US1402691A - Telephony - Google Patents

Description

H. S. TURNER.

TELEPHONY.

APPLICATION FILED mAY20. 1916.

Patented Jan. 3, 1922.

4 SHEETSSHEET 1.

H. S. TURNER.

TELEPHONY.

APPLICATION FILED MAY 20, 1916 Patented Jan. 3, 1922.

4 SHEETSTSHEET 2.

H. S. TURNER.

TELE PHONY. APPLICATION F ILED MAY 20. I916 Patented Jail. 3, 1922 L 1 s ts in 90 Mam H. S. TURNER.

TELEPHONY.

APPLICATION FILED MAY 20, 1916.

.1 402 9L Patented Jan. 3,1922. I

4 SHEETS-SHEET 4.

708 I 7/4 7/7 a w 4- I HUBJERT S. TURNER, 011' SAN DIEGO, CALIFORNIA;

'rnnnrnonr.

aaoaeai. v

Specification of Letters Patent.

Patented Jan 3, 1922.

' Application filed May 20, 1916. Serial No. 98,822.

erators may happen to be on duty at one time, means being provided to prevent an operator from receiving two or more simultaneous calls, and to prevent a call from being.'received while a call previously received has not beencompleted through. Means are also provided, operative when a sub-station 'is connected to a link connector or eordeircuit, whereb the operation of a disconnect .or recal signal associated with the link connector makes the corinectin operator ,nonselectable by an lncomin ca as long as said signal 1s in operation. cans are also provided, operative only when all the operators on 'duty are engaged in completing calls, to operate a signal shouldthere be acalling line waiting to be answered by an operator, the repeated operation of this signal indicating that another operator or other operators are needed at the switchboard. Means are also provided to indicate when the incoming calls are coming, in be-,.

low the working capacity of the operators who may be on duty at any time, thereby allowingone or more of the operators to be removed. Other objects will, be apparent from thespecification) Call distributing systems have many wellfl known advantages, 'amongstwhich are found the following:-

Fewer operators needed. 1 I Elimination of the intermediate f 'ame.

lines.

at switchboard. I 4 Ability of affew operators to handle the off peak load. i

beenopen to many objections, amongst which are found the following, 'all of whleh are eliminated in thesystem of my 1nvent1on:';

Complexityand expense of apparatus. 4

Quicker operators response to; th calling Saving of lamp and answering jack space' Call distributing systems have heretofore.

'. called-for llnet is that an operator is nonvselectable by a' Tim'e lost while selector switch mechanism is selecting an idle o erator.

Two or more ca ls simultaneously put through to the one operator.

A greater numberof calls put through to the first operators selectable than to the other operators, whereby some operators are kept working at ca acity whilst otherslremain more or less id e. r Only a ortion of the available operators at a switc board selectable by a men line or, if all the operators are availab e thereto, a lack of means whereby simultaneous calls are simultaneously putthrough to difierent' operators.

In the system my invention no-selector switch or other complicated electrically o erated mechanism is used, instead, the ca s are properly'dlstributed by means of simple relays of wellknown, forms. The entire number of relays used in an exchange served by this system of calldistribution, as 'described herein, is from 70 to 128 pen cent of the number used in most of the well known 1 exchange s stems where the lines terminate in a cut-o .and line relay and the cord circuits comprise two supervisory relays.

The number of relays used varies accordving to which of the described forms of distribu'ting equipment and cord circuiti's used and thenumber ofoperators to which each subscriber has access Therefore, as wellas obtaining all the advantages inherent in my improved form of; call distributing sys tem, I can eifect an economy in apparatus and exchange "space at .the' same time. The

above mentioned percentages of equipment l are based on a10,000 line exchange; 1,000

.cord circuits and from 30 to 60 operators,

In this system noattempt is made to autofmatically connect a calling line direct to a -'.'link connector or connecting cord at a I switchboard (position where the operator is idle.. Instea number of the calling line, whereupon the by insertin the-calling plug in a jack of the g A feature "of the invention means are provided for auto "matically indicating to an idle operator the Zoperator inserts an janswering plug in a multiple 1' aek of the line, obtains the number 'ofthe desired line and completes the callcalling'line-onl when an answering plu is I in regard the corresponding calling plug has not whereby an operatonhas no personal over the means WhlCh renders a pom oo-pen 'ng-applications Serial Nos.

' 45,232 and 64,967, as the present application, to the link connector clrcuits, in some respects consists in modified means for accomplishing, the results described there fication, and wherein ing all t I j In order to more fully describe my inven tion, referencewill be had to the accompany-s ing drawings forming a part of this speoi- InFigure 1, Part 1' is a diagram illustrate exchange apparatus individual to one hundred lines, when each line has access to nine operators (one additional relay being Part3, a.

adaptedtributing system; Figure 2, a dia ;trating a modification of a part 0 Figure 1; Figure 3,,a diagram illustrating the use of 1 bined with a system wheresome of the lines terminate in answering jacks at a particular :foperators position at the switchboard;.Figure 4, a dia ram illustrating various modifications of t g ure 1; Figure 5, a diagram illustratin a j niodification, of a part of Figure 4, and

ure 6,9, diagram illustrating a modificationof a part of added to the equipment shown for eac tional three operators) and the signal means used which is common to the entire ex-' change; Part 2, a diagram illustrating in part the apparatusindividual to the operators positions at theswitchboardand a part i of the ap aratus individual .to other lines;

diagram illustrating varioustypes ofl'ink connectors or cord circuits which are forfus'e' with the described'call dis am illusthe described call distributingsystem' come apparatus illustrated in Fig- 1" Part 2..

igure heet' 2 of the drawings 7 The lower. end of thereat' being continuous art 1 to Part 2. The wires Part3; it

For sake of convenience, the talkin cirterminal reference ;-numerals inserted in and 2 In the stead use twenty line relays common to each unit of'one hundred lines. Ten of these relays represent the units (0) to (9) and v ten addi- 1 a is intended to oin the'upper end of Sheet 1,

the wires endm and connecting terminating at the upper endsof Sheets 2 and 3 are continuous and connect Part-2 to therefore, the tens relays close a local circuitv v.through the multi-pole relays 0 to 9 respec-- tively, in order to perform the necessary switching operations. It will readilybe understood that, where conditions permit it, the tens relays could perform the switching operations controlled by relays 0 to 9.

For purpose of illustration, the exchange I described hereinafter may be considered as consisting of ten thousand lines, numbered respectively from 0000 to 9999, it being readily understood that the disclosed system 5 is not limited to any specific number of lines,

theamount of apparatus used varying proportionately with the number of lines served.

. I have shown at 10 atelephone substation of a-well known form, to the use of which form the invention, however, is not to be limited. As illustrated, thissubstation would- 'correspond to number 0001. The removal of the telephone receiver at this substation gives path for current from batteryll throughel enients 12, 13, 14, 15', 16, 17, 18, 19, 20, line relay (00), 21, 22, 23, 24, 25, 25, 27, 2s, 29, 30, 31, 32, 33, line relay (1) and ground, energizing relays (00) and (1). This gives path for current from battery 11, througheiements 12, right winding of section selecting relays 34, 0, 35,36 and ground, energizing relays 34, and 0. Assoon as contact 37 of battery control relay 0 after first engaging contact20, disen ages the latter from con-- tact 19, the trace circuit through contact 19 is opened and the path for the current from interrupter 14now proceedsby way of line 38,winding of battery cut-01f relay 39 and contact 37 of relay 0, energizing relay 39.

As the current passing through primary 25 of substation 10 is a variable one (due to the same passing through -interrupter 14),

though the same is not intermittent (due to the resistance which shunts the interrupter), an audlble signal isproduced in the receiver at substation'lO which continues until the operator answers the call. a The ener izationof relays 0 and 34 also -give spath or current from battery 40 (Part .2) through elements 41, 42, 100, 43, 44, 45,

.46 47, upper winding of section connecting re ay 48, 49, 50, 51, 52, 53, 54, 55, 5e, 57, 58 and 59 to the other pole of battery 40, energizing relay 48. This gives a shunt path, to that part of the trace circuit between ele ments 45 and 52, through the left winding of relay 34, lower winding of relay 48, elements 61,62, 63, thousand signal relay (0000), 64, 65, 66 and call transfer relay 67.

