US1504228A

US1504228A - Telephone-exchange system

Info

Publication number: US1504228A
Application number: US427445A
Authority: US
Inventors: John W Gooderham
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1920-11-30
Filing date: 1920-11-30
Publication date: 1924-08-12
Anticipated expiration: 1941-08-12
Also published as: US1504231A

Description

15%,22 J. W.. GOODERHAM TELEPHONE EXCHANGE SYSTEM Filed Nov. 30. 1920 6 SheetsSheet 1 vJ. W. GOODERHAM TELEPHONE EXCHANGE SYSTEM 7 ugo 1L2 Filed Nov. 30

6 Sheets-Sheet 2 MQN N NRA wimqi 83 mm; mm;

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J. W. GOODERHAM TELEPHONE EXCHANGE SYSTEM Aug 12 Filed Nov. 30. 1920 .6 Sheets-Sheet 5 an E W Sm, W

NR QM Mmnfar m h! 6 ami /"1mm wmm Amigo 15.29 J. GOODERHAM TELEPHONE EXCHANGE SYSTEM Filed NOV. 30.. 1920 6 Sheets-Sheet 4 Aug. W, 192% J. W. GOODERHAM TELEPHONE EXCHANGE YSTEM Filed Nov. 30, 1920 6 Sheets-Sheet 5 071 6/720/5 John W Gamfwfia mm W My mwmm mg. 112 W 383?;

J. W. GOODERHAM TELEPHONE axcmmea SYSTEM Filed Nov. 30, 1920 6 Sheets-Sheet 6 kwm Patented Aug. 12 192 p. a

"' YORK, N. 32"., ASSIGNOR TO WESTERN ELECTRIC COM- K'Odlll, A GOBPOBATION 0 NEW' YORK.

HQNE

IANGE SYSTEM.

Application ctl November 30, 1820. Serial No. 427,4A5.

To (52] whom it may concern:

Be it known that l, Jon -W. GoonnnrrAM,

a citizen of the Uni-rec States, residing at "ew York, in the county of New York, ate of New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to a telephone systern and more particularly to a system in which connections between subscribers lines are established by means of mechanical switching devices.

In the installation of telephone exchanges in which mecnanical switching mechanism is employed extending connections between subscribers lines it is the usual practice to dii de the entir exchange into a plurality iices and to make provision in each otlice ultimately giving service to 10,000 subirs lines. The number of oliices in the scribers, it may be, as often occurs, that a selector switch will be set to extend a connection into a division of an oflice which has not yet been installed or a final selector switch will be set upon a blank bank terminal to which no subscribers line has been connected or upon the terminal of a line from which former service has been discontinued. In such a case it is desirable to route such connections to a special operators position, sometimes called an intercepting operators position, so that the subscriber or operator may be informed that they have inadvertent ly established the connection to such a blank terminal. 7

It is therefore an object of the invention to provide means for extending a connection automatically to anoperators position when a selector switch is inadvertently positioned upon a blank set of bank terminals.

A further object of the invention is to proincna to is so selected that at the outset no vide a group of trunk circuits less in numoflit required to function to its ultimate ber than the number of blank terminals in the capa y and therefore only such switching bank of a selector switch for extending a units are initially installed in each or'lice as connection to an operators position when wry to for the immediate exi the s7 As the demand for ice in any particular office increases, a'd' ditio switching units are added until the imate capacity is reached when a new onice established.

-"=")='lwiously during the period in which the l for service is increasing, there must is be switching units which not employ .d to their full capacity. This is espec all true of incoming selector switches which have access to small groups or divisions of trunk lines and to final selector switches which have access to the individual s bscribers lines. Thus there will be num of terminal sets in the banks of incoming or switches which are blank or not con .ed to working trunk lines ending to selector switches, and ter; nal sets in anlis of fin l sel ctor switches which to subscribers lines. 7 v, tee upon full me chanical basis, that is calling subscribers set up connections by dialing the numbers desired lines to position the selector switches, or if the connections are established semi mechanically, that is an operator causes the setting of the selector switches in accordance with insti actions received from calling subthe selector switch is erroneously positioned upon one of such blank terminals.

The principal feature of the invention resides in providing a group of trunk lines extending from the banks of selector switches in which there 'are blank terminals to such intercepting operators positions. The number of trunks in the group is made adequate to care for the maximum density of such trafiic to the operators position and is less than the total number of blank terminals to be served. Thus a selector switch upon being set upon a set of blank terminals will automatically move its brushes to the terminals of the first trunk of the group extending to the intercepting operators position. If this trunk is busy, the switch will continue to move its brushes over the other trunks of the group until an idle trunk is found.

Further features of the invention will be apparent from the following description considered in connection with the accompanying drawings in which Fig. 1 shows one of a group of lines terminating in full mechanical oflice of the exchange and a rotary line switch individual to such line by means of which the subscribers line may be connected to an idle district selector switch; Fig. 2 shows district selector and ill sender finder switch together with the circuits and controlling mechanism associated therewith; Fig. 8 shows diagrammatically a portion of a register sender which may be associated with the district selector of Fig. 2 for controlling the setting of the selector switches; Fig. 4- shows an incoming selector switch provided with mechanism for applying ringing current to the terminals of called lines together with the circuits and mechanisrn for 'controlling'such switch; Fig. 5 shows the mechanism and circuits of a final selector switch; Fig. 6 shows the firstand last trunk lines of a group of trunk lines extending from blank terminals of the final selector switch of Fig. 5 to an intercepting operators position and a cord circuit at the operators position; Fig. 7 shows a diagram of circuits over which connections may be extended to an intercepting operators position; and F igBillustrates the manner in which the several fignresshould be arranged to show as much of a'complete organization of circuits as is necessary to properly illustrate the invention. In Fig. 6, relays 60:2

-and 605 are shown with optional wiring according to whether the trunk line is one of a group'at which time it will be wired in accordance with relay 602, or an in dividual line using the wiring of relay 605.

The calling subscribers line K is of the usual type provided with a transn'iitter, receiver and call-bell and, since it terminates in a full mechanical exchange, it is also equipped with the impulse sending dial S .of the usual type.

The subscribers line terminates in an individual trunk finding switch 100 of the well-known step-by-step type which, througl a plurality of wipers, has access to a group oftrunk lines terminating in district selector switch s. The switch is provided with a stepping magnet for advancing the wipers over the terminals of trunk lines in search of an idle trunk line and for advancing the wipers forwardly to normal position upon the release of the established connection.

The "district selector switch 250, the incoming selector switch 450 and the final selector switch 550 disclosed in Figures 1 and 5 are of the type shown and described in the patent to CraftjandBeynolds 1,12 696 issued January 5, 1915. Each of these switches is provided with a vertically di posedswitch shaft having five sets of brushes each brush set having access to a bank of 100 terminals. ,For driving the switch shaft upwardly an np-drive magnet is provided which when energized presses the switch shaft against a constantly driven power drum, and for restoring the switch to normal position a second down-drive net is provided which when energized presses the switch shaft against a second constantly driven power drum. For determining the particular set of brushes on the switch shaft to be employed, a tripping spindle is provided as described in the patent hereinbefore referred to. The final Selector switch 550 difi ers from the other selector switches in being provided with additional means comprising a second up-drive magnet and driving drum for driving the switch shaft upwardly, whereby the shaft is driven upwardly by the two up-drivc drums at different speeds, rapidly during brush selection and group selection, and more slowly during the terminal selection movement of the switch shaft.

