US1238160A - Telephone system. - Google Patents

Description

A. E. L UNDELL.

TELEPHONE SYSTEM APPLICATION FlLED Aue.26. 1916. P t t d A 28 1917 //7 l/en for A/bem E. Luna/e A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FILED AUG.26.1916.

Patented Aug. 28, 1917.

6 SHEETSSHEET 2.

//1ve/170 A/hen E. Lunde/K A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FIALED AUG.26, 1916,

Patented Aug. 28, 1917.

A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FILED AUG.26. i9l6.

Patented Aug. 28, 1917.

s SHEETS-SHEET s.

fnvemfor: A Men E. Luna/e A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FILED AUG.26. 1916.

SHEET 6.

Patented A11 6 SHEETS 53 mm QR i i TED srA'rs 'ALBEN E. LUNDELL, on NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, on NEW YORK, N. Y., A CORPORATION or NE YORK.

I is

To all whom it may concern:

TELEPHONE SYSTEM.

Systems, of which the following is a full,

clear, concise, and exact description.

The present invention relates generally to telephone systems of the semi-automatlc or semi-mechanical class in which operators use manual equipment in establishing portions of the connections between telephone lines, and automatic switch mechanism is employed in establishing other portions of such connections or in bringing the opera; tors into communication with the subscribers or each other.

More particularly, the invention has to do with systems in which the automatic switch mechanisms place an operator, sometimes called a tandem operator, intocommunication with an operator at a distant exchange and in which the designation of the called line is automatically indicated to the tandem operator and then read off.

by her to the distant operator.

The principal object of the invention is to simplify the work, of the operators. In so doing the number-roof indications to be read off by the tandem operator is reduced, as compared with prior art systems, and the required manual operations of the terminat' ing operator are lessened. In prior systems of the art, upon which the present invention is an improvement, an arrangement of circuits and keys was employed by which the tandem operator could connect to a number of terminating operators equipments. By the present invention these keys and their circuits are done away with. Furthermore, with these prior, art systems it was necessary to employ annunciators to indicate more designations than-is required by the present invention. Inthe present case the automatic switch mechanisms perform certain of the functions which were formerly performed by the operators. The

automatic switches now pick .out the trunks instead of the terminating operator doing so, as was the case in the prior art systems and they perform the functions formerly performed by the keys.

The various aspects and features of my invention will be more fully understoodby Specification of Letters Patent. Patented Au Application filed August 26, 1916. Serial No. 116,993.

reference to the following detailed description taken in connection with the accompanying drawing andthe scope of the invention will be more particularly pointed out in the appended claims.

In said drawings I have illustrated the present invention by a diagram in six figures placed together in the manner indi cated in Figure l.

a In the system herein disclosed, which is merely typical, three operators are required to establish a connection between subscribers lines. Thefirst, or initiating operator,

ATEN FFLE.

answers the call of the subscriber and by a suitable sender causes thecalling line circuit to be extended to' a tandem operator. At the same time an'indication corresponding to the called 'line is displayed before the tandem operator and her telephone set is automaticallyconnected to an automatically selected order wire or trunk running to a terminating operators equipment at the desired distant exchange. The terminating operator, when brought into communication with the tandem operator, designates a trunk to which the tandem operator connects the extended calling line circuit. At this time the tandem operator reads off the displayed indication to the terminating operator and the latter completes the connection to thecalled line. As soon as the tandem operator connects the calling line circuit to the designated trunk, the automatic switching mechanism employed in bringing the .tandem operators equipment into circuit with theinitiating operators sender, in displaying the called line designation and. in connecting the tandem operators head-set into circuit with that of the required distant operator, is freed for further use in establishing other connecting circuits between calling and called lines. At the conclusion of conversation between the sponse to suitable supervisory indications.

Entering upon the description of the diagram somewhat more in detail, it will be seen that the subscribers'equipment at sub I station M is connected by line L to a central office or exchange where the line terminates in contacts of a jack J and is provided with the usual line relay LR, line lamp LL and loo ' cu't-ofi' relayi CO. The jack J is available to the initiating operator who extends the line circuit by means of the plug P whose contacts are connected by the strands of a trunk or link circuit L to the Wipers of an automatic switch S. A second trunk or link circuit Lt extends from the bank contacts of switch Sthrough the contacts of a plug P lar to those of the line L extending from lamps L, L, I]

substation M. The conversational circuit established by extending the calling line circuitis indicated by heavy lines in Figs. 1, 2 and 3 of 'the diagram. The initiating op erator, that is, the operator who has control of the plug P, is provided with a sender SN which is operable to control the switch S" over the strands of link circuit If and sub-.

sequently to bring about the proper operation of the line finder S and either of the final switches S or S as the case may be, and then to display the proper indicating L", L", L, and L of the annunciator mechanism which is before the tandem operator, that is, the operator having control of plug P The'sender- SN may -be of any approved construction although preferably it is a key-board sender .of the type shown in Lundell Patent No. 1,168,319, dated January 18, 1916. I 4

The automatic switch S- may also be of any approved type. It is here shown diagrammatically as comprising aset of wipers and associated bank contacts. United States Patent No. 1,103,623, granted July 14, 1914, to Reynolds, illustrates a switch of the type which is preferalbly used to perform the functions of the switch S of the diagram,

The automatic line finding switch S is also a switch of the type shown in said Reynolds patent and is shown in diagram as a set of wipers in association with bank contacts, the wipers being mounted upon a shaft 10 which is driven in'one direction by a constantly rotating disk 11 and in the opposite direction by a constantly rotating disk 12. The disks are brought into play in the one case by the energization of an advancing magnet AM and in the other case by the energization of a restoring magnet RM. In each instance the magnet by its associated arm brings the lower flattened portion of the shaft 10 into frictional engagement with the disks to brin about the proper movement of the shaft; I his switch is also provided with a commutator 13 which is employed in varyingthe circuits in the operation of the switch and its associated mechanism.

The automatic switch S is preferably a switch of the rotary type, like that illustrated in United States Patent No. 1,146,583, granted July 13, 1915 to RR. McBerty. In brief, the s witch comprises a shaft 14 which is connected to a flexible magnetic disk 15 which may be drawn into frictional engagement with a-constantly rotating disk 16 in response-to the energization of the magnet 17 The shaft 14 carries springs 18, 19 and 20 through which circuit is extended to bank contacts 21, 22 and23. These springs do not engage the bankcontacts, but connection with the latter is brought about by brushes 24, 25 and 26 mounted on a vertical spindle 27 and engaged by the springs 18, 19 and 20, respectively. These brushes are tripped into engaging position by a series of projections of which two, designated 28 and 29, are shown. These projections are mounted upon a verticaLshaft 30 and are in spiral relation so as to bring about a tripping of the properset of brushes in accord- "ance with the rotary position of the shaft 30. This rotary position of the shaft is determined by bringing constantly rotating disk "31 into engagement with disk 32 upon the shaft 30 and maintaining the frictional engaging relation until the desired position of the shaft 30 is reached; This frictional engagement between the disks 31 and 32 is brought about by the energization of magnet 33. The magnet 34 associated with the disk 15 is a'braking magnet intended to bring about a speedy stopping of the disk when the desired point isreached, In addition to these parts the switch includes impulse contacts 34, 35 and 36, 37, which are operated by dogs 38 and 39 upon the shaft 27 and having operative relation with the notched racks 40 and 41.

