US1373447A - Telephone-exchange system - Google Patents

Description

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED $58.12, i920.

Patented Apr. 5, H2L

2 SHEETS-SHEET l.

'UW Pom/f@ WJ/f/ L. POLNKOWSKY.

TELEPHGNE EXCHANGE SYSTEM.

APPLICATION mit FEB. i2, 1,920.

Patented Apr. 5, 1921i.

2 SHEETS-SHEET 2.

Nomils FEYERS. m0,. Lm1o WASHINGTON. D C.

stares earner editrice.

LIPA POLlNKOlSKY, 0F `ANTlitlR7 BELGIUM, ASSGTNOR T0 WESTERN ELECTRIC COMPANYVNCORPORATED, 0F NEW YORK, N. Y., A CORPORATION OF NE YORK.

TELEFHONE-EXCHANGE SYSTEM.

` ricreare.

Specification of Letters Patent.

resented apr. s, reci.

To all w hom t may concern."

Be it'lrnown that l, Liri-r Porinirowsirr, a citizen of Russia, residing at Antwerp, Belgium, have invented certain new and useful improvements in rTelephone-Exchange Systems, oi" which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and particularly to systems employing selectively operable Aswitching devices for establishing talking connections between subscribers lines.

rlhe object or this invention is the provision. ot a switch controlling mechanism comprising a register arranged to respond to a plurality oi series of impulses ifor determining the selection and operation of the automatic switches used in establishing con- 'nections A. feature of the invention relates to a switch controlling mechanism in which a register is positioned responsive to a series of impulses to select one ot aplurality oi automatic switches, and is then again positioned responsive to a succeeding seriesof impulses td control the selective operation of such automatic switch.

Further features of the present invention will become obvious from the following description and appended claims. i

ln the drawings, Figures 1 and 2, taken in ordei, illustrate a portion of a telephone system embodying thev invention. `Figl discloses two subscribers lines together with a pair einen-numerical or finder switches 'flier extending these lines. Fig. 2 shows two selective switchesv joined by means et a linlr circuit with the finder switches in Fig. l and which serve to complete the extension of calling lines to the lines of called subscribers. There is also shown in Fig. 2 a switch controlling mechanism comprising a register for determining the selection and operation ofthe selective switches. f V

The present invention is particularly applicable te small privatebranch exchange systems of therull automatic type where only a comparatively few selective operations` are necessary for the establishment of talking connections. It will `be understood, however, that the invention is not limited to either small capacity systemsk or to systems of the full' automatic type; In

, the disclosure there is shown a switching yarrangement adapted to accommodate a private branch exchange having twenty subscribers lines. These lines are arranged in two groups of ten lines each. All the lines in the first group, such as line 200, appear as callinglines in the multiple contacts oi line finder switches, such as the switch 210. All lines in the second group, such as line 205, appearin the multiple contacts of'line finder switches, such as switch 220. The lindcr switches 210 and 220 comprise a line linding unit arranged to extend any one of the twenty lines to a link circuit 202, 203 and 206. For this purpose the contacts of finder `switch 210, such as contacts 216, 217 and 216 and the contacts of finder v220 such contacts 225, 226 and 227 are connected to the corresponding conductors 202, 203'y andk .206 of the link circuit. When a call is initiated in the first group of ten lines the switch 210 is automatically operatedy to vselect the calling line and extend it toa the thereupon automatically 'selects the calling'f line and extends it to the 203 and r206. Y

rlhe link circuits extending trom the contacts of the line iinder witches, terminate link circuit 202,

in contacts such 284.-', 285 and 286 of the connecting unit. rlhe switch 280 serves to complete connections to one of the groups of ten subscribers lines and switch 290 serves to complete connections to the other 4group often lines..v ln additionto this, two

positions of the switch 290 are reserved for the completion et connections to trunlrlines Vleading from the private branch exchange to the central oilice.

lin manner similar to thearrange-` A switch controllingmechanism comprisi ing a multi-position register is provided for selecting one or the other of theswitches 280 and 290 and also for controlling the operation oit the selected switch to complete the connection to the called line.

