US1318004A - Automatic telephone system. - Google Patents

Description

8. D. WILLIS.

AUTOMATIC TELEPHONE SYSTEM- APPLICATION mm sgrT. l9. l9!!- Patnted Oct. 7,1919.

4 SHEETS-SHEET l.

v v V fnuezz zuf Bernard H. Wills.

B. D. WILLIS. AUTOMATIC TELEPHONE SYSTEM.

- APPLICATION man SEPT. 15, 1911. 1 18,004. Patented Out. 7,1919.

4 sums-snzzr 2 Bernbrdfl 74/1755;

' 1B. 0. wl usfj' "AUTOMATIC uamoursysr-m- Arrucmon man SEPT us m:

1,318,004. -gmmed 0015x1919.

4 SHEE S-SHEET 4.

, a 1 Barnard ZZZ 3.171115.

' and a resident .of Chicago, county of Cook,

rammed? osmicn.

D. \YILLIS, OF CHICAGO, ILLINOIS, ASSIGNGR Ti) AUTOMATIC ELECTRIG m cca Specification of Letters Patent.

COMPANY, OF CHICAGO, ILLINOES, A CORFQEATIQN F ILLINOI",

' AUTOMATiC TE'LEJPHUNE SYSTEM.

Patented @ch '7, ism.

Application filed Septemlicr 19, ieiv. Serial No; 192,125.

To 3117mm it may concern.

it known that I, BERNARUD. WILLIS, a citizen of the-United States of America,

and State, of Illinois, have invented certain new and useful Improven'ients in- Automatic Telephone Systems, of which the followmg is a specification.

My. invention relates to automatic telephone systems, and involves a number of separate features. many of which are applicalole to automatic systems in general, but which are especially valuable in a particular type of 1 system which I term a mixed service s stem. The distin uishing characteristics 0 such systems toget e2? with the improvementsprovided by my invention, their fuctions and operation,- will-lie described fully hereinafter, reference being had to the accompanying drawings; 7

In the drawings, Figure 1 is a schematic diagram or trunking layout of a typical mixed service system; Figs. 2-, 3 and l are circuit drawings of the essential features of the system shown. ill-Fig. 1;-while Fig. 5

is a detail of a portion of the ringing equipment. 1 y e Reierrmg to-Flg. 1, an automatic exchange such as the one shown. within the rectangle and indicated by the reference character suitable for a small town of perhaps thousand inhabitants, which may be the center of a well populated rural community. YVithin the town and Within a limited radius outside there maybe a number of privatij or'individuallines, such as the line 2, and'a number of four party lines,

such the line 1. Personslivingat re moter points are not. usually given such, a high qual ty OfSBI'VlCG, bem-ggcnerally connectcd in larger numbers'ou so called farmer lines or rural lines. Two such lines as this are th e eight party lines 3 and While only a fe w linesare shown it \willhe' understood that there will be many more radiating in; all directions-fron'l the exchange X as a. common center. j

still greater distances there may be other small centers of population, each with its system of telephone lines diverging from a central. exchange; and there will inevitahl y ger, centers of population or cities angle of telephonic communication. The smaller towns may be supplicd with telephone service by mixed service automatic systems such as the one disclosed herein, or they may have small manual exchanges. Either large multiple manual switch boards, or moder full automatic systems may he used in tl e cities, depending upon the stage of development that has been reached bf, the company operating in tlie particular community. Whatever the char actor of the equipment used, these other ere changes may be connected with the exchange X by means of trunk lines, two or which, extending to two different exchanges, are shown in the drawing. There may be many more exchanges than the two shown, and a plurality of trunk lines extending to each, but since the trunks may all be included in two classes, manual and automatic, thetwo shown will he suflicient for purposes of illus' tration. Thus the trunk line 5 is one of a group of trunks connecting the exchange X with the small manual exchange Y, while the trunk line 6 is one of a group which extends to the large automatic exchange Z. All lines entering the exchange whether "individual lines, party lines, or trunk lines, terminate in individual line switches or trunk selectors, These switches are indicated in the drawing by reference characters C to C", inclusive. The line switches have common access to' a group of trunk lines extending to first selector switches, 'thr which are the], selectors E: E and have the well known function 005' extenc in calling lines to idle ones of these selectors "The banks of the selector-sure all multipled together and form terminals of trunk lines extendingto connector switches which have access tocalled lines. .Thcconnectors are divided into two groups, whether the numher of lines in the system exceeds the capacity of asingle. group of connectors Thus the connectors F and F ar included in one group, while connectors F and F are included in the second group. The trunk lines terminating in one group of conncctors preferably extend from the first level rangement of these latter is follows: The s trunk.l

upper or tenth level in one or bothof connectorsis reserved for the-groups oi particular level or levels On account of a switching operation neces sary to be. performed at theconnectors on calls to othei automatic exchanges, anitlns switching operation is most "convenient at of trunk lines or a group of trunk occupy the same level with 1nd1-- -However, for con 4 trunk lines terminate in the "ninth level of lines, =certain e .Withone of the oonnecto J an e mentioned that the necessit of provi group offconnectors.

Inorde'r to take care of the eightparty rresponding levels in both gmmps of connectors, designated in the drawing' as the sixth and eighth levels, are multipled together; This is necessary on ac-' count of the selective ringing and it may mg for selectively ringing the substations on the eight party lines is the prime reason, or dividing the connectors into two groups.

e connectors of each group are provided means for selectin any one, of the four standard frequencies of ringing current 'as used. in we syste equipment .siss oeiated 1' groups is adapted.

substation 'a,

The ringing- 9 give thebell at a the other group of connectors is adapted to gs separated by a short interval repeated at longer intervals.

I v methods eight 'stations on a line may be selectively signaled.

understood .that

line 2 partylines such asthe line 1. v

11 any automatic system which contains party lines, means must ordinarily be pro: to signal other For this purtwo of erence characters I and the four ch are indicated by ref tion Wlll l briei' description of the apparatus Wlll be'as'sumed that the manual ringer 13, c0

having-the windings 15 and 16. hook I? is provided with "a locking lever 19- are separated to whl stations are tions A H? ,and H, and a common single motign ringing switch, indicated by reference char- 'acter I. The ring back switches may be accessible to subscribers linesvia the third level of the first selectors as shown.

It is believed that foregoing descr pthe general layout of i0 circuit in tl be given,

after-which t e operation will be explained in detail.

The line shown in Fig. 2 ductors-30 and 31 is an the substations A -to inclusive, nccte-d in bridge thereof in the usual manhese eight substations only subis shown complete, the other seven ply by a ringer and condenser bridge across the line., The substation A is similar to the substation shown in the application of John Erickson, Serial N o. ed November 10, 1916, except that 1: e circuits are modified for use in a common battery system. It comprises essentially the receiver 10, transmitter'll, switch hook 12, eiiseiuli and induction coil he switch which 13 adapted to hold th an intermediate is removed. III

e switch hook in the intermediate position "of position when the receiver the switch hook contact springs 20 and 21 termine whether or not the line is in. use.

e line is idle thelocking lever 19 is renectingthe' transinit terll across the line feature of the substation is fully disclosed in the application and shunt springs 17 are shown herein.

be similar to the one the patent to Dicker No. 29,654 e ringers at the different sub- This calling device may disclosed in Of 1910.

frequencies of ringing current, there bein two ringers which are adapted to respond to each frequency. Thus tl gers at substations A and A respond "to. the 16 cycle ringing current while th and current, etc. e subscribers'at substation 1 and. A however, only respond when a while the subrespond -s1gnals.' the exchange the line conductors 30 terminate in the individual line of Erickson tuned to respondto different I I e ringers at substa- A respond to 33 cycle ringing misses switch C; This line switch may be of the general type diselosed in the British patent to James No. 26,3 1 of 1966; heing,hoWever, of the particular pe shown in ll. S. Letters Patent No. 1.015.690, granted January 19, L912, to ll'ranl: h ewt'orth. .ilhrougxh the mediiun of line in 1 G the po ty line shown is given 'acc a plurality of selector switches as h ready been explained.