The automatic switch S is similar in constructionto the switch S and therefore need not be described in detail. I

It may l e pointed out at this point that-in the subsequent description of the operation of the system, if any references are made to the parts of switch S those parts will be given designating characters similar to those of switch S but followed by the letter a.

The annunciator illustrated in diagram In Fig. 6 consists of aseries of lamps for ear i1 of the different designations that go to make up the complete designation of the called line. In the instance illustrated the lamp 'L is one of a series of lamps for the thouhundreds digit of the called line. Similarly the lamp L is 'one of a series of lamps for indicating the tens digit of the called line. Again the lamp L is one of a series for indicatingthe units digit of the called line.

indicator are displayed the designation of v the calledline maybe readily read off by the tandem operator. Thus, if the number were 1234., that number would be read off from the first lamp of the thousands series,

the second lamp of the hundreds series, the

third lamp of the tens series and the fourth lamp of the units series. Furthermore, if the party to be signaled was the fourth party on a party line, then the fourth lamp of the party line series would be displayed. This annunciator'mechanism is of the type disclosed in United States Patent No. 1,117,511, granted November 17, 191 1 to F. R. McBerty. i

In the operation of the system many of the circuit changes are brought about by simple rotary switches termed sequence switches. The structure of these sequence switches includes in each instance a rotatable shaft having a series of disks of fiber or other insulating material secured thereto. On each side of each insulating disk is a circular conducting plate which is cut away or skeletonized so as to provide any desired arrangement of contacts. The plates on the opposite sides of the disk are electrically united by securing rivets. The rotatable disks are represented in the drawing in each instance by a long contact. A plurality of springs or brushes is provided for engagement with each pair. of conducting disks and by means of these and by properly cutting away and arranging the plates on the insulating disks, any two or.more' brushes arranged for engagement with a disk may be electrically united at any stage of rotation of the shaft. In each instance, the positions of the sequence switch at which the various springs or brushes are in engagement with the rotatable disk are indicated by numerals placed adjacent to the long contacts of the diagram. Thus, in the case of sequence switch SS of Fig. 2 of the diagram, the shaft upon which the disks are mounted is designated 42 and the disks are designated 43 to (31, inclusive. All of these except the last make contact in the positions indicated by the numerals adjacent to them. In the case of the last contact, namely 61, which is shown with a projection on its upper face, the circuit is closed at all points between the positions indicated by the numerals adjacent to it and the circuit is open at those positions. It may be here pointed out that when in the subsequent description of the operation of the system a circuit is traced through the contacts of a sequence switch, the designating numeral 1 of the disk will be used followed by the number" of the position of the switch at Which the contact is made, the latter being in parentheses. Thus, withthe switch SS inthe seventh position, a circuit through contact 56 would be indicated by 56 (7). The structure of the sequence switch is such that the shaft, as shaft 42. of switch SS, is driven from a constantly rotating shaft, as- 61 through magnetic clutch disks, as

61 and 62, which arebrought into clutching engagement by the switch magnet, as SM. This same arrangement of disks nd shaft is employed in. each of the sequence switches and need not be further described. For convenience, however, the magnets of each of the sequence switches will be designated.

On Fig. 4 of the diagram three sequence switches SS SS and SS are shown. Switch SS has an actuating magnet SM and contacts 63- to 82, inclusive. The latter is a maintaining contact like the contact 61 of switch SS. The sequence switch SS has an actuating magnet SM and contacts 83 to '87, inclusive. This switch has for its function the allotting of the lamps oflthe annunciator to the different finder switch circuits and the same has been termed in the diagram lamp allotter. The sequence switch SS has an actuating magnet SM and contacts 88, 89 and 90, of which the last is a maintaining contact. This switch also performs an allotting function. It allots or sets in waiting position the mechanism of the different cord finding circuits. The sequence switch SS is shown in Fig. 5 of the diagram. It is provided with an actuating magnet SM and contacts 91 to 102, in-

elusive, of which the last is a maintaining contact.

The sequence switches which control the annunciator circuits are shown in Fig. 60f the diagram. Of these, the switch SS is provided with an actuating magnet SM and contacts 103 to 111, inclusive; switch SS, with an actuating magnet SM and contacts 112 to 118, inclusive; switch SS with an actuating magnet SM and contacts '119 to 127, inclusive; switch SS with an terminating operators head-set TO (Fig. 3), the trunk wires 152 and 153 extending from the set TO to the moving contacts of the automatic switches S or S ,-as the case may be, and the trunk wires 154 and 155 extending from the bank! contacts of one of the latter switches to the set T. In the instance illustrated these trunk wires 154 and 155 extend from the switch S With this brief description of the principal portions of the diagram we may pass on to a description of its Operation when putting through a call from substation M to substation N and in so doing the circuit connections and other portions of the apparatus will be more fully described.

If the party at substation M initiates a call by removing his receiver from its hook,

v a circuit will be closed for the line relay LR.

This circuit may betraced from the live pole of the battery 156 through the left hand winding of relay LR, normal contact 157 ofcut-ofi? relay CO, over one limb of the line L, through the substation M, back over the other limb of the line L, through'normal contact 158 of cut-ofl? relay CO and the right-hand winding of relay LR to ground. The resulting energization of relay LR will close its contact 159 and thereby complete a circuit for line lamp LL from battery 160. Upon observing the lighting of lamp LL, the initiating operator, namely, the one having control of plug P, will insertsaid plug into ack J and close a circuit for cut-oil relay CO. r This circuit maybe traced from the-live pole of battery 161 through protective. resistance 162, plug and jack local contacts and the winding of cut-ofi relay CO to ground. The energization of relay CO disconnects relay 'LR from the line and thereby dee'nergizes it and causes the circuit of lamp LL to be opened with a consequent extinguishmentof thelamp. Upon the insertion of the plug P into jack J, the 4 tip and sleeve contacts connect the tip and sleeve strands of the line L and link circuit L. As a' result of this connection, transmission current is supplied from battery 163 through the windings 164 and 165 of a repeating coil to the opposite strands of the link circuit L and thence over the line L to the transmitter of the substation M. The initiating operator is provided with the usual operators set and by means of it and a suitable listening key, (neither set nor key being shown) connects into the circuit of the calling line and obtains the order from the calling party in the'usual way. As soon as the number of the called line is learned the operator proceeds to manipulate the sender SN. Where the preferred type of sender is employed, she sets up the number of the called party upon the sender and sets it going to operate the other mechanisms to bring about an extension of the calling cirnaaeaeo cuit to the called line. Before this is done the contacts 166- and 167 are moved into circuit engagement with the conductors 168 and 169 by any suitable mechanism. Ordinarily this operation will be brought about by a sequence switch associated with this part of the circuit. For the purposes of the present disclosure, however, it may be assumed to be performed by any suitable mechanism, or, if desired, by hand. The first effect of the operation of the sender SN is to cause the automatic switch S to pick out an idle trunk L extending to the desired distant ofiice. In this switch structure the third wiper 170 and set of bank contacts 171 are used for test purposes in bringing about the. proper selection. This switch structure and its operation is well known and for the purposes of the present disbe traced from the live pole of battery 17 2 through sequence contact 50 (1 to 3), the

