US1365269A

US1365269A - Machine-switching telephone-exchange system

Info

Publication number: US1365269A
Authority: US
Priority date: 1918-12-28
Publication date: 1921-01-11
Anticipated expiration: 1938-01-11
Also published as: FR22574E; FR512156A; US1518815A; FR24339E; FR26385E; FR22575E

Description

L. POLINKOWSKY.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 6, m9.

1,365,269. Patented Jan. 11,1921.

5 $HEETS-SHEET 1- //7 venfor:

[49a PO/MAWWS/ry L. POLINKOWSKY.

MACHINE SWHCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 6. 1919.

1,365,269. Patented Jan. 11,1921.

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zmuouu 2 5th 9. 257 2 E I 1 hi4. I

T T f L. POLINKOWSKY.

MACIIINE SWITCHING TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED ran. 6. ms.

1,365,269. Patented Jan. 11, 1921.

5 SHEETS-SHEEI 3.

yen/0r: lfpd o/m/raw ky by A771.

L. POLINKOWSKY.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 6, 1919- I Patented Jan. 11, 1921.

5 SHEETS-SHEET 4.

by A1711 L POLINKOWSKY.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 6, I919.

Patented Jan. 11, 1921. 5 SHEETS-SHEET 5.

7 474 I 47 EB LIPA PDLINKOHSKY, O31 NEVJ Y9 PANY, INCORPORATED, 61 NEE? YORK,

@603 T "WESTERN ELECTRIC COM- .11 CQRPQRATION OF NEW YORK.

h e a a MACI-IINE-SWITCBEING TELEPHGI IE EXCI-EANGE SYSTEM;

Application filed February 6, 1919.

T0 (z ZZ whom it may concern:

Be it known that I, Turn Pomnnowsnr, a citizen of Russia, residing at @63 l i est street, New li orlr, New York, have invented certain new and useful Improvements in Hachine-Switching Telephone-Exchange Sy toms, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephone exchange systems, and more particularly to machine switching telephone s stems of the full automatic type.

A feature of the invention is the provision of means by which, on a register set adapted to be brought in connection with a calling suhscribefs line over a cord, an immediate starting of the release of the register set and of the cord is initiated when the calling line remains open for a time longer than a predetermined length of time, enabling the reg ister to complete its sequence of operation without holding the calling line engaged.

Another feature of the invention and one i in; to the above is the provision of circus at a register set for em ablinr; test to be made at the end of eah impulse series, and during the change-over from one register to'th next, to determine whether the line circuit is open or closed, and to immediately initiate the release of the reg ster set and associated cord, it such line cir is open.

Still another feature of the invention is the nrovisiou of means associated with a reg set for preventing the register set, on premature release or" the call, from advancing into its normal position until the cord associated therewith has reached such a point its sequence or" operations as not to interfere with the register set when the same reaches its normal position.

1 1 fu her feature of the invention is the provision of means associated with the cord, which upon the initiation of a release before completion of the selection, enables the switch. of the cord to complete a sequence ct onerati s and trees the line to which it is connected at the beginning; of the release.

in the drawings:

In Figure 1 i shown a suhscriber s line and first line finder;

F 2 shows a cord circuit comprising a second line finder and a first group selector;

and show a register set;

Specification of Letters Patent.

Patented J an. 11, 1921.

Serial No. 275,4'70.

Fig. 5 shows a final selector;

In Fig. 6 is shown a common arrangement for the timely delay of a monitoring signal; and

Fig. 7 shows diagrammatically the subdivision of cords in pairs.

The selective switches employed in this system may be or" the general type shown and described in the patent to Polinkowslry, No. 1,193,053, issued August 1, 1916.

The system disclosed as embodied in the present invention will be best understood from description of the operation thereof.

31 subscriber, when desirous of obtaining, a connection, removes the receiver from the hook, operating thereby the line relay 201 in the exchange. A circuit is then established over the

individual resistances

202 and 203 or" the subscriber line, the front contact of line relay 201 and both windings of the common starting relays and a potential is created on the c rrespondingr test terminal 210 at the first line finders. Two common starting relays 204: connected in parallel are provided for each line inner group. The relays 2 a, when energized, provide a circuit for the energization of the guarding relay 205 and the power magnets 211 of the tree line finders in the group, the individual circuit of a power magnet 211 being closed over the back contacts of the corresponding test relay 212 and disconnecting relay The power magnet 211, when energized, causes in the well-known manner the rotation of the brush carriage of the line finder along the terminals of the subscribers lines The righthand high-resistance winding of test relay 21 1 of the line fincer, the brushes of which happen to stay on the terminals of the calling line, or are the first to reach these terminals, is energized in a circuit over terminal 210. The left-hand lowrcsistance of relay 214 is brought over its front contact in pinallel to its highresistance winding, reducing the potential at terminal 210 so that no test relay of another line finderwhich passes this terminal is able to operate. When the brushes are centered and contact t brush carriage is opened, the sec- 01 one end test relay 212 is connected in series with the left-hand winding of relay 21d and also becomes energized. The power magnet 211 is disconnected on the back contact 01 this relay, and a circuit is closed over its front contact including the holding magnet 215 of the line finder and the common starting relays 216, and a potential is created over resistance 217 on the corresponding test terminal 230 of the second line finders. The brushes of the first line finder in question are arrested on the terminals of the calling line, whereas the brush carriages of the remaining free first line finders in this group continue to rotate. Relay 205 remains deenergized if a call arrives and there is no first line finder free in the group, in which case the common guarding lamp 206 lights in a circuit over back contact of relay 205 and front contacts of relays 204.

Each second line finder, together with a first group selector, represents a cord which is provided with an individual sequence switch 220 for establishing the different cir cuits in succession, and a searching sequence switch 280 for obtaining a connection with a free register set. For the purpose of reducing the number of simultaneous rotating second free line finders, the cords are divided in pairs, as shown in Fig. 7, and are arranged so that when both cords are free, one sequence switch 220 is in its position 1, and the corresponding sequence switch of the second cord is in its position 18. Only the second line finder on which the sequence switch 220 of the cord is in position 1 is able to obtain a connection with a calling first line finder.

The energization of the common relays 21o causes the closure of a starting circuit for a group of second line finders which have access to the first line finders in question, the individual circuit for each second line finder being closed over contact 223 top of sequence switch 220 and relay 222. The energization of relay 222 closes a local circuit for the energization of power magnet 221 of the line finder brush carriage, over back contact of release relay 231, front contact of relay 222, back contact of relay 232 and sequence switch contact 226 bottom. The brushes of the second line finder rotate, and reaching terminal shown adjacent to brush 230, the test relay 234 is energized in a circuit over contact 282 bottom of sequence switch 280, contact 227 bottom of sequence swit h 220, right-hand back contact of metering-hindering relay 224, right-hand high resistance winding of relay 234, sequence switch contact 228 bottom, brush 230, resistance 217, front contact of relay 212 and back contact of relay 213. The left-hand lo -resistance winding of relay 234 is brought in parallel to its high-resistance winding over its front contact and contact 239 of the line finder brush carriage. Brush 230 is made busy for other line finders. l/Vhen contact 239 is opened the winding of the second t st relay 232 is brought in the same circuit, and relay 232 becomes energized disconnecting 011 its back contact the power magnet 221, whereas sequence switch 220 is energized in a circuit over its contact 229 top, front contacts of

relays

232 and 222 and back contact of relay 231. In parallel to the sequence switch 220 the holding magnet 225 of the line finder is connected over its contact 233 bottom. The brush carriage is arrested on brush 230, whlle sequence switch 220 starts from posi tion 1 and moves under the control of its local contact 265 into position 4.