The line switch similar line swi fies are controlled in their trunk selecting; operations by means of a master switch D. The master switch l) is of the general type of master switch disclosed in the above mentioned British patent to dairies lle. 261,301. of 190th being. however,

more nearly 0 the particular type disclosed in the British pa nt to lrlartin #1419 of 1910. is well lrnown the function of the master switch is to nn-iintain the plungers of all the idle lino switches which it controls in position before the terminals of an idle trunk line. I

one of the trunk lines to which the line switch C has' access is shown in the drawing extended to the first selector E which may be of the general type of selector switch disclosed in U. S. Letters Patent No. 815,321,

06, to Keith, Erickson granted iii larch a side switch and private and Erickson,

magnet are omitted, however, and the cir cults ere modified in accordance with the two wire system of control. The operation of the line switch C and the selector switch E will he described during the process of explaining the establishment of connections.

At the right of '2 three sets of bank contacts, one in each of three levels, are

shown ins-being accessible to the Wipers of' the selector E. From the first: level contact set comprising conductors 95, 96 and 97 extend to a connector (not shown) in the first connector group of theexohange. The second level contact sel comprising hank contacts 86, 87

and 88 the terinina-lof a trunk line comprism ""comtiuctors 932 93 and 9% which" extends to the connector (Fig. 0) in the second connector group. A third trunk line comprising the conductors 98, 99 and 100 extends from the third level contact set machine Q may he magnet H2 and wipers H2 and Q and a plurality of bank contacts 83, 8% and 85,

' the automatic .exchang e Z.

conductors for each'ol these trunk hues, two;

quency selecting ringing equipment Ill. The busy signaling andis of the usual type found in other well known automatic telephone systems, The.

freouenev selectino switch S is individual to 1 W o the connector and cou'iprises e stepping wh ch switch S, end intermittent common to the exchange are adapted to be operated for the purpose oi. selecting the ringing cunent' generator required to signal a desired subscriber.- The ringing equipment IR- is common to the sec ond group of connectors. As shownherein it consists essentially of a relay 150 con trolled by a. two segment interrupter,which adapted- When energized to connect the.

generators AC to AC, inclusive. simultaneously to the four generator leads extending to the frequency selecting switches associ-..

ated with connectors of the second group, In the deenergized position of the relay 150 these four generator leads are connected. to the positive terminal of a booster battery...

In Fig. 5 there is shown at modification of.

the ringing equipment 'IR which to'be used in connection with the first group of connecto It Will be seen that the only dii'ierence between the two sets of ringing equipment is in the constriution of the. in} .terrupters employed. T he interrupter shown inl ign has but a single live segment while the other intcrrupterhas two live segments, thus providing evidently for the one and two hell ringin Atthe right of there is shown a fragmentary portion of the bank of corn nector Fi The lower sets of banks are line contacts in the seventh, eighth, ninth and spending levels. There is nothing new in the b-enk wiring except the wiring of the private bank contacts on the trunking levels. Considering firstthe tenth level in which the groups of automatictrunlis are termi hated it has been assumed arbitrarily that there are three groups of trunks withthree trunks in each of the first two groups and four trunks in the last. Each group qf trunks extends to 'a dilfcrent a'utoinatic exchange, the last group including thetrunk comprising normal conductors 200 to 203, inclusive, being the group whichextends to illiere are four L2G tenth levels while the upper-sets of contacts are private or test contacts in the cor-re:

line conductors and two private or test condoctors. lhe division of the trunk lines into groups is deterniined by the inclusion of i a resistance in the second test conr luctonof the last trunk of each 'n'roup. This isclearly shown in the drawing and the function of g the resistance will he explained 'lully here?v ll G..\Vl1'1l1 Q"Uf the ninth level in.

after. which terminate thegroups of trunk line extending to manual exchanges is' somewhat beingfurther 1 1n mechanical constr itrion shown in the 'iaten't/to Keith, l lricksonand .IKZOdlfiGCl, however, inorder different. Each of these trunk lines hasonl a group except The wiring of the remaining levels is standard, the second test contact of each contact set being left dead. 1 he normal conductors 200 to 203, inelusive,

extend to and terminate in a re- M. This repeater comprises essentially a repeating coil R and the relays 225 to 229, inclusive, whose functions and operation will be described. ductor trunk line 6 extends to the distant automatic-exchange Z where it terminates in the repeating coil R repeater M. The repeater M except for a slight circuit change necessary exchange to the main exchange are extended by way of conductors which terminate in an individual line switch. Calls in the reverse direction which originate at the main exchange are extended to the trunk line shown by way of conductors 262, 263 and 261 which may terminate in a selector level or in some level of a group of rotary connectors. These completed at the mixed service exchange by wayr'f conductors 241 and 242 Which-terminate inthe line switch C (Fig. 1

The ring back swfich H" is a vertical and rotary directively .cont 'olled switch similar l to the switch Erickson, ,o."815,176, the circuits being v to adapt the s W-itch to the two wire system of control and modified to enable the switch to perform its function of a ring back apparatus. .The switch H" has bht two dicated by reference characters 330 and 331 and only the live lower levels of line contacts are used. The private or @test contacts are omitted entirely.

he ringing switch. I is a single motion rotary switch and may be of any suitable construction; it being necessary only to provide connections for, the wipers which permit their continuous forward moven'lent as shown in the' patent to Lamb N 0. 1,193,160, granted August 1, 1916. In its preferred form and as show n diagran'imatically herein it com manual exchanges on associated with the April 13, 1915. Calls and comprisesv the inmates in the usual the call the switch hook wipers inother, thereby bridging receiver 10 permitted to rise to its final "tact springs 21,22 and 23 gagement and the transmitter By tl t riple construction and are continuously in clusive, may be the same generators which are shown in Fig. 3. The wiring of so much of the bank of the ring back switch H as is in use and the wiring of the bank of ringing switch I is shown complete and will be explained in the description of the operation.

It has not been thought necessary to show any of the trun lines which extend to account of the fact that the equipment associated with these trunk lines is old and is in part shown in Fig. 2' of the drawings. onsidering for example the trunk line which is accessible to connector F by way of the seventh set of contacts in the. ninth level, the normal eonductors 207, 208 and 209 extend to and terminate in an individual line switch indicated in Fig. 1 by the reference character C This line switch is similar in all respects to the line switch C", the circuits of which are shown in detail in Fig. 2. It will be seen then that in so far as the exchange equipment is concerned these trunk lines are similar to the party line shown in Fig. 2 conductors 30 and 31. At the manual exchange each trunk line terdrop, jack, and cut oil relay. Manual equipment of this kind is old and well known and need-not be illustrated.

-Having described briefly the apparatus involved in the system its operation will now be considered. The operation of the on local connections will first phone number of the latter substation being i 2842. hen the calling subscriber at sub station Aremoves his receiver to initiate 12 is permitted to rise about half way where it is held by the lockinglever 19. I his position ot the switch hook contact springs 20 and 21 .are

separated while contact springs 21 and 22 are brought into engagement with each the condenser 14, and secondary winding 15 across the twoconductors of the line. The calling subscriber will now place the receiver to his ear in order to determine whether ornot the line is in use. i No conversation being hea'rd the locking lever 19 is now released by hand, whereupon the switch book 12 is position. Conare now in en- 11 and'primary .coil are bridged line in parallel with the receiver. 1e closure of the transmitter bridge a winding 16 of the induction across the flow of current is established in the wind ing of the line relay 32 of line switch Ctas follows: ground at G inner set of cut oii' springs, line conductor 31, primary'winding 16utransmitter 11, contact springs 23, 22

I and 21, line conductor 30, outside set of cut mature the line relay 3-2 oii springs and thc windings of the line reand from the grounded pole of battery.

