US1333026A - Telephone system - Google Patents

Description

A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FILED 050.27. 19 16.

Patented Mar. 9,1920.

4 SHEETS-SHEET I A. E. LUNDELL.

TELEPHONE SYSTEM. APPLICATION FILED n'zc.27,191 e.

Patented Mar. 9, 1920.

4 SHEETS-SHEET 2.

A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FILED DEC-27, I916.

Patented Mar. 9, 1920.

4 SHEETS-SHEET 3- A. E. LUNDELL.

TELEPHONE SYSTEM.

APPLICATION FILED DEC.27, 191s.

Patented Mar. 1920.

4 SHEETS-SHEET 4.

//1, men 20/1' Awe/7 A? Aunde/K UN ED sr 'r s PATENT orrioE.

ALBEN E. LUNDELL, oF NEW YonK, N. Y.,-AssIG1\ion 'IO WESTERN ELECTRIC COMIANY, INCORPORATED, or NEW YORK, N. Y;, A conronarron or NEW YORK.

Application filed Deceinber 27, 1916. ser al No. 139,092.

To all whom it may concern:

Be it'known that I, ALBEJ E. LUNDELL, a

citizen of the UnitedStates, residing at New The main feature of this invention is the" rovision of meanswhereb ifthea aratus associated with the operators position is actuated and then does not proceed 111 its cycle of Operation within a given time interval, a slgnal 1s actuated'and theapp'aratus rendered unselectable until the abnore mal condition has been remedied.

Other features of the invention will appear from the detailed description and claims. j r The drawings, with Figure2 placed above Fig. 1, and Fig. 3 placed above Fig. 2, repre sent diagrammatically a portion of a telephone system embodying the present invention. The portion of the drawing at the right of the dotted line in Fig. 1, represents a controlling operators position; the portion of the drawing at the left of the dotted line. in Fig. 1, represents the terminals of a selector switch at a distant ofiice.

Fig. 2 represents the arrangemenbof a trunk-finder switch, by means of which an operators controlling circuit may be extend-1 ed to lIlCllOEltOl. switches arranged to actuatecertain signals. i w

Fig. 3 represents ,a plurality of varlably operable number indicator switches ofthe'sequence switch type adapted to be set by the controlling operator and also represents signals controlled by the switches for indicating the designationof a wanted line. ,v

' Fig. 4 represents the trouble indlcating means and schematically. shows the relation I of. this means to a group of trunk finders. The relation of the trouble indicating means represented within the large dotted rectangle B of Figml, to the trunk finder dlagram matically shownin Fig. 2, is indicated by the small dotted rectangle at the bottom of Fig. 2. The relationv of the means for rendering the group of trunks non-selectable shown in the dotted rectangleA of Fig. 45, to the'poi TELEPHONE SYSTEM.

Specification of Letters Patent." I Patented Ma -,9 1920,

tion of the system herein disclosed, is indicated by the dotted rectangle A at the left of Fig. 1. V

' A plurality of sequence switches :of a structure similar to thatdisclosed in Patent No. 1,127,808 to Messrs. Reynolds and Baldwin, and similarin operation and function to the sequence switch disclosed in the patentto McBerty, No. 1,125,579, are employed. The contacts controlled by any sequence switch are separated from the contacts of other sequence switches by dotted lines and by the confines of the drawings.

An allotter 200, Fig. 2, is of the same structure as thesequence switches employed in the system, and controls the contacts shown within the dotted rectangle around this allotter. Under the control of the allotter 200 the trunk finder 201 ispreselected for service. The trunk finder may be of the same structure as the cord-finder fully de scribed in Patent No. 1,168,319 to A. E. Lundell, or the selector switch disclosed in Patent No} 1,123,696, to Craft and Reynolds. The allotter 200 preselects the trunk finder 201 bytmoving the sequence switch 203, ELSSO; ciated with such trunk finder, out of position 18 into position 1. The allotter will accomplish itspreselecting operations whenfin its stopping positions indicated by the numerals adjacent to master contact 242. When the allotter is in position 4, into which position it ismoved after the trunk finder associated with sequenceswitch 203 is taken for use, it will preselect one of a group of trunk finders whose sequence switches are in'position 18. It'will be noted that position 18 of the sequence switch associated with any trunk finder,- is the. position in which that trunk.

