US1681215A - X t telephone-exchange system - Google Patents

Description

Aug. 21, 1928. 1,681,215

' W. G. BLAUVELT TELEPHONE EXCHANGE SYSTEM Filed July l5, 1927 7 Sheets-Sheet 1 //v VENTDR 'W/LL/A 6. 52A war 5r Arm/WE),

iAug. 21,1928. 7 1,681,215

w. G. BLAUV ELT TELEPHONE EXCHANGE SYSTEM Filed July 15, 1927 7 Sheets-Sheet 2 /NVENTOR WILL/AM 6? 5L4 war ATTHBNEK Aug. 21: 1928.

F/aJi 7 1,681,215 w. G. BLAUVELT TELEPHONE EXCHANGE SYSTEM Filed July 1 5, 1927 7 Sheets-$heet 3 /NVEN7'0/? WILL/AM G fiLAz/var Br $992k A 7'7'DRNE r Aug. 21, 1928.

. W. G. BLAUVELT' TELEPHONE EXCHANGE SYSTEM 7 Sheets-$heet 4 /NVENTOR 5 WILL/AM G BLAWELT.

A TmR/vEr Aug., 21, 1928. W. G. BLAUVELT TELEPHONE EXCHANGE SYSTEM Filed July 15, 1927 '7 sheets sheet 5 /A/VEN7'0/? W/LL/AM 6? 514014427 5r A TI'URNEY Aug. 21, l928 1,681,215 w. G. BLAUVELT TELEPHONE EXCHANGE SYSTEM Fild Jvly 15, 1927 sheets sheet s fill Enron WILL/AM 5 BMUVELT Arramwr- Aug. 21, 1928.

' 1,681,215 w. G. BLAUVELT TELEPHbNE EXCHANGE SYSTEM Filed July 15, 1927 "r Sheets-Shed .7

//vv/v ran W/LL/AM 6? BLAUVELT momma-Y been initiated Patent-ed Aug. 21, 19228.

stares resins PATENT OFFICE.

WILLIAM G. IBLA'UVELT, OF NEW YORK, N. Y., ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A GQBJL OEATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed July 1,5, 1927. Serial No 206,088.

This invention relates to telephone exchange systei'ns, and more particularly to such systems wherein telephone connections are established by J'neans of mechanical switching devices. a

The invention is in the nature of an advancement in the art 01 automatic switching devices, and has for its object the provision of new and improved methods of and means for establishing telephone connections automatically. v

In attaining this object the invention employs the general idea of a common driving mechanism, in conjunction with a plural I of mechanical operators or plug carrier which serve the terminals of trunk lines located in a screen type terminal bank,

According to the general aspect of the invention a team oi? mechanical operators or plug handlers is provided, one on either side ot the multiple frame adapted to serve plugs individual to the trunk lines i ncon'iing to the terminal bank in such. a manner that a plug individual to a trunk on which a call has removed from its normal seat, carried across the face of the terminal bank and inserted at the crossing points of the particular incon'ling trunk and an idle oi ling trunk of a desired group. Toetfeet this operation a tinder carriage, to

which a plug handling" device is removahly associated, moved vertically by means of a power belt to which it is permanently secured over the pin of a group of incoming trunks until the plug; associated with a callinn; incoming trunk is reached, whereupon a pantograph, secured to a vertical bridge or frame actuated to cause the plug handler to seize the selected plug; the pantogrraph then restores,and the plug handler withdraws the plug; tron'i its normal seat, whereupon the vertical bridge is moved horizontally a -ross the terminal hank, cai ing the plug handling device to the term lilS of an idle trunk in a desired gr up (it out ining trunlto. l he panto rraph is then i'cnctuated to cause the plug handler to c in the multiple bani: at the point of intersection of the incoming trunlt and a selected idle outq'oinp; trunk. Followingthe establishme' t of the-connection the plug handler is r issociated with the finder carriage and placed in readiness to serve other incoming trunk plans. [it the termination of a set up canoe tion and when Ci lhne' subscriber re J. i i i to oi the plug and insert it leases the incoming trunk, the equipment heretofore employed in placing); the plug in the multiple bank is re-actuated in acert-ain sequence, to cause the plugto be ren'ioved from the multiple and returned to its normal seat. y

1n the preferred embodiment of the invention there are twenty movable plugs, a plug on one side of the bank being; paired with a plug on the opposite side of the bank to serve as a selector switch, so that each frame conuirises a group of twenty selectors, each selector having two plugs. lVhen the incoming trunks are idle the plugs are located in plug seats on one end of the multiple bank. A team of two plug carriers is provided tor every twenty incoming trunks, one op itor on each side of the frame. The pc r for operating the apparatus is supplied through a continuously revolving, main sha'tt keyed to which are a plurality of beveled gears. Idler gears are carried on magnet arn'iatures and may be meshed with the main shaft gears for operating steel power belts to which are attached the finder carriage for vertical motion, and the movable bridge for horizontal motion.

A particular feature of the invention resides in the provision of a circuit arrangement whereby one of a team of plug carriers, upon reaching; a certain stage in extending a connectiom causes another plug carrier to be placed in position to handle the next call incoming to the terminal bank.

This feature is ell'ectcd by a certain series relation between several can'is of the sequence switches associated with the plugcarriers whereby a sequence switch employed in set ting up and ital-King down a connection waits in the waiting allotment position until another plug carrier reaches a certain stage in extending; another connection whereupon .it is moved into the allotted posit-ion to be employed in the next connection.

Another ffQZLtlTllBOf the invention resides in the provision of a manually operated key for each mechanical operator, the actuation o'if either of which causes the carrier associated therewith to be rendered inactive to ex tend calls incomii'into the terminal bank but allows it to take down connections it has already been instrumental in setting up.

A thorough understanding of the switchin mechanism embodying the above and other features oi this invention, and its operation,

will be had from the following detailed descriptions made with reference to the accompanying drawings, in which:

Figure 1 is a .tront View of the screen type terminal bank, schematically represented, and its associated switching mechanism;

Fig. 2 is an end view of the switch partly in section taken along the line 2-2 of Fig. 1 and looking in the direction of thearrows;

Fig. 3 is a sectional View 01 the switch taken along the line 3-3 of Fig. 1, looking in the direction of the arrows, and shows the equipment on both sides of the switch frame; V c

Fig. a is a sectional vie i takealong the line 4l4l of Fig. 1 and looking-fin the direction of the arrows;

Fig. 5 is a fragmentary view of a portion or" the switching mechanism showing the finder carriage and'the manner in which the plug carrier is associated therewith;

Fig. 6 :is a side view of the plug carrier or plug handling device in its normal position;

Fig. '7 is a plan view,partly in section, of the plug handling device in normal position, showing its position relative to that of a plug resting in its seat on one end of the multiple; I

Fig. 8 is a side view of the plug handler when in engagement with a plug, prior to the removal of the plug from its seat;

I Fig. 9 is a plan view of the plug handler in the same position as shown in Fig. 8;

Fig. 10 is a plan view of the plug handler after having removed, a plug trom'its seat;

Fig. 11 is a fragmentary section of the ratchet wheel which is a part of the plug handling device;

Fig. 12 is a partial top View or the multiple bank showing a plug inserted on each side i of the bank and the manner in which the plugs are supported in the multiple.