When sequence switch 220 passes position 2, the high resistance winding of relay 234 is disconnected at sequence switch contact 227 bottom, and the energization of relay 234 is maintained over its low resistance winding. lVhen sequence switch 220 reaches position 3 a circuit is produced for the energization of the cutoff relay 207 of the sub scriber line, relay 213 of the first line finder and connecting relay 235 of the cord, the

circuit including terminals

218 and 238, lefthand back contact of relay 224 and sequence switch contact 236 top. Relay 207 causes the disconnection of the line relay 201, and this in turn the disconnection of the common starting relays 204, so that the circuit for the power magnet 211 of the still rotatingfree first line finders is opened and the brush carriages of these line finders are arrested. At the same time the test relays 214 and 212 on the first line finder in use are de'einergized and cause the deenergization of the holding magnet 215, the relays 216 common to the second line finders and the relays on the remaining second line finders corresponding to relay 222. The power magnets of the remaining second line finders are then disconnected and the brush carriages of these line finders are arrested: Relay 231 and tardation coil 237 are now connected over sequence switch contacts 242'top and 243 top, and both front contacts of relay 235 with the calling subscriber line, whereby relay 231 is energized.

In position 4 of sequence switch 220 the test relays 234 and 232 are disconnected from brush 230 at sequence switch contact 228 bottom. The magnet of sequence switch 280 is now energized in a circuit over contact 224 top of sequence switch 220, back contact of relay 232, contact 227 top of sequence switch 220 and contact 282 bottom. Searching sequence switch 280 start from position 10 and maintains its movement over its local contact 281. Between the positions of sequence switch 280 in which a connection with a register set can be obtained a passing contact 282 top is closed.

Assuming the register set in Figs. 3 and 4 to be free, a connection with this register set is obtained as soon as sequence switch 280 is nearing its position 1. Relay 234 is thereby energized in a circuit over contact t 322 top, the rif "cion lower .tac

quence switch C01 hat-.15. holding Win illlCl 1 DOSl may be erased llOlli-hfallil winding 01' re its quence switch 320 Relay p rent conmct the connectioi Win cl relay 323.

winding togeth i t 284, loner 75 29%. con

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circuit i+ tone coi tion of re alaint clesl he dialing GOD I! Oi V 6 o 0 1 EL AI O I w e. 1 Ydvm .11. 9.... m a u w S S 6 B Q. 0 C n i. W 0 0 1.. I p 6 E 53,... 6 R S O nu L 1 l MN m c .1 9 6t 320 which 1 60 set for "uhe see-t swiich geove'r i1 quence ch an.

HO 2 l b r .l m e Bk 0 C S E 0 .m i 96 ll v. .5 me n 1 1% S i 0 1i 9 C L math or the soon as relay 325 J u, and sis again ives again he oil-suit l.. the register 1% reee t e ciycult ClQSCl'lbG tel 100. en efqq'izerl. current nee 121215.

A? n 2, the disconnected at 5 1 osi relay 823 inbo switch 320 leaves 9 cl tact 3 65 win ding o1 from position 1, causing the energization of relay 329 as soon as contact 101 of register 100 is closed.

Over the back contact of relay 3229 relay 337 is also connected in parallel to register 100, which relay 337, when energized, maintains over its front contact the closure of the circuit for relay 329 independent from the contact of relay 325. The speed with which the register is moving is so selected that a register starts and completes its step in a shorter time than the total time of an opening and a closure on a fast dial. Through varia ions in the speed of the dials, the resistance of the line etc, the stepping relay which follows the impulses in the line may not stay on its front contact a suiiicient time to insure the starting of the register, whereas the quick energizi -9 relay 337 makes it certain that the circuit once closed on the front contact of relay 32 3 is maintained until the register starts and moves from one posi tion into the next. Relay has also a further purpose in that relay 32 once energized, keeps its back contact opened until relay 337 is deenergized. 1f relay 337 is not provided and relay 32:? opens its front contact before the register has reached its next position and has opened its contact 101, relay 329 would also become deenergized and both its windin in series would be brought over its baci: contact in parallel to the winding of register. 100. Relay 2 7 e 29 would make an attempt to again leave its back contact which may then happen to be opened at the moment the front contact of relay 325 is in closed. Relay would then become immediately energized over its left-hand winding, and the impulse will not go to the register, which will tien fall short. @n the other hand, if relay 329 is deenergized and baclr. contact is cl sed at the moment con tact 101 of the reg er is opened, the windings of relays 529 would be brought in paraliel to the winding of register 100, delaying the deenergization of the register, and this would cause an overstepping of the register. lielay 387, which is maintained operated as as long as contact 101 is closed holds over front contact the once energized left-hand winding of relay under current, and hinders this relay from closing its back contact even if the stepping relay has left its front contact. This enables a safe operation of the register which can now be driven with a higher speed, and therefore makes it certain that the register would complete its step quicker than any dial which may lose its adjustment and increase its speed.

lVhen on the last interruption at the dial of the line rircuit, relay remains deenerr' zed for a comparatively longer time, it closes at its back contact a circuit for the energization of a slow-operating relay 334% for a time sufficient to energize this relay.

The left-hand winding of relay 323 is then closed in a circuit over front contact of relay and sequence switch 320 is again energized in the circuit over front contact of relay Sequence switch 320 starts from position 3 and moves into position 6. The relation between the openings of the line circuit at the dial, the time relay 33 1 uses for its operation, and the time sequence switch 320 takes to move into the following position, is such that at all variations in speed and adjustment of the dials or voltage in the ex change, relay does not operate during the short interruptions in the line circuit, but is energized and causes the start of the sequence switch on a long interruption at the dial, whereas the time this relay needs to energize, together with the time the sequence switch 320 takes to move into the following position is under all circumstances longer than the time relay 325 remains deenergized during the long interruption at a dial. In fact re lay is already energized over the subscriber line before sequence switch 320 reaches position ll hen relay 323 is energized, it opens on its back contact the circuit for relay 326, which immediately opens the circuit for the energization of the registers, so that when relay 325 becomes again energized, the register circuit is maintained opened at front contact of relay 326 until sequence switch 820 reaches position 6. lVhen relay 325 opens its back contact, relay 33% is deenergized, and opens the circuit of the left-hand winding of relay l'he right-hand winding of this relay being short-circuited at contact 321, relay 323 is (ls-energized before sequence switch 320 reaches position 6. l/hen sequence switch 320 moves over position 1 an additional enization of register 100 is caused in a circ'it over contact 330 bottom, and register 100 makes an additional step. The purpose of it is to enable the use in the directory of subscriber numbers beginning with the ordinal 1 so as to avoid numbers beginning with the ordinal 0,