By the engagement of bank springs L0 and 4-3, respectively, with contacts M and d7, the line conductors 30 and 31 are extended by way oi normally closed contacts of the switching relay 58 to the impedance coil 51 and the line relay 50 of the selector E. The line relay 50 is accordingl energized over the closed line circuit, inc uding subs station A, and upon attracting its armature closes a circuit for the slow'acting release relay Upon energizing-relay 5'2 corn-r plctes a llOl(l11l I circuit tor the line switch (I which may be traced as follows: ground working contact of armature 60. and the. said armature, conductor 61, contact 45, bank spring 11, holding winding 35, and teri'ninal as to battery. The line relay is slmv'acting in order that it may retain its armature in operated position until after the above traced circuit has been completed. A branch of the holding, circuit extends by way of conductor 37 to multiple test contacts in the banks of the connector switches which have access to the line of substation A,

Where by a ground potential upon these test contacts the lineis made busy. By the engagement of bank spring :2 with Contact as, the master switch'l) is operated in the usual manner to advance the plungers of all the remaining idle line switches into position before thetcrminals of the next idle trunk line. Q

The foregoing trunk selecting operations have occurred automatically in response to the removal of the receiver, The calling subscriber will now operate his calling de-- vice in accordance with the first digit in the desired number, or the digit 2, thereby twice separating the impulsemnings 18 and producing two interruptions in the circuit of the line relay 50. In response to these interruptions of its, circuit, the line relay 5 1) is decnergized a couple oftirnes and at each decnergization transmits an impulse from ground G through the low resistance slow acting relay and the vertical magnet let to at, inclu- 80, 81 and 82 into engagement set of bank contacts in the second level. Near the end of its stroke the rotary magnet 56 in series, slow acting relay 52 remaining in operated position notwithstanding the interruptions in its circuit produced by the nion'i'entary deene'rgizations of theiline relay. The vertical magnet 56 responds to the impulsestransmitted by the line relay and operates to raise the switch shaft and the wipers 80, 81 and 82 until the latter stand ope posite: the second horizontal level of bank The relay 53 is energized in seand being slow contacts. ries with the vertical magnet,

acting, retains its arinatures in operated position during the series of impulses. At

the first upward movement of the shaft the 0H normalsprings 59 are closed, thereby completing an initial energizing circuit for Y the stepping relay which extends from the. grounded conductor 61 by way ,of-the lower armature of relay' 53, the ofl normal springs 59, and the winding of the said relay 5a tobattery. Upon energiz1ng,',the relay 54; looks itself independent of relay 53 at its upper armature and at its lower armature prepares a circuit for the rotary magnet 55 which is held open duringthe vertical movement lay 53. In addition to those described the slow acting relay 53 has a new function, in that at its upper armature it connects the lower low resistance winding of impedance coil 51 in parallel with the upper winding. The lower winding of relay 51 is prefeu' ably non'inductive and its inclusion in the line reduces the resistance and impedance oi the. control circuit '1icluding .theline relay 50, thereby greatly improving the op eration of the selector switch in response to impulses. On longrural telephone lines slow acting relay 53 denergizes at the end of the. vertical movement of the switch a vcircuit is completed for the rotary magnet 55 extending from the grounded conductor 61, by way of the springs controlled by the lower armature of relay 53, the lower annature of relay 5e and thewinding of the retary magnet 55 to battery. Upon energim ing, the rotary magnet advances the wipers with the first of the switch by the reopens its interrupter contact and thereby hreal's the locking circuit of the stepping relay 54, Upon the deenergization of the stepping relay, the, circuit of the rotary magnet is in turn broken and the rotary" "the circuit of the more, the steppingv relay completes the circuit 0f the rotary magnet as before and the switch wipers are advanced to the second set of contacts. Since the stepping relay 54 and the rotary 'niagnet each interrupt other it-i'vill be'seen that the switch Wipers will continue tobe ad vanced step v wiper 81 engages busy or grounded test contacts, an idle trunk line is reached, assumed to be the test contact 87, the test wiper 81 will nd -no ground potential and the stepping energized; Instead the. switching relay 08 which until now has beeufiiisu, l 105 connectrelay 54 will not be short circuited is energizedover a circuit ,which may 'be traced briefly as follows:

(31, winding of the switching relay 58, interrupter contact of the rotary magnet o'lf normal springs 59, and" the winding-of the stepping relay 54 to battery. Relay 58 is sufficiently high in resistance to render the relay 5+ inoperative. Upon energizing, relay 58 opens a contact in the circuit of the release magnet -57 at its lower armature; at its upper armature shifts the connection of the test wiper 81 from its upper'to its lower terminal; and at.,its two inner arinaturcs disconnects the line conductors and 31 from their connection in the selector E and extends them by way of wipers 80 and 82, hank congrounded conductor tacts 86 and 88, conductors 92 ,and ill, and

' contactsv controlled by relay 1'01 and 102 to fol lows:

the windings of the impedance coil 153 and the line relay 103, respectively, of the con ncctor F. .The line relay 1 03 is accordingly; energized over the calling subscribers loop and closes the usual circuit for the slow acting release relaylOl. 'lhis'lattei' relay, upon energizing, completes a hohlingcircuit for .the selector E and the line switch C"- as ground at G, spring 121 and its resting contact, armature 125) and its working contact, winding 152 of induction coil conductor 93, bank contact 87, n ip -r 81,

- and the upper armature of relay 58 and its working contact to junction point 02-, where the circuit divides, one branch extending by way of the. previously traced circuit through relays 58 and 54 to battery and the other branch oining the conductor 61 over which it supplies holding gi'ound'to the line switch C.

The calling subscriber may now operate his calling device in. :u-cordance with the second digit, 8 of the called number,thereby producing a series of interruptions in; the circuit of the line relay 103. Tu response to these intcrruptit ins of its circuit the line-relay 103 is dei nergized a corresponding number of lllllvfi'tlml at each deiinegization transmits an impulse to the vertical magnet 11.0 over the following path: ground atG, wiper 142 of the frequency selector S, conductor by .step long as the test,

l/Vhenfa test contact associated with 'ofg impulses as usual.

. of the switch the sive, stand opposite the eighth horizontal The relay 105 is level of bank contacts. energized iirsei-ies with the vertical magnet and retains its armature during the serles the right hand winding of the impedance coil 153 in multiple with the left hand winding in order to reduce the resistance and impedance of the control circuit of the line relay 103, this being the same'operat-ion that was described in the case of the selector E. I addition then-clay 105 closes a circuit for the private nagnet 108 as follows: ground at (i, armature 131, spring 132, and the winding of the private magnet 108 to battci'v.

lllilgllttdtlifi' are deenergized, the latter pertormingits well known-function of advancing the side switch wipers 113, 111 and 115 to their second position.

The third digit 1 of the desired number may now be called in the same manner as thepmccding digits. 5 A series of four interruptions'is now produced in the circuit of the line relay 103 and the said relay accordingl y is again dei nergized momentarily a number of times. Now-however, the side switch wiper 111 having been advanced to its second.position,.impulsesare trai'isniitted to the rotary magnet: 111 as follows: ground at G", wiper 142 of the frequency selecting switch S. conductor 154, armature 126 and its resting contact, armature 128 and its working contact, winding of the relay 105. resting contact of spring 131 spring, winding of the rotary niagiieelll, and the side switch wiper 111 in second position to battery. In response to impulses over ,the above circuit the rotary, magnet is operated to rotate the connectmr shaft until the wipers 1.70 to 173, inclusive, arrive at the fourth set of contacts in' the eighth level. 'lhe slow acting relay 105' is energized as -before. and performs the crations including the closurelo't the circuit n lignet 108. At theend of of the privatc the I'Oitlt'lUiP't) .ie switch the relay 105 and the private magnetdei nergize and the side tacts tnt 1e eighth level At its upper arma Xt. the end of the vertical movement relay 105 and the private same ops assumed- -that the called and the said to third position,- therefore, a i uit minate in the individual line switch C 1) in the. serhe manner that thenorniel. eon duotorsiBT, 38 and terminate in the in (lividuel line switch C (Fig. 22 When thesides iteh, the connector is advanced completeil for, the out. of? or holrlingwinning; of the called line SWllZCil C traced follows: ground while and Hie side switch Wiper in .hird posifion, lower private wiper 171, (.OE'KiUCiZOL ill), ELli-(l the out be Wilding of line switch G to battery. The out of? armature of i e Cilllflll line ewitchvis thereupon attracted to clear the called line of its normal lJt ery' and ground connections; Ground G" also tends to the multiples or" the te'si; cont; with which the Wiper 171 in erigag omen z and the ealleql iine'is thus made lousy remaining connectors in the group.