, winding ofcontrol relay OR, sequence contact 47 (1 to 2),protective resistance 173, tip strand of link circuit L tip strand of link circuit'L conductor 168, closed contact 174' of the sender SN, the winding of magnet 175 of :the sender, conductor 169, contact 167,-

sleeve strands of link circuits L and L respectively, protective resistance 17 6., sequence contact 59(1 to 3) to ground. The closing of this circuit energizes relay CR and establishes a starting circuit for sequence switch SS. This starting circuit may be traced from the live pole of battery 177 through the winding of magnet SM, sequence contact 56 (1) and alternate contact 178 of relay OR to ground. The energization of magnet SM causes the sequence switch to Vance from the first to the second positio Its starting circuit is thereby broken at sequence contact 56 (1), but during its passage from one position to the other, the circuit ofmagnet SM is maintained through sequence contact 61, as before explained. .In consequence, the switch SS makes one complete step or advance from its initial position to its second position, and cannot be left .at an intermediate point. The advance of this sequence switch to its second position places ground at 59 upon the starting wire 179 and upon the hunting or test wire 180 of the line finder S The placing of ground upon starting wire 17 9 completes a circuit for advancing relay AR which may be traced from the live pole of battery 181 through the fwindingof relay AR, sequence contact 64 (1 to 12), sequence contact 64 (1 to 1%) conductor 179 and sequence contact 59 (2) to ground. The closing of this circuit enernate contact 182 to ground. As a result,

sequence switch SS advances from position 1 to position 2. In this case a complete advance is brought about by the maintaining circuit through sequence contact 82 as heretofore described in connection with the switch SS. This advance of switch SS opens its starting circuit at sequence contact 69 (1) and in consequence it takes only one advance step. At sequence contact 66 (2) a circuit is completed for advancing magnet AM of the cord finder S circuit may be traced from the live pole of battery 184 through the winding of magnet All/l, sequence contact 66 (2) and alternate contact 182 of relay AR to ound. Although the advance of switch 1 to position 2 has opened the initial starting circuit through wire 179 at sequence contact 64 (1 to 1%), [ct a maintaining circuit for relay AR is provided through closed contact 185, conductor 186, sequence contact 74 (1 to 2), conductor 187, commutator bar 188 and brush 189 to ground. This circuit is maintained until the switch S makes a complete step, whereupon brush 189 rests upon an insulating segment and-interrupts the maintaining circuit. In the meantime, however, an alternate maintaining circuit is provided for relay AR through sequence contact 64 (1 to 12), sequence contact 64 (1% to 2) and normal contact 190to ground. This latter contact is controlled by test relay TR which is brought into circuit with the test wiper 191 of switch S as soon as sequence switch SS moves to its second position. The test relay TR remains denergized until the test -wiper 191 engages a test contact 192 whose test wire 180 is connected to ground. As soon as such a contact is encountered, a circuit will be established for test relay TR which may be traced from the live pole of battery 193 through the winding of relay TR, sequence contact 65. (2 to 12), sequence contact (2 to 3), sequence contact 63 (2 to 3), test wiper 191, test contact 192, conductor 180 and sequence contact 59 (2) 130 ground. As a result of the energization of test relay TR by the closing of this circuit, its normal contact 190 is broken and the maintaining circuit for AB is thereby in terrupted. As a consequence the circuit for advancing magnet AM is interrupted at contact 182 and the further advance of the switch S is discontinued. By reason of the position oi the insulating segments in association withthe commutator contact strip 188, an accurate full step of the switch is The complete secured in every instance. When the switch S is thus stopped, pawl 194 associated with the armature of return magnet BM drops into a notch in the lower portion of shaft 10 and holds the switch S in its desired advanced position. As soon as relay TR is energized, by reason of the test wiper 191 finding a grounded contact, it is maintained energized by a locking circuit extending from battery 193, sequence switch contact 65 1(2 to 12) sequence switch contact 65 (2 to 3) and through alternate contact 190 to ground.

As soon as relay AR became denergized as a result of the energization of test relay TR, a circuit for sequence switch SS was established. This circuit may be traced from the livepole of battery 183 through the winding of magnet SM, sequence contact 67- (2) and normal contact 182 to ground. In consequence of the closing of this circuit SS advances from position 2 to position 3. The starting circuit is broken at sequence contact 67 (2). The closing of sequence contacts 63 (3),65 (2 to 3) and 65 establishes a starting circuit for sequence switchSS which may be traced from the live pole of battery 177 through the winding of magnet SM, sequence contact 58 (2 to 3), sequence contact 58 (2), conductor 195, bank contact 196 of switch S wiper 197 of the same switch, sequence contact 65 (3), sequence contact 65 (2 to 3), sequence contact 63 (2 to 3), test wiper 191, test contact 192, conductor 180 and sequence contact 59 (2) to ground. As aresultfsequence switch SSad- 'vances to its third position, the starting circuit being broken at sequence contact 58 (2). As a result of this advance of switch SS to position 3, relay AR is energized to bring about an advance of sequence switch SS to position 4. The circuit for relay AR which is thus established extends from the live pole of battery18l through the winding of relay AR, sequence contact 64 (1 to 12), sequence contact 64 (3 to 15), wiper 198 of switch S bank contact 199 of the-same switch, conductor 200, sequence contact 51 (3 to 5), sequence contact 51 and alternate contact 178 to ground. It may be here pointed out that, whereas relay OR was initially energized over the circuit through the sender SN and included sequence contact 47 (1 to 2), just as soon as sequence switch SS moved to its second position an alternate path for relay CR was established by way of sequence contact 47 (2 to 3), closed contact 201 of relay CR, sequence contact 43 (2 to 3) and sequence contact 43 (2 to 3), through protective resistance 173 to the tip strand of link circuit L in parallel to the initial path through sequence contact 47 (1 to 2). Consequently, at this time contact 178 is in its alternate position and relay AB is energized by the closing of the circuit just traced. The energization of relay AR completes a starting circuit for sequence switch SS which may be traced from the live pole of battery 183 through sequence contact 69 (18 to 3), sequence contact .69 (3) and alter- 1 nate contact 182, to ground. As a result, switch SS is advanced to its fourth pos1 tion and the initial starting circuit is inter-1 rupted at sequence contact 69 (3). As soon as switch SS moves to its fourth position a circuit is completed for sequence switch SS (Fig. 5). This circuit may be traced from the live pole of battery 202 through the winding of magnet SM, conductor 203, msie quence contact 74 (4), conductor, 186, 15 c' osed contact 185, and thence to ground at alternate contact 178 of relay CR over the pathpreviously'traced as part of the energizing circuit of relay AR. For convenience, this path may be again traced through sequence contact 64 (1 to 12), se-

' magnet 175 of the sender SN. It will be remembered that the circuit through control relay CR and the magnet 175 of the sender, extends through sequence contact 47 (2 to 3), closed contact 201, sequence contact 43 (2 to 3), sequence contact 43 (2 t0 3) pro-' tective resistance 173, over the tip strands of the link circuits L L through the sender magnet 175 and back over the sleeve strands of said link circuits to ground at sequence contact 59 (1 to 3). branch by which the sender magnet 175 is short-circuited, extends from sequence contact 43 (2 to 3) over impulse wire 206, bank contact 207 of cord finder S wiper 208 of the same-switch, conductor 205, closed se quence contact 94, conductor 204, sequence contact 66 (3% to 12) and alternate contact 182 of relay AR to ground. As before explained, this ground connection is but momentary. At the instant of its establishment the sender magnet 175 is deenergized and if the sender is set so asto cause the sequence switch SS to make but a single advance step, then immediately contact 174 of the sender is opened and in consequence thereof control relay OR is deenergized and the path to ground through alternate contact 178 is broken and both relay AR and sequence magnet S are denergized.