ll hen sequence switch 820 leaves position 5, the register 100 is disconnected at contact 328 top, and the hundreds register 110 is connected over sequence switch contact 328 bottom, whereby this contact is closed earlier than contact 327, so that the circuit for the register 110 is ready before relay 326 is energized. The first energization of register 110 takes place immediately the front contact of relay 326 is closed. Register 110 starts from position 0, and in closing its con tact 111, the right-hand winding of relay 329 is short-circuited and relay opens its back contact, whereas the register con pletcs its step under the control of its contact 111 and is arrested in position 1. Relay 337 is now connected in parallel to register 110, and maintains the energization of relay 329 during the time contact 111 is closed. When the dial is released a second time, register 110 is brought to a corresponding position, whereas sequence switch 320 is advanced from position 6 into position 10, in which the tens register 130 is now connected in the stepping circuit over sequence switch Contact top, and is set up according to the third series of impulses from the dial. Sequence switch 320 is then advanced, in the manner already described, from position 10 into position 13, in which the units register 1 10 is connected in the stepping circuit over sequence switch contact 335 bottom. IVhen the dialing has been completed, sequence switch 320 is advanced from position 13 into position 16, in which the sequence switch remains waiting until the se lectors have been set up under the control of the registers.

The capacity of the exchange is assumed to be two thousand subscribers lines. First group selectors and final selectors are therefore provided. The register controls only the selection of odd and even thousands, whereas the hundreds register 110 controls the selection of the corresponding level at the first group selector. The position of the registers determines the translation from the decimal number system of the wanted subscriber line to the system of the switches, whereby register 100 determines the translation for the first group selector. Five levels on the first group selector are reserved for the odd thousand numbers and the other five levels for the even thousand. The setting up of the first group selector takes place during the time the subscriber continues the dialing, and since the trip spindle of the first group selector has to take a position according to the position of the registers 100 and 110, the operation of the trip spindle of the first group selector is delayed until the first two impulse series are completed on the dial. This corresponds to sequence switch 320 leaving position 6. In position 7 of sequence switch 320 a circuit is closed for the energization of sequence switch 350 over its contact 352 top, contact 103 of register 100 and contact 338 top of sequence switch 320. Sequence switch 350 which controls the connection of the registers in succession for the control of the fundamental circuit of the selectors, starts from position 1, and under the control of its local contact 351, moves into position 3. In position 2 of sequence switch 350 the right-hand winding of relay 359 is energized in a circuit over back contact of stepping-out relay and sequence switch contact 354 top. Relay 359 keeps open at its back contact the circuit, hereinafter to be described, for resetting of the registers.

Assuming that the number of the wanted line is 1253, when the dial is wound up and then released, eight short and one 1on opening are made in the line circuit.- The register 100 having made its first step before the first interruption of the line, and not re ceiving any current after the long interruption, has therefore made nine steps under the control of the dial and one step under the control of contact 330 bottom. The reg ister 100 is therefore again in its position 0. Register 110 has been energized eight times, under the control of the dial, and is therefore in position 8. When sequence switch 350 reaches position 3, the fundamental circuit is closed over contact 356 bottom of sequence switch 350, back contact of relay 357, winding of stepping out relay 355, common conductor 296, contact 286, bottom of sequence switch 280, contact 2 17, bottom of sequence switch 220 and winding of relay 222. Both

relays

222 and 355 are energized. Relay 355 disconnects on its back contact the circuit for relay 359 which is now de'einergized. Relay 222 produces the energization of sequence switch 220 in a circuit over back contact of relay 231, front contact of relay 222 and sequence switch contact 229 bottom. Sequence switch 220 starts from position 5 and moves into position 6 in which the trip spindle magnet 248 is energized in a circuit over sequence switch contact 2&9 top front contact of relay 222 and the back contact of relay 231. The trip spindle rotates and produces at its contact 250 top over sequence switch contact 223 bottom short-circuitings around the winding of relay 355. As soon as 100 the back contact of relay 355 is closed, the register 110 is energized in a circuit over contact 112 of register 110, contact 361 bottom of sequence switch 350, back contact and left-hand winding of relay 359, back con- 105 tact of relay 355 and sequence switch contact 35 1. Simultaneously with the energization of register 110, relay 362 is also energized and provides over its front contact a bridge to the contact of relay 355. Relay 362 in the circuit for the outgoing impulses has the same purpose as relay 337 in the circuit of the incoming impulses, and enables a safe operation of the registers. As soon as contact 111 is closed, the left-hand 115 winding of relay 359 is short-circuited, and the right-hand differential winding of this relay causes the opening of its back contact. Register 110 starts from position 8 and moves into position 9. and as soon as its contact 111 is opened, relay 362 is de'elnergized. In the meantime, trip spindle contact 250 has been opened. The stepping relay 355 leaves its back contact; relay 359 is deenergized. On the following closure of contact 250, relay 355 is again de'e'nergized, and register 110 energized, starts from position 9 and moves into position 0. On the following closure of contact 250, relay 357 is energized in a circuit over sequence switch contact 363 bottom, contact 104: of register 100, contact 11d of register 110, contact 361 bottom of sequence switch 350, back contact and lefthand winding of relay 359 and back contact of relay 355. Relay 357 opens the fundamental circuit. In parallel to the right-hand winding of relay 357 is also connected the sequence switch 350, which is energized, starts from position 3 and moves into position 4.

When contact 351 is closed and the lefthand winding of relay 359 is short-circuited, this relay is energized and maintains its energization over back contact of relay 355. After contact 250 of the trip spindle is also opened, relay 222 is deenergized, and sequence switch 220 is energized in circuit over its contact 251 bottom, back contact of relay 222 and the back contact of relay 231. Sequence switch 220 starts from position 6 and moves into position. 7, in which the test relay 23 i is connected at sequence switch contact 228 top with the test brush 252 of the first group selector. Relay 222 is now energized in a circuit over resistance 253, contact 246 top of sequence switch 220, contact 283 bottom of sequence switch 230, wire 293, the back contact of relay 339 and contact 240 top of sequence switch 320. Sequence switch 220 therefore stops in position 7. The power magnet 2&1 of the group selector brush carriage is thereby energized in a circuit over contact 254: bottom of sequence switch 220, back contact of relay and front contact of relay 222. The brush carriage rotates in the wellknown manner with the brushes along the terminal row determined by the position of the trip spindle. In reaching the test terminal of a free final selector, relay 23 i is energized in a circuit from ground, over contact 232 bottom of se quence switch 280, contact 227 bottom of se quence switch 220, right-hand back contact of relay 22st, right-hand winding of relay 23st, contact 228 top of sequence switch 220, test brush 252, contact 44-1 of sequence switch 4:50 individual to the final selector and resistance 4A2. In parallel to resistance 4A2 is also connected a high-resistance release relay &3. Relay brings its lowresistance winding in parallel to its highresistance winding, and makes the terminal of th final selector busy. As soon as contact 269 of the brush carriage is opened, and the shunt around relay 232 is removed, this relay is also energized, the power magnet 241 is disconnected at the back contact of relay 232, while a circuit is provided for the energization of sequence switch 220 over contact 229 top and front contacts of

relays

232 and 222. In parallel to the sequence switch is also connected, over its contact 233 top, the holding magnet 245 of the group selector, the brush carriage is arrested and sequence switch 220 starts from position 7 and moves over posit-ion 8 into position 9, in which the fundamental circuit is prepared at sequence switch contacts 247 top and 255 bottom to the final selector, pending the closure of the fundamental circuit at the register set.