The Wipers of the connector having been advanced into engagemeni with the set bank contacts associated with the-desired which may he celled line the next operation is esfialr,

lishment of 'a signaling circuit for ringing the hell zit/the desired station on the line. In order to accomplish this the frequency selectingswitch S must be operated. The calling subscriber accordingly will now operate his calling device for the final digit 2 of the called number with the resell; lint two interruptions ere producecl in the circuit of thelinereley103. The en equehijde'nergizetions of the line relax; new pi'lmhiee two current impulses in the cir-enit .oi the step ping magne 11 2 of the fre'queney selector S.

This .eireuii; may be traced. as follows:;

ground at G, wiper 1 92, eonuotor 15 i, allllllllllfl 128 end itsresting contact, armeture 128 and its Working Contact, Winding of relay 105 Winding of the stepping; magnet LL? and the side switch Wiper 114- in thir-zi posit-ioii to hettery In response to the two impuieeereoeired over the illhf'bve circuit the "Q. gne 1- 112 is operaied to advance the erslBeml 1&3 two seeps, whereby they are brought into engagement with the thirdcont acs ietheir respeoeive hanks. At the first moyement of the wiper M2 ground G is aliseonnectel from comiuetor 15 Since the relay 105 energized in series with the magnet l ii however, the armature of relay. is not ilieoonnecleil from ground, but the movement of the Wiper 1.42 has effect on the operation for armetare 1:26 is temporarily supplied with ground from by l,"ll'lili3lll"fi 131, 132 and its workingrontwst. Relay 105 also closes the circuit of the private? n' egnel; 108 as usual eni me private magnet is eherei'ore energlide iclurihg *Jhe operation of the frequency; ee line wip '5 H2 and L73. At the encl of the final series oi" impulses the relay and the private magnet 108 are clenergized'.

' Sta-ion A, norm respond to the 33 172 and 173 from/ rupter H 2 i l) gene or lead. o roqueney eommior mz'iich 5i, eomluaor I i nornml con $2.. he armature, immature l is, 1 ing eonzact upper Winding of the cut off we My 107, Tillie. swlhzh w'per 13, in third position, to battery. By the operation of i'he ringing iniierrupter iii; ringing: cw'reni if? :21 8 the generator All is oroje .ted intermitl line to signal the 3 trueiion of the ina rapidly suemipiilses i by e r period. oi? e eral times the length of zhe interval hem impuises. When, howeve, the ringing current is cut off from fie line by the (leenerg izetion of relay the generator lezul sting Contact oi .2111 1 eonneefied to the positive pole of he hoes-rezhettery shown just ehove lo the right 0 '1 lay 150. The ring oil? r ay 107 is so cljustedihzi't it is not fe lay 'ihe rin, current While the re tion is on the hook. When he .3 removed, however. the relay m2, is energizezi either by current {T0311 the mliin battery in series with the generator thee in use or current from the main battery in series with the hoos'zer battery.

The ringer at subst rioh A. is tuiie to cycle and since the sub ah th is etetion has been nstructed m scriberi answer when a two oe'l ring received he will 110W remove his enol'immedietely release the Switch hook to its final or talking position. The ring out off relay 10? is thereupon energizecl oi once irrespective of the posibion oil: the ringing interrupter Til? and establishes a 1 remit for lie. as folio ref grout '5 i riormei spriiig 1%? -21 j. the 1 meet engaged thereby (broegghi'into engagement at he first if? Ward movement of the switch shaft), time 139 and its working contact enol' die lower winding of i-he ring out releyi'f)? to battery. as a furher result of its en moan relay 10'? disconnects the line uyper Winding er from the geiiereior lead M4.- enci e-ormee them instead to the upper and lower i182. taikiiip eondnetori-i, respeeriveiy. T1'3KASl'2x1l1-- ter ourreira for ihe called substation now supplied as follows: ground G 01% norsaid armature,

therewith. and the mal spring 147 and the contact engaged thereby, armature 139 and its working contact, the lower winding of the answering bridge relay 102, resting contact of spring 119 and the said spring, working contact of armature 138 and the said armature, arma'; ture 141 and its resting contact, Wiper 173, normal conductor 212 to ant through the substation A 172, resting contact of armature 140.

contact, spring 117 and its resting contact, upper winding of the answering bridge re lay 102, and the winding 151 of induction coil P to battery. The current 'flow over the its armatures 122 and 124 reverses the incoming line conductors 92 and 94 as regards their connection to the windings of impedance coil 153 and the line relay 103. addition, at theworking contact of spring 125, controlled by armature 124.,the upper condenser is connected to complete the talking circuit. lhe reversal of the line conductors described is useful in certain cases for controlling a meter or coin collecting device associated with the calling line, but since there is nothing new in this operation no measured service devices have been shown.

he required connection has now been established. Talking current is supplied to the transmitter at the called substation through the windings of relay 102 as already explained; while talking current for-the transmitter at the calling substation 1s 1 the windings of relay 103 supplied througl The path for the and impedance coil 153.

voice currents through the several switches, has been drawn in heauy'lmcs and will be readily understood without further explanation.

When the conversation is finished both subscribers will replace their receivers. By the replacement of the receiver at substation A the line relay 102- of connector Fa is dcenergized, followed by the deenergization' of the slow acting release relay 104-. A circuit is thereupon established for the re-'v lease magnet 10!) as follows: ground at (i spring 121 and its resting contact, armature 12!) and its resting contact, otl' normal spring H 0 and the contact in engagement winding ot' the release magnet 100 to battery. By the energization of the release magnet the switch shaft and the side normal positi circuit of the the shaft reaches its lowest pos1t1on.- As a further result; of the deenergization of relay 101 the holding circuit extending back to the selector E and the line switch Ctis broken. As a result the switching relay.

- volved in th '58 at the selector E is denergize'd to close a circuit for the release 111 S61 the bank, wh e apparatus -ine connection will have been restored to norma position.

In the foregoing it has been-assumed that' the called line was idle wh usy signal to the calling subscriber. 'In his is done it will foregoing paragraphs,"was in use. Under these circumstances there is a t e lower test contact of ciated with the called line either t e normal conductor-210 bank multiple. when the slow acting relay gized at the end of the second series of impulses directed to the connector F that the private magnet 108 is'not-denergized as is the case when the called lineis idle but is held ing path: grounded busy test contact, private or test wiper 171, side switch :wiper 115 in second position, contact trolled by armature 135 of test 'winding of the said test relay, contact springscontrolled by the armature ot'- the rotary n'iagnet 111, resting contact "of spring 132 and the said relay 106,

in second and 173 armatures spring contacts o f substation. A

up by current flow over the followsprings con H g a ground potential upon sis a the side switch wipers are locked and at armature 1,;6'connects'a lead from the busy sigrialing malzhi'nc "Q" to the lower talking conductor. A distlnctlvc signal is thus transn'litted to the calling subscriber vto inform him that,the desired line is for the present inaccessible. As is usual under such ciremnstances,-the calling subscriber will then replace his receiver whereupon the automatic switches arerestored as hereinbefore described.

