line, a, disconnect relay Dll for dfii :oiuicctinpthe ringing current upon responseof the called subscriber, a cir-' cuit closing relay (fill also energized when a called subscriber responds and a, busy relay lilFZ for controllin the application of busy sigi'ial from busy back BB.

The called line if, called sub-stationF and associated line switch B are similar to the calling line Gl'lHllHili-Fllil the similar 'iarts being indicated by like reference characters but with the suliix prime.

U/Ifl'fitiZW/t of Fig. i.'l"laring described in general the apparatus and circuit arrangnuncnt in the preferred embodiment of my invention the operation of the system illustrated, in connecting a calling and called line, will now be described.

i-"issuminn a subscriber at station A desires to connect with a subscriber at substation F whose telephone number we will assume is xiii-3 he will remove his receiver l rom its switch hookwhercby a circuit "for line relay l ill is established from battery through the winding of Lil, wiper 5), normal contact if), line conductor :i-Q'snbstatirm A, line conductor 4, normal contact ii, the

wiper iii to ground. liclay LR is thus enersized closing its alternate contact 133 and .stablisliing an energizing circuit for cutoli relay CO through normal contact (7N. Relays LR and all) being; energized, a circuit for motor magnet M is established through their alternate contacts 14 and 15 respectively whereby said magnet M advances wipers 9, l2 and 16 into engagement with the first set of contacts 17, 18, 19, which, We will assume leads to a busy first selector (1. Therefore the test contact 19 thereof is grounded through primary ofi normal contacts POW, said contacts being till in their alternate position when the selector G is busy, and a locking circuit for relay LR 1 1 C0 is therefore established which may be traced from ground through PON contacts. wiper 1t: and alternate contacts 20, 21 and thewindings of relays Lli and CO resi'wctivcly. Relay CO thus maintains the circuit of driving magnet M closed notwithstanding the opening of the circuit at oil"- normal contacts ()X at the first step of the switch. Magnet M now ad va uces the wipers another step and in fact continues such advancement until the test wiper 16 reaches an idle test-contact 19 which we will assume is the third one leading to first selectort; Assumingthis is idle. as stated, it would be ungroundcd and therefore the locking circuit for relays Lit and is interrupted, but relay Llt being a slow relay maintains its armature attracted until a locking circuit from switch is provided. which .will be.

later described, but relay CO being a 'niickrelay immediately releases its armature opening, its contact 15 111 thecircuit of dr1ving magnet M, thus rendering the switch wipers inert. As above stated L is one of a group of 100 hues that has access to a group of ten first selectors C, and thus thefirst idle selector C of the group is automatically selected by the removal ot the receiver from the hook of any one of said lector C is established over the alling line,

which may be traced from battery through the left hand winding of PR, the upper heavily marked primary conductor, contact 18, Wiper 12, normal contact 11, the calling line and substation, normal contact 10, wiper 9, the selected contact 17 and the right hand winding of PR to ground, causing its energization.

Upon the closing of alternate contact 22 of PR, the locking circuit above referred to for the slow-acting line relay LR is established, tif aced over contact 19, wiper 16, alternate contact 20, and the winding of LR to battery thus maintaining said relay energized untila release is desired. Also responsive to the'energization of PR a circuit for MRR is established traced from ground at normal contact 23 of PON, alternate contact 24 and winding of MRR to battery causing its energization. Alternate contact, 25 is thereby closed establishing a second circuit for MRR through the comparatively high resistance R. Also responsive to the closure of alternate contact 25, a circuit is established through thejwinding of release relay RR causing its energization whereby its alternate contact 26 is closed, establishing an energizing circuit for secondary relay SR traced tron said grounded alternate contact 26, nornial contact 27, conductor 28, and

V the Winding of SR to battery causing its energization. Its alternate contact 29 is relays, such as One path for current 'tlirougli' relays MRR' and SR is through the contacts of relay PR. The relays MRRand SR, botlnbningquick acting, would therefore be de'e'nergized and release their armatures while PR was operating to step the, switch around to the desired group, if it were not for the second or maintaining path for current through the windings of these relays including the highresistance R and I "-respective1y. As the first path for these relays through the contacts of relay PR is broken byit's vibration in response to impulses from the substation,

the second or high resistance pathbeing closed maintains them in energized position, so that the relays MlilVand SR are not deenergized buthold their armati'fies attracted jnutil sutticient impulses have been sent through PR- to move the Wipers of the Switch to the desired group of contacts. The high resistance path, however, only furnishes sufiicient current to energize the relays MRR and SR between the intervals or vibrations of relay PR, so that when the desired group of contacts is reached and relay PR ceases to vibrate, relay SR, being energized now solely over the high resistance path, releases its armature, resulting in the operation of secondary magnet SM to move the wipers of the switch to the, first idle contact in the selected group. If SR should be deenergized or release its armature while relay PR was vibrating the desired group would not be selected, but the wipers would be started in a vertical moven'ient to select an idle contact in some group, before the desired vertical group of contacts was reached. (See Fig. 3). It is, thus apparent that .second relay SP, while quick acting, and the same in construction in this respect as relay PR,