Sequence switch 350 remains in position 4 until the tens and units registers have been set up under the control of the dial, and sequence switch 320 has moved into position 16, in which sequence switch 350 is energized in a circuit over contact top and contact zs ii bottom of sequence switch 320. Sequence switch 350 starts from position a and moves into position 5, in which the fundamental circuit is closed at the register set over back contact of relay 357, and sequence switch contact 356 top and conductor 207, and at th final selector over the contacts let-it bottom and top of sequence switch 450. Relay 4-52 the final selector and relay 355 at the register set are energized: relay 35!) is deenergized. A circuit is closed for the energization of sequence switch 150 over its contact- 4&6 bottom and front contact of rclay 452. Sequence switch 4,50 starts from position 1 and moves under the control of its local contact 451 into position 2, in which the trip spindle magnet 448 is energized in a circuit over sequence switch contact 47 7 bottom and front contact of relay 452. The trip spindle rotates and provides at its contact 455 top over sequence switch contact 4:49 bottom short-circuitings around relay 355 in the fundamental circuit.

ll hen relay 355 is deenerglzed, register 130 is energized in a circuit over its contact 132, contact 367 top of sequence switch and back contact of relay 359. Register 130 starts from position 5 and moves into position 6. After register 130 is restored to position 0 under the control of relay 355, a circuit is established on the following (lechergization of a relay 355 over contact 13 1 of register 130, and contact 352 top of sequence switch 350 for the energization of the sequence switch 350 and the relay 357. The fundamental circuit is thereby opened, whereas sequence switch 350 starts from position 5 and moves into its position 7. After contact 351 is opened, relay 357 is deenergized, and the fundamental circuit is again closed at its back contact. lVhen contact 4l55 of the trip spindle is opened, relay is deenergized, and sequence switch 450 is energized in a circuit over its contact top and back contact of relay Sequence switch 450 starts from position 2 and moves into position 5. The duration of the open ing of the fundamental circuit at back contact of relay 357 is so adjusted that contact dl7 of sequence switch 450 is opened, before relay e52 can be energized a second time over the fundamental circuit, whereas the energization of this relay takes place before sequence switch 450 reaches position 5. The power magnet 461 of the brush carriage is now energized in a circuit over sequence switch contact 456 top and front contact of relay L52. lhe brush carriage rotates along the sixth terminal row; a series ot shortcircuitings of the stepping relay 355 in the fundamental circuit is again produced at contact 457 top of the brush carriage over sequence switch contact 4A9.

"When the relay 355 is deenergized, a circuit is established for the energization of register 140 over contacts of

relays

355 and 359, contacts 367 bottom of sequence switch 350 and contact 142 of units register 140. After register 140 reaches position 0, under the control of relay 355, a circuit is established for the energization of sequence switch 350 and relay 357 at the following deenergization of relay 355, over contact 143 oi register 14-0, back contact of relay 3%, contact 1 A of register 140 and contact 352 top of sequence switch 350. The fundamental circuit is again opened and sequence switch 350 starts from position 7 and moves into position 18. lVhensequence switch 350 leaves position 9, the circuit in which relay 222 has been maintained energized during the progress of the selection is now opened at contact 368 top of sequence switch 350, causing the deenergization of relay 222 in the cord, whereby sequence switch 220 is energized in the circuit over its contact 251 bottom and back contact of relay 222. Sequence switch 220 starts from position 9. ln position 10 of the sequence switch the fundamental circuit of the register set is disconnected at contacts 255 and 247 of sequence switch 220. Supervisory relay 262 and retardation coil 257 are connected over sequence switch contact 255 top and 256 top to the selector. When sequence switch 220 leaves position 9, stepping relay 325 is disconnected from the subscribers line at sequence switch contacts 2&2 and 2&3, and the subscribers line is again connected over these sequence switch contacts with relay 231 and retardation coil 237. in position 10 sequence switch 220 is energized in a. circuit over its contact 258 bottom, and back contact oi relay 262. Sequence switch 220 moves therefore over position 10 into position 11.

As soon as relay 325 at the register set is deenergized, sequence switch 320 is energized in a circuit over its contact 348 bottom. Sequence switch 320 starts from position 16 and moves into position 17. \Vhen sequence switch 350 reaches position 18, a circuit is established for its energization over contact 372 bottom of sequence switch 350, back contact of relay 326 and contact 3'32 bottom of sequence switch 350. The sequence switch 350 starts from position 18, and moves into position 1, in which the lefthand winding of relay 323 is energized in a circuit over contact 35% bottom of sequence switch 350 and contact 322 bottom of sequence switch 320. Sequence switch 320 is new ener ized over front contact of relay 3 3, starts from position 17 and moves into position i. The register set is and can be taken for a new call.

After the fundamental circuit has been opened at the r gister set, the relay 41 32 is tie-energised as soon as contact e57 top is opened, the power st 461 oi the final selector is disconnected, whereas sequence switch 450 is energized in a circuit over contact top and back contact oi relay In parallel to the sequence switch, the holding magnet 435 is conn cted over its contact 1:58 bottom. The br sh is arrested, and sequence switch starts from position 5 and moves into position 6. tln subscriber line groups on which the final selector is arranged to search for a tree line to private branch exchanges, the cuto'lt relays 488 on the single subscriber line and on a last line to private one range are pro vided with shunts 4139. T he final selector is provided with a special test relay 463 which can energize over the cutoii relay oil? a free private branch exchange line. ltelay M33 is also energized over the test terminal of a single subscriber line, or of the last pr vate 9 branch exchange line, disregarding whether the line is free or busy; assuming the line tree, test relay #163 is energized in a circuit over sequence switch contact -l59 bottom, test terminal of the subscriber line H0 and cuter? relay ass, respective resis ance 489. A, circuit is thereby establis-ahed for the energization relay 1-62 over front contacts of relays 4163 and i413, whereby sequence switch 450 energized in a circuit over back contact of relay 452, front contact of relay M32 and sequence switch contact i533 bottom. Sequence switch efO moves over position 6 into position 10.