The upper winding of relay 48 is prefer ablv ofa higher, resistance than the lower 0 '8 s o o winding, as shown, though it Is not essential, as it is only necessary that enough current passes through theleft winding of the differentially wound relay 34 to neutralize the magnetic effect roduced by the current flowing in the described circuit through the right winding, thereby de-energizing the relay. When contact 46 becomes disengaged from contact 47, the described circuit through the upper winding of relay 48 is opened and all the current now flows through the lower winding of relay 48, maintainm the same actuated. Relays (0000) and 67 art 2) are preferably, though not necessarily, energized onl after the o ening of the circuit through t e upper win ing of relay 48, when they receive all the current flowing in the circuit. This is purely a precautionary measure, it only being necessary that contact 46 of relay 34 disengage contact 47, before contact 51 of relay 67 engages contact 68. If the two relays were energized simultaneously,.the adjustment of contacts 51-68 would be such that they could not engage before contacts 46-47 had become disengagedr The energization of relay 48 "(Part 1) through elements 41, 69, 70,71, 72, 73, 74, 75, 76, hundred signal rela (000), 77, 78, 57, 58 and 59 to the other poe of battery 40, energizing relay (000). I

The energization of relay 67 (Part 2) also gives path for current from battery 11 through elements 79, 80, 81, 82, 83 and 84;

or 85, 86 and 87 or 88, 89 and 90; and 91, 92,

93, energizingsignal controlling rela' 84,

rupter 81 in relation to its brushes As well as the relay circuits closed, as described, whenever a substation receiver is taken'ofl its switchhook, signal talking circuits are also closed through an operators receiver such as. 94 (Part 2) which corresponds to the operator selected by section connecting relay 48. These signal talking circuits are adapted to transmit by phonographic means the line designation of the calling line, thereby allowing the operator to pick out the correct line jack in the multiple and connect the talking set thereto by way of an answering cord and plug, the operation of connecting the talking set opening the aforementioned signal circuits, deenergizing all; the described relays, and eliminating the audiblesignal in the receiver at substation 10.

i' graphic record, which may be of the cylin- 1 drical form as shown, or of the disk or other spoken numbers from 0 to 9, or the record of any other form of line designations. The

members are so recorded that theyare re peated four times with a short, interval bep phone receiver which may be associated with gives another path for current from battery 7 1 connected to secondary 42 will have repeated 87 or 90 according to the position of 1nter-' I and transmitter, the use of the same being- The phone raphic signal means is shown type. This cylinder or disk has recorded onv its surface the repeated record of all the 123, 124, 125 126, 121, 107 and by the traced tween each repetition, then a longer interval and the numbers repeated again with the short interval. between them. Cylinder 95 is rotated by means of motor 96 which is geared thereto, or by any other rotating means. Interrupter 81 is revolved in svnchronism with cylinder 95, it being geared to the cylinder as shown or to motor 96. The number of repetitions on each cylinder or dlsc will depend upon its size, as, preferably, the record of the recording voice used does not trace the usual siiral upon the record, but makes one complete circle around the same. Bearing upon the record and adjusted in the roove representing the, voice vibrat ons of t e number 0, is the needle or stylus of a phonographic reproducer 97, which is associated with a telephone transmitter 98 ,tuations to the circuit controlled by it, and

.thereby reproduce by well known telephonic means the corresponding number in a telesaid transmitter circuit. The circuit for transmitter 98 may be traced from batter 11 through wire 79, transmitter 98 and primary 99 to ground. Therefore, any receiver into it the number0. For sake of clearness I have not shown in the drawing the. usual retardation coil placed in series with the transmitter when the. same is connected to the exchange battery, as illustrated, nor the condenser which usually shunts the primary well known in the art. 1

The described energization of thousand, signal relay (0000) connected operators'receiver 94 to secondary 42 by way of a circuit which ma be traced as follows: Fromthe right terminal of the secondary through elements 100, 101, 102, 103, 104., 105, 106, 107,108, 109, 110, 111, 112, 113, 114, .115, 116, 94, 117, 118, 119, 120, 55, 5e, 57, 58, 59, 40 and 41 to the left terminal of the secondary. Therefore, the number 0 correspondin to the 0 thousands in the exchange is soun ed in receiver 94'. Interrupter 81 revolves so that its metallic segment engages brush 82"before the next repetition of the numbers on record 95 takes place, consequently, relay 84 is energized and contaot107 disengages contact 106 and engages path through receiver 94, battery 40. and wire 41 to the left terminal of secondary 42. As secondary 42 is associated with the same primary that is incircuit with transnumber,'-co rr'esponding to the O hundreds in the exchange is sounded in receiver 94. During the short silent interval betweenthe repetition of the'number's as reproduced by the phonograph, themetalli'cjsegment'of in terrupter' 81 disengages brush 82 andengages brush 85, there y. dc-ener izing' relay 84 and energizing relay 87. ontact' 109' thereupon disengages contact '108 land en-.'

gages contact 127,, thereby' furnishing a tofore been passing through the described circuit through contacts 4344 of relay 0, relay-'0000',1w1 res 64 -65 retardatlon coil 66 and'wire 57*tobatteryi 40. On account of the impedance QO'QE- retardation coil 66, sufficient ,voicecurrentsfrom secondary 42 are shunted through receiver 94'; therefore the number 0,1corresponding to the O, tens 'is sounded in. receiver 94. If preferred, relay thereby) eliminating" retardatlon coil 66.

"During the next short silent interval be-- tween the repetition of the numbersas' 1'8 produced .by the phonographlc record, the metallic segment of interrupter 81 dlsen- 1 a g gjbrush 85. and engages brush 88, there? i -"by de-ener izingrelay 87 and ener 'zing re lay 9 0 ontac't-lll thereupon 1sen ages contact '110-and engages contact 128, t ere-.

.by furnishing a shunt path through receiverj;

'. 94- forthe voice currents from secondary 69 which have heretofore been passing throu h the described circuit through contacts 7 1' l oftheimpedance of retardation coil 77 sufiie cient: voice; currents. from" secondary69 are "shunted through" receiver 94; therefore, the

number'lfcorresponding, to thel units is sounded in receiver 94, maslmuchas second ary'6Q is associated with theprimary WhlOh is in series with transmitter 129 which'in'v turn reproduces the number 1, as hereinbefore described; In this way. the number 0001 is sounded in operators receiver 94,

After sounding the units number, the 'e-; tallic segment of interrupter 81 disengages brush '88 .and, consequently, relay is de-cz' energized. As the de-energization' of this relay is synchronous" with the long silent interval between the repetition of the phono graphic numbers, the long intervak forms a space between the sounding of a number and its repetition,- thereby indicating to the op-' 'eratorthe lastor umt number; Justbefore the metaHicsegment of interrupter 81 engages-brush 82 again the first .ofthe series of phonographic repetitions? of the num-' berstakes place, consequently, the number 0 ;isreproduced again and the numbers f 67 can be made'of the necessary impedance,

1 is engaged with brush 82," isbrush and brush 88, or is engaged with the 1003 .short so'that an appreciable amount oftime- .1 "follow I quick succession. Brushes mitter v98, which transmits the numberQO as reproduced bythe phonographic record, that,

82,85, 88' of-interrupter 81 ,are individual to the first switchboard section, there being I a corresponding brushes foreach of the 'other' sections, thereby preventing shunt paths '70 through the other signal controlling relays correspondin to, 84', .87, 90, when contacts; 92-'--93, of re a 67 become engaged. stead of indivi ual brushes the upper terminals ofrelay 84, 87,90 may lead to separate 76 contactsjisuch as '92, being connected ,to- 1 a gether and grounded only when relay I y1s energized, as shown in Figure 2.

Th wer winding er relay 48, 1e 'wi'nai got rela 34 an may b bri ged by condensers, as shown,

non-inductive resistances may be substituted therefor, in order to allow the voice cur- 'peating thenumber of the calling line, it 1.1 will be evident that if the operator does'not J f understand the. number: when it'bis] first, sounded, it 'willonly .benecessary; to wait"'95"-* 'for it tobe repeatedgflf the signalcon'nec a 1 tion is established by thecalling line at the time the metallic segmentyo finterrupter 81 latter, thereby sounding an incomplete nuni- 1 her, the sounding of one, two or three numbers only would indicate to the operator that V the number was incomplete and the operator would wait forthe next repetition which would necessarily be the complete number.