If the sender is set so as to allow further advances of the sequence switch SS*, then the latter proceeds to advance, each time momentarily closing the connection to The circuit ground andcausing the sender magnet 178 to be de'nergized as. before. ,In the present case, thesender SN will not cause the sequence switch SS to advance more than four steps, that is to say, farther than to its third position. This is because there are but four groups of trunks 154, 155, to which the tandem operators set TO may be con-' nected. If we assume that the sender has been set so as to cause sequence switch SS to move only one step, that is to say, to its zero position, then we-will find that relays CR and AR and sequence magnet SM are denergized in the manner just explained. The movement of sequence switch SS to its zero position connects the order wires 152 and 153 through sequence contacts 95 (0 to 1) and 96 (0 to 1),to the wipers 24 and 25, r'espectively, of switch S It will be seen that if the switch SS had moved to a second or third position in resp se to a different setting of the sender bl, then the wires 152 and 153 would have been extended via sequence contacts95 (2 to 3) and 96 (2 t0 3) and conductors 209 and 210 to the wipers 24 and 25 of switch S Thus the op eration of the switch SS in response to the setting of the sender SN picks out the particular final switch that is to be brought into circuit and thereby performs the first step in determining the group of conductors 154 and 155 which are to be brought into circuit. switch S it remains for subsequent opera tions to cause that switch to pick out contacts 21 and 22 of the desired group of conductors 154 and 155. In the type of switch shown, the next selection, which is commonly called brush selection, is brought about by the' projections upon the shaft 30 which is rotated in response to the energization of the magnet 33. Impulses for the operation of this magnet come through sequence contact 98 (O to 1). It will be seen that if the switch Si had been selected then the impulse for operatingv magnet 33 of that switch would have assed through sequen'cecontact 98 (2 to In order to establish a circuit for the brush selection, that is tosay, a circuit for the magnet 33, there must have first been an operation of sequence switch SS to move it from its fourth position to its fifth Having picked out the particular position. This starting circuit is provided at the time that relays CR and AR and magnet SM are denergized by reason of the breaking down of the fundamental cir-' cuit in response to the opening of sender contact 174, as before explained. Upon the breaking down of such circuit, relay AB is denergized and a starting circuit for magnet SM is established. This circuit may be traced from the live pole of battery 183 through the winding of magnet SM, sequence contact 68 (4). conductor 211, se-

quence contact 92(0 to 16), conductor 212,

normal contact 213 of relay 214, conductor 215, normal contact 216 of relay 217, conductor 218, sequence contacts 108 (N), (N), 124 (N), 132- (N), 140 (N), 148 (N), conductor 219, sequence contact 79 (4 to 12), conductor 220, and normal contact 182 of relay AR to ground. As a result of the closing of this circuit, switch SS moves to its fifth position. As soon as this occurs, relay CR, relay AR and brush selecting magnet 33 are energized. The circuit by which relay GR is energized extends from the live pole of battery 172 through sequence contact 50 (1 to 3), the winding of relay CR, sequence contact 47 (2 to 3), se-

quence contact 45 (2 to 3), sequence contact 45 (2 to 3), conductor 221, bank contact 222 of switch S wiper 223 of the same switch, conductor 224, sequence contact 78 (5), conductor 225, sequence contact 93 (0 to 16), conductor 226, normal contact 227 of relay 214, conductor 228, normal contact 229 of relay 217, conductor 230, sequence contacts 109 (N), 116 (N), 125 (N), 133 (N), 141 (N), 149 (N), conductor 205,

wiper 208 of switch S bank, contact 207,

conductor 206, sequence contact 3), sequence contact 43 tive resistance 173, and thence, as before, over the tip side of the link circuits L, L through the sender magnet 175 and back over the sleeve side of the circuits L, L

and through protective resistance 176 and sequence-contact 59(1 to 3) to ground. The energizing circuit forrelay AR is established as before'when alternate contact 178 of relay GR is closed. The energizing circuit for the brush selecting magnet 33- of switch S extends from the live pole 011mtery 231 through the winding of magnet 33, sequence contact 98 (0 to 1), conductor 232,

sequence contact 74 (5), conductor 186,: AR, and thence,

closed contact 185 of relay over the path to ground at alternate contact 178 of relay CR as before traced. As a result of the closing of these circuits for relays CR and AR and magnet 33, they and the sender magnet 175 are energized. The energization of magnet 175 operates the sender one step and the energization of magnet 33 advances the shaft 30. As the latter advances, it actuates lever 233 toclose circuit at points 234 and 235 between conductors 236 and 237, thereby connecting impulse wire 205 to ground through wire 204, sequence contact 66 (31; to-12) and alternate contact 182 of relay AR. The grounding of the impulse wire in this way causes magnet 175 of the sender SN to be dee'nergized.

Thus, as the brush trippingtshaft 30nd.

vances step by step, sender magnet 1751s denergized in response to the repeated mo mentary closings of the short-circuitingpath until shaft 30 has advanced to a position (2 to 3), protec-- (N), conductor to 12), conductor ,tact 59 (1 to 3).

as a result of closing this circuit, closes "the circuit for relay AR which extends, as

into the path of the Wipers or brushes 24 and 25, which are to be used in extending the circuit of the order Wires 152 and153.

' The next operation is to bring about an advance of the wipers of the switch S Before this advance can take place, sequence switch SS must advance to position six. It may be here pointed out that the-switch S is-provided with off- normal contacts 238, 239 and 240. As soon as the shaft 30 moves from its normal position, contacts 238 and 239 are opened and contacts 239 and 240 are closed. The. closing of the latter contacts completes a circuit for relay 214 which may be traced from the live pole of battery 241 through the winding of relay 214, conductor 242 and closed 240 and 239 to ground. relay 214 brings about a change of connections WlllCll'lIlSlllGS a'circuitfor the control relay CR at this stage of the operation. Before such circuit is established, however, switch SS must be advanced' The circuit for advancing switch SS may be'traced from the live pole of battery 183 through sequence contact 68 (5), conductor 243, alternatecontact 213, normal ductor 218, sequence contacts 108 (N), 115 (N), 124 (N), 132 (N) 140 (N) and 148 219, sequence contact 79 (4 220, and normal contact 182 toground. As a result of this move ment of sequence switch SS to the sixth position, relays CR and AR and Wiper actuating magnet 17 are energized. Theenergizing circuit for relay CR extends from the off-normal contacts The energizatlon of live pole of battery 172 through sequence contact 216, consistance 173, tip strands of link circuits L and L the winding of sender magnet 175, sleeve strands of link circuits L and L protective resistance 176, and sequence con- The energizing of relay before traced, to ground at alternate contact 178 of relay CR. The closing of contact 185 of relay AR brings switch magnet 17 into circuit by closing a path which may be traced from the live pole of battery 245 through the winding of magnet 17, conductor 246, sequence contact 99 to 1), conductor 247,

sequence contact 73 (6), conductor 186 and closed contact 185 to the circuit of relay AR which goes to ground at alternate contact 178 of relay CR, as previously traced.' The closing of this circuit for magnet 17 causes it to bring about a clutching engagement between the constantly rotating disk 16 and k the co5perating disk '15 to rotate shaft14' which carries the wipersor brushes 24,

and 26 of the switch S As the wipers advance, only those are in position to engage the bank contacts 21, 22 and 23, which have been tripped by a properly set projection on the shaft 30. As the switch wipers advance, the actuating arms 38 and 39 pass over the associated racks 40 and 41 to actuate the contacts 34 and 35, in the one case, and 36 and '37, in the other, to short-circuit the I sender magnet 175 in a way similar to that previously described in connection with con tacts 234 and 235 associated with the brush sociated with the brush selecting magnet 33.