When the sequence switch 0* lcctor reaches position 8, the wan undergoes a final test and the rig high-resistance winding of the relay iG l which can only enei k e on a tree line, even it the cutoff relay is i rovided with a shunt, is connected in a. circuit over the cutoff rolay 4-38 v at t rminal i 70 and sequence switch contact 9 top. it the line :t 3e, relay 461 brin over its front contact in parallel. to its hign resistance winding its lefthand low-resistance winding, together with the winding of relay 462. The terminal. oi t 11G wanteilline is made busy whereas relay .4162 is energized. Sequence switch 4e50, in reaching position 10. is energized in the circuit over front contact of relay 41-62, and the sequence switch mores orer positions 10 and 11, into position 12, in wh m an alterna t ringing current is immediately sent to the station of the wanted line in a circuit over 100 the sequence switch contacts 466 top and 167 bottom, including the ringing relay 4:60. ltelay 452 is brought over sequence switch contact 4268 bottom in connection with common interrupter 4:69, which when closed, causes the energization of relay 152, whereby the sequence switch 150 is energized in the cirruit orer the front contact of this relay, the sequence switch 130 mores into position 13, in which relay 452 is connectet over sequence switch contact 1-71 with a it'urther common interrupter 472. The two interrupters 4269 and 1-72 are continuously operated, and are arranged to close the circuit to ground at predetermined time intervals so that atter the sequence switch 47:0 reaches position 12, it is brought aft r the lapse of a few seconds over

positions

12 and 13, into position 1 1. The duration of time in which sequence switch 150 re ains in

positions

12 and 13 and an instantaneous rin ing current is sent to the wanted station depends upon the moment the sequence switch reaches position 12, and varies slightly according to whether at this moment the in terrupter 169 has just opened its contact or is near to close it. The contact of these interrupters is closed for a time sutlicient to energize relay 452, and to cause the energization of sequence switch 150, but not sui'iicient to maintain its energization more than to move the sequence switch from one position. In. this manner the sequence switch 4-50 is held in position 18 for at least a time which elapses between the closure of the interrupter 4:69 and the following closure of interrupter 472.

lVhen sequence switch 150 reaches position 1 1, the direct connection of the ringing current is removed in opening sequence switch contact s66, and the connection of the subscriber line with the ringing source of current is now maintained over seq ence switch contact 173 bottom and the common interrupter 4-7 1, which in selected time inter vals connects in succession the circuit either to the source of ringing current or to ground. During the time sequence switch 1-50 is in positions 12 to let, the primary winding of tone coil 4-77 is connected over sequence switch contact e76 bottom to a common interrupter, whereas the secondary windings of coil 177 are connected in bridge to the line over sequence switch contacts 1 1% top and 145 bottom. The call subscriber perceives thereby an indication that the ringing of the called party is proceeding. As soon as the receiver at the wanted station is lifted from the hook the ringing relay 4:60 is energized and causes over its front contact and sequence switch contac' 1 1-6 top the energization of sequence switch 450 which starts from position 1 and moves into position 15 in which the ringing current supply is disconnected, and athrough con nection or the subscriber line is made over sequence switch contacts 173 top and 46? top to the transmitter current supply bridge at the group selector. Relay 262 is thereby energized. Sequence switch 220 is energized circuit over th contact 229 top and at contact of relay 262. Sequence switch starts from position 11 and moves into It the number or" the wanted re 2, sample 2253, i usands register 100 receives eight imfrom the dial and one impulse over bottom of sequence switch 320. The regis er 100 is therefore in position 9. il hen the fundamental circuit is closed over relay 222 of the first group selector, the resetting of the hundreds register 110 begins 1n the manner as has been described, and when i ister 110 reaches position 0 the folr c cnergization of relay 355 provides for the energization of register 100 over contact 11 1- or register llO and contact 102 of register 100. This causes register 100 to move from position 9 into position 0, so that sequence switch 350 and the relay 35*. are energized on the next deenergization of relay 355 The trip spindle ot' the first 'roup selector has therefore made an addiional step, and is arrested in its fourth intead of its third position, as has been preiously described. The brush carriage of the f rst group selector searches now in an even level of a free final selector.

it. the second figure ofthe wanted number odd, for example, number 1353, register 110 receives from the dial seven impulses and is a ested in its position 7. hen sequence switch 350 moves over its position 1, relays 3'73 and 37 1 are energised in a circuit over contact of sequenc switch 350, and contact 116 of register 110, whereby relay 373 provides a locking circuit over its front contact and sequence switch contact 372 top. After the units register 14-0 has been set up, the energization of relays 378 and 37 1- is maintained over contact 146 of register 140 and contact 35-1 of sequence switch 350. When sequence switch 850 passes over position 2, register 110 is energized in a circuit over contact 112, contact 861 top of sequence switch 350 and contact 116 of register 110. Register 110 makes an additional step and takes the same position as it the next lower even figure has been dialed. The trip spindle of the group selector takes therefore the same position, disregarding whether the second figure of the wanted number was even or odd, whereas relay 374': controls the translation of the units on the final selector, causing the advance or" the brush carriage to the second half of the terminal row. hen the brush carriage of the final selector is rotating and relay 355 controls the units register 140, the circuit or" this register is maintained in position 0 over front contact of relay 374 and contact 143 of register 140. Register 140 passes therefore over 0 position and starts a second rotation. When moving between position 0 and position 1, the holdin circuit of

relay

373 and 374 is now opene at contact 146 of register 140 and

relays

373 and 374 are denergized. Then the units register 140 completes its second rotation and reaches position 0, the circuit is eX- tended over contact 143, back contact of relay 374 and contact 144 of register 140 to the sequence switch 350. The brush carriage of the final selector is therefore arrested at the second half of its terminal arc in a position corresponding to the position of the units register.

Then, after a successful conversation, the calling subscriber restores his receiver on the hook relay 231 is. deenergized, and sequence switch 220 is energized in a circuit over sequence switch contact 251 bottom, and back contacts of relays 222 and 231. Sequence switch 220 starts from position 12 and moves over position 13 into position 17. When the sequence switch 220 moves over position 14 to 16, the metering battery 259 is connected over sequence switch contact 236 bottom and left-hand back contact of relay 224 to terminal 238, whereby the meter 208 of the calling subscriber line is operated. In position 17 of sequence switch 220 the power magnet 241 of the brush carriage of the first group selector is again connected in the circuit over sequence switch contact 254 bottom, back contact of relay 232, contact 227 top of sequence switch 220 and contact 282 bottom of sequence switch 280.

The brush carriage rotates until its home connected at the sequence switch contacts- 228, 256 and 255, relay 443 at the final selector is de'e'nergized and sequence switch 450 is energized in a circuit over contact 458 top and back contact of relay 443. Sequence switch 450 starts from position 15 and moves into position 17. Disregarding the deenergization of relay 443, the circuit containing

test relays

462 and 464 is maintained closed over sequence switch contact 478 top and the called line is maintained busy. In position 17 of sequence switch 450 relay 452 is brought over sequence switch and back contact of relay 452.

gized over the subscriber line in a circuit including

sequence switch contacts

467 and 445. Sequence switch 450 is held in position 17 and lamp 481 is connected in a circuit over sequence switch contact 446 top and front contact of relay 452, displaying a guarding signal. When the called subscriber has also restored his receiver, relay 452 is deenergized and sequence switch 450 is energized in the circuit over contact 453 Sequence switch 450 starts from position 17 and moves into position 18 in which the power magnet 461 of the brush carriage is energized in a circuit over sequence switch contact 456 bottom, back contacts of

relays

462 and 452. The brush carriage rotates until its home contact 457 bottom is closed, whereby relay 452 is energized in a circuit over contact 457 bottom and sequence switch contact 468 top. The power magnet 461 is disconnected whereas sequence switch 450 is energized in the circuit over its contact 446 and front contact of relay 452. In parallel to sequence switch 450 is the holding magnet connected over its contact 458; the brush carriage is arrested, whereas sequence switch 450 starts from position 18 and moves into position 1.

