US1580630A

US1580630A - Telephone-exchange system

Info

Publication number: US1580630A
Application number: US698635A
Authority: US
Inventors: Walter P Albert
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1924-03-12
Filing date: 1924-03-12
Publication date: 1926-04-13
Anticipated expiration: 1943-04-13

Description

A ril 13, 1926.

W. P. ALBERT TELEPHONE EXCHANGE SYSTEP A Flled March 12. 1924 4 Sheets-Sheet 1 rate-ates; Apr. l3,

UNETED STATES insane PATENT OFFICE.

WALTER P. ALBEET, @IE EAST ORAIJGE, NEXV JERSEY, ASSIGNGE TO WESTERN ELEC- ERIC COMPAETY, II'TCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEVI YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed March 12, 1924. Serial No. $98,635.

To all whom/i1; may concern Be it known that I, WALTER P. ALBERT,

.. ate of New Jersey, have ineitam new and useful Improvements in Tclephoneddxchange Systems, of

which the following is a full, clear, concise, and exact des ription.

'lms invention relates to telephone exchange systems and moreespecially to such systems as make use of automatic switches in. the estal'ilishing and extending of connec-. tions.

The object 0:1": the invention is an improved means for registering the designations and ling the operation of a connector switch, the

latter being independent of the sleeve conductors oi": the called lines.

A further featiui'e of the invention is the use 0% a. register mechanism for controlling the operation of a connector switch, and tor maintaining a seized called line non selectable by other connector switches.

Another feature of the invention relates to connector switch which hunts for amarlred group oi: lines and then hunts for a particular one of a plurality of individual ly marked lines, this particular line being determined by the previously marked group.

Other features and advantages will be ap.- parent after a consideration of the follow:

ing detailed description and the appended claims. The figures of the drawing when a are ranged in the manner shown in Fig. 5 disclose a preferred means for carrying out the invention.

Fig. 1 discloses a number of subscribers lines and one of a plurality of central o'flice trunks with associated controlling mechanism. In addition there isshown an auto: ratio switch for connecting subscribers lines to the trunks. This tig'ure also shows an attendants line circuit by means of which incomin calls may be extended to local stations.

Fig. shows in adrlitiento aot the United States of America, c Grange, 1n the county of subscribers lines, a finder switch and a connector switch. This figure also shows one of a number of link circuits'with certain controlling apparatus. for interconnecting local subscribers lines.

Fig. illustrates a register switch and a register relay mechanism associated with a .central office trunk.

Fig. t illustrates a register switch and recording mechanism associated with a linkcircuit, and similar to the register mechanism of Fig. 3.

General description.

The

finder switches

100, 200 and connector switch 269 are all of the same type, each switch consisting or": a plurality of banks of terminals and cooperating wipers. These wipers are further divided in two sets which scribers lines. lhe talking and testcon-' ductors oi each line have an appearance in different banks of contacts or" the finder switches 100 and 900. Thus the tip, ring and. sleeve conductors of the first group of lines are terminated in the first of three banks of contacts while conductors of the second group of lines are to 'minated in the second three banks. The sleeve conductors are also multipled through contacts of cutolt rela'ys'to appear in contacts of the register relays shown in Figs. 3 and l.

When one local subscriber desires to converse with another local subscriber, theremoval of the receiver causes the finder switch 100.150 hunt for and connect the calling line with an idle link circuit. The transmission of the tens series of impulses positions the brushes of register switch 400 on the proper set of tens terminals and the corresponding register relay is operated. During the comparatively long period followingthe transmission of the tens impulses the brushes of switch 400 are automaticall advanced to the next resting position. In the drawing this is shown as the No. 5 set of terminals. The

. callingsubscriber upon dialing the units switch to be adranced to the proper set of units contacts. The test or sleeve conductor of the called line is now connected through a right front: contact of the operated register relay, units contact and brush 4-27 of switch 400 to the winding 01'' test relay QlS) which operates it the called line is busy, causing busy tone to be transmitted back to the calling subscriljier. Should, however, the called line be idle the connector switch 200 is operated, to hunt for the set of terminals marked by register switch L00.

The ralled lines, it will be observed, are arranged in groups, each group being provided with an identifying contact in the ranks E203 and 20 i. in accordance with the operation of a particular one of the register relays shown in Fig. l the proper group contact is marl-zed and when this contact is reached, relay 923 operates thus bringing the brushes oit switch 200 to rest. Alter a short interval, the switch 260 is again operated to hunt for the particular units contact in the selected group, this units contact having been marked by means of ground extended over conductor 251 to brush 4:20 and thence to the particular units terminal in banks 263 and Qtil. 'lVhen the brushes of switch 260 reach the terminals corresponding to the called line, relay 22 again operates and brings switch 260 to rest. Connecting relay 220 now operates to connect the calling and called lines.

l hen a local subscriber desires to converse with a subscriber reached by means of the cent al otiicc the number 11 is dialed. The operation is similar to that alrcat. y described as far as the point where register switch 400 is positioned. The setting of switch 400 in this case, causes the operation of relay 228, thus releasing the link circuit and operating a starting relay associated with the first idle outgoing trunk. A circuitis then completed for operating finder switch '100, the calling line previously hav ing been n'iarked by battery connected through the right front contact of cut-off relay 202. A test relay l is now connected in series with the winding of the cut oil relay but does not receive su'llicieut cur rent to cnergize.- However, when the termin. s ot the calling line are reached, battery is connected througl the back contact of relqr 108 in pa allel with the \Yllltlll ig ot' cut-oft relay, thus providing suihcient current to operate relay 10}. The brushes oft switch 100 are new brought to rest upon the terminals oi the calling line. Subsequently 'cLay 105 operates thus completing connect 1 a ot the calling subscribers line rith the tral otce trunk. The ('RllTP- subscriber now proceed to one verbally the numo't' (l"SllQ(l line in the case of a I or to dial the same in the :ase anicaloliice.