The time interval 'betweenthe repetition of the complete numbers can be made very v is not lost by having the operator wait. 1

Referring ,now to Part3. Ihave'shown therein five diflerent forms of link connec-' .tors which may be used with the described call distribution systema However, it will 1 be seen as these link connectors are described that any standard link connector circuit may also be used, Y

.By placingthe sheetcontainin I theright of the sheet containing art/2,the-

four l1nes shown at the top of eachsheetiwill 121E be found to correspond and are intended to be connected. I The link connector marked A represents a well known type and I1have made no change therein. If, the exchange is equipped with 12 5 this type of link connectors then when the I operator inserts answering multiple. jack 133 :or 134 art 1) of the calling: line, plath is given for current from battery 135-t rough elements 136, 137 138, 1 30 between that 4 lug 132 in-a.

139, 140, 141, or 142 (Pm 1)-;143ai 1d to. ground, energizing cut-ofl' relay 143' and I su ervisory lamp 139. Contacts 23-31 of re ay 143 disengage contacts 22-32, thereby opening the traced. circuit through relays (00) and (1) and tie-energizing the'same; Consequently, the circuit through relay 0 and the right winding ofrelay 34 is opened when contacts 35-36 of relay (00) are disengaged. The disengagement of contacts 43-44 of relay 0. opens the traced circuit through the left winding of relay 34, lower winding of relay48 and relays (0000) and 67,

energizing the latter. of contacts 92 -93 of relay 67 opens the t ese relays are de-energlzed. The isengagement of contacts 74-75 of relay. 48 or 70-71 of relay (1) opens the traced circuit through relay (000) ,thereby de-energizing the latter. The disengage-- ment of contacts 37-20 ofrelay 0 opens-the '1 traced circuit through relay 39, thereby de- The disengagement traced intermittent circuits through. relays 84, 87 and 90, consequently, the latter cease,

to be intermittently ene'rglzed. "The sound-- ing of the described numerical signals peased when the relayswere returned to their nor- I scribed hereinafter. 1

mal de-ener ized condition, as described,and

the same re ays are thereby made available] for use by other calling lines, as will be de- Before or, after inserting answering plug 132 in a jack of the calling line, the operator manipulates listening key .144, giving path for current from battery 135 through elements 136, 145, '146 and- 147 in multiple, upper spring of key 144, 148, 149, upper or secondary winding of induction coil 150, 94, 117, 151, 152, 153, .154, lower spring of key 144, 155 and to ground, energizing position controllingrelay 152. Thls gives path for current vfrom'battery 156 Part 2) through 5 elements 157, upper wi'n ing of position lock-'out relay'158, 1'59, 160, 161, 162, upper winding of position signal. transfer relay 163, middle winding of induction coil 150 and to ground, energizing relays 1'58-163. (The middle winding of induction coil 150 is not necessary when link connector A is used butis necessary when link connectors B, C, D or E are used.) The disengagement v of contacts 115-116 of relay lower or primary winding of induction coil '150 and battery 167. Therefore, the oper-..

ator' is enabled to converse with the calling party at substation 0001, inasmuch as the traced circuit through relay 152 connected much asa path for current from batte was glven throu h their lower or loc 'ng. wmdings whenre ay 158 was energized. This j elements 59 5s, 57, 5e, 55, 120 175 secondary of induction. coil 150 and receiver 94 to windings 145-155 of the link connector repeating coil; substation 0001 being connected to windings 168-169 of the same coil by way of contacts 170-171 of plug 132 and the spring contacts of jack 141 or 142. Voice currents are allowed topass relay 152 b bridging the same with a condenser 172.

aving obtained the number of the. desired iine the operator inserts calling plug 173 nto aj ack of'the line and manipulates ringmg key. 174. -.The other functions of link connector A are not described herein as the same are well known in the art and form no Vpart of the present invention.

hen the operator restores listenin .key 144 to its normal position, the traced clrcuit through relay 152-is opened, consequently contacts 160-161 are disengaged and the traced clrcuit through the up or windings of relays 158-163 is opened. owever, relays 158-163 are not (lo-energized thereby, inaspath may be traced from battery 40 through windings oi relays 158-163, 176,177,178 and 179 to -the other terminal of'battery 40.

Therefore, receiver 94 cannot again be con-' nected to a calling line signal circuit until either switch 176 has been opened or contacts 178-179 of lock-out release relay 180 have been disengaged. It is these locking windings and contact 175 on relay 158 and conlower tact 178 on relay .180 which provide the meanszfor evenly distributing the calls in an enchan" amongst whatever operators may be on u'ty at one time. If it is desired to have an operator selectable as soon as-disengaged from a calling line, switch 176 may be opened, thereby preventing the useof the lockin windings and making the operator selecta le as soonas disengaged.

In Part 2 relays. 166-163-158 and associate equipment corres'pondto the first operators position'at a three position section of a switchboard, relays 181-182-183 are the corresponding relays of the second position in the same section and relays 184-485-186 are the corresponding relays of the third poprised two positions relays 181-182-183 and associate equipment wouldbe eliminated, and if the section, comprised four positions additional relays such as 181-182-183 and associate equipment would be similarly connected. It will readily be understod that any number of positions may be similarly linked together or that each switchboard section may comprise but one positlon.

.sition in the section. If the section com- Whenever an operator vacates a position,

the operators' transmitter plug is removed from its jack, thereby opening the circuit through signal switching relay 166, 181 or 184, as the case may be, and, consequently,

de-energizing the same and switching the calling line signal circuit to the next position. This condition is shown at the central position of the first section. Therefore, should another call be received during the time rev lays 158163 remain locked up, the path for.

the signal circuit which was traced through contacts 115 of relay 163 and 550i relay the operator at the central position answered 166 now proceeds by way of elements 115, 189, 190, 187, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200,201,202, 188,203, 201, 54 and 55, thereby producing the calling signal in operators receiver 195 of the last position in the section instead of in receiver 94 of the first position. If'the operator at the central position had been on duty, then signal switc ingrelay 181 would have been energized and contacts 187-188 wouldhave been en aged with contacts 205206 and the signa circuit would have proceedediby way of elements 187, 205, 207, 208, 209, 210, 211, 206 and 188, thereby sounding thesignal in receiver 209, and in receiver 195 only'when relay 182 was locked up orenergizedfwhen now proceeds y way of the, middle winding of relay 163, middle winding of relay 182, and elements 215, 216, 198, 199, 200, 201, 202, 188 203, 204, 54 and 5556 of relay 166. The mi dle windings of relays 163-182 are such that the current flowing 1n thiscircuit is suffi-v cient to maintain the relays actuated, should the circuit through their loweror locking windings be opened. Therefore, should a calling signal oncebegin to be sounded in receiver 195 of'the last position, it 'cannot'be cut off andsounded in another receiver by the operator at the. central position coming on duty and energizing relay 1 81 by inserting the transmitter plugin jack 217 or by relay 163 of the first position being de-en'ergized by opening switch17 6, or by the disengagement of contacts'17 8-17 9 of relay 180.

When the operator at the second'position is on duty, then the path .for the current throu h the middle winding ofrelay 163 woul proceed by way of contacts 214-213 of relay'182 and 206-188 of relay 181, con sequently, relay 163 only, would remain locked up until the call was attended to and the signal circuit throughreceiver 209 at the second position would not be opened by the described opening of the circuit through the lower locking winding of relay 163.

Relays 182-183 and 185 -186 are eners gized and locked up in the same way as described in relation to relays 163-158, conis opened; and if relay 163 remains locked 4 I up, and either relay 182 remains locked'up or relay 181 remains de-energized, thepath for current through relay 48 (Part1), which was traced through wire 52 irom lfl;

relay 67. (Part .2 is open. Therefore,'re-

lay 48 (or any relay. of another 100 corresponding thereto), which corresponds to the first switchboard section represented by receivers 94-209-195, cannot be energized by another calling line, until one of the re- .lays 163 or 185 or 163, 182 or 185; is deenergized.