broken line are `controlled by switch 290, the

contacts between the two` vertical broken lines are controlled by switch 280, the contacts within `the small broken rectangle in-v closing register 100 are controlled by such register and the reinaining switch contacts are controlled by the sequence switch 250.l

ltis believed that a clearer understanding is to be had of the invention by describing in detail the establishment and release of a telephone connection. For this purpose it is iirst assumed that the subscriber of line 200 in the iirst group of ten lines desires to converse with the subscriber oi' line 208, which is also located inthe iirst group of ten lines. For convenience the lirst group of ten lines is numbered consecutively from 10 to 19 and thev second group of lines is numbered consecutively from 20 to 29. Hence, the iirst, or tens digit of all lines in the iirst group is 1 and the first digit of all lines Vin the second group is 2. Upon renioving the receiver from the switchhook the subscriber of line 200 closes a circuit inroin battery through the winding of coinmon start relay 20st, left-hand winding of line `relay 201, contact and innerI armature oiE cut-oli2 relay 207, over the loop of the calling line to ground at the outer armature and contact of relay 207. Relay 201 attracts its armature and closes a pathi'rorn battery through the winding ci relay 207, right-hand winding and Contact and arinature of relay 201 tothe contact 218 of the Vline iinder switch 200. Relay 20eA by energizing closes a circuit from ground through its contact and armature, conductor 211, Contact 243 (1) of sequence switch 250,

Aarmature and Contact ofrelay 268, winding of slow-toenergize relay 233 to batteryA and ground. A parallel branch of this circuit also closed by way of the armature and and ,establishes the following circuit for operating the line finder switchl 210; batV .tact 213 to ground.

contact 238 (1), contact and armature of relay 233, conductor 222, contact 223, con- The finder switch 210 startsl troni whatever position it happens to be standing in and commences to rotate in search of the calling line. ris the finder switch 210 passes through each of its halt positions the upper contact 213 is closed to ground. @n reaching position 111i the above traced path :troni battery through the wind# ing of cut-oit relay 207 to contact 218 is completed by way of conductor 206, contact 2416 (1), lett-hand winding. of test relay 264, conductor 215, contact 213 to ground, rlhe contact 218 is -so arranged that it is closed in its successive positions simultaneously with closure oi' contacts 213 in theco "responding half positions. Hence, as theiinder switch approaches,position 2 the circuit just traced iseonipleted and re- .lay 207 becomes energized. Relay 264i energizes in the circuit including its lett-hand high resistance winding and completes a holding circuit through its right-hand low resistance winding and front contact and `armature for cut-oil relay 207 and line relay 201. This low resistancecircuit to ground` reduces the potential on contact 218 to ren der the line busy. Relay 264i at its back contac` opens the above traced vcircuit for the'energization oi' relay 239. Relay 239retracts its armature and coinpletes a circuit from battery through the winding of sequence switch 250, contact 2410 (1), back contact and armature of relay 239, contact 238 (1), Contact andarniature ofrelay 233, conductor 222, contact 223, contact 213 (2) l to ground.' Sequence switch 250 advances from position 1 to position 3. lt will be observed Vthat the Acircuit traced from sequence switch 250 depends upon the front contact and armature of relay 233. The ciicuit Voit this relayis Vopened at the armature and contact of relay 204i as soon as the cut-oil relay 207 is operated to open the circuit Voi' said relay 204a Relay 233, however, be-

ing slow to denergize does not release its armature until after relay 239 has had time to denergize and complete the circuit for moving sequence switch 250 into position 3. 0n reaching position 2 sequence switch 250 closes a direct circuit to ground atcontact 219 for niaintaininwr theieneroization of rel lay 207 and relay 201. rThe iinder switch 210is 'thus brought to rest on the contacts of the calling line 200, tlieopcrating circuit of'said Vswitch being opened by the denergization of relay 239.