tinder is awaiting preselection. The operationof the trunk fitnders similar to 201, and

of-the associated sequence switches similar to 203, are identical, and it is, therefore,

deemed necessary only to describe the opnected to the terminals 130 and 156.

including the well-known stepping relay (also not shown) is arranged to be consendcr (not shown) which may be of the type disclosed in Patent 1,168,319 to A. E. Lundell, is employed. 1 i

As soon as the connecting operator receives a call through trunks 101 and 129,

the line relay 103 is energized over a c-ir;

cuit extending from grounded battery, contact 10st, winding o't' line relay 103, contact 105, trunk 129, terminalfl30, through the fundamental circuit established in extending the call to this operators position,

terminal 156, trunk 1.01, contact'106, to

ground. The line relay 103 attracts its armatures and at its rlght-hand armature and front contact completes a circuit trom ground through conductor 107, contact 108,

magnet of sequence switch 100 to move this sequence switch out of position 1. As soon as sequence switch 100 reachesposition 2, relay 207 is energized over a circuit extending from grounded battery, winding ofthis relay, conductor 202, contacts 204; and Y205, conductor 206,'contact 109, to ground. The relay 207 attracts its armatures and at its right-hand armature and'front contact .com-

pletes a circuit for moving sequence switch 203 out of position 1 into'position 2. This circuitinay be traced from ground, righthandiarmature and front contact of relay 207,. contacts 208 and 209, magnet of sequence switch 203, to grounded battery. \Vhen the sequence switch 203 passes through position 11}, the energizing circuit,

previously described, for the relay 207 in replaced by a circuit extending from grounded battery, winding of relay 207, contacts'204t andf210, resistance 263, back contact and annature of relay 211, to ground,

In position 2 of the'sequence switch 203 the updriving clutch magnet 212 is energized over .a circuit extending from grounded I battery, winding 0 magnet 212, conductor 213,. contact 214;, r ght-hand trout contact 'and armature of relay 207, to ground."

Under the control of this magnet the wipers of the trunk finder switch 201 are moved upward over the bank of terminals contain- 7 ing One'set of: terminals for each trunk, to which the selector at the dlstant ollice (not shown), has access. Upon the engagement vby'the trunk finder wipers of the terminals individual to the trunk disclosed in Fig. 1, an energizing circuit is established t'or the relay 211, whichcontrols the stopping of the trunk finder switcln The energizing circuit for relay 211 may be'traced from grounded battery, winding ofrelay 211, contacts 215, 216, 217 and218, to wiper-219, terminal 220, conductor 221, contact 110, to ground. Relay 211 then locks itself up over the circuit completed through contacts 215 and 216 front contact and armature 211,

to ground. vAs a result, of the closure of tlnls circuit, relay 211 remains locked up mutator brush 225, to ground. lVhen relay 207 deenergizes a circuit is completed for moving sequence switch 203 into position This circuit may be traced from grounded batter], magnet of sequence switch 203, conductor 226, contact 228, right-hand back contact and armature of relay 207, to

ground.

In p0s1tion'3 of sequence switch 203, a

circuit is established from ground at the leftehandarmatureand frontcontact of relay 211, contacts 216, 229, c-onductor230, wiper 231, terminal 232, conductor 233, contacts 111 and 112, conductor 113, magnet of sequence switch 100, to grounded battery, to move this sequence switch out of position 2 into position 3. Relay 103 is new maintained energized over a circuit extending from grounded battery, contact 1041, winds ing of relay 103, contact 114, left-hand armature and front contact of relay 103, contacts 118 and 119 orer thctuhdamental circuit,