O11 calls incoming from the central ofiice the attendant is signaled by means of the ighting of lamp 140. The attendant answers by operating key 170 and receives the number oi the desired station from the central otlice operator. Immediately thereafter a key 100 is operated and the number of the wanted station is dialed over the attendants line circuit 190. The transmission of the tens and units impulses causes the brushes of switch 300 to be set in a manner similar to that described in connection with register switch shit), the p 'oper one of the register relays shown in Fig. 3 being oper ated. As soon as the attendant commences dialing, switch 100 is operated to find the calling line which is marked by means ot 21 units contact of switch 300 and a front contact of the operated register relay. lVhen the terminals corresponding to the called line are reached, relay 10% operates in the same manner as described in connection with an outgoing call, thus bringing the brushes of switch 100 to rest.

Detailed description of a local coll.

hen a calling subscriber, as the sub scriber at station 101, desires to talk with another local subscriber, removal of the re ceiver from the switchhook causes the line relay 201 to operate from battery through its right hand winding, left inner contacts of cut-oil relay 202, ring side of the calling line, through the subscribcfis substation apparatus back over the tip side of the line, le'lt outer contacts ot relay 202 to ground through the left winding of relay L Relay 201 at its right inner armature connects battery throturh resistance 203 in parallel with the winding of relay 202 to the sleeve conductor of the calling line, thus raising the potential of a particular one oi" the set of contacts with which brush 210 cooperates.

Relay 201 also connects ground through outer armature and contact to the starting wire 206 and thence through the out-er armature and back contact of relay 20 to batterythrough the winding ot starting relay 205. Relay locks in a. circuit traceable from battery through its winding, arma ture and locking contact thereof, outer armature and contact of relay 912 to ground at the inner armature and contact of rblay 20-l. ll the partiular link shown in Fig, had heel busy, relay 204, ii'ldividiutl thereto, would he in operated condition and the start ng wire 208 would be extended thrimgh the oulcr front contact of relay 20-1 to operate the starting relay ssociated with the next idle link. li hen relay F205 closes its left outer armature it connects ground thrc h the armature and back contact of test relay 207, outer armature and contact oi relay Ti interrupter contacts and winding of step ping magnet 1209 to battery. Stepping mag- (ill nects net 200 is energized in an interrupted mannor in this circuit and steps the brushes of the line tinder switch 200 until the set of terininals is located in which the calling line terminates. ll hcn this particular set of terminals is reached, a circuit is completed from batter through the winding; o'lf relay and the resistance 20.3 in parallel, brush 210 and cooperating contact, winding of relay 207 to ground at the armature of relay 205. Relay 20'? operates in this circuit and breaks the energizine' circuit of stepping magnet 209, thus causing the brushes of switch 200 to come to rest on the set of terminals in which the callingline tcr ni ates, but relay 202 which marginal, does not operate in this circuit. Belay 20'? also extends the above traced ground through its armature and front contact, to battery through the winding of relay 208, which locks in a circuit from battery through its winding, armature and locking contact, lettt outer armature and contact ot. relay 228 to the grounded conductor 25%. The operation of relay 208 connects the calling line to the windings of the impulse relay 211 which operates. Atthis time ground is extended through the left middle armature and contact of relay 20S, conductor 255, brush 210, to battery through the winding of cut-oil relay 202' which now operates and renders the calling The operation of relay 202 alsoline busy. causes the release of the line relay 201.

It willbe observed that had the brushes of switch 200 been at rest on a set of terminals in advance of the set corresponding to switch 200 would necessarily have been rotated throughthe calling line. the brushes of almost a complete revolution before relay 202 operates to comp ete the dialling circuit. .3y means of relay 212, however, this t me interval may be rendered comparatively 1napprecialfle. When brush 220 reaches the last one of the associated bank of terminals (terminal .tt22) relay 212 operates "from battery through its winding, brush 220 and cooperating terminal #22 winding o't testrelay 207 to ground at the armature (rt re ay The operation of relay 20? closes the above traced circuit for operating relay 208 which in turn closest-he impulsing circuit as before described. The turther stepping of the switch 200 to the terminals ot the calling; line is accomplished as n'criously described, Thus by means of relay 212 the dia" circuit may be completed beforethe brushes oii switch 200 have connected with the calling line. I

lVhen relay 21.1 operates subsequent to the operation of relay 208, an obvious energizing circuit is closed for the slow releasing relay 213 which in turn closes an obvious circuit for the holding re ay 21%. Belay 21s; con- (rround through its left outer armature iratcd, this re purpose maybe traced as of relay 21.6.

crates and transfers the starting wire 206 to the next idle link. The locking circuit of the starting relay 205 was opened by the operation of relay 204, the former relay now releasing. However, a substitute holding circuit is provided for relay 20S extending from ground at the left inner armature and contact o't relay 21 1, conductor 254, left outer armature and contact of relay 22S, armature and locking contact and winding of relay 208 to battery.

