US1478022A - Telephone system - Google Patents

Description

Dec. 18 1923.

1,478,022 w. w. CARPENTER ET AL TELEPHONE SYSTEM Filed Dec. 22 1920 6 Sheets-Sheet l /n venfars': War/6f? W. Game/772m Dec. 18 1923. 1,478,022

W. W. CARPENTER ET AL TELEPHONE SYSTEM Filed Dec. 22 1920 6 Sheets-Sheet 2 hue/17ers: v Warren WCa/penfe/f Hen/y Ha /anal by ekmmew #5 Dec. 18 1923. 7 1,478,022

' w. w. CARPENTER ET AL TELEPHONE SYSTEM Filed Dec. 22', 1920 6 Sheets-Sheet s /nvenfors: War/en WLa/penfen Hen/y Ha /and.

Dec. 1s,192s. 1,478,022

W. W. CARPENTER ET AL TELEPHONE SYS TEM /n venfors: Warren M (a/penfe/r 6 Sheets-Sheet 4.

Filed Dec. 22 1920 Henry fiov/and y QKM 5- Dec. 18 1923.

. w. w. CARPENTER ET AL TELEPHONE SYSTEM Filed Dec. 22 1920 6 Sheets-Sheet 5 65:. Egan 3 35. v

mkww QRSQ jlslrllsl kmm QTISQ //1' van furs: War/en (Co/pen fer.

Dec. 18, 1923.

W. W. CARPENTER ET AL TELEPHONE SYSTEM F 22 ts-Sheet 6 the int a Patented [lee ill, i923.

Uhll'lED STATES PATENT OFFICE.

WARREN XV. CARPENTER, OF BROOKLYN, NEW YORK, AND HENRY HOVLAND, OF

CORPOE-ATED, OF NE'VJ YORK, N. 55., A COBPORATIGN OF NEVJ YORK.

TELEPHONE SYSTEM.

Application filed December 22,

To all Yul tom it may cancer-1t:

Be it known that we, VVAnnnN N. CAR- rnnrsn and HENRY lovLANn, citizens of United States, residing at Brooklyn in the county 01": Kings and State oil- New York, and li ast Orange, in the county of Essex and State of New Jersey, respectively, have invented certain new and useful Improvements in Telephone Systems of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systerns and particularly to systems involving the use of machine switching apparatus for esta vlishing connections.

The object of the invention is to provide means, in a system where selective switches are operated over an impulse circuit from a central ollice register sender to extend a connection to a subscribers line, whereby the final one of said switches is controlled in response to a special condition impressed by the sender upon said impulse circuit to extend the connection to the subscribers line regardless of its busy condition.

A. feature of the invention relates to the provision of manually operable means for slice-ting a given operation of the impulse relay which normally serves to send operating impulses "from the sender to actuate the switches to so modify the operation oi the final switch that the subscribers line is se lected regardless oi its busy condition and the usual busy signal rendered ineffective.

(lther features and advantages of the present invention will become more readil understood from a consideration of the tollowing description taken in connection with the appended claims.

Referring to the lrawing which constitutes part of the application. Figures '3. to inclusive. when arranged in the order illus- .ed in Q' l, discloie the detai ed cirand )p'aratus oil portion of a. tele phone stem embodyii'lg the principles of tion.

3 hows. at the left of the broken p of the. equipment at toll conoperators position and the outgoing A a Clliflllt which leads to a seswitch at a cordless operators position in the same oilice. To the right of the Serial No. 432,427.

broken line there is shown the incoming end of the trunk circuit at the cordless operatofis position together with certain controlling and supervisory elements.

Fig. 2 at the left shows selector switch in which terminates the trunk interconnecting the toll operators position and the cordless operators position. To the right of ig. 2 is shown a second group selector switch.

Fig. 3 illustrates a linal selector or connector switch to which the switches shown in Fig. 2 have access and serves for completing connec.ions to the subscribers lines.

Fig. 41 discloses a switching unit made up two trunk finder switches which act to an tomatically associate an idle register sender with the particular trunk circ t at the cordless operatcrs position that h'as been taken for use in the extension of a toll connection. This figure further shows an allotter switch for assigning an idle register sender for use.

Fig. 5 shows an operat ons keyboard consisting of a plurality of rows 01" number lreys, one of which is provided for each cordless operators position. This figure also illustrates one of a plurality oi register General description.

The present invention is particularly applicable to toll switching systems and has to do with the provision of means for onahlinp; a toll connection to be set up over automatic switches to the line of a calling suliscriliier. who has previously initiated the toll call. regardless oi? whether his line has late been made busy, as by being called by other subscribers in the exchange or for any other reason. To accomplish this tea ture certain devices are provided in connec tion with the register sender at the cordless operators position which controls the selective operation of the automatic switches in building the connection to the calling subscribers line for so influencing the op '30 TESTER-N ELECTRIC COMPANY, IN-' eration of the final or connector switch that this switch will seize the subscribers line even though it tests busy without CllllSl) the actuation of the usual busy signal. For a clearer conception of the manner in which a toll call is handled and the part played by each oi the different operators, atte:.1tion is called to the diagrammatic layout in Fig. 6. After having studied this schematic showing the functions of the selective switches and controlling mechanism shown in detail in the other figures will be more readily understood.

At the left of the figure a calling subscribers line 830 is shown terminating in the jack 603 before an answering operator in the exchange. It will also be observed that the calling subscribei:"s line terminates in the multiples of a connector switch C in the same oflice. The subscriber at line 330, wishing to make a toll call, removes his receiver from the switch hook causingthe illumination of the usual line signal at the answering operators position. She answers the call by inserting the plug: 60d of one of her cord circuits in the jack 603. The insertion of the plug in the jack may cause the association of the operators head set 600 with the cord circuit by means of auto matic devices, or, as illustrated for the sake of simplicity, her telephone set may be placed in talking relation with the calling subscribeii"s line by means of the ordinary listening-in key 609. The answering operator, on learning that the calling subscriber wishes a toll connection, connects her head set, as by means of a key (301, to an order wire 602 interconnecting her position with the position of a toll connecting; operator, illustrated within the dotted rectangle n the upper right-hand corner oi the figure, The toll connecting operators head set 606 being thus placed in talking relation with the answering operators equipment, she rcceives from the latter operator, orally, all the necessary-information required for tl completion of the connection.

The toll connecting operator next manipulates a key 605 which. establishes a talking connection between her telephone set, over the order wire 610, and the telephone set 607 of a cordless operator. Over the order wire the toll connecting operator communicates with the cordless operator, gives her the number of: the calling subscriber-"s line and also requests the assignment oi? an idle trunk to be used in the establishment of the toll connection. The cordless operator thereupon assigns a trunk, such as the trunk 108, brings about the association of a register sender 608 with the assigned trunk and records the designation of the calling line on her keyboard. At this time the toll connecting operator may advise the answering operator, either by an oral sl: 1 ina take down her connection with the Inc by removing the plug 604-, From NJ G03.