In position 3 oit the .sequence switch 250 theriinpulse relay 231 is energized in series with the calling'line'zby Ineans of a circuit 'numerals from Oto 9.

and back contact of relay 239, contact 24rd (3), left-hand winding ot relay 239 winding oit i'egistei'100 to battery and ground. A circuit is also closed ytroni battery through the right-hand winding of relay 239, contact'2a1 (3), front contactand armature ot relay 231vr to ground at contact 243. Relay 239, being` differential, does not operate when both of its windings are energized simultaneously. "Ehe register 100, however, becomes energized in series with the left-hand winding oit relay 239 and moves out of position O. Between position and position 1 the master contact "101 01"' register 100 closes a direct circuit to groundY in shunt oft the left-hand winding otdiiierential; relay 239. The current flowing in the right-hand winding ot relay 239 is now suilicient to energize said relay. rlhe register 100 under the control of its master` contact continues to move into position 1.

lt may bewell to explain this point that the register `10() isprovided with ten controlling positions, one foreach of rthe rlhis register` responds-to the series of impulses sentftrom the calling subscribers dial vand advances into a position corresponding vto the number of impulses contained in the series. K rllhe register having assumed la certain position, dependent upon Vthe number of' impulses transmitted, later runs through the remainot its ten positionsto,` normal to control the selection and operation oi the selective switches 280aiid 290. `lt will be seen, thereiitore, that the number ot positions passed through by the register in reaching its norinal position is the complement of the number of impulses sent 'trom the calling subsci'ibei"s dialv tov set theregister. ln order that the switches maybe controlled in accordance withftlie rdi its ot called numbers 'as listed in the diictory, it is oiilynecessary to variraiiigge themsiibscribers dials such that seriesfot inipuses corresponding tothe complements rather' than'fto the actual" l` gits themselves are transiiii'tted to the register.V The'. subscribers dialsv are furtherl arranged such that the last interruption ot the liney in eachimpulse series is comparatively longer than preceding interruptions. The purpose r-'eXplain`ed, to position 1, nothing further occurs until the subscriber commences to Send impulses.,l In position`3 oi' sequence switch 250e. circuit is closed froml battery through thev right-hand winding ot' tone coil 242, contact 276 interrupter 247 to ground. Current flowing iii this circuit produces a .characteristic sound in the receiverat the calling substation to advise the calling subscriber that the apparatus is in condition to receive impulses. The calling subscriber thereupon manipulates his dial 228 to send the tens series of impulses corresi'aonding to the first digit 'ot the called number. Since the called line belongs to the firstN group, the tens digit is 1 and consequently the tens series comprises nine impulses. When the calling line is opened for the first impulse, relay 231 .denergizes The release of relay 231opens the circuit for the right-hand winding of `differential relay 239, which` in turn denergizcs. On the next closure of. the line'circuit at the completion ofthe first impulse, the above traced circuit is established for register 100. This register' advances from positionV 1 into position 2, and the relay 239 is energized, as above eX- plained. At thecompletion of the second impulse, relay 239 denergizes and the register 100 advances into its next. position.

This method ot operation continues until the last impulsev of the 'series istransmitted, yat which time register 100 will have reached Vposition 9. Duringeach brief interruption of the circuit of krelay 231, a circuit is completed from battery through the windings of relay 234, resistaiice212, back contact and armature of relay 231, contact 241s (3) to ground. The relay 2311 being slow to Venergize does not Vattract its armature in response'to the short closures ot-liis circuit.

-At the last' impulse of the series, however, `relay. 231 vremains de'cnergized for a suiiiclosed from battery through the right-hand' winding of relay .239, Contact 241g. (6), bach contact'ancl' armature, of relay 264C to ground. Relay 239 becomes energizedanil closes ay circuit from batteryjthroughf the winding of register 100, Vcontact 102, conta/:t

(6), front contact and armature of rc- `ylay 239,'front Contact and armature 'ot relay sterv 100 Veiiieigizes in this circuit ,and advances from position 9 to its normaly position l0.v

231, contact 243'r to ground.`

lt is not necessary to maintain .sequence 100"will,have suiiicient time to advance switch 250 in position 6 since the register i from either of its positions 8 or 9 to its normal position during the period 4that sequence switch 250 is passing through position 6. Consequently when sequence switch 250 reaches yposition 6 a circuit is closed from battery through the winding of said sequence switch, contact 255v (6 to 7), back contact and armature of relay 234, contact 235 to ground. Sequence switch 250 thereupon advances over position 6 and position 7 into position 9. In passing out of position 6, contacts 244 and245 open the circuit ofthe impulse relay 231. This circuit is 'again energized upon sequence switch 250 Vreaching position 3, and relay 231 isincluded in series with the calling line.