vibrations of the latter, not because of any retarding means added thereto, but because itis continuously supplied with energizing current during such vibrations. Instead of retarding means the relay SR and the other relays in my invention that correspond to the slow acting or sluggish relays in other systems, are provided, with two separate paths for energizing current, in the present embodiment, one of these paths being a low resistance path and the other a comparatively high resistance path. Said secondary SR in Fig. 1, are first energized over the low resistance path through contacts of relay PR, and when this low resistance path is interrupted by the vibrations of relay PR, the ,high resistance path held energized and kept in actuated condition by current flowing in this high resist contact 2a is closed" causing an operation of impulse relay IR, the three operations there of causing the transmission of three primary or directive impulses to the primary magnet PM of the selected switch D. Responsive to the first of said deenergizations of PR, its normal contact 22 is again closed establishing an initial or low resistance energizing circuit for the secondary relay SR traced through alternate contact 27, conductor 28, and the Winding of SR to battery. lelay SR again. closes its maintaining contact 29 whereby a second or alternate circuit for relay SR is again closed through the high resistance R and the right hand end winding of PR to ground as previously described. This second circuit for SR is effective to maintain its armature attracted while the primary impulses are coming from normal contact 22, but as previously described, upon the cessation of these primary impulses the flow of current through the second. circuit alone is not sufficient to maintain its armature attracted whereby it restores effecting a secondary circuit change for switch I) as will be described.

Referring now to the said three operations of relay PR, three impulses of current are transmitted, as previously, through the'winding of relay IR via contact 24 of relay PR- and contact 3]. of relay RR. Said relay IR thus actuates its armature thr e times and transmits three impulses ot *current to the primary driving magnet of switch '1), over a path traced from its alternate contact 32, normal contact 46, wiper 35, contact 42, the upper heavily marked primary conductor to conductor 4L8 of switch 1), normal contact 49 and winding of Pit I to battery resulting in three operationsoft' said primary driving magnet. The wipers 50, 51, 52 of switch D therefore receive three primary steps to select the third group of contacts which are the contacts extending to connector switches in the third hundredths group or the selected thousands group, and which includes the line of the called substation F.

Upon the first primary step of switch I),

the primary off-normal contact 56 is closed so that upon the said retraction of the armature of secondary relay SR, a secondary circuit is established traced from ground through the right end winding of PR, normal contacts 29, 47, Wiper 36, contact 4:3,

the lowerheavily marked secondary con-.

ductor, alternate contact 56, normal contact 57 and the winding of test relay T to bat-\ tery. 'Rplay T is thus energized closing its alternate contact 58 whereby a circuit for magnet SM is established causing it to step the wipers into' engagement with the first set of contacts in the selected group.

.Assuming this first set of contacts lead to a busy connector E, its test contact 53 has a busy or ground potential connected thereto connector Efand there being no busy po- 'tential upon these contacts, the circuit for relay '1 is interrupted causing its dei nergization and the consequent interruption of the circuit for 8M whereby the wipers remain in engagement with the contacts leading to selected switch E.

Upon deenergization of T its normal contact 59 is closed, placing a ground or busy potential upon the selected test contact 53 and its multiples rendering them unselectable. This ground connection also is effective to cause energization of relay BB of switch E, its circuit being traced over test conductor 64"., normal contact 65 and the winding of to battery causing its energization. Upon said restoration oi T its normal contacts 66, 67 being again closed, the circuit from. the calling line is extended through to the connector E.

The subscriber at A now operates his call.- ing device tov eiij'ect four operations of relay lli. this corresponding to the third or tens digit of the called line number, this resulting in the energization of secondary relay SE in a manner as before described and also causing four operations oi impulse relay IR whereby four impulses of current are trans mitted through primary magnet PM of switch E. These impulses to magnet PM are traced from ground at alternate contact 32 of impulse relay IR, normal contact ll), wiper 35, contact 4-2, normal contact 66, wiper 51, contact 54, conductor 68', normal contacts 69, 70 and the winding of PM to battery causing tour operations thereof and four primary steps of wipers 71, 72, 73 to select the fourth group of contacts 7 4:, 75, 7 6, which is the group including the terminals of the wanted line. Following the said primary impulses the secondary relay SR restores its armature in the manner as before described; whereby a secondary circuit is- .PR along the lower heavily marked secondary conductor through switch D, conductor 77 extendlng from the secondary conductor of switch E, alternate contact 7 8 (which isnow closed), normal contacts 79, 80 and the winding of switching relay al to battery. This relay is theretore energized closing its .ance or maintaining path. In my invention,

' to release their armatures after the impulses have been sent, but cooperating with the low resistance path to keep said relays energized until that time, or during the sending of the directive impulses. The manner in which the above operations are effected will now be described in detail.'

' Wenow have relays PR, MRR, RR, and SR energized over the previously described paths. The subscriber at station A now operates calling device 1 to effect operations of impulse springs 2 corresponding in numher to the first digit of the called substation number which is 2, and thus select the second vertical group of contacts (see Fig. 3). The first interruption of contacts 2 causes an interruption of the circuit for the primary relay PR, whereby its contacts momentarily restore to normal, the closure of normal contact 24 (which is now also grounded through alternate contact 30 of RR) closing a circuit for impulse relay IR traced through alternate contact 31 and the winding of IR to battery.' Such an energizing circuit for relay IR is closed responsive to each de'e'nergization of relay PR and upon each such operation of IR its alternate contact 32 is closed establishing a circuit through normal contact 33 and winding of magnet PM to battery causing an operation thereof, each such operation affecting a primary step of wipers 34, 35 and 36.