After the record of the calling subtribers line has been set up on the registers of the sender 608, the switches El S and C are directly operated to extend the assigned trunk 107, 108 back to the tcrminals oi the calling subscribers line 330. Should the connector switch C reach the terminals of the calling; line prior to the time the answering operator removes the plug from jack 003, or should the call- 111, line be seized by another con ection during the interval that might exist be tween the time the answering operator removed the plug 604 from the jack 603 and the time the connector switch C reaches the terminals oi the calling line, a busy condi tron would be found thereon. However, by the provision of means to be taken up in detail hereinafter, the circuits are so ar ranged that the connector switch C will disregard such a busy condition of the callinc; subscribers line.

In the meantime the toll connecting operator has inserted the plug of her cord circuit in the jack 101 of the trunk assigned to her by the cordless operator and with the (.l'illlflf plug of her cord circuit has pro-- ceeded to establish a connection through to the called line 611.

lVhen the connection has been completed in both directions, the called subscriber has answered and the toll connecting operator, :lailing to receive a busy signal, knows that the calling suliiscribers line 330 has not been rezdered busy, in the meantime, she brings about the application of ringing current to notify the calling subscriber, who may have replaced his receiver on the switch hook, that the desired party has been obtained.

Should, Ilor one of the reasons above set truth, the calling subscriber's line he rendercd busy whil a toll connection is being, established, the toll operator a'lter havinii' obtained the desired party may listen in on the connection estal'slished in the meantime and notify the calling subscriber at station 330 that she has succeeded. in obtainiiu; the toll connection. may then discontinue the local call and converse with the subscriber o1 lnally called.

Comparin s. i to 5 inclusiir with the din am cl '3. (3, it will be seen that those illustrate the detailed circuits and equipment located at the cori'lless operatoi"s The switches 5i, 9 and 0 shown iatically in Fig. (3, are the switches disclosed in detail in Figs. 9, and 23. these switches, in the detailed iowing, are an :d in accordance with the usual convention to build the connection from Description of apparatus.

The automatic switches shown in Figs. 2 and 3 are of the two motion step-by-step t pe in which a primary stepping magnet operates in response to a series of directive impulses to advance the brushes to select the desired group and then a secondary stepping magnet operates to move the brushes over the chosen group to select a set of ten minals therein.

The trunk finders consist of single move ment rotary step-by-step switches each made up of a plurality of arcuate rows terminals and cooperating brushes. in trunk finder unit consists of two of these rotary switches, one of which is designated TF and the other is designated TF The pur pose oi utilizing two switches per unitis to increase the number of trunk circuits at the cordless operators position that may be as sociated with the register sender without the necessity of employing large capacity switches. Half of the trunks, such as the trunk 107. 108 shown in Fig. l at the operators position. are apport mod to the trunk finder TF and the remaining half oi" said latcd to the second trunk finder switch. the first trunk finder will continue to opci to until it has made a test out all the trunks which it serves. Thereafter, the second trunk finder switch TF begins to operate and finds the desired trunk. In the drawing the several sets oi terminals id brushes of each oi. the trunk tinder swwi'hes of a given unit are located within the area oncloscd by the dotted e ugh-s. il ithiu he lower rectangle are slump. the stopping: mag. lOZ-l and the lli'lllrlil'ilj 1nd lcrini: belonging to the trunk linder TF. stepping magnet 4:09 and the saw of terminals which comg'u'ise the i trunk finder switch TF are shown within the area of the upper broken rectauy The operator-"s keyboard illus rated in Fig. 5 comprises four rows of ten keys each cord the number oi anyone of 191,000 lines.

In addition to these keys the operators posi tion is equipped with a key 583 which places the sender in condition to accomplish the no test operation o'l. the connector switch C. These keys are of the locking type and any depressed key will remain in its actuated position until released by the energization of an electromagnet. The release magnets for the thousands. hundreds, tens, units and no test key are shown respectively at 528, 5929, 530, and 532. In addition to the ten number keys a common contact is provided for each of the four rows. These contacts, which are identified by the characters 565, 566, 56? and 568, are closed whenever one ot the keys in the corresponding rows is actuated.

The operators keyboard briefly described above is common to a plurality of trunk linder and register sender units. One of the register sender units at the operators posi* tion is ill strated in detail in Fig. 5. The registers, of which there are tour one for each of the four digits of a subscribers numher consists of single motion step-by-step rotary switches. The thousands register 501 is provided with a stepping magnet 502, the hundreds register 50% with a stepping magnet 507, the tens register 511 with a stepping magnet 512 and the units register 516 with a stepping magnet 17. which may;- nets operate to step the brushes of their respective registers from position to position. The stepping magnets, the brushes and their coacting terminal banks and the other elements pertaining to each of the tour registers are shown within the corresponding broken rectangles at the right-ham side of Fig. 5.

The sender control switch is likewise of the stcp-by-ste i rotary single motion design. This switch consists oi? a stepping magnet 555 and a plurality of brushes and terminal rows. The several brushes of the sender control switch are, for convenience, distributed throughout Fig. 5.

Each ot the register sender units iurthermore equipped with a time measure switch, the function of which is to regulate the advance of the sender control switch from one position to another in such manner that the automatic selective switches S and S are given a sutlicient time to complete a maximum trunk huntii'ig operation before the register sender is permitted to start the The time measure switch,

next selection. generally designated by the letter T. comprises a small rotary step-bystep device including the stepping}; magnet 545 and a plurality 0t brushes and terminal rows. All the elements of the time measure switch are confined within the area of the broken rectangle in the lower left-hand corner of Fig. 5.

In order that a trunk finder and register sender unit may always be allotted for use,

when one is idle, and to avoid confusion in apporti ii, the same, an allotter switch AL is provided. The allottcr switch likewise consists of a small step-by-step device in which a stepping magnet 41-24 is designed to move the several switch contacts from one position. to another. The several elements belonging to the allotter switch are shown within the space of the broken rectangle at the right of Fig. 4.

It is believed that a more thorough understanding of the invention may behad by giving a detailed description of the method of operation of tl c system.

Opemtionof system in detail.

Let it be assumed that the subscriber of line 380, wishing to obtain a toll connection with the subscriber of line 611, shown in Fig. 6, and omitted from Fig. 1 for sake of clear ness, has initiated the call and that the necessary information regarding the connection has been communicated to the toll connecting operator. She thereupon requests the cordless operator to assign an idle trunk. The trunk 107,108,being idle at this time, is assigned by the cordless operator.