Fig. 13 is an end'view of the multiple bank as disclosed in Fig. 12;

Fig. 14: is a top view of the multiple Sl10\ ing a plug on the right, in its normal seat and its associated. off-normal springs operated, and the plug on the lettwithdrawn from its seat and its associated off-normal springs in'norma] position; and

Figs. 15 and 16 are the electrical circuits employed in connection with the switching mechanism.

The first detailed description will be directed to the switch structure in general, with an exact enumeration of the various elements which go to make up the switch, their relation to each other and their construction. The second description will embody the workings of the electrical circuits which are employed in eflecting the operation of the switch.

Like numerals indicate similar elements throughout the several views.

Referring in general to Fig. 1 and Fig. 2,

the screen type multiple bank is mounted on the switch frame in any suitable manner. The screen type multiple bank, as the name implies, is a screen 01 vertical aiulhorizontal wires woven in a manner similar to window screen, except that the horizontal and vertical wires are insulated from each other.

, to an individual commutator segment S (see Fig. 15) and are used in trunk hunting as will hereinafter appear.

Connections through the multiple are made by plugs 101, which, inserted at any cross point, connect the tip, ring and sleeve wires of an incoming trunk respectively to the tip, ring and sleeve wires of an outgoing trunk. Figs. 12 and 13 clearly show the manner in which these connections are made, as does the schematic representation of the plug in Fig. 15. It will be noted that the horizontal wires are bared, and the vertical wires insulated, the insulation being cut away at the cross points to expose the wires to the plug contacts.

When the plugs are in their respective seats, they are supported as shown in the upper portion of: Fig. '7 and also in Fig. 13. Each plug is provided with a slot which cuthe extended portion or flange of the frame piece230, and its spring contacts ongage the horizontal wires between the first set of vertical wires and the frame member 230.

The power for operating the apparatus is supplied through a continuously revolving main shaft 107 on either side oi the switch frame. Keyed to each shat't 107 are six bcveled gears 108, 109, 110. 111. 112 and 113. Idler gears 11 1, 115. 116, 117. 118 and are carried on the a-rmatures 0t magnets 120, 121, 122, 123, 121 and 125. l\ ectively. which. upon operating, cause their associated idler gears to mesh with the main shaft spurs to perform functions as will hereinafter appear.

Upon the'operation of magnet 120 (Fig. 2). the idler gear 110 meshes with the main slur ft gear 113 and also with the gear 120 associat ed with the sequence switch 127. The operation of magnet 121 causes idler gear 113 to mesh with main shaft gear 112 and also gear 128 to mesh with the gear wheel 129. whereupon the power from the main shaft 107 is transmitted to the countershait 130. on which a pulley for the power belt 131 is rigidly mounted. The front hall of the power belt 131 thereupon is moved from left to right,

emma assuming the main power shaft 107 to be r0- tated in an anti-clockwise direction, when looked at from the top. The nn-pose tor this movement 01'' the belt 131 will hereinafter be set forth. In like manner, the operation of magnet 122 causes the idler gears 117 and 132 tomesh with gears 111 and 333, rcspectivel the toriner associated with the power shaft 107 and the latter with shaft 130, so that the belt 131 in this case is moved from right to left. Upon the operation of magnet 123, idler gears 11.0 and 133 mesh with gears and 13 1, respectively, to cause the power from shaft 107 to beimparted to shaft 135, on which a pulley 130 for the power belt 137 is securely mounted. Thereupon the belt 137 is moved downward. In like manner, the meshing of gears and 138 with gears 109 and 13 1, respectively, causes the belt 137 to be moved upward upon the operation of magnet 12 1. The purpose of these D'lOVCl'llGllliS of power belt 137 will appear from later description.

l i hcn magnet is operated, gears 11 1 and 139 mesh with gears 1.08 and 1 10, whereupon the sha1't14t1 on which the gear 140 is mounted, rotates, causing the cams 171 and 172 secured thereto, to impart a downward movement to the blade 173, againstthe no tion of restoring springs 210 and 211. The blade 17 3 extends across the top of the '1 rants and is rotatably mounted at the peinhrfillt) and 301.

Attached to the power belt 137, at 212, is a finder carriage 1 12 which rides on rollers along the vertical guides 1 13. Attached to the carriage 1 12 a set of contact brushes 14: 2

which travel over the contacts in the finder bank 102, in search of a particular incoming trunk, as will hereinafter be described. Dur- .ing the process of finding, a plug handler, or

mechanical operator l io is coupled to the finder carriage 1 112 and is moved upward or diiwnward with it as the power belt 137 is moved. To efiicct this coupling, the carriage 1/12 provided with two extending pegs 213 and $214- which lit into corresponding holes 215 in the plug handler, as shownin Fig. 5. A cc itering roller- 1415 used for centering the carriage 1 12, rides in a corrugated rack 147 and is attached tothe carriage 1412 just above the tinder brush 1 1 1. V7 hen power is applied to the vertical belt 137 by 1 1e operation of the armature ot l'nagnct 12d, the idler gear 115 is brought into mesh with the main shaft gear 109, and gear138 with gear 13 1 whereupon shaft the finder carriage 1 12 iipward. In the proccss 0'1 finding, magnet 12-1 is deenergized and its armature restores just before the centering roller 1 1:6 drops into a slot in rack 1 i7, so that the final movement of the carriage is controlled by the centering roller 1 16. This insures pertect alignniicnt of the plug handler and the contacts 01 acalling incoming trunk in the finder bank.

135 rotates and the power belt 137 moves Attached to the horizontal power belt 131 at the point 153 is a movable bridge or vertical tran'ie which comprises the guide rails 15.1.

and 152 which are fastened together by the two cross pieces 15 and 155 and on which the its, permanently securet to the plug before the former is actuated to seize the plug.