Referring now to the other contact 22 of relay PR, upon its first momentary restoration to normal, and as soon as alternate contact 27 of PON is closed, a low resistance circuit is'closed through SR, traced from the ground at said normal contact 22, alternate contact 27, conductor 28 and the wind-.

ing of SR to battery, such a circuit being closed each time the armature of PR is vibrated. Relay PR having operated two times, remains energized over the line circuit until the calling device is operated for the second time. Therefore, normal contact 22 is maintained interrupted, and the low resistance circuit of relaySR is opened to allow the retraction-of thearmatureof secondary relay SR to start the secondary selecting operation of the wipers, this being brought about in the following manner: As soon as normal contact 29 of SR closes, a circuit for test relay T is established traced from ground through the right end winding of PR, normal contact 29, conductor 37, alternate contact 38, normal contact 39, and the winding of T to battery, causing its en- 'ergization and the closing of its alternate contact 40, thus establishing an operating circuit for secondary magnet SM and its generator. from the generator operates said magnet to step. wipers 34, 35, and 36 into engagement with the first set of contacts 41, 42, 43 of the selected second group. Assuming the first set of contacts lead to a busy second selector D, the test contact 41 thereof will be grounded whereby a maintaining circuit for relay T'is provided traced from the said grounded contact 41, wiper 34, alternate contact 44, alternate contact 45 and the winding of No battery. As long its test wi-per 34 is engaging a busy test contact 41,

it will be seen that relay T remains energized, so that magnet SM continues to advance the wipers until an idle set of contacts is reached. Assuming the set of contacts shown as extending to second selector D are the first idle set in the group, no busy potential will be present at its test contact 41 so that themaintaining circuit for relay T is interrupted, causing its deenergization and calling substation is extended to an idle second selector switch D in the thousand group, which includes'the line of the called substation.

The first impulse of current the interruption of the circuit for SM,

It will be noted that upon the first secondmy step of switch C its. secondary off-normal contacts SON move to their alternate position disconnecting magnet PM and interrupting the initial energizing circuit for 34, whereby an energizing circuit for-relay RR of secondary selector D is established,

traced over test conductor 61, normal contact 62, and the winding'of RR 'to battery,

causing its energization, whereby its alter-' nate contact establishes a locking circuit for it. This' 'gi'ound potential at 44, placed 7 upon multiple contacts 41 also renders them unselectable by any other first selector.

The subscriber at A.now operates calling device 1 toeffect three interruptions of the circuit for relay PR and responsive to each ensuing deenergization thereof its normal alternate contact 80 and establishing a locking circuit for itself through normal contact 81 to grounded test conductor 64. Alternate contact 82 of relay SW is also closed thereby disconnecting the primary magnet PM and connecting the secondary magnet SM to the primary conductor.

- The subscriber at A now operates his dial to cause three operations of primary relay PR, these operations corresponding in number to the last or units digit of the called line number, whereby three impulses are transmitted from impulse relay IR to switch E followed by the retraction of the armature of SR in a manner as previously described. The said last three impulses of current are traced over the previously described path including the upper or heavily marked primary conductor to conductor 68 of switch E, alternate contact 82, normal contact 83, the winding of SM to battery at. normal contact 84. The ensuing three operations of SM are efi'ective to step wipers 71, 72, 73 into enga ement with the third set of contacts 7 1, 75, 6 which are the terminals of the called line.

Following the transmission of the last series of impulses, secondary relay SR retracts its armature in a manner as previously described to effect a secondary circuit change at switch E by the application of ground through the rightend winding of relay PR to the secondary conductor of switch E. This ground connection then extends over conductor 77, switch E, alternate contacts 78 79, normal contacts 85 and thewinding of'switching relay SW' to battery causing its energization. Its alternate contact 85 isthereby closed establishing a look ing circuit for itself over conductors 86, 87 to .ground at alternate contact 88. Its normal contact 81 is also interrupted thereby interrupting the locking circuit for relay causing its deenergization. Also responsive to said energization of SW its alternate contact 90 is closed to. connect line test relay LT iticincuit with the test contact 7 1' of the seized line. This circuit is traced from wiper 71, alternate contact 91 I (relay BR having been energized over a cir cuit including nqrmal contact 90 and alternate primary otl'normal contact 88 upon the first off-norinal step of the switch). the