The sender finder switch SF shown in Fig. 2 is of the well known step-by-step type, the wipers being advanced by the stepping magnet to hunt for an idle sender such as diagrammatically shown in Fig. 23. This switch has no normal position, the wipers resting in contact with the bank terminals last employed, when the switch is not in use. Only so much of the register sender is shown in Fig. 3 as is necessary for annnderstanding of the invention. This sender may be of the type disclosed in Patent 1,395,977 issued to F. A. Stearn and F. J. Scudder, November 1, 1921, and functions in the manner set forth therein to control the

selector switches

250, 450 and For controlling the circuits associated with the several selector switches and the circui s of the ofiice sender, auxiliary switches are provided. These switches may he of the type described in the patent to Reyno ds et al, No. 1,127,808 issued February 0. HHS. and known in the art as sequence switches. Each sequence switch comprises a rotatable shaft driven from a cons antly operated source of power through a magnetic clutch member and carries a plurality of circuit closing cams which, at different. radial positions of the shaftcause the closure of a plurality of contacts. The ram contacts as sociated with each sequence switch 21H- closed only in the positions ind cated by the numerals associated with each contact with the exception of the master contacts .201. 301, 101 and 501 associated respectively with

sequence switches

200, 300, 4:00 and 500, these latter contacts being opened in the po sitions indicated by the numerals appe; ng adjacent to such contacts and closed n all other positions.

The differentpieces of a iparatns employed in the system having now been fully de scribed, it is thou ht that a clearer under standing of the invention may be had from a description of the method of establishing: a connection. It will be assumed. that the calling subscriber at the subs a ion c siring a connection with a subscriber in his own office whose directory No. is PENns vl- Vania 8432, through nadvertence dials th number corresponding to PENnsylvania 8632 and that this latter number has not been assigned to any subscriber, but appears a blank terminal in the banks of all final selector switches which have access to the group of lines containing lines 8500 to 8000 inclusive.

The calling subscriber to initiate a call removes his receiver from its switch hool; thereby closing a circuit for the line relay 101 of the trunk hunting switch 100, which circuit may be traced from grounded battery through the right hand winding of re lay 101, the innermost lower armature and back contact of cut-off relay 102, over line conductor 103, through the substation of subscribers line K and then back over line conductor 104 to ground at the upper ture and back contact of cut-oil relay 102. The line relay energizes in this circuit and closes a circuit for the stepping magnet 105 of the switch 100, which circuit may be traced from grounded battery through the winding, armature and contacts of magnet 105, conductor 106, the lowermost armature and back contact of relay 102, the right hand armature and front contact of relay 101, conductor 107 and thence to ground through the wiper 108 and the normal contact of the bank to which this wiper has access. The magnet 105 upon energizing in this circuit opens its energizing circuit at its armature contacts and thereupon deenergizes, advancing the

wipers

108, 109, 110, 111, 112 and 113 of switch 100 to the Second position contacts of the respective banks to which they have access. As the second contact which wiper 108 engages is permanently connected to ground, the magnet 105 is reenergized and steps the wipers to the third set of contacts which are individual to the first trunk of the group of trunks to which switch 100 has access.

If the first trunk of the group is busy there will be a ground potential on the test terminal thereof appearing in the lowermost bank of the switch and the switch will therefore continue stepping until an idle trunk is found, upon the test terminal of which battery potential appears. When such an idle trunk is found a circuit is closed from battery through the contacts of sequence switch cam 202 (1} of the district selector 250 to which the first idle trunk extends, through the inner left hand armature and back contact of sleeve relay 226, over test conductor 114, wiper 108, conductor 107 left hand armature and front contact and left hand winding of relay 101, conductor 115 to ground through both wind ings of cut-off relay 102. Relay 102 is energized in this circuit and opens, at its lowermost armature and back contact and at its upper armature and back contact, the circuit previously traced through the winding of stepping magnet 105 and at its upper armature and front contact and at its up perinost lower armature and front contact extends the -onduttors 103 and 104 of the subscribeWs line to the

wipers

111 and 113 of the switch 100 and from thence to the trunk conductors 116 and 117 leading to the selected district selector. Relay 102 also its intermediate lower armature and front contact closes a circuit extending through the right hand winding of sleeve relay 226 of the district selector switch, the break con tacts of the left hand armature of slow releasing relay 227, the lower right hand contact of sequence switch cain 203 (1 to 2%) sleeve conductor 118, wiper 109, winding of marginal message register magnet 119, conductor 120, the intermediate lower armature and front contact of relay 102 and thence to ground through the upper Winding of relay 102. The sleeve relay 226 of the district selector switch energizes in this circuit but owing to its marginal nature the message register magnet 119 does not energize at this time.

For making the calling subscribers line ii busy to all calls incoming thereto, battery potential is connected to the multiples 1' test terminal 121 of the calling line apearing in the banks of all final selectors avine: access to this line, over conductor 'hrough wiper 110, segment 123 and Wiper 112 through the grounded segment 124L- prepares a circuit era-ending over conductor 125 to the back contact of the right hand armature of line relay 101'preparatory to restoring finder switch 100 to normal when the cut-off relay 102 ieconies deenergized upon the termination of the connection.

Upon the energization of sleeve relay 226, a circuit established for the line relay 228 of the district selector switch 250 which circuit extends from grounded battery through the right hand winding of this relay, the lower right hand contact of sequence switch cam 20 1-, conductor 22 the lower contacts of sequence switch cam 205, conductor 230 and thence to ground through the front contact and right hand armature of relay 226. At its inner left hand armature and back contact relay 226 opens the initial energizing circuit previously traced extending through the windings of relays 101 and 102 and at its left hand armature and front contact connects ground potential to the test conductor 11 1 of the selected trunk to mark the trunk busy to other line switches.

Relay 228 upon energizing closes a circuit for driving the sequence switch 200 of the district selector switch out of its normal position 1 and into position 2, this circuit extending from grounded battery through the winding of the driving magnet of switch 200, conductor 231, the upper left hand contact of sequence switch car .200 (1), the

I inner right hand armature and front contact of relay 228, and thence to ground at the lower right hand contact of sequence switch cam 207 (1 to 6). The sequence switch magnet energizes in this circuit and under the control of master earn 201 drives the sequence switch into position 2 in which position the circuit previously traced o'rer cam 202 is opened and a circuit is closed from grounded battery through the winding of relay 227, the upper left hand contact of sequence switch cam 208 (2 to 11) and thence to ground.

Relay 22'? upon energizing closes a lockingcircuit for the sleeve relay 226 extending through the right hand winding of relay 226 the malre contacts of the left hand armature of relay 227 and thence to the sleeve conductor 118 over the upper contacts of sequence switch cam 203 (1% to 16), this circuit being maintained through position 16 ofthe sequence switch or until relay 2'2? becomes deenergized. Upon reaching position 2 the sequence switcl connects a new holding ground to the test conductor 114: extending from conductor 11% over conductor 232 and through the upper right hand contact of sequence switch earn 208,

which holding ground is in a int ai nc d through position 18% of the sequence switch. 7

the interrupter contacts and winding of magnet 233, the upper left hand con tact of sequence switch earn 209 to 2) conductor 234iand thence to ground through the inner right hand arinature and front contact of relay 228 and the lower right hand contact of sequence switch cam 207 (1 to 6). VA circuit is also closed at this time through the winding of stepping magnet 238, the winding of cut-in relay 235 and thence to ground at the lower left hand contact of sequence switch cam 208 (2 to 11). Relay 235 does not energize at this time, however since its winding is shunted by ground connected through the armature of line relay 228.