The calling subscriber now dials the tens digit of the wanted station. Relay 211 follows the impulses in the well known manner. 1186111119 that the number of the desired eta tion is Vi hen relay 211 releases a re sult of the first opening of the line circuit ground is connected through its armature and back Contact, ri ht outer armature and contact of relay 214-, winding of relay 21f, conductor 250, to battery through the winding; of stepping magnet 401. il hcn stepping magnet- 401 releases as a result of the reoperation of relay 211, the brushes of register switch are advanced to the No. 1 set of. terminals. In a similar manner the transmission of the second and third impulses of the tens series, advances the brushcs 01: register switch 100 to the No. 3 set of terminals. At the termination of the cone paratively long period following the transmission 01 the tens digit, slow relay 215 releases and closes a circuit. from ground at the right inner armature and contact of re lay 214-,

right normal contacts of relay 215, left outer armature and back contact of relay conductor 25.1, brush l20 and terminal No. 3 of re ter switch 41-00, conduc tor 51, winding'of 1x ister relay 402, to ates and extends this same ground throur its armature and locking; contact, conductor to battery through the winding of relay 216 which locks to ground at the arn'iature and contact oi relay 213. With relay 216 operated, a circuit is completed to stepping magnet 401 to advance the brushes of switch 100 to the next resting position. l n the case illus ar position would be the lie. 5 set of terminals. The circuit for this follows through the winding iping'ma conductor 250, left inner arr turc contact relay 21h, conductor 2 1., armature and. contact of magnet 401, brush -l21 of register switch 100, conductor 4:52 to ground at the left outer armature and front contact ll hen the No. set of tern' inals is reached. the above traced circuit is opened and the brushes or: register switch 41-00 come to rest.

The callin' subscriber dials the units di of the desi l station. At the first ope c5 ct the line circuit, relay and the i net energize asbefore lescribed. he so. u

as relay 215 operates, ground is extended through its right armature and front contact, right outer armature and contact of relay 216, to battery through the winding of line test relay 217 Bela-y 217 operates and closes an obvious energizing circuit for relay At this time ground is extended through the right inner armature and contact of relay 21h middle armature and con tact of relay 217, through the right hand winding of relay 225 to battery. Belay 225 locks in a circuit from battery through its left winding arn'iature and locking contact thereof, right armature and contact of relay 232, right armature and back contact of relay 219 to ground at the armature of relay 214-. Since the units digit of the called line is assumed to be 5, the line circuit is opened. a corresponding number of times and regisic-r switch $00 will have its brushes positioned upon the No. 5 set of units terminals.

At the termination of the. units dialing, rclay 215 and magnet 4:01 release. The release of relay 215 opens the original energizin circuit of test relay 217. efore relay 217' retracts its armatures and assuming that the called line is busy, a circuit is closed from battery through the left winding of relay 219, inner armature and front contact of relay 217, left normal contacts of relay 215, conductor 252, brush 427 of register switch 400, conductor 458, right hand contact No. 5 of register relay 402 to the groundrd sleeve conductor of the busy line. It should be observed that all the right hand contacts of the register relays shown in Fi i and 5 are connected, by means of multiples, through the right front contacts of cutoff relays, to the sleeve conductors of the different lines. Thus, the sleeve conductors of the first group of lines are multipled to the right front contacts of register relays 395 and 1-05. In a similar manner, the sleeve conductors of lines in other groups are multipled to appear in right contacts of the corresponding register relays. hen relay 219 operates in the above traced circuit it also locks through its right-hand winding, right armature and locking contact, to ground at the right inner armature and contact of relay 214;. A distinctive tone is thereupon transmitted to the calling sub-- scriher from the tone source 257, left outer armature and front contact of relay 219, (InlrClQHSQl' 229, ring side of the line and thence to the calling subscriber, notifying him of the busy condition of the wanted line.