At the time the cordless operator communicates the identity of the assigned trunk to the connecting operator she also depresses an assignment key 126 individual to said trunk. The purpose of this key is to cause the operation of the allotted trunk finder to associate an idle register sender to the trunk to which said hey is individual. A circuit is completed from battery through the winding of relay 125, contacts of key 126, righthand armature and contact of relay 122, back contact and right-hand armature of relay 124:, closed contacts of key 127 to ground. lie ay 125 operates and locks as follows before the contacts of key 126 open when re leased by the operator: battery through the winding and front contact and inner righthand armature of relay 125, and thence to ground as traced through the lejl'thand con tacts of key 127. Relay 125 establishes a circuit from ground through its inner left-hand armature and contact, conductor 135, lower rig t-hand contact 125 (1) of the allotter switch, brush 550 of the sender control switch, contact 569, conductor 4:42, winding of relay 41-06 to battery and ground. Relay 106 becomes encr d and completes a circuit from ground through its outer right-hand armaturo and front contact, conductor :33, terminal 570, brush 541-9, contact and armature and winding of stepping magnet 555 to battery and ground. ihe magnet 555 energizes, interrupts its own circuit and deenergizes to advance the brushes of the sender control switch on to their first position terminals.

It may be well to note at this time that the sender control switch, the register switches, the time measure switch, the trunk finder vncctor terminals and brush 115.

position the relay 4:06 is maintained encr gized, the circuit therefor being now closed through the brush 550 and terminal 571.

The stepping magnet 4:08 of the first trunk finder TF commences to advance the brushes 410, 111, 112, etc., from position to position to search for the calling trunk circuit. The circuit for operating magnet 108 may be traced from battery through the winding of said magnet, armature and contact thereof, conductor 143, through the connector tern'iinals with which the brush e15 cooperates, intermediate left-hand armature and front contact of relay 106, terminal l i-i, brush 4:15 to ground. On the first operation of stepping magnet lOS the several brushes of the trunk finder TF advance to their first position terminals. The opera ing circuit for the stepping magnet 4:08 therefore leads over the conductor 1 13 and thence directly to ground through the con Since the calling trunk is not represented in the terminals of the first trunk finder switch, the stepping magnet 408 will continue to operate until the brush 115 steps 0d the last one of the series of connected terminals and makes engagement with terminal 1 15. The circuit of mag-net 4%.08 being opened the switch comes to rest and a circuit is estab lislied as follows for operating the second trunk tinder switch TF battery through tlie wiudiug and armature and contact of stepping magnet 109, front contact and innermost left-hand armature of relay 406, terminal 1 16 upon which the brush 122 of the second trunk tinder switch. is now standing, brush 4e22, terminal dlti, brush 4-15 to ground. lllagnet 4.09 energizes, interrupts its own circuit and dcenergizes to advance the brushes ll'i', 418, 119, etc. to the terminals representing the first trunk in the group which is served by the trunk finder switch TF Hereafter the operating circuit for the stepping magnet 4t09 leads from battery through the winding and armature and contact of said magnet over the series of connected terminals. which brush 4:22is now engaging ierniiinal l l-Ii and brush 115 to ground. in parallel to the above circuit a circuit is cstablishmi from battery through the winding of relay 407, inuern'iost left hand armature and contact of relay 106, brush 1-22, terminal 4e45, brush 4-15 to ground. liclay 107 energizes for a purpose presently to be considered.

N hen the brushes of the second trunk finder reach the terminals identifying the assigned trunk circuit at the operators posis tion, a test circuit is closed from battery through the winding of stepping magnet 409, front contact and left-hand armature of relay 4107. Winding of relay 1102, contact and inner left-hand armature of relay 401, brush 4-11, tern'iinal l-1:7, brush 4-18, terminz'il 44-8, condi'ictor 18%;, contact and outer lefthand armature of relay to ground. The stepping magnet 109 energizes permanently in this circuit and the brushes are stopped in engagement with the proper set of terminals. The relay 10.2 also becomes energized and establishes a circuit as above traced from battery through the Winding of magnet 109, front contact and lefthand armature of relay 4107, thence through the winding and contact and left-hand armature of relay d02 conductor 185, brush of the sender control switch, conductor 13e, brush no, brush 117, conductor 138, contact and on tor right-hand armature of relay 119, ".t'inding of relay 122, right-hand contacts of key 127 to ground. Stepping magnet 400, rel y 402 and relay 122 are locked in this circuit. Relay 402 at its inner righthaud armature closes an operating circuit for the relay 101. Relay 4:01 closes a hold ing circuit as follows for relay 107: battery through. the Winding and inner r ght-ha id iil'lPltlll'Q and contact of relay +107 to ground the outer left-hand. armature and contact of relay 4:01. Relay 5101 also completes a circuit from battery through the Vindlug of the slow to release relay 1041, contact and fight-hand ari'nature of relay 4:03, outer left-hand armature and contact of relay 4.01 to ground. The function of the relay 1.0% W? ll be tup hereinafter.

The relay 122 which also energizes in the holding circu serves to extend the conducto 130 and 187, which constitute the impulse circuit, from the sender to the first & foup s ector switch. Relay 122 at its right-hand armature and contact opens the holding circuit of relay 125. Relay 125 removes ground from the conductor 135 whereby relay 4-06 releases its armatures. lay 122 furthermore completes a circuit from ground through its outermost l ft hand armature and contact, winding of re lay 120 to b y and ground. Relay 120 becomes our iced. Lamp 118 is illumiuit through the inner right uated in a hand arn'iature and back contact of relay 117, left-hand armature and front contact of relay 120, back contact and innermost 1cft-hand armature of relay 12 1 to ground.

Registration of cuZZing Zinc number.

ground.

proper keys in the thousands, hundreds, tens and units rows on the keyboard. The keys pertaining to this particular number are key 557 in the thousands row, key 558 in the hundreds row, key 559 in the tens row and key 560 in the units row. As soon as a key in each of the four rows has been actuated the common row contacts are closed and circuits are established for the stepping magnets 502, 507, 512 and 517 of the registers. These circuits leau in parallel from battery through the windings and armature and contacts of said magnets, conductor 4.49, lower left-hand contact 450 of the allotter switch, conductor ass, common contacts 508, 50?, 566, 565 to ground. The stepping magnets of the registers interrupt their own circuits and advance the brushes from terminal to terminal in search of the depressed {eys on the operators keyboard. lVhen the thousand register 501 finds the operated key 557, a circuit is closed from battery through the Winding of magnet 502, winding of relay 503, brush (position 1), brush 504, ter minal 561, key 557 to round. hen the register 506 finds the depressed key 558 a circuit is completed from battery through the winding of magnet 507, relay 508, brush (position 1), brush 509, terminal key to ground. In a similar manner the circuits are completed through the windings of magnets 512 and 517 and the corresponding relays and 518 to ground through the operated keys 559 and 500, respectively. lVhen the registers reach positions corresponding to these keys the magnets are thereby permanently energized and the brushes brought to rest. After the last register has found the depressed key a circuit is closed from ground through the right-hand armatures and contacts of relays 518, 513, 508 and 508 in series, conductor 572, terminal 578, brush 5&8, contact and arn'iature and Winding of steppin magnet 555 to battery and ground. M: 505 interrrqfits its own circuit and any can the sender control switch to its secor 1 position.