As soon as sequence switch 200 leaves position 1, the initial energizing circuit of line relay 228 is opened at the lower right hand contact of sequence switch cam 20%, but this relay remains locked up over a circuit ex tending from grounded battery, its left hand winding its left hand armature and front contact, the upper left hand contact of sequence switch cam 210 (1 to 6), conductor 236, the lower righthand contact of sequence switch cam 211 (1 to 2 A) conductor 237 test wiper 238 of the sender finder switch SF and to ground on the contact with which the wiper 238 is in engage- This ci for step lishmh i in this manner the n'iafznct 2 33 adances the wipers of the tinder s-witch until an icie oi'iice sender is found t'hrn the wipcr 238 will find no ground on the terminals 'orrespond ng such idle sender and the 4 thereby arresting the stepping 1 of the switch F3, F and closes a. "it hand arn'iaiure and back i. it for driving sequence switch or position 2 and into position 3.

'cuit may he traced from grounded battery through the winding of the magnet of sequence switch 200, conductor 231, the unuer right hand contact of sequence switch rain the inner right hand armature and back contact of relay 228 and thence to grcuud at the lower right hand contact of sequence switch cam 20?. is soon as line relay 228 decnergizcs the shunt around the windi of relay 23:) is removed at the inner r' znt hand armature and, front contact of relay 228 and relay 235 thereupon energizes in series with stepping magnet 2:38, the current flowing through its circu t not be ing suiiicient to cause the eiuu'gization ol' the stepping magnet because of the high resistance of the winding of relay 285. Relay 235 upon energizing closes a circuit ex tending from ground through its inner left hand armature and front contact. over wiper 238 and the teniinal upon which it is resting, conductor 302 and thence to grounded battery through the winding of relay 803. Relay 303 energizes in this ircuit and at its armature and contact establishes a circuit for relay 301- which latter relay at its armatures and contacts closes an impulse circuit extending through the windings of the impulse relay and over the calling subscribers line loop This circuit may be traced from grounded battery through the left hand winding of rela) 305, the left hand armature and contact of relay 804;, conductor 306, wiper conductor 240, the upper left hand contact of sequence switch cam to 10 conductor 117, wiper 113 the upper armature and front contact of relay 102, conductor 10% thence over the subscribers line loop and returning over lilii conductor 103, the innermost lower armature of relay 102, wiper 111, conductor 110, the lower contact of sequence switch cam 213 (2 to 10 conductor 241, the outer left hand armature and front contact of relay 235, wiper 242, conductor 307, the right hand armature and contact of relay 304 and thence to ground through the right hand winding of impulse relay 305. Ground potential connected to the wiper 238 through the inner left hand armature and front contact of relay 235 also establishes a busy potential upon multiples of test conductor 302 to prevent other sender finders from selecting the sender which has now been taken for use by the calling subscriber. The calling subscriber now proceeds to dial the number of the desired line. Under the assumption that the subscriber desires a connection with the subscribers line which is listed in the directory as PENnsylvania 8432 and that this line is reached through a district selector switch 250, an incoming selector 450 and a iinal selector 550, the subscriber proceeds to dial three letters corresponding to the oiiice designation of the oflice in which the desired line is located and then. dials four digits representing the number of the line in such office. In the case assumed the calling subscriber will dial the letters PEN and then should dial the numerals 8432, but through inadvertence dials the numerals 8632. The three letters which represent the office code causes the setting of the code registers in the office sender in the manner fully set forth in the aforesaid patent to F. A. Stearn and F. J Scudder which, through the mechanism associated with the sender, controls the setting of the district selector switch 250 for extending the connection through the desired ofiice of exchange, in this case to an incoming selector in the subscribers own office.

The dialing of the numerals 8632 causes the setting of the numerical registers of the sender in the manner set forth in the aforesaid patent for controlling the setting of the incoming selector switch. 450 and the final selector switch 550. Following the setting of the code registers of the sender, the sender sequence switch 300 is moved from its normal position into position 2 in the manner set forth in the aforesaid patent, and the fundamental switch controlling circuit which extends from the sender to the selector switch 250 is closed at sequence switch cams 308 and 321. This circuit may be traced from grounded battery through the left hand winding of relay 228 of the district selector switch, the upper right hand and lower left hand contacts of sequence switch cam 210, conductor 243, the inner right hand armature and front contact of relay 235, the wiper 244 of the sender finder switch SF and the contact of the bank with which this wiper is associated, conductor 309, contact of sequence switch cam 308 (2),

back contact of the No. 0' counting relay 311, and thence to ground at the right hand contacts of sequence switch cam 321. The line relay 228 of the district selector switch and stepping relay 310 of the office sender both energize in this circuit.

Relay 228 upon energizing closes a circuit for driving sequence switch 200 out of position 8 and into position 4. This circuit extends from grounded battery through the magnet winding of the sequence switch 200, the upper left hand contact of sequence switch cam 206 (3), the inner right hand armature and front contact of relay 228 and thence to ground at the lower right hand contact of sequence switch cam 207 (1 to 6). With the district sequence switch 200 in position 4, a circuit is now closed for the updrive magnet 245 of the district selector, which circuit extends from grounded battery through the winding of magnet 245, the

upper right hand contact of sequence switch cam 209 (4), conductor 234, and thence to ground through the. inner right hand armature and front contact of relay 228 and the lower right hand contact of sequence switch cam 207. Magnet 245 upon energizing presses the depending portion of the switch shaft 246 against the constantly rotating updrive drum 247 thereby causing the upward movement of the switch shaft. Upon l the movement of the sequence switch 200 out of position 8, the initial energizing circuit of relay 228, which extends through its left hand winding and the upper right hand and lower left hand contacts of sequence 2' switch cam 210 is opened at the upper right hand cont-act of this sequence switch cam, but a locking circuit for relay 228 is closed through its left hand winding, its left hand armature and front contact, the left hand 1 contacts of sequence switch cam 210, and thence over the fundamental circuit as traced.

As the switch shaft of the district selector switch approaches its first brush tripping position, brush 252 engages the metallic portion of segment 249 of the commutator 251 and a circuit is closed in shunt of the wind ing of sender stepping relay 310, which may be traced from a point in the fundamental circuit between the winding of relay 228 and the windings of relay 310, through the upper contact of sequence switch 211 (3% to 4) conductor 248, brush selection segment 249 of the commutator 251, brush 252 carried upon the upper end of the switch shaft 246 and thence to ground at the lower left hand contact of sequence switch cam 214 (9 to 7 Upon the application of this shunt around the windings of stepping relay 310,

relay 310 deenergizes, relay 228, however, remaining energized over the shunt circuit just traced.

As the brush shaft 246 continues to move upwardly, the stepping relay. 310 will again become energized as soon as the brush 252 engages the first insulating portion of segment 249. The stepping relay 310 will then continue to be intermittently energized and deenergized as the switch shaft of the district selector moves upwardly until the sender has been satisfied with respect to the district brush selection condition which has been established at the sender by the par ticular code which the calling subscriber has registered. lVhen the sender is satisfied, the No. 0 counting relay 311 becomes energized and locked up through the winding of the No,- 0 counting relay 313 over a circuit extending from grounded battery through the winding of relay 813, the winding of relay 3-11, the armature and front contact of relay 313, and thence to ground at sequence switch contact 815 in the manner well known in the art and set forth in detail in the P tent. hereinbefore referred to. Relay 311 upone-nergizing closes a circuit for driving sequence switch 300 out of position 2 and into position t which may be traced from grounded battery through the winding of the magnet of sequence switch 300, sequence switch contact 314 and thence to ground at the right hand armature and front contact of relay 311. At its left hand armature and back contact, relay 311 opens the fundamentalcircuit previously traced through the windings of relays 310 and 228. When sequence switch 800 leaves position 2, the looking circuits of all counting relays which have been energized are opened at sequence switch cam 315 and these relays deenergize.