above described. 7

In position 30f sequence switch 100 a circuit is'completed for energizing relay 207. This circuit may be traced from grounded battery, winding of relay 207, contacts 201 and '236, wiper.235, terminal 237, conductor .238, contacts 120 and 121, right-hand front contact and armature of relay 103, to ground. Relay 207 attracts its armatures and its right-hand armature and front contact completes a circuit from ground through contacts 208 and 209, magnet of sequenceswitch 200, to grounded battery to move this sequence switch out of position 3 and into position 4. i

lVith the allotter 200 in posit-ionl, a circuit will be established fromgrounded bate tery, 'magnet of the allotter 200, contacts 239 and 210, contact 2411, to ground. Under control of its master contact 242, the

allotter is moved, into position ,4, in which position it controls the preselection of another sequence switch associated with a trunk finder similar to 201, If this sequence switch is in position 18, which is its normal .7

position, a circuit is completed for moving tliissequenceswitch out of position 18 into position 1.

' conductor 117, terminal234, wiper 243, con .ducto'r 244, contact 245, conductor 246, contacts 306, 307, 308,309, 310,- 311 and 312, conductor, 313, brush 247, terminal 248, conductor 224, contacts 122 and 119, over-the portion 'of the fundamental:circuit. mentioned, to ground at contact 106. Also, in position 4 of the sequence'switch 203 the numbel' indicator 300 is operated.

This circuit may be traced from grounded battery, magnet of indicator 300,'contact 314, conductor 315, contact 249, conductor 250, left-hand armature and front contactofrelay207, conductor 202, contacts 204 and 236, brush 235, terminal 237, conductor 238, contacts 120 and 121, conductor 107, righthand front contact and armature ofrelay 103, to ground. As indicator 300 is moving.

fromposition to position, its contact 316 is closedfor each position passed, and in response to each closure of the contact 316,'a

shunt circuit for short-circuiting the stepping relay (not shown) is completed from relay 103. This circuit may be traced from grounded battery, contact 104, winding of relay 103, contact 114, left-hand armature and front contact of relay 103, contacts 118 and 122, conductor 224, termina-l 248, wiper 247, conductors 313 and 317, contact 316, conductor 318, contact 251, right-hand front contact and armature of relay 207, to ground. As a result of the closure of this shunt circuit at contact 316, the stepping relay (not shown) of the fundamental circuit, above mentioned, becomes deenergized and actuates the counting relays in the well-known manner. After theindicator 300 has taken a number of steps determined by the operation of the sender (not shown), the countmg relays will" be'actuated in the well- .known manner to interrupt the fundamental circuit and cause the. de'e'nergization of relay 1.03. When relay 103 deenergizes it interrupts the energizing circuit of the relay 207. YYith relay 207 deenergized, as soon as the ndicator 300 reaches position X, a circuit is closed for moving sequence switch .203

into position 5. This circuit may be traced from grounded battery, magnet of sequence switch 203, contact 253, conductor 252, contacts 319, 320, 321, 322, 323 and 324, conductor 325, contact 254, conductor 255,righthand back contact and armature of relay 207, to ground. In the meantime the'fundamental circuit is again closed to energize the relay 103. q

The fundamental circuit now extends from grounded battery, contact 104, winding ofrelay 103, contacts 114,115 and 116, q

tacts 326, 307, 308,309, 310, e11, 312, e011- ductor 313, wiper 247, terminal 248, conductor 224, contacts 122 and 119, over that portion'ofthe fundamental circuit previously mentioned; As a result of the energization of relay 103, relay 207 is again energized, and com'pletesat its left-hand front contact and armature, an operating circuit for the indicator 301. This circuit maybe traced from groundedbattery, magnet of indicator 301, contact 327, conductor 328, contact 258, conductor 250, left-hand armature and front contact of relay 207, conductor 202, contacts 2041'and 236,'wiper 235, terminal 237, conductor 238, contacts 120, 121, conductor 107, right-hand front. contact and armature of relay'103 to ground. The indicator 301 opcrates and at its contact 328 controls the operationiof the sender '(not shown). When the fundamental circuit is interrupted after the setting of this indicator, the relays 103 and 207 are deenergized. The de'energiza tion of the relay207 completes a circuit for moving the sequence switch 203 out of position 5 into position 6. This circuit may be traced from' grounded battery, magnet of sequence switch 203, contact259, conductor 258, contacts 329, 321, 322, 323, 324', conductor 325, contact 254, conductor 255, right-hand back coutact and armature of relay 207 to ground. When the fundamental circuit is again reestablished to energize the relay 103, and in turn relay 207, an operat ing circuit is completed for the indicator 302, from grounded battery, contact 330. V