lower winding 'of LT, conductor 97, alter nate cont-'actsi 92, 90, conductors 86, 87 to ground at gtlternate contact 88. Although the initial energizing circuit for BB is interrupted at normal contact 90 when SW is energized, BR, being a slow-acting relay, maintains its contact 91 closed until a substitute energizing circuit for BB is established, V roviding' the called-for line is idle, as will be describedl Retu rning now to re lay LT, it will be noted that its lower winding has its terminals connected between ground at alternate contact 91 and the Wiper 71. Up to this period the operation of switch E is the same whether connection has been made with an idle or a busy line but after this period the operation difi'ers depending. upon whether the called line'is idle or busyrfv Gallcol Zing idZe.Aissum.ing that the cuit for LT is established over the said circuit including its lower winding, Wiper 71, contact 74, ON and the winding of CO causing the energization of both relays LT and CO the energization of CO removing the substation control of its line switch B Upon energization of LT, its alternate contact 93 is closed causing the energization of relay H whose alternate contact'94 closes, restablishing an energizing circuit for re lay BR thus maintaining its armature attracted. The closing of alternate contacts 95 95 of relay LT shunts the lower winding thereof, but amaintaining circuit therefor is established from battery through its upper winding and the current reducing. resistance 9G, alternate contacts 95, 95 conductor 97. alternate contacts 92, 90,COI1(ll1C- tors 86, hi, to ground at alternate contact 88. This ground connection is also extended through alternate contacts 95 91 and wiper 71 to the engaged terminal 74 maintaining a direct ground upon this terminal and its multiples and thus rendering the associated line unselectable by any other con- 98, normal contact 99, the winding ofFF and interrupter I to-battery. By the op eration of interrupter I, relay FF is periodically energized thereby operating its C 'ulttlCtS 100, 101 to alternately connect generator G and control relay OR in bridge of the terminals 75, 76 of the called line. Upon each connection of current from ringing generat r G the call bell at substation F is ,operated, the circuit therefor being traced from the upper terminal of generator G, alternate contact 100, wiper 72, terminal 75, over the line and through. the condenser andcall bell of station F, returning through terminal 76, wiper 73, c'on'diictor 102, alternate conlict 101, to the lower terminal of generator i Upon each retraction of the armature of FF, relay GR is connected in bridge of; the called line, this circuit being traced from battery through the upper winding thereof, alternate contact 103, normal contact 100, to

105 nector. Also, upon the closure of alternate .hook thereby providing a path for direct current over the called line.

the terminal of the called line, while the other winding of GR is connected through alternate contact 104:, normal contact 101, terminal 76 of the called line. Due to the book, there is no path for direct current for relay CR so that it does not energize until the called subscriber answers the call and removes his receiver from its switch Thus, when the subscriber at F removes his receiver in response to a call and upon thefollowing deenergi'zation of FF, a path for direct current through control relay GR is provided oryer the previously described path causing its energization. Therefore its alternate contact 105 is closed maintaining relay RR" energized as long as the receiver remains olf the switch hook at substation F and relay (7R thereby energized. This prevents the release of switch E until'the called subscriber replaces the receiver.

gRet-urning now to OR, the closure of its alternate contact 106 is eflective to prevent another application of ringing current to the' called line, also by the ensuing energization of relay CL causing the establishment of talking circuit by the closing of alternatelcontacts 107, 108. Responsive to said .energization of CL alternate contact 109 is closed establishing an energizing circuit for disconnect relay DR which closes its alter-- nate contact 110 establishing a locking cir-' cuit for itself over conductor 87 to ground at alternate contact 88. Relay DR therefore interrupts its normal contact 99 rendering relay FF inert and preventing any frlrther application of ringing current to the terminals of the called line. The two substations are now connected over a conversational circuit including the heavily marked primary and secondary conductors, a condenser 111 being interposed in the primary conductor at first selector; C while a condenser 111 is interposed in the secondary conductor at connector E, these condensers being connected in circuit 'to prevent interference between the control circuits of the respective substations. I i

The talking battery for the calling substation isprovided through the windings of relay PIh-"while talking battery for the called substation is provided through the winding ofrelay CR.

ReZease.- -'After the subscribers have finished conversation by replacing their receivers upon their respective switch books they may effect the release of the switches used in establishing the connection. The release of the switches is preferably controlled from both substations, that is, release of switches B, O and D isefi'ectcd when the calling subscriber replaces the receiver while replaces his receiver, the

the release of the connector E is effected when the called subscriber replaces his receiver. This order of release may, of course, be varied.

Assuming now, that the subscriber at F previously described circuit through relay CR is interrupted at the snitch hook of station F whereby said relay restores. Due to the interruption of alternate contact 100 of CR,

and CO and due to the interruption of alternate contact 93 of LT, relay H restores disconnecting relay CR from the wipers and by the interruption of its alternate contact 94 allows relay BR to deenergize.

Returning now to BB due to the closing of its alternate contacts 83, 8-1 magnet SM is connected in circuit with the alternating current generator 114 whereby the wipers are advanced in a secondary direction as already described causing their restoration and the restoration of the cit-normal contacts. As soon as contact 88 of PON rcstores to normal, relays SW RR andDR restore, as it will be remembered these relays were held energized over.circuits including said grounded contact 88. Upon restoration of RR its normal contact is again closed and as test conductor 64 may still be grounded from second selector D, RR again becomes energized but this is only incidental and has no effect upon the switch at this time.

The cut-off relay C0 of switch B having been restored, the line of substation F is available for use in establishing other (1011- MRR attracted. Said armature therefore restores interrupting alternate contact 25 and thus allowing the release relay RR to restore.

Upon the closing of normal contact 4-5 of RR, a circuit for relay T is established ma /nee traced from battery through the winding of said relay, normal contact d5, alternate contact 27 normal contact 22 to ground. Helay T therefore closes its alternate contact 40 effecting an operating circuit for magnet SM whereby the wipers are advanced to effect their release in a manner as previously described, also causing the off-normal switches to be restored. Upon the interruption of alternate contact 27 of PON, the circuit for relay T is interrupted causing its deiinergization and the interruption of the circuit for SM.

It will be noted that upon the closing of normal contact 22and the release operation nst described, ground is connected through alternate contact 27,'conductor 2S, and the winding of SR to battery causing the energi zation of SR, but this has no efiect upon the release of switch C relay SR again restores when the alternate contact 27 of PON is interrupted.

