US1492396A - Automatic telephone system - Google Patents

Description

April 29 1924.

R. G. RlcHARDsoN AUTOMATIC TELEPHONE SYSTEM 3 Sheets-Sheet 1 Inman nr- BDnFnE/lj E Ewzarsnn @TTT prl 29 [1924.

1,492,396 R. G. RICHARDSON AUTOMATIC TELEPHONE S YSTEM Original Filed Feb. 14 1916 3 Sheets-Sheet 2 IIIIIIIHII Y Y; Q A@ BUnFnRgf-E. Ezaharcfsnn I Mm..

il' 2 A n l-' April 29 1924.

R. G. RICHARDSON AUTOMATIC TELEPHONE SYSTEM 0 Filed Feb. 14 1916 YQ [IIIIIIIIIHIl HIT-U;

Patented Apr'. 29, 1924.

matas nonnnr G. RICHARDSON, orc'nircneo, inLINis, Assiciion, ',ro nU'roMAro ELECTRIC COMPANY, on oHI'oAGqTnnno'Is, noonronnron or Tumors.

AUTOMATIC TELEPHONE SYSTEM.

original application filed Febfairyi, 191e, Seriaiiio. Tenci. :renewed .nine ze, 1920, sriai NQ. 392,042, now Patent No. 1,439,124, dated- Dec'ember 19, 1922.- Divided and this application led November 6,

1922. serial No. 599,176.

To @ZZ whom t may concern; y

Be it known that I, eBonnerA G. RICHARD# son, a citizenl of the United States lof Amer. ica, and a resident of Chicago, county ofI Coolr and State of I-llinois,have*invented certain' new and useful Improvements in Automatic Telephone Systems, of which the following is a specification. 1 My invention relates to rautomatic telephone systems and as to yits/principal features relates more particularly to LlCh-'sys-f tems as employ so called-finder switchesforv connecting acalling 'line with a selectorv or connector switch. A

In systems of the above general,characfA ter the lines are dividedl into groups, and there is provided for eachgroup of lines ak suiiicient number of finder switches toy han; dle the maximum number of originating calls from that grou-p. 'Each finder may be directly connected to a selector or co-nnector switch, depending. on the sizeof the system, through the medium yof-.which a calling line, whenvlocated bya finder switch,

. may be extended into connection with a called line. ,i

One of the features disclosedand wclain'ied in this application, which is. adivisionmof my application Serial No. 78,11611tiled .Febf ruary 14, 1916, renewed June' 26,1920, Serial No. 392.042, is an improved circuit arrange. ment according to which theline relay of a selector or connector switch to which a calling line is extended is energized over a local circuit for a brief interval independent of the calling line. This arrangement renders the line relay incapable of respond ing to accidental interruptions in the subscribers line circuit which may occur dur,- ing the removal of thev receiver "(fknownas false or preliminary impulses) and thusreg mores a. source of trouble found in eX-isting systems.

i further feature of ythe invention basto do with the trunk release'circuits.'Al According to this feature the release trunk conduc-f tor' is grounded through a 'locking winding ofv anV energized relay in' oneswiteh (aiy finder` switch) to maintain the `connection],untili ground is' applied to the release trunk4 con,-

ductior at thel next switch jin the'. train L S'V4 lector orconneetor), l/Vhenthis occurs the is short circuited and the energizedfrelay in the firstswiteh fallgback. The/holding ofthe connection during the change over from one switch Ito the next switchin the series is therefore made posi tiye'and reliable, las it isv independent ot thedeenergizing time of a slow relay, as is thefcase with systems now'in' use.

y To accomplish the foregoing and otherI useful ends my invention comprises means whichwill bei hereinafterjset forth. and claimed, referencebeing had to the accompanying drawings.

`In the r drawings Figures 1 and 2, taken in order with thef'lines at the end thereof in alignment, represent diagrammatically f a ure 'ois a schematic representation of one ot the circuits show-nin Figure 5.

.f [khevsubstation A (Fig. 1) may be of the general type' of substationfshown in British Patent to T., Gr. Martin No. 1419 of 1910. Asherein represented it consists of the receiver 2, transmitter .3, receiver hook 4, ringer 5, and condenser. Being an auto-- matic substation itisfalso provided with a pairfof..impulsesprings 8 and 9 controlled bythe impulse .wheel 7,1.which in turn is con'-` tro-lled through the medium of a finger hole dialinotshown) The impulse springs and Wlieelmas shown .herein maybe arranged in the manner-l shown in BritishL GQ Dicker, 29.654;` of 1910. i

Thefline lconductors 11and12 of the sub` stationQ have allotted-to them` at the eX- change-the @1in-e' and cut-off relays 21 and bank, ,of eachiinder switch, lQ'neof these sets being Afindicated .reference characters.

45 and 46 associated with each setof finder -bank contacts; and a set of multiple bank contacts (not shown) in the bank of each connector, such as connector E (Fig. 2), which has access to the group of lines of which the line of substation A is one. The normal conductors 13, 14, and 15 extend to the latter sets of bank contacts. The func tions of the line and cutoif relays are very similar to the usual functions of these relays in other well known systems, although the line relay 21 in my system is somewhat different in operation as will appear more l fully hereinafter.

