US1464726A - Telephone-exchange system - Google Patents

Description

Aug., M, 11923.. L. IPOLINKOWSKY TELEPHONE EXCHANGE SYSTEM k iled April 30, 1920 5 Sheets-Sheet l @w Aug., M, i923. ils-464,72@

L.. POLINKOWSKY TELEPHONE EXCHANGE SYSTEM Filed April 30, 1920 5 Sheets-Sheet 2 Ml Ml Ml c Ooo OOO O Aug., M, R923.

1 POLINKOWSKY TELEPHONE EXCHANGE SYSTEM Filed April 50, 1920 Aug. M, 1923.

L. POLENKOVVSKY TELEPHONE EXCHANGE SYSTEM gli Bild 2mg E3 www ` ed April 30 9 Nj@ Nm@ N [21:1 [IUD :Il:

UU UHUUUDUDU BAELZE Aug. .14, E923.

L. POLJNKOWSKY TELEPHONE EXCHANGE SYSTEM Filed April 30. 1920 5 SheecS-Shee'I 5 MGM.

Patented Ang. la, @23,

sFr-raras earner ortica.

LIEPA PQLENKWSKY, @F ANTWEEP, BELGIUM, ASSIGNOR T@ WESTERN @@MA'W, ENGQRPRATED, 0F NEW Yl'lltl, N. Y., A @@RFRATN @El YZRE.

'TELEPHGNE-EXCHANGE SYSTEM.

Application tiled April all, 1920. Serial 1Go. $577,931'.

To all 'wko/mJ t may concern:

Be it known that ll, LIPA Pomnnowsnr, a citizen ot Russia, residing at Antwerp, Belgium, have invented certain new and use- 5 ful improvements in Telephone-Exchange K Systems, of which the following is a full,

clear, concise, and exact description. f

rlFhis invention relates to telephone eX- change systems and more particularly to l@ systems in which machine switching mechanism is used for establishing connections between subscribers lines.

ln machine switching telephone systems where register senders are employed Jfor 115 lcontrolling the switches in the extension of` connectionsythe registers of these senders are arranged to be positioned, either in response to calling transmitters or operators k keyboards, to record the desired designait@ tions. With the desired designation thus 'recorded the registers then serve to control the selecting operations of av series of switches to extend and complete the connection. lt, during theoautomatic trunk-hunt- 5255 ing movement of any of the switches in the seriespall outlets of the group at that particular stage of the connection are found busy, the switch moves to an overflow position and comes to,V rest. ln certain sys- 3@ tems of the foregoing character it is customary to rovide means whereby the switch, in tin ing all outlets busy, advances to its overflow position and causes the application of a tone-producing current to @it the calling line or the operation ot a super-f y visory signal before an operatorf rll`he partially established connection may then be released in the usual manner.v ln other systems the advance of the switch to overdow t@ position causes theconnection to be released automatically, a busy signal being given at the same time to the subscriber. type of system the lrelease of the unsuccessful connection causes the register sender to t5 be restored to normal; lll .further attempts are made to establish the desired connection,

it is tirst necessary to reset the controlling d .registers o ,tn the sender.

' The obyect of this invention is the prot@ visioniv ot means in a system of the above eneral character, for maintaining the registration ot the desired designation durin the release of the switches, when all outlets are found busy, and for thereupon'reoperatln either,

A feature of the invention relates tol means, operative upon the lapse oi a dehnite interval after any switch has tailed to find an idle outlet, tor releasing the pari tially established connection and tor placing the sender in condition to again control the switches in accordance with .the registered designation in a Jfurther attempt to obtain a complete connection.

Another feature relates to means whereby a switch, which has been operated in accordance with the settingot certain registerseof the controlling sender, may be released and reoperated under the control of such registers during the time that other reg1sters of the sender are bein set to control the operation ot other swltches which cooperate in the establishment out the desired connection.

These and other features contemplated by the present invention will become, more apparent from a consideration of the following descri tion and appended claims.

lln the rawin s Figs. 1, 2, l and 5, taken in order :trom ett to right uwith Fig. 3 placed beneath Fig. 2, illustrate a telephone system embodying the principles of this invention,

. Fig. 1 shows a subscribers line and a reliminary switching unit comprising a ine finder switch and a trunk finder switch tor extending-such line to an idle trunlrcircuit.

Fig. 2 showsa first group selector switch and an auxiliary switchl individual theretoV for associating ari-idle re 1ister-controlli,ng

mechanism w1th the circuits of the groups Fi t shows a second group selector switc and Fig. 5 `shows a final .selector switch havin access to the terminals of called subscri ers llnes. v

- lhe preliminary switching unit shown in Fig. 1 consists ofa line-'dnding switch whose brushes are shown at.110, 111, 112 and 113, and a trunk-finding switch whose brushes gy are shown at 121, 122, 123 and 12a. rll`hese finder switches are of' the simple rotary type, Idrivenlstep by step by a motor magnet over the terminals of an arcuate bank. The brush sets have no normal position but always remain in engagement with the terminals last taken for use.

The group selector switches shown in F igs, 2 and 4 and the final selector switch in Fig. 5 are of the well-known power driven panel type, such as disclosed in the patent to Craft and Reynolds N o. 1,123,696, issued January 5, 1915.

The register-controlling mechanisms, `one of which is illustrated in Fig. 3, which control the selective movement of the switches, are of the revertive impulse-sending type. rllhese controlling mechanisms comprise a plurality of registers A, B, C, D-and E which are positioned under the control of a calling subscribers impulse transmitter and in accordance with the numerical designations of called subscribers lines. A side switch F is provided for the purpose of associating the calling subscribers line with the successive registers. register A has 4been advanced in accordance with the first series of impulses transmitted over the calling subscribers line, the side kswitch F moves forward one position to associate the second register B. The next series of impulses serves to set the register B, whereupon the side switch advances to associate the calling line with the third register C and so on. The registers, having been thus positioned in accordance with the respective digits of the desired designation,

are then el'ective to control the operation of the counting relay set which, in turn, cooperates with the fundamental circuit in the usual manner to determine the extent of op-l eration of the successive selector switches in the extension of the connection. The registers consist of small rotary step-by-step switches, each comprising a plurality of superimposed contact levels with a rotating brush for each level. For clearness of illustration the several contact levels of each register are shown in vertical alignment, one above theyother, together with the brush arm co-operating with each of such contact levels. The register A is provided with four levels of contacts and four corresponding brushes 316, 317, 318 and 319. The register B also has four levels of contacts and four corresponding brushes 320, 321, 322 and 323. rlhe register C' is likewise provided with four levels of contacts with the corresponding brushes 324, 325, 326 and 327. The last two registers, D and E, are provided with only three levels of contacts each. Each of the Several brushes of a register has two contact arms spaced 180O apart and rigidly mounted upon the same rotating shaft. The stationary contacts are arranged 1n a semicircular bank, such that the movable brushes, having completed av half circle of rotation, are in normal position ready for After .fthe first the next operation. Stepping magnets 311, 312, 313, 314 and 315, one for each of the respective registers, serve to drive the movable brushes step by step over the terminals of the stationary banks. The stationary bank terminals of the registers may be wired vto the counting relays shown at the top of Fig. 3 in any manner suitable for exercising the necessary control over the selective operations of the switches. Since the method of wiring the registers to the counting relays is arbitrary and depends upon the type of translation required to satisfy the ygrouping of trunks and lines in the selective switches, it has been considered necessary to show only a few of the connections between the register contact banks and the counting relays. l

The side switch F consists of a rotary step-by-step switch, similar in construction to the controlling registers, provided vwith four levels of stationary contacts. brushes 334, 335, 336 and 337 of the side switch each have two contact wipers spaced 180 apart as shown in the case of the lowermost brush 334. The brushes of thinJ side switch are shown in their normal positions and are arranged to rotate in a direction opposite to the rotation of the register brush arms, as illustrated by the arrows. As a further means for accomplishing the necessary circuit changes during the operation of the controlling 310 is provided for each controlling mechanism.