conductor 331, contact 260, conductor 250, left-hand armature and front contact of relay 2 07, conductor 202, contacts 204, 236, wiper 235, terminal 237, conductor 238, contacts 120 and 121, conductor 107, righthand front contact jandarmature of relay 103 to ground. The indicator 302 controls at its contact 332 the-operation of the sender (not shown). When the indicator 302 is properly set, the fundamental. 'circuit' is again interrupted to cause the deenergization of the relay 103, which in turncauses relay 207 to be deenergized. WVhen the re:

lay,207 deenergizes, a circuit is completed to back contact and armature of relay 207 to ground. In position 7 of sequence switch 203 with relays 103 and 207 again energized. on the reestablishment of the fundamental circuit, an operating circuit for the indicator 303 is established from grounded hat 7 tery. magnet of indica'tor303, contact 334,

conductor- 335, contact 261, conductor 250, f,

left-hand armature and frontcontact of: re-

lay 207, over the circuit previously de' scribed toground at the'right-hand front contact and armature of relay 103 to ground. The indicator at its contact 336 controls the operation of the sender (not shown) asv above mentioned. hen the indicator 303 has been setin accordancewith the operation of the sender, the fundamental circuit is againinterrupted, which results in the deenerglzatlon of relays 103. and 207. r-i circuit is thereupon completed for inovingthe sequence swltch 203 into 1303151011 8, whlch circuit extends from grounded battery, magnet-of sequence switch 203, Contact 259, conductor 258, contacts 337, 323, 324:, conductor 325,. contact 254:, conductor 255, left-hand back contact and armature of relay 203.130

ground. In position 8 V of the sequence switch 203, with relays 103 and 207 again energized, an operating circuit for the 1ndicator301 is completed from grounded battery, magnet of indicator 304, contact 338,

conductor 339, contact 262, conductor 250, left-hand armature and front cont-act ofrelay 207 to ground at the right-hand armature of relay 103. The contact338 ofindi cator 304: controls the operation of the sender (not shown). -VVhen the sender at the close of this series of impulses interrupts the fundamental circuit, relay 103 deenergizes, and this in turn causes the deenergization of relay 207. When relay 207 deener gizes a circuit is completed to move se quence swltch 203 outofv position 8 into position 9. This circuit may be traced from grounded battery, magnet of sequence switch 203, contact 253, conductor 252, contacts 339 and 324, conductor 325, contact 254, conductor 255, back contact and armature of relay 207, to ground. In position 9 of the sequence switch 203, the setting of the indicator 305 is accomplished in a'manner similar to the setting of the other indicators mentioned. When the setting of 1ndieator 305 is effected, the relay 103 deenergizes and this inturn'causes the deenergiza tion of relay 207. V r p After the setting ofthe indicator 305, a circuit is completed for moving the sequence switch 100 out of position'3 andintoposicoil 128, trunk conductor 129 and terminal 130 to ground at the preceding switch. Relay 126 attracts its arinatures and completes to ground.