FShould, however, the called line be idle when relay 215 releases the second time, there being no ground potential on the sleeve conductor of the called line, relay 219 will remain normal and thus allow testrelay 217 to release. The release of relay 217 opens the original energizing circuit of relay 218 which does not release, however, since it is now locked in a circuit traceable from ground at the r ght inner armature and contact of relay 21 1, right normal. contacts of relay 215, outer armature and front contact of relay 218, left outer armature and back contact of relay 221 to battery through the winding of relay 218. After a short interval when relay 217 releases, it connects ground through its inner armature and bacl: contact, through the left normal contacts of relay 215, conductor 252, brush 127 of register switch 100 and thence through the contact of relay 102 to the sleeve of the called line, rendering this line busy to other calling stations. Should the connector switch 260 when relay 217 releases oe resting upon a set of terminals not in the group assigned to lines having a tens digit of 3, a circuit is closed from battery through the winding of stepping magnet 222, armature and contact thereof, armature and back contact of relay 223, inner armature and front contact of relay 218 to ground at armature of relay 217. Stepping magnet 222 continues to operate in this circuit until the set of group terminals allotted to called lines having a tens digit of 3 is reached. V lhen this set of group terminals is reached, relay 223 operates in a circuit traced from battery through its winding, brush 23-1 of connector switch 260, third group identifying terminal thereof, conductor 253, left outer armature and front contact of register relay 102, couductor 4153, to ground at the right outer armature and back contact of relay 22 1. Relay attracts its armature and breaks the operating circuit for magnet 222, thus causing brush 23 1 of switch 260 to come to rest on the marked group terminal. At the same time a circuit is completed from battery through the winding of relay 224:, right armature and back contact of relay 22 armature and front contact of relay 223, inner armature and front contact of relay 218 to ground at the outer armature and back contact of relay 217. The operation of relay 224: causes the release of relay 223. When relay 223 releases, relay 224; looks in series 'ith the winding of relay 221 which operates. lVhen relay 221 operates a circuit for operating stepping magnet 222 similar to that above traced. is completed, ground being supplied through the inner front con tact of relay This same ground is extended through the out-er armature and front Contact relay 224, conductor 251, brush 20 and units contact No. 5 of register switch 1-00, conductor 159 thence to units terminal No. 5 in group No. 3 of bank This serves to mark this particular units terminal. Stepping magnet 222 continues to operate in the above traced circuit until the particular set of terminals is reached, which has been p io sl ma ked by a n sf ister switch 400. When this set of terminals is reached, relay operates in turn bringing the brushes of switches 260 to rest.

lVhen relay 221 operates in series with the winding of relay 22 t the locking circuit for relay 218 is broken and this relay releases. A. circuit is now completed for the relay 226 traceable from battery through its winding, right armature and trout contact of relay 221, armature and front contact of relay 223 to ground at the right inner armature and front contact of relay 22 i. Relay 220 operates in this circuit and immediately closes a locking circuit for itself from loattery through its armature and locking contact to ground at the right inner armature and contact of relay 214. Relay 226 in operating causes the successive release of

relays

224, 221 and 223.

When relay 226 operates, the calling subscribers line is extended by means of the link circuit to the called subscribers line. Ringing current is supplied from the source 261, winding of relay 232, right inner armature and front contact of relay 225, ring side of the link, right inner armature and front contact of relay 220, brush 231 and cooperating contact, thence over the ring side of the called line and through the subscribers ringing apparatus back over thetip side of the calling line, brush 230 and cooperating contact, right outer armature and front contact of relay 226 to ground at the right outer armature and "front contact of relay 225. When the called subscriber removes his receiver from the switchhook the resistance of the circuit above traced in series with the winding of relay 232 is reduced and this latter relay now operates and at its armature and Contact breaks the locking circuitfor relay 225 which releases and disconnects ringing current from the call-ed line. Talking current is furnished the called subscriber through the windings of retardation coil 238 which is bridged across the outgoing end 01' the link.

It will be observed that when relay 218 released as a result of the operation of relay 221, ground was connected through the right outer contact of relay 217, left inner arn'iature and back contact of relay 218, left inner armature and front contact oi? relay 221., to battery through the winding of relay 270. Relay 270 attracts its armatures and connects ground to each of the group identifying contacts in terminal banks 263 and 26 i. The purpose of grounding these several contacts is to confine the units hunting operation of switch 260 to the particular group of contacts first selected. Thus, it for any reason brush 28 12 in its rotation fails to make contact with the marked units terminal, the brushes will be advanced to the next group identifying contact upon which ground is found, thus causing relay 223 to operate and prevent further hunting in the next group of contacts. This is necessary since all the units contacts are ,inultipled, the marking of one contact also marking a corresponding contact in each of the other groups; thus failure to select the properfline in one group might result in the selecting o1? acorresponding line in another group.

Disconnect-ion.

Following the conversation when the calling subscrlber replaces his receiver upon the switchhook, relay 211' releases, in .turn re leasing relays 21 21 i, 204:, 208, 216, and 402. After a short interval when relay 213 closes its normal contacts, ground is extended over conductor. 258, brush r21 of register switch 400, armature contact of step pln contact e01, conductcr256, leit inner armature and back contact of relay 210. winding of relay 215, conductor 250, back through the winding of stepping magnet 401. Magnet e01 continues to rotate the brushes of register switch e00 until the normal posltion is reached at which time the 7 above traced circuit is broken and switch 400 comes to rest.

All the relays associated with the link are now 1n normal condition thus rendering the link selectable in connection with another local' call.

Outgoing central office calls.

lVhen a local subscriber desires connection with the central oliice, a special code is dialed. In the case illustrated this is 11. The sequence of operations when this mun-- ber is dialed is similar to that for a local call.- In this however, register switch 400 Wlll have its brushes positioned upon. the No. 1 set 0t units terminals and register relay l05 will be operated.

lVhen, therefore, relay 215 releases the termination of the dialing of the units digit a circuit is completed from battery at, the outer armature. of relay through the right hand winding of relay 228, coi'nluctor 259, right hand contact No. l of l'GlzljgdUS, brush 427 and cooperating contact, conductor 252, left normal contacts oi relay 215 to ground at 7 armature and back' contact of relay 217. Relay 228 operates in the above traced circuit and locks through its left winding, le'l t armature and back contact of relay 102 to ground at. the right outer armature and back contact of relay 108. At the same time relay 228 closes an obvious operating circuit for common relav 227 which operates thus preventing more than one calling subscriber being simultaneously connected with an outgoing trunk.