Release 07 actuated lacy s.

In position of the sender control switch the depressed. keys on the operators keyboard are released inasu'iuch as they are no longer needed. The circuit for the release magnets 528, 529, etc. may be traced from battery through the windings of these magnets in parallel, terminal 574, brush 551 to With the keys released the relays 503, 508, 513 and 518 become deenergized and close a series circuit from ground over the left-hand armatures and contacts, terminal 575, brush 5&8, contact and armature and Winding of magnet 555 to battery and ground. The stepping magnet again onergizes and advances the sender control switch into position 3. The re ier sender has thus received the record of the calling subscribcrs line and is now in condition to. transmit series oi impulses in accordance with said record to operate the automatic switches to extend the toll connections over the assigned trunk 107, baclr to tne terminals of the calling subscribers line 2330.

Operation of first group selector switch.

The impulse circui' which is completed over the left-hand air itures and front contacts of relay 122, may be traced from battery through the right-hand winding o'l. relay 200 at the first roup selector S back contact and inner leit-lnnid armature of relay 207, conductor 129, middle left-hand armature and front contact oi? relay 122, conductor 136, brush 419, brush 412, back contact and left-hand armature of relay 400, contact and left-hand armature of relay 4023, brush 413, brush 420, conductor 137, front contact and innermost left-hand armature of relay 122, conductor 128, outer left-hand armature and back contact of relay 207, lefthand winding of relay 200 to ground. lie-lay 200 ener ires and closes a circuit from battery through the winding of slow to release relay 201, front contact and armature of relay 200, contact and outer rightdiand armature relay207, to ground. it will also be noted that the relay 405 is included in a circuit in parallel to the circuit leading through the contact and lett-hai'id armature of relay 403. .ielay 405, however, mains inert so long-:3 as its Winding is shunted by the contact and arn'iature of relay 403.

When the sender control swi ch reaches position 3 a circuit is established from battery through the Winding of relay 556, brush 544 and normal position terminal 576 of the time measure switch T, brush 536 (position 3), brush 520 to ground. Relay 556 becomes energized and closes a circuit from battery through the winding of magnet 555, contact and left-hand armature of relay 556 to ground. At the sametime a circuit is closed from ground through the front contact and inner right-hand. armature of relay 556, brush 539, brush 542, terminal 557, winding oi stepping magnet 545 to battery and ground. Magnets 555 and 545 are energized preparatory to advancing their brushes to the next position when the operating circuits are opened. On the next closure oi the con stantly rotating interrupter 451 a circuit is completed from ground through said interrupter, contact and outer right-hand armature of relay 401, conductor 436, winding of relay 552 to battery and ground. Relay completes a'circuit from ground through its contact and inner left-hand armature, contact and outer righthand armature of relay 556, left hand ari'nature and back contact of relay 554, winding of relay to battery and ground. Relay 553 operates and completes a circuit from battery through its winding and contact and armature, winding of relay 554, conductor 579, and thence to ground at brush 520. Relay 554 does not energize since its winding is shunted by the direct circuit to ground at the interrupter 451. As soon as interrupter 451 opens relay becomes operated and locks in series with relay 553. The next closure of the interrupter 451 and the consequent energization of relay 552 results in the establishment of a circuit from ground through the ri hthand armature and contact of relay 554, outer left-hand armature and contact oi relay 552, brush 5-37 (position 3), winding oi stepping magnet 502 to battery and ground. Magnet 502 attracts its armatures and prepares to advance the brushes 561. and 520 to their next position terminals when its circuit is severed. At the same time circuit is completed from ground through the contact and inner left-hand armature of relay 552, contact and outer right-hand armature of relay 556, left-hand armature and front contact of relay 554, conductor 430, windii'ig of the stepping relay 400 to battery and ground. Stepping relay 400 attracts its armatures and opens the impulse circuit lead ing to the selector S thereby permitting the release of relay 200. 1

Relay 200 on retracting its armatures closes a circuit from ground through the outer right-hand armature and contact of relay 207, armature and back contact of relay 200, armature and front contact of relay 201which remains energized during the transmission of impulses winding of slow to release relay 202, winding of theprimary stepping magnet 208 to battery and ground. Magnet 203 opera es to advance the brushes 208, 209 and 210 into operative relation with the first group of terminals. Relay 202 likewise energizes and establishes a circuit from battery througl'i the winding oi? relay 206, lowermost spin of the oil? nornial contact 211., armature and front contact of relay 202, conductor 1.30, middle ar mature and conta t of relay 12 it-hand contacts ott key 12a to ground. will be noted that the off normal contact 21.1 is closed the instant the brush shaft takes its first primary step. Relay 206, on energizing, locks up in a circuit from battery through its winding, lower springs 01' contact 211, armature and contact of magnet 205, contact and outer armature of relay 206 to ground at the contact and outer right-hand armature of relay 207. At the first primary step of the selector switch S a circuit is also closed from ground through the upper set 0i oil normal springs 211, conductor 131, winding of relay 124 to battery and ground. Relay 124, at its right-hand armature and front contact, provides a substitute ground connection from the left-hand contacts oi lllt) key 127 to conductor 130 so that this conductor Will remain grounded When later the relay 120 releases its armatures.

Relay 1%, at its innermost left-hand armature and back contact, opens the circuit for the lamp 118 and this lamp becomes e2;- tinguished. Relay 1%, in addition, completes a circuit from ground through the interrupter 123, middle lett-hand armature and contact of said relay, contact and innermost right-hand armature of relay 120, lamp 121 to battery and ground. Lamp 121 is flashed in this circuit to indicate to the operator that the establishment of the connec tion is The interrupter l5 causes relay and the open iits of magnet 502 and re Magnet i302 advances its crusher int position and relay 400 closes t for relay 200. Relay 200 in turn ch circuit through the Winding; of O2 and magnet 203 and recloses th "nit for relay 201. Magnet Q03 (ht-energizes hut relay 202, being slow to release, does not retract its armature. For each succeeding closure and opening of the tor i ter lfi'i relay 552 is operated to close .1 i the step- O-lSlLG'i 5G1 advances 1 stepping nm 'net 208 to ad- 'ance the brushes oi the selector switch rrom one group out terminals to the next. When all oi th register 5 1 disengages the last grounded terminal and relay 556 becomes deenergized. Relay 556 pens the circuits oi: the stepping magnets 5 3 and Magnet 555 releases the brushes of the sender control switch into position 4t and the magnet 54:5 releases the brushes r the time aser on. liemeasure switch to their t .3 and are also released as soon as ren'ioved from coi'iduetor 5Y9; measure snitch. is driven through jycle by oi the interrupter l continues close and open the 5Y2. The sleeping circuit n' easnre switch tery through the yer the connector 1 brush 54:2, brush l arms i relay 556, right-hand 4,