As soon following the opening of the fundamental circuit by the No. 0 counting relay 3 11 as the brush 252 engages the next insu- 'lati-ng portion of segment 249, relay 228 be comes deenergized, closing a circuit for driving the district selector sequence switch 200 out of position at and into position 5. This circuit extends from grounded battery through the winding of the magnet of sequence switch200, the upper right hand contact of sequence switch cam 206 (4), the inner right hand armature and back contact of relay 228 and thence to ground at the 7 lowerright hand contact of sequence. switch cam 207. As soon as relay 228 deenergizes, the circuit previously traced through the updr ve magnet 245 1s opened at the inner right 7 hand armature and back contact of relay 228.

lVith sequence switch 200 of the district selector in position 5 and the sender sequence switch 200 in position 4:, the fundamental circuit previously traced is againestablished V and relay 228 of the district selector and stepping relay 310' of the sender again energize. Relay 228 upon energizing causes the movement of the district selector sequence switch 200 from position 5 into position (i, the sequence switch magnet 200 being cncrgized over a circuit extending over conductor 23]., the upper left hand contact of sequence switch 206 the inner right hand armature and front contact of relay 22S, and thence to ground at the lower right hand contact of sequence switch cam 207. As soon as sequence switch 200 leaves position 5, the initial energizing circuit of relay 228. which is closed over the fundamental circuit through the upper right-hand contact of scquence switch cam 210 (5), and the lower lefthand contact of cam 210 (3 to (3) is opened, but relay 22S remains locked up through its left hand winding, its left hand armature and front contact and the left hand contacts of sequence switch cam 210.

Upon reaching position (3, the circuit previously traced for the updrive magnet 245 is again established through the upper right hand contact of sequence switch 200 (6) and the inner right hand armature and front contact of relay 228, and in the manner previously described, the switch shaft 24-6 is again driven upwardly. Since at this time the tripping spindle 292 has been rotated by the trip magnet 253, which was energized in position 5 of sequence switch 200 over a circuit extending from grounded battery through the winding of magnet 253 and to ground through the lower right hand -ontact of sequence switch 208 (5 to 7), the first set of brushes is now tripped upon the initial upward movement of switch shaft 246 and during the continued upward movement of the switch shaft. the tripped set of brushes travels over the contacts of the bank with which they are associated. The remaining four sets of brushes not being tripped are funciionless at this time. During the continued upward movement of the switch shaft and as the tripped set of brushes approaches the first group of contacts in the bank. brusn 256 engages the metallic portion of the group selection segment 25:) of the commutator and a circuit in shunt of the windings of sender stepping relay 310 is established. extending from grounded buttery through the left hand winding, the left hand armature and front contact of relay 228, the upper left hand and lower right hand contacts of sequence switch cam 210, conductor 254-. segment brush 256 and thence to ground at the lower contact of sequence switch cam 2M (9 to 7). Further upward. movement of the switch shaft advances the brush 2:76 into engagement with an insulating portion of segment 255 thereby removing the shunt from around the windings of stepping relay 310. The intermittent connection of this shunt around the windings of stepping relay 31.0 causes the intermittent energization and deenergif ll llfi

zation of stepping relay 310 which, in the well-lrnown manner, causes the successive energization of counting relays associated with the sender.

hen the sender has been sat-is? ed with respect to the district group selection cont the contact of sequence switch cam 3153 Upon the energization of relay 311, the circuit previously traced through the magnet winding ot sequence switch 300 is again established and the sequence switch 300 is driven out of position 4 and into position (3. Atits left hand armature and back con tact relay 81.1 opens the fundamental circuit thereby causing the deenergization ot relays 310 and 22 As soon as sequence switch 300 leaves position 4t, the lockh circuits oi the energized counting relays a opened at the sequence switch cam P 7 these relays deenergize'. As soon tonowing the opening of the fundamental c cuit as the brush 256 engages the nest portion of commutator segment 228 deenergizes opening at its inner hand armature and trout contact the circuit previously traced extending through the winding of the updrivc magnet 25 thereby arrestin the upward movement of he switch shaft 101' positioning the tripped set ot brushes in engagement with the l" set of terminals of the selected group.

its inner right hand armature and bat-l; con

tact relay 228 closes a circuit or a through the upper right hand contact sequence switch cam 206 for driving scquence switch. 200 out of position 6 and into position 7. In position 7 relay encrgiiws over a circuit extending from grounded battery through its right hand winding, the lower right hand contact of sequence cam 2041; (7 to 71;) conductor 229, the lower contacts of sequenceswitch cam 205 and to ground at the right hand arinztture :lront contact of sleeve relay 226, El:

upon energizing, closes a circuit driving sequence switch 200 out ot position 7 and into position 8. This circuit may be traced troin grounded battery throu 'h the magnet winding of the sequence switcu, conductor 281, the upper lett hand coat ot sequence switch cam 206 (7), the inner right hand armature and front contact ot relay 228., the upper left hand contact ot s 'aequence switch cam 20? (7 to 8) a id thence to ground through the malre con s ot the ht hand armature of relay 221.

As soon as sequence switch 200 leares position 7, the initial energizing circuit of relay 228 is opened at sequence switch cam 204, but relay 228 locks up over a circuit extending from grounded battery tl'iro-ugh its left hand winding, its left hand armature and trout cont-act, the upper contacts of sequence switch 215 to the test brush 257, and it the first trunk of the selected group is busy to ground at the test terminal of this trunk. Upon reaching position 8 with relay 228 energized, a circuit is established for the updrive n'iagnet 245 which may be traced from grounded battery through the magnet 245, the upper right hand contact of sequence switch cam 209 (8), the inner right hand armature and front contact of relay 228 and to ground at the lower right hand contact of sequence switch cam .207. The llpt'll'llfl n'iagnet 245 upon energizing again drives the switch shaft upwardly in search of an idle trunk in the selected group. So long as the test brush 257 encounters the terminals 01" busy trunks, relay 228 remains locked up. When, however, an idle trunk is encountered which it will be assumed. the trunk terminating in

terminals

258, 259 and 260, the locking circuit of relay 228 is opened and relay 228 deenergizes as soon as the

brushes

257, 263 and 264 have been properly centered upon

bank terminals

259, and 200. Until the brushes are so centered relay 228 remains locked up over a circuit extending through its right hand winding, the lower left hand contact oi sequence switch cam 204 (8), conductor 286, centering segment 28?, brush 288, the lower left hand contact of cam 209 (8), conductor 284-, the inner right hand armature and, front contact of relay 228 to ground at the lower right hand contact of sequence switch ram 207 (7-3,- to 16).

