US1501668A - Telephone system - Google Patents

Description

July 15, 1924.

L. KELLER TELEPHONE SYSTEM 2 Sheets-Sheet l Filed July 20, 1920 I/O m JulyV 15, 1924. 1,501,668

A L. KELLER TELEPHONE SYSTEM July 2o, 1920 2 Sheets-Sheet 2 Coll OOOOOO oooo oooob Patented July 15, 1924.

UNITED STATES PATENT LEO KELLER, or New YORK., N. Y., assitance To einem@ Consent', in#

CQRPQRMED, or NEW YQRK, "N: Y., A COnPORATiIQN SQP New YQRIK- TELEPHONE SYSTEM.

Application led July 20,

to a central oiiice, the invention comtemplates the use ot line inders and connectors, the latter switches being directly responsive to impulses for connections to subscribers within the exchange and also capable of trunk hunting when establishing out-- going calls to central office or to the private branch exchange attendant. It has been customary. in systems embodying these general characteristics, when establishing incoming calls, to signal the private brauch exchange attendant over a central office trunk. The attendant then dials for the wanted subscriber over connections independent ot said trunk and,v upon the response ot' the subscriber, his line is connected, either automatically or manually, to the incoming trunk.

An object of the present inventio-n is to employ portions or extensions of incoming trunks and the same connecting circuits used in establishing calls wit-hin the private branch exchange incompleting central ofice connections to a subscriber within said exchange.

In accordance with this object the private branch exchange attendant is preferably provided with a key or .other switch associated with an incoming trunk and which, when operated, will cause a line finder to seek and engage terminals to which an extension of said trunk connected. The attendant may then operate connector switch to establish connection with a .subscriber by the transmission of impulses over said extension and through the line linder.

A preferred embodiment of the invention is illustrated in the accompanying drawings.` wherein Figs. 1 and 2 with Fig. 1 at the lett of Fig. show diagrainniatically the circuit arrangement employed,

1920. 'serial No. 397,596.

Fig. 3 is a diagrammatic View of thema-11kmgarrangemnt of thfeline finder andloonnector switches used inconnect-ion'wi-thitlie i invention. y Briefly, the invention contemplates theuse of rotary `single movement switches which are capable of extending incoming calls from central 'otlice through an atten-dants vposition at the private branch eX- change to a subscriber therein, Calls 'loe-` tween subscribe-rs or a subscriber and the attendant within the exchange,` and 0115134' going calls from subscribers or the attendant to cent-ral otce.

The inventive idea involved in the in? vention may be generally understood lby reference to Fig. 3 ofthe drawings. There is here yshown a line iin-dei" A, the bank of which includes terminals to which a number of subscribers lines and central oce trunks may be extended. The terminals'o the lines and trunks may be arranged in any desired manner. Connected :to the brushes 0f Athe line finder is a connector B. Terminating in the bank ot' the connector and utilizing certain of the terminals there-- of are groups of central oflice trunks, subscribers lines and attendants trunks. Gertain other of the` terminals of the connector bank are allotted for group Selection and may be interspersed between terminals of i the several groups.

On an incoming call from the central of.- iice, the call is routed through the attendant who, in a manner which will appear in the course ot the description, causes the line nder A to operate and engage the lbrush thereof with the terminal individual to an extension of the central ofiice trunk taken for use. The attendant then dials't-henumber of the wanted subscriber. It said subscriber is in the group of lines having the digits 4l to 44. the impulses corresponding to the tens digit will operate the connector switch to engage the b-rushthereof with the fourth terminal. The next or units impulses then causes the connector to select* the desired line in the selected group. It the desired line is in the group' marked lines 94h98, the nine impulses of the tens digit steps the connector to the ninth terminal and the second series of impulses carries the switch over the tenth terminal and terminals of the attendants trunks to the desired line. Should the wanted subscriber be in thelast lili group, it is :necessary to transmit three series of impulses, the lirst tvvo of nine each stepping the connector to the terminal marked 99 which is the eighteenth terminal in the bank and the last series engaging the brush of the connector with the terminal of the desired line. Subscribers Within the exchange may establish connections inthe same manner after the line finder has engaged the terminals of the callingl line.

A subscriber desiring a central oliice connection transmits one impulse to cause the switchto take one step and then automatically hunt for an idle trunk in the group assigned for central oce trafc. Should a subscriber Wish a connection to the attendant, ten impulses are sent to engage the tenth terminal which is allotted for attendants trunk selection. The switch again automatically hunts for an idle path leading to the attendants position over the group o terminals AT.

lt is believed that the invention will now be fully understood from the following detailed description of the establishnfient of t-he various connections.

Incoming @all from central oyce.

Then the central office operator` inserts plug of a cord circuit into jack 100, a Well known circuit is closed to light the central office supervisory lamp associated with the cord taken for u se vand to energize cut-off relay 101 in the usual manner, thus disconnecting the line relay 102 from the trunk. A suitable cord circuit is shown in Patent No. 1,125,965 of January 26, 1915, to E. H. Clark. A circuit is also closed trom bat-- tery in thecord circuit through the usual supervisory relay therein, the ring contacts of the plug and jack 100, the Winding of supervisory relay 108, the right-hand normal contact of the relay 104, the Winding of relay 105, the tip contacts of jack and the plug engaged therein, to ground. lay 105 is energized but is of such high4 resistance that the supervisory relay in the central oilice cord circuit is prevented from operating. The energization of relay 105 closes a circuit extending from grounded 'battery through the Winding of sloy.v to release relay 106 and the contact of relay 105 to ground. Relay 106 energizes and places a guarding potential on the sleeve conductor of the trunk in the connector multiple. to prevent seizure ot said trunk when a call is initiated to the central oliice by a subscriber Within the private branch exchange. The energization oi' relay 106 also estab lishes an obvious circuit for relay 107 which, upon energizing, lights the busy lamp 10S. Then the central otlice operator actuates her ringing key, supervisory relay 103 operates from the ring side of the trunk through the Winding oi? said relay, the condenser 109 and the left-hand normal contact oi relay 110 to the tip side ot' the trunk. Relay 103 energizes and remains in this condition durA ing the actuation oi the ringing key and upon operating establishes an obvious circuit or relay 10/1vvhich, upon energizing, opens at its right-hand normal contact the previously described circuit for relay 105 Which then releases. The release of this relay opens the energizing circuit initially described for relay 106 but, this relay being slovv to release, the energization of relays 103 and 104 establish other holding circuits for the same. The energization ot relay 1041- also includes the non-inductive resistance :i:`