The sequence switch 310, together with the sequence switches 210, 410, and 510, associated with the selective switches, ma be of the construction shown and describe in the patent to Reynolds and Baldwin No. 1,127 808, issued February 9, 1915.

In the system disclosed, the initiation of a call on a subscribers line causes the automatic operation of an idle ypreliminary switching unit. The line finder operates to find the calling line and the trunk finder operates to extend such line over a trunk circuit to an idle first group selector switch. The auxiliary selecting switch, the brushes of which are shown at 246, 247, 248, 249, 250 and 251, is thereupon started in operation to test and seize an idle register-controlling mechanism. An idle controlling mechanism having been associated with the first group selector switch, the calling subscri'bers line is extended to an impulse relay 300, lwhich responds to series of impulses, to position the successive registers in accordance with the called line designation. After the first two registers, A and B, have been positioned,l

a fundamental circuit is completed and the brush and group-selecting operations takey place at the first-group selector switch. During the operation of the first group-selector switch, the subscriber continues to mechanism a sequence switch The Maarja@ transmit impulses to set the remaining registers C, D and lE. When the lirst group selector has completed its operation, a `fundamental circuit is completed for the operation ot the second group-selector switch, provided at this time all of the reining registers have been positioned. llt the tirst groupselector switch, however, completes its operation prior to the setting of the remaining registers, the operation of the second group selector is delayed until the last ot such registers has been positioned. The second)- ter-controlling mechanism at the corresponding point'in the progress of its operation. Ater the controlling mechanism has stood in its partially operated condition for a predetermined interval of time, means are rendered edective to place said controlling mechanism in its initial condition without.

disturbing the setting of the registers and in fact, without interfering with the regular operation of such registers as may not have been positioned at this time under the control of the calling subscribers transmitter. With the switches thus released and the controllin mechanism returned to its initial set con ition, said switches are again operated in accordance4 with the original setting of their controlling registers to make afurther attempt to establish a through connectionA to the called line. This operation may continue so long as no idle trunks are' found or uitil the calling subscriber abandons the call by hanging upv his receiver.

A detailed description of the operation involved in the extension and completion of a connection will now be given. For this purpose it' will be assumed that the subscriber at substation desires to hold conversation with the subscriber atsubstation 530. Upon the removal of the receiver from. the switchhook at the calling substation, a

circuit is completed fromf battery through '""the winding of line relay 102, contact and outer armature of relay 103, over the yloop of the substation 100, inner armature and contact of relay 103 to groundflielfiyv 102 becomes energized and closes'a circuitfrom battery through resistance 104, contactand left-hand armature of relay 102 to test terkminal 109 of the line finder switch, thus placing a selectable potential on said terminal. Relay 102 also closes a circuit at its right-hand armature tor the energiaation ot relay-105.. Relay completes a circuit from battery through the winding ont coil 1111, winding ot stepping magnet 115, armature and` contact ot said magnet, outer armature and contact et relay 105, back contact and lett-hand armature ot relay 117, Contact and outer lett-hand armature oit relay 118, Contact 129, to ground. A circuit in parallel to the one just traced is also closed through the winding or relay 116, to ground at contact 129. Relay 110, however, being shunted out, does not receive sumcient current to energize. 'l`he stepping magnet 115 interrupts its own circuit and advances brushes 110, 111, 112 and 113 over the terminals of the subscribers lines. llhen the calling line is reached, a circuit is .completed from battery, through resistance 1041, contact and lett-hand armature ot relay 102, terminal 109, brush 113, conductor`130 middle winding oit relay 117 to ground. lltelay 117 energizes and opens the operating circuit ot the stepping magnet 115. Relay is now included in series with magnet 115, .but magnet 115 does vnot receive sucient current to continue its operation. ll-lence the brushes 110, 111, 112 and113 are brought to rest in engagement with terminals 106, 107, 108 and 109 of the calling line. Relay 116 isl made slow to attract lts armaturesv vwhile relay 116 is in its inoperative condition, a circuit is completed trom battery through the inner right-hand armature and back contact or relay 116, lett-hand winding of rela 119, contact and right-hand armature o relay 117, Contact and outer lett-hand armature et 'relay 118, contact 129 to ground. Relay 119, which serves as a test relay attracts its armatures and locks up 4over lts right-hand winding, provided the test brush 124i oi? the trunk finder is standing on the terminal 128 of a busy trunk. This holding circuit maybe traced from battery through the right-hand winding and front contact and right-hand armature ot test relay 119, brush 1241, terminal 128, conductor 252, to ground either at the lower lett-hand sequence switch contact 207 ture ot relay 119, iront contact and innerA lll@ iso

right-hand armature of relay 116 to battery and ground. The stepping magnet 120 interrupts its own circuit and advances brushes 121, 122, 123 and 124 over the terminals of trunk lines in search of an idle one thereof. WVhen an idle trunk is reached, the holding circuit of test relay 119 is opened and this relay deenergizes. Relay 119 opens the operating circuit of stepping magnet 120, thereby bringing the brushes of the trunk finder to rest in contact with the terminals of the trunk line leading to an idle lirst group selector switch. When relay 116 became energized after the lapse of the necessary interval, a circuit was closed from battery through the winding of cutoff relay 103, left-hand winding of register magnet 131, terminal 108, brush 112, conductor 132, outer right-hand armature and contact of relay 116, right-hand winding of relay 117 to ground. The cut-oli' relay 103, by energizing in this circuit, opens the circuit of line relay 102, which, in turn, permits the deenergization of relay 105. Relay 116 remains energized in series with magf net 115 by means of a circuit closed through the inner left-hand armature and contact of relay 116 to ground at contact 129, as above traced.

As soon as relay 119 releases its armatures a circuit is completed from ground through the outer left-hand armature and ContactV of relay 116, back contact and right-hand armature of relay 119, brush 124, terminal 128, conductor 252, outer left-hand armature and back contact of relay 204, lower right-hand contact 203 (1), conductor 253, right-hand winding of relay 202, to battery and ground. Relay 202 becomes energized and closes a circuit from ground through its right-hand armature and front contact, lower contact 205 (l), winding of sequence switch magnet 210 to battery and ground. euence switch 210 energizes in this circuit n moves from position 1 into position 2. s sequence'switch 210 reaches position l a circuit is completed from ground through the lower right-hand contact 207 (lili to 17), conductor 254, terminal 127, brush 123, winding of relay 118, back contact and lefthand armature of relay 119, front contact and inner right-hand armature of relay 116 to battery and ground. Relay 118 energizes in this circuit and opens the above-traced circuit for relay 116. Relay 116 thereupon releases its armatures. The deenergization of relay 116 opens the circuit through the right-hand winding of relay 117, permitting this latter relay to release its armatures.

Relay 118 andA cut-off relay 103, however,

remain energized in a circuit from battery through the winding of relay 103, left-hand winding of register magnet 131, terminal 108, brush 112, inner left-hand armature and contact and winding of relay 118, brush 123, terminal 127, and thence to ground at ycontact 207.