WVhen relay opens its left outer armature and back contact the locking circuit of relay 208 is broken and this latter relay now releases. The release of relay 208 causes the successive release of

relays

211, 213, 214, 216, and the restoration of the register switch 400 to its normal position as already described under Disconnection. The link however, is not completely released since relay 201 is held operated by ground at the left middle armature and contact of relay 228. ll hen relay 228 closes its right inner armature and contact it connects ground to the winding of relay 103 which operates. The operation of relay 103 connects ground to the ring side of the trunk serving as a slgn'al to the central oiiice. At the same time ground is extended through the leftouter armature and contact of relay 103, left armature and back contact of relay 104, left armature and back contact of relay 105, armature and contact of magnet 106 to battery through the winding of the same. Magnet 106 steps the brushes of the finder switch until the set of terminals corresponding to the calling line is reached, whereupon a circuit is completed from battery through resistance 107, left armature and back contact of relay 10S, brush 110, and cooperating contact of switch 100, sleeve conductor of the calling line and thence in parallel with battery through the winding of relay 202, brush 210 and cooperating contact, right outer armature and contact of relay 228, right normal contacts of relay 102 to ground through the winding of relay 10 1. Relay 104: receives suflicient current in this circuit to cause its energization, resulting in the releaseof stepping magnet 106. The operation of relay 10st closes a circuit from battery through the winding of relay 105, right normal contacts of relay 10 8, armature and front contact of relay 104, to ground at the left outer armature and contact of relay 103. The operation of relay 105 connects the called line through the normal contacts of relay 113 with the winding of relay 111 which operates. Relay 111 at its left armature provides a substi-- tute holding ground for relay 103. At its right armature relay 111 closes an obvious opera-ting circuit for slow release relay 112. Vith relays 111 and 112 operated an energizing circuit is completed for relay 113 which locks in a circuit traceable from ground at the left outer contacts of key 160, right armature and contact of relay 112, armature and locking contact of relay 113 to battery. When relay 112 attracts its armatures, a circuit is also completed from battery through the winding of relay 108, left armature and contact of relay 112, right normal contacts of relay 117, to ground at the left outer contacts of key 160. Relay 108 operates and connects ground through its left armature and contact, brush and cooperatingcontact, to the sleeveconductor of the calling line to render it busy to other calling subscribers. Relay 108' connects ground through its right outer armature and front contact to the winding of relay 102 which operates and renders the selected trunk busy to other calling stations. When relay 102 operates it breaks the original lock ingcircuit for relay 228 which releases, in turn releasing relay 227 to thereupon allow the association of other calling lines with central office trunks.

The calling line is now connected through the contacts of relays 105 and 113 with the central oiiice trunk and the calling subscriber may proceed to dial the number of the desired line in the case of an automatic ofiice or give the number verbally in the case of a manual oflice. lVhen the connection of the calling line with the central otlice has been completed, supervisory relay 11st operates in a well known manner from a source of battery and ground at the central otlice. Relay 111 closes an obvious circuit for relay 115 which in turn closes the circuit of relay 116.

R'elay llt at its left armature provides a substitute holding ground for relay 112.

When the calling subscriber disconnects, relays 11 i, 115 and 116 release in succession, causing the supervisory relay at the central office to release, as a disconnect signal. The release of the trunk is now under control of the central oilice since relay 120 is bridged across the trunk through the outer back contact of relay 116. Relay 120 at its armature provides a holding circuit for relay 112. However, when disconnection takes place at the central oilice, relay 120 releases causing the release of the trunk circuit and all the operated relays associated therewith.

Incoming calls.

lVhen the central oiiice trunk is connected to, either manually or as the result of seizure by a. connector switch, relay 120 operates through both windings in series. since it is bridged across the trunk through a back contact of relay 116 and a normal contact of key 101. Relay 120 in energizing. closes an obvious operating circuit for slowrelease relay 112. Relay 112 con'ipletes a circuit from battery through the right hand winding of relay 120, right armature and contact of relay 128, right armature and contact of relay 112, to ground at key 100. Relay 12S) operates in this circuit and coinpletes a locking path through its left hand winding, left armature and locking contact. right armature and contact of relay 102;, right inner armature and back contact of relay 131, right mature and contact of relay 112 to ground at key 160. 'Vhen ringing current is applied to the trunk, relay 118 operates through its left winding in series with the condenser 11$). Relay 11S closes-a locking circuit for itself from battery through its right hand winding, right armature and locking contact, left inner armature and back contact of relay 121,

left normal contacts of relay 122, right armature and contact of relay 112, to ground at key 160. This last traced ground is also extended through the left armature and contact of relay 118, causing line lamp 140 to be illuminated as a signal to the attenz'lai'it. The attendant answers by operating key 170 which causes the talking set 180 to be connected through the normal contacts of relay 123 with the outgoing end ot' the central oilice trunk. The operation of key 170 also completes an obvious operating circuit for relay 121. wlfich locks in a circuit from battery, through its winding, left inner armature and locking contact to the previously traced ground key 160. The operation of relay 121 causes line lamp 1&0 be extinguished and retardation coil 127 to be connected in parallel with the right hand high resistance winding of relay 120.