The frame or bridge is provided with a l'OllQl 353 at the bottom, which rides on the horizontal rail 150, and a similar roller .161 (Fig, 3) at the top, which rides on the guide rail. 160. The guide rails and 100 provide for the horizontal movement of the bridge across the multiple bank. its lltklGllllJGffOlG stated, the plug luindler 1 15 is removably associated with the tinder carriage 1-112, shown in l ig. 5.

Attached to the bottom of the vertical bri member 152 nearest the frame is a set ojt contact brushes 167. These brushes make contact with the comnu'itator segments of commutator 168 as the bridge is moved over the niultiplc lor a purpose to be described hereinafter.

fr pantograph com irising the vertical member 16 1: and the two horizontal members and 10 S is pivotally mounted on. the vertical bridge, the vertical member 16 1 bearing against a roller 109 on plunger 170 of the pin handler 1 15. The pantograph is carried by the bridge in its movements across the multiple. "lne pantogra h is operated when the armatue of magnet actuated to cause idler gears 114s and 139 to mesh with gears 10S and 1 10, respec ively. The meshing of, gems 130 with gear 140 causes the shaft 1 1:1 to rotate, whereupon the cams 171 and 172 mounted thereon drive against the blade .173

which extends the entire length of the frame,

and causes it to cug 3 projection 1.74 ot the pantograph and 1110i. it downward, so that the vertical member 16-11; rides on the roller 169 and forces the plun r 170 o the pin h dlcr 141-5 inward to e1 a s of a plug 101 as will next be i The plug handler 14.5 cons 177 provided with a slot 278 in which a. plunger 170 ada ited to move uiulcr the caiiuning action ot the vertical member 10-1 01 the pantograph, on the roller 109. it spiral spring holdsthc pluu in nori'nal position, as shown in Figs. 6 and 7. Pivotally mounted on the plunger 170 by means of a screw 173 15 a ratchet wheel 170 which con'ipilses two 1550 and 181 audtwo stops 'iing siu'jlaccs also acting aeement with the ratchet litl ' rotate during its sliding movement.

vpli' oted tot-heplunger 1'70 at 191- is a plug pawl 185 having a hooked end adapted to enplunger-in the same direction and the ratchet awls engage the stops to cause the wheel to Also gage-a correspondingly hooked end 01 the plug 101. Normally, as shown in 1F ig. 7 the plug pawl rests on the cam 180 and is raised in the position shown.

VVhenthe plunger 170 is forced inward due to the actuation of magnet 125 and the subsequent action of the pantograph, the ratchet wheel 179 being attached thereto moves in the samedirectioh,slidingbodily over the frame 177. The ratchetpawl 181 engages the stop 182 causing the ratchetwheel 179 to turn less than a quarter turn due to-the length of the inward stroke oil theplunger,during which interval the plug pawl 185 rides oll' cam 180 and drops-into the'position'shown in Figs. 8 and 9 under the-action olf's prin-g' 200'. The hooked end of the plug pawl 185 thereupon engages'the hookecl extended portion of plug 101.

When the plug 101 .is engaged by the plug pai'vl185 'andinagn'et 125 deenergiz'ed, as will appear from a later circuit description, the pantograph is "returned to normal and the plunger-170 is forced outward under the re 'storingaction of spring 175, which was compressed when the plunger was forced inward. The plug pawl 185 in moving outward with the plunger 170 removes the plug 101 from its norinal'seat. The plug 101 is now in the position shown in Fig. 10, its hook end resting in the slot 278 and engagedbythe hook end or the plug pawl 185." 011 the outward move ment of the plunger 170,-the pawl 199 engages the step 183, iusing the ratchet wheel to complete the quarter turn started on the inward stroke of the plunger, so that the ratchet wheel "assumes a position similar to that shown in except that cam 180 occupiesthe positionot stop 183 and cam 181 that or stop 182.

v The plug handler must now deposit the plug at another position in the multi'ale. In

the descriptionofthe operation oi the switch to follow, it will'be pointed out how the plug handler after removing the plug from its seat is carried across the multiple to the terminals of an idle trunk, and for sin'1pl1c1t it will now be assumed that this operation has erated, causing the pantograph to function and force the plunger170 of the plug carrier 1 is in the act of grasping aplug in its seat,

' the plunger 170 requires a relatively short stroke as the. plug when in its seat IS nearer the plug handler than when it is in a position v in the multiple banln To provide for this necessity, the blade 173 is provided with a raised portion 201 immediately above the home position of the plugs. This results in i'ectcd. The magnet 125 is again op-' the blade 173 is not provided with raised portions, sothat the plunger has a longer stroke at these positions and consequently the ratchet wheel turns a greater distance, and in reality-a run quarter turn as will now be described.

'lhe ratchet pawl 199 is now in engagement with stop 183 and pawl 181 with cam stop 181. As the pantograph causes the plunger 170 to bc'inoved inward due to the rc- :tuation of magnet 125, the ratchet wheel 1) turns a full quarterturn. As the ratchet wheel turns, the cam 181 rides under the plug pawl 185 and starts to raise it out of engagement with the plug. The cam has been so designed that the plug pawl is free of the plug before the hookeclportion thereof leaves the slot 178 and after the plug springs have engaged the trunk wires. In this manner the plug insured against falling. The plunger in continuing its'inwai'd' stroke forces the plug further into the multiple until a position as shown in Fig. 12 is reached. The cam181 now occupies the position of cam 180 in Fig, (i and the cam 1'80 and stops 182 and 183 occupy correspomling positions, and the ratchet wheel itself is positioned at the further end of the frame 177 so that the ratchet pawls will be resting on the sideso'f stops 182 and 183. l Vhen the pantograph is again restored to normal under the action oi? spring 350, the plunger 170 is again forced outward under the action of spring 175, whereupon the ratchet wheel 179 slides back into the posit ion shown in Fig. 6, but it is not rotated, the several cams and stops assuming the positions just given them in the previous paragraph.

T 1e electric circuit again functions a ud the plug handler is carried back on the vertical bridge across the multiple and is again connected to the finder carriage.

After a call has been completed and the incoming trunk released, a complete cycle of operations similar to'those just described, but

in a reverse order, performed, whereby the plug employed in the establislnnent of the connection is remoi e'd from the multiple and returned to its seat, and since these (meratioiu: are identical with those described, it is believed unnecessary to repeat the description.

A set of contacts 188 is carriciil by the plug handler, the contacts being normally held open-due to a camming action of the plug, so

that the contacts are closed between the time a plug is deposited in the multiple bank and pick-ed up again by the plug handler.