The bank contacts 37, 38, and 39 iu the bank of finder switch C are multipled to corresponding contacts in the banks of all other finder switches in the group; each line of the groupof which the line of substation A is one, of course, being multipled through the banks of these finders in the same manner. The bank contacts and 36,however, and similar contacts of other lines of the group, are not multipled straight to corresponding contacts 'in the banks of other finders, as are contacts 37. 38, and 39, but are connected in a peculiar loop circuit which will be fully expl ained hereinafter.y

The finder switch C mayl be brieiiy described as a rotary switch whose wipers have a movement in one direction only and have no normal position. ures 3 and 4, the frame of the switch ris formed of a circular base plate 200 and a ring shaped upper mounting plate 201, the two being separated the properdistance and rigidly connected by posts 202, 203, 204, and

205. Supported on bearings in the upper' and lower frame plates, is a shaft 206 to which is rigidly secured an arm 207, a ratchet wheel 210, and i'ive sets of wipers insulated from each other,one set being indicated by reference character 215. VA magnet 208. attached te base plate 200 by means of the heel piece 209, is adapted, when energized, to rotate the shaft 206 through the medium of armature 211, pawl 212, and ratchet wheel 210. The spring 212a tends to hold the pawl 212 constantly inengagement with ratchet Wheel 210. The dog 214, which also engages the `ratchet wheel 210 serves to prevent backwardorotation of the shaft 206. Y

The various sets of `bank contacts are preferably arranged in a complete circle,v

and there are shown in Fig. 3 Afifty `of these sets, by which it appears that there will Vbe iifty lines in the group to whichthe finder switch VC has access. however, is immaterial, it being easily pos-4 sible and perhaps advisable to increase the number of lines inl each group to one hundred.y It is understood that thev manner in which the iinder switch banks and wipers are shown in Figure l is purely diagram- Referring to FigL The exact number,

matic, the`l actual construction of these parts being as shown in Fig. 4. In the latter drawing the bank contacts 35439, inclusive, correspond to the same numbered contacts 1n Figure 1 and are individual to a certain line. The bank contacts 40-44, inclusive, correspond tothe wiper 40-44, inclusive, 'in Figure 1, and are preferably-complete circular strips extending around the entire circumference of the bank. Attached to the strips 40-44, inclusive, are conductors which extend to the relays of the switch, shown at C (Fig. 1). It is evident that at all times a certain set of contacts such as contacts 35-39, inclusive, will be connected to the common strips 40-44, inclusive, by means of the ve sets of wipers.

As before mentioned, each set of bank contacts has associated with it a pair of normally closed contact springs, one of these pairs being indicatedv by reference charactersand 46 (Figs. 1 and 4). The arm 207 carries an insulating piece 47 which is adapted to separate the pair of contact springsbetween which it happens to be resting. Or, in other words, no matter what set of bank contacts the wipers are resting on, the pair of contact springs associated with that vset will be separated by the insulating piece 47.

Referring now to Fig. 5, I have shown diagrammatically therein six sets of bank contacts in each of three finder switch banks, together with six starting wires and their connections in the banks. The six sets of contacts 'immediately adjacent to the line and cut oit relays at the left of the drawing are located in the bank of the first finder of the group, iinder switch C; the six sets of contacts at the extreme right of the drawing are located in the bank of the lastl iinder of the group (not shown) g while the other six sets of bank contacts are located in the bank of an intermediate finder. It is to be understood that in actual practice there may be more than three iinder switches in a group and that each finder, as already explained, will'have fifty or even one hundred sets of contacts instead of six, but it is thought that sufficient contact sets and finder banks are represented to show what is intended. vCounting from the top the three sets ofvfinder switch wipers are shown resting, respectively on the third. second and fth sets of contacts in their respective banks.` The wipers when in motion move in an upward direction, as representedk in Fig. 5.

The starting wires are indicated by reference character 230-235, inclusive. There .are as many separate starting wires as there are lines in the group and each starting wire extendsfrom the line relay of the line with which it is associated to the starting wire contact of that line in the bank of the first contact 237.

finder switch of the group. For exaniple, startiii3 wire 232 extends from a contact on the line relay ot No. 3 line to bank contact 28S, in the third set of contacts in the bankk ci' the lirst finder switch. In the saine inanner, starting wire 233 extends froin a con tact on the line relay of line No. 4 to bank contact 239 in the fourth set of contacts in the bank of the first finder switch. Also, by referring to Figure 1, the starting wire 821 associated with the line of substation A is seen extending troni contact 29 on line relay 21 to bank contact 86 in the bank of Finder switch C, which is assumed to be the ifirst switch of the group.