190 associated with relay 103v in parallel With the inductive Winding thereof. At its outer left hand alternate contact relay 104 also establishes a circuit for relay 111 ein tending from grounded battery through the Winding oif said relay the outer alternate contact of relay 104 and the normal right hand contact of slow to release relay 112 to ground. Relay 111 energizes and locks through it-s right-hand contact to ground at the normal contact of relay 112 and at its left-hand contact establishes the circuit for lighting the line lamp 113 Which indicates to the attendant at the private branch exchange that a call on the particular trunk is awaiting attention. The attendant, With her receiver removed from its switchhook, then actuates the listening key 1141- whereupon a circuit 'is established from grounded battery through the left-hand Winding of line relay 115, the middle normal contact of relay 110, the middle normal Contact of the central office cut-ott' key 116, the right-hand Contact of the listening key 11i. the attendants substation set 117, the left-hand contact of the listening key, the upper normal contact of the central oliice cut-oft' key, the right-hand normal contact of relay 110 and the right-hand Winding of relay 115 to ground. Relay 115 energizes and establishes a circuit for relay 112 extending from grounded battery through the Winding of said relay and the right-hand contact of relay 115 to ground. Relay 112 energizes and opens the locking circuit for relay 111 which thereupon releases to extinguish the line lamp 113.` The energization of relay 112 also establishes a circuit for relay 110 extending from grounded battery through the Winding of said relay. the lett-hand alten nate contact of relay- 112 and the inner right-hand alternate contact of relay 106 to ground. this relay being still energized due to the re-energization of relay 105 at the termination of the operation of the ringing key Which energized relays l103 and 104.` Relay 110 energizes in the circuit described theretor and at its right hand normal contacts opens the circuit for line relay 115 Which thereupon releases, but the energizacirc-uit.

tion of the relay 110 provides a holding circuit for relay 112 to ground through the left hand alternate Contact of relay 110. The energization of relay 110 also connects the trunk through to the attendants telephone and at its left hand normal contact opens the bridge across the trunk which includes the condenser 109. The trunlr having been extended through to the attendants position, the cord circuit supervisory relay at the central oi'lice and the superrisory relay 103 thereupon energize in the usual inanner, the operation of the former relay extinguishing the supervisory lamp in the oord Relay 103, in operating again causes the energization of relay 104 which disconnects relay 105 from the line and provides a holding circuit for relay 106. Relay 104 again includes the non-inductive resistance 190 in the line circuit for talking purposes. A. connection is now established 'from the calling subscriber through the cent-ral, office to the attendant at the private branch exchange who may nouT communicate with said subscriber to obtain the details of the connection desired.

Having ascertained the number of the wanted subscribensthe attendant operates the central oilice cutoff key 116 which at its upper alternate contact establishes an obvious circuit for relay 118, and this relay in closing its left hand contacts connects the holding bridge 119 the trunk to hold the connection While the attendant proceeds to call the wanted subscriber. rlhe operation of the key 116 opens the talking circuit established from the central oilice to the attendants telephone and in closing the contacts 120 and 121 connects the local battery to the attendants line through the windings ot coil 122. The opening ot the line circuit causes the deenergization ofthe supervisory relay 103 which in turn opens the circuit for relay 104 and the previously described holding circuit tor relay 106, but bet'ore this latter' relay can release its armatures relay 118 is energized as previously described to provide another holding ground at its right hand contact tor said relay 106.

The opening of the lower normal Contact of key 116 removes ground trom the conL ductor 123 which extends through thelower normal contact of the private branch ei;- change cutoff key 121A to the test terminal ot the row in the line Afinder bank with which brush 200 is associated. The closure ot the lower left hand alternate contact of lrey 116 grounds the trunk terminal in the bank ot' the line finder and the closure of the lower right hand alternate contact of said ltey grounds the starter wire 125 extending through the normal contact of the cutotl relay 126.

As soon as the starter wire is grounded a circuit is established for the` line finder test relay 201 extending from grounded battery through the winding of said relay, brush 202 oi' the line iinder in normal position, the terminal associated therewith, the lett hand normal contact ot relay 203, starter wire 125, the normal contact of relay 126 land the lower right hand rontact ot lrey 116 to ground. Relay 201 energizes in this circuit thereby closing a circuit tor slow to release relay 2011- extending from grounded batte through-the windingl of said relay, brush 205 oit the connector. lett hand normal contact of slow to release relay 206, ht hand normal contact of relay 201. the brush 208 or' the connector and the right hand normal contaet ol' slow-to-release relay 209 to ground. rllhe energization of relay 20ain this circuit causes the energization of relay 210 troni grounded battery through winding of said relay and the mi naiui a' ornate conc-act ot relay 204 to 1 i i x iground. lhe closure or the inner right hand alternate contact ot relay 210 establishes a sellf-interrupting circuit for the motor magnet 211 ot' the line finder switch extending .trom grounded battery through the winding and Contact of said magnet ot' the right hand alternate contact of relay 201, the brush 200 in its normal position, the inner right hand alternate contact ot `relay210 and the left hand alternate contact of relay 2011 to ground. The magnet 211 operates to cause the brushes of the line Ender switch to talte one step from their nor-mal positions. The test terminals associated with the brush 200 ot the line finder switch are normally grounded either by the lower normal contact ot' lrey 116 or the norinal contact et' line relay 212 associated with cach subscriber line in the private branch ein' bange. rllheretore, as long as the brushes ot' the line finder switch engages the terininals associated with idle lines a locking circuit for test relay 201 will be established extendingytrom grounded battery through the winding ot said relay, brush 202, the segment 213 associated therewith, the right li nd alternate contact ot relay 201 and brush 200 to ground upon the test terminal.