In position 2 of sequence switch 210, the auxiliary selecting switch, the stepping magnet of which is shown at 209, is operated to select an idle register-controlling mechanism. If the test brush 246 'of the auxiliary switch happens to be standing on a terminal individual to a. busy register-controllin mechanism, the relay 202 remains energize in position 2 of sequence switch 210 by means of a circuit from battery through the lefthand windin of relay 202,y upper right-hand contact 206 El to 9), front contact and lefthand armature of relay 202, upper left-hand contact 208 (1 to 2), brush 246, terminal 255, thence to a multiple terminal similar to terminal 255 at some other auxiliary switch, brush 246 at such other auxiliary switch, conductor 255, contact and inner left-hand armature and winding of a relay similar to relay 211, to ground. Relay 202, by remaining energized in this circuit, completes a circuit from battery throu h the winding and armature and contact o the stepping relay 209 here shown, lower right-hand Contact 224 (l to 2), front contact'and right-hand armature of relay 202 to ground. The stepping magnet 209 interrupts its own circuit and advances brushes 246, 247, 248, 249, 250 and 251 to search for an idle register-controlling mechanism. The test brush 246, on reachino a non-grounded terminal 255, opens the holding circuit of relay 202. Relay 202 `releases its armatures and completes a circuit quence switch 210 advances from position 2 into position 3. After relay 202 has released its armatures and before sequence switch 210 leaves position 2, a circuit is closed from ground through the winding of relay 211, lower left-hand contact 214 (1 to 2), lower right-hand contact 214 (ll to 2), back contact and left-handarmature of relay 202, upper left-hand-contact 208 (1 to 2), brush 246, terminal 255, conductor 372, upper lefthand contact 308 (18% to 1%), of sequence switch 310, winding of relay 303, to battery and ground. 4Relays 303 and 211 energize in this circuit. Relay 211 immediately locks up through its inner left-hand armature and contact to conductor 255, independent of the contacts of sequence switch 210.

With the relay 211 energized, the calling subscribers line is extended throughto the windings of the stepping relay 300 at the register-controlling mechanism for the transmission of impulses thereto. The circuit including the windings of relay 300 may be traced from battery through the left-hand winding of said relay,'lefthand winding of tone coil 338, brush 247, conductor 257, outer third register C. lin response tothe rst interruption of the line in the third impulse series, relay 300 becomes deenergized and closes a circuit from ground through its armature and back contact, contact and lefthand armature of relay 301, conductor 374, back contact and left-hand armature of relay 306, winding of relay 302, brush 334, position 3, winding of ste ping magnet 313, to battery and ground. elay 302, stepping magnet 313 and stepping magnet 305 all become energized -in the manner above described. When the impulse relay 300 again energizes at the termination of the first impulse of the series, stepping magnet 313 deenergizes and advances the brushes of the register C one position. lFor each succeeding interruption of the line circuit during the transmission of the third series ot' impulses, magnet 313 operates to advance the brushes oit register C forward one position. At the termination of this series, the stepping magnet 305 becomes deenergized and moves the brushes of the side switch to their fourth position.

'lhe subscriber next manipulates his impulse transmitter to send a series of impulses according to the tens digit ot the wanted number. rlFhe impulse relay 300, on first deenergizing, completes acircuit from ground through its armature and back contact, contact and lett-hand a-rmature of relay 301,

conductor 374, back contact and lett-hand armature of relay 306,'winding ot relay 302, brush 334, position 4, contact winding ot stepping magnet 314 of re ister D, to battery and ground. For eac impulse transmitted in the tens series, the stepping magnet 314 energizes and deenergizes to'cause the progressive advance ofthe brushes of the registerl). At the end "ot the tens series et impulses, the side switch stepping magnet 305 becomes deenergized and advances the brushes ot the side switch to their litthposition.

.lhe calling subscriber finally operates his impulse transmitter in accordance with the units digit to cause the setting ot the ren'- ister E. lln a manner similar to that already described, relay 300, by retracting its armature at each impulse ot the units series, completes a circuit including the brush 334 in its tth position, tor the energization of the stepping magnet 31,5. Magnet 315 causes the advance ot the brushes ot register l. At the termination ot the units series ot impulses, the step ing magnet 305 becomes deenergized and t ie brushes of the side switch move out or their htth position. The stationary terminals of the side switch bank are so arranged that when. one end of each brush moves out ot position 5, the opposite end engages the first terminal on the righthand side of the banlr. The registers ot the controlling mechanism have thus been posi- Meara@ tioned in accordance with the several digits oit the desired designation.

'.lhe controlling mechanism is so arranged that brush and group selection of the first groupv selector switch may commence as soon as the first two registers, A and B, have been positioned by the calling subscribers transmitter. lt will be recalled that at the completion ot the setting of the second register B the sequence switch 310 advanced into position 5. With sequence switch 310 in position 5 a fundamental circuit for controlling brush selection is completed from battery through the left-hand winding of relay 202, lower right-hand contact 213 (3), brush 249, upper left-hand contact 339 (5 to 13),

upper right-hand contact 339 (5 to-6), winding of stepping relay 362, lett-hand armature and contact of the 0 counting relay 376, upper right-hand contact 341 (5), lower lett-hand contact 341 (5 to 7), resistance 377 to ound. Relays 202 and 362 become energized in this circuit. Relay 202 completes a circuit trom ground through its righ hand armature and front contact, lower contact 205 (3) winding of sequence switch magnet 210, to battery and ground. Sequence switch 210 moves out et position 3 and into position 4. Relay 202 remains energized in position 4 ot sequence switch 210 by means of a circuit from battery through its lett-hand winding, upper right-hand contact 206 (l to 9), front contact and lefthand armature of relay 202, upper left-hand Contact 213 (3 to .6), and thence to ground as above traced. With sequence switch 210 in position 4 a circuit is closed for the updrive power magnet 225 to cause the upward movement ol the brush shalt 259 -in its brush-selecting operation. 'lhe circuit oil magnet 225 may be traced from battery through the winding of said magnet, upper right-hand Contact 224 (4), to ground at the front contact and right-hand armatureot relay 202; For each brush-tripping position approached by the shaft 250, the brush 235 engages a metallic segment of the commutator 229. A circuit is thereby closed from battery through the lett-hand winding ot relay 202, upper right-hand contact 206 (l to 9), trent Contact and left-hand armature et relay 202, upper lett-hand contact 222 (3 to 9), lower leftfhand contact 222 to 4), conductor 260, commutator 220, brush 235 to ground. rlhis direct circuit to ground maintains the energization ot relay 202 and at the same time causes the shunting ot the stepping relay 362 in the fundamental c ircuit. `When relay 362 first energizes in series with relay 202, a circuit is closed from ground through the lower left-hand Contact 343 (l to 18), upper right-hand contact 343 (5), arma-ture and contact of stepping relay 362, conductor 378. lower lett-hand contact 344 (5), upper right-hand contact inea-,rae

3414: (5), brush 319 ot register A, standing in its tth position tor example, conductor 353, armature and bach contact ot the number 1I7 counting relay 379, winding ci the number 1, counting relay 380 .to battery and ground. Relay 360 energizes and prepares a circuit from battery through the winding of relay 380, armature and contact ci said relay, winding ot relay 379, bach contact and right-hand armature ot relay 376, lower contact and armature ota relay 361 to ground. Relay 361, it willsbe observed, is energized at this time by means oi a circuit from battery through the winding ol" said relay, upper right-hand contact 332 (5), upper left hand contact 34:2 (5 to 15),righthand armature and contact ot relay 301, lower letthand contact 3011 (3 to 18), to ground. The number 1" counting relay 379 does not energire at this time in series with relay 380 since it is shunted out by the direct circuit to ground, closed at the armature and contact out the steppingv relay 362. As soon as thebrush 235 engages the tirst metallic segment ot the commutator 229 in the upward movement ot the switch shalt 259, stepping relay 362 is deenergized as explained. ltelay 379 is energized and loclrs up in series with relay 380 in the circuit traced. As brush 235 disengages the hrst metallic segment olt the commutator stepping relay 362 again becomes energized. The stepping circuit is now clbsed by way ont register brush 319, conductor 353, armature and iront contact et relay 379, winding ot the number 0 countingrelay 381, to battery and ground. llelay 331 energizes and prepa-res a loclring circuit tor itself in series with the number 0p counting relay 376. As soon as the next metallic segment of the,y commutator is reached by brush 235, stepping relay 362 deenergizes and relays 331 and 376 loclr up in the circuit closed to ground at the armature and contact ot relay 361. The o eration ot relay 376 opens the holding circuit o1? relays 380 and 379, permitting these relays to release. Relay 376, at its lett-hand armature o ens the fundamental `circuit and at its right-hand armature and trent contact, completes a circuit from ground through the armature and lower contact ot relay 361, conductor 332, bach contact and outer armature ot relay 307 winding oli sequence switch magnet 310 to battery and ground. Sequence switch 310 advances trom position 5 into position 6. ln v-oassirig trom position 5 to position '6, the upper right-hand contact 342 is momentarily opened to permit the deenergization of relay 361. ltelay 361, by releasing its armature, opens the loclring circuit of relays 381 and 37 6. lin position 6 oil sequence switch 310, the upper right-hand contact 3l2 is again closed and relay 361 becomes energized. As soon alter the fundamental circuit is opened at the lett-hand armature and contact of relay 376, as brush 235 engages an insulating segment ot the commutator 229, relay 202 deenergizes and completes a circuit :trom ground through its right-hand armature and bach contact, upper contact 205 (l), winding ol sequence switch magnet 210 to battery and ground. Sequence switch 210 thereupon moves trom position l into position 5.