Anotl'ier incidental operation may occur when the calling subscriber replaces his receiver for release purposes, this being an application of ground over the primary conductor. This is brought about in the following manner.- Upon restoration of PR its normal contact 24 closes, and as relay RR maintains its armature in an attracted position for an instant after restoration of PR, ground will be connected through alternate contact 30 of RR, normal contact 24, alternatc contact 31, and relay IR to battery, causing a momentary energization thereof and causing a short application of ground through its alternate contact 32 to the primary conductor"- This incidental application of ground to the primary conductor in the present embodiment of my invention, is effective to cause a primary step .oi' connector E (if said connector'was released by the called subscriber before the calling subscriber replaces his receiver) but thereafter if said connector E is so operated, it is antomatically restored. This incidental op eration of connector E is brought about'as follows: The ground impulse to the primary conductor follows a path overconductor 68 of switch E, normal contacts 69, 70 and PM to battery, causing a primary step of the wipers 71, 72, 73, leaving the switch offnormal until released as will be described.

Returning now to switch C, upon the said releasing energization )1 operation of-relay T, its normal contact i4: is interrupted disconnecting ground from test wiper 34 whereby the locking circuit for BB of switch D is interrupted causing its restoration. A release circuit is thus closed for relay T? traced from ground at alternate contact 115 of PON, normal contact through winding of T to battery. Its alter nate contact 58 is thereby closed establishing an energizing circuit for SM whereby the Now as to the restoration of switch B,

this effected upon restoration of switch C due to the interruption of alternate contact 23 of PON. this bringing about the restoration. of relay LR which has been held energized through this alternate contact 23. Upon restoration ofLR its normal contact 13 is closed connectingground through alter- I nate contact ON and the winding of CO to battery. Thus relay LR being deenergized and relay CO energized, both retaining pawls'i', 8 are disengaged from the ratchet 6 allowing the wipers to be restored. Upon restoration of contact ON the circuit for CO is interrupted causing its deiinergization whereby switch B isat normal and available for use in extending other connections.

Connector B it will be remembered was incidentally stepped-one point oil normal, and relay BB thereof was energized over the circuit including the grounded test 0on duc'tor G l. But, upongthe removal of this ground due to the interruption of normal contact'59 of relay Tfl'switch D, relay RR? restores energizing relay RR and causing a restoring operation of switch E from the incidental operation.

In the-previous description of the release operation it was assumed that the subscriber at the called substation was the first to replace-the receiver upon. its switch hook. We will now trace the release operation under the assumption that the subscriber at the calling substation was the first to replace the receiver followed by the replacing of the receiver at the called substation. In such a case relay PR decnergizes upon replacing the receiver at substation A, causing a restoration of the switches C, B and D in a manner as prev-ioi'lsly described. In this instance the connector switch is not affected because its release relay RR is energized over a path including grounded alternate contact 105 of relay CR, said relay CR being maintained energized over the calling line. Therefore, when the subscriber at substation F replaces his receiver, relay CR restores to normal followed by theldeiinergization of RR while due to the interruption of alternate contact 106 of CR, relay CL restores. of BB relay RR energizes closing a-cirs cuit through SM whereby the wipers aria automatically restored in a manner as pro vie ously described. Also, upon restoration of Responsive to the restoration BB due to the interruption of its alternate contact 92, relays LT and CO restore, the restoration of alternate contact 93 of LT causing the restoration of relay H followed by the restoration of BB as before described. Upon restoration of PON relays DR and SW are restored whereby the switch being at normal is available for further use in establishing other connections.

. The restoration of C0 of line switch B restores the substation control of its line switch whereby the line is free to be used in establishing other connections. Called Zine busyr-In the previous description it was nssumed that the called line was idle upon connection made therewith. It will now be assumed that said line is a busy line upon connection being made therewith, in which case its test terminal 7% will have a ground or busy potential connected thereto either from alternate contact 13 of switch B if the line be calling, or't'rom the grounded test wiper 71 connected to multiple of terminal Tl if the line he a called line. g

It will be remembered that following the last. secondary-circuit change, relays RR SlV and BR were in an energized condition and the closing of alternate contact 91 of relay BR had connectedthe lower winding of line test relay LR in circuit between ground at alternate contact S8 of PON and test wiper T1 and terminal Tat. It will be rem c1nbered also that upon connection with the idle line relay LR was energized, but in the present case there being ground or busy potential upon test terminal 74;, no energizing circuit for LT of T is provided as both of its terminals are connected to ground, and it remains inert. Therefore, relay H is not energized so that slow-acting relay BR restores closing its normal contact 117 connecting busy back BB through al ternate contact 70 and normal contact 82to the primary conductor. This busy tone fol-v ground. The subscriber at A in response to this signal knows that the wanted line is busy and therefore replaces his receiver upon its switchhook interrupting the circuit for relay PR. Upon restoration of'relay PR, switches C, D, and B are restored in a manner as previously described, and in the pres ent instance switch E being off-normal is also restored. This is brought about in the following manner. Upon the interruption of normal contact 59, relay T of switch. D, the energizingfcircuit for BB is interrupted (relay CR nothaving been energized) causing restoration o'fRR whereby its normal contact 113 is clo's l'connecting ground from 'to find an idle trunk.

alternate contact 88 through thewinding of RR to battery. Relay RR" closes its alternate contacts 83, 8-1 establishing an operating circuit for SM as before, whereby the wipers are advanced effecting the restoration of switch E in a manner as previously described. Upon interruption of alternate contact 88 relays R11 and Si 71 are restored and switch E being at normal is available for use in establishing other connections. 75