nand

LlLG

2.? "Mil t relay 552 to Tie pin. ose oi? the time measure 1 c Jl l swrtcn, as u iortn no einbetore, is to celay S qrl 101 0 mp1 (tile the e of the sender control switch son'iewhet greater than that re the automatic selective switch 'torin a rmnimnm trnnlr hunting .l, while the time measure ela 200, which in moulses have been sent the brush cuit is closed rrom battery th ough the inner aienature ant. contact of r leg," 206, Winding oi" the seeondery p ng magnet 20;"), normal contacts or rela 902 to the ground ed conductor f cg magnet hes It the brushes ode and 210 on to th first oi? tan- Ininals of t 1e selected group. l /lagnet 205, at its armature and contact, opens the hold ing 0 cuit of relay 206 W doenergizes and opens the ope 'ated circur of magnet 205. l\flagnet 20 5 again becomes deenergized end closes the following circuit provider the lint trunl: in the gron is busy at this time: battery t irough the winding of relay 20-3, lower springs or oil normal contact arn'ature and contact of magnet 205, bnclr contact will inner righthand armature oi r lay 207, brush 210 to ground on the test terminal 215 of the trunk. in parallel with this circuit 1 cu cuit also leads through the winding of relay 207 through the grounded conductor 130. Relay 207, however, LS shunted out by the direct connection to ground at the busy test terminal 21: and cannot operate. Relay 206 operates to close the'energizing circuit for steppii nagnet 205 which advances the brushes 0 the hex set oi nals. This method 01" operation continues until an idle trunk is reached, the test terminal of which is identified l y the absence of ground potential. Relay n t irivkl thcrcrore mils to energize and the brush s or the switch are brought to rest. Relay 207 non enorl.) with relay 206 to the g undcrl l LGlt" h L J m U the insistent o.

206 cannot res-ate.

s ther its contact end nn er ri armathrough the test 215 to render tli ins: line; to

for operating the secou group selector e is established trom battery through the right-hand Willtliihj 2? relay 2%, back contact and arn'n cure of relay 216, r brush 209, front contact {11H inner left-hand armature ol 1:. 20?, conductor 129, thence, as &..,'OVC trot, through the contact and armature oi the .tcpnng relay 4:00 and rellll) turning by Way of conductor 128, outer left hand armature and front contact of relay 207, brush 208, terminal 213, outer letthend ernuitrr'e and back contact of relay 21G, leitdmnd winding of relay 220 to ground. lleny 220 heeonies energized and completes e circuit from buttery through tl winding of relay 217, contact and right hand armature of relay 220, conductor 231 the grounded test terminal l'leley 21'? operates and locks up in a circuit from battery through its Winding and armature and eontz iet and thence to the grounded conductor 231, independently ol? the righthand tlilllttli and contact oi relay 220.

7571c second group selector switch.

ll lien the time measure switch reaches the next to its lest position brush Z342 disenthe lust of the continuously connected terminals and steps on to the terminal 578. it circuit is now completed from battery tnrough the Winding of rehiy l 3, conductor i539, terminal 580, brush 54:1, brush (position 4) to q: ind. lleluy 4:03 o' iierzitcs to remove the shunt from around the Winding oi relay 403. The purpose oi this is to pen niit the relay 41:05 to make it test oi? the iinpulse circuit to determine it the selector switch S has succeeded in. .lindiog en idle trunk. Since an idle trunk was found buttery current is connected to the impulse circuit through the windings of relay 220 at (v and relay 4-05 inunedh the next switch to lately operates when the slnint is removed at the left-hand armature and contact of e03. Relay 405 a circuit from butthrough the Wine ling of stepping inugnet e15, conductor 4:58, contuct end rightl1l1(l armature of relay l conductor 48?, t inel i378, brush 5 :2, brush 539, and t rhencr 1 ground at the rioht-hend armature t. o e. )(l coi'ituct of relay Cl'he time inch"- are s\'-.'itcn 'l advances to it normal po lteley 4.03 is tluereupou released, the .l and rtiuxy 4205 become de- LS the time iiiezieure switch 'l uiriiu-il position and since the sender co yol switch is now in posi' on 4i,

s iin e. circuit idietcly ves'uhlisheuil irroin buttery through the winding of relay conductor 579, brush 5%, terminal 57th brush 536 (position 4), brush 521 of the hundi'eos register 506 to ground. Relay 556, in the manner above eescrioed, closes the energizing circuits of the stepping mug;- nets 555 of the sender control switch and of the time measure switch T. Upon the next closure of the interrupter 1-51, reley 552 operates and closes the circuit for relay 553. Relay 553 energiices and prepares it circuit from battery through its Winding, Contact and zurinuture and the Winding of relay to grounc ed conductor 579. Relay elm Energize; immediately that the interrupter s .l locks in series with relay ["-\T' through the above traced circuit ii' ised from ground through the contactend inner lett-hend er- 1. o fl' niutuie (1i, ichiy l outer righthand no ure if reluy 51.6, left-hand ernur ure and trout contec of relay conductor and thence through the winding he stepping reluiy e00 to outcry and grori Stepping inugpet is energised nce the crushes 009 end 0121 socond group se- *h UlJ L) xfl on deenergizing completes e circui from ground t iroue'h the outer i' 'ht-hlu d armature and contact of relay E216 -u'urtuii'e and contact of relay eri'neture and front conict o winding oi? slow to release relay 2i), Winding oi the primary l'eppin -i; .llhgi et 2% to battery end ground. i'rlteppingi; magnet operates and mores the hrushe 255, 226 and 227 into operative relation with the first group of terminals.

The

relay 2'19 also becomes energized and Jletes e. circuit from battery through the rung 0i relay 218, lower springs of the ii tne first primary step of the switch-er1nuture and front contact of relay 219 to the grounded conductor 231. Relay 218 nttracts its erinetures and closes a holding circuit for itself "from batt ry through the winding ct seid ey, lower springs of content 529%; :u l Ture and context oi? the Y see 223., rout-ectand i v i. v u, We to jgl'OlYlllCl at the t haul armature oi lent opi-iniru oi" the interrupt rs the energizing;- ('i' QC V l stepping roe/net 5307 and the steop'ng' stepping relay L causes the primary stepping magnet 221 to move the brushes of the second group selector succesively from one group of terminals to the next. When the las ir pulse Oil the series representing the depressed key 558 has been transmitted to the switch. the brush 521 discngages the ground ed terminals and relay 556 becomes deenergized. Relay 556 opens the holding circuits of the stepping 555 and 545. net releases the brushes of the sender control switch to their fifth position terminals. The stepping magnet advances the brushes oi the time measure switch and this switch commences to make a complete rocation.