-With sequence switch 210 in position 5 and sequence switch 310 ot the controlling mechanism in position 6, the fundamental circuit is again established for controlling the group selecting movement ci the switch. '1`he only diderence is that the 'fundamental circuit is now closed in position 5 ot sequence switch Contact 213 and in position 6 ot sequence switch'contact 31-1. ltelay 202 becomes energied and completes a circuit from ground through its right-hand armature and front contact, lower contact 205 (5), winding ot sequence switch magnet 210 to battery and ground. Sequence switch 210 is driven trom position 5 into position 6. ln position 6 relay 202 is maintained energized' by` means of the above described circuit including its lett-hand winding and armature and upper lett-hand contact 213 (3 to 6). vWith sequence switch 210 in position 6, the updrive power magnet 225 is energized to cause the advance ot the brush shaft 259 in the group-selecting movement ot the switch. The circuit ot magnet 225 is traceable rom battery vthrough the winding .ot

said magnet, uppery right-hand contact 2241 (6), to ground at the Jiront contact and right-hand armature ot relay 202. ln position 5 ot sequence switch 310, the trip magnet 277 is energized by means of a circuit trom battery through the winding of said magnet, upper right-hand contact 223 (5 to 6), to ground. Magnet 277 operates to trip the selected set ot brushes 2110, 2l1 and 2&1-2, to mathe engagement with the trunk terminals in the banlr. 2411 and 2112 approach each successive group ore terminals in the section to which they have access, brush 234@ engages a metallic segment ot the group-selecting commutator 230. A circuit is thereby closed from batf-- tery through the lett-hand winding of relay 202, upper right-hand contact 206 (1 to 9), liront contact andy left-hand armature of relay 202, lower right-hand contact 203 (5% to 6),conductor 261, commutator 230, brush 2311- to ground. This direct circuit to ground maintains the energication ot? relay 202 and at the same time shunts the stepping relay 362 in the fundamental circuit. Relay 362,

which energizes simultaneously with relay i 202, completes a circuit 'from ground through the upper right-hand contact 30d (6), contact and armature otrelay 362, upper left-hand contact 34d (6), lower right hand contact 3tlg (6), brush 313 ot the reg- As the brushes 230 l 202. 'llhe brus ister A standin in its fifth position, conductor 354, win ing of the 0 counting relay 381 to battery and ground. Rela 381 energizes and prepares a locking clrcuit for itself and the 0 counting relay 376 as described. When brush 234 engages the first me-tallic segment or" commutator 230, relay 362 deenergizes and permits the venergization of relay 376 in series with relay 381. Relay 376 opens the fundamental circuit and also completes a circuit from ground through the armature and lower contact of relay 361. right-hand armature and front contact of relay 376, conductor 382, back contact and outer armature oi" relay 307, winding of sequence switch 310, to battery and ground. Se uenceswitch 310 moves out of position 6 an into position 7. ln leaving position 6, contact 342 opens the circuit of relay 361 which, by deenergizing, causes the release ot the counting relays 381 and 376. As soon as the fundamental circuit is opened by the counting relay 376, as the brush 234 engages an insulated segment ot the commutator 230, relay 202 becomes deenergized and completes a circuit from ground through its right-hand armature and bach contact, upper contact 205 (6), winding ot sequence switch magnet 210, to battery and ground. Sequence switch 210 advances trom position 6 into osition 7.

With sequence switch 210 1n position 7, relay 202 is immediately energized by means et al circuit from battery through the righthand winding ot said relay, upper righthand contact 219 (7 to 74), upper lett-hand contact 219 (7 to 10), conductor 262, brush 251, upper lett-hand contact 341 (7 to 13), lower lett-hand contact 341 (5 to7), resistance '377 to und. Relay 202 completes a circuit trom ground through its right-hand armature an trent contact, lower contact 205 (7), winding oit sequence switch 210, to battery and ground tor moving said sequence switch out of position 7 and into position 3. lt the tirst trunlr in the selected group, upon the terminals ot which brushes 240, 241 and 242 are now standing, is busy at this time, relay 202 remains energized in position 3 oit sequence switch 210 by means oit the tollowin g clrcuit: battery, through the letthand winding ot relay 202, upper right-hand contact 206 (1 to 9), t'ront contact and lett-hand armature ot relay 202, upper lett-hand contact 222 (3 to 9), test brush to the grounded test terminal 24501 the busy trunh. Relay 202, by remainin energized, provides a circuit tor the uprive power magnet 225, traceable trom battery through thevwinding ot said ma et, upper righthand contact 224 (8), to ground at the liront contact and right-hand armature oit relay shatt 259 is again moved u ward in the trunk-hunting operation. pon engagement ot the brushes 240, 241 and 242 withy terminals 243, 244 and 245 of an idle trunk in the group, no ground potential is found 'on test terminal 245 and the abovetraced circuit of relay 202 is opened. Relay 202, however, remains energized by means of a circuit from battery through the righthand windin of said relay, upper right-hand contact 203 58), conductor 263, commutator 231, brush 237 to ground. When the brushes 240, 241 and 242 are accurately centered on the terminals ot the idle trunk, brush 237 engages an insulating segment of commutatorl 231 and relay 202 deenergizes to open the circuit of power magnet 225. Relay 202, by deenergizing, also completes a circuit trom ground through its right-hand armature and ack contact, upper contact 205 (8 to10), winding of sequence switch magnet 210, to battery and ground. Sequence switch 210 energizes in this circuit and leaves position 3.

As soon as sequence switch 210 reaches position 3g a path is closed from ground, through brush 236, commutator 232, conductor 264, lower right-hand contact 222 (32 to 131), test brush 242, to test terminal 245 ot the seized trunk. The application ci this round to the multiples at terminal 245 reners the trunk non-selectable to other group selector switches.

llt may be well to explain at this point that the commutator 232 comprises a, metallic strip having a series of openings or insulating portions 233. rllhe insulating segments 233 are so arranged with respect to the movement ot the switch that the brush 236 is always in engagement with the metallic portion of the commutator 232 while brushes 240, 241 and 242 are in engagement with any set o1 trunli terminals in the group. lt, however, brushes 240, 241 and 242 iind all trunks in a given group busy, they are driven 'over the entire group and come to rest in the over-dow position at whichv time the brush 236 passes otr the metallic portion oit the commutator 232 and engages an insulating segment 233..