permanently break the stepping circuit. lll'L i hand alternate contact ot relay Relay 201 will therefore remain operated` iith the brushes oi' the switch in engagenient with the' terminals associated with the portion of the trunk extending Yfrom the attendants posit-ion,l a circuit is established@- 'tor line relay 214 extending from grounded battery, through the lett hand Winding ot said relay, the outer lett hand normal contact ot relay 20T, the middle normal contact of relay 201, the brush 215, the middle normal contact ot key 12st the right hand contact ot' listening key 114C,r the attendants .substation apparatus, the left hand contact ot key 114-, the upper normal contact of key 12st, brush 216, the lett hand normal contact ot relay 201, the inner lett hand normal contact of relay 207 and the right hand Winding of relay 21e to ground. Relay 214.- energizes and this occurs before relay 204 can release following the opening of its original energizi 0j circuit through the lett hand alternate Contact ot' the test relay 201. Relay 201- iyill therefore be held energized over another circuit extending from grounded battery through the Winding of said relayf the lett hand alternate Contact of relay 214, the inner lett hand normal contact oi' relay 20? and the right hand alter nate Contact of relay 2li to ground. Continued energization ogt relay 204 maintains the relay 210 in its operated condition and upon engagement ot the brushes of the line finder with the terminals otW the trunk taken tor use, a locking circuit is established for relay 210 extending from grounded battery through the Winding and inner right hand alternate contact otl said relay, brush 217-, conductor 127 and the left hand alternate contact ot relay 106 to ground. The energization of relay 214 also establishes a circuit for relay 203 extending trom grounded battery through the Winding of said relay and the right hand alternate contact of relay 2.11 to ground. Relay 203 energizes and locks through its middle alternate contact, the inner right hand alternate contact of relay 210 and brush 217 to ground at the left hand alternate contact of relay 106. By closing its left hand alternate Contact relay 203 transfers the starter Wire to the next line finder. The closure of the right hand alternate contact ot relay 203 establishes a circuit extending from ground, through the right hand alternate contact ot' said relay, the innermost lett normal con tact ot relay 201, the brush 21S and the Winding ot the cuttf relay 126 to ground. Energization of the latter relay in the circuit just described disconnects ground from the starter wire 125 to pre rent a second line finder from being started and also at its al ternate Contact again grounds the test terminal in the line Jfinder bank associated With brush 200. The grounding of this terminal however does not allect the motor magnet 211 ot the line finder since the test relay 201 has already released.

The attendant may now dial Jfor the desired connection. Let it be assumed that the call is to be extended to substation 219 and that the number ot' this substation is 94. Vlfhe attendant manipulates her impulse sending device to transmit nine impulses and upon each interruption ol the line cir cuit, extending through the windings oit relay 214, this relay releases to establish a stepping circuit tor the motor magnet 220 extending troni grounded battery through the Winding ot this magnet, the Winding ot relay 209, the right hand normal contact ot' test relay 221, the right hand normal contact ot relay 222, the right hand alternate contact ot' relay 20s, which nniintaii'is its armature attracted during theitransinission ot the impulses, the normal contact ot relay 214;, the inner right hand normal contact of relay 20?, the inner lett hand alternate con-- tact of relay 203 and the lett hand alternate contact ot relay 204 to ground. Relay 209 also energizes in this circuit, maintains its armatures attracted during the transmission ot' impulses and removes ground trom brush 208. The energization otI relay 209 also establishes a circuit extending from ground through the alternate contact ot' said. relay, the normal Contact of relay 223 and the winding ot' relay 224 to grounded battery.

The energization of relay 224 opens the sleeve and test brush circuits extending through brushes and 226, respectively.

,At the termination ot the nine impulses corresponding to the tirst digit of the called number, relay 209, after an interval releases and the test brush 226 will be engaged with terminal 227 on the connector multiple bank with the other brushes on the corresponding terminals in the same vertical row. A circuit will then be established for relay 22S extending 'trom grounded battery, through the Winding of said relay, brush 20S and its associated terminal and the right hand normal contact of relay 209 to ground. Relay 228 energizes and locks up in a circuit extending from grounded battery through the Winding and right Ahand alternate contact of said relay, the inner lett hand alternate contact of relay 210 and the left hand alternate contact of relay 204 to ground. Relay 2211 is held energized over the brush 286 to ground at the lett hand alternate con tact of relay 210. The attendant now sends tour impulses corresponding to the units digit of the called number and the stepping circuit is again closed in the same manner as previously described to operate motor magnet 220 and energizes relay 209. At the termination of this series oit impulses and with the brushes ot the switch engaged with the terminals ot the Wanted line, relay 209 again releases. It the called substation 219 is busy due to another call from the central oliice, a ground Will be placed upon the multiple sleeve terminal of the called line through the busy connector switch, the brushes of Which are in engagement With the terminals ot said line. rllhis ground extends Jtrom 'the inner right hand alternate contact of relay 106 over the conductor 12T, brush 21T. right hand normal contact or" relay 229 ot the busy connector switch. the lett hand normal contact otrelay 224 o't` said switch, the next to outer right hand alternate contact ot relay 210 to the brush which is in engagement with the sleeve terminal of the called line. lt' substation 210 is busy on a local call, then the slow-to-release relay 204 of the busy connector switch remains en-` ergized throughout the call due to energiza tion ot line relay 21+.L and the ground po' tential on the sleeve terminal of the called line is extended trom the lett hand alternate contact ot' relay 204` through the inner right hand alternate Contact ot relay 210, the right hand normal Contact. o'l" relay 229, the lett hand normal contact ot relay 224, the outer right hand alternate contact ol relay 210 to brush Thus, should substation 219 be busy when lthe brushes oll the switch engage the terminals thereof, a circuit will be established t'or test relay 221 by the malte-be- 'l'ore-breah Contact of relay 209 betere this relay is tully released to open the circuit for relay 224. This circuit t'or relay 221 eX- tends 'trom ground at the sleeve terminal of the called line through brush 225, the next to the outer right hand alternate contact of relay 210, the alternate contact ot relay 224, the middle alternate contact of relay 223, the lett hand normal contact and Winding ol' relay 221. left hand normal contact of relay 209, the normal contact ot relay 223 and Winding of relay to battery and ground, whereby rela' 224 which has up to this time been held up by ground at the letft-hand alternate contact ot' relay 209 is non' held up in series with the Winding o'tl 221 by the ground on the test terminal ot the called line. Re lay locks up through its lett hand alternate contact, the innermost right hand alternate contact otl relay 210 and the lett hand alternate Contact of relay 204 to ground. Relay 224 is held energized in this circuit. @pei-ation ot relay 221 extends ground through the right hand alternate contact ot said relay. the secondary Winding ot the busy tone transformer 230 to one side ot the trunl; then in use, thence to the attendants suhstzfition and to grounded battery through the let't hand Winding` oit line relay 214. The attendant upon hearing this busy tone, proceeds to release the connection in a manner which u'ill later appear. The energization oi relay also opens at its right hand normal contact the stepping circuit for motor magnet 210 to prey-ent further operation Lhereo't should additional impulses he transi'nitted.