Following the completion of the impulse series relay 4:00 remains deenergized and relay 220 remains energized. After an interval has elapsed the slow to release relay 219 retracts its armature and completes a circuit from battery through the inner armature and contact of relay 218, winding of the secondary stepping magnet 223, normal contacts of relay 219 to the grounded conductor 231. Stepping magnet 223 operates to move the brushes 225, 226 and 227 on to the terminals of the first trunk of the selected group. Magnet 22?) opens the lockcircuit of relay 218'which becomes deenergized and in turn opens the energizing circuit of said magnet. On the deener ization of the magnet 223 a circuit is completed t .=llcws, assuming the first trunk in the group to be busy at this time and a ground potential to exist on the test terminal 280: battery through the winding of relay 218, lower springs of the normal contact 224, armature and contact of magnet 223, back contact and inner right-hand armature of relay 216. brush 227 to the grounded test terminal 230. It will be noted that relay 216 is included in a circuit in parallel with the one j at raced, but this relay cannot operate as it is shunted by the direct path to ground at the busy test terminal 230. Relay 218 operates and closes the above traced circuit for magnet 223 which in turn operates to advance the brushes to the next set of terminals and also to open the circuit of relay 218. This method of operation continues until an idle trunk is found at which time the shunt is removed from the winding of relay 216 and this relay operates in series with relay 218 The resistance of relay 216, however, such as to prevent the operation of relay 218 and consequently the circuit of the secondary stepping magnet 223 is maintained open and the brushes of the switch are brought to rest on the terminals of the idle trunk. Relay 216 at its inner right-hand ar mature and contact extends the grounded third conductor through tothe test terminal 230 to render the selected trunk busy to other switches. Relay 216 at its left-hand armatures opens the circuit of relay 220 and extends the talking conductors through to the connector switch C. The impulse circuit for operating the connector switch C may now be traced from battery through the right-hand winding of relay 300, contact and outermost left-hand armature of relay d, conductor 326, terminal 229, brush 226, thence over the lower talking conductor through the contact and armature of the stepping relay 400 at the sender and returning over the upper talking conductor to brush 225, terminal 228, conductor 325, normal contact at the outer left-hand armature of relay 305, left-hand winding of relay 300 to ground. Relay 300 becomes energized and closes a circuit from battery through the winding of relay 301, contact and inner right-hand armature of relay 300, contact and innermost right-hand armature of relay 304 to the grounded third conductor 327. Relay 301 locks in a circuit from battery through its winding and contact and innermost right-hand armature, contact andinnermost right-hand armature oi relay 30a to the conductor 327. Relay 300 also completes a circuit from battery tlnough the winding of the slow to release relay 307, front contact and left-hand. armature of relay 300, contact and outermost right-hand armature of relay 305 to ground at the back contact and middle left-hand armature of relay 304.

Operation 0 the connector switch.

Upon reaching the next to its last position the time measure switch T stops temporarily and a circuit is closed from battc *y through the winding of relay r023, conductor 4.39, terminal 580, brush 5411, brush 5&0 (position 5) to ground. Relay ace removes the shunt from around the relay i025 and this latter relay operates in series with the windings oi relay 300 at the connector switch 0. Relay L05 completes a circuit from battery through the winding oi stepping magnet 5 15, conductor 4238, contact and IlglTlZdRiIid armature of relay 405, conductor 437, terminal 578, brush 542, brush 539, and thence to ground at the right-hand armature and contact of relay 552, which operates on the next closure or the interrupter 451. Stepping magnet 545 thereupon advances the time measure switch to its normal position and relay 103 deeuergizes to rec-lose the shunt around the winding of relay 405.

Immediately that the time measure switch reaches its normal pos t on relay is again energized in a circuit o er conductor 579, brush 544, 7 terminal 576, brush 536 (position 5), brush522 ot' the tens register 511 to ground. Relay 556 closes the circuits hereinbetore tracedfor energizing the step ping magnets 555' and 5545. Upon the first closure of the interrupter 4:51 relay 552 encrgizes and closes circuit'f'or relay 553 which in turn completes a circuit for relay 554k as above described. As the interrupter opens the relay 1 energizes in series with relay 553 to the grounded conductor 579. The next time the interrupter 451 closes a circuit is completed as hcreinbetore traced for the stepping relay 400. A circuit is also closed from ground through the rigljithand armature and contact of relay 55 1 outer left-hand armature and contact of relay 552, brush 53? (position 5), winding of the stepping magnet 512 to battery and ground. Magnet 512 energizes preparatory to advancing the brushes ot' the tens register to their next position.

Relay 400 oper tes to ope the imp l circuit thereby causing the energiz tion of the relay 300 at the connector switch C. Relay 300, on deenergizing, completes a circuit from ground through the middle lefthand armature and back contact of relay 304;, outermost right-hand armature and contact of relay 305, left-hand armature and back contact of relay 300 outer le-tthand armature and contact of relay 301, contacts 313 and 315, winding of slow to release relay 302, winding of the stepping magnet 303 to battery and ground, Primary stepping magnet 303 actuates to advance the brushes 318 319 and 320 of the connector switch into operative relation with the first group of terminals. Upon the first primary step of the switch contacts 313 and 315 disengage one another but before this occurs the contact 313 makes engagement with contact 31 1. Consequently, the original energizing circuit of the primary stepping magnet is substituted by a circuit which lead as above traced through the left-hand armatures and contacts of relays 300 and 301, thence by way of contacts 313 and 314., left-hand armature and front contact and winding of the slow to release relay, which is now energized, through the winding of the primary stopping magnet 303 to battery and ground. The next time interrupter 4:51 opens relay 552 deenern'izes and opens the circuits of the stepping magnet 512 and the stepping relay 100. Magnet 512 advances the brushes of the tens register to theirnext position terminals and relay 100 closes the impulse circuit to permit the energization of relay 300. Relay 300 opens the circuit through the slow to release relay 302 and stepping mag net 303. The stopping magnet becomes decnergized but relay 302 retains its armature during the transmission of the impulses. For each succeeding impulse sent out by the register sender stepping magnet 512 opcr t s t ad anc h brushes ne p hile relay 300 operates to cause the primary movem t of t e sel to s i ch 0, Follow- .i e" he ast impul e of the s ries the rush 2 o t egiste .511 1 eng g s he last grounded term nal and opens the circuit 91f encrgized, the slow to release relay 302 retracts its armatures. Relay 30. being slow to release remains energized during the retract-ions of the left-hand armature of re lay 300.

lVhen the time measure switch, which con'imences to rotate upon the Cl@1101"lLi lt-l011 of relay 556, reaches its sixth po ition, brusn. 543 makes engagement with the first one of the connected terminals 531 and a circuit is established as follows: ground through brush 54:3 terminals 531, terminal 532, brush 54:8 contact and armature and winding o l" stepping nuignet to battery and ground. The magnet operates in this circuit to advance the sender control switch from position 6 into position "2. Upon reaching the next to the last position the time measure switch completes a circuit from battery through the winding of mag not 545, the seventh position terminal coacting with l irush 546, brush 5 10 terminal 578, brush 54-2, brush 539, and thence to ground at the right-hand armatme and con tact of relay 552. Magnet 545 ei'iergizes and upon the opening of interrupter 42-51 deenergizes to advance the time nieaeiue switch into its normal position. it will be observed that-the brush54l0 does not close the conductor 4139 to ground in the sixth. and

seventh positions of the sender control switch and consequently relay 21-03 remains deenergized.