- The path in bridge of conductors 204 and 205 may be,traced from conductor 204 through conductor 248, conductor 249, contacts 34 and 35, conductor 250, conductor 251, sequence contact 101 (0 to 2), and conductor 252 to conductor 205. It may be pointed out that if the sequence switch had been in positionto close sequence contact 10,1 (1 to 3), then the circuit would have included impulse contacts 36, 37, conductor 253, conductor 254, sequence contact.

101 (1 to 3) and conductor 252. It may also be pointed out that contacts 34, 35 36, and

37 of switch S", are connected in parallel with the corresponding contacts of switch S From this description, it will be seen that when switch S is advancing, its contacts34 and 35 will not be closed until the end of the arm 38 engages the teeth of the rack 40. When this occurs there will be an intermittent closing of the contacts34, 35, to intermittently short-circuit the magnet 175 of the sender SN. short-circuiting path may be traced from sequence contact 43 (2 to 3) over impulse wire 206, bank contact 207, iviper'208 of switch S conductor 205, conductor 252 sequence contact 101 (O to 2), conductors 251 and 250,, contacts 35 and 34, conductors 249, 248, 204, sequence contact 66 (31 to 12) and alternate contact 182 to ground The intermittent closing of this grounded branch For convenience, the

will bring about intermittent energizations of magnet 175 of the sender and when the requisite number of advance steps have been made, as determined by the setting of the sender, then the contact 174 of thesender willbejopened and relays CR and AR and motor magnet 17 however, only occur when the wipers 24 and 25 of the switch S have been advanced to the desired bank contacts 21 and 22, and by reason of their tripped condition, brought into electrical contact with those bank con- I tacts. WVhen this occurs, the circuit oforder wire conductors 152 and 153 will be completed through the springs 18 and 19, wipe-rs 24 and 25 and bank contacts 21 and 22 of switch S and thence through the order wire conductors 154 and 155 running to the desired terminating'operators set T O. The next operation is the advance of sequence switch SS from position 6 to position 7. This is brought about upon-the opening of contact 174 of the sender with the consequent deenergization of relays CR, AR and magnet 17. It may here be pointed out that the rotary switch S is provided with off-normal contacts255, 256 and 257, which are actuated whenever the wipers of switch S are rotated from normal position. As the switch moves fromhormal, contacts 255 and 256 are opened and contacts 256 and decnergized. This will,

257 are closed. -The closing of the latter contacts energizes relay 217 by closing a circuit which may be traced from the live pole of battery 258 through the winding of relay 217, conductor 259 and contacts 257 and 256 to ground. This connection is also provided with a parallel path through similar contacts of switch S The energization of relay 217 has to 'do with the establishing of circuits for the subsequent advance of sequence switch SS and theenergization of relay CR. The circuit by which sequence switch SS is advanced to its seventh position, extends from the live pole of battery 183 through the winding of magneg SM, sequence contact 68 (6), conductor 211, alternate contact- 216, conductor 218, sequence contacts 108 (N), (N), 124 (N), 132 (N), 140 (N), 148 (N), conductor 219, sequence contact 79 (4 to 12), conductor 220 and normal contact 182 to ground. Sequence switch SS is thus moved to position 7 As soon as this takes place, a circuit is established for energizing control relay CR. This circuit extends from the live pole of battery 172, through sequence contact 50 (1 to 3), the winding of relay GR, sequence contact 47 (2 to 3), sequence contact 45 (2 to 3), sequence contact 45 (2 to 3), conductor 221, bank contact 222, wiper 223, conductor 224, sequence contact 78 (7), conductor 225,alternate contact 229, conductor 230, se-

quence contacts 109 (N), 116 (N), (N), 133 (N), 141 (N), 149 conductor 205,

resulting energization of relay CR closes alternate contact 178 to ground and again energizes relay AB in the manner heretofore described. At the same time, magnet SM of sequence switch SS is brought into a circuit which may be traced from the live pole of battery 260 through the winding -of magnet SM conductor 261, sequence contact 73 (7), conductor 186'and closed contact 185 to the circuit of relay AR which goes to ground at alternate contact 178 of relay CR. The-result of closing the circuit of magnet SM is to cause sequence switch SS to advance from its normal position to its zero position. In doing so its contact 110 which is opened at positions of the sequence switch and closed between positions as indicated by the numerals adjacent to it, makes a momentary connection between conductors 204 and 205, by-whieh the usual ground connection is established to shortcircuit the sender magnet 175. A reference to the connection of conductors 236 and 237 in the case of the brush selection, and of the conductors 248 and 252 in the case of the group selection,'will show that itis the same conductors 204 and, 205 which bring about the short-circuiting of the sender magnet whenever they are electrically connected. It will therefore not be necessary to again trace this path to ground. .If the sender is set so as to cause the switch SS to make only one advance step, then the sender contact 174 will be opened as a'result of the first impulse transmitted by the closing of contact 110, and the relays CR and AR and the magnet SML will be deinergized. The result of such denergization will be to stop the switch SS in its zero position. It may be assumed, however, in the present case, that the sender is set so as to require five impulses by the contact 110 before this breaking down of the fundamental circuit is brought about. In such case the switch SS will be .moved into position 4, which connects the thousands lamp L into circuit.

This lamp L will be the one corresponding to the thousands digit of the called number as set up on the sender SN.

The breaking down of the fundamental circuit, as just explained, will cause sequence switch SS" to advance fromits seventh positact 68 (7), conductor 243, sequence con tacts 10s (0 to 16), 115 N 121 N), 132

(N), 140 (N), 148 (N), conductor 219, sequence contact 79 (4 to 12), conductor 220, normal contact182 to ground. As soon as sequence switch SS advances to its eighth position, relay CR will be again energized with a resulting energization of relay AR and thereupon an energization of magnet SM of sequence switch SS. The clrcuit by which relay OR is energized maybe traced from the live pole of battery 172 through sequence contact 50 (l to 3), the winding of relay CR, sequence contact 47 (2 to 3), se quence contact 45 (2 to 3), sequence contact 45 (2 to 3),conduct0r 221, bank contact 222, wiper 223, conductor 224, sequence contact 78 (8), conductor 244, sequence contacts-109 0x0 16).116, (N)-,-,125 (N), 133