From the eager-1 description it will be, seen that more than one of the three operators at a section cannot receive a call at the same time. This arrangement is purely arbitrary and is used for purposes of economy in equipment, one operator selecting relay for each 100 lines giving access to one of the hree operators. As the second opem tor in' a'section is selectable as soon as the ond operator inserts a plug, three calls can be received in asection over the same equip ment, the time needed'by the first operator for completing the connection for the first selectable by way of the same equipment,

first operator has inserted an answering j 1 plug in a j aclg of a calling line, and the third operator similarly'selectable when the sec-.

inasmuch as this equipment would otherwise v .be idle until the first, operator had completed the call. Whenever relay 48 is rendered inopera tive, as described, a calling line in the OO'OOs is enabled to connect the proper-numerical second switchboard section, the traced path a 1 through contact 46' of relay 34 (Part 1),

signal circuit to an operators receiver at the instead of proceeding by way of'contact 47.

through the upper winding of section con-' necting relay 48, now proceeds by way of contact .60 through the upper winding of section connecting relay 218, corresponding to the second switchboard section, elements 219, 220, 221, 222, 223, 224,225, 220, (signal switching relay 227 corresponds to relay 166 of the first position in the first section and is therefore energized when an operator is -on dut at the first position in the second section; by the "already traced ath to battery 40, energizing relay 218. 7 his gives a shunt path through the left winding ofsection 228,. 229, 216 .and then proceeding selecting relay 34 and the lower winding of Q relay-218,. (similar to that traced through I the lower winding'of relay 48) elements 230,

battery 40. Call transfer relay 234 is energizcd by the currentflowing in this path in the same way that the corresponding relay 67 of the first section was energized.

The described circuits and line signaling apparatus b which the numerical signals are produce in the'operat-ors receivers, for

sake of brevity and clearness in the draw- I ing are not 'shownand described in relation to the second section, inasmuch as they are similar to those described in relation to the first section. Dottedline 233 represents the elements corresponding to thousand signal relay (0000), wires 64-65 and retardation coil 66. Contact 239- of relay 218 is 'con-" instead opens the direct, path to} battery .40

byqway of contact 235, thereby removing. the short-circuit around the middle winding 'of'relay and allowing current to flow 0 through sald winding and elements 253, 254," .,255,' 256and 58 to battery 40. In both cases, -1

lthe middlewindings cannot be energized- Y -until. af ter the relay has actuated. Relays 242-245 are locked up-in the'same- 245, 243 and-246; and thewindingsof re- @next call will produce the numerical signal' 1n the} receiver atthe third position'of the "L,

secondf. section. The traced path through nectedthrough elements, at the secondsection in the same way as contact 750f relay 48 is connected at the first section. It iw1ll be understood that any contact or winding; not shown connected, is connected and fundtions in the same way as the corresponding; "element of thefirst section. The top contacts of relays227, 240, 241, 242 and 243;;

the upper windings of relays 240, 244, 242,

lays 227, 241 3113-247, well as the operators receivers, transmitters and induction coils are also not shown, itbeing'understood that they are connected inlthesamev way as corresponding elements fshown in the first by way of contacts 259-260, 261-262 of re-- section.

' As the traced circuit through wire 63 and relays (0000) ;and 67 controlled the produc tion of the numerical signalin receiver j-94 of the first position of the first section, in a the traced circuit through the similar way corresponding elements 232, v233 and relay 234 controls the productlonoffi the signal i'n-n the receiver at the'first position of the sec? ond section.

When the operator at the first position ofthe second section answers a call, relays. 240-244 are locked up, as described in relation to the corresponding relays 163-158,

and relays 218-234 are dc-energized as described in relation to thecorresponding relays 48-67 of the first section,'thereby making the same available'for use by other call.- ing lines.

The next calling line will produce the corresponding numerical signal in the re'--,. I

'.j- -Whenever relayl2l8 is rendered inoperative, as just described, a calling line in .the

ceiver at the second position of the second section, masmuch as the receiver thereat is connected to the s1gnal'c1rcu1t 1n the same way as described in relation, to the second position of the first section; The traced tacts 252-224 of relay, 240. The traced path through relay 234v to battery 40 was Inents 269, 270, 271, 272, 273, 274, 275, 276,,

opened when contacts 235-236 of relay 240 through relay 234 to battery 40, throu h the. middle winding of relay 240, and e ements 253,254, 255, 256, 58 and 59.

The purpose of the middle windings of slightly different way,'the same being an alternative form'which ma or may not be 'used, as desired. The middle winding of relay 163 cannot be energized until its contacts 54-204 are engaged, thereby preventing a premature energization of the rela Contact 236 of relay 240, which correspon s I to contact 54 of relay. 163, does not engage. 1

any contact when the relay is energized, but

way as relays '240-244; consequently, the

wire-222 instead of proceeding byway of contacts 248-249 of relay 242, now proceeds lays 243-247 and contacts 263-249 of re-- lay 242. The traced path through relay 234 i fto'batter'y 40 by way of the middle winding of relay 240, was opened when 'contacts' 253-254 of relay 242 were disengaged, but

"there is still a path to battery 40 through the middle winding of relay 242 and ele- I ments 264, 265,266. 267, '58 and 59; come 5 5 quently,'-theshort-circuit around the middle wind ngot'relay 242 is removed, and this ,relay is 'maintained actuated by current" flowing in this winding.

Relays 243-246are locked up in the same up or energized.

0000s is 'enabledlto connect the proper nuceiver atdthe third switchboard section. 1

'The'tra'cedpath through contact 46 of relay =34 (Part:1) ';instead of proceeding by way of contacts; 47 vor 60 through the upperwindings ofrelays'48 or 218, now proceeds .bygway'of contact through the upper winding of section connecting relay 268, elegwa y as relays' 240-244, consequently, relay 218 Part 1) cannot be energized again by j; acalling line, inasmuch as the path through,

- the relay -to battery 40 is now open, wire 222 Y being disconnected from the battery as long as relays 240, 242 and 243 all remain locked already traced path to battery 40, energiz- .used; for the other described sections as well ing relay 268. This gives a shunt path through the left winding of relay 34' and the lower winding of relay 268 elements 279, 280, 281, 282, 283, middle windings of relays 284 and 285, 286, 287, 288, 289, 290, 291, 5a

and battery 40. Call transfer relay 283 is energized by the current flowing in this path in the same way that the corresponding call transfer relays 67 and 234 of the first and second sections were, energized. Dotted I line 282 represents the corresponding ele- 'ments of the third section to those described as being represented by-dotted line 233 of the second section. Contact 292 of relay 268 i is connected in a corresponding way to contact 239 of relay 218. I Y; Relays 234-283 are shown without a right grounded contact and armature switch such as shown on relay 67, though it will be understood that relays 234-283 have such contacts for the purpose of closing a sim'i-;

larcircuit to that controlled by contact 92 of. relay-'67. Relays 293, 294 and 295,;cor-" respond in function to. relaysI166, 181,3'and 184. Relays 284, 285 'and 296 correspond in function torelays 163, 182: and 185. "Be. lays 297, 298 and 299 correspond 11111111011011 to relays 15 ,188 and 186'.

pThefthird sectionrelays'represent another alternative-form which may. or nlay not be [as for the third one. The use-of this form equires less contacts on the relays of the.

I 'first and second positions.

" windings of relays 284-285'1are such that I 2180. The ener izat on of relay 18Q-causes *contacts 178-1 9 to be idisengaged, there-- The middle I {thefl-current flowing'in the. traced; circuit .--ftherethrough' which energized relay 283 is not'sufiicient to causelthe energization one ta'inthem energized onceihey have been energized by -cnrrentpflowmg,1n'theother lays- 284 -285, though'it'is sufiicient to mainiv windings.

. When tilt-8885389118 the first 5839181181 the third section answers a call, relays- 284-297 are energized or locked up,'as described in relation to the. corresponding relays 163-158 and 240-244; "relays'268-283 being de-energized, as described in relation to the corresponding relays- 48-67 and 1?.1'218-234, thereby makin' relays 268-283 ;available for use by ot er calling lines. The traced path.;through wire 272 to wire .277, by way of contacts 273-274 ofrelay 284, is openedwh'en the relay becomes energized, but thereis still another path avail-.

able by way ofcontacts3O0-301ofjrelay 285 and contacts 302-303] of, relay 294.

'- Therefore, relays 268-283 can be, again energized and the next call will"be,rece1ved by the operatorfat the second-positiom'inasvmuch as the operators receiverf thereat is connected to the signal circuit in the same f way as described'in relation'ftothe second I i position of the first{section.-

-locking windings I I 285-298 and 296-299,; consequently,- all these relaysjare de-ener-fl,

current is not passing When the operatoratthe second position of the third section answers a call, relays 285-298 are energized or locked up (as described in relation to the corresponding relays 182-183 and 242-245) and relays 268-283 are made available for use by other calling lines. The traced path through wire 272 to wire 277 by way of contacts 300-301 of relay 285,. is opened when the relay becomes energized, but there is still another path available by way of contacts 304-3050f relay 296 and contacts 306-307 268-283 are again made available for use by other-calling lines. However, the traced path through wire 272 to wire 277 is now entirely open, inasmuch as the, energization .of rlay 296 disengaged contact'305 from contact 304 and connected it to contact 308.