Secured to the linde'r carriage is a tripping mechanism 512 having extending portions 598 and 599 which engage the transfer switch 510 at certain times during the travel of the carriage. The tripping element 512 is so pro portioned relative to the distance traveled by the carriage 142 that when the carriage reaches its uppermost position on its upward travel, the extension 598 engages and throws the switch 510 to cause a circuit change, whereby the carriage is immediately started on its downward travel. The extension 598 does not override the switch 510, so that it does not re-actuate the switch when the carriage starts down. The extension 599 of the tripping mechanism is provided to cause the carriage ll2 to be started upward when it reaches its lowermost position on its downward travel.

The detailed operation of the system disclosed is as follows, particular reference being made to Fig. and Fig. 16, the former being placed immediately above the latter in tracing the circuits Assinning thata call has been initiated by a subscriber at a distant substation and the call has been extended to the incoming trunk 500, itwill be now described how the connection is further extended to an outgoing trunk, such as 501. /Vhon the trunk 500 was selected for use, the connection, which has so far been set up in the usual manner, will cause the sleeve 502 of trunk 500 to be grounded. A circuit is thereupon established extending from battery, winding of relay 503, right-hand winding of relay a, contact l-l2 of the oil-normal springs 106 located at the front ofthe multiple bank, contact N-1 of the oil-normal springs 106 located at the rear ol; the terminal bank to ground on the sleeve wire 5020f trunk 500. llelays 503 and 50 i operate in series in this circuit. Belay 50-1 in operating locks up to ground on the sleeve 5052 by way of its left-hand winding, front contact and inner lett'hand armature and conductor-505. At its outer left-hand armature and front contact, relay 504 causes battery to be connected tothe contact 506 oi the tinder bank over a circuit extending from battery through resistance 50?, contacts N-i and l t-*3 ofl' oil-normal swings 106, :liront contactand outer letthand armature of clay conductor 500 to the contact 506 of the or bank.

lay 503 in operating connects ground to art lead 500 which cause start relay 600 to operate over an obvious ci euit. Assuming the sequence sv s -h 12? (Fig. 1) to be in position 1, which will be the case when neither V of the mechanical operators on the iiront or rear of the bank frame in use, a circuit is established extending from ground, front contact and armature or start relay 600, normal. contact of key 601, G cam oi sequence switch in position 1, coi'uluctor 603, back contar-t and middle lelthand armature oi rolay -12, c-znnjluctor (505, right hand winding 1-1 layb06 to battery and ground. Relay 006 operates in this circuit and locks in a circ extending from be. tery, right-hand winding; oi? relay 606, inner right-hand arma- 600, O cam of soon.

ture and front contact of relay 606, conductor 607, I cam of sequence switch in positions 1 to 2, conductor 608 to ground by way of back contact and inner left-hand armature of relay 609. At its inner left-hand arn1ature and front contact, relay 606 completes a circuit extending from ground, inner lefthand'armature and front contact 01" relay 606, conductor 61.0, D cam of sequence switch in position 1, winding of sequence switch magnet 120 to battery and ground. The operation of magnet 120 in this circuit causes the gear 119 to mesh with the drive shaft gear 113 and sequence switch gear 126, whereupon the sequence switch moves into position 2. In position 2 a circuit exists extending from ground on the back contact and outer letthand armature of relay 609, outer armature and front contact of relay 606, cam J of sequence switch in position 2, conductor 612, contact 61.3 of transfer switch 510, winding of updrive magnet 12 1 to battery and ground. lit will be noted that the contacts 613 of trans-Hr switch 510 will be closed at this time as the tripping element carried. by the finder carriage 142 will be at its lowermost position, having opened the downdrive contacts 614 on a previous movement of the carriage 124. The mechanism is so arranged that carriage 142, after having served a pa ticular incoming trunk, remains at the level of the trunk served, so that when called upon to set up or take down another connection on a trunk at a level below that at which it is resting, it will be moved upward until the transfer switch 510 is actuated to send the carriage downward in search of the trunk requiring service. Upon energization', updrive magnet 124: causes idler gears and 138 to. mesh with drive shaft gear 109 and gear 13 1,respectively, whereupon shaft is rotated and power belt 137 to which the tinder carriage 1&2 attached, is moved vertically, so that the tinder JIUSllGS 51-1, and 510 of the brush; a; tic-ally and test over Under this condition the iii 11 oat- 'fi on'the bank contacts andlinds it on con-- tact 506 as hereii'lbeiliore described, whereupon relay 600 operates in a circuit from contact 505", brush wiper 516. rmuluc ce switch in pos' aion 517, l; cam of re condurtor 6153,14: hand winding o re ay ace switch in porn Urea the ep reti n of Plus ne 195 ll-lzflildjlfiil ineshwith drive shaft gear an 1&0, respectiyely whereupon I .is rotated, causing the-rams 171 and 172 h) .e cage the'blade 178. andtorce it clownod tl' ra portion 200 ei'igaging extensicn re pautograph, whereupon the vertical member 16 1 forces the plunger associatec with re plug handler inward, to seize tlieplu ciat el-with theincoining trunk 5.00 in ainanneri hereinbeiore described. Relay 609.17el es when the sequence switch ino gg ouf-o' osition 2. li hen the finder. on the t'ronto the frame has found the calling trunk an the corresponding plug has been li i ted, iiq iri-1 1 springs associated therewith are actuated, il 2, l l4-, ON-2 and ON=4,. being ope atec. iii-*2 opens the circuit b0 the operating windings of relay e y 50 8-. nary 5 0 l ren iains oper- A Linden sleeve502, throughits loclring win ding, 5,03 r eleases. N 4 re .0 e attery m he nd r h mina y nit equipment isnowawaiting the sender Re lay 606 now; operates inacircuit extending from grounded battery, left-hand winding-,1.of *elay606, Jfcam of sequence switch in position 3, conductor 616, finder brush ala and 'its associated finder. COIllLiICt, tip conductor of trunk 500, over the fundamental circuit to the sender in; .theusual man no]; ring conductor-of trunk 500, contact and brush 515 ofthe finder, conductor 611, cam

:i of sequence switch in position 3,conductor.