F roni the foregoing,- it will be clear that each line ot a group is provided with an individual starting wire extending' troni its line relay to the bank of the tirst finder switch in the group. l will now explain how the various starting wires are connected in the banks of the remaining' nder switches, Considering the starting wire 230, which is the one associated with line No. 1 (not shown), a complete series circuit which includes every set of contact springs such as 45 and 46 (Figs. 1 and 4) in every linder switch may kbe traced as follows: starting` Wire 230, bank contact 236, contact springs 270 and 271, bank contact 242banlr contact 248, contact springs 272 and 273, bank contact 250, bank contact 252, contact springs 274 and 275, bank contact 253, wire junction 300, and starting wire 231 to bank Froin this point the circuit inay be traced incre brieiiy by way of the second pairs of contact springs of the three finders in series to wire junction 301; thence by way ot the third pairs of contact springs of the three iinders in series to wireA junction 302; thence by way of the fourth pairs of contact springs of the three finders in series to wire junction 303; thence by way ot' the fifth pairs ot contact springs ot the three finders in series to wire junction 804;

and thence by way ot the sixth pairs et contact springs of the three finders in series and the dotted conductor 310 to wire junction 305, where it joins starting wire 230 lagain and forros a coniplete loop. Conductor` `310 is shown dotted to indicate that it passes through other pairs of Contact springs not shown before returning to wire junction 305. The individual starting` wires inay be considered as taps taken off troni the inain loopr circuit at the first tinder switch banlc It will be observed that the above describet loop circuit is divided into as inany sec-y tions as there are finder switches` by nieans ot the insulating pieces 290, 291, and 292 which correspond to insulating piece 47 fFiO's. 1 and The iinder switches may t be considered as each standing, whenidle,

fitjthe divisionpoint'between two adjacent sections, each finder being adapted to serve starting relay in each of the those lineswhose starting wires are tapped on to the section iininediately in front oi" that linder. There inay be but one starting wire attached to a given section or there inay be inany incre, depending obviously on the po j i Y the other finders.

For the s ot additional cleai'ness l haveshown in n iciii'et, the loop circuit and six starting wir of F 5, t ether with a hree iinders, allr unnecessary details being' oinitted. l/Vhen taken in connection with the :foregoing descriptionot Fig. 5, it is thought that F 6 will be understood without difficulty.

The relays shown at are coin inon to a group oit' finder switches and may be terined emergency startinfD and stoppingr relays. 'lyheir functions will be incre fully explained hereinafter. F igure 1, 'the iinder switch C is connected directly with the selector switch l) which maybe of thegeneral type of selector switch disclosed in Uf Letters Patent No. 815,32 granted ll'larch 13, 1906, to Keith, TErickson and Erickson; being, however, of the particular type disclosed in British patent to the Automatic Telephone lianutacturing Conipany, No. 2543 oi 1914. Among other de' tails the selector D coinprises a bank or" contacts.y arranged in horizontal rows or: levels, `which contacts are adapted to be engagedby a set of wipers, 120, 121, and 122 carried upon a shait y(not shown) which has `a vertical .inoveinent controlled by a vertiealinag'net y109, yandy a` rotary nieveinent controlled by rotary niagnet 110. rl'he operation ot the various parts ot the switchis controlled through the rne the double wound line relay 100. Means for permitting' the switch to be restored to noiinal position is provided in the release in v,cnet 105 which, upon energizing', withdi aws the ,retaining pawls troni the shaft.` rllhe contacts and 113 inake against their `refvipective springs only when the vshaft has been .raised one or incre steps troni its norinal position. The relays 1.04 and 106are slow acting, i. e., each of these relays is able to retain itsarinatui'e for an kinstant yafter itsenergizing circuit is broken.

Asis well lmown, selector ot the type shown herein may be given, access to a nurnber ot groups oic connector switches, which connectors `in turn have access to groups ofk subscribersf lines for the purpose of completing connections thereto. One ot these connectorsfis shown ai E, E .may be ot the L,ener-al type of connector switch disclosed in U. S. Letters Patent No.

V815,176 granted March 13. 1906, to Keith,

Firiclasoiiand Erickson; being, however, of the particular type disclosed in British patent to the .toinatie Telephone Manufacturing Company, 22'w other details they connector E ,comprises a leturning now to` Fig, 2. The connector.

oit 19,14. Amongk bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of wipers 160, 161, and 162, carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 143, and a rotary movement controlled by the rotary magnet 144. The usual side switch comprising the wipers 156, 157, 158, and 159 is controlled by the private magnet 147 in the well known manner. The operation of the various parts of the switch is controlled through the medium of the double wound line relay 140 which relay also serves to supply talking current to the calling line. A called line is furnished with talking current from the windings of the double wound answering bridge relay 150. The ringing relay 149 affords means for projecting ringing current over the called line to signal the called subscriber. Means for restoring the switch to normal position is provided in the release magnet 152, which, upon energizing, withdraws the retaining pawls from the shaft and restores the side switch wipers to their first position. The contacts 154 and 155 make contact with their respective springs only when the shaft has been raised one or more steps from its normal position. r1`he relays 153 and 146 are slow acting.

The connector E has access through its .wipers and bank contacts to a group of subscribers stations one of which is shown at A. The substation A may be similar in all respects to substation A and is provided `with similar individual line equipment.

For supplying current for operating and talking purposes I have shown a battery B having one terminal grounded. The battery B shown in Fig. 5 may be the same battery yor a different battery from that illustrated at B in Fig. 2. For supplying ringing current I have shown a generator R and for busy signaling purposes 1 have shown a busy signaling machine Q.