With the sequenceswitch 250 in position 9 and relay 231 energized, a circuit is coinpleted frombattery through the winding of register 100, left-hand winding ot relay 239, contact 240 (8 to 9), backcontactand armature of relay 239, front contact and armature of relay 231,'contact 243 to ground. At the same time the above tra-ced circuit for the right-hand winding of differential relay 239 is closed to ground at contact 243. The register 100 energizes in the above circuit and advances from position 0 into position 1. The calling subscriber now operates his dial in accordance with the units digit.

`The register 100. isiadvanced from position to position, as described, in response to the units series of impulses. On thelast `coniparatively longinterruption of the line, relay 234 attracts its armature and closes va circuit from battery through the winding of sequence switch 250, contact 253 (9), front contact and armature ofrelay 234, contact 235 to ground. ASequence switch 250 moves out of position 9 and into position 10. After relay 234 has become denergized in position 10 of sequence switch 250, a circuit is closed from the winding ofv said sequence switch, contact 255 (10), back contact and armature of relay 234, contact 235 to ground.` Sequence switch 250 thereupon advances from 'position 10 into position 11. In position 11 of sequence switch 250 the selective switch 290, having access to the group of lines containing the called line isstarted in operation. The circuit for operating this switch may be traced f trom :battery through the winding of the magnet of said switch, back contact and right-hand armature of relay 274, back contact and armature of relay 262, contact 255 (11), back Contact' and armaturev of relay 234, contact 235 to ground. Switch 290 movesffrom position 1 over positions 2, l3 ancl'4 and into position 5, positions 2 and 4 being reserved as above noted for central office connections. V Inpassing position 4,3,

contact 293 is closed to complete'a circuit from battery through the windinglof register 100, contact 102, contact 293 (41,), contact 283 closed in position 1, contact 254 (11)baclr'contact and armature of relay 264 to ground. The register 100 energizes in this circuit and moves forward one position. and-in each oi its half positions the contact 293 is closed to advance the register 100 one position. This procedure continues until register 100 has been fully restored to its normal position 0. ln position 0 of register 100 a circuit is closedfrom battery through the winding of relay 234, conductor 229, Contact 104 (0), contact 256 (11) to ground. Relay 234 attracts .its armature and coinpletes a circuit from battery through the windingof sequence switch 250, contact 253 (11), front contact and armature of relay 234,` contact 235 to ground. By means of this circuit the sequence switch 250 moves out of position 11 and.` into position 13.

The selectivel switch 290 is now in the proper position to close the link circuit through Vto the called line by way of contacts'294, 295 and 296. tWhile sequence switch 250 is passing through position 12, a test is made to determine the busy or idle position of the called line 203. The circuit for performing this test may be traced from ground, contact 256 (12), left-hand high resistance winding of test relay 264, contact 246 (4 to 16), conductor 232, contact 296,

237, and relay 261 becomes energized byV means of itshigh resistance winding. Relay 261 attracts its armature and completes a substitute circuit to ground through its right-hand low resistance winding. This low resistance path decreases the potential on the test conductor 237 ofthe called line to render this line non-selectable by other switches. In position 13 of sequence switch 250 a circuit is closed from battery .through the winding of said sequence switch, contact 240 (13), baclr contact and armature of relay 239,'front contact and armature of relay 231, contact 243 to ground. The sequence 'switch 250 moves Jfrom position 13 into position'15.