a circuitfrom grounded battery, contacts 124 and 125, winding of relay 126, contact 160, front contact and armature of relay 126, contacts 132and 133, conductor 134:,

left-hand winding of relay 135 to ground. Relay. 135. attracts its armatures and at its right hand arinatur'e and front contact establishes a locking circuit for itself from ground, its right-hand front contact and armature, contact 111 and 136, right-hand winding of relay 135, conductor'137, consequence switch into position 10. In position 10 of this sequence switch, relay 207 is energized over a circuit extending from V grounded battery, winding of this relay, contacts 261 and 229, conductor 230, wiper 231, contact 232, conductor 233, armature and front contact of relay 135, to ground. When relay 207yis energized, an energizing circuit for the relay 265 is completed from grounded battery, winding of this relay, contact 266, conductor 267, contact 297, conductor 250, front contact and armature of relay 207, contacts .264 and 229, conductor 230, to ground at the right-hand armature and front contact of. relay 135; A substitute energizing circuit, for relay 265 is completed as soon as sequence switch 203 reaches position 14, which circuit extends through contact 266, conductor 267, contact 341, conductoi 342, contact 268, to ground. Relay 265 attracts its armatureand completes a circuit from grounded battery, magnet of sequence switch 203, contacts'269 and 270, front contactand armature of relay 265, contact 271., armature and front contact of relay 207, o ground, to move this sequence switch out of position 10 and into position 15. hen sequence switch 203 leaves position 14: the lamp allotter 298 selects an idle set of indicators for use.

\Vhilef the sequence switch 100 is'in posi-; tion 4,, a circuit is completed from grounded contacts 141 and 120, conductor 238, terminal 237, wiper235, contact 236, contact 21.0, through resistance 263, back contact and armature of relay 211, (which is deenergized battery, contact 139, winding of relay 140,

when sequence switch 203 leaves position 9), r

The relay 110 attracts its ar matures and atlts left-hand armature completes a circuit from grounded battery, contact spring 142, contact 1 13, winding of: .re

.lay .103,.contact 144, to ground. Relay 103.1

ously described. Under this arrangement relay 103 is maintained energizedcuntil the preceding selector is restored to its normal I position. When the relay-103 attracted its right-hand armature it, closed a circuit for moving the sequence switch 100 out'of position 4 and into position ,6. 1 This circuit may. be traced from grounded battery, magnet of the sequence switch 100, contact 108, conductor-107,right-handfront contact and arma- 1mm of relay 1031to ground. The sequence Tswijtch,100 isthen moved out of position 6 by a circuit completed from grounded battery, magnet of the sequence switch: 100,-

contact 180, back-contact and lower armature ofrelayi148 to ground.

' 148, sleeve of plug147, .to groundat the select the-proper ringing current.

lVhen thesoperator insertsplug 147 into the jack (not shown), the sleeve relay 148 is energized over a circuit which extends from grounded battery,fwinding of relay jack (not shown). Relay, 148 attracts its armatures and completes a circuit for moving sequence switch 100into a pos tion to ing current is applied in position 10 of sequence switch 100. ,The operating circuit for the sequence switch-100 may be traced from grounded battery, magnet of sequence switch 100, contact 149, left-hand front contact and armature of relay 135, which is locked up at this time, front contact and lower armature of relay 148, to ground. The sequence switch'100 continues to rotate until its} operating circuit is interrupted at the left-hand front contact and armature of relay 135; this occurs in the present 1n- -stance when the contact 138 is opened in position 9 of: sequence switch 100. In posiposition 10 of sequence switch 100, proper ringing current is I applied to the selected partyline. Assoon as the relay 135 dener grzes an ener izing circuit forthe ringing relay 163 is c osedfrom: grounded battery,

' contact 131, contact land: armature of. relay 126, contacts 168Hand 162,, winding of relay 163, upper armatureand. back contact of relay 164, armature andback contact of the ring trip relay 165, left-hand back contact 7 andarmature of relay135,-lowerfront contact andarmature of relay 148 to ground.

"circuits-Qthe relayi1'63.