N 111' (N), 1 19 (N), conductor 205,

wiper 208, bank contact 207, conductor 206,

sequence contact 43 (2 to 3) and thence over the link-circuit strands L and L through the sender magnet 175 and back to ground at sequence contact 59 (1 to 3). As before, the closing of alternate contact 178 of relay CR, energizes relay AR and the latter, by closing its contact 185, completes an energizing circuit for the associated switch magnet, which in this case is the magnet SM of sequence switchSS. The circuit of the latter extends from the live pole of battery 262, through the winding of magnet SM, conductor 263, sequence contact 73 (8), con ductor 186 and closed contact 185 to the circuit of relay AR which is connected to ground at alternate contact 178 of relay CR. As before, the energization of the motor magnet of the sequence switch causes it to advance and as it advances, its contact 117, which is open at positions and closed between positions momentarily short-circuits the sender --magnet 175 and these short-circuiting impulses continue uritilthe sender has advanced far enough to open its contact tion. In certain types of trunking arrange ments, this operation is necessary to pick out a proper group of trunks, and, accordingly, in the present instance, where the sender. is assumed to be of the type where such selection is necessary, the advance of the switch SS does not cause the lighting of a lamp since the position of the switch does not in any way correspond to a digit of the number which the tandem operator is to read off to the terminating operator in giving er the number of the called line. In the present instance, this switch merely comes into play in establishing the complete circuit for the associated thousands and hundreds lamps. As soon as switch SS has stopped as a result of the deenergization of relays CR and AR, a circuit for sequence switch SS is established for the purpose of advancing said switch SS to its ninth position. The circuit for bringing about this result extends from the live pole of battery 183 through the winding of magnet SM, sequence contact 68 (8), conductor 211, sequence contacts 115 (0 to 16.), 124 (N), 132 (N), 140 (N), 148 (N), conductor 219, sequence contact 79 (4 to 12), conductor 220 and normal contact 182 to ground. The advance of-sequenceswitch SS t0 the ninth position results in establishing a new energizing circuit for relay CR, with a consequent energization of relay AR and motor magnet SM of the next sequence switch SS The energizing circuit for'relay CR extends from the live pole of battery '172 through the winding of relay CR, sequence contact 47 (2 to 3), sequence contact (2 to 3), sequence contact 45 (2 to 3), conductor 221, bank contact 222, wiper 223, conductor 224, sequence contacts 78 (9), con ductor 225, sequence contacts 116 (0 t016), 125 (N),133 (N), 1 11 (N), 149 (N), conductor 205, wiper 208, bank contact 207, conductor 206, sequence contact 43 (2 to 3), sequence contact 43 (2 to 3), resistance 173, to the tip side of the link circuits L L through the sender magnet 175 and back over the sleeve side of link circuits L and L to ground at sequence contact 59 (1 to 3). As before, the energizing of relay CR -causes the energization of relay AR and a circuit is provided for the associated switch magnet which in the present instance is the magnet SM of switch SS The air cuit for said magnet extends.from the live pole of battery 264 through the winding of magnet SM conductor 265, sequence contact 73 (9), conductor 186, closed contact 185 and thence to ground at alternate contact 178 of relay CR as before traced. Again the advance of the sequence switch connects conductors 204 and 205 momentarily by a bridging contact 126- which is open at the positions of the switch and closedbetween its positions. This contact 126 short-circuits the sender magnet 175, as in the case of the corresponding contacts of the preceding switches SS and SS", and the advance continues until contact 174 of the sender is opened. This, as before explained, will depend upon the setting of the sender. If it be assumed that the sender is set so as to advance the switch SS to its third position, in such instance the proper lamp L will be connected into circuit. The lamp in. this instance will correspond to the hundreds digit of the called line. 1 7

Upon the breaking down of the fundamental circuit in this instance, the relays CR, AR and the magnet SM will be deenergized and immediately upon the deenergization of relay AR, sequence switch SS will be advanced from its ninth position to its tenthposition. The circuit for bringing about this result may be traced from the live fpoleof battery 183 through the winding 0 magnet SM, sequence contact 68 (9), conductor 243, sequence contacts 124 (0 to 16), 132 (N), 140 (N), 148 (N), conductor 219,; sequence contact 79 (4 to 12), conductor 220 and normal contact 182 to ground. As soon as switch SS has thus advanced to its tenth posit-ion, relay CR will be agaiuenergized with a resulting energization of relay AR and of a newswitch magnet,namely,magnet SM of sequence switch SS The circuit for en ergizing relay CR extends as before over conductors- 221 and 224, thence through sequence contact 7 8 (10), conductor 244', sequence contacts 125 (0 to 16), 133 (N), 141 (N), and 149 (N), and conductors 205 and 206 to the sleeve side-of the link circuits L and L and thence through sendermagnet 175 and over. the sleeve side of link circuits L and L to ground at sequence contact 59 (1 to3). The closing of alternate contact 178 of relay CR, before, energizes relay AR and completes the ground connection for the energization of the associated switch motor magnet, namely, the magnet SM The circuit by which the latter magnet is energized extends from the live pole of battery 266 through the winding of magnet SM conduct-or 267, sequence contact 72 (10), conductor 186 and closed contact 185 to I the circuit of relay AR, which, as before pointed out, closed to ground at alternate contact 178 of relay CR. Like its predecessors, the sequence switch SS momentarily connects conductors 204and 205 as the switch advances, and thereby momentarily and intermittently short-circuits the sender magnet 17 5, as before explained. The contact 134 of switch SS performs this short-circuiting function.

Like the corresponding contacts of the other switches, it is open in the switch positions and closed between those positions. It may be" assumed that the sender is set to stop switch SS upon its ninth position. Under this assumption, as soon as the ninth position is reached, the fundamental cir-' cuit will be broken down by the opening of sender contact 174, as before The result will be the denergization of relays GR and AR and of motor magnet SM As soon as sequence switch SS is brought to rest, sequence switch SS is advancedfrom its tenth position to its eleventh position. This is brought about by the deenergization of relay AR, which followed the breaking down of the fundamental circuit. The circuit by which this advance of switch SS is brought about extends from the live twelfth position.

pole of battery 183 through the winding of magnet. SM, sequence contact 68 (10),conductor 211, sequence contacts 132 (0 to 16), 140 (N), 148 (N), conductor 210, sequence contact 79 (4 to 12), conductor 220 and normal contact 182 to ground. As soon as this advance has taken place, relay (R will be again energized by a circuit including conductors 221 and 224, as before, thence by way of sequence contact 78 (11). conductor 225, sequence contact .13 3 (Oto 16), l-ll-(N), 149 (N), conductors 203 and 200 to the tip side of the link circuits L and L thence through the winding of sender magnet. 179 and back over the sleeve side of the said link circuits to ground at sequence contact 59 (1 to 3). Following this, relay AR is energized by reason of the closure of alternate contact 178- of relay CR. At the same time magnet SM ofsequence'switch SS is brought into circuit. This circuit extends from the live pole of battery 268 through the winding of magnet SM, conductor 260, sequence contact 72 (11), conductor 186 and closed contact 185 to the circuit of relay AR and thence over said circuit to ground at alternate contact 178. The impulse contact 142 of sequence switch SS is open at the positions of the switch and closed between them, so that like the other.impulse contacts it will momentarily connect conductors 204 and 205, and thereby momentarily intermittently shortcircuitsender magnet 175. If it be assumed that the sender is set so as to stop the switch SS 'in position 5, then as soon as said switch reaches said position, sender contact 174 will be opened to break down the fundamental circuit and deenergize relays CR and AR and magnet SM in the manner heretofore repeatedly explained.

As soon as the fundamental circuit is thus broken down sequence switch SS will advance from its eleventh position to its The circuit for bringing about this advance extends from the live pole of battery 183 through the winding of magnet SM, sequence contact 68 (11), conductor 243, sequence contacts 140. (0 to'16), 148 (N), conductor 219, sequence contact 79 (4 to 12) and normal contact 182 to ound.