269, closeciby I the next] calling line, instead of proceeding by way of contacts 270-271.

.of'rela 283, now'proceeds by way of "relay 180, mm 309',' contacts 308, 305, 306, 307 and wire .277,'lenergizing lock-out release relay Therefore, the traced'path through 'wire by opening the circuit throu h the described 4 of ro ays 1623-158,

gized, providin through onelof t eirother windings," The de-energizationgofanyone or all of, 1-re'-.

lays 163,182 or 185 opens the'circuit through wire 228;the de-energization of any one. or

'-all of.relaysf240,"242, 243 opens the circuit through-wire 277 and the de-energiza-- tion of any one or all of relays 284, 285,296

opensthe circuit through wire 309. There- I fore, if only one of-these relays 'is'de-em 1i ergized the circuit is opened through frelay;

180 and the latter "is; .de-energized. "-The traced path through wire 269 andcontacts 270-271'of relay 283 is also opened, pro- 'viding' one orall of the last cited second section'relaysis de-energized, consequently, thecalling line signal circuit which was closed through wire 269 :is' closed instead. through wire'219 and-contacts 220-2215of V re'la'y-234, .the" call being received in the already'described manner by the operator I atlthe first, second or third position of the second section. However, the path through contacts 220-221 of relay 234 is open also, providing one or all of the cited relays of the first section is de-encrgized, in which event the calling line signal circuit is closed through wire 49 and contacts 5051 of relay 67, instead-of through wire 219, and the call would be received by an operator at the first section, as already described. Therefore, whenever relay 180 is energized when all the signal transfer relays of all the switchboard sections at which there are operators are energized, the described sequence in which the incoming calls are received b the operators is repeated. It will readily lie seen that relay 180 and the de scribed locking windings on the signal transfer relays furnish the means for evenly dividing the calls among the operators on duty, inasmuch as once such a relay is locked up it cannot be de-energized as long as there is a similar relay located after it in order of sequence that is not locked up, the equivalent circuit changes to those produced by this-locking up being performed by the removal of an operators transmitter plug from its jack.

A single call emanating from one of the 0000s has now been traced through to each one of the operators at the switchboard, the calls having been received successively only after the release of the signaling circuit,

which is brought about by the insertion of an answering plug in a line jack of the calling line. It is evident that provision must be made for handling simultaneous calls, without delaying them, until such release is made and without confusing the signals. As illustrated; and about to be described, arrangements are made whereby as many simultaneous calls may be practically in stantaneously put through to the operators as there are switchboard sections at which there are operators on duty. As any probable combination of simultaneous calls will be distributed amongst the various 100s, the selective means illustrated is such that only one line in each 100 can close the described numerical signal circuit at one time, the first line to close said circuit looking out all the other lines of the same 100 until an answering plug is inserted in the proper line jack, whereupon another calling line in the same 100 is enabled to at once sound its signal in the receiver of the next operator ready to receive the, same. Inasmuch as only one call can be received by an operator at a time and an operator is only selectable when not otherwise engaged, the

only delay incident to attending to the call of the second calling line is that represented by the time it takes the operator to insert the answering plug in the proper line jack after having heard the corresponding signal. It is evident this delay will be insignificant and only a fraction of the delay now incurred in manual systems where the second calling line must wait until the call has been completed through for the first calling line. Should threeor more lines in the 'same 100 call at the same instant, the calls gages contact 310. Therefore, should the rehs ceiver at another substation in the 0000s, such as 0024, be removed from its switchhook after the receiver at number 0001 has been removed, instead of path being given for current from battery 11, through contact 16 of relay 39, as described, a path is given for induced current from secondary 311 through elements 310, 16, 17, 312, 313, 314, relay (20), left one of terminals (24), substation line and apparatus, other substation line, right one of terminals (24), relay (4) and to ground. The induced current in secondary 311 is produced by the variable current flowing in primary 315 through interrupter 14. Relays (20) and (4) are not energized by the induced current flowing in this circuit as the same need battery current for their energization;however, the induced current flowing through these relays is such that it produces an audible signal in the receiver at substation 0024 which is similar to the one produced by the described variable current flowing through the substation primary direct from interrupter 14. The purpose of the audible sig nal produced at the substation is for assuring the party thereat that the line wires and central office apparatus are in working order and also for providing a means whereby the discontinuing of the signal, brought about when the operator inserts an answering plug in the line jack, indicates to the calling party that the operator is ready to receive the number of the desired line, thereby allowing the verbal query of the opera tor to be dispensed with.

As no numerical signal circuit is closed until a relay such as (20) or (4) is energized the second calling line does not interare energized and the corresponding numerical signal 0024 is produced in the same way as described in relation to the production of the .0001 signal.

If two substation receivers belonging to the same 100 are removed from their respective switch-hooksat precisely the same in stant, nevertheless, only one of the numerical signal circuits will beclosed. Assuming that the two already described numbers 0001- 0024 call at the same instant, then, if relays 0 and 2 are energized at precisely the same instant, current will continue to flow through line relay (00) by way of contacts 37-20 of relay 0 and relay 39; but current cannot continue to flow through line relay, by

way of contact 314 of relay 2, inasmuch as the path is opened for current through contact 313 when contact 16 of relay 39 dlsengages contact 15, and even if contact 316 of relay 2' had enga ed contact 314 before relay 39 was energize battery current 1s cut off from contact 316 when contact 37 disena ed contact 317. Therefore, relays (20), %4? and 2 are all de-energized and remain de-energized as long as relay 0 is energized.-

- It will be noted that the battery current throughirelay 39 is led, by way of contacts such as'fi37j-3l7 of relay 0, 318- 319 of relay l' -afid 316 of relay 2, successively to all the relays 0-4-9 pertaining to the same 100. f I This is 'a precautionary detail-to prevent the ossibility, however slight, of two of the reays being energized and engaging thelrcontacts such as 37-20 of relay 0, at precisely the same instant.

scribed; preference is given to the lowest ten relay when two or more simultaneous calls are received. However, it will be readily understood that the preferential arrangement is purely arbitrary and may be, varied as desired.

As soon as thecall from line 0001 has been V answered, relays 0 and 39 are de-energized and, consequently, path is given for current from battery 11 through elements 12, 13,14, 15, 16, 17, 312, 313 and 314, thereby causing relay (20) to be energized and closing the current which flows through contacts 15-16 of relay 39. Therefore, it will readily be seen and understood that while preferenceis given to the lowest number of two or more As illustrated and de-' ary na simultaneous calls, no preference is given to a lower number if a call is made an instant after a higher number has called. The time between the two calls, which would insure the higher number the first control of the si nal vcircuit, would depend on the rapidity of action of relay 39 and relays (20) and 2.

As such relays are very rapid in action, a fraction of a second difference would be sufficient.

.As the line relays used in the preferred embodiment of my invention are not indivldual to each line, two lines in the same ten of the same hundred calling at the same time, or one calling before the other was attended to, would permit the current flowing through the ten relay to return to ground through both of the unit relays; for instance, if lines 0000 and 0001 are both calling then a path is given through terminals 21--33 of- (01), as hereinbefore described,

and unit'line relay (1) is energized; however, the battery current fiowing through ten line relay (00) would also have a path through the left one of the (00) terminals (corresponding to 21-33), apparatus at substation 0000, right one of the same ter- "minals and to ground through relay (0').

As the 'unit relays control the production of the proper numerical-signal for the unit numbers, confusion caused by mixing two unit.

signals is prevented by causing contact 73 of relay (0) to disengage contact 72, thereby opening, the circuit traced therethraugh from secondary 69 and contacts 7071 of relay (1), consequently, the 0 unit signal is sounded and not the 1. The ord -r of preference for the unit relays is from the lowest numberto the highest, though of course the arrangeme'nt'illustrated and described is purely arbitrary.

In order to insure the proper operation of I I as many unit relays as may ever be operated at one time through one ten line relay, the Winding of the latter may be made of low resistance in comparison to the windings of the unit relays, thereby allowing sufiicient current to pass through one ten relay to operate various unit line relays.