It will be noted thatthe relay164 isshunted'l at this time. .Relay 163 however, attracts its armatures to apply ringing current to the: signal at the called substation. This circuit for applying ringing current,:. extends through the left-hand. winding of relay. 165', contact .166, front contact and upper arma ture of relay 163, frontcontact and upper plug 147 to hell at the calledisubstation, through the ring contact of plug 147', lower armature and. front contact of 'relay .163, contact 167 to. ground. The ringing trip 'armatureof relay l48y'fro m the tip of the relay 165 is marginal and .does'not attractitsarmature until thecalled party answers, at -wl11ch.-t1me it does attract its armature Relay 164 looks itself up and short- I As soon as the locking circuit of re'lay l35 front. contact ,andiarmature the energizing circuit forthe, relay. 207. As soon as the relay 207 deenergizes a-circu'ituis completed for moving sequence switch 203 out of position 15. Thiscircuit may be traced from grounded battery," magnet. of sequence switch 203, conductor 226, contact 228, rightand removes the short circuit aboutv there. i

s interrupted 1t breaks at ts right-hand hand. back contact and armature of relay 207, to ground. At position 16-of sequenceswitch ,-2;03*a, circuit is completed for the, down-,dr1ve magnet :272. This circuit may be. traced from grounded battery, winding fltwlll be assumed that the desired ringof magnet 272, contact 273, to ground. As" soon as the commutator brush 27 4 reaches normal segment 275 ofthe commutator, a cir-.

cuit is completed from'groundthrouglrcom mutator brush and normal segment 27 5, con-:

fromgrounded battery, magnet of theJindi-' cator 300, contact 350, contact .286, conductor 255,. right-hand back contact and armature of relay 207 to gronnd.- The operating circuit of the indicator: 301 is completedthrough contacts 351 and 287 to ground at the armature of relay 207.v The, indicator 302 hasits, restoring circuit closed through contacts- 352' and 288 to ground. Inlike.

manner','the indicators 303, 304 and-305 have their operating circuits closed: to ground, through contacts 281, 290 and291 respec-l tively, Assoon as all of the indicators are restored to their normal position, a circuit for moving-thesequence switch v203 outof position 17, is "completed from grounded battery,magnet of sequence switch 203, contact 277, conductor 278, through the normalj contacts 342, 320, 321, 322, 823 and 324, conductor 3255,. contact 254,- conductor 255,

right-hand armature. and back contact of relay 207, to ground. Position 18' is the normal position of the sequence switch 203 in which itawaits. selection. As soon as the al'lotter 200 reaches position 1, a circuit is completed from ground through contacts L 241, 240 and 209, magnet of sequence switch sequence switch into position 1.

203, to grounded battery, which moyes this The apparatus associated with the operators position, indicated at Fig v3, is restored to normal when the relay 126 is deenergized. by reason of the interruptlon of 1ts energ1zing circuit at the preceding selector switch.

When relay 126 retracts its armature, the

relay 140 deenergizes and this inturn causes the decnergization of the relay 103. when relay 103 retracts 1ts armature acircult is completed vfor moving the sequence switch 100 to its normal position, which circuit may;

be tracedfrom'groundedbattery, magnet of sequence switch 100, contact 152, rlght-hand back contact and armature of relay 103, to

ground; y p i It will be understood 1n this system that a trunkfinder similar to 201 is normally-1n- 1 position 1, selected for use, and a second trunk finder similar to 201 is in position-18 awaiting selection. If, however, due to any abnormal operation of the trunk finders, one

or more trunk finders are in position 18 in which I they 1 are awaiting selection; and a no trunk finders are standing 1n position 1, a

circuit arrangement disclosed in Fig. 4 becomes effective; This condition may arise from tailure of any trunk finder toproce'd inits cycle of operation from posltlon 1 to I position 40f its sequence switch, inwhich position the allotter 200' operates to select an idle trunk finder. The circult arrange ment of Fig. 4 under the control of a'timing device, operates-an alarm to indicate'the improper operation of the trunk finders and applies ground to the test terminals ofthe selector switch at the distant ofiice sot'that the trunks leading to the operators position shown in Fig. 3, cannot be selected until the abnormal condition has been removed;