As sequence switch 210 passes through position 8;? a circuit is momentarily `closed :trom ground through brush 236, commutator 232, conductor 264, upper right-hand Contact 213 (83), brush 249, upper lett-hand contact 339 (5 to 13),'iower left-hand contact 339 (7 to 13), winding of relay 303 to battery and ground. Relay 303 becomes energized and loclrs up in a circuit from battery through the winding of said relay, lower contacts 339 (7 to 13) to ground at the lett-hand armature and contact ot` relay 303., When sequence switch 210 later arrives in position 9%, relay 202 is energized iaeearae at the left-hand armature and contact of relay 303. Relay 202 attracts its right-hand,

)F is standing in either its third, fourth or fth position. lin either case relay 307 is energized by means of a circuit from ground', brush 337 in its third, fourth or fth position, contact 345 (7 to 8), winding of relay 307, to battery and ground. lf, however, the registers have all been set or as soon as the setting of such registers is completed, relay 307 is deenergized and a circuit is completed from battery through the winding of sequence switch magnet 310, outer armature and back contact of relay 307, lowerleft-hand Contact 347 (8) to ground. Sequence switch 310 thereupon advances into position 9.

l/Vith sequence switch 310 in position 9 and sequence switchI 210 in position 10, a fundamental circuit is completed through to the second group selector shown in Fig. 4 for controlling` the brush-selecting operation.

This^circuit` may be tracedfrom battery through the left-hand winding of relay 403, lower right-hand contact 404 (1), upper left-hand contact 404 (1 to 4), conductor 401, terminal 244, brush 241, upper righthand contact 220 (10 to 13), lower left-hand contact 220 (10), conductor 265, brush 250,

n winding of the stepping relay 362, left-hand armature and contact of relay 376, upper right-hand contact\341 (9), upper' left-hand contact 341. (7 to 13), brush 251, conductor 262, upper left-hand contact 219 (7 to 10), lower right-h-and contact 219 (.10 to 6), brush 240, terminal 243, conductor 400, lower left-hand contact 411 (15 to 8), upper righthand contact 411 (1 to 8), resistance 413, to ground. Relays 403 and 362 become energized in'this circuit. Relay 403 comp-letes a circuit fromoground through its righthand armature and front contact, upper contact 417 (1), winding of sequence switch 410, to battery and ground. Sequence switch 410 advances from position 1 into position 2. In position 2 of sequence switch 410, relay 403 remains energized by means of a circuit from battery through its left-hand winding and front contact and left-hand armature, and upper left-hand contact 404 (1 to 4), and thence to ground as described. Relay 403 also provides a circuit for the up-drive power magnet 418' as follows: batry, through the winding of said magnet, lower contact 417 (2), to ground at the front contact and right-hand armature of relay 403. Power magnet 418 causes the advance of the switch sli-aft 439 in the brush-selecting movement. F or each brush-tripping position approached by the shaft 439, brush 425 engages a metallic segment of commutator 421 and a circuit is closed from battery, through the left-hand winding and front contact and left-hand armature of relay 403, upper lefthand contact 414 (12 to 2'), commutator 421, brush. 425, to ground. This circuit maintains the energization of relay 403 and causes the shunting of the stepping relay .362 in the fundamental circuit.

385, to battery and ground. Relay 385 er1-- ergizes and prepares a locking circuit for itselic and relay 384, relay 361 being energized at this time by the closure oit sequence switch contact 342 in position 9. For each metallic segment encountered by the brush 425, relay 362 is deenergized and a pair of counting relays are energizedand locked up. When the 0 counting relay 376 is finally operated, the fundamental circuit is opened and a circuit is also completed from ground through the armature and lower contact ofxrelay 361, right-hand varmature and front contact of relay 376, conductor 382, back contact and outer armature of relay 307, winding lof sequence switch 310,

to. battery and ground. Sequence switch- 310 moves from position 9 intov position 10. Relay 361 becomes deenergized as sequence switch 310 leaves position 9 and again energized in position 10 of said sequence switch. The momentary release of relay 361 permits the deenergization of the counting relays. As soon after the fundamental circuit is opened at the controlling mechanism, as the brush 425 engages an insulating segment of the commutator 421, relay 403 becomes deenergized and opens the circuit imi of power magnet 418. Relay 403 also completes a circuit from ground, through its rright-hand armature and back contact, up-

per right-hand contact 405 (2), winding of sequence switch. 410, to battery and ground for driving said sequence switch out of position 2 and into position 3, When sequence switch 410 reaches rposition 2, a circuit is closed from battery through the winding of relay 406, upper right-hand contact 407 (2 to 11), lower left-hand contact 407 (2), to ground. Relay 406 becomesy po'sition 3 of sequence switch 410, the fundamental circuit is again closed and relays 403 and 362 become energized. Relay 403 completes a circuit from ground through its right-hand armature and front contact, upper contact 417 (3), `winding of sequence switch magnet 410 to battery and ground for driving sequence switch 410 out of position 3 and into position 4. Relay 403 remains energized in position 4 by means of the circuit closed from battery through its left-hand winding and front contact and left-hand armature and' sequence switch contact 404. Relay 403 provides a circuit for the up-drive power magnet 418 as follows: battery, through the winding of said magnet, lower contact 417 (4), front contact and right-hand armature of relay 403 to ground. The trip magnet 420 is energized at this time by means of a circuit from battery through the winding of said magnet, lower right-hand contact 416 (3 to 4), to ground. The selected setcf brushes 427, 428 and 429 are thereby tripped into engagement with the terminals of the bank. As the brush shaft 439 advances under the control of power magnet 418 in the groupselecting movement, the brush 424 successively engages the metallic segments of the group-selecting commutator 422. By this means a circuit is closed from battery `through the left-hand winding and front contact and left-hand armature of relay 403, upper right-hand contact 414 (311i to 4), commutator 422, brush 424 to ground. This ldirect circuit to ground maintains the energization of relay 403 and also causes the shunting ofthe stepping relay 362 in the fundamental circuit. The stepping relay 362, on energizing in series with relay 403,

completes a circuit from ground, through the upper right-hand contact 304 ,(10), contact vand armature of relay 362, upper lefthandcontact344 (10), conductor383, upper right-hand contact 351 (9 to 10), lower left-hand contact 351 (10 to 8), brush 320 of register B standing in its fifth position,

.upper right-hand contact 352 '(10), brush 325 of register C, standing in position 3 for example, conductor 355, armature and back contact of counting relay 384, winding of relay 385, to battery and ground. Relay 385 energizes and prepares a locking circuit in the manner welll understood. For each group of terminals passed over by the brushes 427, 428 and 429 the stepping relay 362 is operated and a pair of counting relays is energized and locked up. `Wl1en the 0 counting relay 376 is finally operated, the fundamental circuit is severed at the controlling mechanism and a circuit is also completed from ground, through the armature and lower contact of relay 361, righthand armature and front contact of relay 376, conductor 382, back contact and outer armature of relay 307, winding of. sequence switch 310, to battery and ground. Sequence switch 310 advances from position 10 into position 11. ln passing fromposition 10 to position 11, sequence switch con-1 tact 342 momentarily opens the circuit of relay 361 which by deenergizing causes the release of the counting relays. As soon as the brush 424 encounters the next insulating segment of commutator 422 after the opening of the fundamental circuit at the counting relays, relay and opens the circuit of the power magnet 418. Relay 403 also completes a circuit from ground, through its right-hand armature and back contact, upper right-hand contact 405 (4), winding of sequence switch 410 to battery and ground. switch 410 moves from sition 5.