It will readily be understood, without any further'description, that the series of unit line relays (0)(9), tens. line relays are all respectivelyv connected in the described manner, as illustrated in the draw ing, thereby positively preventing more than one calling line in each 100 from signaling at the same time, also that each relay connects the proper numerical signal second- (such as 42 or 69) to the described sigcircuits.

The terminal rack arrangement shown in the upper part of Part 1 is purely diagrammatical and is used for purposes of illustration' only. In practice the wires from the '(00)(90) and battery control relays 0-9 v cut-off relay contacts, such as 22-32 of cutoff relay 143, could be taken direct to the proper terminals of the tens and units line relays, instead of to terminals as shown in the drawing. The numbers assignedto the terminals and the connections thereto show clearly how the proper relay is connected to each line. 1

It is evident that as well as preventing two calling lines in the same 100 from controlling the common numerical signal circuit at the same time, means must also be provided for preventing two calling lines in different 100s from simultaneously producing their respective signals in the same operators receiver, inasmuch as a plurality of the 100s or all of the same have access to the same operators. The described 100 corresponds to the numbers 0000 to 0099, and in the top row of relays in Part 2 are illustrated section connecting relays corresponding to some of the other 100s in the exchange. Relay320 corresponds to the next 100 or the numbers 0100 to 0199. Relay 320 corresponds in function to and is controlled similarly to relay 48 in Part 1. The section connecting relays for the other switchboard sections, corresponding to 218-268 in Part 1 are not shown, for sake of clearness, it being understood that each 100 is equipped with such relays and that the same are respectively installed, in relation to the second and third sections, in the same way that relay 320 is installed in relation to the first section. The upper winding of relay 320 is energized when a call is initiated at any one of the substations of lines 0100 to 0199, the path through the winding proceeding by way of wire 321 to contacts 50-51 of relay 67 and thence over the same path as that traced from the upper wlnding of relay 48 through wire 49 and the same contacts. The consequent energization of relay 320 gives path for current through the lower winding of the relay (as described in relation to the lower winding of relay 48), contacts 322-323, wire 324, contacts 325-62 of relay 48 and thence over the same path as that already traced when contact 62 engaged contact 61. Consequently, the same relay (0000) is energized producing the 0 thousand signal; but when contact326 of relay 320 engages contact 327 it closes a circuit through wire 328 and relay (100) to.

retardation coil '77, instead of a circuit through wire 76 and relay (000) to the same coil as was closed when contact 75 of relay 48 engaged contact 74. Therefore, the traced path to wire 126, instead of proceeding from the (0) secondary 42 (Part 1) proceeds from the (1) secondary 69 by way of elements 329, 330, 331 and 332, thereby sounding the 100 signal instead of the 000 signal. The ten and unit signal is sounded according to the ten and unit line relays the incoming call.

energized by the callingline, as described in relation to Part 1.

Call transfer relay 67 was energized as soon as contacts 322-323 of relay 320 were engaged, consequently, contact 51 of relay 67 disengages contact 50 and engages contact 68. Therefore, should a line initiate a call in the 0000s or in any other 100, there would be no path for current from battery 40 by way of contacts 51-50 of relay 67, as herelnbefore described; consequently the first section relay, such as 48 or 320 of the 100 in question, could not be energized. However, as contact 68 of relay 67 is connected to contact 226 of relay 227, a path is given for current from battery 40 by way of wire 222 to contact 221 of relay 234. This path through contact 226 is the same as that already traced by way of wires 228222 when all the relays 163-182-185 had been locked up, when all the relays 166-181-184 had been de-energized, or when one or more of the former had been locked up and one or more of the latter de-energized. Therefore, provided all the operators who might be on duty at the second section are not busy, or all the positions thereat are not vacant, the section connecting relay of the second section of the group containing the call initiating line is energized and the call is put through to an operator at the second section. The path for battery current'through wires 228222 is opened; when all the relays 240-242-243 are locked up, when all the relays 227-241 -247 are de-energized, or when one or more of the former are locked up and one or more of the latter de-energized; but a path is closed thereby through wires 228-272 to contact 271 of relay 283. Consequently, the call is ut through to a third section oper: ator w en no second section operator is available. When relay 234 is energized, con} tact 221 disengages contact 220 and engages contact 333, thereby giving path for current from battery 40 to contact 271 of relay 283 and instantly making the third section selectable by the next calling line of any of the various 100s. This path through contact 333 is the same as that traced hereinbefore through wires 277-272 and the third section relay contacts when. there was no available operator at the section section. When relay 283 is similarly energized. contact 271 disengages contact 270 and engages contact 334, thereby connecting battery to wire 269 by way of relay 180; consequently, the next calling line would cause the energization of relay 180, thereby open the cir cuits through the locking windings of the signal transfer relay and making one or more operators selectable without delaying Relay 180 is of high enough resistance to prevent the actuation of the section connecting relay of the call ing line when included in circuit therewith,

has been first de-energized.

. It will be seen from the foregoing description that as soon as one call is received in a switchboard section, subsequent calls are locked out from that section and are put through to the next sections, the controlling means beinlgI the call transfer relays 67, 234 and 283. owever', means must be rovided for handling calls from Various undred groups that may simultaneously be initiated at substations. For instance, if a call was simultaneously made in the 0000s and the 0100s and all the operators were free, then the paths through the u perwindings-of relay 48 (Part 1), and 320 art 2) wouldboth be through contacts 50-51. of"

relay 67, consequently both relays 48 and 320 would be energized. However, when 'contact 62 of relay 48 disengages contact 325 the path is opened through contact 323 of relay 320, consequently, relay 320 cannot be locked up by current flowing through its lower winding, but relay 48 can be locked "up bythe current flowing directly through its lower winding from relays 67 and (0000), wire 63 and contacts 62-6-1. Therefore, as soon-as relay 67 is energized and contacts 50-51 disengaged, the path is opened I through the upper winding of relay-320 and the latter is. de-energized and the section connecting relay corresponding tothe second section is energized instea Relays 335 and 336 represent the first section connecting relays corresponding to the numbers 0600 to 0699 and 0900 to .0999, the dotted lines 337-338 representing the con nection of contacts (corresponding to contacts 323-322 of relay 320) of the first section connecting relays of the other hundred groups in the 0000s. Therefore, whenever'two or more section connecting relays in the;same- 1000 are energized at the same instant, pref-r erence is given in control of the line signaling apparatus of a section to the lowest numbered line and the circuit through the lower or looking winding or windings of the other relay or relays is opened when the top contact of the numerically lower relay disengages its alternate contact. The preferential ar-;

rangement shown in the'drawing is of course purely arbitrary.

If the simultaneous calls had been from different thousand groups, then the higher number is locked out in a slightly different manner. Relay 339 represents the first section section-connecting relay corresponding to the numbers 1000 to 1099. The upper winding of this relay is connected to contact 50 of relay 67 by way of wires 340-321 and the relay is energized by said winding in the described manner. However, contact 341 of relay 339 is connected to wire 64 by 'energizedwhenever relay 335 is energized.

the'current flowing through relay (0000) thev second or third section section-connecting relay of the 1000-1099 line is energized and locked up and the call put through to the operator at that section. 0

For the sake .of 'clearness in the drawing, I have shown but four of the thousandsignal relays, namely (0000), (1000), (6000) and (9000). Dotted lines 344-345 represent the connection of contacts, corresponding to 342-343 of relay (0000), of the other thousand signal relays. Therefore, when: ever two or; more thousand signal relays in a section are energized at the same time, preference in controllof the line signaling apparatus of the section is always given to the numericallylower relay and the circuit through the other relayor relays is opened when the bottom contacts of the numerically lower relay become? disengaged. At the same time the other call or calls are not delayed, inasmuch as they are at once put 95 through to the other section or sections, the exchange capacity for simultaneous calls depending on the number of sections the sw tchboard is equipped with, which, of course, should be sufiicient to handle, the 100 maximum number of simultaneous calls apt I to be received.

Contact 346 of first section section-con necting relay 335 is connected-by wire 347 to relay (600), consequently, relay (600) is As contact 348 of relay (600) is connected bv wires 349-350 to secondary 351, which is associated with primary 352controlled by transmitter 353 which reproduces the six; signal, the 600 signal is produced in' th-e operators receiver whenever relay 335 is energized. In the same way the 900 signal is produced whenever relay 336 'is energized, inasmuch as contact 354 is connected by wire 355'to relay (900) andcontact 356 of,

relay (900) connected by wires 357-358 to secondary 359, which is associated with primary 360 controlled by transmitter 361 which reproduces the nine signal. As the (0000) relay'is energized whenever relays 335 or 336 areenergized, the proper thousand and hundred signal is given, forming 0600 or 0900, the case may be, The tens and units signal are supplied by the described line relays. For the sake of clearness in the drawing, I have show'n'but four hundred-signal re- 'tively. Relay 100s are represented by their respective renal, and as the bottom contacts. of these re lays are connected to relays (100), (600) and (900), respectively, the proper hundred signal is also produced. The other 100s in the 1000s are represented by dotted f lines 365-366.