In this system a switchboard clock; 400

' opens and closes the contact 401 at regular intervals of time. When contact 401 is 7 closed through the operation of the switch board clock the relay 402 is energizedover circuit extending from grounded battery, winding of magnet 402, contact 401, to ground; Relay 402 attracts its armatures and thereby completes a circuitfrom grounded battery, front contact and Emma til-re of relay 402, armature and baclr con-' 7 tact of relay 403, resistance 404,- W IIIdI'IIgOf relay 405, to ground, at one of-the contacts 406, 407, .and 408, oneof such'fcontact's being associated with and controlled by one of the trunk finders in the group. Relay 405 attracts its armature and thereby completes a locking circuit for. itself from grounded battery through its armatureand front contact, winding of relay403, resistance-404,winding ofrelay 405, to ground at one of the contacts 406, 407 and 408, 'Re- 1ay 403 attracts its armature. When relay 402 again attracts'its armature a circuit is con-ipletedfrom grounded battery, iiront con tact and armature of relay 402, armature and front 'contact o'f relay 403,- winding of relay 409, windingof relay-.410, to ground.

Relay 409 attracts its armature and c0m-' pletes a locking circuitfor itself. from grounded'battery, armature andfront contact Iof relay 405, armatureand" front contact of relay 409, Winding ofrelay 409,

winding of relay410, to ground} The'r'ela-y 410 attracts its armature and completes a circuit for energizing relay 411, which circu'it' may be traced from grounded battery,

winding" of relay 411,- front contact and ar "mature of relay 410, to ground} Relay 411 when energized closes an "energizing circuit for relay 414 and this relay controls a local circuit for alarm 413.

'Theineans for applying groundto the test terminals of thetrunks comprises a switch which may be tenneda snap switch. This witch" issimilar to the structure ofthe se quence switches, previously mentioned, with the exception that it has only two operating positions. These positions are the normal position of the switch and a second position 7 in which itfremains to apply ground to testterininals, until an. attendant removes;

the abnormal conditions and resets, the switch. When relay 410 attracted its ar mature a circuit for actuating switch 412 was established from grounded battery, magnetof switch412, contact 419, front contact and armature of relay 410. L If, however, one of the sequence switches associated with one vofthe trunk findersof thefgroup' moves into osition 1, subsequ en t to, the. eneifgization ot relay .405but prior trunks. In this instance relay 4 05 isshort- V circuited by way of conductor 415 through 1 any of the contacts 416, 417 or 418 ground.

Relay 405 retracts its armature and thereby interrupts the energizing circuit of relay 403. Whenrelay 403 retracts its armature,

. the operating circuit of relay 409 is opened: The deenergization of relay 409" causes relay 410 to deie'nergize to prevent the operation; of thealarm and the. grounding of the test terminals of the mentioned trunks.

It will be understood that these'circuits and apparatus may 'be" arranged to become,

effective if there isno-trunk finder in 130- lines, means for indicating the failure of sition 1 during a predetermined interval, regardless of whether other trunk. finders are in position 18.

Whatis claimedis: 1. In a telephone system, telephone lines, an automatic switch associated with said said switch to function properly,-and means to render said telephone lines unselectable when said switch fails to functionproperly.

2. In a telephone system, a plurality of telephone lines, a'plurality of automatic switches arranged to be brought into operative relation to any one of said lines, means common to said switches for indicating the failure of any switch to function properly, and means to render said lines unsele'ctable when any switch fails to function properly.

3. In a telephone system, a plurality of telephone lines, a plurality of witches associated with said telephone lines, mechanism for allotting a switch for'use, means for in dicating the abnormal operation of said switch, andmeans to characterize said lines by an unselectable condition when any of said switches failto function properly.

4. In a telephone system, a plurality of telephone lines, a plurality of switches asso- ,ciated with said telephone lines, mechanism for allotting a switch for use, means for indicating the failure of any switch to be allotted during a predetermined interval,

" and means to characterize said lines with an 7 'unselectable condition when any of said switches fail to function properly.

5. Ina telephone system, a plurality of telephone lines, a plurality of switches each having a normal position, mechanism for allotting a switch for use, means for indicating the failure of any switch to be allotted-during a predetermined interval while any switch is in its normal position, and means to characterize said telephone lines as busy when said indicating means operates.

6. In a telephone system a plurality of telephone lines, a plurality of switches,

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