When the sender control switch is in po sition 7 and the time measure switch at uorma], a circuit is closed trom battery through the winding of relay 556, conductor 579. brush 544-, terminal 576, brush 536 (position 7), brush 523 of the units register to ground. Relay 550 opera! to close the circuits of stepping magnets 555 and When the interrupter 451 closes relay becomes energized and establishes a circuit for the relay 553 wh ch in turn closes series circuit for itself and relay 554; to the grounded conductor 5. 0. ()n the nextopcuing of the interrupter relay 554: locks in ries with relay Following this the closure of interrupter 151 causes the operation of relay 552 and the above traced circuit is estal lished for the stepping relay 400. also a cir cuit is closed from ground through the ri ht-hand armature and cont 1 554, outer left-hand armature an of relay 52, brush, (P tion 7 COL- L: )9 W h1g oi stepping magnet 51? to battery and lilagnet 517 energizes preparatory u ing the brushes oi? the units regrnetit position and relay 4:00 zit-- aiiuature to open the impulse ciriy causin the rleenergization it t the cc .ector switch, not, upon clcenergisingg, establishes from 7 cl through the middle heel, onta t of rea (l con- I e and t of n outer ieft-iancl relay 301. co

V i e i uture anti contuct 30%" Wk. ow to release re- Winding: the secondary stepping magi", a e09 to battery a cl gz rounch Magnet 30) tes to advance the brushes 318,

l into one ,o sent with the firs terminals in he selectecl groip. lien i also energizes in series n th the stepping magnet and retains its armatures (luring; the tran sion of the units iinpulses. in the manner Well unclcrstootl the relay e00 energizes a d deem- J-ulses over the i misecirits stepping maggs. operated to resto e the unit reg-- 0 its normal position. lWhen the s impi so has been me that the brushes of the i have been (l on to the calling suhscribers line 38th anci *9 to senrl .L terminals brush 52 3 he register the grounder". te n na s and opens the circi. it of )o in turn opens the c1" going magnet and magnet releases ier con 'ol sun :11 out oi.

nto position 8 and magnet J 0t tl ste; brushes of position 7 TL co helices to rot te to l its the time measure "ch ihrc a an. l l fte cyciei Before :ontinning to describe the manner in which the calling; subscribefls line is l preparation made for the am lice.- sing current, the release 0 se will first be taken up and i 1e effect of its release upon the circuits of the group selectoswitch Zielmsc 0f the register sender.

"hen the time its inner armature Relay 4:01 becomes (leaner nects the interrupter Tlmll coiorluctor 401. also completes circuit from battery through the Winding: and ar- L c contact of a brush V on l0) conductor en, contact ant inner right-hand armature o relay 4.101 to ground at the back contact anal outer right-hand armature of relay e06. Magnet interrupts its own circuit and advances the sender control 53" ch into normal position. altll, its outer loft-hand armature, opens the holding circuit of relay 1 and this latter relay becomes (leener- The nia' uiet 409 which also cleeuera at this time arlvances the brushes oi trunk fincler TF to their next tern1iinh finder 'llll is now restored to position by means of a circuit through the Win '1 and aran l contact O'l' magnet 409 through conn cted te .e iinals with which brush cooperates, terminal 145, brush 415 to il hc-n the trui'ik finder Tl! reaches normal brush 422 engages terminal 446 and a circuit is completecl from battery through the wire of relay 40?, terminal 146 i l and brush 4:15 to operates and closes a i hatter through the Winding armature and contact oi magnet 4'08, 2 outer righuhanfl armature oi tact .u'l outcri'nost left-hand cl )6 J n, coi armature ot- 4:16 brush 423 at. ininal to grouml. crate in this circuit brushes the trunk normal position, The

Ma l 7 terminal {452, brush 0. i s normal position ter- Stepping magnet e108 op anc. advances the finder TF to their trunk finder switches remain inrclive and relay 4.0? is reat the time moves into posin," v fnmr A un 0. .ouc cit impulse comluctors s Saul talking; con- ,e ul Wind- "lef co troa on (l jenerg'iz' l;

onuects is to i il 10% in the trunl i its cute" left-hand pens the circuit 0:? I at its rinost right 11 u I pens the circui, torllashing the lamp 121. The termination of the flash mg of lamp 121. indicates to the operator direction as to prevent the energization of the polarized relay 105. Relay 110 completes a circuit from ground through its armature and contact and the winding of relay 1141 to battery and ground. Relay 114: becomes energized and a circuit is established from battery through the winding of relay 113, armature and contact of relay 116, iront contact and left-hand armature of relay 11 1 to ground. Relay 113 operates and closes a circuit from ground through its right-hand armature and contact, winding of relay 117 to battery and ground. Relay 117 locks in a circuit from battery through its winding and front contact and inner lefthand armature, contact and outermost righthand armature of relay 120 to ground at the contact and outermost left-hand armature of r lay 124. Relay 117 also opens the operating circuit of relay 116 and this latter relay releases its armature. After relay 116, which is made slow to release, retracts its armature, relay 113 deenergizes and closes the trunk circuit at its left -hand armature and contact. Relay 117 also opens the circuit of lamp 118.