In connection with line switch B, means are provided to indicate to the calling subscriber when such switch has not been able For instance if all of the trunks leading from contacts 17, 18, 19 are busy, their test contacts 1!.) will be grounded causing the switch to step to the last set of contacts 17 18, 19". There being no ground connected to terminal 19, relay CO immediately deenergizes but relay LR maintains its armature attracted due to its slow acting construction so that upon the closing of normal contacts 10, ll. of CO, a locking circuit for LR is established from ground through busy back BB, terminal 18 9G wiper 12 over the calling line, returning to wiper 9, contact 17 contact 19 wiper 16, alternate contact '20, and winding of LR to battery. A characteristic signal is thus transmitted from BB over the path just described whereby the subscriber at A. receiving such signal knows that all of the trunks are busy and therefore replaces his receiver upon its switch hook. The circuit for LE being thus interrupteihit restores to normal closing an energizing circuit for CO as before, and relay LR being deencrgized and CO energized, both retaining pawls 7,8 are disengaged from ratchet wheel 6 and the wipers restore to normal. Upon restoration of ON, relay CO is'deenergiz'ed.

Several alternating current generators are illustrated, these being used for efi'ecting the operation of certain of the motor magnets, but it is to be understood that these generators may be all one and the same but have been shown in this manner to simplify the drawings. Also a number of batteries are shown in diiferent parts of the drawings but it is to be understood that these may be one and the same batteries, and those terminals which are shown connected to ground,- in practice would be connected to the grounded terminal of the battery.

While I'have embodied my invention in what is known as a complete automatic telephone system, it is apparent that my invention is by no, means limited to such a system and furthermore while I have embodied it in circuits for controlling switches of certain characteristics, my invention is not limited to such particular switches. Also scribed but aim to cover all that which comics within the spirit and scope of the appended claims. a

Having described my invention, what I claim as new and desire to secure by Letters Patent is:- 1

1. A telephone system including a automatic switch, a metallic control circuit for said switch including a primary relay energized by current over said metallic circuit and responsive to rapid interruptions there? of, a quick-acting release relay having an energizing circuit closed responsive to the initial energization of the primary relay and interruptedresponsive to said primary relay operations, a second energizing circuit of comparatively low current value andcontinnous flow for said release relay,- and means for closing it and holding it closed during the period of said interruptions of its first said circuit, and operating and release means for/said" switch controlled by said primary a'nd release relays.

2.; A telephone system including an auto- ..miitic switch, a metallic control circuit for said switch including a primary relay energized by current over said metallic circuit and responsive to rapid interruptions thereof, a quick-acting release relay having an energizing circuit closed responsive to the initial energization of the primary relay and interrupted responsive to said primary relay operations, a second energizing circuit of comparatively low current value and continuous' flow for said release relay and means for closing it and holding it closed during the period of said interruptions of its first said circuit whereby its armature is maintained attracted during such interruptions, operating means for said switch responsive to said primary relay operations, release means for said switch rendered ineffective while said release relay has its armature attracted, and

"means for causing a prolonged interruption ofsaid metallic circuit whereby said pri- "mary and release relays are restored and said release means rendered effective.

" 3. A telephone system comprising a metalliecircuit telephone line, an automatic switch, a primary relay energized by current over said line and responsive to rapid interruptions of said metallic circuit, a quickacting release relay having a high current value energizing circuit closed responsive to the initial energization of the primary relay and interrupted responsive to said primary relay operations, a second energizing circuit of comparatively low "current value and continuous flow for said release relay and means for closing it and holding it closed during theperiod of said interruptions of its high on rent value circuit, and operating and rele se means for said switch controlled by said primary and release relays respectively.

'4. A telephone system comprising a metallic circuit telephone line, an automatic switch, a primary relay energized by current over said line and responsive to rapid interruptions of said metallic circuit, a quickacting release relay, means for closing an energizing circuit for said relay responsive to the initial energization of the primary relay and interrupting said circuit responsive to said primary relay operations, a secswitch, a quiclcacting release relay energized responsive to said energization of the primary relay, said energizing circuit for the release relay being over a low resistance path, means for causing rapid interruptions of said metallic circuit to cause similar operations of said primary relay whereby said low resistance energizing circuit for the release relay is rapidly interrupted, a second comparatively high resistance energizing circuit of continuous flow for said release relay and means for closing it and holding it closed during the period of said interruptions of its said 'low resistance circuit, and operating and release means for said switch controlled by said primary and release relays respectively.

6. A telephone system comprising a metal lic circuit telephone line, an automatic switch, a primary relay energized by current over said line and responsive to rapid interruptions of said metallic circuit, a quickacting release relay having a low resistance energizing circuit closed responsive to the initial energization of the primary relay and interrupted responsive to said primary relay operations, a second comparatively high resistance energizing circuit of continuous flow for said release relay and means for closing it and holdingit closed during the period of said interruptions of its low resistance circuit, and operating and release means for said switch controlled by said pri-. mary and release relays respectively.