VTn position 15 of sequenceswitch 250 ringing current is applied to the, called line by means of the following circuit: ringing source 251, contact 266 (15), contact 295 of switch 290, over the lower conductor of the called line 208 and returning by way of The switch 290 continues to iotate.

izo

the upper conductor of the called line to conate in series with the bell at the calledV substation. When the called subscribed removes hisy receiver `from the switchhook, the re- Y tact 294 of switch 290, contact 265 (15) consistance ol' the called line loop is reduced, as is well understood, to permit the energization oi relay 234. Relay 234 completes a circuit from battery through the winding of sequence switch 250, contact 253 (15), 'liront contact and armature of relay 234, contact to ground. Sequence switch 250 advances from position 15 into position 16. Position 16 of sequence switch 250 is the talking position. Battery is supplied to the calling line through the winding of relay 231 and to the called-line throughl the windings of relay 262 and contacts 265 and 266.

After conversation has been completed and the calling' subscriber hangs up his receiver, the supervisory relay 263 is deencrgized. A. circuit then completed from battery through the winding of relay 233, contact and armature or relay 268, contact 243 to ground. Relay attracts its armature and -closes a circuit from battery through the winding of sequence switch 250, contact 253 (16), contact and armature of relay 233, conductor 222, contact 223, contact 13 to ground. Sequence switch 250 advances into position 17.. @n leaving position 16 sequence switch 250 opens at contact' 219 the holding circuit for the line relay 201 and cut-off relay 207. rthese relays become denergized to permit the initiation of iiurther calls by the subscriber of line 200. lVith sequence switch 250 in position 17 and the called line relay 262 denergized, a circuit is closed as follows for the restoration oi' the selective switch 290 to its normal position: battery through the winding of the magnet switch 290, back contact and right-hand armature of relay 274, back contact and armature or" relay 262, contact 238 (17), contact and armature or relay 233, conductor 222, contacts 223 and 213 to ground. IThe switch 290 rotates back to its normal position. As the switch 290 reaches position 18 a circuit is closed from battery through the right-hand winding of relay 262, contact 105 (0) of register 100, contact 293 (18), contact 283 of switch 280, contact 254 (17), baclr contact and armature or' relay 264 to ground. Relay 262 attracts its armature to openthe driving circuit of the selective switch 290. This switch, Vhowever, under the control or its master contact advances into position 1. Vlllhen relay 262 attracts its armature a circuit is established irom battery through the winding of sequence switch 250, front contact and armature of relay 262, contact 238 (17), contact and armature of relay 233, conductor 222, contacts 223 and 213 to ground. 'Sequence switch 250 advances into position 1, in which position relays 262 and 233 are released.

lf the called line 208 is busy at the time sequence switch 250 passes through position 250 a circuit is closed from ground through the interrupter 257, contact 276 (13), righthand winding or tone coil 243 to battery and ground. The interrupter 257 causes the impression oiE a characteristic tone on the calling line to notify the calling subscriber that the called line is already busy. The calling subscriber then replaces his receiver ,to the switchhcok and relay 263 becomes denergized. rllie denergization of relay 268 causes the energization of relay k233 in the manner `alcove described. The selective switch 290 is thereupon restored to its normal position by means of the circuit above traced, including the back contacts and armatures ofrelays 274 and 262 and contact 238v (13). Whenswitch 290 reaches position 18, relay 262 becomes energized as described and closes a circuit from' battery through the winding of sequence switch 250, front contact andl armature of relay 262, contact 238- (13), contact and armature of relay 233, conductor 222, contacts 223 and 213 to ground. Sequence switch 250 advances 'from position 13 into position 15. Since the calling subscriber has replaced his receiver to the switchhook, relay 231 is deenergized and the following circuit is closed for the energization of relay' 234: battery through the winding of said relay, resistance 212, baclr contact and armature of relay 231, contact 243 f (15) to ground. Relay 234 completes a circuit from battery through the winding of sequence switch 250, contact 253 (15) `iront contact and armature or relay 234, Contact 235 to ground. Sequence switch switch 250, front contact and armature of` relay 262, Contact 238 (17), Jiront contact and armature of relay 243, and thence to ground by way of conductor 222 and contacts 223 and 213. thereupon moves into its normal position 1.