As soon as this advance of switch SS toposition 12 has taken place. relays CR- and -AR and magnet SM will be energized. 55

16), 149 (N) and conductors 205 and 206 to the tip strands of link circuits L L thence through the winding of sender magnet 175 and back over the sleeve strands of said link circuits to ground at sequence contact 59 (1 to 3). The resulting energlzation of relay CR by closing alternate contact 178 brings about the energization of relay AR and the latter by closing its contact 185. brings sequence magnet SM into circuit. The latter circuit extends from the live pole of battery 270 through the winding of magnet SM, conductor 271, sequence contact 72 (12), conductor 186 and closed contact 18-? to the circuit of relay AR, which, as before pointed out, is closed at alternate contact then contact 174 of the sender is opened and 'relays CR and AR- are dcenergized with a resulting deener izationof magnet SM of sequence switch SS. If 1t be assumed that the sender 1s set so as to stop the switch SS in position 1 then it will be seen that party line lamp L is brought into connection by the resulting advance of the switch. Advances to other positions may be used to bring in otherindicatin}! lamps. For instance, if the switch be left in positions zero or then lamp L would be brought into circuit. Likewise in positions zero 'to 4 inelusive, lamp L would be brought into circuit.

The next piece of mechanismto'be operated is the, sequence switch SS, which moves into position 4 out of position 3. which it has occupied during the transmission of impulses in connection with the sender SN. The circuit for the sequence switch SS may be traced from the live pole of battery 177 through the winding of magnet SM, sequence contact 58'( 2 to 3), sequence contact 58 (3), conductor 272, bank contact 273 of switch S wiper 274, conductor 27 5, sequence contact 148 (0 to 16), conductor 219. sequence contact 79 .(4 to 12), conductor 220 and normal contact 182 to ground. The sender SN has now completed its required operations in connection with the particular call under consideration and it is restored to normal position and contacts 166 and 167 close with contacts 27 6 and 277 so as to com plete the strands of link circuit L. This release of the sender and movement of the contacts 166 and 167 may be automatic, or, for the purposes of the present disclosure., the same may be considered as performed by hand. As soon as the contacts 166 and 167 complete the strands of the link circuit L, a circuit is completed for relay 27 8 which may be traced from battery 279 through sequence contact 45 (4 to 17), sequence contact 45 (4 to 5), the winding of relay 278,.

the'tip strands of link circuits L and L including engaged contacts 166 and 276 and repeating coil winding 28) to ground at 281. The resulting energization of relay 278 completes a circuit for the double wound relay 282 which may be traced from battery 279 through sequence contact 45 (4 to 17), sequence contact 45 (4 to 5), the winding of relay 278, sequence contact 44 (4), closed contact 283 of relay 278, sequence contact 48 (4 to 5), sequence contact 48 (4 to 5), and the left-hand winding of relay 282 to ground. The resulting energization of relay 282 completes a locking circuit for said relay which may be traced from the live pole of battery 284 through the right-hand wind-' ing of relay 282, conductor 285, sequence contact 58 (4 to 8) sequence contact 58 (4 to 8), conductor 195, sequence contact 57 (4 to 8), sequence contact 57 (4 to 8), conductor 286, and closed contact 287 to ground. The

completion of the locking circuit just traced results in placing ground upon the conductor 195. It thereby completes a circuit for test relay TR which may be traced from the live pole of battery 193 through the winding of relay TR, sequence contact 65 (2 to 12), sequence contact 65 (12 to 15), wiper 197 of switch S bank contact 196 and conductor 195 to ground at closed contact 287 of relay 282. The energizing of relay TR closes a starting circuit for sequence switch SS which thereupon moves from position 12 to position 13, The circuit by which this latter movement is brought about may be traced from the live pole of battery 183 through the winding of magnet SM,

the sequence switch SS The function of. the lamp allotter mechanism is to test out p the difierent circuits associated with the finders S until it engages one whose se quence switch SS is in position 13. YVhen it encounters such a circuit the sequence switch SS of the allotter comes to rest. In this testing operation the test relay TR determines the point at which the sequence switch SS shall come to rest.

As soon as sequence switch SS moves into position 13, a circuit is established for relay.

AR which may be traced from the live pole of battery 181 through the winding of relay AR, sequence contact 65 13 to 15), sequence contact 65 (12 to 1'5), wiper 197, bank contact 196, conductor 195, sequence contact 57 (4 to 8), sequence contact 57 (4 to 8), conductor 286 and closed contact 287 to ground. The resulting energization of relay AR closes contact 185 and thereby-places ground upon conductor 186. If the lamp allotter be in the position illustrated in the drawing, then as soon as sequence switch SS moves into position 13, relay TR will be energized by the closing of a circuit which may be traced from the live pole of battery 288 through the winding of relay TR, sequence contact 84 (1), conductor 289, resistance 290, sequence contact 72 (13 to 15), to conductor 186 which is grounded by reason of the energization of relay AR, as before explained; The resulting energization of relay TR closes alternate contact 291 and thereby establishes a starting circuit for sequence switch SS which may be traced from the live pole of battery 183 through the winding of magnet SM", sequence contact 68 (13), sequence contact 87' (1), alternate contact 291, sequence contact 66 (13) and alternate contact 182 to ground. As a result of the closing of this circuit, sequence switch SS moves from position 13 to position 15.

If it be assumed that the allotter sequence switch SS be' in some other position than that illustrated, then as 'soon as sequence switch SS moves into position 13, a starting circuit will be established for sequence magnet SM which may be traced from the live pole of battery 272 through the winding of magnet SM normal contact 291 of relay TR, sequence contact 66 (13), and alternate contact 182 to ground. The closing of this circuit will cause the switch SS to advance. As it advances,,the winding of relay TB is brought successively into circuit engagement with branches like that through position 1 and conductor 289. As soon as a grounded branch is encountered, relay TR is energized to interrupt the circuitof magnet SM and prevent the further advance of the switch. The test relay TB is short-circuited by sequence contact 85 in all positions of the switch except positions 1, 4, 7, 11, 14 and17, indicated by the numerals adjacent to it. Thusa full advance ot the switch to these positions is insured.

As soon as sequence switch SS moves through position 14 and into position 15, battery connections are supplied to the annunciator lamps. Thus lamp L will be supplied by current from battery 292 over a circuit which may be traced from the live pole of battery 292 through sequence contact 70 (14 to 15), conductor 293, sequence contact 112 (2 to 3), sequence contact 103 (4) and lamp L to ground. Similarly a circuit for lamp L extends from the live pole of battery 292 through sequence contact 70 (14 to 15), c0nductor 294, sequence contact 113 (3), sequence contact 119 (3) and lamp L to ground. A similar circuit for lamp L extends from the live pole of bat tery 292 through sequence contact 70 v(14 to 15), conductor 295, sequence contact 128 (9) and lamp L to ground. A circuit for lamp L extends from the live pole of battery 296 through sequence contact 71 (14 to 15), conductor 297, sequence contact 137 (5) and lamp L to ground. A similar circult for lamp L extends from the live pole of bat- TO and the terminating operators telephone set T0 is completed at sequence contacts 76 (14 to 15) and 77 (14 to 15).

At the time sequence switch SS moves into position 15, .a circuit is also closed for magnet 300 (Fig. 2), which may be traced from the live pole of battery 301 through sequence contact 49 (4 to 5), the winding of relay 300, sequence contact 51 (4 to 17), sequence contact 51 (3 to 5), conductor 200, bank contact 199, wiper 198, sequence coni tact 64 (3 to 15), sequence contact 64 (14 to 15) and normal contact 190 to ground. The

energization of relay 300 by closing alternate contact 302 completesv a new circuit for control relay CR which may be traced from the live pole of battery 303 through sequence contact 52 (4 to 9), alternate contact 302, sequence contact 50 (4 to 17), the windingof relay CR, and sequence contact 46 (4 to 17 to ground. As a result of the energization of relay CR, sequence switch SS moves from position 4 to position 6; The circuit for bringing about this result may be traced from the live pole of battery 177 through the winding of magnet SM, sequence contact '56 (4) and alternate contact 178 of relay CR to ground. Immediately following this advance a new starting circuit is provided for the same switch and it is advanced from position 6 to position 7. The starting circuit for bringing about this latter'advance extends from the live pole of battery 177 through the winding of magnet SM, sequence contact 56 (6) and normal contact 304 of relay 305 to ground.