Having learned the number of the wanted station the attendant operates key16O causing relay 123 to attract its armatures. When relay 123 operates, the attendants line circuit 190 is disconnected from the outgoing end of the trunk and is transferred to the local end thereof, resulting in the operation of relay 111 through the normal contacts of relay 113. Relay 111 at its left armature connects ground through the left inner armature and, back contact of relay 103 to battery through the winding of relay 1241 which operates. Relay 12-1 completes an obvious operating circuit for relay 117. Re-

' lay 117 at its left inner armature connects ground through the winding of relay 12:) to battery at the armature of relay 227. Relay 125 operates and completes an obvious energizing circuit for relay 227 thus preventing simultaneous seizures of this central ofiice trunk. Relay 125 also looks from battery through its right winding,

right armature and locking Contact, rightouter arn'iature and contact of relay 117 to ground at the right outer armature and back contact of relay 198. At this time relay 102 operates to render the central oh ice trunk busy. The circuit for this purpose may be trace; from battery through the winding of relay 102, right inner armature and front contact of relay 117 to ground at key 160.

The attendant now dials the number of the desired station, relay 111 following the impulses in the well known manner At each opening of the line circuit, relay 111 releases and connects ground through its leftarmature and back contact, left armature and contact of relay 12 1, winding of slow.-to-release relay 126, conductor 152 to battery through the winding of stepping magnet 310. Relay 126 operates and the magnet 310 is seized. Assuming the number of the called line to be 36, then magnet 310 will receive three current impulses thus causing the brushes of register switch 300 to be advanced to the No. 3 set of terminals. At the end of the tens dialing period, relay 126 releases and completes a circuit from battery through the winding of register relay 302, brush 320 and cooperating contact, conductor 351, right norn'ial contacts of relay 126, to ground at the left outer 1li1121 ture and contact: of relay 117. This same ground is extended through the left arma ture and locking contact. of relay 302 to cause the operation of relay 130 which ale looks. The operation of relay 302 connects the sleeve conductors of the group of lines having a tens digit of with the set of units contacts in. switch 300.

When relay 126 releases at the end of the first dialing period a circuit is completed for advancing the brushes o't' switch 300 to the next resting position upon the No. set of terminals. This circuit may be traced from ground at the right normal contact of relay 12 1-, conductor 153, brush 330 and cooperating contact, armature and contact of mag net 310, conductor 350, left inner armature and front contact of relay 130, conductor 152 to battery through the winding of step ping magnet 310. When the No. 5 set cf terminals is reached the above traced circuit is broken and the brushes of switch 300 come to rest.

The attendant upon transmitting the units set of impulses causes relay 126 to become energized and the stepping magnet 310 to alternately operate and release until the proper set of units terminals is reached. At the completion of the units dialing relay 126 and stepping magnet 310 release. A test is now made of the called line in the following manner. Relay 128 which operated when relay 130 was energized now completes a circuit from battery, through the left winding of relay 131, left armature and front contact of relay 128, left normal contact of relay 126, conductor a, brush and cooperating contact, right hand contact No. (3 of relay 302 to the sleeve conductor of the called line. Should the called line be busy a ground potential will be found on the sleeve conductor and relay 131 will operate in the last traced circuit thus providing at its right outer armature and contact a holding circuit for relay 128. A distinctive tone will now be transmitted from the tonesource 155, left armature and contact of relay 131, ringside of the trunk, thence through contacts of relay 123 and key 170, through the attendants set. The attendant thereupon releases key 160 thus replacing the talking set 180 in communication with the central office by the release of relay 123 and she may now proceed to notify'the central office operator of the busy condition on the called station.

Should however the called station beidle,

ill)

ltll) when relay 126 releases the second time, there will he no ground potential on the sleeve conductor of the called line, thus permitting 131 to remain normal and the subsequent release of relay 12S.

lVhcn relay 125 operated subsequent to the operation of keys 100 and 170 a circuit was completed from battery, through the winding of stepping magnet 100, armature and contact thereof, left armature and contact of relay 105, left armature and back eon tact of relay 10 1 to ground at the armature and contact of relay 125, lilagnet 106 continues to advance the brushes of switch 100 by means of this self-interruptiug circuit. ll hen however, register switch 300 has been set, ground is connected through the winding of low resistance identifying relay 10 1, left armature and back contact of relay 128, left normal contacts of relay 126, conductor 15%, brush 353 and No. 6 units terminal, right hand contact No. 6 of relay 302, sleeve conductor of the called line to battery through the winding of cutotl' relay 202 which oper ates, but relay 104 does not. Battery is now connected through the winding of relay 202, right armature and contact thereof, conductor 262, to a contact in the terminal bank with which brush 110 cooperates. ll hen brush 110 during its rotation reaches this particular terminal, battery is connected through resistance 10?, left armature and back contact of relay 108, brush 110 and thence in parallel with battery through the winding of relay 202, to ground through the identifying relay 10% as above traced. Relay 1041 receives sulllcient current in this circuit to energize thus causing the brushes of switch 100 to come to rest upon the terminals of the called line. Relay 105 now operates from battery through its winding, right normal contacts of relay 108, left armature and front contact of relay 10 1 to ground at the armature of relay 125. Ringing current is new supplied to the called line from the ringing source 162, winding of relay 163, right inner armature and front contact of relay 129, ring side of the trunk, thence to the ring side of the called line through the called subscribers apparatus back over the tip side of the called line and thence over the tip side of the trunk to ground at the right outer armature and con tact of relay 129.