Having given a general description of the apparatus I will .now proceed to describe the operation of a system embodying the principles of my invention. For the purposes of this explanation it will be assumed thaty the subscriber at substation A (Fig. 1) desires to establish a connection withl the subscriber at substation A (Fig. 2). Inasmuch as a great dealof the automat-ic apparatus shown herein is old and well known in the art, having been fully described in the publications referred to, its operation will be described in a more or less general manner, the details being given only when they have to do in some way with the appli-v cation of the principles of my invention.

Referring now to Fig. 1, the subscriber at substation A, upon removing his receiver to initiate the call, completes a circuit which includes a Winding of line relay 21, individual starting wires 321, and a pair of starting relays in that finder switch whose wipers require the least movement in order to reach the contacts in its bank allotted to the line of substation A. Assuming that the wipers of finder switch C are already resting upon contacts individual to substation A, the above mentioned circuit may be traced as follows: ground at G2, winding 55 of relay 54, winding of relay 53, Contact 70, armature 69, contact 68, spring 67, wiper 41, bank contact 36, starting wire 321, contact 29, spring 30, contact 27, armature 25, line conductor 11, to and through substation A, line conductor 12, armature 24, contact 25, and winding 22 of line relay 21 to battery B. 1n response to current fiow in the above path, relays 21, 53, and 54 attract theirarmatures. The armature of relay 21 is adjusted with a rather long stroke and the contact against spring 32 is made before spring 30 is separated from contact 29. As a result of the latter operation, which takes place near the end of the stroke, the original energizing circuit is broken, but not before relays 53 and 54 have fully attracted their armatures. Relay 21 is enabled to complete its stroke by reason of the new path to ground by way of common relay 90 closed by armature 28 and spring 30. A temporary locking circuit for relay 54 may now be traced as follows: ground at G2, winding 55 of relay 54, contact 66, spring 63, wiper 42, bank contact 37, spring 32, armature 31, holding winding 23 of line relay 21, and winding of cut off relay 2O to battery B. The cut o relay 20, upon energizing, breaks the energizing circuit of winding 22 of line relay 21, but relay 21 retains its armature attracted by reason of its holding winding 23, now carrying current in series with the cut off relay winding.k

An instant after the temporary locking circuit of relay 54 is established by the4 energization of relay 21, the slow actingV iin relay 53 retracts its armature, thereby completing an energizing circuit for line switching relay 51 as follows: ground at G3, armature 78, contact 80, armature 74, contact 75, holding winding 56 of relay `54, armature 81, contact 82, and winding of relay 51 to battery B. Relay 51, upon attracting its armatures, bringsabout the following cir-` cuit changes. By bringing armature 64 into Y engagement with springfi and by separating the latter from contact 66, the temporary locking circuit of relay 54 by way of its winding 55 is broken and relay 54 remainsy energized by reason of its low resistance holding winding 56. By the substitution of winding 56 for winding 55, the test contact 37 and its multiples are brought sufficiently near to ground potential to make the line of substation A busy to other finder switches that may be started. Also, by

`reason of the low resistance of holding winding 23 of line relay 21, the conductor 15 and the multiple test contacts in the banks of connector switchesto which it extends are brought sufficiently-near to ground potential to make the linevof substation A busy to those connector switches. Als a further result ot the energization ot relay 51 the wiper 41 is disconnected trom relay 53 and is connected directly to wiper l10 in an obvious manner. This is done for the purpose ot maintaining the continuity ot the loop starting circuit while iinder switch C is busy. Finally, by bringing armatures 59 and 60 into engagement, respectively, with contacts G1 and 62, relay 51 extends the line conductors 11 and 12 to the double wound line relay ot the selector 1). Two energizing circuits :tor relay 100 may now be traced, one of which extends overthe following path: ground at G5, winding 103 of relay 100, contact springs and 116, contact 61, armature 59, wiper 48, bank contact 38, conductor 16, line conductor 12, substation A, liner conductor 11, conductor 17, bank contact 39, wiper L14, armature 60, contact (i2, contact springs 117 andv 118, and winding 102 of relay 100 to battery B. The second energizing circuit extends as follows: ground at G3, armature 78, contact 80, armature 74, contacti, 75, armaturel 60, contact 62, Contact springs 117'fand 118, and winding 102 of relay 100 to battery B; Ordinarily the latter circuit, which is in effect a short circuit of winding 103 and the substation A., could be dispensed with. Its purpose will appear later.

Upon attracting its armature, the line relay 100 completes an energizing circuit for the slow acting relay 104, which relay, upon energizing, prepares circuits for the vertical and rotary magnets 109 and 110 in the well known vmanner and also completes a. holding circuit which may be traced over the 'following path: ground at G6 andy contact springs and 131 Ito armature 641, where the circuit divides, one branch eX- tending by way of the winding of line switching relay 51 to battery B, and the other branch extending by way ot spring 63, wiper 11-2, bank contact 87, spring 82, armature 31, winding 23 of relay; 2l; and winding ot cut oii" relay 20 to battery B. 1t will .be observed that as soon as the above holding circuit is established the winding 56 ot relay 54 is short circuited. Upon (leenergizing, relay 5i kbreaks the last described energizing circuit of line relay 100, thereby leaving the selector 1) under the control, oi the si'lbstation A.