It' the called line is idle no ground Will be found upon the sleeve terminal thereof and relay 221 will `fail to operate. Relay 224 Will therefore release as soon as"v the alternate contact of relay 209 is opened. The release of relay 224 establishes a circuit eX- tending from ground through the left hand alternate Contact ot' relay ,204, the ,inner right hand alternate contact of relay 210, the right hand normal contact of relay 229, the lett hand normal contact ot' relay 224, the next to outer right hand alternate contact of relay 210, brush 225 and the Winding of the cutoit relay of the cal-led line similar to cutotl relay 231 shown at the 4left of 2 to grounded battery. The cutofll relay ot' the called line thereupon operates and prevents energization of the line relay individual to said called line should the -subscriber remove his receiver from the switch hook to initiate another call. Relay 222 is now energized over a circuit extending' from grounded battery through the winding of said relay, the right hand normal-contact of relay 206, the normal contact of relay 232, the left hand alternate contact of relay 228, the right hand norma-l contact of relay 224, the next to the innermost right hand alternate contact of relay 210, and test brush 226 to ground. Relay 222 energizes and connects ringing current to the called line over a circuit extending from grounded battery through the secondary Winding of the ringing transformer 233, left hand Winding of relay 206, the left hand alternate contact of relay 222, brush 234, the ringing apparatus at the called substation, brush 205 and the inner left hand alternate contact of relay 222 to ground. Relay 206 is not energized in this circuit until the called subscriber removes his receiver from his switch hook whereupon sufficient current flows through the let't hand Winding of relay 206 to cause it to attract its armatures. In operating, relay 206 opens the energizing circuit for relay 222 Which thereupon disconnects the ringing current from the called line. Relay 206 locks -up over a circuit extending through its right hand Winding and inner right hand alternate contact and from thence over the previously described energizing circuit tor relay 222 to ground at the test brush The energization of relay 206 also establishes a circuit extending from ground through the outer right hand alternate contact ot relay 206 and Winding ot' relay 223 to grounded battery. Relay 223 energizes and establishes a circuitfor relay 232 extending from grounded battery through the left hand Winding of relay 232, the alternate contact of relay 223, brush 235 of the line finder and the lowermost left hand alternate Contact of central ollice cutoff key 116 to' ground. `Relay 232 energizes and locks up over a circuit extending fromA grounded battery through the right hand Winding and right hand alternatecontact of said relay, the left hand lalternate contact of relay 228,

the right hand normal contact of relay 224, next to the innermost right hand alternate contact otV relay 210 and test brush 226 to ground. The energization ot relay 282 opens ythe locking circuit for relay 206 which exn tends through the normal contact or said relay releases.

ternate contact ot relay 232 to ground. Re-

lay 20T, upon energizing, connects the trunk through from the attendants position to the called subst-ation, and causes the release ot line relay 2111v and relay 204:.

The operation of the connector switch would be the same as linst described it the wanted line had been in the group ot lines having` 4f. as the tirst digit instead ot Q. in establishing calls wherein the wanted line has three digits, the operation will again be the same, the first digit 9 carrying the switch to the row of terminals including' the terminal 227, the section digit 9 carrying the switch to the' row of terminals similar to the rtirst mentioned row but not shown on the connector bank in Fig'. 2, while the third di ,cit operates the switch to engage terminals of `the wanted line.

The called subscriber at substation 210 having answered7 the attendant then restores listening key 114 and central oliice cutoff key 116 to their normal positions and the latter key, when restored. extends the trunk Jfrom the central oitice through to the called subscribers substation. whereupon the calling and called subscribers may converse. The supervisory relay 103 is energized in the conversational circuit and maintains energized relays 104. 1.06. 110, 112 and 107.

At the termination ot the conversation, the replacin .eV ot the receiver upon its switch hook at the called substation causes the release ot the supervisory relay 10?)7 which. upon deeuergizing', opens the circuit Ytor relay 104. whereupon relay 105 becou'ies ener- ,Q'ized and holds relays 100. 110. 112 and 10T energized. Then the called subscriber hangs up and thereby releases relay 10?). thc supervisory lamp at the central ottice is airain lighted to indicate to the operator thereat that the call has been terminated and she then removes thc plug trom jack 100. This releases relay 105 which opens the holding?` circuit tor relay 106 and the latter relay` upon.4 deenergizinc'. removes the holding` ;round from conductor 127v to cause the release of the switches employed in establishine' the connection.

rllhc removal ot `round trom the letthand alternate contact ot relay 106 opens the previously described locking circuit for relays 2055 and 210 which thereupon release. Restoration ot relay 20?) opens thc holding circuit for relay 120 through brush 21S and relay 120 then releases. Upon the release oi relay 210, a stepping circuit `tor the line iinder is closed extending' trom grounded battery through the winding and contact of motor magnet 211, brush 23T and the lett hand normal contact ot relay 210. to ground. rilhis circuit, being` seit-interrupting. causes. the motor magnet to step the liuc finder switch back to its normal position. rllhe release ot relay 210 also opens the locking' circuit tor relay 228 which extended through the innermost right hand alternate contact ot' relay 210, and relay 228 in releasing. opens the locking' circuit tor relay which extended through the lett hand alternate contact ot relay 228. Ground being' removed from the left hand alternate contact ot relay the holding circuit tor relay 20T is opened and this relay releases with thc brushes ot the connector still in engagement with the terminals ot the called line. A circuit is now established 'tor relay 229 extending` trom grounded battery, through thc winding ot this relay.y a rigght hand normal contact ot relay 210 and brush 226 to Aground. Relay 229 energizes and in so doing` establishes a self-interrupting circuit tor the motor magnety 220 of the connector switch. said circuit extending from Agrounded battery through the wi udine o't said mannen the winding` ot relay 200.l the contact ot magnet 220. a right hand alternate contact ot relay 229 and the right hand normal contact ot relay 203 to ground. Magnet 220 theretore operates to step the brushes o't the co nector switch towards their normal position and as lona` as the brush 226 is passinn' over test terminals connected to ground. this seit-interruptincA circuit will be maintained. Then brush 226 engages the last terminal in thc connector bank. the yground 'For the continued n'iaintenance tor relay 229 is Found at the normal contact with relay 204 which was previously released by the energization ot relay 207 at the time that the connection was established. The motor magnet 220 is therefore again operated to step the switch Jfrom the last set ot termina-ls to normal whereupon relay 229. no longer findingT around. releases. A more detailed description ot the release of the connector switch will appear later.

Should the attendant desire to answer another call before the one to the subscriber is completed. she may restore key 110 and hold the central o'tlice trunk to prevent the operation ot the disconnect signal thereat by operating key which. at its lett contact, closes a circuit to energize relay 118. Ground is then maintained through the wiudino ot relav 10S to prevent the release thereof. The right hand contact of ltejf 128 prepares a circuit tor lamp 129 through the lett hand normal contact of relay 104. but this relay is energize-d due to the operation ot' relay 103. It, at the termination ot the conversation which results in the release ot' relays 103 and 104, the holding key 123 is still operated. the attendant Will be informed ot' this by the lighting ot lamp 120.