7. A telephone system including an auto matic switch, a metallic control circuit for said switch including a primary relay energized y current over said metallic "circuit and r "ponsive to rapid interruptions thereof, p 'imary driving mechanism for said switc responsive to said primary relay operati us, a quick-acting secondary relay having an energizing circuit closed responsive to saidprimary relay and interrupted responsive to said primary relay operations, a second energizing circuit of comparatively" low current value and of continuous flow for said secondary relay and ,ineans-i'or closing it and holding it closed during the period oi said interruptions of its first said circuit .whereby its armature is maintained attracted during such interruptions, said armature being retracted upon cessation of said priniary relay operations to effect a secondary circuit change for said switch.

8. Atelephone system including an automatic switch, a metallic control circuit for said switch including a primary relay energized by current over said metallic circuit and responsive to rapid interruptions thereof, primary driving mechanism for said switch responsive to said operations of the primary relay, a quick-acting secondary relay having an energizing circuit closed esponsive to said. primary relay and interrupted responsive to said primary relay operations, a second energizing circuit of comparatively -low current value and of continuous flow for said secondary relay and means for closing it and holding it closed during the period of said interruptions of its first said circuit whereby its armature is maintained attracted during such interruptions, said armature being retracted upon cessation of said primary relay operations whereby a secondary circuit change is effected, means for causing a secondary oper ation of said switch responsive to said secondary circuit change, and means for restoring said switch.

9. A telephone system including an auto-- matic switch, a metallic control circuit for said switch including a primary relay energized by current over said metallic circuit and responsive to rapid interruptions thereof, primary driving mechanism responsive to said primary relay operations, quick-act ing release and secondary relays each having an energizing circuit periodically closed through contacts of said primary relay While operating, a second energizing circuit of comparatively low current value and continuous flow, for each of said release and,

secondary relays and means for closing and holding it closed during the period of said interruptions'of their first said circuits, whereby said relays maintain their armatures attracted, said secondary relay ,being adapted to retract its armature upon cessation of said primary relay operations to effect a secondary circuit changefor said switch, and release means controlled by said release relay.

10.. A telephone system, including subz scribers metallic telephonelines, automatic switches formaking connection between said lines, a primary relay responsive to rapid variations of current in the line of a calling "SllbSCI'lbGI, a secondary' qu ckacting relay having the continuity of its circuit broken responsive to the rapid operations of said primary relay,and a low current valuemaintaining circuit for said secondary relay, said maintaining circuit being continuous and preventing the deenergization of said secondary relay during the period of operations of said primary relay.

1 1 A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsiveto rapid variations of current in the line of a. calling subscriber, a secondary quick-acting relay having two circuits, one of said circuits being of high current value and broken by the rapid operations of said primary relay, and the other circuit being of low current value and of continuous flow during said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, a secondary quick-acting relay having two circuits, one of low resistance and the other of high resistance, the low resistance circuit being broken by the rapidfoperations of said primary relay, and the high resistance circuit being of continuous flow during the period of said operations, so that said secondary relay is not deenergized until after the primary relay has operated.

13. A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, a secondary quick-acting relay having two .circuits of different current values, one of said circuits being oi. sufiicient value to energize said secondary relay but being broken responsi e to the operations of said primary relay, and the other circuit being of continuous flow during the period of operation of said primary relay and insufiicient value to energize said relay, but suflicient to maintain it energized during said broken periods in the first mentioned circuit.

14. A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsive. to rapid variations of current in the line of a calling subscriber, a secondary 'qieick-acting relay having two energizing circuits, one a vibrat are strength to maintain said secondary relay energized when assisted by said vibrating circuit.

15. A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsive to rapid variations ct current in the line of a calling subscriber, means controlled by said prmary relay for giving said switches a primary movement, a secondary quick-acting relay having a high resistance and a low. resistance path for current, said low resist ance path being interrupted responsive to the operations oi. said primary relay, but said high resistance path having current of continuous how for maintaining said secondary relay energized during the period of said interruptions, and means operative when said secondary relay is deiinergized for giving said switches a secondary movement.

16. A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, aquick-acting release relay having, the continuity of a low resistance circuit thereof broken resliionsive to the rapid operations of said primary relay, and a high resistance maintaining circuit for said re lease relay, said n'ia'inta-ining, circuit being of continuous flow and preventing the deenergization of said release relay during the operations of said primary relay. 17. A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, a quick-acting release relay having two circuits, one of said circuits being of low resistance and broken by the rapid operations of said primary relay, and the other circuit being of high resistance and of continuous flow during the period of said operations, so that said release relay is maintained energized during said period, and a release circuit for said switch controlled by said release relay.

18. A telephone system, including subscribers metallic telephone lines, automatic switches for making connection between said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, aIquick-acting release relay having two circuits of difierent current values,

one of said circuits being of suilicient value to energize said release relay but being broken responsive to the operations of said primary relay, and the other circuit being of continuous flow but of insufficient value to energize said relay, but sufficient to maintain it energized during said broken periods in the first mentioned circuit, and a, release circuit for said switch controlled by said release relay.

19. A telephone system, including subscribers metallic telephonelines, automatic switches for making connection between said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, a quick-acting release relay having two circuits, one a vibrating circuit responsive to the ope 'ations oisaid primary relay, and the other a continuous flow circuit, said continuous circuit being only of sufficient strength to maintain said release relay energized when assisted by said vi,- brating circuit, and a release circuit for said 3 switch controlled by said release relay.