Relay 228 upon dee-nergizin opens the circuit previously traced through the winding of the updrire magnet 24-5 thereby arthe upward movement ot' the switch shaft 2% and closes a circuit extending through its inner right hand armature and back contact 0 sequence switch cam 206 (8) for driving sequence switch 200 out of position 8 and into position 9. Upon reaching position busy ground potential is connected to the multiple test terminals of the selected trunk over brush 257 and the right hand contacts of cam Relay 228 again euergirws when sequence switch 200 reaches p ion 9 over a circuit extending through its right hand winding, the lower right. luind contact of sequence switch cam 204; (9 to 10), conductor the lower left hand and upper right hand contact 01? sequence switch 205 and to ground at the right hand aiimature and front contact of relay r Relay 261 is at this time energized oyer a circuit extending from grounded batvery through its winding, the upper left nd contact of sequence switch cam 216, a 10), the outer right hand armature and 7 tact for driving sequence switch 200 out of position 9 and into position 10, in which position the fiiindamental circuit is extended through contacts of

sequence switch cams

218 and 219 over brushes 263 and'264 of the 51? district selector switch to the line relay 421 of the incoming selector switch 450. This circuit may be traced from grounded battery through the right hand winding of relay 421, conductor 422, the upper contacts of sequence switch cam 402, conductor resistance element 424, the upper contact of sequence switch cam 403 (1 to 10) trunk conductor 419, bank teri'ninal 260 and brush 263 of the district selector switch 250, the upper right hand and lower left-hand con-- tacts'of sequence switch spring 218, conductor 264, conductor 243, the inner right hand armature and front contact of relay 235, wiper 244, conductor 809, the contact of sequence switch cam 308 (6), the windings of overflow relay 318 and sender stepping relay 31.0, the armature and back contact of counting relay 311, the upper contacts of sequence switch cam 321, conductor 312,

" wiper 265, conductor 266, the lower left hand and upperg right hand contacts of sequence switch cam 219, brush 264 and banl: terminal 259 of district selector switch 250, trunk conductor 420, the lower contact of sequence switch cam 404 (1 to 10), resistance element 425, conductor 426, and thence to ground through the lower contact of sequence switch cam 405 (1 to 8). Bela- 7421 energizes in this circuit and at its outer left hand armature and front contact closes a circuit for driving sequence switch 400 out of'its normal position 1 and into position 2, this circuit extending from grounded battery through the winding of the driving magnet of sequence switch 400, the lower right hand contact of sequence switch cam 406 (1), the outer left hand armature and front contact of relay 421, conductor 427 and thence to ground at the lower contact of sequence switch cam 407 (1 to 10). As soon as sequence switch 400 leaves position 1, the initial energizing circuit of relay 421 is opened at the upper left hand contactof sequence switch cam 402, but relay 421 remains energized over the fundamental circui-t through a locking branch of the funda mental circuit which may be traced from grounded battery through the right hand winding of relay 421, the right hand c011- tacts of sequence switch cam 402, conductor 428, the right hand armature and front conhand contacts of sequence switch earn 408 (1 to 4) and thence over the fundamental circuit as previously traced.

In position 2 of sequence switch 400, a circuit is closed for the updrive magnet 430 which may be traced from grounded battery through the winding of this magnet, the upper right hand contact of sequence switch cam 409 (2), conductor 43.1, the outer left hand armature and front contact of relay 421 and thence to ground at the lower contact of sequence switch cam 407. Magnet 430 upon energizing presses the depending portion of the switch shaft 432 against the constantly rotating updrive drum 433 causing thereby the upward movement of the switch shaft. As the shaft of the switch approaches its first brush tripping position, brush 436 engages a metallic portion of the brush selection segment 434 of the commutator and a circuit is closed in shunt of the stepping relay 310 of the ofiice sender, which may be traced from grounded battery through the right hand winding of relay 421, conductor 422, the right hand contacts sequence switch cam 402, conductor 428, the right hand armature and front contact of relay 421, conductor 429, the upper left hand contact of sequence switch cam 408 (1 to 4), the lower right hand contact of sequence switch cam 408 (1?,- to 2) segment 434, brush 436, conductor 437 and thence to ground at the lower contact of sequence switch cam 410 (7 to 5). Upon the establishmcnt of this shunt, relay 421 is maintained energized over the shunt and stepping relay 310 deenergizes. As the switch shaft 432 continues in its upward movement, the brush 436 engages an insulating portion of the segment 434 and the previously traced shunt is opened, whereupon stepping relay 310 again energizes. In this manner as the switch shaft 432 moves upwardly the stepping relay 310 of the oflice sender is intermittently energized and deenergized to successively energize and lock up counting relays associated with the sender, all in the well known manner.

It has been assumed that the calling subscriber has dialed No. 8632 and that, therefore the numerical registers of the sender have been set to register this number. The No. 4 counting relay was therefore energized upon the initial cnergization of stepping relay 310 when the fundamental circuit was first extended through the winding of line relay 421 of the incon'iing selector switch. Therefore when the switch shaft 432 of the incoming selector switch has moved upwardly to such an extent as to position the fifth set of brushes thereon in such a relation to the tripping spindle 439 as to later cause the tripping of this particrsoaaae ular set of brushes, the counting relays succeeding the No. 4 counting relay will have become energized and locked up and the No. 0 counting relay 311 will open the fundamental circuit at its left hand armature and back contact. At its right hand armature and front contact, relay 311 establishes the previously traced circuit for driving sequence switch 300 out of position 6 and into position 8. When the sequence switch leaves position 6, the locking circuits of the energized counting relays are opened at sequence switch cam 315 and the counting relays deenergize.

As soon following the opening of the fundamental circuit by the No. 0 counting relay 311 as the brush 436 engages the next insulating portion of commutator segment 434, line relay 421 becomes deenergized, opening at its outer left hand armature and front contact the circuit of the updrive magnet 430 thereby arresting the upward movement of the switch shaft 432, and at its inner left hand armature and back contact closing a circuit for driving sequence switch 400 out of position 2 and into position 3. This circuit may be traced from grounded battery through the magnet winding of sequence switch 400, the upper left hand contact of sequence switch cam 406 (2) and thence to ground at the inner left hand armature and back contact of relay 421. Upon reaching position 3 sequence switch 400 closes a circuit for the tripping magnet 438 extending from grounded battery through the magnet winding 438 and thence to ground through the right hand contacts of sequence switch cam 405. Magnet 438 upon energizing rotates the tripping spindle 439 into such a position as will trip the selected set of brushes, which in the case assumed is the fifth set of brushes, upon the subsequent upward movement of the switch shaft 432.

Upon reaching position 3 the fundamental circuit extending through the winding of relay 421 and the windings of stepping relay 310 and overflow relay 318 is again established over the circuit previously traced. Relay 421 upon energizing in this circuit again closes the circuit previously traced for driving sequence switch 400 out of position 3 into position 4 and at its right hand armature and front contact closes the locking circuit previously traced for maintaining itself energized over the fundamental circuit after the sequence switch 400 leaves position 3. With sequence switch 400 in position 4 and relay 421 energized, the circuit previously traced through the updrive magnet 430 is again closed and the switch shaft 432 is again driven upwardly. During the initial upward movement of the switch shaft the fifth set of brushes is tripped by the tripping spindle 439 and during the subsequent upward movement of the switch shaft the tripped set of brushes travels in engagement with the terminals of the bank with which they are associated, and as the brush shaft of the selector switch moves the tripped set of brushes into engagement with the lowermost group of terminals in the bank, brush 441 engages the metallic portion of the group selection seg ment 440 of the commutator 435 and a circuit is closed in shunt of the windings of sender stepping relay 310 which may be traced from grounded battery through the right hand winding of relay 421, conductor 422, the right hand contacts of sequence switch cam 402, conductor 428, the right hand armature and front contact of relay 421, conductor 429, the upper contacts of sequence switch cam 408, commutator segment 440 brush 441, conductor 437 and thence to ground at the lower contact of the sequence switch cam 410 (7 to 5). Relay 421 is maintained energized over this shunt circuit, but stepping relay 310 'deenergizes. As the switch shaft 432 continues in its upward movement, the brush 441 engages an insulating portion of segment 440 and the shunt circuit is opened and stepping relay 310 again energizes. In this manner. as the switch shaft 432 continues its upward movement, the stepping relay 310 of the sender is intermittently energized and deenergized.