Alltwo bell-stations are called from the second group of connectors like station A l. 5 The one bell stations, however, are called from the first group of connectors which have associated With them the ringing equipments shown in Fig. 5. Considering station A which We may assume to be a one hell. 0 33 cycle station, the number of this station will be 18-12 and connection may be extended thereto in substantially the same manner as above described; except that the selector E, being operated in accordance with the digit 1 rather than in accordance with the digit 2, selects an idle connector in the first group instead 01 an idle connector in the second group. nector is of course the same as has been alzc ready described and the only other difference occurring in the establishment. of the connection which needs to be mentioned is the substitution of the one hell signal for the two bell signal. This it will be readily understood is accomplished by the use of a single segment 1n the common rmgmg'mterrupi'er as 18 shown clearly in Fig. 5.

There is nothing unusual in the manner of extending connections to straight or four party line stations and consequently no detailed explanation will be given.

Having described the operation of the apparatus in completing local connections I will now explain how connections are ex- ,35 tended from the local or mixed service exchange to a distant automatic exchange as for example the vexchange Z (Fig, 1.). The call number for each of the exchanges to which trunk connections may be extended is 40 determined by the group of connectors from which the trunk lines are accessible and by the location of the first trunk" line in the banks of the connectors in the group It follows therefore that sincethe trunk lines extending to the exchange Z terminate in the last four contact sets in the tenth level of the second group of connectors, the telephone number to he called in order to extend a connection to an idle one of these trunk lines the number 207. For convenience it will be assumed that the subscriber at substation Adesires to obtain connection with some subscriber at the exchange Z, and it will be further assumed that the first three .55 of the trunk lines which extend to the exchange Z are busy. The operation of the line switch Cf and the operationof the first selector E responsive, respectively, to the removal of thereceiver and to the calling .ot' the first digit of the number are the same as was described in the explanation of the establishment of a local connection. Like wise the "operation of the connector F in response to the calling of the digits 0 and 7' is precisely thesame as has already been deare extended by direct metallic The operation of the selected con-- tion;

scribed except of course that it is new heir operated to a different level and to a diffe ent contact set in the selected level. in he case now under consideration, however a: to; the connector operated to establish connection with the first trunk line of the de sired group, if this first trunk line is busy it is necessary to select an idle trunk line of the group, and thereafter a switching operation is performed by which the line conductors connection through to the line conductors of the leoted idle 'runk line. These op actions will. now be described.

ii We assume as before me *ioned first three trunk lines wh terminate spectively in the seventh eighth and ninti': sets of contacts in the tenth l are in there will be a ground potential upon both the upper and lower test contacts of each contact set. It follows therefore that when the connector F is operated to Wipers 170 to 173, inclusive. into engagcin with the seventh set of contact in. the ter level and the slow action scri delinergizes at the end of the final so, .es oi? controlling impulses, a circuit will. be tablished through the test relay 1% and the private magnet 108 as follows: ground on the lower test contact the scvemu contact set in the tenth. level, t-cst wiper 1T1, sine switch wiper in second position. co tact springs controlled by armature .nd ing of test'relay 106, contact spi' con trolled by the armature of the rotar net llh res'ting contact of spring; 132 and the said spring, and the winding; of the i 31* rate magnet to battery. By the establish.

ment of the above circuit the rivate on: net 108 is maintained eneryria- 4. thus ing the side switch wipers in second. The test relay 106 energized in series with the private magnet and upon at tracting its armature 133 COlYlPlQlTQSiL circuit for the rotary magnet 111 as follows: ground on the upper test contact of the seventh. contact set in the tenth level, test wiper 1Y0, armature 1333, contact spring winding of the rotary magnet 111 and the side switch Wiper 11.4: to battery. By the operation of the rotary magnet the connector wipers are advanced one step into engagement with the eighth set of contacts in the tenth level: Near the end of its stroke the armature of the rotary magnet connects ground i to the private magnet and at the same time breaks the energizing circuit of the test lay 106, the test relay accor ingly being energized. the falling back oi? the test relay the circuit or the rota y" magnet is interrupted and the magnet therefore lcenergized. It being assumed that the ii-n1 line terminating in the eighth contact is air-3o busy, the former circuit through the test relay 1% and the private mag e ninth set of contacts.

I sutne 'to beidle.

- follows: ground at and its worlnng"contact and the lower wmd-.

now be reestablished andthe rotary magnet.

will again be energized to advance the c 0n- .nec tor wipers into engagement with the The ninth set of com tacts'being also busy the same operation is again repeated and the. wipers of the connector are advanced into engagement with the tenth set of contacts which we will as- VVhen the rotarymagnet deinergizes for the last time, since there is no ground potential upon the test contact with which the wiper 171 is now in engage ment, the test relay 106 will not again be energized and the private magnet 108 will be permitted to de'e nergize. By this latter operation the side switch vanced inthe'usua l manner to their third position.

By the advance of side switch wipers 115 and 113 to their third positions a circuit is completed for the switching relay 101 as-fol- .lows: groi nd at G side switch wiper 115'- in third position, test wiper 171, conductor .201. contact pointv246, spring 245, conductor 200, resistance 204, test wiper 170, armature 133 and its} resting con tact, oif normal contact-145 (closed only on the tenth level), winding of' relay 101, and the side switch Wipe1n113 to battery, Upon the energization of the switchingrelayrml a' circuit is completed tor'the ring. out oii' relay. 107'. as i G contact spring 121 111g of the relay 107 to battery. Ground at i selector G fis alsoconnccted'by way of contact spring l-21-'an'd armature 120 to conductor in order mguard' against the release of'the I arid the line switch (I -upon the decnifgization of relay 104: which instant later. Relays 101 and 107 being in energized position a direct metallic connec tion has been established from conductors and 94 byway of armatures 116 and118 200,"thereby maintaining connection of relay 101,-armatu res 137 and 138 of relay 107, armatures 140 and 141 of private magnet 108 and line wipers 172 and l73etothe' trunk conductors 202 and 203, respectively.

It follows therefore that the line relay 22 7 of the repeater M which is connected in bridge of conductors 202 and "203 in series with thevbattery will be energized over the calling subs'cribers loop; therebyclosing at its armature 233 an energi-zing circuit for the slow acting relay 226. Relay 226, upon energizingin turn, completes a circuit from ground G which extends by way of-armature 232 and the winding of slow acting. re-

' la 7 225 to battery. Relay 225', upon energizing, has the function of breaking, the connection between conductors 200 and 201 and of connecting ground G? to the conductor cuit of the switching relay 101 of the con nector F? independent of the former ground wipers are adtors 265 and 266 with the result that theli'ne .to operate the dial of his accordance with the digits in. the telephone OCCllI'S an 'pleted. The bell the energizing c1r- -bywayof the lower test wiper 171. As a further result of its energization relay 225 completes a control-circuit extending to'thc distant automatic exchange Z which maybe traced psfollow-s: ground at G,winding oi the has rel: 267, resting contact of armature 2799 and tie Said armature, left hand windings of repeating coil R in parallel. line conductors of trunk line (3 in parallel, right hand windings of repeating coil 'R in parallel, armature 231 and its Working contact, working contact ofv armature 234 and the said armature, and the resistance 247 to battery. The line relay 267 is accordingly energized and couipletes air energizing circuit for the'slow acting relay 268 which relay, upon energizing in turn, connects ground G" by way of its armature 274 to the conductor 263 in order to make the trunk line 6 busy at the exchange Z. As afurther resultof the operation of relay 268 the right hand windings of the repeating coil R are connected at armatures 273 and 275 to the conductors 2.65 and 266 respectively. Since the line relay 267, in addition to closing the circuit of the relay 268,also short circuits the condenser which is connected in series with the two right hand windings of the repeating coil R, a conductive bridge is now closed across the con'ducswitch in which these conductors terminate is operated in the usual manner to selectan idle selector switch.