During th energization of relay 113 the upper talking conduct is opened for a sufficient interval to permit the release of relay 305at the connector switch. Relay 305, on

retracting its armaturcs, completes a circuit from the ringing source interrupter 329, left-hand winding and back contact and in- 'er left-hand armature of relay 305, contact and outermost right-hand armature of relay 301, outer right-hand armature and con tact of relay 311, brush 319, thence over the loop of the calling suhscribers line, brush 313, back contact and inner right-hand armature of relay 311, middle right-hand armati "7% and contact of relay 304 to ground at the outer left-hand armature and contact of relay 305. Relay 305, being marginal. does not operate in series with the high resistance of the ringer magnet at the substation 330. l/Vhcn the calling subscriber removes his receiver from the switch hook, relay 305, being included in a low resistance circuit, attracts its armatures and locks up in a circuit an battery through the right-hand winding and contact and innermost right-hand armature of said relay, normal contacts of relay 307. conductor 325, and thence over the upper side of the talking circuit to sand at the upper right-hand winding of reneatin coil this circuit having been :mp in the meantime by the release'of relay 11.3. The ringing current is thus disconnected froin the callii'ig subscribers line. iuce the calling subscribers receiver is off the switch hook and the left-hand armatures of relay 305 are attracted the relay 306 is now included in a direct circuit from the callin subscrihers substation through to the right-hand windings of the repeating coil 109 and the battery supply relay 112. Relay 306 becomes energized and closes a circuit for relay 307. Relay 307 at its make before break contact shifts the holding circuit for relay 305 from the upper talking conductor to the third conductor 327. This circuit may be traced from battery through the right-hand winding and contact and inner'right-hand armature of relay 305, front contact and right-hand armature of: relay 307 to conductor 327. The relay 112, which also energizes in series with the calling subscribers line, close a circuit from battery through the winding of relay 111. contact and armature of relay 112 to ground at the contact and armature of relay 110. 111, at its armatures and contacts, reverses the connection of the windings of relay 110 to the talking conductors 107, 108. This re versal of current causes the polarized relay 105 at the toll operators position to retract its armatures. Relay 105 removes the shunt from around the high resistance winding of relay 106, whereupon the flow of current is reduced through the winding of relay 102. Relay 102 thereupon deenergizes and opens the illuminating circuit of lamp 103 which advises the toll connecting operator that the calling subscriber has removed his receiver from the switch hook. The calling and called subscribers may now converse with one another over the toll connection.

Release 0; the :stablished connection.

When the conversation has terminated the calling subscriber line 611, by replacing his receiver to the switch hook, causes the ac tuation of the usual supervisory signal at the toll connecting opcrators position, Lil-rewise, the replacement of the calling subscribers receiver to the switch hook cause the deenergization of relay 112, which in turn permits the deenergization of relay 111. Relay 11.1 again reverses the current over the trunk 107, 108 and the polarized relay 105 releases its armature to recluse the shunt around the right-hand winding oi relay 106. Relay 102 now operates and lamp 103 illuminates to notify the toll connecting operator that the connection should be taken down. She thereupon removes the plug 100 from the jack 101 causing the deenergz ization of relays 102 and 106. Belay 106 opens the circuit of relay 110, which latter relay rcleases its armatures and opens t ic circuit oi relay 114. Relay 11 1 completes circuit from battery through the lamp 118, ini'ier right-hand armature and front contact of relay 1.17 innermost right-hand armature and contact of'relay 114, interrupter 115 to ground The interrupter 115 causes the ai't'zp to flash. indicating; to the cordless operator that the switches should be released.

The cordless operator thereupon depresses her disconnect key 127 which removes ground potential from the. conductor 130. n The removal of this ground potential causes the release of relays 207, 216, 217, 3041 and 305. Relay 207 completes a circuit from battery through the winding of release magnet 204, middle springs of the off normal contact 211, back contact and armature of relay 201, back contact and armature of relay 200, contact and outer right-hand armature of relay 207 to ground. to restore the brushes of the selector switch S to their normal position. circuit is completed from battery through the winding of release magnet 222, upper, contacts 221, back contact and left-hand ar mature of relay 21?, contact and left-hand armature of relay 220 to groiiind at the.con-- tact and outer. liglltdlal ld armature'ot' relay 216. Magnet 222 also operates to restore the brushes of the selector switch S The release of relay 304 at the connector switch establishes a circuit from battery through the winding of the release magnet 308, con -v tacts 317 and 316, back contact and middle right-hand armature of relay 301, back contact and middle left-hand armature of relay 30a to ground. The release magnet 308 energizes and causes the release of. the brush shaft of the connector switch C. All apparatus taken in connection with the es.- tablishment of the toll connection has now been completely returned to its normal condition.

Calling subscrbers Zine busy.

ltwill next. be considered that the calling subscribers line 330 has been, rendered busy during the time that the toll connection is being obtained by the toll operator. Consequently. the test brush 320 of the connector switch C on engaging: the test terminal 321 of the calling subscribers line at the termination of units selection encounters a ground potential thereon. A circuit is there upon established from battery through the winding of relay 311, front contact and right-hand armature of relay 32 1, test brush 320 to the grounded test terminal 821, Relay 311 operates and locks up in a circuit as follows immediately that the slow. to release relay 3241 retracts its armatures: battery through the winding of relay 311;. make before break contacts at the right-hand armature o't relay 32 1-. back contact and righthand armature o-t rela 310, contact and outermost left-hand ari .ure of relay 311 to the grounded conductor 32?. Upon the next closure of the constantly rotating inter-- rupter 323, -following the deenergization of relay 3241. a circuit is closed from ground through the left-hand winding of coil 322, interrupter inner left-hand ari'i'iature ano contact of relay 32 1-, contact and middle eft-hand arniiature of relay 311, outeri'i'iost right-hand armature and front contact of The release magnet 204.- operates,

Similarly, a

relay 301, left-hand winding of relay 304 to battery and ground. Relay 30 1 operates and locks in a circuit through its left-hand winding to the grounded conductor 327 and relay s04 opens the holding circuit of relay 301. For each succeeding closure of the interrupter 323 a circuit is established over the above traced path to the outermost righthand armature and back contact of relay 301, right-hand winding; of relay 300 to battery and ground.

When the toll operator has succeeded in obtaining the called party she depresses the key 138, as hereinbetore explained, and the relay 113 is caused to attract its armature to open the upper talking conductor. The opening, of this circuit causes the deenergization of relay 30:), as explained. Although relay 305 retracts its arinatures it cannot apply ringing current to the calling subscribers line due to the fact that relay 311 is holding the ringing circuitopen at Its right-hand armatures. For each opening and closure of the interrupter 323, a current is induced in the h --hand winding of relay 300 which llows over the non al contacts at the outer lefthand armature of relay 305 over the upper talking conductor to the repeating coil 109, The repeating coil 109 induces the current which is in turn transmitted over the trunk 107, 108 to the toll operators telephone receiver. The characteristic sound produced in the toll operas tors receiver notifies her that the calling discussed. The cordless operator canes the release of the switches S S and C.

The toll operator immediately connects her telephone set to the order wire 010 and asks the cordless operator to set up the same connection to the calling subscribei"s line and this time to providefor seizing said line regardless of its busy condition. The cordless operator thereupon depresses the keys on her board in the manner. previously explained and also actuates the no test key 583. The key 583 completes a circuit from ground through its contacts, upper righthand contact 455 (1) of the allotter switch AL, conductor 586, winding; of relay 58a to battery and ground. Relay 58 1 locks up on the following circuit as soon as the relay 401 has become energized following the completion of the operation 01? the trunk finder switches: battery through the winding and right-hand armature and contact of relay 58 1, conductor 44:0 to ground at the outer left-hand armature and contact of relay 401. The first and second selector switches H ll

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