At this time the thousands and-hundreds numerical registers of the sender are so set as to provide a circuit for the No. 1 counting relay, which circuit is completed upon the first energization of stepping relay 310 at the time relay 310 energizes in series with relay 421 at the beginning of the group selection movement of the incoming selector switch. Therefore when the switch shaft of the incoming selector switch is moved up wardly to such an extent as to position the tripped set of brushes upon the first contact of the second group of the bank, the No. 0

counting relay 313 will become energized establishing a locking circuit for itself through the winding of No. 0 relay 311. The No. 0 relay 311 upon energizing opens the fundamental circuit at its left hand armature and back contact and at its right hand armature and front contact closes the circuit previously traced for driving sequence switch 300 out of position 8 and into position 10. When the sequence switch leaves position 8, the locking circuits of the energized counting relays are opened at the contact of sequence switch cam 315 and these relays deenergize.

-As soon following the opening of the fundamental circuit by the No. 0 counting relay 311 as the brush 441 engages the next insulating portion of the commutator segment 440, relay 421 of the incoming selector switch deenergizes and opens the circuit previously traced through the updrive magnet"43t)"thereby: arresting the upward movement of the switch shaft. At its inner left hand armature and back contact relay 421 closes a circuit extending through the winding of the driving magnet of sequence switch 400 and'the upper left hand contact of sequence switch cam 406 (4) for driving the sequence switch out of position 4 and into position 5. In position 5 relay 421 is again energized by a circuit extending from grounded battery through its left hand winding and thence to ground through the right handcontacts of sequence switch cam 411. Relay 421 now closes a circuit extending from ground at

sequence switch cam

407 and 7 through the outer left hand armature and front contact of relay 421 for driving sequence switch 400 out of position 5 and into position 6. Upon leaving position 54 the initial energizing circuit extending through the winding of relay 421 is opened at sequence switch cam 411, but relay 421 remains energized over a locking circuit extending from grounded battery through its right hand winding, the right hand contacts of sequence switch cam 402, conductor 428, the right hand armature and front contact of relay 421, conductor 429, the right hand contacts of sequence switch cam 412 and thence to the test brush 442 and to ground at the test-terminal of the first trunk of the group to which the tripped set of brushes hasacces's, if the first trunk of the group is at the time busy.

With sequence switch 400 in position 6 and relay 421 locked. up over the circuit traced through the test brush 442, a circuit is closed for the updrive magnet 430 as previouslytraced for driving the switch shaft upwardly in its trunk-hunting movement. This movement will continue so long as the test brush 442 encounters ground potential on the test terminals of the trunks of the group over which this brush moves. Then, however, an idle trunk is found which, it will be assumed is the trunk terminating in the

bank terminals

447, 449, 451, the locking circuit of relay 421 will be opened and since the initial energizing circuit of relay 421 was opened as soon as the sequence switch moved out of position 5 1-, relay 421 will deenergize thereby opening at its inner left hand armature and front contact the circuit of the updrive magnet 430. To insure, however, that the brushes shall be properly centered. on the terminals of the selected idle trunk, relay 421 is maintained energized to maintain the circuit of the updrive magnet 430 until the brushes are so centered, by an' additional'locking circuit extending from grounded battery through the left hand winding of relay 421, the upper right hand and lower left hand contacts of sequence switch cam 411, conductor-448, centeringcommutator segment 444, brush 445, conduc- 7 tor 437, the upper left hand contact of sequence switch cam 410 (6), conductor 431, the outer left hand armature and iroi'it contact of relay 421 and thence to ground through the sequence switch cam 4th" (1 to 10).

Upon the deenergization of relay 421 5clowing the centering of the brushes upon the terminals of the selected idle trunk, the circuit previously traced is again closed for driving the sequence switch 400 out of position 6 and into position 7. In position 7 relay 421 again energizes in a circuit extending through its left hand winding and the right hand contacts of sequence switch cam 411 and closes a circuit for driving the sequence switch out of position I and into position 8, in which position the tip couductor of the fundamental circuit is extended through the resistance element 424, the upper left hand contact of sequence switch cam 413 (8), brush 446 and bank terminal 447 of the incoming selector switch 450, trunk conductor 517, the lo wer left hand contact of sequence switch cam 502 (15 to (3), the lower left hand contact of sequence switch cam 503 (1), the right hand winding of relay 518 and thence to grounded battery through the upper left hand contact of sequence switch cam 504 (l to 10). ring conductor of the fundamental circuit extends as previously described over conductor 426 to ground at the lower right hand contact of sequence switch cam 41 5 (1 to Upon the extension of the connection to the final selector switch, relay 421 of the incoming selector switch which was energized in position 7 of sequence switch 401) is innintained energized in position 8 oi the sequence switch 400, over a circuit extending from grounded battery through the right hand winding of relay 421. conductor 422, the right hand contacts of sequence switch ram 402, conductor 428, the right hand armature and front contact of relay 421, czniduclor 429, the lower right hand contact of sequence switch cam .14 (7 to 8), brush 448 and terminal 449 of the incoming selector switch, trunk conductor 519. the upper left hand and lower right hand contacts of scquence switch cam 505, resistance element 520 and thence to ground through the lower left hand contact of sequence switch cam 5 6 (1 to 83;). Busy ground potential is placed on the multiples of test terminal 451 of the selected trunk over test brush 442 and the lower right hand and upper left hand contacts of sequence switch cam 412.

Upon the extension of the fuiulauicntal circuit to the final selector switch 550, with the sender sequence switch 300 in position 10, relay 518 of the final selector and stepping relay 310 of the otlice sender energize. Relay 518 upon. energizing closes a circuit for relay 521 which may be traced from The grounded battery through the left hand winding of this relay, conductor 522, the upper left hand contact of" sequence switch cam 507 (1), conductor 523, the left hand armature and front contact of relay 518 and thence to ground through the upper contact of sequence switch cam 508 (1 to 11). Relay 521 energizes in this circuit and at its left hand armature and front contact closes a locking circuit for itself extending from grounded battery through its left hand winding through the armature and back contact of test relay 5241, the left hand armature and front con tact of relay 521, sleeve conductor 525 of the trunk circuit extending back to the in coming selector switch, bank terminal 151 and brush 1 12 of the incoming selector switch and thence to ground at sequence switch cam 4:12. Relay 521 upon energizing also closes a circuit for driving sequence switch 500 out of its normal position 1 into position 2, which circuit may be traced from grounded battery through the winding of the magnet of sequence switch 500, through the lower contacts of sequence switch cam 509 and to ground at the right hand armature and front contact of relay 521. When sequence switch 500 moves out of position 1, the initial energizing circuit of relay 518 is opened at the lower left hand contact of sequence switch cam 503, but relay 518 remains energized over the fundamental circuit by reason of a locking circuit extending from grounded battery through the left hand contact of sequence switch cam 504;, the right hand winding of relay 518, the lower right hand contact of sequence switch cam 510 (15 to 10), the right hand armature and front contact of relay 518, the lower right hand contact of sequence switch cam 503 (1 to 6) and over the fundamental circuit as previously traced.