20. A telephone system including an automatit switch, a metallic control circuit for said switch including a primary relay energized by current over said metallic circuit 35 and responsive to rapid interruptions thereof, a quick acting release relay for said switch, means for closing an energizing circuit for said release relay, said circuit being rapidly interrupted responsive to said pris mary relay operations, a second energizing circuit of comparatively low current value and continuous flow for said release relay, and means for closing it and he ling it closed during the period of said interruptions of its first circuit so as to maintain the armature of said release rclay attracted, and operating and release means for said switch controlled by said primary and release relays. 106

21. A telephone system including an automatic switch, a metallic control circuit for said switch including a primary relay energized by current over said metallic circuit and responsive to rapid interruptions thereof, a release relay, means for closing an cnergizing circuit for said release relay, said release relay having its said energizing circuit rapidly interrupted responsive to said primary relay operations, a second energiz- 110 inn circuit of comparatively low current value and continuous flow for said release relay, and means for closing it and holding it closed duringthe period of said inter ruptions of its first closed circuit whereby its armature is maintained attracted during such interruptions, operating, means for said switch responsive to said primary relay operations, release means for said switch rendered ineffective while said release relay has its armature attracted, and means for causing a prolonged interruption of said metallic circuit whereby said primary and release relays are restored and said release means rendered effective.

22. A telephone system comprising a mctallic circuit telephone line, an automatic switch associated therewith, a primary relay energized by current over said line and responsive to rapid interruptions, ct lac its high current value circuit, and operating and release means for said switch controlled by said tively.

23 A telephone system including an automatic switch, a metallic control circuit tor said switch including-a primary relay energized by current over said circuit and re sponsive to rapid interruptions thereof, primary driving mechanism responsive to said primary relay operations, release and secondary relays, energizing circuits for said last two relays periodically closed responsive to said primary relay operations, a second energizing circuit of comparatively low current value and continuous flow for each of said release and secondary relays and means for closing and holding closed during the period. of saidinterruptions of their first said circuits, whereby said relays maintain their armatures attracted, said secondary relay being adapted to retract its armature upon cessation of said primary relay operations to efiect a secondary circuit change for said switch, means whereby a prolonged. interruption of said control circuit causes the deenergization of said primary and release rclaysto cause the release of said switch.

l he. trolcircuit forautomaticswitches com rising a primary'or impulse relay, a second relay, an energizing circuit for said second relayresponsive to said primary relay whereby saidsecond relay attracts its armature, means for rapidly interrupting the circuit of said primary relay whereby it interrupts said energizing circuit of the second relay accordmgly, a second energiz- 111g circuit of continuous flow for sa1d-secfond relay of itself not suflicient to holdthe armature thereof attracted, means for closing thissecond circuit and holding. it closed during the period of interruptions of the first said circuit thereof whereby the armature of said second relay is maintained attracted during said interruptions, and cir cuits controlled by each of said relays respectively.

25. A Y control circi'iit for I/ automatic -switches comprisingila primarypr impulse relay, a second relay," a high current'value energizing circuit for said second relay responsive to said primary relay whereby said second relay attracts its armature, means for rapidly interrupting the circuit of said primary relay wherebyit interrupts saidenergizmg circuit of said second relay etc-- primary and release relays respec-' cordingly, a low current-value energizing circuit of continuous flow tor said second relay of itself not sul'licient to hold the annature thereof attracted, means for closing this low current-value circuit and holding it closed during the period of interruptions of the high current-value circuit whereby the armature of said second relay is maintained attracted during said mterruptions, and circuits controlled by each of 'said relays respectively.

V 26. A telephone system including subscribers telephone lines. automatic switches of the two-motion type for completing conneetion between said lines, a primary relay responsive to rapid variations of current in the line of a calling subscriber, a secondary relay provided with two circuits one of low resistance and the other of high resistance, the low resistance circuit being broken by the rapid operations of the said primary relay and the l'iigh resistance circuit being of continuous flow during the period of said operations, means controlled by the operations of said primary relay for controlling one of the motions of said switches, and

means controlled by the said secondary rerent path being interrupted by the oper-- ations of the said primary relay and the high current path being of continuous flow during the period 0t said operations of the primary relay, means controlled by the said primary relay to control one motion of said switch and automatic means controlled by the secondary relay for controlling the second operation of said switch.

In a telephone system a calling subscribers line, an automatic switch accessible to said calling subscribers line, said automatic-switch being of the two-motion type and provided with means for operating the said switch in one direction to elect a group of trunk lines and means for oppi'ating the said switch in another direet""'n to automatically select a trunk line in the elected group, a primary relay responsive to current variations in the calling subscribers line for controlling the said first motion and a secondary relay for cent-sell ng the second motion of said switch the said secondary relay being provided with two circuits, one of low resistance and the other of high resistance, the low esistance rcuit beinn' memes broken by the rapid operations of said primary relay and the high resistance circuit being of continuous flow during the period of said operations of the said primary relay.

29. A telephone system comprising a pri niary relay an energizing circuit therefor, an automatic switch, secondary and release relays, each of said last two relays having high and low current-value energizing cir cuits, the low currentwalue circuits being of continuous flow and not sufiicient ,by themselves to hold the a'rmatures of the relays attracted, means responsive to rapid operations of the primary relay to render the two said circuits of, each relay eflective so as to maintain their-armatures attracted during the period of operations of the primary relay, to operate said switch.

Signed by me at. Chicago, county of Cook, andState ofIllinois, in the presence of two Witnesses.

CHARLES s. WINSTON. Witnesses M. R. Roonrom), G. E; MUELLER.

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