Establishment of a eti/.ZZ between subscribers within the eachmige.

Let it now be assumed that a subscriber within the private branch exchange at substation 233 desires to establish a connection to the subscriber at substation 219. The removal ot' the receiver trom its switch hook at substation 23S establishes an obvious circuit from relay 212 individual to said substation. This relay, in closing its alternate contact, closes a circuit extending from ground through contact ot relay 212, the left hand normal Contact of relay 203, brush 202 and the Windingy of test relay 201 to grounded battery. Relay 201 energizes to establish an energizing circuit for relay 204 through brush of the connector switch to ground at relay 209 as previously described. The connection of ground to the left hand alternate contact ot relay 204 energizes relay 240 over an obvious circuit, whereupon motor magnet 211 will be operated in the sanne manner as described in connection with the establishment of a call from central oilice to step the brushes of the line iinder from their normal position. The idle condition ofthe vlsubscribers lines being denoted by ground upon the terminals over which brush 200 passes. it will be obyious that as long Aas said brush is passing oyer terminals having Iaround connected thereto, the circuit for test relay 201 will be' maintained and motor.

grounded battery. through the lett handnindi'ng ot said relay, the outer Alett hand normal contact 'ot :relay 207., the middle normal Contact ot relay 201, brush 215, the lapparatus at substation ,the brush 216. letth'and normal contact of relay 201, the :inner left hand normal contact of .relay .20T and tlhe right hand Wind-ing of relay 214 to ground. This circuit is closed land relay 214 energizes before relay .-204 r`can Vrelease `so that ythis latter relay `will lnow be main-- ltained energized tfhrough the faltelnate contacts of relay 214. Relay 204 theretoremaintains a holding circuit tor relay 210. The encrgization of relay 214 also establishes the previously described energizing circuit tor relayv 203 which, upon energizing, locks up to ground at the lett hand alternate contact of relay 204. The energization ot relay 203 transt'ers the starter Wire to the next line tinder and establishes a circuit for cutoff relay 231 individual to the calling line, said Circuit extending from grounded battery through the Winding of relay 231. brush 213` the inner left hand normal contact of relay 201 and the right hand alternate contact ot relay 203 to ground. Relay 231 energizes and opens the energizing circuit tor line relay 212 which thereupon releases to again connect ground to the test terminal'individual to the calling line.

The subscriber at the calling substation may now proceed to dial the Wanted number and in response to the impulses the connector switch operates in the same manner as described in connection With a call from central oiice until the point is reached in the operation Where relay 2,23 energizes due to the operation ot relay 206. It Will be recalled tha-t at this time relay 223, in closing its alternate contact, established an energizing circuit for relay 232 which extended through the brush 23.5 to the lower lett hand alternate contact of key 116. It will be noted that in the opera-tion Vof connecting two subscribers, the terminals of subscribers lines engaged by brush 235 of the line ltinder have no Vconnections thereto. Thus, uith `the brush 2.35 resting upon the terminal individual to the .calling line7 no circuit will be established for relay 232 and this relay will remain in its normal condition. It Will also be recalled that,l upon the energization ot rel-ay 2,06.v a locking circuit .was established for this relay extending through its right hand Winding and inner righthand alternate contact, .the normal contact tot relay 232. the lett hand alternate. contact of relay 228. the righiL hand normal contact ot relay ,224, the next to .the innermost right hand .alternate contact ot relay 210 and the brush .to ground. Inasmuch vas relay 232 is .not energized, this locking circuit Jfor relay 206 will ybe maintained throughout the duration ot' .thecall between the subscribers` and relay `207 will tail to operate. The talking circuit will therefore extend through the lett .hand i.iorniial contacts of relay 207 and lthe lett hand alternate icontacts of relay .20.6. Battery for .talking purposes .is sup- Iplied to the called subscribers substation over a .circuit extending from battery through Athe right hand Winding of imped- .ance ycoil the .inner .lett hand alternate contact ot relay 206, the left hand normal Contact ot relay 222, brush 234, called subscriberls substationapparatus, brush 205(7 the lill) cuit ot this relay exception that the release ot relay 210 accomplishes the deenergization ot relay 200 instead ot relay and the release ot the former relay opens the circuit ot the coil 289.

Outgoing @all to cef/115ml oyoe.