In position 5 of sequence switch 410, relay 403 is energized by means of a circuit from batterythrough the right-hand winding of said relay, lower right-hand contact 409 (5 to 5i), to ground. Relay 403 completes a circuit from ground, through its righthand armature and front contact and sequence switch contact 417 for driving sequence switch 410 out of position 5 into positionl 6. If the firstl trunk inthe selected group, upon'the terminals of which brushes 427, 428 and 429 are now standing, is busy, rela 403 remains energized in position 6 of sequence switch 410 by means of the following circuit: battery, through the lefthand windingand front contact and lefthand armature of relay 403, upper righthand contact 404 (5 to 6%), .test brush 429, test terminal 432 of the busy trunk and thence by way of the test brush 429 at some other selector switch', to ground at a contact corresponding to contact 416, closed in position 6i to 164. Relay 403 provides a circuit from battery through the winding of power magnet 418, lower contact 417 (6), front contact and right-hand armature' of relay 403 to ground. The brush shaft 439 is, therefore, driven upward in the trunk-hunting movement. When brushes 403 becomes deenergized Sequence positionv 4 into pov `lett-hand contact 412 (8),

Y winding-ot the l turning by yway nti-cavas- 431 and 432 of an idle trunk, the circuit of relay 403 is opened since no ground potential isfound on the test terminal 432. Re-

lay 403 is held energized, however, by means of a circuit from battery through the right- `rhand winding of said relay,conductor 440,l

over the test brush 429 to the test terminal 432 of the seized trunkto render such trunk non-selectable to other switches..y ln position 7 of sequence switch 410 a circuit is established from battery, through the letthand winding of relay 403, lower righthand Contact 404 (7), lower right-hand contact 414 (7to 8), brush 427, terminal 430, conductor 500, upper lett-hand contact 503 (K1 to 8) of sequence switch 510, to ground;

elay 403 becomes energized and locks up in a circuit from battery through its lefthand winding and front contact and lefthand armature to ground over the circuit traced. Relay 403 closes a circuit including its right-hand armature and front contact and upper contact 417 (7), for driving se uence switch 410 into position 8.

ith sequence switch 310 in position 11 and sequence switch 410 in position 8 the Jfundamental circuit is extended through to the final selector for controlling brush selection. This circuit may be traced from battery, through the left-hand winding ot relay 505, lower right-hand contact 506 (1 -to 84) lower right-hand contact 507 (1),

lower left-hand contact 504 (l to 6), conductor 501, terminal 431, brush 428, upper thence over the path described, through the stepping relay 362 and reof conductor 400, lower left hand contact 411 (15 to 8), upper right-yy hand contact. 411 I(1 to 8'), resistance 413 to ground. Relays 505 and 362 become energized Relay 505 closes a circuit from ground through its right-handfarmature and front contact,'lowerl left-handcontact 512 (1) winding of sequence switch magnet 510, to battery and ground. Sequence switch 510 moves from position 1 into position 2. ln position 2 of sequence switch 510,'relay 505 is maintained energized by means of a circuit from battery, through the left-hand winding of said relay, lower right-hand contact 506 (1 to 8), front contact and left Y*conductor 401,

hand armature of relay 505, lower left-hand contact 504 (1 to 6), and thence to ground as described. Relay 505 provides a circuit for the high speed up-drive power magnet 514 as follows: battery, through winding ot magnet514, lower right-hand contact 512 (2), front contact and right-hand armature ot relay 505 to ground. The brush shaft 531 of the final selector is driven upward in thc brush-selecting operation. Rach time the brush 521 encounters a metallic segment ot l'the brush-selecting commutator 519, a circuit is closed Jfrom battery, through the letthard winding of relay 505, lower right-hand contact 506 (1 to 8), front Contact and left` hand armature of relay 505, lowenleft-hand contact 504 (1 to 6), lower right-hand contact 504 (1% to 2), commutator 519, brush 521 to ground. This circuit holds the relay 505 energized and also serves to shunt the stepping relay 362 in the fundamental cir-e cuit. Vthen relay 362 first energizes in series with relay 505, a circuit is completed from ground, through the lower lett-hand contact'343 (l to 18), upper right-hand contact 343 (11), armature and Contact of relay 362, .conductor 378, lower left-hand contact 344 (11), conductor 383, lower righthand contact 350 (11), brush 327 of register C standing in its third position, conductor 358, armature and back contact of the number 4 counting relay, winding ol the number 4 counting relay 386, to battery andV ground. Relay 386 energizes and upon the first deenergization of the steppingrelay ,362, locks up in series with the number4 counting relay as above explained. For each brush-tripping position assumed by the switch shaft 531, a pair of counting relays is energized and locked up. lWhen inallv the 0 counting relay 376 becomes energized, thev fundamental circuit is opened and all counting relays preceding the 0 counting relays are released. Relay 376 also completes av circuit fromground through the armature and lower contact of relay 361. right-hand armature and front contact of relay 376, conductor 382, back contact and outer armature of relay 307, winding of sequence switch magnet 310, to battery and ground. Sequence switch 310 advances into position 12. lln passing from position 11 to position 12 the contact 342 opens to permit thel momentary release ot relay 361. rlhe relay '361 permits the release of the 0 and 0 counting relays.

As soon after the fundamental circuit is opened at the 0 counting relay, as the brush 521 engages an insulating segment of the commutator 519, relay 505 becomes deenergized and opens the' operating circuit of the power. magnet 514. Relay 505 also completes a circuit from; ground, through its right-hand armature and back contact, contact 511 (2), winding if sequence switch iov magnet 510, to battery and ground for driving sequence switch 510 out of position 2 and into position 3. In position 3 of sequence switch 510 a circuit is completed from battery through the winding of the trip ma net 517, upper right-handycontact 513 3 to 4), to ground. Magnet 517 operates to trip the selected set of brushes 524, 525 and 526.

With sequence switch 310 in position 12 and sequence switch 510 in position 3, the fundamental circuit is again closed in the manner described, and relays 505 and 362 become energized. Relay 505 locks' up over its left-hand armature and front contact, as eX- plained, and also provides a circuit including its right-hand armature and front contact and contact 512 (3) for driving sequence switch 510 'out of position 3 and into position 4. In position 4 of sequence switch 510, the high speed up-drive power magnet 514 is again energized to cause the advance of the shaft 531 in the reup-selecting movement of the switch. or each metallic segment of the group-selecting commutator 520, encountered by the brush 522, a circuit is closed from battery through the left-hand winding of relay 505, lower right-hand contact 506 (1 to 8%), lower left-hand contact 506 '(32 to 4), 'commutator 520, brush 522, to ground. This circuit maintains the energization aof relay 505 and at the same time causes the shunting` of the stepping relay 362 in the fundamental circuit. Relay 362 on first en-v ergizing in position 12 'of sequence switch 310, completes a circuit from ground through the upper right-hand contact 304 (12), contact and armature of relay 362, upper lefthand contact 344 (12), conductor 383, upper left-hand contact 350 12), brush 329 'of register D, standing in position 3 for example, conductor 354, winding of the 0 counting relay 381, to. battery and ground. Relay 381 is energized and upon` the rst shunting of relay 362, relays 381 and 376 lock up in I vseries with each other. Relay 376 opens the fundamental ,circuit and at the same time, completes the circuit already described for advancing sequence switch 310 out of position 12 and into position 13. In passing from position 12 to position 13 contact 342 opens to permit the momentary deenergization of relay 361 which in turn opens the holding circuit f the 0 and 0 counting relays.` As s'oon fter the fundamental circuit has been opened at the controlling me'chamsm', 'as brush 522 engages an insulating por- 'tlon of commutator 520, relay 505 is deenergized to open the operating circuit of the power magnet 514. kRelay 505 also com'- pletes a circuit including its right-hand armature and back contact and contact 511 (4), for driving sequence switch 510 into position 5. l e