The attendant may new release keys 100 and 170. The release of key 170 disconnects the talking set from the trunk causing the successive release of relays 111, 124,117, 125, 130, 302 and 104:. A circuit is now closed from battery through the winding of relay 108, left armature and contact of relay 112, right normal contact of relay 117, to ground at key 160. The operation of relay 108 connects ground through its left armature and front contact, brush 110 and cooperat- Register switch 300 new 'estorcd to its normal position. This circuit ma he tr ccd from battery through the windi of stepping magnet 31, conductor inding of relay 126, left inner armature and back contact of relay 130, conducttn armature and contact of magnet 310, bri 330 and cooperating contacts, conductor o left outer armature and back contact of re 130, to ground at the right normal contacts of relay 124. Guard lamp 101 is now lighted from ground at key 100, right :nhrziature anal contact of relay 112. right outer contact of key 170, right inner armature and back con tact of relay 122, right outer armature and contact of relay 121, to battery through the lamp 101-. Guard lamp 10 lremains lighted until the -allcd subscribe answers. 7

ll hen allcd subscriber rcmorcs the receiver from the switchhook, relay 10:1 operates thus cans ng the release of relay 129 and the disconnection of ringing current from the called line, Relay 111 now operates through the normal contacts of relay 113, whereupon a circuit is closed from ground at the left armature and front contact of relay 111, right inner contacts of key 100 to battery tl'irough the winding of relay 113. Relay 118 immediately locks in a circuit extending through the right arnun ture and contact of relay 112 to the above traced ground, thus causing the release of relay 111. The called line is now connected directly with the central ollice trunl: caus ng supervisory relay 114- to operate. Relay causes the successive energization of rca 115 and 110. clay 110 in operating ca the release of relay 20. However. relay 112 maintained energized by round at the left arn'iature and contact of relay 110. The release of relay 111 connects ground through its right armature and back coir tact, right outer arn'iature and front contact of relay 113, left outer armature and con tact of relay 121 to battery from the wind ing of relay 122 which locks in a circuit traceable from battery through its winding, armature and locking contact, right outer contacts of key 170, right outer armature and contact of relay 112 to ground at key 100. The guard lamp is extinguished as a result of the operation of relay 122.

When the called subscriber replaces his receiver, relay 11-l releases. in turn releasing relays 115 and 116. The release of remainder ot the connection is under the control oi? the central oiiice since relay 120 reoperates when relay 116 releases. This provides a holding circuit for relay 112. When disconnection takes place at the central otfice, relay 120 releases causing the release of the remainder of the connection.

The local subscriber may recall the attendant by depressing the switchhoo-k momentarily thus causing relays 11 1, 115 and 116 to reoperate. A circuit is now completed from battery through line lamp 1&0, rightouter armature and contact oi relay 122, left inner armature and back contact of relay 121, left armature and front contact of relay 122 to ground at the armature of relay 116. Lamp 140 is illuminated in this circuit and serves as a recall signal to the attendant, who answers by operating keys 160 and 170.

The attendant may signal tne central otfice operator by operating and releasing key 156, causing the release oi? supervisory relay in the central oilice. The trunk super visory relay 11. 1 however, remains energized in series with attendants set 180 and resistance 157.

By means of key 161. the attendant may originate a call to the central ofiice and latex. extend this same call to any station as previously described. i 1

hat is claimed is: y

1. In a telephone system, calling lines, central oiiice trunks, a plurality of automatic switches each individual to a trunk and common to a number of calling lines, a cut-oil relay for each of said calling lines, a test relay for each of said trunks, means for energizing a cut-oit relay prior to the operation of one of said automatic switches, a circuit for the corresponding test relay, means under control of said cut-oft relay for partially completing said circuit, and means rendered etl'cctive when said one of said automatic switches locates a calling line for completing the circuit of said lest relay to thereby prevent further operation o't'said automatic switch.

2. In a telephone system, a calling line,

a link circuit a central oiiice trunk, a cut-- off relay for said calling'line, a plurality of sets of line finder switches, one set of said finder switches adapted to connect the call ing line with the link circuit, the other set of said find-er switches adapted to connect the calling line with the central oliice trunk, means responsive to the initiation of a call to cause the first of said sets of line finders to seize and connect: with the calling line, a test relay for said central oiiic-e trunk, a test circuit extending through the winding of said cut-oii relay, means rendered efi'ective when a line finder ot' the first set has seized the calling line and responsive to the transmission of particular series oi impulses to cause a line finder of the second set to seize the calling line, means rendered efl'ectvie when the calling line has been so seized for completing said test circuit through said cut-oil relay and said test relay to prevent further operation of the'line finder of the second set, and means rendered effective upon the operation of said test relay to complete the connection or the calling line with the central oiiice trunk and to release the said first line finder.