After the release of a connection, sequence switch 220 of the cord remains in position 18 until the second cord of the pair of cords. is engaged in a call. This arrangement is best shown in Fig. 7 in which relay 272 corresponds to relay 262 in the cord of Fig. 2; sequence switch 270 corresponds to sequence switch 280 of Fig. 2, and

contacts

274 and 276 correspond to sequence switch contacts 244 and 256 of sequence switch 220, while

contacts

278 and 279 correspond to sequence switch contacts 288 and 289 of sequence switch 280, and wires 271 and 275 correspond to

wires

291 and 292. Assuming the second cord to be engaged in a call, sequence switch 220 provides in position 18 a circuit for the energization of sequence switch 280 over contact 244 bottom of sequence switch 220, wire 291, and a contact on the second cord corresponding to sequence switch contact 289. Sequence switch 280 rotates and moves into position 10. In passing position 93;, a circuit is closed for the energization of relay 262 over contact 256 bottom of sequence switch 220 and contact 288 top of sequence switch 280. Sequence switch 220 is thereby energized over front contact of relay 262 and sequence switch contact 229. Sequence switch 220 starts from position 18 and moves into position 1 whereby contact 224 is opened before sequence switch 280 reaches position 10.

If the called subscriber is the first to restore his receiver on the hook, relay 262 in the cord is de'energized and sequence switch 220 is energized in a circuit over back contact of relay 262 and sequence switch contact 258 top. Sequence switch 220 starts from position 12 and moves into position 13. The circuit over the brushes of the first group selector is thereby disconnected at sequence switch contacts. 228, 256 and 255. The final selector is released, while the sequence switch of the cord remains in position 13 and the calling line is held busy until the calling subscriber restores his receiver and relay 231 is deenergized. Sequence switch 220 is then energized over back contacts of relays 231 and 222.

If the wanted line has been found busy and the test relays 464 and 462 have not been energized, when sequence switch 450 of the final selector moves over position 8, the sequence switch 450 is arrested in position 10, in which the primary winding of the busy tone coil 477 is connected over sequence switch contact 476 to a busy tone interrupter. The secondary winding of the busy tone coil 477 is thereby brought in bridge to the line, and the calling subscriber receives a busy tone. When the subscriber restores his receiver and relay 231 is deenergized, a circuit is established for the energization of the left-hand winding of metering hindering relay 224 including back contacts of relays 231, and 222, contact 251 top of sequence switch 220 in position 11. Relay 224 disconnects at its left-hand back contact the circuit for

relays

235, 213 and 207, while over a holding circuit is provided the lefthand front contact of relay 224 for its left hand winding. Over the right-hand front contact of relay 224 and its right-hand lowresistance winding, a circuit is established for the energization of sequence switch 220, including contact 227 bottom of sequence switch 220 and contact 282 bottom of sequence switch 280. Sequence switch 220 starts from position 11 and moves over

positions

12 and 13 into position 17. The purpose of resistance 266 in the circuit of the local contact 265 of sequence switch 220 is to hinder the deenergization of the righthand winding of relay 224. After the disconnection of the group selector, relay 443 is deenergized, and sequence switch 450 is energized over back contact of relay 443, starts from position 10 and moves into position 11, in which the power magnet 461 is energized in a circuit over sequence switch contact 456 and back contacts of

relays

462 and 452. The brushes are restored to their position of rest, whereby after contact 457 is closed, relay 452 is energized, causing the energization of sequence switch 450.0ver front contact of relay 452. Sequence switch 450 starts from position 11 and is maintained energized in positions 12 to 15 over back contact of relay 443, while in position 17 sequence switch 450 is energized over back contact of relay 452 and moves into position 18, where relay 452 is again energized over contact 457, so that sequence switch 450 is energized over front contact of relay 452 and moves into position 1.

Since sequence switch 220 is held in position 11, whether the wanted line is busy or a ringing current is sent to the wanted station, relay 224 is energized if the calling subscriber gives up the' connection before the called subscriber has answered. The release proceeds therefore without metering if the sequence switch of the final selector is in its ringing position and the called subscriber does not answer.

If the called number belongs to a private branch exchange, relay 463 tests in position 6 of sequence switch 450 the terminal to which the brushes of the final selector have been brought under the control of the register set. Assuming the first private branch exchange line busy, relay 463 remains deenergized. Power magnet 461 is energized in a circuit over sequence switch contact 456 bottom and back contact of relay 462. The brush carriage rotates and a free line is searched for in reaching which relay 463 is energized. During the time the brushes move from one terminal to another, relay 462 is short-circuited over sequence switch contact 449 top of sequence switch and contact 457 top of the brush carriage. As soon as the brushes are centered at the terminals of a free line and contact 457 is opened, relay 462 is energized, and sequence switch .450 is advanced from position 6. If all lines to the private branch exchange are busy, relay 463 is energized on the terminal of the last line, and through resistance 489. ()n the repeated test in position 8 of se quence switch 450, relay 464 remains deenergized. Sequence switch 450 is arrested in position 10 and a busy tone is given to the called station. Through the repeated test on a final selector for private branch exchange lines, it is enabled to connect the

relays

463 and 464 in succession in the test circuit instead of in parallel or in series, so that sufficient energy is secured in the circuit for the energization of these relays.

A connection can be immediately released at any stage of the progress of the selection. In the first instance, a premature release can take place if two second line finders happen to stay on the same terminals, and relays 234 of both cords may become simultaneously energized, whereby the relays 232 may also energize, and the sequence switch 220 of both cords may start from position 1. lVhen sequence switch 220 passes between

positions

1 and 3, the circuit for the high-resistance winding of relay 234 isopened at contactdial.

227 bottom. Relay 234 is not able to maintain its energization over its left-hand winding it the current over resistance 217 is divided in two branches. Relay 234i is thereby deenergized, causing the deenergization of relay 232, whereby the left-hand winding of relay 224 is energized in a'circuit over sequence switch contact 254 top, back content of relay 232, sequence switch contact 229 bottom and contact 263. Relay 224; maintains its energization over its left-hand front contact and left-hand winding, and. hinders the energization of relay 235. Sequence switch 220 is arrested in position 4: in which sequence switch 280 is energized in a circuit, as has been described, and rot-ates until arrested either on the terminals of a free register set, in which relays 23 1 and 232 are energized, or in position 10, whereby when passing position 9:}, a circuit is provided for the energization of sequence switch 220 over contact 289 of sequence switch 280 and right-hand front contact of relay 224. Sequence switch 220 starts from position 4: and completes then its cycle 01 operation without disturbing the calling line, or an engaged register set. When sequence switch 220 reaches position 18, sequence switch 280 is energized over contact 288 bottom and contact 2 14: of sequence switch 220. Sequence switch 280 moves into its position 1.