The purpose ot the auxiliary energizing circuit tor line relay 100 may now be seen. Should the subscriber at substation A removehis receiver and replace it, in the interval between the pulling up oit relay 21 and the pulling` up of relay 10ft oi thesclector, relay 54 would remain locked up by its winding 56, thereby maintainingtlie inder switch in a busy conditionv until the next call by substation A. The auxiliary energizing circuit for line relay 100 is provided to obviate this possibility.

Before continuing with the operation of the selector D and connector E it will be well to consider the operation in the case where no finder switch is resting upon the contacts of the calling line. le will assume that the finder switch C is idle and that its wipers happen to be nearer to the contact-s oit the line of substation A than the wipers of any other finder. It tollows then that the section ot the starting loop to which starting wire `821 is tapped will terminate in the bank contact upon which wiper 41 is resting, as explained in connection with Fig, 5. i

Upon the removal of the receiver at substationy A an energizing circuit is completed aspreviously described for relays 21, 53, and 54, except that in this case the circuit includes a portion ot the starting loop. Relay 21, upon energizing, prepares a circuit for the cut-oit relay 20 by bringing armature 31 into engagement with spring 82breaks the original starting circuit by separating contact 29 and spring 30, and

locks itself by bringing armature 28 into engagement with spring 80, all as previously described. The instant spring 80 is separated from Contact 29, relay 54: deeng ergizes but relay 5,8, being slow acting, re-

tains its ,armature for an instant thereby completing the following circuit: ground at G3, armature 78; contact 79, armature 76, Contact 77, winding of relay 52, winding of rotary magnet 50, interrupter contact springs 58and common relay 91 to battery B. Relay 52, upon attracting its armature 72 completes the above circuit over a path which is independent ot' the relay whereby the deenergization of this relay an instant later is without effect.

As soon as the circuit just described is completed the rotary magnet 50 operates to vibrate its armature 21,1 b v means o't the interrupter contact springs 58. thereby rotating the wipers 40-/1-4, inclusive, in search of the contacts ot' the calling line. Relay 52. being slow acting, retains its armature although its circuit is broken at each energization of magnet 50. During the rotation of the finder switch, wiper l1 is disconnected from` relay 58 by the attraction ot armature 69 of relay 52 and is connected at the same time to wiper i0 tor the purpose of maintaining the continuity of the starting loop. Y

`When wiper Ll2 arrives at bank Contact 37 an energizing circuit is completed for relay and cut-ott relay 20 over the follow ing path: 'ground at G2. winding ot relay 54, contact 66, spring 63, wiper 42, bank contact 37, spring 32, armature 31, winding 23 of relay 21, and winding of cut-off relay 20 to battery B. The above circuit is the sam-e as one previously described and referred to as the temporary locking circuit of relay 54. Upon attracting its armature, relay 54 breaks the rotary magnet circuit by separating armature 78 and contact 79, thereby stopping the rotation and bringing the wipers 40-44, inclusive, to rest upon contacts 35-39, inclusive. From' this point the operation is the same as described in the case where it was assumed that the wipers of finder switch C were already resting upon the contacts of the line of substation A.

Vile may now return to the selector D and consider briefly its operation. in response to the manipulation of the dial at substation A in accordance with the first digit of the desired number, the impulse wheel 7 interrupts the circuit of the line relay 100 a number of times in the well known manner. As a result of these interruptions the line relay is deenergized a corresponding number of times, sending an impulse at each deenergization from ground at G7 to the slow acting relay 106 and the vertical magnet 109 in series. The vertical magnet, in response to these impulses, steps up the shaft until the wipers stand opposite the horizontal level in which are located contacts which are 'terminals of the desired group of connectors. The relay 106, being slow acting, retains its armature during'the series of impulses and closes a circuit for the test relay 108 which latter relay prepares a circuit for the rotary magnet and locks itself to ground at G".y At the end of the series of 'impulses the relay 106 deenergizes, thereby closing a circuit for the rotary magnet 110, whereupon the wipers 120, 121, and 122 start rotating in search of a trunk extending to an idle connector. AS is well known, the rotary magnet interrupts its own circuit and also the locking circuit of the test relay at every energization, the contacts in the latter circuit, however, being short circuited by the test wiper 121 while passing over busy7 or grounded contacts. As soon, therefore, as the test wiper reaches an ungrounded test contact the test relay falls back and opens the rotary magnet circuit, thereby bringing the wipers to rest upon contacts which are terminals of a trunk leading to an idle connector switch, assumed in this case to be the Connector E. As a further result of the deenergization of the test relay 108, a circuit is completed for the line switching relay 107. which relay, upon energizing, disconnects the extended line conductors '12* and 11 from the windings of the line relay 100 and further extends them by way of Wipers and 122 and bank contacts 123 and 125, to the double wound line relay of the connector E.