3. In a telephone system, a calling line, a cut-oil relay, a plurality of outgoing trunks, registering mechanism, an automatic switch for finding the calling line and associating the same with said register mechanism, means responsive to the transmission of a special code for causing the association of said calling line with an idle outgoing trunk, identifying means associated with said outgoing trunk, a second automatic switch, means efilective upon the association of an idle outgoing trunk for causing said second automatic switch to operate to find the calling line, means under the control of said cut-0H relay for markingthe calling line, and means efi ective upon the finding of the calling line by the second automatic switch for causing, said cut-off relay'and said identifying means to cooperate in bringing said second automatic switch to rest.

4. In a telephone system, calle-dlines,a plurality of trunks, an operators position, an impulse transmitting device at said position, registering means comprising relay and switch recording mechanism, means for setting said registering means in accordance with the impulses transmitted, means under control of said registering means for mark ing one of said called lines, an automatic switch, means eiiective upon the transmission of impulses for causing said automatic switch to hunt for the called line, a relay individual to the called line, a plurality of identifying means each individual to one 0i said trunks, and means effective upon the finding of the called line for causing said relay and one of said identifying means to cooperate in bringing said automatic switch to rest.

5. In a telephone system, telephone lines, a plurality of link circuits for interconnect ing said lines, a switch common to anumber of said lines and responsive to the initiation of a call on one of aid lines for connecting said line to an idle one of said link circuits, a progressively movable switch operable in accordance with the busy or idle condition of another of said lines for connecting said one of said link circuits to the second mentioned'line, and a register mechanism for recording the designation of said second mentioned line and for allowing a test to be made thereof prior to the op-erz tion of said progressively mo 'able switch.

6. In a telephone system, a plurality of calling lines, a plurality of called lines, a plurality of link circuits, for extending said calling lines, a progressively movable switch common to a number of called lines for connecting an extended calling line to a particular one of said call-ed lines, testing means, a circuit for said means, and a recording mechanism operable in accordance with a portion of the designation of a called line for completing the circuit of said testing means prior to the operation of said progressively movable switch.

7. In a telephone system, a calling line, a called line, a plurality of link circuits, means eflective upon the initiation of a call for extending said calling line to an .idle one of said link circuits, a progressively movable switch individual to said one of said link circuits for connecting said calling line to said called line, register meanscomprising switch and relay recording mechanisms, testing means, and means rendered effective upon the operation of said register means for connecting said testing means to the test conductor of the called linepriorto the operation of said progressively movable switch.

8. In a telephone system, calling and called lines, a plurality of automaticswitches each common to a number of calling lines, a plurality of link circuits each individual to an automatic switch, a test conductor for each calling and called line, a group of relays operable in accordance with a portion-of the called line numerical designation, contacts in said group of relays in which the test .conductors of called lines terminate, and a progressively movable switch common to a number of called lines and controlled by certain of said relays and the condition of the associated test conductor-s.

9. In a telephone system, a calling line, a called line, a connecting circuit for extending said calling line to said called line, a plurality of registers each individual to a connectingcircuit, a plurality of connector switches, means controlled by one of said registers for testing saidcalled .line and causing the operation of one of said connector switches, and means independent of said connector switch and controlled by said register for maintaining said called line nonselectable by other connector switches.

10. In a telephone system, a calling line, a plurality of called lines arranged in groups, link circuits for extending said calling line to any one of said called lines, a register mechanism, connector switches, means controlled by said register mechanism and one of said connector switches for marking line groups and individual lines, and means controlled bysaid register mechanism and independently of said connector switch for maintaining an individual called line non-selectable by other connector switches.

11. In actelephone system, a plurality of calling lines, a called line, a connecting circuit for extending one o1 said calling lines to said called line, a register for said connecting circuit and common to said plurality of calling lines, means controlled by said register for determining the busy or idle condition of said called line, a connector switch in which said called line appears, means under control of said register for operating said connector switch to seize the called line, and means controlled by the register for maintaining the called line busy independent of the setting of said connector switch.

12. In a telephone system, calling lines, called lines arranged ingroups, link circuits for interconnecting said calling and called lines, switch and relay recording mechanisms, a connector switch, means controlled by said relay recording mechanism for marking the group in which a particular called line is located, means under joint control of said relay and switch recording mechanisms for causing said connector switch to hunt for the particular called line group, means controlled by said switch recording mechanism-and subsequent to the finding of said-called line group for marking other called lines in other groups, and means effective when said called line group has been so found for causing said connector switch to hunt for and seize the particular marked Inc in the selected group.

13. In a telephone system, calling lines. called lines arranged in groups, link circuits for interconnecting said calling and called lines, register means comprising relay and switch recording mechanisms, a connector switch, means controlled by said relay recording mechanism for markingthe group in which a particular called line is located, means under control of said registering means for causing said connector switch to selectsaid particular called line .group, means effective when said group has been so selected for marking the remainder of said called line groups and a different called line in each group, and automatic means for continuing the operation of said connector to seize the individually marked line in the selector group and to prevent the selection of an individually marl-:ed line in another group.

In witness whereof, I hereunto subscribe my name this 4th day of March A. 1)., 1924-.

IVALTER P. ALBERT.