618 to ground over the back contact and outermost left-hand armature of relay 604, Relay 606 locks over its inner right-hand armature and front contact, conductor 60,7, canil of sequence switch in position 8, conductor 616,

tip of trunk500, over-the fundamental circui o ring conductor of trunk 500, H ca. of sequence switch in poslt- ions 3 and 4 conductor 6 18-, baclr contact and outermost lett;hand armature of relay 604: to ground liihhenrela ii 606 operates, the sequence switch magatlQO is energizedin a circuit extendingjfrom ground, inner left-hand armature and front contact ofrelay 606, conductor 610,

'1; D cam in posit-ion 3,- windingof magnet 120 restoring action of s rings 210 and 211. The

pantograph thereupon restores and the plug handler plune'er is forced outward, causing the removalor the plug from its seat as here.- inbeilore described.

lVith the Sequence switch in position a, r lay 609 operates inacircuitextending from grounded battery cam O in positions El to ll, left-hen d windin of relay 600, conductor 615., cam L in position 4%, conductor 61.0 ilront contact andinncr leit-hand armature ot rc lay 606 to round. Relay 609st, its inner left-hand amnature and front contact connects ground to conductor 619 thence to cam MI in position l, conductor 620, windin oi selector power magnet 121, to battery and ground over the back contact and armature of plus, magnet 125. whereiu ou selection begins. The operation of selector. magnet ]21 causes the gears 118 and 128 to mesh with power gear 112 and gear 129, res )ectivcly whereupon the power belt 131 to which the W1 'cal bridge is attached, is moved trout left to right. The bridge, carrying the plug handler thereupon moves across the multiple bank.

As the selector moves over the multiple. the brush set 167 also carried by the bridge, movcs over the face of the commutator 168. The brush riding on the COlllllllJillliiOl segments 13, causes ground connected to this brush to be sent back by way of the connnutater segments B conductor 522, cum I of sequence switch in position 4;, conductor 616, thence over the tip conductor of trunk 500 to. short circuit the stepping); relay oi the sender in a manner well known in the art. When the sender h as been satisfied the fundamental circuit is opened and relay 606 roleases. Relay 609, however, remains operated since itis locked up first over its front contact and inner right-hand armature. couductor 23, cam N in positions at and 5, couductor 624 to the sleeve segments S of busy trunks, and second from its front contacts and. outer rightdiand armature, conductor 621, K cam in positions 4 and 5, conductor 62?, brush and C con'unutator segments to ground. There is therefore no pause be tween group selection and trunk hunting. The bridge continues to ll'lOVQ across the multiple, therefore, until an idle trunk such as 501 is encountered.

When the idle trunk 501, ch aracterizcd by the absence of ground on its sleeve segmentis encountered, relay 609 loses its sleeve locking; circuit and. then its locking circuit from the l commutator when the plug' ccntered. hen relay 609 restores its armsits inner left-hand armature and back comes to rest. On releasing, relay 609 also connects ground lay-Way of itshuclr contact and inner right-hand miniature, conductor 623, com N in positions d and 5, conductor 624:, brush andcomi'nutator segment S indi- VlClllll to trunk '501 to the sleeve thereof. lhis ground renders the trunk 501 lousy. At con tact reluy 609 connects ground to the conductor (S, conductor 625, cum F: in position 1, winding of sequence switch magnet 120 to battery and ground. lr lngnet 120 in operating "in this circuit causes the sequence switch to move from position t to position 6.

As the sequence switch moves from position tto position 5, the plug magnet 125 is energized in u circuit extending from ground on the E cum in positions 1 to 15, innermost left hand armature and back contact of relay (SO-l, conductor 609, C cum of sequence switch in position 411 too, conductor 519 to buttery :rnd ground through the Winding of plug magnet 125. The actuation oi plug magnet 125 again causes certain mechanical elements to function as hereinhetore described, to cause the plug handler to liorce the plug into the screen multiple. Now the connection hus been completed and the plug, as schematically shown at 523, connects the tip, ring and sleeve conductors of trunktOO to the tip,

turn to i'zoriuul.

ring and sleeve conductors, respt rively, of trunk. 501 by Way oi? the horizontal wire-s 525. In position 6 of the sequence switch, the circuit for plug magnet is opened so that the plug handler plunger 170 is forced stray from the multiple leaving the plug in the multiple, and the return magnet 122 is operated in a circuit extending from grounded buttery, zirmuture and buck con tuct oil. plug magnet 125, Winding o'l return magnet 122, conductor 527, com M in positions 6 end 13, conductor (128, to ground on the cou'uuututor segn'ient M and its associated brush. hlhr net 122 causes certain mechanical functions as hereinheiore described to cuuse the selec As the br l go returns to nor inul, the brush at the some level as commutzu tor s zcgiuent M rides on this segment and consequently magnet 122 remains operated untit the brush leaves the M scgn'lent and rests on the Y segment oi? the cou'unututor.

(ill

, whereupon this relay restores.

At the termii'uition of a cell. the groruul on the sleeve wire 502 of trunk 500 will be ro- 7 .moved in well-known manner, causing the lay 504 to bank terminal 506. Group d is :i so

connected to the disconnect iced 529 from the tor bridge to ro up unother ctmnection.

right-howl armature and back contort of re lay 1, O.ll-2 spring on front oi fruine, and thence to cum H in positions 18 to 1 and positions 7 to 8, conductor (32G, lurch contact and outer lci t-hund sruurture of relay 600, rigit-hund Windi oi disconnect relay (304;, to battery and ground. Relay operates in thiscircuit and locks through its front contact and innermost lettdui armature to ground on the E coin in po minus 1 to 15. A circuit now exists extending from grounded buttery, Winding of sequence switch nuignet 120, D cum in positions 1. to 8, conductor (32?, trout contact and outermost left-hand urnmture of relay 60% to ground.

hilugnet operates in this circuit and the sequence switch is moved into position 9. With the sequence switch in position 9, relay G00 operutes in a circuit extending from grounded battery, right-luunl winding oi 1cluy (506, conductor 505, middle left-heed armature and frontcontuctof relay (304-, conductor 628, cum h: in position 9 to ground. The sequence switch new moves into position 10, nmgnet 120 being operetedin r-Q circuit 0Tbtcnding from grounded buttery, winding of magnet 120, D cum closed in position 9, conductor 610, front contact and inner lett l'urnd ermuture of relay sec to ground. In position 10 relay is pro "ided With n lock-- ing circuit through its own righthund Wind ing, inner rigl'it-hend ermuture and frontcontuct oil? reluy 600, conductru (50?, can! 1'. in position 10, conductor 608, back contact and outer leithzind armature of relay (309. The updrire magnet is new (worsted in u circuit extending from grounded battery, Winding of magnet 124:, closed cents-ch: 013 of trans fer switch 510, conductor 612, J cum closed in position 10, front contact and outer righturnd armature of relay (306 to ground over the outer left-hand urmuture and boot: eontuct of relay (309. lit, at this time, the finder carriage 1t2 is positioned at a point above the noruml position, of plug 101 used in this connection, which only he the nose, should the curriuge have been employed in tt-ing the 'updriw. magnet causes the linder curriuge to .truiel to the top of the iii-lune, whereupon the truns'ter switch operated, (reusing the downdriro magnet 123 to he sul tituted for magnet 12% and contuct (51-4: cl whereupon the finder cru'riugc moves ('lounwurd.