A. subscriber within the private branch exchange may initiate calls direct to the central oliice and may employ any one of the trunks extending between the central ottlce and the private branch exchange by operating a connector switch to cause the same to trunk hunt. Should the subscriber at substation 238 desire a central ottice connection, the removal ot the receiver from its switch hook at the substation will cause the line finder to operate in the same manner as previously described, whereupon the subscriber actuates his impulse sending device to transmit one impulse. The brushes ot the con-- nector switch are thereby caused to take one step from their normal positions and engage the second row of terminals in the connector bank. After an interval Jfollowing the termination of the impulse relay 209 releases and establishes a circuit Jfor the trunk test relay 229 extending from ground on the right hand normal contact ot relay 209, brush 208 and the winding of relay 229 to grounded battery. Relay 229 energizes and, in so doing, causes the operation ot relay 2&0 over a circuit traceable from grounded battery through the winding of relay 240, brush 226, the next to the innermost right hand alternate contact of relay 210. the right hand normal contact ot relay 224, the norma-l contact of relay 2287 the lett hand alternate contact of relay 229, brush 208 and the right hand alternate Contact of relay 209 to ground. Relay 240 energizes to remove ground from its normal contact which is connected to all of the test terminals of the central oce trunks. Relay 240 locks over a circuit extending from grounded battery through the winding and left hand alternate contact of said relay, the right hand alternate contact of relay 229 and the right hand alternate contact ot relay 240 to ground. The. energization ot relay 240 also establishesastepping circuit for motor magnet 220 at the connector switch extending from grounded battery through the winding of said magnet, the Winding of relav 209, the contact ot magnet 220, the leilt hand alternate contact of relay 240-and from thence over the energizing circuit of relay 240 to ground at the right hand normal contact of relay 209, The lirst energization ot magnet 220 over this circuit steps the brushes of the switch trom the second row ot terminals in the bank onto the terminals of the first central otlice trunk. The busy condition of trunks to the central otiice is denoted by ground upon the test conductor of the trunks extending from the right hand alternate contact of relay 106 or the similar contact of relay 112. It the first trunk leading to central ottice is busy, ground will therefore be extended through the sleeve brush 225, the middle right hand alternate contact of relay 210, the left hand normal contact ot' relay 224e, the middle alternate contact ot' relay 229 and the winding of thisy relay to grounded battery. Relay 229 will therefore remain energized and maintain a stepping circuit Jfor motor magnet 220 extending from the right hand alternate contact of relay 106 or the similar contact of relay 112. It the lirst trunk leading to central oliice is busy7 ground will theretore be extended through the sleeve brush 225, the middle right hand alternate contact of relay 210, the left hand normal contact of relay 224, the middle alternate Contact of relay 229 and the winding oi this relay to grounded battery. Relay 229 will therefore remain energized and maintain a stepping circuit for motor magnet 220 extending from grounded' battery throughr the winding of this magnet the winding ot relay 209, the Contact otmagnet 220., the right hand alternate Contact ot relay 229 and the right hand alternate contact of relay 2110 to ground. Motor magnet 220 will therefore continue to operate and step the brushes of the connector switch until brush 225 encounters a terminal free from ground. The locking circuit tor relay 229 will then be opened and this relay will release to permanently open the stepping circuit7 whereupon the brushes ot the switch will be brought to rest upon the terminals of the idle trunk leading to central office. The release of relay 229 also opens the locking circuit for relay 240 which thereupon restores to again place ground upon the terminals ot' the central office trunk engaged by brush 226. The circuit is now established for relay 207 extending from grounded battery through. the winding of said relay, the left hand normal contact of relay 229, the normal contact of relay 228, the right hand normal contact of relay 224, the next to the innermost right hand alternate contact of relay 210, the brush 226 and the normal contact of relay 240 to ground. Energization of relay 207 connects the talking conductors throughthe lett hand alternate contacts of said relay to brushes 205 and 234;. A circuit is now established for Aline relay 115 extending from grounded battery through the left hand winding of said lll) relay, ,the middle normal contact of relay 110, the lower talking conductor, brush 223-1- Ot the connector switch, the lett hand normal contact ot' relay 222, the outer lett hand alternate contact o'i. relay 20?, the middle normal contact of relay 201, brush 215 of the line linder, the calling subscribers substation apparatus, brush 216, the lett hand normal contact. of relay 201, the right hand alternate Contact ot relay 20T, brush 205, the upper conductor ot the trunk, the right handnormal contact ot' relay 110 and the right hand winding ot relay 115 to ground. Relay 115 energizes and establishes an obvious vcircuit for relay 112 whiclnin energizing, Vcauses the operation ot' relay 107 to lightthe busy lamp 108. The energization ot' relay 112 also grounds the test conductor ofI the trunk terminating in Vthe multiple bank ot the connector switch so that this trunk will test busy on other calls. The energization ot' line relay 115 extends the ground'trom the normal contact ot' relay 10S through the lett hand alternate contact ot relay 115 to the tip side otl the trunk terminati-ng at the central o'liice, whereupon the linel relay 102 at said otlice is energized to light the lamp 130 associated with the trunk taken tor use to indicate to the central ottico operator thata call is awaiting attention. The operator then insertsthe plug into jack 100, whereupon the trunk relays shown in Fig. 1 will operate in the same manner as described in connection with a call 'from centralfotiice. Upon the energization ott relay 106 a circuit is established for relay 110 through `the lett hand alternate contact ot relay 112 to ground at the lett hand alternate contact ot' rela-y 106. Relay 110 energizes to open energizing` circuit for relay 115 and extends the callingline through to the central otiice opera-tors cord circuit.

At the termination of the call, the replacing of thereceiver upon the switch hoolr at the called substation caused the release ot thesupervisory relayin the central otlice operators cord circuit which results in the lighting ot the supervisory lamp thereof in the usual well-known manner. The central ottice operator then removes the plug trom jack 100 to restore to normal the apparatus associated with tlietrunk in Fig. 1 in the same manner as previously described. The restoration of the receiver upon the switch hook at the called substation also opens the circuit 'ot supervisory relay 103 which thereupon deenergizes to release relay 100. Upon deenergiZat-ion of the latter relay the holding 4ground at its right hand alternate/,contact is removed trom relay 210 and this relay thereupon releases. The selt-interruriting circuit "for motor magnet 211 ot the line finder switch is now closed as previously described to step the brushes ot the switch to their normal position. The release of relay 210 also establishes a circuit for 4relay 229 extending Yfrom Vgrounded battery through the winding ot said relay, the lniddlenormal contact ot relay 210, testbrush 226, engaged testterminal and thefnormal contact oitl relay 240 to ground. Relay 229 energizes to close a stepping circuit for motor magnet 220 extending trom grounded battery through the windingotsaid magnet., Winding ot' relay 209, the .contact of magnet 220, the right-hand alternate con tact ot' relay 229 and the right-hand normal contact ot relay 203 which was deenergized upon the release of relay 2041. circuit to step the brushes ot the connector switch from the terminals engaged to the next set ot terminals in the connector bank. lt will be obvious, that as long as the brush 226 encounters ground upon its associated termina-ls, the circuit tor relay 229 will be maintained to cause the continued operation ot the motor magnet. In the case or'. all subscribers lines, ground is connectedk directly to the terminals over which brush 226 passes. lVhen saidbrush engages terminall 221", ground will be 'found at the normal contact ol relay 204. Ground is placed upon the next succeeding terminalI from the right'- hand normal contact of relay 210 andwhen brush 226 engages the terminals individual to the trunks extending to the attendants position, ground is found at the normal contact ot relay 241. The lasttest terminal in the connector bank isconnectedto ground at the normal contact ot relay 204 and 'it willI thus be obvious that magnet 220' will operate to step the` brushes and the switch to their normal positions. Relay 229, .no longer linding ground, will release to permanently open the stepping circuit for the switch which will thereupon be in a position to extend another call.

'uosc/rf-cfl' initiates a @all to' Hte attemlaat.