Relay 518 upon energizing, with sequence switch 500 in position 2, closes a circuit for the high speed updrive magnet 526 which may be traced from grounded battery through the upper right hand contact of sequence switch cam 511 (2), conductor 523, the left hand armature and front contact of relay 518 and thence to ground at the upper left hand contact of sequence switch cam 508. Magnet 526 upon energizing presses the depending portion of the switch shaft 527 against the constantly rotating high speed drum 528 thereby causing the witch shaft to be moved upwardly at a high speed in its brush selection movement. its the brush shaft approaches its first brush tripping position, brush 532 engages the metallic portion of the brush selection commutater segment 530 of the commutator 531 and circuit is closed in shunt of the windings of the sender stepping relay 310, which may be traced from grounded battery through the left hand contact of sequence switch cam 504, the right hand winding of relay 518, the lower right hand contact of sequence switch cam 510 (15 to 10), the right hand armature and front contact of relay 518, the lower right hand contact of sequence switch earn 503 (1 to 6), the upper right hand rontact of sequence switch cam 502 (1%- to 2), conductor 529, commutator segment 530, brush 532, conductor 533 and thence to ground through the upper left hand contact of sequence switch cam 506 (13 to 11). Upon the establishment of this shunt circuit relay 518 at the final selector switch is maintained energized, but stepping relay 310 of the oilice sender deenergizes.

As the switch shaft 52? continues in its upward movement, the brush 532 advances into engagement with an insulating portion of the commutator segment 530 and the shunt circuit previously traced is opened, whereupon sender stepping relay 310 again energizes. In this manner as the switch shaft 527 continues its upward movement, stepping relay 310 of the Office sender is intermittently energized and deenergized.

On the initial closure of the fundamental circuit through the winding of relay 518 and the windings of stepping relay 310,

with the sender sequence switch 300 in p0 sition 10, and under the assumption that the calling subscriber has set the hundreds register of the sender in position six, a circuit is closed in the well lrnown manner for the No. 1 counting relay. in response to the intermittent cnergization and deenergization of sender stepping relay 310, the counting relays eer 'ize and. lock up in succession in the well known manner until the No. 0 counting relay 313 becomes en ergized, when an energizing circuit for the No, 0 counting relay 311 is established, eX tending from grounded battery through the. windings of relays 313 and 311, the armature and front contact of relay 313 and thence to ground through the contact of sequence switch cain 315 (10). Counting relay 311 upon energizing closes a circuit at its right hand armature and front contact, extending tl'n'ough the contact of sequence switch cam 314: 10) for driving sequence switch 300 out of position 10 and into position 12. When the sequence switch leaves position 10, the locking circuits of the enercounting relays are opened at se quence switch cam 315 and these relays deenergize. At its left hand armature and back con act relay 311 opens the fundamental circuit previously traced through the windings of stepping relay 310 and relay 518 of the final. selector switch.

As soon following the opening of the fundamental circuit as the brush 532 engages the next insulating portion of the commutator segment 530, relay 518 becomes deenergizcd and at its left hand armature and front contact opens the energizing circuit of the updrive magnet to arrest the upward movement of the switch shaft. At itsleft hand armature and back contact relay 518 closes a circuit for driving sequence switch 500 out ofposition 2 and into position 3, this circuit extending from grounded battery through the winding of the sequence switch magnet'500 the upper right hand contact of sequence switch cam 512 (2). the left hand armature and back contact of relay518 and thence to ground at the upper contact of sequence, switch cam 508. The second set of brushes has now been positioned with relation to the tripping fingers of the tripping spindle 53%- so that upon a subsequent upward n'ioven'ient of the switch shaft this set of brushes will be tripped for engagement with the bank of one hundred termi ials with which this brush set is associated'. To cause the tripping of this set of brushes the tripping magnet 535 is energized as soon as sequence switch 500 reaches position 3, over a circuit extending from grounded battery through the tripping magnet 5 35 and thence to ground at the lower right hand contact of sequence switch 506 (3 1305). hen sequence switch 500 reaches position 3, the energizing GHCUit' of relay 518 is again established over the fundamental circuit as previously described and relay 518 and stepping relay 310 of the ofiice sender again energize. Relay 518 upon energizing closes the previously traced circuit for driving sequence switch 500 out of vposition 3 and into position 4. With sequence switch 500 in position 4, the previously traced circuit for the updrive magnet 526 is again established at the left hand armature and front contact of relay 518. Relay 518 also establishes the previously traced locking circuit for itself extending through its right hand armature and front contact for maintaining itself energized over the fundamental circuit after the sequence switch 500 leaves position 3 and the initial energizing circuit is opened at the lower lefthand contact of sequence switch cam 503.

Upon the energization of updrive magnet 526 the switch shaft 527 is driven upwardly in its group selection movement and during the initial portion of this movement the second set of brushes is tripped by a finger of the tripping spindle 534. During the remainder of the group selection movement, the tripped set of brushes then travels upwardly in contact with the terminals of the bank with which they are associated. As the tripped set of brushes approaches the lowermost set of contacts of the first group in the bank, brush 538 engages a metallic portion of the group selection commutator segment 537 of the commutator 531 and a circuit is closed in shunt of the windings o f the sender stepping relay 310 which may be traced from grounded battery through the left hand contact of sequence switch cam 504- (1 to 10), the right hand winding of relay 518, the lower right hand contact of sequence switch cam 510 to 10), the right hand armature and front contact of relay 518 the right hand contacts of snquence switch cam coi'idurtor 5130. coininutator segment 53?, brush Z388. conductor 533 and thence to ground at the upper left. hand contact of sequence switch ll'l sec (13 toll). Relay 518 at the final selector switch is maintained energized over this shunt circuit but the sender stepping relay 310 becomes deenergized so longas the shunt circuit is maintained.

As the switch shaft 527 continues in its upward movement the brush 538 engages an insulating portion of the commutator segment and the previously traced shunt circuit is opened and stepping relay 310 of the sender again energizes. lfn this manhe): as the switch shaft continues its upward u'iovenient. the sender stepping relay 310 intermittently energizes and deenergizes.

Upon the initial energization of sender stepping relay 310 with the sender sequence switch 800 is position 12, it being assumed that the calling subscriber has set the tens register upon its third position contacts, a circuit was established for the No. 3 counting relay in the well known manner. In response to the intermittent operation of the sender stepping relay 310, the counting relays energize and lock up in succession until the No. 0 counting relay 31; becomes energized, when a locking circuit is established through its winding, the winding of No. 0 counting relay 311, the armature and front contact of relay 313 and to ground at the contact of the sequence switch cam 315 (12). Relay 2311 upon energizing closes a circuit extending through its right hand armature and contact, the contact of Stfqlltlllu switch cam err (12), and through the winding ofthe magnet of sequence switch 300 for driving sequence switch 300 into position 14. At its left hand armature and back contact counting relay 311 opens the fundamental circuit previously traced through the windings of sender stepping relay 310 and the winding of relay 518 at the final selector switch.

As soon following the opening of the fundamental circuitas brush 538 engages the next insulating portion of commutator segment 537, relay 518 becomes deenergized and opens the circuit previously traced through the winding. of the updrive magnet 52th and closes the circuit previously traced for driving sequence switch 500 out of position 4; and into position 5. In position 5 the fundamental circuit extending through the wind mgs of stepping relay 310 and the right hand winding of relay 518 is again established. Relay 518 upon energizing closes the previously traced locking circuit for itself and closes a circuit for driving sequence switch 500 out of position 5 and into position 6. Upon reaching position 6, a circuit is established for low speed updrive magnet which circuit may be traced from grounded battery through the winding of magnet 539, the lower left hand contact of sequence switch cam 50'? (6), conductor 523, the left hand armature and front contact of relay 518 and thence to ground at the upper left hand contact of. sequence switch cam 508.

The low speed updrive magnet 539 upon energizing presses the depending portion of the switch shaft 527 against the constantly rotating low speed drum 540 thereby causing the upward movement of the switch shaft in its units selection movement.