Then a release is started during the time the searching sequence switch 280 is rotating, not finding a free register, relay 231 is deenergized, and relay 22 i is energized in a circuit over back contacts of relays 231 and 222 and contact 251 of sequence switch 220 in position 4. The calling line is immediately given free, and when sequence switch 280 reaches position 9?}, sequence switch 220 is energized in the circuit over contact 289 of sequence switch 280. The release is completed as has been described. "When a release is started, after the cord has been brought in connection with a free register relay 325 remains deenergized for a longer time than on a last opening at the If relay 325 is not energized when sequence switch329 being started through the energization of relay 323, reaches position 3, relay 334i is energized, sequence switch 320 moves over position 3 and, in passing position 5, relay 3-25 closes a circuit for the energization of relay 339 over contact 348 top of sequence switch 320 and back contact of relay 325. Relay 222 in the cord is energized in a circuit over i'ront contact of relay 339, contact 37 6 top of sequence switch 350, wire 296, contact 286 of sequence switch 280 and contact- 247 of sequence switch 220, so that sequence switch 220 is started from position 5 and moves into position 6. In the meantime sequence switch 350 has been started from position 1 as soon as sequence switch the denergization of relay 222, sequence 320 has reached position 7, and the for relay 222 is opened at contact 376 of sequence switch 350. Relay 222 is deenergized and sequence switch 220 moves into position 7 in which relay 222 cannot become energized since the back contact of relay is opened, so that sequence switch 22 moves over position 7 into position 8, in which the left-hand winding of relay 22 1- is energized in a circuit over sequence switch contact 251 top. In position 3 of sequence switch relay 232 is energized in the circuit over the home contact 269 of the brush carriage, and contact 226 of sequence switch 220. The energization of sequence switch 220 is main tained over the front contact of relay and sequence switch contact 22?. Sequence switch 220 moves over position 3. In positions 9 to 13, the sequence switch 229 is maintained energized over right-hand l'ront contact of relay 224 and contact 227, and in position 17 over front contact oi relay \Vhen the release begins at the time brush carriage of the group selector is r ing, searching for a tree trunk line to a final selector, the energization of relay car switch 220 starts from position 7 and moves into position 8 in which relay 22 is energized. The power magnet 241 remains ergized, whereas the left-ha d winding oi test relay 234 is disconnected at the righthand back contact of: relay The brush carriage continues to rotate without testing the terminals of the trunk lines, and after the brushes reach their position of rest, relay 232 is energized in the circuit over home contact 269, and the sequence switch is advanced over positions 8 to 17 as has been cescribed. Should a release begin at the time sequence switch 220 is in position 9, and the fundamental circuit is extended to the following selector, the energization of relay 359 causes the deenergization of relay Sequence switch 220 is energized in position 9 over back contact of relay 222. In position 10, the energization of sequence switch 220 is maintained over back contact of relay 262. Relay 22% is energized as soon as the sequence switch reaches its position 11.

When the release is started before the dialing is completed, relay 339 is energized in one of the

positions

5, 9 or 12, of sequence switch 320, whereas when the connection is given up at the calling subscriber station after the wanted number has been dialed, but before the selection is completed, sequence switch 320 is energized in position 16 over contact 348 bottom and back contact of relay 325. In position 17, relay 339 is energized in the circuit over sequence switch contact 348 top and back contact of relay 325, so that relay 222 in the cord is deenergized. At contact 3 12 top ot sequence switch 320,

the back contact o1 relay 359 is connected circuit 'to ground and the circuit is established for the resetting of the registers, should they not be in their position 0. I

When a premature release is made at a stage in which sequence switch 220 is in position T, and relay 22a is then energized, sequence switch 220 remains in position 8 until the brush carriage is restored to its position of rest. During all the time the brush carriage is restored, relay 222 remains connected over sequence switch contact 2&6 top to wire 293. It is therefore desirable that the register set shall not be given free and shall not be taken for a new call until contact 2 16 of the cord which has been released is opened. It the sequence switch 350, started from position T after the registers have been restored, reaches position 18 b fore contact 246 of sequence switch 220 is opened, circuit is established for the energization of relay over back contact of relay 323, contact 368 bottom of sequence switch 350, wire 293, contact 2% top of sequence switch 220 and winding of relay 222. Sequence switch 350 is held in position 18 until contact 24:6 is opened, and relay 326 is deenergized.

When the release is started. after the group selector has obtained conn ction with the terminals of a free final, and sequence switch 150 has left position 1 through the closure of the fundamental circuit at the register set, relay 452 is deenergized as soon as the relay 357 opens the fundamental circuit and enables sequence switch L50 to pass over

positions

2 and 5 and to disconnect resistance 442 before the fundamental circuit can be again closed should the terminal of the final immediately be taken by another cord.

The fundamental circuit may be opened at the moment the brush carriage of a final selector has started from its position of rest, and contact 4:57 bottom has not been opened, whereby the brushes may be arrested in the line with the trip spindle. Sequence switch 450 would thereby pass over positions 6 and 11, and when in position 12 the trip spindle is restored in the well-known mannor to its position of rest in energizing magnet 1 18 in a circuit over sequence switch contact 447 top and trip spindle contact 455 bottom, the latches of several brush sets would be released. The circuit of the final selector is thereforeso arranged that whenever its sequence switch 450 passes over positions 8 to 9, a check is made whether the home contact is opened. If this is not the case, relay 452 is energized in the circuit over contact l5? bottom and the power magnet M31 is energized in the circuit over contact 456 top of sequence switch 450 and front contact of relay 452. The brush carriage is moved out until contact li-57 is opened, so that sequence swltch 450 1s arrestedin position 11 and the brush carriage is restored to its position ofrest. In all promature releases the operation of the meter 208 on the allinp; line is hindered through the disconnection of the metering battery 259 at the left-hand back contact of relay 224.

When the dial on the subscriber station is erroneously set up to a higher number than the capacity of the exchange, and the first figure dialed is different from figure l or 2, the register 100 in the exchange takes a position different from position 9 or 0. Should the subscriber notice the error and restore his receiver for a short while, the premature release will take place as has been described, and after the receiver is again removed, the calling line will obtain a connection with another cord. If the subscriber does not notice his mistake, he obtains a connection in the exchange over a special line to the supervisory operator who calls the attention of the subscriber to the error made. If register 100 takes a position different from position 9 or 0, sequence switch 350 cannot start from its position 1 after, sequence switch 320 reaches its position 7, since the circuit for the energization of sequence switch 350 is maintained opened at contact 103 of register 100. Also, registers 110, 130 and 1 10 are hindered from receiving impulses from the stepping relay 325 through the opening of contact 105 on register 100, and these registers remain in their position 0, whereas after each series of impulses from the dial, relay 334 is energized and the sequence switch 320 is advanced to its next position. After the subscriber completes the dialing, and sequence switch 320 moves into position 16, sequence switch 350 is energized in a circuit over contact 363 and contact 341 bottom of sequence switch 320. Sequence switch 350 starts from position 1 and moves into position 3. The fundamental circuit is then closed to the group selector, and its trip spindle when rotating controls the resetting of register 100 to a level corresponding to the first figure dialed. Since the following registers are in their position 0, a number is selected consisting of three figures of which the first is the same as the first figure dialed and the remaining figures are zero. The lines 300, 400 and so on are reserved in the directory, and are connected to the desk of the supervisory operator, and the operator when communicating with the subscriber, knows which first figure the subscriber has erroneouslv dialed.