The calling subscriber may now proceed calling device in number of the subscriber in the automatic exchange Z with whom he deslres' to obtain connection, thereby producing successlve series of interruptions in the circuit ofthe line .relay227 of the repeater M. During each series of interruptions the line relay 227 is deenergized a number of times and thereby interrupts the control. circuit ineluding the line relay 267 of the repeater.1l0

M, this latter relay being likewise de'-nergized intermittently to interrupt the bridge across the conductors 265 and-266. Thus it will be seen that the interruptions produced by the calling device at. the calling substation will be repeated by the line relays 227 and 267. of repeaters M and M'in order to effect, the operation .of a series of. switches in the exchange Z, whereby theconnection" to the line of the called subscriber is comat the called substation is thengrung automatically in the usual lnanner and when the called subscriber responds conversation may be held as desired. There being nothing unusual in the signaling 01* 1:!6

talking circuits no detailed explanationneed be given. i 'j. f When the conversation is finishedboth subscribers will hang' up their receiver.-

When the receiver at substatioh A isre- 113011 placed the line circuit is broken and the line relay 227 at repeater M is accordingly deenergized. The deener'gization of relay 227 opens the control circuit including the line relay 267 of repeater M and .the resulting vfrom conductor 200. By the removal of ground from conductor 200 the energizing circuit of the switching relay 101 of connec tor "F is broken and inasmuch as relay 25 is slow acting this circuit remains open long enough to permit relaylOL to deiinergize. By the retraction of armature 120 of relay 101 ground G? is disconnected from the holding conductor 93 and/is connected instead to'the release magnet 100, thereby causing the relea'seof theconnector F It should be mentioned tl'iatithe connector is released and the side switch Wiper 115 restored to first position before the slow acting relay 225 at the repeater/M has had time to decnergize. By the ren'i'oval' of ground from the holding conductor 93 the selector E and the line switch C are restored to normal in the usual manner.

In calling into a group of trunks on the tenth level, if all the trunks in the group are busy the connector in use will stop on the last trunk anyway, because of the resistance as 204 for instance which is included in series with the private normal conductor associated with thelast trunk, this resistance being high enough to prevent the opcration of the rotary magnet. In such a case the test relay of the connector and the private magnet are maintained energized until the connection is released and the calling subscriber will hear the busy signal when he places the receiver to his ear.

It is understood that the trunk lines connecting the exchange X or mixed service exchange with the automatic exchange Z are two way trunk lines and are adapted to handle connections in either direction.

To provide for handling calls from the 6X" change Z to the exchange X the group of four trunk lines may terminate in a selector level in the former exchange; and considering the particular trunk line number G which is shown in the drawings, the conductors 262, 263 and 264'may terminate in the first set of contacts of the level which is reserved for this purpose. Suppose now that a subscriber in the exchange Z desires to obtain connection with a subscriber in i We assume that the trunk line number 6 is the one with which connection is established the line relay 269 will energize as soonlas the connection is completed and Will in turn complete a circuit for theslow acting relay 270. Relay 270, upon energizing, connects ground G to the conductor 263 in order to maintain the operated selector or selectors in operated position. By the energize tion of relays 269 and 270 a control circuit including the line relay 229 in the repeater M is completed as follows: ground at G, winding of relay 229, resting contact of armature 231 and the said armature, right hand windings of repcatingcoil R in parallel, line conductors of trunk 'line number 6 in parallel, left hand windings of repeating coil B in parallel, armature, 279 and its working contactavoiking contact of armature 277 and the said armature, and the-resistance to bat tery. The closure oi the above control circuit is followed by the encrgization of relays 229 and 228m the repeater M the latter relay being cliective to ground conductors 200 and 20l and thereby render the trunk'line busy to connector switches such as the connector F in the exchange X. Relays 228 and 229 also close a' bridge across the conductors 24.1 and 24-2 tooperate the line switch (7 for the purposeot selecting and connecting with an idle selector switch. N ow when the callingsubscriber in the distant automatic exchange operates the dial of his calling device the interruptions of the line circuit which are produced are repcated by means of line relays 269, and 229, and thereby cause the operation of the selectcd. selector and a connector in the 0X- change X in order to complete the required connection to the desired subscribers line.

Since thc connector switch under these cir-- cumstanccs opcratcscxactiy thesame as was described in thc/cxplanathm of the .cstablishmcnt of a local connection no further details need be given. When the receiver is rcplaccd at the distant exchange Z. the

The I exchangeis being called. No switching.

through operation takes place, however, for

the of]? normal contact 145 is closed when on the tenth' level and an extra digit must be called to operatev the frequency selectlng switch S as when calling a local line. In accordance with the location of the Y exchange trunks in the drawingthe proper digits to 'be called would be the digits 2, 9,14: andone a'dditional digit,

When the operator plugs in to answer the which the operator p the exchange X' and therefore are entitled It may be, however, who are furnished her to rebate the charge. Ordinarily of course all calls from the exchangeX to the manual exchange Y willhave to be-paid and it is the duty of the operator at the latter point to charge all incoming calls from the exchange X to'the proper parties. that certain subscribers telephone service from the exchange X are in reality located about as close to the'exchange Y as they are to to, communicate-with subscribers-in the exchange Y free of charge. In order to notify the operator at the manual exchange when she is being called by an X' exchange subscriber who is entitled to free service, special equipment-is provided comprising a signal ing device K at the exchange X and comprising also an induction coil such-as'the induction will which is associated with each .of the connectors, such as the connector F In-the exchange X the'holdin windings of the line switchesassociate ,with lines whose subscribers are entitled to free calls to the exchangeY are not con:

nected direct to battery but on the contrary line are located near the end ofithe line switch C is disconnectedfrom terminal extend to battery byway of the secondary; winding of the inductioncoil of the signaling device K. Thus if we assume for the sa e of illustration that the party line corn prisin conductors 3O and31 extends in the direction of the exchange Y as shown in the drawing and that the subscribes n'thisline it may be that these subscribers-will ge'Y. To

. 49 and is connected insteadjto terminal 48.

- and conductor F to ..When connected in this 'way if a connection "is extended by means of .the selector E the manual exchange Y a distinctive tone produced by the signaling device K will be transmitted by way of the holding conductors 61 and 93, the Induction preferably the digit 2.

key the relay certain calls tonotify is nothing particularly be en-' the operation is set is preferably connected directly in of the trunk line in order to operate the ring out off relay 107 .and thereby stop the ringing operation. It follows that'immediatclv upon the energization of relay 107 the bat tery supply relay 102 will be energized and .the' left hand winding of the induction coil P will be short circuited.

The operator at the manual exchange,

however, may have a condenser connected in series 'with her head 1 set and normally short circuited through the contacts of a special-listening key. lVith this arrangement the operator is instructed to listen in with her special listening key on all calls incomin WVhen the special listening key is thrown the condenser will becut in series with the operators head set and the battery supply rela 102 at the exchange X be eenergized. Under these conditions the operator will be able to'hear the tone if it is present on the line and will, rebate the charge for the call accordingly. Since there difficult in the design of the operators cord circuit it has not been thought necessary to illustrate the same and any suitable arrangement may be used instead of the one herein proposed. Attention will now be directed to the ring back equipment through the medium of" which the party line subscriber is enabled to signal another subscriber on his own line. This equipment comprises a plurality of ring backswitches one of which is the switch H (-Fig; 4) and the common rotary ringing switch I. In general the method of handling reverting calls in my present system is similar to the method disclosed in the patent to .Hovland No. 1,158,221., wherein there is described a revertin call or ring back system in which the calling subscriber by manipulating his dial in accordance with the proper digits operates a ring backswitch at the exchange to select the two frequencies of ringing current which corresponds to the calling and called substations.;- The calling subscriber then hangs up his rejieiver, whereupon mechanism in the'ring back switch is operated to effect the application of the selected ringing currents to the calling line alternately. The called subscriber is' thussigna led as usual;.while the calling-subscriber is also signaled so that he may know that proceeding properly and also that he may know by'the-cessation of the ringing of the response of. the called party. Owing -to the fact that in'the present system the selective ringing is accomplished by a combination of the one and two bell principle, ratherAthan on the harmonic principle alone as in the Hovland system, the apparatus and circuits employed are radically different although the general from the, exchange X.

will therefore tin * swi h. as

"- horizontal principle of operation is substantially the same. 4

Each party line subscriber is supplied with a list of special numbers which are to be used in calling the other parties on his own line. These numbers of course conform to the wiring of the banks of the ring hack switches, which it may he stated is largely an arbitrary arrange:uent although considerable care has heentaken to devise as simple scheme possible. The bank wiring of one of the ring back the wiring of the ringing switch I shown complete in here: which correspond to the wiriirg shown are given in the table below.