The line relay 140 thereupon energizes over the previously traced circuit through substation A, and completes an energizing circuit for slow acting relay 153. Relay 153, upon energizing, prepares a circuit for the vertical and rotary magnets 143 and 144 and also completes a new holding circuit as follows: ground at G9, contact springs 170 and 171, bank contact 124, and wiper 121 to wire junction 132, where the circuit divides, one branch extending by way of contact springs 133 and 134 and winding of line switching relay 107 to `battery B, while the other branch extends by way of contact 112 and contact 111l to wire junction 135, where it joins the previously described holding circuit extending back to the finder switch C.

The subscriberat substation A may now operate his dial in accordance with the second digit of they desired number, resulting in this case in deenergizations of the line relay 140 of the connector E. At each deenergization the line relay 140 sends an impulse from ground at G8 to the slow acting relay 146 and the vertical magnet 143 in series, side switch wiper 156 being in its first position. sponse to these impulses, steps up the shaft until the wipers stand opposite the horizontal level in which are located contacts which are terminals of the line of substation A. The relay 146 being slow acting,-retains its armature during a series of impulses and maintains a circuit from ground at G10 to the private magnet 147. At the end of the series of impulses the relay 146 and the private magnet deenergize, the latter controlling the side switch wipers in the usual manner, to advance them to theirsecond position'.

rllhe subscriber at substation A may now operate his dial in accordance with the third and final digit ofthe desired number, resulting as before in deenergizations of the line relay 140. In this case, however, the line relay sends impulses to the slow acting relay 146 and the rotary magnet 144, side switch wiper 156 being in its second position.V The rotary magnet operates in response to these impulses to rotate the wipers 160, 161, and 162 until they rest, respectively, upon contacts 163, 164, and 165` these contacts being terminals of the line of substation A.

As side switch wiper 157 comes into engagement with its third position contact point, a circuit is completed from ground at G11 by way of wiper 161, bank Contact 164. and winding of cut-oli' relay 20 to battery B. The cut-off relay 20. upon energizing, disconnects the line conductors of substation A from their connections at the line The vertical magnet, in'rei relay 21. Ground at G11 also extends to multiples ot contact 164 in the banks of other connectors ot the group, thereby malring the line of substation A busy to other calls.

By the engagement of side switch wipers 158 and 159 with their third position contact points the line conductors 11 and 12 are extended to the wipers 1GO and 162, krespectively, thereby completing; the connection between the two substations. By the engagen'ient of side switch wiper 1.56 with its third position contact point, a circuit is com-v pleted 'tor the ringing relay 1&9 in series with the interrupter l, whereby ringingl current is projected intermittently out over the line of substation il to signal the called subscriber.

The subscriber at substation A has now established the required connection with substation A, and the bell at the latter substation is being; rung to attract the attention of the subscriber. "When the subscriber at substation A removes his receiver from the hook a circuit is completed for the double wound answering bridge relay 150, which relay serves to supply talking` battery to the transmitter at substation A. Relay 150, upon energizing, completes a circuit for the ring cut off relay 14S, which relay locks up and breaks the circuit oli' the ringing' relay 1119, thereby stopping the ringing'. ils a further result ot the energization oit relay 150, the incoming; line conductors are reversed as regards their connection with the windings ot' line relay 141-0. rlhis operation is without importance in the system shown herein, yalthough it is provided in case it is desired to operate lmeters or similar apparatus.

'The calling' and the called. subscriber may now converse without further effort, the voice currents taking` the path shown by the heavy lines.

Upon the completion of the conversation the subscribers will hang up their receivers. By the replacement ot the receiver at substation A the circuit ot line relai,1 14:0 is broken. Upon d eenercfizingf relay 140 breaks the circuit of slow actingv relay 153. Upon the deenergization oit relay 153, the connector E is restored to normal in the regular manner and as a further result, ground is removed trom the holdingr circuit extending back to selector D and finder switch C. The selector D is then restored to normal following the deenern'izaticn ot 'ref lay 107, and line switching relay 51 of the finder switch (li line relay 91, and cut oit relay are deenergized. whereupon all the aiviparatus will have been restored to normal position. lt should be mentioned that the line switching; relay 51 is made slightly slow acting' to insure that spring 63 will not make against contact 66 untilatter armaythe publications referred to.

the operation ot the relays shown at H which relays may be termed emergency starting and stoppingrelays. As implied above these relays perform no useful 'funci,

tion in the ordinary operation oit the system but are provided to care tor extraordinary conditions.

The' relays 90 and 91 are of rather low rresistance and are in series7 respectively, with a common locking wire ex'- A tending to vall the line relays of the group of lines and a common battery supply wire extending to the rotary magnets ot allthe inder switches of the group. The relays 92 and 98 are normally energized and are controlled, respectively, by the relays 91 and 90. Y

F rom the previous description of theoperati'on ot linder switch C, it will be clear that the line relay ot a calling line is locked upby way ot ycommon locking conductor and relay 90 during the time a finder switch isv rotating" to /tind that line. Since the rotary magnets of all the finder switches of the group are in series with relay 91, it tollows that in the ordinary operation or" the system whenever ,relay 90 isenergized relay 91 will be energized also.