In order to stop, the finder must iind u plug out of its -t sud ground on the tinder bunk contact in the some'po:-=ition. its hero iubeiltn'e described, the coutuct 531. on. the plug handler represented by 531 in 15 will close each time u position is found. Where a plug is out of its seat. When a trunk, such as 500, is found with its uss0- ciuted plug out oi its sent and ground on ates in a circuit extending from ground on the finder bank contact 506, brush 516, concuit extending from grounded battery, wind- 0 back contact and outer left-ha -13, conductor 528, conunutator M, and.

ductor 517, L am in positions and 11, conductor 53 closed contacts 531. of plug handler 532, conductors 534: and 615, lefthand winding of relay 609, cam O, in positions 3 to 11 to battery and ground. Relay 609 in operating opens at its inne left-hand armature and baclccontact the locking circuit .tor relay 606, whereupon this relay release The release of relay G06 effects a cirselector magnet causes the, bridge to move again across the multiplebank carrying the plug; handler insearch of the plugemployed in the set up connection. lVhen the plug handler strikes the plug, contact 531 opencchwhich causes relay (309 to release whereupon the circuit for magnet 121 is opened and the movement of the bridge stopped.

Relay 609 releases causing the sequence switch magnet 120 to operate ma circuit extending from grounded battery, Winding of magnet 120, F cam in positions 11 to 12 4) conductor 625 back contact and inner f... 7 leit-hand armature Oi relay 609. Magnet 120 causes the sequence switch to be moved into position 18, whereupon the plug magnet 125 operates in a circuit extending irom grounded battery, Winding of plug magnet I 125, conductor 519, C cam in positions llto l l, front contact and right-hand, armature of relay 0.0 1 F cam 1n posltions 11 to 12 4 conductor 625, back contact and inner lefthand armature of relay 6.09 to ground. The plug; magnet 125 in operating causes the plug to be seized hereinhe'l ore described.

Vfh'en the sequence switch reaches position 13, the circuit for plug magnet 125 is opened at l? cam in positions 1 and 11 to 12 The pantog raph thereupon restored to normal, permitting the plug plunger 170 to remove the plug fromthe multiple. In restoring. magnet 125 causes the return to operate in. circuit extend;-

ing' from hack contait o magnet 125.. wind 'ofmao conductor 5227, cam M in position I Lb eturn ma...

assoc ated ground ed brush. The

.et. 122' causes the. bridge to be returned.

to its normal. position carrying; the plug; wlthlt. i I

In the. normal pos tion of the brldge,

grounded battery, armature and around on the Y commutator; segment. couductor 534,1 cam in positions 12- to 15. winding of magnet 120 to battery and ground. causes the sequence switch to he movediuto position 10. ll hilc the sequence switch. is moving from positions 1:? to 15, plug magnet 12% is. again energized causing the pantoggraph to be again actuatedto re store the plug toitsnormal seat. The circuit for magnet 125 may he raced from grounded be tel-y, winding of magnet 125; conductor 51.0,(l cam in positions. 11 to 14, front contact and "rut-hand aru'iature of relay cam in positions 13 to 15. conductor 53 1 to ground on the Y commutator.

Inposition 15 01' the sequence switch, rclay 604:,loses. its locking; circuit throiug'h the E cam closed in posi-ious 1 to 1? and releases. lVith relay 00%: unoperated. the sequence switch magnet 190 opt-rah. in a circuit extending'lrom grounded butle. "\Y. winding of magnet 120. canrF in positions (3 to 17. rightrhand armature and. bacl; couturt of'relay 6011-, conouctor but. to ground on the Y commutator. causing the sequence switch tobe moved into position 18 which is the awaiting a lotment position.

t the end of each group oi? trunks, a secmeut D is provided on the commutator. 'lhc aejustment of the counnutator brushes is such that a circuit to the overflow relay 230 is established through a brush in contact with the T) segment to the relay before the sleeve brush loses contact with the sleeve segn'ieut oi the last trunk in the group. The D segments are preferably metal inserts in the commutator which may be strapped together. Should it he desired to increase the size of the trunk group, the strap may be removed.

At the end 01 giiroup selectiom relay 00 releases z.-sl'ie1.'einbefore des -ribcd, whereupon the D segments are grounded from around at the inner left-hand armature and back contact of relay, 6,06, cam N of the sequence switch in posit-ion 5, conductor 31 to the segments D on the comn'iutator. When the contact brush of the ovc 'ilow relay G530 strikes the grounded D segments, the overflow relay (350 is operated in a circuit en 'cudine from grounded batter). Winding of relay 030, normal make-bel' rclfireair contacts of relay (33th couduclor (133, the brush associateiil therewith to grouml on the D segments. Relay (32-30 in operating! locks up by way of its malre-bcfore-lucalc contacts. conductor 63 1, the brush associated therewith to ground on a feed bar OVF on the commutator 108 which is cou'unou to the entire bank. The operation of relay (330 prevents relay 609 from releasing. maintaining it operated in a circuit extending; from grounded battery. 0 cam in positions 3 to 11, left-ban d winding of: relay (05h trout contact and outer armature of relay (309, front. contact and lefthandarmature of relay (330 to ground. 'lclay 609 remaining operated, the plug is carried to the end of the bank to the overflow-trunk. On the overflow trunk position the overflow relay hrush moves off the OVF feed bar, whereupon the locking circuit for relay 630 is opened and this rela releases. The release of relay 630 opens the locking circuit for relay 609 which restores, whereupon the plug handler places the plug in the overflow trunk in the same manner as hereinbefore described in connection with the seizureof an idle outgoing trunk in a desired group. After discharging the plug, the bridge is returned to normal position and the sequence switch moved to position 18 as for a regular selection.