Sequence switch 250 The case will now be considered in which it is desired to extend a connection to a subscribers line belonging to the second group of ten lines. These lines are selected` by means of switch 280 and appear accordingly in contacts, such as 234, 285 and 286 of switch 280. To illustrate the operation of the line fin der switch 220, it will be 'further considered in connection with this call that the calling subscriber belongs to the second group of ten lines, one of which lines is shown at 205. The ten lines of the second group appear as calling lines in the contacts ot'tinder switch 220, such as contacts 225, 226 and 227. Upon the removal of the receiver from the switchhook, the line relay 260, individual to the calling line 205,`is operated in series with the common start relay 204. Relay 204 operates in the manner already described to start the line finder switch 210 in rotation. Since the calling line 205 does not appear in the contacts'o the first line vfinder switch 210, this switch will continue to rotate until it reaches position 12. In passing through position' 11, switch 210 shifts the driving circuit from the first line finder 210 to the secondline finder 220. This circuit maynow be traced from ground through the contact 213 (10 to 12), contact 223 (1), conductor 222, armature and Contact of relay 233, contact 238 (1), armature and front contact of relay 239,'contact 249 (1), conductor 221, contact 224, (1), Contact 214 (11), winding of the magnet of switch 220 to battery and ground. rhe magnet of switch 220 is energized in this circuit and moves out of position 1. The finder switch 220 continues to rotate until it reaches the positioncorresponding to the callingline 205 of the second group. circuit is then closed from battery through the winding of cutoff relay 261, right-hand winding and contact and armature of relay 260, contact 227, conductor 206, left-hand winding of test relay 264, conductor 215, coifitact 223 closed in .its off position, contact 2113 (12) to ground. Relay 264 energizesas above described, the finder switch 220 is brought to rest in engagement with the calling lin-e and sequence switch 250 is 'moved into position 3 ready for the transmission of the tens series of impulses.

Since the called line belongs to the second group, the tens digit thereof is 2. Accordingly the calling subscriber transmits a series of eight impulses to set the register 100 in position 8. Sequence switch 250 then moves from position 3 vover positions 6 and 7 and into position 9, `as described. In passing through positions 4 and 5 'sequence switch 250 closes a circuit for the energization or" relay 274 which serves to determine the selection of the proper one of the two se lectivo switches 230and '290. This circuit may be traced from battery through the winding of relay 274, contact 282, contact 106' (8) of register 100, contact 254 (4 to 5), back contact and armature of relay 264 to ground. Relay 274 becomes energized and locks up over a circuit from battery through the winding or said relay, Contact 282, lefthand'armature and contact of relay 274 to ground at contact 235 (3 to 17). The sequence switch 250 in passing through position 6 causes the restoration of register 100, as above explained.

In position 9 of sequence switch 250, th iuiitsimpulses fare sent and register 100 is advanced to its second controlling position.

After register 100 has been positioned the sequence switch 250 advances into position 11. ln position 11 a circuit is closed Jror the operation ot the selective switch 280, which advances under the control of the register 100 to select the terminals ot the called subscribei"s line. This circuit leads from battery through the winding of the magnet of switch 280, front contact and right-hand armature ofV relay 274, back contact and armature of relay 262, contact 255 (11), back contact'- and armature of relay 234, contact 235 to ground. Each time the switch 28() passes through one of its half positions contact 233 is closed. A circuit is established from battery through the winding of register 100, contact 102, contact 283, contact 254 (11), bach contact and armature of relay 264 to ground. Register 100 rotates from position to position in step with the switch 230 until itis restored to normal. ln position 0 of the register 100 a circuit is 'completed from battery through the wind- .ings of relay 234, Contact 104 (0), contact 256 (11) to ground. Relay 234 operates and completes circuit from battery through the winding of sequence switch 250,` contact 253 (11), front contact and armature of relay 234, Contact to ground. Sequence switch 250 advances from position 11 to position 13. From' this point on the operation involved in tho completion of the connection is the saine as that already described.