Calling; a aziun. Caller Motion. Nmnbcr.

it caliing .21 or A? A 31 a an; A" A A [t 317 A A. 31.9 A. A 310 A A 321 A A 823 [a A 3-27 A. 329 $1. 320 u A A. 333 A 335 A 33? A" 339 f 330 it: an A 343 A 345 A 34:7 A 3&9 is c are ii 351 A, f: t-a A 355 A A 357 The operation of the apparatus in a rell will now he explained, it being this purpose thatthesuhscriher A (Fig. desires to call the su'oscimer at suhstation A". By referring to the tahic it. will he seeirthatithe number to he called in this case is the number Upon the removal of the receiver at Sill!- station It the line switch {1* is operated in the manner already explained to extend. the line comluctors and 31 to the trunk conductor rrl ch terminate in an idle selector zed to he the selector id, in to the calling oi he first digit 3 her the first selector operated. .iaft in the usual manner until 5 so, 81 and arrive at the third icvel of bank contacts, after which the wipe;

switches and Fig. "l and the special call hum-- the wipers are automatically rotated to pick out an idle set of contacts in the Selected level, Assuming that the contact setcomprising bank contacts 89, 90, and 91 is the set selected, upon the energization of the switching relay 58 the line conductorsjare further extended into connection with trunk conductors 98 and 100 which terminate in the windings of the line relay 300 of the ring hack switch H (Fig. 4:). The line relay 300 is accordingly energized over the two sides of the calling line in series in the usual manner and upon attracting its armature 316 cou'iple-tes slow acting release relay 301. Upon energizing in turn, relay 301 connects ground G to the holding conductor 99 at its armature 317, thereby completing the usual holding circuit by which the selector E and the line switch C are maintained in operated position. I

The calling subscriber at substation A. may now operate his calling device in accordance with the second digit 1 of the number, thereby producing a momentary interruption in the circuit of the line relay 300. The line relay 300is accordingly deenergi' 'ed momentarily and transmits an impulse of current to the vertical magnet 306 over the following path rground at G, armature 316 and its resting contact,.armat-ure 318 and its working contact, winding of the slow acting series relay 302, winding of the vertical magnet 306,- and the side switch wiper 309 in first position to batter-y. In response to this impulse of current the ver 'cal magnet is operated to raise the switch shaft one step, the wipers 330 and 331 lacing thereby brought into alinement with the first horizontal level of bank contacts. The slow acting relay 302 is energized in series with the'vertical magnet, and operates the private magnet-308 in the usual manner. Both the relay 302 and the private magnet are dcenergized after thevertical ope1'atioii of. the switch, the dee'ncr'gization of the private magnet being etl'cctive' tocause the advance of the side switch wipers from first to second position.

The callingsubscriber will now operate his calling device in accordance with the third digit 5 of the number, producing this time five interruptionsin the circuit of the line relay 300. The resulting (lei ncrgizations of the line relay 300 now cause five impulses of current to be transmitted through the rotary magnet 307, side switch wiper 309 having been advanced to its second position. By the operation of the rotary magnet 307 the switch shaft is rotated until the wipers 330 and 331 come into engagement with the fifth set of hank contacts in the first level, those hank contacts being indicated in the drawing by the reference characters 371and 312. The slow acting an energizing circuit for the of the ring back switch-as relay 302 and the private magnet 308 are operated as before and the latter upon deenergizing permits the side witch wipers to advance to their third and final position.

The calling subscriber will now hang up his receiver.

Since this operation opens the line circuit the line relay 300 is de'cinergizcd and closesa circuit for the relay 312- as follows: ground at G, armature 316 and 0 its resting contact, armature 318 and its working contact, Winding of the slowacting Series relay 302, winding of relay 312, and

the side switch .wiper 3.09 in third position to battery. Upon energizing, relay 812 com- -wpletes a newcircuit forthe slow acting i-elease relay 801 as follmvszgi'ound at G, ofi' normal contact 311 (closed at the first Upward -movement of the switch shaft),

armature- 315 and its right hand working contaet, armature 321 and its resting c011- tact, and the-winding of relay 301 to battery.. In addition relay .312 closes a circuit' for starting the operation of the ringing SWltCh' I which extends over the following pathzg'round at G", ofi' normal contact 311,

armature 315 and its left hand working contact, conductor 352, bank contactnormally Y engaged by the wiper 355 of the ringing switch I, the said wiper 355,-contact springs of the interrupter relay 351, and through the saidinterrupter relay-B51 and theniotor i'nagnet 350 in parallel to battery. The,

motor magnet 350- thusreceives an impulse of current by which it is operated to ad-J 5 vance the wipers 354, 355 and 356 of the ringing switch into engagement. with the second set of bank contacts. Since all thebank contact which are adapted to be engaged by the wipeeflofi, except the first,

40 are multipled together and connected to I ground G it will be evident that a. circuit has now been establishedfor the motor inagnet'350 and the interrupter relay 351, where- 'by the ringing switch I will. be caused to advance its wiperssuccessively into engagementwith all of the contact sets in its bank finally returning to theirfirst' or normal position. In other words, upon. recei\'ing .the initial starting impulse the switch 'I i makes a complete revolution and returns to normal position. Of course if the relay switch I will then immediately start 'on a second revolution and is still energized the will thus rotate continuously as long as the conductor 352 is grounded I When the wipers 354, 355 and. 356 of the bank contact 37201 the ring back switch, wiper 331, upper winding of bank contact 367,

the ringing relay 30 i and a signaling circuitfor operating the linger.