A subscriber within the private branch exchange may establish a coiniection tothe attendants position by dialingthe digit 0 after removingreceiver from switch hook at the calling substation. In responsel ,tothe ten switch operates as previously described,.to engage the brushes with the eighth set of terminals shown in the connected baul-. Relay 209 then releases as before, to establish a. circuit tor relay 229through brush208. rThe taiergizatiouot relay 229 in this circuit establishes an energizing circuit tor relay=211 traceable from grounded battery through the winding of said relay, the outermost right-hand alternate contact ot relay T210, test brush 226 next to ther innermost.rig'` thand alternate contact of relay 2,10, the right-hand normal contact of relay 224i', the nori'nal contact ot relay 228, the lett-hand alternate Contact oit' relay 229 and froml Magnet 220 operates in lthis impulses transmitted, the connector,

thence over the energizing circuit for the latter relay to ground at the right-hand normal contact ot relay 209. Relay 2&1 locls in a circuit extending through its winding and left-hand alternate contact, the right-hand alternate contact of relay 229 and the righthand alternate contact ot relay 2-'2-1 to ground. A stepping circuit is now established tor motor magnet 220 extending trom grounded battery through the winding ot said mag-- net, the winding ot relay 209, the contact ot magnet 220, the right-hand alternate ccntact of relay 229, and the right-hand alternate contact ot relay 2st to ground. iViagnet 220 operates to step the brushes ot the switch over terminals associated with trunks leading to the attendants position. The busy condition ot' these trunks is denoted by ground upon the sleeve terminals thereoi. over which brush 225 passes, said ground being extended to each sleeve terminal from *the lett-hand alternate contact ot relay 204 of the busy switch connected to the trunk extending to the operator-s position, through the innermost right-hand alternate contact of relay 210 ot said switch, the right-hand normal contact ot relay 229, the left-hand normal contact ot relay 224, next to the outermost right-hand alternate contact ot' relay 210 to the brush 225. Therefore,` should the brush 225 of the connector switch now seeking an idle trunk leading to the attendants position encounter ground upon the sleeve terminal ot the first trunlt. a locking circuit will be maintained tor relay.229 extending through the winding and the middle alternate contact of said relay, the lett-hand normal contact oit relay 22a'` and trom thence over the path just traced to the brush 225. Relay 229 therefore, remains energized to cause the continued operation ot magnet 220. lV hen brush 225 encounters a terminal tree trom ground, relay 229 releases to permanently open the stepping circuit ot thi connector switch whereupon the brushes thereotl come to rest upon the set ot terminals indivifiual to the selected idle trunk extending to the attendants position. The release ot relay 229 also opens the locking circuit tor relay 2-111 which thereupon deenergizes to again place ground upon the test terminals individual to the trunks extending to the attendants position. Each trunk terminating at the attendants position has associated therewith, a .lamp 131 which is lighted when the trunk is seized, over a circuit traceable Vfrom grounded battery through said lamp, the normal Contact ot the key 132, tne sleeve terminal ot the trunk in the con- I nector bank. the brush 225, the nef-:t to the relay 210 and the lett-hand alternate contact ot relay 20% to ground. The attendant observing the lighted condition ot the lamp 1.31, can now operate the key 132 ot the trunk taken tor use and thereby connect her telephone set with the calling substation line. it the termination ot the conversation between the subscriber and the attendant, the replacing oi" the receiver upon the switch hoolt at the calling substation again causes the release ot the line finder and the connector switches in the same manner as previously described.

The attendant may initiate a call direct to cent 1al oiiice by operating the listening hey 1111-. whereupon line relay is energized with the result that the central o'tiice operator is signaled as previously described in connection with the establishment ot a call trom a subscriber to central otce.

What is claimed is:

1. ln a telephone system, a branch otlice, a main,` otiice, connecting circuits including numerical automatic switching mechanism at the branch oliice, an attendants position thereat, subscribers lines terminating at the branch ollice, senders associated tlierewitl'i Jfor setting said switching mechanism to interconnect said lines, a trunk extending between said oliices, a signal vfor said trunk at the branch otiice actuated when the trunk is taken ttor use at the main oliice, means controlled from said position 'for causing said trunk to be connected to an idle one ot said connecting circuits, and a sender 'tor setting the numerical automatic switching mechanism thereot` to select the desired subscribers line.

2. In a telephone system, a branch oliice, a main oltice, connecting circuits including numerical automatic switching mechanism atthe branch oltice, an attendants position thereat, subscribers lines terminating at the branch oiiice, senders associated therewith for setting said switching mechanism to interconnect said lines, a trunk extending between said offices, a signal tor said trunk at the branch otiice actuated when the trunk is taken 'tor use. at the main oilice, an automatic non-numerical switch, means controlled by the attendant tor causing said non-numerical switch to connect said trunk to said numerical switching mechanism, and a sender tor setting said mechanism to connect with a subscribers line.

3. in a telephone system, a branch oliice, a main ottice, connecting circuits including numerical automatic switching mechanism at the branch office, an attendants position thereat, subscribers lines terminating at the branch oliice, senders associated therewith for setting said switching mechanism to interconnect said lines, a trunlt extending between said otlices, a signal for said trunk at the branch ottice actuated when the trunk taken for use at the main ctiice, an automatic non-numerical switch, means controlled by the attendant tor causing said non-nunierical switch to connect said trunk to said numerical switching mechanism, and a sender at said position for setting said mechanism to connect with a subscriber-s line.

4. Ina telephone system, a private branch exchange, subscribers lines terminating thereat, connecting circuits thereat includ ing numerical automatic switching mecha nism, senders associated with said subscribers" lines tor setting said switching mechanism to interconnect a pair of said lines, a central ofiice, trunks extending therefrom to the private branch exchange, means controlled by the attendant there-at for causinga calling incoming' trunk to be connected to an idle one ot said connecting circuits, and a sender for controlling the numerical automatic switching mechanism of said connecting circuit to connect the calling trunk with the desired subscribers line.

5. In a' telephone system, a private branch exchange, subscribers lines terminating thereat, connecting circuits thereat including numerical automatic switching mechanism, senders associated with said subscribers lines tor setting saidswitching mechanism to interconnect a. pair ot said lines, a central oliice, trunks extending therefrom to the private branch exchange, means controlled by the attendant there-at for causing a calling incoming trunk to be connected to van idle one of said connecting circuits, a sender, means for connecting the same to the calling trunk to control the numerical automatic switching mechanism oit said connecting circuit to connect the calling trunk with the desired subscribers line.

6. In a telephone system, subscribers" lines, a private branch exchange wherein said lines terminate, connecting' circuits at said private branch exchange,'cach including al tinder switch, numerical vautomatic switching mechanism, senders 'for said subscribers lines for building'up connections between subscribers lines by means ot lsaid switches, a central oiiice, trunks extending therefrom tosaid private branch exchange, an attendant station at said private branch exchange, signals thereat t'or said trunks, neans controlled by the attendant tor causing an idle finder to connect with a calling trunk, and a sender for setting the associated numerical automatic switching mechanism to connect the calling trunk with the desired subscribers line.