lVhen the subscribers have replaced their receivers to the switchhools after the completion of conversation, relays 263 and 262 become denergiiaed and relay 233 becomes energized. Sequence switch 250 is driven into position 17 bymeans or" 'a circuit from battery through the winding of said sequence switch, Contact 253 (16), contact and armatureY of relay 233, conductor 222, contact 223, contact 213 (12) to ground. ln position 17 of sequence switch 250 a circuit is closed Afrom battery through the magnet of switch 280, front contactand right-hand armature of relay 274, back Contact and armature of relay 262, contact 233 (17), contact and armature of relay 233, conductor 222,` contac-ts 223 and 213 to ground. The switch 280 rotates back to its normal position, at which time a circuit is closed from battery through the right-hand winding of relay 262, Contact 105 (0), contact 293 (l), contact 283 (18 to 1), contact 254 (17) back contact and armature of relay 264 to ground. Relay 262 encrgizes in this circuit and completes a cir-v cuit from battery throughv the winding of sequence switch 250, front contact and aimature ci relay 262, contact 238 (17), and thence to ground at contact 213. Sequence switch 250, therefore, advances into its normal position 1.

The next time the finder switches 210 and 220 are taken for use, the switch 220 is iirst driven to its normal position 1 from the position in which it was left in connection with the last call.` W ith linder 220 restored to its normal position, the finder 210 isy then started in operation in the manner described to find the calling line, provided such line is one of the lirst group of' lines. 1i the calling line, however, belongs to the second group, finder 210 iirst maires a complete revolution to position 12, whereupon the finder 220 again is set in operation to ind the calling line in the second group. The circuit for restoring the linder switch 220 to its normal position may be traced from battery through the winding or the magnet ot' said finder, contact 224 (2 to 11), conductor 221, contact 249 (l), front contact and armature of relay 239, contact 238 (1), contact and armature of relay 233, conductor 222, contact 223, contact 213 (12) to ground.

Ars hereinbeiore stated, positions 2 and 4 of the selective switch 290 are reserved for central office connections. Two trunks 270 and 271 leading to the central otiice are shown as connected to contacts 297, 298 and 299 of switch 290 in positions 2 and 4 re spectively. 1n order to make a central ofi-ice, the calling subscriber operates his dial to transmit ten impulses. ln response to this ,series of impulses the register 100 makes a complete revolution and stops in position 0. When, therefore, the sequence switch 250 passes through positions 4 and 5 in the manner explained, a circuit is completed from battery through the windinO o1' the magnet of switch 290, contact 103 0), contact 254 (4 to 5), baclr Contact and armature of relay 264 to ground. The switch 290 advances into position 2 where the central oiiice trunk 270 is tested. rThe` test circuitrfor this purpose may be traced from the test conductor 272, contact 299 (2), conductor 232, contact 246 (4 to 16), through the left-hand winding oi' test relay 264, contact 256 (7) to ground. The sequence switch 250 will have moved over position 6 and into position 7 in the manner hereinbefore described. lf trunk 270 is found idle, relay 264 energizes. Relay 264 including its right-hand winding and the test circuit reduces the potential on test conductor 272 in order to render the trunk busy to other switches.,A `When the sequence switch 250 passes through position 6 relay 234 energizes in a circuit trom battery through the windings or saidy relay, conductor 229, contact 104L (0), contact 2.56 (6) to ground. Relay 234 remains locked up in position 7 of sequence switch 250 by means of a circuit from battery through the windings of said relay, resistance 212, contact 236 (7), iront contact and armature of relay to ground at contact 235. The calling subscribers line is connected through to the central or'iice trunk 270 withsequence switch contacts 244 and 245 closed in position 7, and the further extension of the call may be made in the usual manner.

At the completion of conversation the calling subscriber by replacing his receiver on the switchhook causes the decneigization of supervisory relay 26S., Relay 233 there'v upon energizes by means of a circuit from battery through the windings of said relay, contact and armature of relay 268, armature and back contact of relay 231, contact 236 (7), front contact and armature oiE relay 234 contact 235 to ground. Relay 233 com- Jletes a circuit from batter through the winding of sequenceswitch 250, contact 253 (7), contact and armature of relay 233, conductor 222, and thence to ground at contact 213. Sequence switch 2.30 moves into position 9. ln position. 9 of sequence switch 250 relay 234 is energized by means of a circuit from battery through the windings oi said relay, resistance 212,'back Contact andarmature of' relay 231, contact 243 .to ground. Relay 234 completes a circuitrom battery through the winding of sequence switch 250,