Each register set is provided with a key ment for delayed signals is provided in the exchange, as shown in Fig. 6. When a reglster is attached to a cord, a guarding lamp 344 lights in the exchange in a circuit over contact 3415 of sequence switch 320. hen sequence switch 320 passes position 2, a circuit is temporarily established over contact 32? bottom of sequence switch 320, the lefthand winding of relay 392 and back contact of relay 393.

Relays

392 and 393 are common for several register sets. One of the windings of relay 395 is thereby energized over sequence switch contact 3&5 top and guarding lamp 344. Relay 392 when energized, provides according to the position of sequence switch 390, a circuit either over its left or its right-hand front contact, its righthand winding, right-hand back contact and winding of relay 393, and left-hand front contact of relay 395. Relay 393 is thereby energized, disconnecting on its left-hand back contact the operative winding of relay 392 and providing over its right-hand front contact a locking circuit for its winding. On the left hand-front contact of relay 393 is the right-hand winding of relay 392 maintained energized. Relay 394, common for a large number of register sets, is connected in a circuit over right-hand front contact of relay 395 to a common interrupter 399. The interrupter 399 provides at given time intervals the closure of the circuit for relay 39 1 which is therefore energized each time the interrupter 399 is closed, and a sequence switch 320 of a register set is in position 3. Relay 394 provides a circuit for the energization of sequence switch 390 over back contact and right-hand winding of relay 398 and front contact of relay 394. The left-hand winding of relay 398 is thereby connected in parallel to sequence switch 390, and the differentially wound windings of relay 398 remain deenergized. Sequence switch 390 is energized, starts from the position in which it happened to stay, and in closing of its local contact 391, provides a shunt around the right-hand winding of relay 398, the left-hand winding of which is then energized. The sequence switch 390 moves in the next position, whereas relay 398 remains energized as long as relay 394 is energized over the interrupter 399. Since sequence switch 390 is arrested in a number of positions, it completes slowly a cycle of operation in a predetermined length of time, while interrupter 399 which is driven from the common power shaft can be comparatively quicker. On

contacts

396 and 397 of sequence switch 390 the energization of relay 392 is maintained until sequence switch 390 starts from position 15 and moves into position 1. When relay 392 is deenergized, a circuit is prepared for the complaint lamp 308 individual to the register set over contact 340 of sequence switch 320, and back contact of relay 392. The closing of this circuit is delayed until sequence switch 390 again reaches position 11 and contact 397 is again closed. The lighting of the lamp 308 before the complaint operator is therefore delayed at least the time necessary for sequence switch 390 to move from position 15 into position 11. If sequence switch 320 passes over position 2 and relay 392 is energized when sequence switch 390 is in a position earlier than position 15, the lighting of the lamp 308 is still further delayed. \Vhen sequence switch 320 in a regular connection leaves position 3, relay 395 is deenergized and the holding circuit for relay 393 is opened. Lamp 308 is not displayed before the complaint operator.

The operator in noticing lamp 308, depresses key 301, whereby the stepping relay 325 of the register set is brought in connection with a dial 302, whereas in bridge to the calling line are now connected the windings of relay 303. The contacts on keys 301 are so arranged that first the dial is connected, then relay 303 is brought in parallel to relay 325, and after that the two circuits are separated. Relay 303 brings over its front contacts the wires 3041 of the operators telephone into connection with the calling line. The operator communicates with the subscriber. whereas the register is maintained undisturbed. The complaint operator through, displaying of the lamp signal 308, also finds a short loop to a subscriber line. If this is the case, she can either directly notify the troubleman, or in operating her dial once, cause the ad Vance of switch 320 to a later position in which a time alarm signal is displayed before the troubleman and in the well-known manner. If the complaint operator finds that the subscriber is not able to set up the register, and having ascertained that the subscriber has not dialed after he removed the receiver the last time, she sets up the register set according to the wanted number from her dial and restores the key 301. The registers then take positions according to the number dialed and control the setting up of the switches for the connection, whereby relay 325 is maintained energized over the subscriber line after key 301 is restored.

WVheri the selection is completed, the register set is released, and the sequence switch of the cord is advanced into the position of a through connection which remains under the control of the calling subscriber.

\Vhat is claimed is:

1. In a telephone exchange system, a subscribers line, a selective switch for extending said line, a controlling mechanism, means for sending series of impulses over the subscribers line to set said mechanism, means controlled by said mechanism for selectively operating said switch, timing means for testing the condition of said line during the transmission of impulses, and means responsive to said timing means for releasing said selective switch.

2. In a telephone exchange system, a subscribers line, a selective switch for extending said line, a controlling mechanism, means for sending series of impulses over the subscriber's line to set said mechanism, means controlled by said mechanism for selectively operating said switch, timing means for testing the condition of said line at the end of each series of impulses, and means responsive to said timing means for releasing said selective switch.

3. In a telephone exchange system, a subscribers line, a selective switch for extending said line, a controlling mechanism,

means for sending series of impulses over the subscribers line to set said mechanism,

means controlled by said mechanism for selectively operating said switch, timing means for testing the condition of said line at the end of each series of impulses, means responsive to said timing means for releasing said selective switch, and means controlled by the release of said selective switch for restoringsaid mechanism to its normal condition.

4. In a telephone exchange system, a subscribers line, a plurality of selective switches for extending said line, a controlling mechanism, means for sending series of impulses over the subscribers line to set said mechanism, means controlled by said mechanism for selectively operating said switches, timing means for testing the condition of said line during the transmission of impulses, and means responsive to said timing means for releasing said selective switches and said controlling mechanism.

5. In a telephone exchange system, a subscribers line, a selective switch for extending said line, a controlling mechanism, means for sending series of impulses over the subscribers line to set said mechanism, means controlled by said mechanism for selectively operating said switch, means operative at a predetermined interval following the transmission of each series of impulsesfor testing the condition of the subscribers line, and means responsive to said last-named means for releasing said selective switch.

6. In a telephone exchange system, a subscribers line, a selective switch for extending said line, a controlling mechanism,

scribers line, a selective switch for extending said line, a controlling mechanism, means for sending series of impulses over the subscribers line to set said mechanism, means controlled by said mechanism for selectively operating said switch, timing means for testing the condition of said line during the transmission of impulses, means responsive to said timing means for releasing said selective switch, and means for restoring said controlling mechanism to its normal condition, the restoration of said controlling mechanism being completed only after said switch has reached a certain stage in the progress of its release.

8. In a telephone exchange system, a subscribers line, a selective switch for extending said line, a controlling mechanism, means for sending series of impulses over the subscribers line to set said mechanism, means controlled by said mechanism for selectively operating said switch, means controlled by said switch for rendering the subscribers line busy, timing means for testing the condition of said line during the transmission of impulses, means responsive to said timing means for releasing said selective switch, and means for rendering the subscribers line idle prior to the completion of the release of said selective switch.

In witness whereof, I hereunto subscribe my name this 5th day of February, A. D. 1919.

LIPA POLINKOWSKY.