In position 5 of sequence Switch 510 the fundamental circuit is closed for the nal or units selecti'on and relays 505 and 362 become energized. Relay 505 causes the advance of sequenceswitch 510 from position 5, into position 6, as explained. In position 6 of sequence switch 510 a circuit is closed for the low speed 11p-drive p'ower magnet 515 from battery, through the winding of said magnet, upper right-hand Contact 512 (6) to ground at the front contact and right-hand `armature of relay 505. Brushes 524, 525 and 526 are thereby driven at low speedl over the terminals of the selected group of ten lines. lF or each set of terminals engaged, the brush 521 makes contact with the metallic segment of the commutator 519, whereby a circuit is Aclosed from battery through the left-hand winding of relay 505, lower right-hand oontact 506 (1 to 8%), front contact and lefthand armature of relay 505, lower left-hand contact 504 (1 to 6), lower right-hand contact 504 (5% to 6), commutator 519, brush 521, to ground. This circuit maintains the wenergization of relay 505' and causes the shunting of the stepping relay 362 in the fundamental circuit. When the stepping relay 362 first becomes energized in position 13 of sequence switch 310, a circuit is completed from ground through the lower lefthand contact 343 (l to 18), upper righthand contact 343 (13), armature and contact of relay 362, conductor 378, lower left-hand contact 344 (1,3), conductor 383, upper righthand contact 350 (13), brush 332 'of the register E, standing in its third position for f example, conductor 354, winding of the 0 counting relay 381, to battery and ground. Upon the first shunti'ng of they stepping relay 362, relays 381 and 376 lock up in series wlth each other and the fundamental circuit is opened. Relay 376 also completes the above-described -circuit for advancing sequence switch 310 out of position 13. Conwtact 342 opens on, leaving positinn 13 and re lay 361 and the 0 counting relays become deenergized. As soon after the fundamental circuit is opened at the controlling mechax nism, as the brushes 524, 525 and 526 are accurately centered upon the terminals 527, 528

and 529 of the .called line, brush 521 .moves n.

upon an insulated segment of commutator 519 and relay 505 is deenergized. Relay 505 opens the circuit of the up-drive power magnet 515 and completes a circuit including its right-hand armature and back contact and contact 511 6), for driving sequence switch 510;y into position 7. Before continuing with the operations involved in testing the called line and applying ringing current thereto for signaling the called substation, a description will be given of the release of the regwister-controlling mechanism,- and the manner in which sequence switch 210 of the first group selector` advances to prepare the talk- 111g clrcuit at auchV selector in response to the hrushes ot Monroe n release of the register-controlling mechanism.

rlhe units selection having been com-.

pleted, sequence switch 310 is driven out of position 13 as explained. 1n leaving position 13, contact 339 opens the holding circuits of relays 303 and 202. Relay 202 deenergizes and closes a circuit vtroni ground through its right-hand armature and back Contact, upper contact 205 (8 to 10'), winding of sequence switch magnet 210, to battery and ground. Sequence switch 210 leaves position 10 and advances into position 12. Before sequence switch 210 can reach position 12, however, sequence switch 310 at the register-controlling mechanism will have reached position 13%,i to close the following circuit: battery, through resistance 309, lower left-handv contact 308 (lto 18%), inner left-hand armature and contact of relay 36a, lower left-hand contact 371 (135i to 18g) to ground. rllhis direct circuit to ground shunts out the relay 211 which, up to this time, has been maintained energized in the circuit traced over conductor 372. Relay 211 conse'quentlyv deenergizes and closes the following circuit tor relay 215 in series with the callin line: battery, through the left-hand win ing ot relay 215, upper contact 218 (10g to 13), contact 263, conductor 201, thence over the loop ot the calling line and returning hy way ot conductor 200, contact 257, contact 217 (10 to 13), right-hand winding ot relay 215 to ground. lilela 215 energizes and sequence switch 210, on ater reaching position 12, comes to rest.

Relay 211', by retracting its right-hand armatures, opens the circuit of impulse relay 300. 1Relay 300 deenergizes and att/er a short interval the slow-to-release'relay 301 retracts its armatures. When sequence switch 310 reaches position 18, a circuit is completed from hattery through the winding ci relay 300, make-before-hrealr contact ot relay 301, lower left-hand contact 30d, to 18) to ground. Since the hruslies oit the side switch le" are in engagement with the i'irst position contacts on the right-hand side of the bank, a circuit is now completed for the restoration to normal ot the tlrst register A. This battery, through the winding ot stepping magnet 311, brush 3341, standing in its iirst restoring position, winding or relay 302, left-hand armature and front contact ot relay 306, brush 335, iirst restoring position, conductor 387, brush 310, armature and Contact of stepping maet 311 to ground. lelay 302 and magnet 311 ener 'ze in this circuit. Relay 302 closes the a ove-traced circuit tor stepping magnet' 305 oit the side switch. The mepping magnet 311 opens its own circuit, deenergizes and advances the circuit may he traced from the register A. one position. 'lhe advance the brushes another step. During the interruptions of the circuit of magnet 311, relay 302 remains energized to main-- tain the energization of the side switch stepping magnet 305. ,When the register has been completely restored to its normal position the brush 315 moves od the last terminal in the bank and the circuit of magnet 311 and relay 302 is permanently opened. After an interval relay 302 deenergizes and the stepping magnet 305 in turn operates to advance the brushes of the side switch to the second restoring position. ln this position ot the side switch, a circuit is completed from battery throu h the winding ot stepping magnet 312 o register B, brush 334i, second restoring position, winding of relay 302, left-hand armature and front contact ot relay 306, brush 335, second restoring position, conductor 388, upper lett-hand contact 352 (11 to 8), brush 320, position 5, lower left-hand Contact 351 (10 to 8), lower right-hand contact 351 (11 ture and contact ot magnet 312 to ground. Magnet 312 and-relay 302 become energized. Magnet 312 interrupts its own circuit and advances the brushes ot the second register B one position forward. rl`lie circuit for magnet 312 is' now closed from battery through the winding otsaid magnet, brush 334s, second restoring position, winding of relay 302, left-hand armature and front contact ot relay 303, rush 335, second restoring position, conductor 388, hrush 320, position 5, lower lett-hand contact 351 (10 to 8), lower right-hand contact 351 (11 to 18),

to 18), armaarmature and contact ont magnet 321 to ground. 312 again energizcs and interrupts its own circuit to advance the brushes oil the register another position. "ln this manner the second register B is restored to its normal position at which time relay 302 deenergifzes to permit the magnet 305. The side switch is thereby advanced to its third restoring-position. a similar manner the three remaining registers, C, D and ll, are returned to their normal positions at which time the brushes the side switch will have reached their normal positions, as shown in the drawing. l1 circuit is now completed trom battery through the winding voit sequence switch ma et 310, upper lett-hand Contact 3118 (18%? brush 337 and its normally positioned contact to ground. Sequence switch 310 moves into position 1, thus completing the restoration ot the register-controlling mechanism to its normal condition.

Returning now to the `,igioint at which the units selection had been completed at the ldnal switch, a description will he given of the testing and ringing operations. lWhen seo uence switch 510 reaches position 57, a circuit is completed from battery, through the right-hand winding of relay 505, resistance 532, lower contact 509 (7), to ground. Relay 505 becomes energized and closes a circuit including its right-hand armature' and front contact and contact 512 for driving sequence switch 510 into position 8. Assuming the called line 530 to be idle at this time, relay 505 immediately deenergizes as soon as sequence switch 510 leaves position 7. In position 8 of sequence switch 510 a circuit is closed by way of contact 533 (8), for driving said sequence switch into position 9. A circuit is then completed from ground, through the right-hand armature and back contact of relay'505, contact 511 (9 to 17 winding of sequence switch magnet 510 to battery and ground. Sequence switch 510 leaves position 9. @n reaching position 12, contact 509 bottom is closed and relay 505 attracts its armatures. At its right-hand armature and back contact, said relay opens the circuit of sequence switch -magnet 510, causing said sequence switch to stop in position 13. Relay 505 remains energized in position 13 by means of a circuit from battery through the left-hand winding of said relay, lower righthand contact 506 (10:11 to 16), front contact and left-hand armaturey of relay 505, upper left-hand contact 507 (10i to 13%), conductor 502, terminal 432, brush 429, upper right-hand contact 416 (6% to 164), to ground.