at substation A over the followin )ath:-

ground at G, ringingcurrent generator AC the resistance lamp, bank contact. 362,

wiper 356, conductor working contact of armature and the said armature, working contact of armature '313 and the said armature, conductor 98, bank contact Sf), wiper 80, contacts controlled by the switching relay 58 of selector E, bank contact 4+1, spring 40, line conductor 30, through the ringers at all the party line substations in parallel, conductor 31, spring ell-3, bank contact 17, contacts controlled by the switching relay 5S, wiper 82, bank contact 91, con duetor 100, armature 314 and its working contact, winding of ring cut oil relay 303 and through the exchange battery to ground G As soon as the wipers of the ringing-switch advance to the next set of contacts the ringing relay 30 l is of course deenergized and the above described. signaling circuit is the ringing relay 304; completes broken but is immediate] com ileted a ain when the wipers arrive at the contact set comprising ba'nk contacts 363, 361 and 365, these latter contacts being connected inmultiple with the. contacts 360, 361 and 362, respectively. It will be seen thc irthat the ringer at substation A will be operated twice for the ringer at this substation is tuned to respond to the 3S cycle ringingcuri'ent deliv ered by the ringing current generator AC Station A'liciiig a two-bell station the two rings received-serve to notify the subscriber that he is being called. When the wipers of the ringing switch arrive at the'contact set comprising bank contacts 366, 367 and 368 a circuit is completed for the ringing relav 30-1 over the following path: ground at (l wipers 355 and 354, bank contact 366, conductor 3T0, bank contact-371, wiper 330, relay 304-.and the side switch wiper 310. The ringing rclay30l is accordingly again energized and the signaling circuit is again completed. This time, however, the wiper 356 being in engagement with bank contact 368 the 16 cycle ringing current generator AC is included in the circuitinstead of the 33 cycle generator AC It follows accordingly thatthe ringer at the one bell 16 cycle station A: will be actuated to calling subscriber that the-signaling opera. tion is proceeding satisfactorily. In case the called not answer immediately the above described Q l 0 I A l signaling pcrations will be repeated duringthe second revolution of the ringing switch I and will cont nue to be rep'eated at interlower winding of the ringing subscriber at substation A does notify the I ca-ls "until a respon'se is made or until the calling subscriber again removes his receiver, at which t me a release will occur as presently set forth. t is to be noted that in the silent periods between rings the conductor 98 1s connected to ground iii; in order that the ring out 01f relay 303 may be operated immediately upon the removal of the receiver at the called substation whether the receiver 'is removed during a ringing period or a silent period. The ring cut off relay of course is so adjusted that it will not energize until the receiver is removed from the hook. But as soon as the subscriber at substation A answers the said relay 303 operates, either by current from the exchange battery alone or by current from the ex change battery and the generator in use in series, and closes a as follows: ground at G, ofi normal contact 311, armature 315 and its right hand working contact, armature 321 and its work ing contact, and the winding of the said relay 303 to battery. In addition by attracting its armature 320 relay 303 disconnects ground G from the holding conductor 99, thereby breaking the holding circuit by which the selector E and the line switch G are being maintained in operated position. The line switch C and the selector E immediately release and restore to normal in the usual manner. But since the receiver at substation A is oii thehook the line switch C will at once operate again to extend the line conductors 30 and 31 again into connection with the line relay of the selctor E. At the ring back switch H. the ring cut oil relay 303 also opens the circuit of theslow acting release relay 301 and this relay upon detnergizing completes a circuit in the usual manner for the release magnet 305. The operation of the release magnet restores the ring back switch to normal position and the locking circuit of the cut oii' relay 303 and also the circuit of the release magnet are broken when the shaft reaches its normal po sition. The ringing switch Iwill complete the revolution upon which it is engaged and will then stop unless some other ring back switch similar to the switch H is in use. \Vhen the calling subscriber at substation A notices the fact that his bell'has stopped ringing he willknow thatthe called party has answered and he will therefore remove his own receiver also and converse as de-' Tal king *current for the transmitters sired.

at the calling and called substations is supplied from the relay 5Uand the im )edanc-e coil 51 in the. first selector E.

receiver are replaced on the line the line switch (7 is restored in the usual manner.

What I claim as my invention is:

1. In a' telephone system, an automatic.

switch, a closed control circuit for said switch including a source of curi'entmneans for producim; a series of interruptions in said circuit to control the operation of said locking circuit for itselfv ion the automatic means for increasing. the currentv how in said circuit after each interruption to a point above normal in order to facilitate the energization of said relay after each deenergizatlon.

3.111 a telephone system, an automatic switch and a closed control circuit therefor including a battery, means for producing a series of interruptions in said circuit to operate said switch, and means in said switch for automatically decreasing the resistance of said circuit while the switch is operating.

4. In a telephone system, an automatic switch and a closed control circuit therefor including a battery, means for producing variable series of interruptions in said circuit to directively control the operation of said switch, and means in said switch for automatically decreasing the resistance of said circuit while the switch is operating.

5. In a telephone system, an automatic switch. and a closedcontrol circuit therefor including axbattery, means for producing a series of interruptions in saidcircuitto opcrate said switch, and means in said switch for automatically lowering the impedance of said circuit while the switch is operating.

switch, and means in said switch for auto.-

matically lowering the resistance of said circu-it during the transmission of impulses. I

S. In a telephone system, an automatic switch and a control circuit therefor, means for transmitting directive current impulses over said circuit to variably operate said switch, and means in said-switch forautomatically' lowering the impedance of said circuit durin the transmission of impulses.

9. In a telephone system, an automatic witch and a control circuit therefor, means for transmitting directive current impulses over said circuit to variably operate said switch, and means in said switch fol-"automatically lowering the resistance and impedance of said circult during the transmission of in'ipulses.

10. In a telephone system, a trunk l1ne,'a

main progressively movable switch indiopen connection in said conductor.

., cess'ible to said switch, two series of test conline, the two contacts of certain ll. In a telephone system, a plurality of subscribers lines, a group of trunk lines, means foroperating said connector to establish connection with a desired subscribers line, orlto select and establish connection with an idle trunk line, an operating magnet incl udedin said-means, and a relay operating as a busy test relay when a subscribers,

line is selected, and operatingas a stepping relay for said magnet'when an idle trunk is beingselected.

12. In a telephone system, an automatic connector switch, a plurality of, trunk lines accessible to said switch and divided into groups, a pair of test contacts for each trunk pairs being iconductively connected, a pair oi test wipers for said onnector, and associated testing mechanism and circuits in said connector suchthat the division of said trunk-lines into groups is determined by the abscnceof conductive connections "between the pair of test 'COIItQiC tSILSSOClQtBQ with the last trunk line of each group.

13. In a telephone system, an automaticconnector switch, a plurality of trunk lines accessible to said. switch anddi'vided into groups, a pair of test contacts for each trunk line conduotively connected, a'resistance included in certain of said connections, a pair of test wipers coiiperating with said pairs of contacts, and testing mechanism and circuits-associated with said wipers such that the division of said trunk'lines into. groups is determinedby' the presence of a resistance in the connection between the test contacts associated'with the lastft'ru'nk line of each group.

14;. In a telephone system, anautomatic connector 'switch,"a group of- 'trunk'lines actacts in said connector, there being a test contact ineach series for each trunk line, conductive connections between. the test contacts associated with'each trunk line except the 7 last, means for operating said connector to connect with the first of said trunk lines if the sanicis idle a test wi )er for each series of test contacts, and means controlled by the coijperationof said wipers with said test .contacts for causing said connector to automatically select an. idle trunk line-if the first is busy. v h

15. In a telephone system, an automatic connector switch, a. group of trunk lines accessible-to said switch, two series of test contacts in said connectonthere 'beinga test contact in each series for each trunk line,- conductive connections between the test contacts associated with each trunk line except the last, means for operating said connector to connect with the first of said trunk lines if "the same is idle, a test wiper for each series of test contacts, and means controlled by the cooperation of said wipers with said test contacts for causing said connector to automatically select an idle trunk line if the first is busy and eifective'to stop said 0011- nector on the last trunk line whether. the

same is busy or idle.

16. In a telephone system, an automatic connector switch, a plurality of-groups of trunk lines accessible to said switch, two series of test contacts in said connector corresponding to the several trunk lines, conductive connections between the two test contacts which are associated with each trunk line, except that between the test contacts associated with'the last trunk line of each group the connections are omitted,"

means for operating, saidconnector to connect with the first trunkline of any group I a test wiper for each if the same is idle,

and means in said con= series of test contacts,

'nector coiiper'ating with said wipers to cause said connector to automatically select an idle trunk line if the first is busy.

17; In atelephone system, an automatic connector switch, a plurality of groups of. trunk lines accessible .to said switch, two' series of-test contacts in said connector. cor: respondlng to the several trunk l1nes, -con-' Y I ductive connections between the twotest contacts which are associated with each trunk line, except that between the test contacts associated with the last trunk line of each group the connections are omitted, means for operating said connector to connect with the first trunk line'of any group if the same lot .is idle, a test wiper for each-series of test contacts, and means in said connector (:0

operating with said wipers to cause saidconnector to automatically select an idle trunk lineif the first is busy and efiective to'stop said connector on the last trunk line of the group whether the same is busy or idle.

18. In a telephone system,'an automatic connector switch, a group of trunk lines 210-.

cessible to said switch, two series of test con-- ta'cts in said connector corresponding to the several trunk lines, conductive connections between the two test contacts associated with eachtrunk line, a resistance included in the connection between the test contacts asso-

Images