Assume now that two 'subscribers vwhose starting wires happen to be tapped on to the same section of the starting loop' remove their receivers at the same instant.` lt is evident that but one finder switch will be started. Thistinder will stop at whichever line it reaches First. whereupon relay 91 will deenergize, but' relay 90 will remain energized since `the second calling subscriber still has his line relay locked up. Relay 91, being' slow acting, will pull up its armatures when the Atirst impulse of current passes through it in series with the rotary magnet and retains its armatures until the finder switch comes to rest on the contacts ot the calling` line, i heung'rounded pole ot battery B" is nowconnected to conductor 95 by way of back contact ot relay 93 and back( contact ot relay 91. Conductor 95 is joined to the starting loop at some convenient pointr and alords means for startincr another finder switch to locate the second calling' line.

We will assume now that a subscriber removes his receiver and thereby starts a finder switch hunting for his line: but before the finder switch reaches his line7 the receiver is replaced. By the replacement of the receiver the line relay ot the calling line is deenergized and battery potential from the cut-oil' relay is removed from the multiple test contacts of that line in the iinder switch banks. When, therefore, the finder which was started arrives at the contacts ot the line in question, its test wiper finds no battery potential and the iinder switch is unable to stop, but will continue to rota-te indefinitely. I provide, however, a conductor .indicated by reference character 96 which at this time will have battery potential upon it by way ot back contacts of relays and 92. Conductor 96 is joined to one or more multiple test contacts in the finder banks and affords means for stopping a rotating` tinuer switch when there is no calling line w iting to be served.

It will be seen from the foregoing that I have provided a very eiiic-ient method of starting finder switches in a system of the general 7pe described, by which the movement oi' the finders is reduced to a minimum; and it will be seen Jfurther that I have provided certain new and advantageous circuit arrangements for accomplishing the foregoing and other beneficial results, thereby tending to increase the general serviceability ot a finder switch system.

While I have described in the foregoing certa-in specific embodiments of my invention,I do not wish to be held strictly to the iorms shown herein, for various adaptations will no doubt suggest themselves to persons skilled in the art. I desire, theretore, to include and have protected by Letters Patent all Jforms and modifications of my invention which may come within the scope of the appended claims.

I claim:

l. In a telephone system, a line, an automatic switch, a controlling relay for said switch, a iinder switch operable for extending said line into connection with the controlling relay of said switch to complete a circuit therefor, said controlling relay remaining deenergized until the line is found, and means in said finder switch responsive to the linding of said line for completing a preliminary energizing circuit for said controlling relay.

2. In a telephone system, a line, an automatic switch, a controlling relay for said switch, a iinder switch operable for extending said line into connection with the controlling relay of said switch to complete a circuit therefor, means in said finder switch for completing a second circuit for said controlling relay, and means under the control of said relay 'for breaking said second eircuit. j

3. In a telephone system, an automatic switch, Ya trunk line terminating in said switch, a line relay in said switch bridged across the said trunk line, means for connecting a calling line with said trunk line, means eliective when the connection is established for automatically completing a local circuit for said relay over a talking conductor ot' said trunk to energize the said relay independent of the calling line, and means for opening said local circuit after a predetermined time interval.

l. In a telephone system, an automatic switch, a trunk line terminating in said switch, a line relay in said switch bridged across the said trunk line, means for eX- tending a calling line to said trunk line, means for automatically completing a local circuit for'said relay over a talking conductor of said trunk to energize the said relay independent o the calling line, and means operated responsive to the closure of said local circuit for opening said local circuit.

5. In a telephone system, a trunk line, an automatic switch in which said trunk terminates, means for extending a calling line to said trunk, a relay connected to said trunk and adapted to be energized over the two sides of the calling line in series, means actuated when the calling line is extended to said trunk for automatically closing a local circuit for said relay including a talking conductor of said trunk, and means controlled by said relay for opening said local circuit.

6. In a telephone system, a calling line and a called line, a switch controlling device on said calling line, means including a subscriber controlled automatic switch for eX- tending a connection from said calling line to said called line, means responsive to an initiation of a call by a subscriber on said calling line for connecting said calling line and said switch together whereby said switch is placed under the control of said switch controlling device, and means at the exchange for closing a shunt around said switch controlling device for an interval after the connection is established.

7. In a telephone system, a calling line, trunk lines, an automatic switch controlled over the calling line to connect the same with an idle trunk line, a locking circuit for retaining said switch in operated position established when the line and trunk are connected, and means operated automatically and independent of the calling line for opening said locking circuit.

8. In a telephone system, ga calling line, trunk lines, an automatic switch controlled over the calling line to connect the same with an idle trunk line, a locking circuit for retaining said switch in operated. position established when the line and trunk are connected, a relay connected to each trunk, means 'tor closing a local energizing circuit for the relay associated with the trunk in calling line.

10. In a telephone system, a trunk line,

terminating in an automatic switch, a line relay in said switch bridged across the talking conductors oit said trunk line in series with the exchange battery, a second switch for connecting a calling line with said trunk line, and means in said second switch for grounding one of the talking conductors of said trunk line and for maintaining said conductor grounded for an interval after the connection is established, whereby the placing of the said line relay under the control of the calling line is automatically delayed.