T. In a telephone system, subscribers lines, a private branch exchange wherein said lines terminate, connecting circuits at said private branch exchange, each including a finder switch and numerical automatic switching mechanism, senders for said lsubscribers lines tor building up cenynections between subscribers lines by 4"ineaiis ot said switches, a central cnice, trunks exy tending therefrom tosaid pi'ivfatebr'anch exchange, an attendants station at said private branch exchange, signalsv the-reat'tor said trunks, means controlled by' theat-` tendant for causing an idle tindei `to conf" nect with a calling trunk, andV as'end'er said position lor setting the numerical -autoni-atie `switching mechanism to connect-the calling trunk with the desired subscribers line.

8. In a telephone system, subscribers lines, a prw'ate branch' exchange` wherein said lines terminate, connecting circuits` at said private branch exchange, each including a finder switch and a 4co'niiect'or switch, senders tor said subscribers lines-torl building up local connections bynieansfetl said switches, a centraho'tiice, 'trunks eX-l tending therefrom to said' private branch4 ing a linder switch and a 'coi'inectbr switch,"` senders 'for said subscribers lines tor buildf ing up local connections by n'i'eansotfsaid switches,` a central cnice, trunks extending thereirom'to said 'private branch 'excl'iange Y ndan idle and terminating thereat in fixed'terininal'sl at said nnders, an attendants station 'at private branch exc'h'ai'ige, signals ther'eat for said trunks, means controlledbysa'id attendant :tor causing an idle findento select a callii'ig trunk, and a'seiider Iat said position for setting the associatedconnectorto connect the calling trunk with Vthe desired subscribers line, y

10. In a telephone system, subscribers lines a )rivate branch exchange whereinsaid lines terminate, connecting circuits at said private branch exchange each includl ing a finder switch and numerical automatic switching mechanism, senders for said subscribers lines for building up"localfco'nnections by means of said connecting circuits, a central office, trunks'eirtending therefrom to said private branchexchange Aand terminating thereat in tixed' termi`iials at,`

said finder switches, an attendants station atsaid private branchI exchange, signals thereat tor said trunks, means c'lontro'lledfby the attendant tor causing an'fidle tinde'iii'ic select a callingtrunk, a sender tor settingthe associated numerical vautomatic switching mechanism to connect the calling trunk with the desired subscribers line, and other trunks extending from said private branch exchange to Said central office and terminating in fixed terminals at said numerical automatic switching mechanism 'for extending connections from said subscribers lines to said central office.

l1. In a telephone system, subscribers lines, a private branch exchange wherein said lines terminate, connecting circuits at said private branch exchange each including a finder switch and numerical automatic switching mechanism, senders for said Subscribers lines for buildingup local connections by means of said connecting circuit-s, a central office, trunks extending therefrom to said private branch exchange and terminating thereat in fixed terminals at said finder switches, an attendants station at said private branch exchange, signals thereat for said trunks, means controlled by the attendant for causing an idle finder to select a calling trunk, a sender for setting the associated numerical automatic switching mechanism to connect the calling trunk with the desired subscribers line, and other trunks terminating in fixed terminals at said numerical automatic switching mechanism Land leading to said attendants station for extending connections from said subscribers lines to said station.

12. In a telephone system, subscribers lines, a private branch exchange wherein said lines terminate, an attendants station thereat, connecting circuits at said priva-te branch exchange each including a finder switch and a connector, senders for said subscribers lines for building up local connections by means of said connecting circuits, a central office, trunks extending therefrom to said private branch exchange and terminating thereat in fixed terminals at said private branch exchange, signals thereat for said trunks, means controlled by the attendant for causing zn idle finder to select a calling trunk, means for sett-ing the associated connector to connect the calling trunk with the desired subscribers line, trunks terminating in fixed terminals in said connector, and extending to the central office, and other trunks terminating in fixed terminals in said connector and extending to said attendants station, said connector being arranged to select an idle trunk in either group under control of said sender.

13. 1n a telephone system, subscribers lines, a private branch exchange wherein said lines termina-te, an attendants station thereat, connecting circuits at said private branch exchange each including a nder switch and a connector, senders for said subscribers lines for building up local connections by means of said connecting circuits, a central oiiice, trunks extending therefrom to said private branch exchange and terminating thereat in fixed terminals at said private branch exchange, signals thereat for said trunks, means controlled by the attendant for causing an idle finder to select a calling trunk, means for setting the associated connector to connect the calling trunk with the desired subscribers line, and trunks terminating in fixed terminals in said connector and extending to said attendants station and to said central ofiice, said trunks being arranged in a single row in said connect-or, said connectors being adapted under control of said senders to select a trunk of either character.

14. In a telephone system, subscribers lines, a private branch exchange wherein said lines terminate, an attendants station thereat, connecting circuits at said private branch exchange each including a. linde-r switch and a single movement connector, wherein said lines terminate, senders for said subscribers lines for building up local connections vby means of said connecting circuits, a central office, trunks extending therefrom to said private branch exchange and terminating thereat in fixed terminals at said private branch exchange, signals thereat for said trunks, means controlled by the attendant for causing an idle finder to select a. calling trunk, means for setting the associated connector to connect the calling trunk with the desired subscribers line, and trunks terminating in xed terminals in said connector, one group of said trunks leading to said attendants station and another group of said trunks leading to the central office, said trunks being arranged in groups in a single row in said connector, whereby the connector may be set by a number of sets of impulse-s from a subscribers sender to pick out a local subscribers line or a trunk in either group.

15. In a telephone exchange system, a private branch exchange wherein said lines terminate, an attendants position thereat, connecting circuits including finders and connectors, subscribers lines terminating in said finders and connectors, a central ofiice, trunks leading from said central oflice and terminating in said finders, a signal and a manual switch for each trunk at said private branch exchange, means controlled by said manual switch for causing an idle finder to extend a calling trunk to the associated connector, and a sender at said position for connecting the said trunk wit-h the desired subscribers line.

16. In a telephone system, a private branch exchange, subscribers lines terminating thereat, connecting circuits thereat including numerical automat-ic switching mechanism., senders associa-ted with said subscribers lines for setting said switching mechanism to interconnect a pair of said nol lines, a central oiice, trunks extending therefrom to the private branch exchange, means for causing a calling incoming trunk to be connected to an idle one of said connect-ing circuit-s, and a sender for controlling the numerical automatic switching mechanism of said connecting circuit to connect the calling trunk with the desired subscribers line.

17. In a telephone system, a private branch exchange, subscribers lines terminating thereat, connecting circuits thereat for extending connections, a central office, trunks extending therefrom to the private branch exchange, and line finders for said connecting circuits for extending connections `from said connect-ing circuits to said subscribers7 lines or to said trunk lines.

In Witness whereof, I here-unto subscribe my name this 15th dayo July A. D., 1920.

LEO KELLER.

Images