US1387367A

US1387367A - Telephone system

Info

Publication number: US1387367A
Application number: US315816A
Authority: US
Inventors: William L Dodge; Hugh D Macpherson
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1919-08-07
Filing date: 1919-08-07
Publication date: 1921-08-09
Anticipated expiration: 1938-08-09

Description

w. L. DODGE/AND H. 0. MAcPHERSON.

IELEPHONE SYSTEM. APPLICATION FILED AUG-7, 1919.-

1,3 7,3 7, Patented Aug. 9,1921.

5 SHEETS-SHEET Afffy.

W. L. DODGE AND H. D. MAcPHERSON.

TELEPHONE SYSTEM.

APPLICATION FILED AUG-7, 1919.

1 ,387,367 Patented Aug. 9, 1921.

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TELEPHONE SYSTEM.

APPLICATION FILED Aue.7. 1919.

1,387,367.. Patented Aug. 9, 1921.

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W. L. DODGE AND H. D. MAcPHERSON.

TELEPHONE SYSTEM.

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TELEPHONE SYSTEM.

APPLICATION FILED AUGJ. 1919.

Patented Aug. 9, 1921.

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arena aorjs en.

WILLIAM L. DODGEAND HUGH n. ivrAornnnsongor ivmrnnwoon nnw JERSEY,

ASSIG-NOR TO WESTERN ELECTRIC COMPANY,

-N. Y., A CORPORATION OF NEW YORK.

rnconronnrnn, on" NEW" YORK,

TELEPHONE SYSTEM.

T 0 all whom it may concern:

Be it known that we, VILLIAM L. Donen and HUGH' D. MAGPHERSON, citizens ofthe United States, both residing atMaplewood, in the county of Essex and State of 'New Jersey, have invented certain new and useful Improvements in TelephoneSystems,of which the followingisa full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly to such systems" in which the signals for a. plurality of trunk lines extending between widely separated stations arecontrolled over a: single signaling path common to such trunk lines.

11 systems of this character it has been proposed to employ at opposite'ends of the c signaling path; switching means for temporarily rendering the common signaling path individual to the various trunk llIlGS'SGIVQCl thereby. The individualizing switching apparatus may comprisemeans for translating lnto code signals the signals initiated by the 'difi'erent trunk lin'es,melans for transmitting over-the signaling path the code signals which are individual to the'trunk lines, and means for receiving and translating the transmitted codesignals into signals indi-g vidual to the respective appropriate trunk lines. a

In order that the common signaling'path may be made" to serve asmany trunk lines as possible, it is desirable, in controlling subscribers in the building up and breaking down of connections over a trunk line, to transmit as few code signals as possible andto transmit the code signals as rapidly as possible. It is the object of the present invention thereforeto provide improved signaling means for systems of this character in which a minimum number of code signals for each connection established by way of a trunk line is transmitted, thereby rendering device may preferably 't'a'ke signal to the operator. y

The invention 1 may be more readily understood by a reference to thef-following description considered in: connection with the accompanying drawings, in "which Figures lfto' 5 inclusiveywh'en arranged in the Specification of Letters Patent. I Patented Aug; 9;.1921, Application filed August 7, 1919.

i Serial '-N0. 31 5,816.

. the common signaling path 4 available 'for the transmission of codesignals individual to other offthe trunk lines V to the end that I the comm'onsignrlingpath may be m ade to serve a greater number of-t-runk lines.

In attainlng this obj ect of -tlie-invention there is providedat the terminating station of the trunk lines'and signaling path apparatus individual to each trunk line -wh ich -isresponsive to thecontinued rapid opening and closing of the connected telephoneline,

as when the subscriberatthe station thereon is'ra'pidly 'opening-and closing the switchhook contact to signal the originating operator, for setting up and transmitting over the'common signalingpa'th but two code sig-' nals during such continued rapid-opening and closingof the telephone line. Apparatus individual togea'ch trunk line provided at the originating station is respon i've to the two transmitted code signals causing'the operation of a signaling deyice associated with the engagedtrunk'line. This signaling "the 'fo'rm of a signal lamp in a connected link circuit which is lighted intermittently 1 :during 5 the j continued opening and closing of "thedistant connected telephoneiline to serve as a recall manner indicated in "Fig 5, represent one embodiment of the invention; Referrin to Fig. 5 all-apparatusshown to: the left of 3-3 is located'at the ethos Z. Like=a1')pa-' ratus at the two" oflices X 'and Y-will be the dotted line 2 2 is located at the'oflice designated by the same reference Icharacterswithout primes at the office X, and with primes at the ofiice Y.