With the parts in this condition, the operator having control of the plug P and having the head-set TO, reads ofi? the number of the called line as the same is indicated by the lamps of Fig. 6, and the distant operator having control of the plug P and having the head-set TO, upon obtaining the order, assigns a trunk L in the usual way, and the operators plug in, the one into jack J 2 of the assigned trunk, and the other into jack J 3 of the called line.

As soon as plug P is inserted into ack J relay 305 is energized by the closing of a local circuit, which may be traced from the live pole of battery 306 through the winding of relay 305, conductor 307, local contacts of the plug 1 and jack J and resistance 308 to ground. As soon as relay 305 is energized, a starting circuit is established for sequence switch SS which may be traced from the live pole of battery 177 through the winding of magnet SM, sequence contact 56 (7) and alternate contact 304 to ground. The closing 'ofthis circuit causes sequence switch SS to advance from sition 17.

a As a result of this advance of switch SS to position 17, the ground upon conductor 195 is removed by the opening of sequence contact 57 (4 to 8). The removal of this ground opens the previously traced circuit through the right-hand winding of the double wound relay 282, but said circuit is replaced by another which extends through sequence contact 52 (9 to 17), alternate contact 302 of relay 300, sequence contact 50 (.4 to 17 the winding of relay CR and sequencecontact 46 (4 to 17) to ground; The removal of the ground from conductor 195 also denergizes relay AR and the test relay TB of the allotter, which has remained in circuit up to' this time and kept the switch SS in connection with the parti ular finder switch circuit in use. Thus, it be seen that the allotter stays in engagement with the switch circuit during the time that the lamps are illuminated, and until the tandem operator plugs into the trunk after reading the indication of the lamps to the terminating operator. The allotter is thenfree to seize a new finder switch circuit which is in the proper condition. In this way, the calls coming in upon the different switch circuits cannot interfere with each other, and only one indication at a time can be set up upon the annunciator lamps.

It will be noted that relay GR is now maintained energized over a local circuit which also includes the right-hand winding of relay 282 and alternate contact 302 of relay 300. The relay 300, although initially energized by a circuit extending through the finder switch S is now maintained energized by a circuit which may be traced from position 7 to pothe live pole of battery 309, through sequence contact 44 (5 to 17 closed contact 283, sequence contact 49 (5 to 17 the winding of relay 300, sequence contact 51 (4 to 17), se-

quence contact 51 (5 to 17 and alternate.

tion 17 Instead of the circuit extending from battery 279 through sequence contact 45 (41 to 5) directly to the winding of relay 278, it now extends via sequence contact45 (5 to 17), closed contact 201 of relay CR, sequence contact 4:3 (5 to 17), Sequence contact 13 (5 to 17), to the winding of relay-278. As soon as switch SS advances to position 17, a circuit is established over the sleeve side of the link circuits L and L which may be traced from the live pole of battery 163, through repeating coil winding 310, the sleeve strand of link circuitL including engaged contacts 7 277 and 167, sleeve contacts of switch S,

sleeve strand of link circuit L including sequence contactsAS (8 to 17) and 18 (8 to 17), conduc or 311, closed contact 312 of relay 300, retardation coil 313, closed contact 314; of relay 315, and sequence contact (17) to ground. Of course this circuit will not be established when relay 315 is energized, as will be the case when the circuit is extended to the called line L but at a time prior to the response of the called party at station N. It may be pointed out at this time that while switch SS is in positions 6 and 7, the previously traced circuit for relay 300 divides at sequence contact 51 1 to 17) and one branch extends through alternate contact 178 of relay CR, as before traced, and the other branch extends through sequence contact 51 (6 to 7 lamp 316, and relay 317 to ground. The lighting of the lamp 316 indicates when the circuit'is in condition. for the operator toinsert plug P into jack J and the lamp remains lighted until the plug has been so inserted. Relay 317, by means otits contact 318, may extend this signal to any desired distant pointfor the purpose of supervising the work of the operators.

As before pointed out. the removal of ground from conductor 195. by reason of the advance of sequence switch SS to position 17, caused relay AR to be decnergized. In consequence of such dei nergization, sequence switch SS advancesfrom position 15 to position 16. The circuit by which this advance takes place extends from the live pole of battery 183 through the winding of magnet SM. sequence contact 67 (15) and normal contact 182 to ground. In consequence of this advance of switch SS the finder switch 7 2 is restored to normal position. This is brought about by the closing of a circuit for restoring magnet RM of said switch. This circuit extends from the live pole of battery 13% through the winding of magnet RM. conductor 319. and sequence contact 31 (16) to ground. The resulting energization of magnet RM withdraws the pawl 191. and forces the lower end ot the shaft 10 of switch S into frictional engagement with the constantly driven disk 12. and as a result. the switch is drawn down into its normal position. As soon as the finder switch S gets back to its normal position, its grounded contactbrush 320 engages commutator contact 321, and thereby completes a starting circuit for sequence switch SS by which it is moved from position 16 to position 17. The entire circuit be traced from ground at contact brush 320, through said brush, contact 321, conductor 322, sequence contact 67 (3 to 16) and winding of magnet SM to battery 183. The advance of switch SS from position15 to position 16 opens the connections from batteries 292 and 296 to the various lamps of the annunciator. Like-- wise, as before indicated, the test circuit of the allotter test relay TR is interrupted at sequence contact 72 (13 to 15) by the same movement of sequence switch SS. In positions 16and 17 of switch SS, a releasing circuit is established for sequence switch SS which may be traced from the live pole of battery 202, through the winding of magnet SM*, sequence contact 91 (O to 15), conductor 323 and sequence contact (16 to 17).

to ground. As a result of the closing of this circuit, sequence switch SS advances to position 16. As soon as switch SS reaches position 16, a circuit is established for advancing the brush selecting shaft 30 to its normal position. This circuit extends from the live pole of battery 231. through the winding of magnet conductor 324. normal contact 325' of'relay 326. and sequence contact 97 (16) to ground. This circuit will be maintained until relay 326 energized.

The circuit for energizing said relay extends from the live pole of battery 327. through sequence contact 100 (15 to 16). the winding.

of relay 326 and closed off- normal contacts 238 and 239 to ground. It will be remembered that these contacts are brought into engagement when the shaft 30 reaches its normal position. As soon as relay 326 is energized. a new release circuit will be estal lished, thistime for the brush advancing magnet 17. This circuit may be traced from the live pole of battery 245. through the winding of magnet 17. conductors 2:16 and 328, normal contact 329 of relay 330, alternate contact of relay and sequence contact 97 (16) to ground. This circuit will continue until interrupted at contact 329 by the energization of relay The circuit for bringing about such encrgization extends from the live pole of battery 327. through sequence contact 100 (15 to 16), the winding oi relay 336 and closed off- normal contacts 255 and 256 to grounch These oil-normal contacts are brought into engagement when the switch wipers reach their normal position. it will be noted that as soon as sequence switch SS reached position 16. so as to close sequence contact 106 (1.1 to 16). similar circuits were at once established for" relays 331 and through the correspond.-

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