As sequence switch 510 leaves position 8, the upper left-hand contact 503 is opened and re ay 403 becomes deenergized. Relay 403 completes a circuit from ground through its right-hand armature and back contact and right-hand contact 405 (8), for driving sequence switch 410 out of position 8, through position 11 and into position 12. Sequenceswitch 410, on leaving position 11, opens the original holding circuit of relay 406 at the upper right-hand contact 407. Relay 406, however, remains energized by means of a circuit from battery through the winding of said relay, armature and contact ot relay 408, lower right-hand contact 407 (11 to 15), front Contact and left-hand armature oit` relay 406, conductor 402, and thence to ground.

lin position 12 of sequence switch 410, rin ing current is supplied to the called sub- Scri ers line. The circuit for the applicatlon of ringing current may be traced from the ringing source 434, contact 433 (12 to 14), winding of relay 408, front contact and inner right-hand armature of relay 406, lower contact 412 (12 to 15), vbrush 428, terminal 431, conductor 501, upper righthand Contact 504 (13 to 17), brush 525, terminal 528, over the loop ofthe called substation 530, terminal 527, brush 524, lower right-hand contact 503 (13 to 17), conductor 500, terminal 430, brush 427 lower righthand contact 411 (12 to 16), upper left-hand contact 411 (12 to 15), to ground. The response of the called subscriber, by removing his receiver from the switchhook, decreases the resistance of the ringing circuit inthe well-known manner to permit the energization of relay 408. Relay 408 opens the circuit of relay 406 which, in turn, completes a circuit from ground through its outer righthand armature and contact, left-hand contact 405 (3 to 17), winding of sequence switch 410, to battery and ground. Sequence switch 410, leaves position 12 and on reaching position 15, closes the following circuit: battery, through the Winding of relay 406, upper right-hand contact 407 (15 to 17), lower left-hand contact 407 (15 to ground. Relay 406 energizes and locks up over its left-hand armature and front contact to the grounded conductor 402. Relay 406 at its outer right-hand armature opens the driving circuit of sequence switch 410, permitting said sequence switch to stop in position 16. 4

Since the called subscriber has answered, a circuit is now closed for the energization ot' relay 216 in series with the called line. rli`his circuit may be traced from battery, through. the left-hand winding of relay 216, upper left-hand Contact 220 (1051Y to 8), up per right-hand contact 220 (10 to 13), brush 241, terminal 244, conductor 401, upper left-hand contact 412 (15 to 16), brush 428, .terminal 431, thence over the loop of the called line circuit as explained in connection with the application ot ringing current, and returning by way of terminal 430, brush 427, lower right-hand Contact 411 (12 to 16), loWer left-hand contact 411 (15 to 8), conductor 400, terminal 243, brush 240, lower right-hand contact 219 (10 to 6), lowerleft-hand Contact 219 (10g4 to 13), right-hand Winding of relay 216, to ground. Relay 216 becomes energized and completes a circuit from ground through its armature and front contact, lett-hand contacts 221 (12), winding of sequence switch magnet 210, ,to battery and ground. Sequence switchI 210 thereupon advances into position 13 which is the talking position. A complete talking connection is now established between the calling and called subscribers lines. Talking current is fed to the calling line through the windings of relay 215 and to the called line through the windings of relay 216.

After the conversation has been completed, the calling subscriber, by replacing his receiver on the switch-hook, causes the deenergization of relay 215. Relay 215 completes aA circuit from ground through. its armature and back contact, upper left-hand Contact 212 (12 to 17 lower right-hand contact 212 (13), conductor 268, winding of sequence switch magnet 210 to battery and iso' incapaci ground. Sequence switch 210 moves from position 13 into position 141. A circuit is thereupon closed trom ground through the right-hand arma-ture and back Contact of relay 202 and upper contact 205 (le), for driving sequence switch- 210 out ot position 111 and into position 15. ln position 15 a circuit is completed from battery,through the left-hand winding of relay 202, lower lefthand contact 206 (15 to 16), upper righthand contact 2124 (15 to 2), upper lett-hand contact 212 (12 to 17), back contact and armature of relay, 215 to ground. Relay 202 energizes and completes a circuit includingr its right-hand varmature and iront contact and contact 205 `for driving sequence switch 210 into position 17. lin position 17, relay 202 becomes deenergized and completes a circuit by way of its right-hand armature and back contact and upper Contact 205 for moving sequence switch. into 18. A circuit is now 'established from battery through the winding of the down-drive power magnet 226, lower right-hand Contact 223 (18), to

ground. rllhe power magnet 226 operates to restore the brush shalt 259 to its normal position, in which position a circuit is completed from battery, through the winding of sequence switch magnet 210, lower contact 228 (5 to 18) segment 238, brush 23d to ground. Sequence switch 210 thereupon moves into its normal position 1. lll/*hen seuence switch contact 207 leaves position 17, t e holding circuit ot' relay 118 and the cutolii1 relay 103 is opened to permit the release oit these relays. The line relay 102 is thereby placed under the control oi'I a subscribers line 100 so that -iurther calls may be initiated. 207 leaves position .18 the busy ground is removed :trom test terminal 128, so the trunk leading to ythe hrst group selector switchmay be then :for use in connection with other callsg llhen sequence switch 210 leavesposition 13g` the lower right-hand contact 222 is opened to brealr the holding circuit of relay 4106 at the second group selector.' Relay 4106 releases its armatiges and completes a circuit including contact 4105 for driving sequence switch 110 out of position 16, through position 17 and into position 18. lln position 18 of sequence switch 4110 a circuit is closed trom battery, through the windings ot' the down-drive power magnet L119, lower letthand Contact 416 (18) to ground. rllhe brush shaft L139 is restored to its normal position under the control ot power magnet 119. rllhe brush shaft havingareached its normal position a circuit is lclosed `from battery through the winding of sequence switch magnet 110, lower contact 4:15 (3 to 18), segment 435, brush 42d, to ground. Sequence switch 6110 thereby moves from position 18 into its normal position 1.

As soon as sequence switch corn'zactv Sequence switch 410 on leaving position 161 opens the upper Contact A16 to permit the deenergization of relay 505 at the final selector switch. Relay 505 completes a circuit from ground, through its right-hand armature and back contact and contact 511 (9 to 17), winding ot sequence switch magnet 510 to battery and ground. Sequence switch 510 moves from position 13, over positions 15 and 17, and into position 18. ln this position a circuit is completed from battery, through the winding of the down-drive power magnet 516, lower right-hand contact 513 (18), to ground. The brush shaft 531 of the hnal selector switch is restored to its normal position under the control ot `the `power magnet 516. lin the normal position ot the inal selector switch a circuit is completed from battery through the winding of sequence switch magnet 510, lower contact 518 (12 to 18), segment 523, brush 522, to ground. Sequence switch 510 advances trom position 18 into its normal position 1. All apparatus is now completely restored to its normal condition.

lt will now be assumed that the called line 530 is busy at the time the units selection is completed at the final switch. lit the end of the units selection, the sequence switch 510 advances from position 6 into position 7 in the manner hereinbetore described. 1n position 7, relay 505 energizes over its right-hand windin. and lower contact 509. oince the called line is lousy at this time a holding circuit is closed for relay 505, traceable from battery, through the lett-hand winding'4 oi said relay, lower right-hand Contact 506 (1 8112), :iront contact and lett-hand armature of relay 505, upper right-hand contact 507 (7 to 99,), test brush 526, test terminal 529, thence by way ot the test brush 526 some 'other iinal selector switch, to .ground at a contact corresponding to contact 513 closed in position to 16:1. Sequence switch 510 afl`= varices through `ositions 7 and 8 inthe manner explained. Upon leaving position the lower contact 506 is opened to sever the circuit traced ifor the lett-hand winding of relay 505. The upper contact 509, however,

closes in position 811 prior to the opening or l contact 506 in position 81, Relay 505. therefore, 4remains energized by means or a circult from battery through the right-hand lwinding of said relay, resistance 532, upper contact 509 (82C to 10), liront Contact and right-hand armature 0in' relay 505 to ground. Sequence switch 510 is therefore arrested position 9. ln this position the brush shaft 531 is restored to its normal position under the control oil the down-drive power magnet 516. A circuit for this magnet may be traced from battery through the winding of said magnet, upper left-hand contact 512 (9'), liront contact and right-hand 4armature oil relay 505 to ground. When the brush

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