First section section connecting relays 367-368 correspond to numbers 6000 to 6099 and 6900 to 6999, the other 100sin the 60005v beingrepresented by dotted line 369. 1 Contact 370 is connected by wire 371 to relay (6000), thereb producing the proper thousand signal, tie bottom contacts of relays 367368 bein connected respectively, to relays (000) and (900), thereby producing the proper hundred signal.

First section section connecting relays 37 2-37 3 correspond to numbers 9000 to 9099 and-9900 to 9999, respectively. Contact 374 of relay 372 is connected by wire 375 to relay (9000), thereby producing the proper thousand signal; the bottom contacts of relays 372 373 being connected to relays (000) and (900), respectively, produce the proper hundred signal. Dotted line 376 represents the other relays in the 9000s.

It will readily be understood that each switchboard section would comprise ten relays such as "(O000)-(9000) and ten relays such as (000)(900) and that the same would be connected, as herein-before described.- so as to produce the proper numerical signal. Also'that while only three switchboard sections have been illustrated and described, it will be evident that as many more may be added as desired, a relay such as 234 being connected for each section added and a corresponding section-connecting relay and contact on relay 34 added to each 100 for each such section.

The section-connecting relays pertaining to the second and third sections are not shown, but they are connected to contacts 220-270 of relays 234283, by Way of the wires as indicated at 37 7378, their connection being the same as the connection of Wires 49-321 to contact 50 of relay 67. Dotted lines 233, 282 represent the thousand signal relays, as hereinbefore described.

If at any time and for any reason the line signaling apparatus which produces the order to locate the calling line. If the thousand si al was missing, the opera-. tor knowing 9 correct hundred, ten and unit, would try:each one of the corresponding thousands. If the hundred signal was missing, the operator knowing the cor? rect thousand, ten and unit, would try each one of the corresponding hundreds. The proplerten or unit couldbe similarly locate It will be evident that if the calls are received faster-than the operators on duty can attend to them, there will be no way the operators can tell whether calls are being inordinately delayed or not, the various sec tion-connecting relays of calling lines merely being non-operative whenall the operators are busy. However, it has already been described how lock-out release relay 180 is energized whenever all the position signal transfer relays (such asv 163) of the operators on duty are locked up and another call is received; should all these signal transfer relays be energized by means of the circuit traced through their upper windings, (representing the'operators engaged in completing calls) then the circuit through relay 180 is not opened when contact 179 disen ages contact 178, inasmuch as current woul still flow through wire 272 and contacts 271- 334. Therefore, relay 180 remains energized and contact 179 en ages contact 379, giving path for current f rom battery, 40 through elements 179, 379, 380, 381, 291, 59 and the other pole of battery 40. Lamp 380 may be mounted on the chief operators desk, so that I its constant illumination would constitute a warning signal and indicate to the chief operator that the calls were being received above the capacity of the operators on duty. Therefore, more operators could be sent to the switchboard until the infrequent illumination of lamp380, its illumination for a very short time, or its non-illumination, would indicate that enough operators were on dutyto handle the load.v vA registering device such as 381, which may be of any de-v sired form, is added to the circuit if it is desired to have a record of the number of times an overload is present. If this de, vice constituted a stylographic register, a permanent record of the time that calls were delayed would be obtained.

Contacts 178-379 of relay 180 may be so far apart, that, when some of the position signal transfer relays are locked up and are consequently re-energized when contacts 17 9 -178 of relay 180 become disengaged, contact 179 has not time to engage contact 379 before relay 180 is de-energized by the cutting off of the current through wire 272. Therefore, lamp 380 will onlybe illuminated and registering device 381 record when there is an actual delay in attending to a call.

However, even contacts 179- 37 9 of relay 18 l calls that co calls being sent to the other positions only when the first position operator was busy rent momentarily passin 180 should become engaged, the engagement would be only momentary and lamp 380 and registering device 381 may be such as not to be illuminated and energized by curthrough them. As well as relay 180 b81111! kept-energized should all the operators on duty be engaged in completing calls, it will remain energlzed should more calls be simultaneously received than there are switchboard sections available, inasmuch as relays 67, 234 and 283 would all be energized and path would be given for current from battery 40 through wire 52 and contacts 51, 68, 221, 333, 271, 334 of the relays, relay 180, wire 269, and the described ap aratus to the other pole of battery 40. Iherefore, the repeated 1llumination of lamp 380 might also indicate that too many simultaneous calls were being received for the operators on duty, consequently more operators could be sent to the board. When all the switchboardpositions are occupied, the repeated illumination of lamp 380 would indicate that the capacity of the switchboard was too small. i

The chief operator or other ofiicial is enabled to know when there are too many operators on duty for the load, as in that case lamp 380 would not be flashing, or by means of an observation of the time interval between any two calls as received by any one of the operators. As the calls are evenly divided amongst the operators on duty whenever one operator is found idle for a longer interval thanv is standard practlce, it would be certain that the calls were not rotating quickly enough among the operators, consequently, some ofthem could be removed.

The use of manually operated switches such as 176 (as shown at the first section) furnishes means also for determining the load, inasmuch as by opening the switch, position signal transfer relay 163 cannot be locked upand. consequently, the operator at the first osition would receive all the ul d be handled thereat, incoming completing a call or receiving a disconnect or recall signal as will be hereinafter described. It will be readily seen that by using switches such as 176 at all the positions, some positions could be allowed to handle all the calls they could handle and other positions allowed to handle their pro rata is receiving a call and before a cqllnfil' on two positions may be used for instructing new operators.

It will be understood wherever condensers are shown for shunting voice currents around relay windin that non-inductive resistance shunts may substituted therefor.

From the precedlng description, it will be clear that the system is very elastic and capable of many modifications. The de-" scribed ap aratus and means whereby a call initiating ine in any hundred group obtains exclusive control of the signal circuit of the group may be used, together with the signal circuit, for producing the line designation of the call initiating line in the receiver of of one particular operator, instead of in the receiver of one of a plurality of operators, thereby efi'ecting an economy of a paratus and switchboard space without utilizing the call distributing feature described herein.

Operating conditions sometimes require various kinds of cord 'circuits to be used at the same or different positions in an exchange,and in Part 3 is shown how this maybe done. Link connectors 'A and B can beused together and C, -D and E- can also be used together. When the link connector marked B is used instead of the already de- 'is made to the line jack. Therefore, these scribed link connector A, then when the, op-

erator inse rts answering plug 382 in a multiple jack 133 or 134 (Part 1), of a calling a line, path is given for current from battery 135 through elements 383, 384, 385, 141 or 142 (Part 1), 143 and "to ground, energizing cut-off relay 143. The signal circuit of the hundred group and the line signaling apparatus of the section is restored to normal in exactly the same way as hereinbefore described when link connector A was used.

The manipulation of listening key 386 gives path for current from battery 135 through elements 383, 387, 388 and 389 in multiple,

upper spring of key 386, 390, 391, 392, 149,

secondary of induction coil 150, 94, 117', 151,. 393, 394, 395, 396, 397, lower spring of key 386, 398 and to ground, energizing position controlling relay 395, which acts as the controlling means for receiver 94. This closes the already traced circuit through wires 159-162 but by way of wires 399-400 and contacts 401-4Q2 of relay 395, consequently, relays 158163 are energized and the numerical signal circuit changes are made as described in relation to link connector A. The operator is enabled to converse with substation 0001, inasmuchv asthe substation is connected to windings 403404' of the link connector re eating coil by way of contacts 405-4060 plug 382 and the spring contacts of jack 141 or 142. Voice currents are allowed to pass relay 395 by bridging the same with a condenser 407.

en all P s 4. s e v a a jack of the called -for line, ringing key 409 is manipulated in the usual way. i, The restoral'of listening key .386 to its normal po-- sition opens 'the,circuit through relay 395 and the same is consequently de-energ zed. Relays 158-163 are locked u as described in relation to link connector The insertion of calling plug 408 intoa line jack gives path for current from battery 135 through elements 383, upper WlIlding of recall relay 410; 411, 412, 413, 414, 415 and the upper winding of changing re- .lay 416 in multiple; 417, 418, contact of the line jack corresponding 'to 141 or 142 (Part 2), cut-off relay corresponding to 143 and to ground, energizing the cut-ofl relay. Relays 410 and 416 are not energized by this current flowing through their upper windings, but ringing lamp 411 is illuminated by. the current flowing therethrough. The continued-illumination of lamp 411 indicates to the operator that the called-for party has not responded, consequently, the operator periodically manipulates ringing key 409 as-long as the lamp remains illuminated.