As the tripped set of brushes approaches the first set of terminals in the selected group the brush 532 engages a metallic portion of the units selection portion of commutator segment 530 and circuit is closed in shunt of the windings of sender stepping relay 310, which may be traced from grounded battery through the left hand contact of sequence switch cam, 504 (1 to 10) the right hand winding of relay 518, the lower right hand contact of sequence switch cam 510 (15 to 10), the right hand armature and front contact of relay 518, the lower right hand contact of sequence switch cam 503 (1 to 6), the upper right hand contact of sequence switch cam 502 (5%}; to 6), conductor 529, commutator segment 530, brush 532, conductor 533 and thence to ground at the upper left hand contact of sequence switch cam 506. Relay 518 is maintained. energized over this shunt circuit but sender stepping relay 310 deenergizes As the switch shaft 527 continues its upward movement, brush 532 comes into engagement with an insulating portion of the commutator segment 530 and the previously traced shunt circuit is opened, whereupon the sender stepping relay 310 again energizes. In this manner during the continued upward movement of the switch shaft the sender stepping relay 310 inter mittently energizes and deenergizes.

Upon the initial closure of the fundamental circuit for controlling the units selection movement of the final selector switch with the sender sequence switch 300 in position 14 and, under the assumption that the calling subscriber has set the units register upon its fifth position terminals, a circuit is established in the well known manner for the No. 2 counting relay. In response to the intermittent operation of relay 310, the counting relays energize and lock up in succession until the No. 0 counting relay 313 becomes energized, when a locking circuit is established for this relay as previously traced through the winding of the No, 0 counting relay 311. Relay 311 upon energizing closes the previously traced circuit extending through the contact of sequence switch cam 314 for driving the sender sequence switch 300 out of position 14 and into position 16. At its left hand armature and back contact relay 311 opens the fundamental circuit previously traced through the windings of sender stepping relay 310 and theright hand winding of relay 518 at the final selector switch. As soon following the opening of the fundamental circuit as the brush 532 engages the next insulating segment of commutator 530, relay 518 becomes deenergized and thereupon opens the circuit of the updrive magnet 539 to arrest the upward movement of the switch shaft and closes the previously traced circuit for driving sequence switch 500 out of position 6 and into position 9.

The brushes of the final selector switch 550 have now been positioned upon the bank terminals which are numbered 8632. With the sequence switch 500 in position 9, a cirsequence switch cam 504 (1 to 10), the right hand winding of relay 518, the lower right hand and upper left hand contacts of sequence switch cam 510 and thence to ground at the right hand armature and front contact of relay 521. Relay 518 upon energizing closes a locking circuit for itself extending from grounded battery through its right hand winding, the lower right hand contact of sequence switch cam 510 (15 to 10), the right hand armature and front contact of relay 518 and thence to ground through the upper contacts of sequence switch cam 513 (9 to 10). This locking circuit will be maintained through position 10 of sequence switch 500. Relay 518 upon energizing also closes a circuit as previously traced for driving sequence switch 500 out of position 9, and the switch will continue to advance underthe influence of its master cam 501 through intermediate positions into position 12. Upon reaching position 10 a new holding circuit is established for relay 518 extending from grounded battery through the left hand winding of relay 518, the lower right hand contact of sequence switch cam 515 (10 to 11), the left hand armature and front contact of relay 518 and thence to ground at the upper left hand contact of sequence switch cam 508. Upon reaching position 11 sequence switch 500 establishes a new holding circuit for relay 518 extending from ground through the winding of test relay 524, conductor 541, the upper left hand contact of sequence -";terininals 562, 563 and 564.

switch cam 502 (11 to 13), the lower left hand contact of sequence switch cam 503 (11 to 13), the right hand winding of relay 518, the upper right hand contact sequence switch cam 510 (11 to 12: the right hand armature and front contact of relay 518, the right hand contacts of sequence switch cam 513, test brush 542 and thence to grounded battery on the test terminal 560of'the set of terminals upon which the tripped set of brushes of the final selector switch has been set. It is to be noted in this connection that all blank bank terminal sets will be grouped together and, with the exception of the last terminals of the group, which are connected to trunks extending to an intercepting operators position, all test terminals will be permanently connected to grounded battery over conductor 561 and through resistance elements 600 and601. The battery potential supplied to these test terminals will be re duced since it is applied through both re sistance elements 600 and 601.

The current now flowing over the locking circuitof relay 518 and through the winding of relay 524 is not sufiicient to energize relay 524 since this relay is marginally wound, but the current is sufficient to maintain the energizationof relay with sequence switch 500 in position 12, test relay 524 deenergized and relay 518 energized, acircuit is now established for the updrive magnet 539 which may be'traced from grounded battery through the wind mg of magnet 539, the lower left hand contact of sequence switch cam 507 (12) conductor 523, the left hand armature and front contact of relay 518, the lower left hand contact of sequence switch cam 508 12) and thence to ground at the right hand armature and front contact of relay 521. The 'energization of the updrive magnet 539 causes the switch shaft 52? to be moved upwardly in a hunting movement. hen the test brush 542- encounters the next test terminal which test terminal corresponds to a second set of blank terminals and is therefore multipled to the conductor 561, the line relay 518 is maintained energized and sufficient current does not flow to energize relay 524 and therefore the switch shaft continues-to move upwardly until the brushes'of the switch encounter the set of This set of terminals is shown connected to the first of a group of trunk lines extending to an intercepting operators position. It will be assumed that'this trunk line is in use on another intercepted call and that therefore busy battery potential is connected to the test terminal 564 of this trunk over a circuit which maybe traced from grounded battery through the contacts of sequence switch/cams of the other final selector switch which has been set upon multiple terminals of the trunk hne, correspondmg to

cams

504 and 513, the test brush of su h other selector and to the multiple of termi nal 564. Since however the multiple of terminal 564 is at this time connected over sleeve conductor 604 of the first trunk of the group through the low resistance wind ing of relay 602 to ground, the greater por tion of the current is diverted through the movement over the terminals of succeeding trunk lines of the group terminating in the intercepting operators position.

)Vhen the test brush 542 encounters test terminal 567 which it will he assumed is the test terminal of the last and idle trunk line extending to the intercepting operator's position, ground potential will be encountered on this test terminal and the circuit previously traced through the winding of relay 518 and the winding of test relay 524 will he. opened. Relay 518 will thereupon deener glze opening the circuit of the updrive magnet and closing a circuit for driving sequence switch 500 out of position 12 and into position 13, this circuit extending from grounded battery through the upper right hand contact of sequence switch cam 512 (12), the left hand armature and back contact of relay 518, the lower left hand con-- tact of sequence switch cam 508 (12) and thence to ground at the right hand armature and front contact of relay 521..

To insure that relay 518 will not deenergize upon brush 54 finding the termi nal of an idle trunk line to stop the. upward movement of the switch shaft, before the brushes have been properly centered on the terminals of the idle trunk line. relay 518 is locked up over a circuit extending from grounded battery through the left hand winding of relay 518, the lower left hand contact of sequeiu-eswitch cam 515 (12), the right hand winding of relay 521. conductor 554, centering segment 555 of commutator 531, brush 556, conductor 533, the upper right hand contact of sequence switch earn 507 (12), conductor 523, the left hand armature and front contact of relay 518, the lower left hand contact of sequence switch 508 (12) and thence to ground at the right hand armature and front contact of relay 521, this circuit being maintained until brush 556 engages an insulating segment of commutator 531 corresponding with the centered position of the brush set upon the, terminals of the selected line.

ill!