11. In a telephone system, a trunk line, terminating in an automatic switch, a line relay in said switch bridged across the talking conductors of said trunk line in series with the exchange battery, a second switch for connecting a calling line with said trunk line, a local circuit for said line relay including one conductor of said trunk line, and means in said second switch for maintaining said local circuit closed Jfor an interval after the connection is established.

12. In an automatic telephone system, two serially related automatic switches for use in connecting a calling and a called line, a trunk line extending between said switches, a release trunk conductor included in said trunk line, means in the first switch for grounding said conductor, means in the second switch for groundingl said conductor thereafter, and means in said irst switch responsive to the grounding of said conductor in the second switch for removing the ground in the first switch.

13. In a telephone system, two serially related automatic switches for use in connecting a calling and called line. a trunk line extending between said switches. said trunk line including a release trunk conductor. a self locking relay in the first of said switches having a locking winding through which a holding ground is supplied to said conductor, and means for grounding said conductor in the second ot said switches. whereupon the said locking winding is short circuited and the relay is deenergized to open its locking circuit.

14. In a telephone system, a subscribers line. two serially related automatic trunking switches for' extending said line when calling, a trunk linel extending between said switches, said trunk line including a release trunk conductor, a cut-off relay for said line, a holding circuit for said relay including said `conductor, a locking relay in the irst ot said switches having a locking winding through which a holding ground is supplied to said conductor to maintain thecutofi' relay energized, and means tor grounding said conductor at the second of said switches, whereupon said locking winding is short circuited and the said locking relay is deenergized to interrupt its locking circuit.

15. Ina telephone system, a line, two se'- rially related automatic switches Jfor extending said line when calling, a cut-oit' relay tor said line, a self locking relay in the first ot said switches, a circuit for said cut-oli' relay including the locking winding ot said locking relay, and a relay in the second ot said switches for shunting said locking winding by completing said circuit over a diiierent path.

16. In a telephone system, a line. a trunk line, an automatic switch for connecting said line and trunk line, a switching relay in said switch for closing the connection, a release trunk conductor, over which said switching relay ismaintained energized, a relay in said switch having a locking winding through which a battery potential is applied to said conductor, and means in said trunk line operative after the connection is established for placing substantially the same battery potential on said conductor whereby said locking relay is shunted and deenergized.

17. In a telephone system. a train of automatic serially related switches for connecting a calling and a called line, a release trunk conductor for maintaining said switches in operated position. a relay in one switch having a locking winding for supplying `ground to a section ot said conductor for an interval during the setting up of the connection. and a relay in a succeeding switch for directly grounding said conductor to short circuit and d'eenergize said first relay.

18. In a telephone system, two serially related automatic switches for setting up al connection, a switching relay in the first switch for closing the talking circuit at said switch, a secend relay in said switch having an energizing winding and a locking winding, means Jfor closing a temporary circuit through the energizing winding, a circuit for said switching relay including contacts of said second relay and it-s locking winding, and a relay in said second switch for shunting said locking winding.

19. In a telephone system. an incoming line, a plurality of outgoing lines, automatic switching mechanism for interconnecting said incoming line with any of said outgoing lines, a holding 'circuit completed when said incoming line is connected to one of said outgoing lines, means in said holding circuit for temporarily bringing together the two sides oit a seized outgoing circuit, means responsive to said operation for initiating the release of said seized outgoing circuit, and other means normally eii'ective to prevent said releasing opera-tion.

20. In a telephone system, an incoming line, a plurality of outgoing lines, a switch for interconnecting said incoming line with one of said outgoing lines, an impulse relay connected to one side of the connected outgoing line, a holding circuit for said switch established when the connection between the incoming and outgoing lines is completed, a slow releasing relay in said holding circuit, means controlled by said slow releasing relay for closing the operating circuit of said impulse relay independent of said incoming line, means responsive to the operation of said impulse relay for initiating the release oi said outgoing line, and other means including a second energizing circuit for said impulse relay extending through said incoming line for preventing said releasing operation.

21. In a telephone system, a calling line, trunk lines, an ,automatick switch controlled over the. calling line to connect, the samev with an idle trunk line, means operating automatically and independently of the calling line to initiate the release of the connected trunk line, and means normally controlled over the calling line for preventing such releasing operation.

22. In a telephone system, a calling line, trunk lines, an automatic switch controlled over the calling line to connect the same with an idle trunk line, means for temporarily holding said connection independent of the calling line, means operating automatically to disable said holding means to break the connection, and means normally effective to prevent the breaking of the connection in case the calling subscriber continues with the call.

23. In a telephone system, a calling line, trunk lines, an automatic switch controlled over the calling line to connect the same with an idle trunk line, means for temporarily holding said connection independent of the calling line, means for transferring the control of the holding means to the calling line in case the calling subscriber continues `with the call, and means operated automatically for disabling said holding means to release the connection in case the calling subscriber hangs up his receiver before the control of the holding means is transferred.

RODNEY GnRICI-IARDSON.

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