Under normal conditions both plug carriers are in series and are used alternately. The waiting position of the sequence switch is position 18 and the allotted position is position 1. When the sequence switch of either plug carrier reaches position {1, the other sequence switch is moved from the waiting position 18 to the allotted position 1. The circuit ell'ecting this change may be traced from grounded battery, Winding of sequence switch magnet 635 located at the rear of the frame, B cam of the same switch in position 18, conductor 636, B cam of sequence switch on the front of the frame in positions 1- to 17 to ground. Should it occur that both carriers are engaged at the same time and reach position 18 together, the circuit is designed in such a manner that the carrier on the front of the frame will be allotted first. This is accomplished by a circuit extending from ground, Gr cam of sequence switch on the rear of the frame in position 18, conduc tor 637, G cam of sequence switch on the front of the frame closed in position 18, cam A of the sequence switch on the front of the frame in position 16, winding of magnet 120 to battery and ground. The operation of the magnet moves the sequence switch on the front of the frame from the Waiting allotment position 18 to the normal or. allotted position 1. v

A plug carrier on either side of the tram may be taken out of service if it is so desired by actuating key 601 or key 638. If it is desired to remove the carrier on the front of the frame from service key 601 is actuated, placing ground on B cam of the sequence switch on the rear of the frame, so that when this switch reaches position 18, a circuit for magnet 635, is closed causing the switch to move into position 1 immediately. The carrier may be taken out of service at any t me. Any plug that happens to be in the mult1p le at the time a key, such as 601, is actuated, will be taken down asrequired, as the disconnect circuit hereinbefore described is not disturbed by such operation of the key.

What is claimed is:

1. In a telephone exchange system in WlllCll the terminals of a group of incoming lines intersect the terminals of a group of outgoing lines and in which the terminals of incoming and outgoing lines are interconnected by means under the control of a common operating mechanism, the method of establishing connections which consists in causing the operating mechanism to select a connecting means individual to an incoming line, move it to a position for connecting with a desired outgoing line, and cause it to interconnect the incoming line to which it is individual to a desired outgoing line, and returning the operating mechanism to its position of rest.

2. In a telephone exchange system in which the terminals of a group of incoming lines intersect the terminals of a group of outgoing lines and in which the terminals of in coining and outgoing lines are interconnected by means under the control of a common operating mechanism, the method of establishing connections which consists in causing the operating mechanism to select a connecting means individual to an incoming line, move it to a position for connecting with a desired outgoing line, and cause it to interconnect the incoming line to which it is individual to a desired outgoing line, returning the operating mechanism to :its position of rest and causing the operating mechanism to again select the connecting means upon the termination of a call and to return it to its position of rest.

3. In a telephone exchange ystem in which the terminals of a group of incoming lines intersect the terminals of a group of outgoing lines and in which the terminals of incoming and outgoing lines are interconnected by means under the control of a com mon operating mechanism, the method of establishing connections which consists in causing the operating mechanism to travel vertically over a plurality of connecting means associated with the incoming lines, select a certain one of said connecting means, and remove it from its normal position, carry the selected connecting means horizontally to a predetermined position and cause it to interconnect an incoming and outgoing line, returning the operating mechanism to its position of rest and at the termination of a call to cause the operating mechanism to again travel in a vertical plane and locate the normal position of the connecting means heretofore employed, to travel horizontally to the new position of the connecting means and remove it from association with the selected incoming and outgoing line terminals, and return it to its normal position.

4:. In a telephone exchange system in which the terminals of a group of incoming lines intersect the terminals of a group of outgoing lines and in which the terminals of incoming and outgoing lines are interconnected by means under the control of a plurality loperatingmechanisms for serving a connecting means individual to another of said incoming lines.

5. Ina switching mechanism, a multiple bank comprising a plurality of sets of incoming line terminals and a plurality of sets of outgoing line terminals, said sets of outgoing line terminals intersecting said sets oi:-

incoming line terminals, a plurality of means for interconnecting any set of incoming line terminals with any set of outgoing line terminals at the intersections thereof, and means common to said interconnecting means for selecting an interconnecting means, tor moving it to a position to interconnect said sets of .terminals and for returning it to its normal position.

6. Ina switching mechanism, a multiple bank comprising a plurality oi sets of incoming line terminals and a plurality oi? sets of outgoing line terminals, said sets of outgoing line terminals intersecting said sets of incoming line terminals, a plurality of means forinterconnecting any set of incoming line terminals with any set of outgoing line terminals at the intersections thereof, and a plurality of means common to said intercon-- necting means, any one of which is adapted to select an interconnecting means, to move it to a position to interconnect said sets of terminals and return it to its normal position.

7. In a switching mechanism, a multiple bank comprising a plurality of sets of incom ing line terminals and a plurality of sets of outgoing line terminals, said sets of incoming line terminals intersecting said sets oi outgoing line terminals, movable plugs for cross connecting any set of incoming line terminals with any set of outgoing line terminals, said plugs normally resting in plug seaits, a plug handling device, means for causing said device to move said plug to the point of inter section of an incoming line terminal and a desired outgoln'g line'terminal, means to cause said device to insert said plug at said intersection, and means for then restoring said device to its normal position.

8. In a switching mechanism, a multiple bank comprising a plurality of sets of incoming line terminals and a plurality of sets ofoutgoing line terminals, said sets of in coming line terminalsintersecting said sets of outgoing line terminals,movable plugs for cross connecting any set of incoming line terminals with any set of outgoing line terminals, said plugs normally resting in'plug seats, a plug handling device, means for causing said device to move said plug to the point of intersection of an inconnng line ter' minal and a desired outgoing line terminal, means to cause said device to insert said plug at said intersection, means for then restoring said device to its normal position, and means operative following the termiuatimi of a connection for again causing said plug handling device to select said plug and to return it to its seat.

9. In a switching mechanism, a multiple bani: comprising a plurality oi sets of incoming line terminals and a plurality oi? sets of outgoing line terminals, said sets of incoming line terminals intersecting said sets of outgoing line terminals, removable plugs on either side of said bank for cross connecting any set of incoming line terminals with any set of outgoing line terminals, said plugs normally resting in plug seats, a pair of plug handling devices, one on eith r side oi" said bank, means for causing either of said devices to select a plug, more said plug to the point oi intersection of an incoming line terminal and the desired outgoing line tern'iinal and to insert said plug at said intersection, and means for then restoring the operated device to its normal position.

10. In a switchin mechanism, a terminal bani: having sets of incoming and outgoing line terminals therein, a plug normally resting in a plug seat at one end of said bank, and a plug handler adapted to seize said plug and remove it from its seat in response to a call incoming to a set oi incoming line terminals and deposit it in said bank at another position to interconnect said sets of incoming and outgoing line terminals.

11. In a switching mechanism, a terminal. banlr having sets of incoming and outgoing line terminals therein, a plurality of plugs normally resting in plug seats at one end of said bank, and each individual to a set of incoming line terminals, and a plug handler adapted to select the plug individual to a set of incoming line terminals to which a call has been extended, remove it from its seat and carry it to another position on said bank to interconnect said set of incoming line terminals with a set of outgoing line terminode.