contact`253 (9), front contact and armature of relay 234 to ground at contact 235. Se quence switch 250 moves out of position 9 and into position 10. 1n position 10 of sequence switch 250 a circuit is completed from battery through the winding o1 the magnet of switch 290, back contact and right-hand armature of relay 274, back contact and armature of relay '262, contact 233 (10), contact and armature of relayy 233 to lground at contact 213. Switch 290 restores to its normal position, at which time relay 262 is energized in the manner above described. Relay 262 by attracting its ar-` mature closes a circuit from battery through the windingo'f sequence switch 250, front contact and armature of relay 262, contact 238 (10), contact and armature of relay 233, and thence to ground at Contact 213. Sequence switch 250 thereupon advances into position 11. Inthis position a circuit is closed from battery through the winding of sequence switch 250, contact 253 (11), front contact and armature of relay 234 to ground at contact 235. Sequence switch 250 moves from position 11 into position 13. 1in position 13 of sequence switch 250 relay 262 is energized in a circuit from battery through the right-hand winding of said relay, contact 105 (O), contact 293 (1), contact 283 (l), contact 254 (13), back contact and armature of relay 264e to ground. Relay 262 closes a circuit from battery through the winding of sequence switch 250, front contact and armature oi' relay 262, contact 238 (13), contact and armature of relayv233, and thence to ground at contact 213. Sequence switch 250 moves into position 15 where a circuit is closed from battery through the winding o'i sequence switch 250, contact 253 (15), iront contact and armature of relay 23a to ground at contact 235. Sequence switch 250 advances into position 16. In this position ot sequence switch 250 a circuit is completed from battery through the winding ot said sequence switch, contact 2523 (10), contact and armature of relay 233 to ground at contact 213. Sequence switch 25() thereupon moves into position 17. n this position relay 262 is energized in the circuit above traced and completes the circuit already described for driving sequence switch 25() into its normal position.

What'is claimed is: i

1. ln a telephone system, a plurality of selective switches `for establishing telephone connections, a multi-position register, means for sending series ot' current impulses, impulse mechanism responsive to one of said series oi impulses tor variably setting said register, means controlled by said register when in its set position Jior selecting one of said switches, said impulse mechanism being responsive to another series of impulses for again setting said register, and means controlled by said register in accordance with its subsequent setting for operating the selected switch.

2. ln a telephone system, a plurality of selective switches for establishing telephone connections, a multi-position register,means for sending series of currentimpulses, impulse mechanism responsive to one of said series of impulses for variably setting said register, means controlled by said register when in its set position for selecting one of said switches, means for thereupon re storing the register to its normal position, Said impulse mechanism being responsive to another of said series of impulses for again setting said register, and means controlled by saidregister in accordance with its subsequent setting for operating the selected switch.

3. In a telephone system, subscribers lines, selective switches for interconnecting said lines, a multi-position register, means for sending series ot' impulses over said lines,

series or impulses for variably setting said register, means controlled by said register when in its set position for selecting one of said Switches, said impulse mechanism being responsive to another series or' impulses for again setting said register, and means controlled by said register in accordance with its subsequent setting for operat ing the selective switch.

4E. In a telephone system, subscribers lines, selective switches tor interconnecting said lines, a multi-position register', means for associating said register with a subscribers line, means for sending series of impulses over said line, impulse mechanism responsive to one of said series 'of' impulses for varia bly` setting said register, means controlled by'said register when in its set position for selecting one of Said switches, said impulse mechanism being responsive to another of said series of impulses for again setting said register, and means controlled by said register in accordance `with its subsequent set ting for operating the selective switch.

5. In a telephone system, subscribers lines arranged in groups, aplurality oi? selective switches one individual to each of said groups for interconnecting the subscribers lines, a multi-position register, means for as- Vsociating said register with a subscribers LIPA POLINKOVVSKY.

impulse mechanism responsive to one oiv said y

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