When a party responds at the called-for substation, the removal of the receiver closes a circuit for direct current through the substation line, in a manner well known in the art. This gives path for current from battery 135 through elements 383, 387, 388 and 389 in multiple, 419, upper springof key 409. 420, spring contact of jack, one limb of the called-for substation line, substation apparatus, other limb and spring contact of jack, 421, lower spring of key 409; 422, 398 and to ground, energizing calling supervisory relay 389. When'contact 415 of relay 389 disengages contact 414, the circuit through ringing lamp 411 is opened. consequently, this lamp is extinguished, indicatingto the operator that the called-for substation has answered. When relay 389 is energized, relay 416 is also energized, inasmuch as the shunt circuit around the upper winding of the-latter, comprising lamp 411, is opened when contacts- 414-415 of relay 389 become disengaged and, consequently, all the current flowing through the upper winding of relay 410 now flow s through this upper winding.-

Answerin supervisory relay 424 was energized w en answering plug 382 was in-.

serted in the jack of the calling line, inasmuch as this relay is in circuit with the'line of the calling substation. 425-426 are not illuminated, as no appreciable amount of current can pass through contacts 427-428 of relay 424, lamps 425-426, and contacts 429-415 of relay 389, inasmuch as resistance 384 and the upper windings of relays 410-416 are approximately equal in resistance, consede-energizes the same, consequent Recall lamps quently, lamps 425-426 are included in'the bridge arm of a Wheatstone Bridge, the re sistanc'es of the cut-off relays being approximately e ual.

When is e receiver is replaced at either the calling or called-for substation or both, the circuit for direct current is opened through relay 424 or 389 and, consequently, the same is deenergized. This gives path for current from battery 135 through elements 430, 431, right part of winding of relay 432, 433, 434,435, 436, right winding of relay 437, 438, lower windings, of relays 410-416, and 439, 441, 427, 385, through the calling line cut-off re 440, 442, 413, 414, 415 417, 418 and to ground through the called-for line cut-oil relay, or through both, energizing relays 432, 437 and 410, and illuminating disconnect lamp 439 or 440, or both. The enerization of disconnect relay 437 gives path or current from battery 135 through elements 430, 431, right part of winding of relay 432, 433, 434,435, 443, 444, 445, 402, 400, 162, upper winding of position signal transfer relay 163, middle winding of induction coil 150 and to ground, energizing relay 163. The energization of relay 163 disconnects operators receiver 94 from the described lin'e signaling apparatus and connects the latter to the operators receiver at another position, as has-been hereinbefore described. Therefore, an operator is.not selectable by a numerical signal circuit whenever there is a link connector in use which should be disconnected. The energization of signal relay 432 .causes contacts 446-447 to become engaged, thereby short.- circuitingthe winding of the rela which y contacts 446-447- are disengaged removing the short-circuit and the relay is at once reenergized and the operation repeated. In

this manner a vibratory action of armature contact 446 is producedand the resistance of the circuit includlng the central winding of induction coil 150 (Part 2) varies in ac cordance with the resistance of the alternately short-circuited winding of. relay 432.

This produces an alternating current in the secondary of induction coil 150, a path for which is given from the left terminal of the secondary through elements 149, 392, 391, 448, 394, 393, 151, 117 and 94 to the right terminal of'the secondary. The passage of this alternating current through 0 erators receiver 94 causes an audible si nal to be produced therein which indicates to the operator that there is a connected line or lines signaling for a disconnect. Illuminated disconnect lamps 439 or 440, or both, would indicate the proper link connector to be removed. Resistance 448 is high enough so as not to appreciably shunt operatorcould wait until the test failed'to a disconnect, at the same time a positive disconnect signal is sounded .in the operators'receiver.

The path traced through relays 432-437 and the lower windings of relays 410-416 to contacts 141 or 142 of the calling line multiple jacks and thence to ground through the cut-ofi' relay, is also-aifected by the variable currentcaused by the descrlbed. short-circuiting of rela 432, consequently,

if an operator makes -t e well known busy test on a called-for line and that line is sig- .naling for a disconnect, instead of hearing the usual click in the recelver, the operator will hear a sustained tone, inasmuch as part of the variable current flowing to through the cut-off 'rela will be diverted through contacts 141 an 142 of the tested jack, contact 421 of calling plug 408 (on gaged with the jack contact when'the' busy test is made), lower spring of ringing. key 409, contact 422, and repeating C011 winding 398 to ground, thereby afi'ectlng the operators receiver which 1s bridged across repeating coil-windings387-398 by the manipulation of listening key 386. Therefore, an operator hearing this sustalned' tone or audibl signal when makin a busy test would know that the tested me was really idle and that the connecting operator would remove the connected link connector wlthm a moment or so, conse uently, the testing produce the ton or signal and then would connect to the line in the usual manner. Incoming calls would not delayed by th s action, inasmuch as the testing operator'ls non-selectable by calling lines as o the line connected to the calling plug instead of the answering lug will produce the same busy signal as t e variable current has a path through contact 418 of calling plug 408 and the testing contacts of themultiple jacks of the connected line.

If the callin or called-for parties desire -a recall, the su station receiver is removed after having been replaced, or the switchhook is depressed once and then allowed toreturn to the position it occupies when, the receiver is not resting thereon. This wouldfirst de-energize supervisory relay 424 or 389 and then re energize the'same. However, recall relay 410 would remain energized, inasmuch as .having once been-eneround ng as a listening key is in its manipulated posltlon. It willbeevident that a busy test made on 1 mgs.

lower winding, when relay 424 M389 is deenergized, it is maintained energized or locked up by the current flowing in its upper or looking winding. Therefore, path would be given for current from battery 135 through elements 430, 449, left winding of relay 437, 450, 451, 452,; and 425, 428, 427, 385 and to ground through the calling line cut-ofl why or 426, 429,415, 417, 418 and to ground t roughthe called-for line cut-01f relay, energizin relays. 449-437. The ener 'zation of re ay 437 closes the same au 1ble signal circuit as described when a disconnect was signaled. However, the additional energization of operators recall relay 449 removes the short-circuit around the left part of the winding of relay 432, inasmuch as contacts 434-435 of relay 449become disengaged; consequently, the

I increased resistance ofiered by the entire' wmdmg of relay 432 causes a greater variation in the current flowing through the middle Winding of induction coil 150 and the audible signal produced in receiver 94 "is louder than the disconnect signaL. As relay 432 is now energized by a greater number of ampere turns than it was when the disconnect signal was produced, its ar- .matur'e maybe so arranged that it will vibrate faster, thereby producing an audible signalof difi'erent tone quality, as well as of greater volume. In any event, the operator is enabled to distinguishv the recall from the disconnect signal and upon hearing the former would lance over the link connectorsin use and coats the recalling line by observing recall lamp 425 or 426 illuminated.

The described disconnect signal circuit through relay 437 is opened when answering plug 382 or calling plug 408, or both, are

removed from the line jacks, according to whether the calling orcalled-for lines or both, are si aling for a' disconnect. sequently, t e disconnect audible signal is only discontinued when there is no longer an idle line to which .a link connector is connected. r

' The described recall signal circuit relays 437-449 is opene only when calling plug 408 is removed from theline jack 0 the called for line, inasmuch as relays 410 and 416 remain energized aslong as the calling plug is in a jack, therevv being a ath for current through their upper wind- Therefore, means must be provided for discontinuing the recall signal when it i is desiredto talk to a line 'recallingand this is provided 'for by having relay 395,

which is energized whenever a listening ke 386 is manipu ated, open the circuit for hot the recall and disconnect signals when con- 'tacts 402-445 become disengaged Consequently, the recall and disconnect audible gized by the current flowing through its, s gnals canonly he produced in receiver 94 18.

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