12. In a switching mechanism, a terminal bank having sets of incoming and outgoing line terminals therein, a plurality of plugs normally resting in plug seats at one end of said bank, and each individual to a set oi incoming line terminals, and a plug handler adapted to select the plug individual to a set of incoming line terminals to which a call has been extended, remove it from its seat and deposit it at another position in said bank to interconnect said set of incoming line terminals with a set of outgoing line termicarriage to position said plug handler in 01 erative relation with said plug, whereupon said plug-handler seizes said plug, removes it from its normal seat and deposits it at another position in said bank to interconnect a set of incoming and outgoing terminals.

14. In a switching mechanism, a terminal bank having sets of incoming and outgoing line terminals therein, a plurality of plugs normally resting in plug seats at one end of said bank and each individual to a set of incoming line terminals, a carriage, a plug handler carried thereby, and means responsive to a call incoming to aset of incoming line terminals for causing said carriage to hunt for the plug individual to said set of terminals, whereupon said plug handler seizes said plug, removes it from its seat and deposits it at another position in said bank to connect said set of incoming line terminals J with aset of outgoing line terminals.

15. In a switchin mechanism, a terminal bank having sets or incoming and outgoing line terminals therein, a plurality of plugs normally resting in plug seats at one end of said bank and each individual to a set 01 in coming line terminals, a carriage, a plug handler carried thereby, means responsive to a call incoming to a set of incoming line terminals for causing said carriage to hunt I for the plug individual to said set of terminals, means for causing said plug handler to seize said plug and remove it from its seat, and means for causing said plug handler to be disengaged from said carriage and moved to another position in said bank, whereupon said second mentioned means again operates to cause said plug handler to deposit said plug at the new position to interconnect the set of incoming line terminals with a set of outgoing line terminals.

16. In a switching mechanism, a. multiple bank comprising a plurality of sets of incoming line terminals and a plurality of sets of outgoing line terminals, said sets of incoming line terminals intersecting said sets of outgoing line terminals, movable plugs for each of said incoming line terminals for cross connect-ing any set of incoming line terminals with any set of outgoing line terminals, said plugs normally resting in plug seats, a plug handling device, means responsive to a call incoming to a set of incoming line terminals for causing said plug handling device to be moved into engagement with the plug associated with said incoming line terminals, means for causing said device to seize said plug and remove it from its seat, means for moving said device with said plug to the point of intersection of the calling mcoming line terminals and a desired set of outgoing line terminals, means for causing said devices to insert said plug at said intersect-ion, means for then restoring said device to its normal position, and means responsive to the termination of a connection for causing said device to be moved to a position adjacent the vacated plug seat and thence to the new posie tion. of the plug to seize said plug and return it to its sea 17. In a switchin mechanism, a terminal bank having sets oi incoming and outgoing line terminals therein, a plug normally resting in a plug seat at one end of said bank, a plug handler adapted to seize said plug and remove it from its seat in response to a call incoming to a set of incoming line terminals and deposit it at another position in said hank to interconnect a set of incoming and out going line terminals, means for returning said plug handler, and means responsive to the termination of a call for causing said plug handler to hunt for said plug and return it to its normal seat.

18. In a switching mechanism, a terminal bank having sets of incoming and outgoing line terminals therein, a plug normally rest ing in a plug seat at one end of said bank, a plug handler for said plug, means responsive to a call incoming to a set of incoming line terminals for causing said plug handler to seize said plug and remove it from its seat, a bridge adapted to engage said plug handler and move it to another position in said bank, whereupon said plug is deposited in said bank to interconnect at set of incoming and out going line terminals, means for returning said bridge and said plug handler, and means responsive to the termination of the call for causing said bridge to again carry said plug handler into engagement with said plug, whereupon said plug is removed from its position and returned to its normal seat.

19. In a switching mechanism in which plugs are employed as connecting means, a terminal bank, a plurality of plug carriers serving said bank in the establishing of telephone connections, and means for causing said plug carriers to serve said bank in a certain sequence.

20. In a switching mechanism in which plugs are employed as connecting means, a terminal bank, a plurality of plug carriers serving said bank in the establishing of telephone connections, means for causing a certain one of said plug carriers to serve said bank upon the initiation of a call, and means operative when the plug carrier employed reaches a certain position in serving said bank for causing another of said plug llO carriers to be placed inreadiness to serve said bank upon the initiation of another call.

21. In a switching mechanism, a terminal bank, incoming line terminals therein, other line terminals therein, plugs for each of said incoming line terminals positioned on either side of said bank and adapted to in-- terconnect' said incoming line terminals with said other terminals, a plug carrier oneach side of said bank serving said plugs, means responsive to a call on an incoming line terminai forcausing a plug carrier on one side of said banlrto move to and seize a plug corresponding to the calling line, and means operative when the last mentioned carrier reaches a certain stage in extending a connection for preparing the other of said plug carriers to serve a plug corresponding to another incoming-line terminal on which a call maybe initiated.

22. In a switching mechanism in which -plugs are employed as connecting means,

a terminal bank, a plurality of plug car riers serving said bank in the establishing of telephone(connections, means for causing said carriersto serve said bank in a certain sequence, and means for disabling one of said carriers whereby another of said car riers handles all calls incoming. to said bank.

23. In a'switching mechanism in which phigsare employed as connecting means,

riers serving said bank in the establishing of telephone connections, means for causing said carriers to establish connections in turn, and means for disabling one of said carriers whereby another of said carriers handles all calls incoming to said bank and the disabled carrier takes down the conncc tions it was intrumental in establishing.

25 In a switching mechanism in which the terminals of a group of incoming lincs intersect the terminals of a group of outgoing lines and in which connections are made by plugs, a team of plug carriers, and means for causing said team of plug carriers to serve said switching mechanism to interconnect sets of incoming and outgoing line terminals at their points oil" intersection. 26. In a switching mechanism in which the terminals of a group of incoming lines intersect the terminals of a group 01' outgoing lines and in which connections are made by plugs, a team of plug carriers, and means for causing said team of plug carriers to serve said switching mechanism to interconnect sets of incoming and outgoing line terminals at their points oi intersection and to unmake said connections.

27. In a switching mechanism in which the terminals of a group of incoming lines intersect the terminals of a group of outgoing lines and in which connections are made by plugs, a plug carrier on one side of said switdhing mechanism, a plug carrier on another side of said switching mechanism, and means for causing both of said plug carriers to serve said mechanism in turn to interconnect sets of incoming and outgoing line terminals at their points of intersection.

In testimony whereof, I have signed my name to this specification this 13th day of July, 1927-.

'WILLIAM G BLAUVELT

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