Referring to the drawings there is shown a toll trunk line L comprising two talking conductors extending from a central office X to a central ofiice Y. At central ofiice X there is located a toll cord circuit F by means of which connection is established with the trunk line L The trunk line L may be connected with a toll switching trunk circuit M extending from the central oihce Y to a central office Z, at which terminates a subscribers telephone line 1* with which the toll switching trunk circuit M may be connect-ed. While only one toll cord circuit, one toll trunk line, one toll switching trunk, and one subscribers telephone line are shown, it is to be understood that this is for the purpose of convenience only and that many such circuits and lines may be and usually are provided, in actual service.

The signals for a plurality of toll trunk lines may be controlled over a signaling path common to the trunk lines and com prising a conductor P, extending from a central office X to the central office Y, which conductor as shown has a grounded return. The signaling conductor is arranged in a well-known manner for duplex operation, for which purpose there is provided at the ends of the conductor artificial balancing line AL and

diiferentialpolarized relays

25 and 25. Each end of the common signaling conductor P is connected with a commutator for sending and receiving signals. vThese commutators are preferably of the well-known startstop type of distributers employed in connection with printing telegraph systems and are, it will be understood, provided with a synchronizing device (not shown) by means of which, approximate synchronism is automatically maintained therebetween.

The commutator at ofiice X comprises a sending distributer S for transmitting signals over conductor P to the otlice Y and a receiving distributer R for receiving signals transmitted over conductor P from the office Y, and similarly the commutator at the office Y comprises a sending distributer S and a receiving :distributer R for transmitting signals to and receiving signals from the office X over the conductor P. These commutators comprising sending and receiving distributers are of the same construction and a description of one will be sufficient. For convenience, the construction of the sending and receiving distributers S and R only will be described, for thesending and receiving distributers S and R are exactly like the former and need no specific descrip tion. The sending and receiving distributers S and R each comprises a series of stationary rings some of which are continuous and others segmented and a common shaft upon which are mounted brushes 9 and 10 normally held against rotation by the respective armatures of two separately controlled release magnets. The outer end of each brush is insulated from the inner end so that each brush controls two separate groups of circuits. Between the common shaft and each brush there is provided friction clutch mechanism (not shown) by means of which the constantly rotating shaft causes the rotation of each brush when released. The face of the sending distributor S is stationary and is providedwith a common sending ring 14, a restoring segment 1 a start segment 8, and individual sending segments 1 to 6 for controlling the signals transmitted over the signaling conductor P and with a common ring 15 and segments 16, 17 and 18 for controlling local circuits. The face of. the re ceiving distributer R is also stationary and is provided with a common receiving ring 19 and individual receiving segments 1 to 6 for selecting a circuit according to the case of signals received over the signaling conductor P, segments 20 and 21 through which the selected signal receiving circuit is completed, segments 22 and 23 for controlling the circuit of the associated release magnet RRM and a ring 24 and segment 31 for controlling a local circuit.

At central oflice X the common conductor P is connected to the common sending segment 1 while the normal contact of the differential polarized relay 25 thereat is connected with the common receiving segment 19, and the alternate contact is connected with the segment 22 in such manner that when the relay 25 is operatively energized, the release magnet RRM is energized to release the brush 10. At the central office Y the common conductorP is connected with the common sending segment 1%, while the normal contact of the differential polarized relay 25 is connected with the common'receiving segment 19, and the alternate contact of this relay is connected with the segment 22 in such manner. that when the relay 25 is operatively energized, the release magnet RB'M is energized to release the brush 10.

The signals transmitted over the common signaling conduct-or P by the sending distributers S and S are determined by the polarityof current connected with the individual sending segments of the respective sending distributers S and S. These polarities are determined by the position of the brushes of automatic selector switches G and G provided at the respective oflices X and Y. These automatic selector switches which are common to a plurality of trunk lines, are alike instructure. The automatic selector switch G is provided-with eight brushes 0;, Z) and 1 to t mounted upon a single shaft driven by a motor magnet MM initially controlled by a start magnet 30 connected in the start conductor or lead ST commoir associated with the automatic selector switch G are controlled by the sending distrihuter S for reasons which will more fully hereinafter appear. A plurality of contacts equal to twice the number of toll trunk lines to which the automatic selector switch G is common, is associated with each brush. The contacts associated with the different brushes are mounted at different levels in position to he engaged by the respective brushes as they are rotated by the motor magnet MM. Two correspondingly positioned contacts of all levels are allotted to each trunk line, for example, the first two contacts may be allotted totrunl: line No. 1, the second two to trunk line No. 2 the third two to trunk line N 3, etc. The two contacts of levels a and Zn allottedto each trunk line, are connected with relays individual to and associated with the outgoing end of the trunk line. The trunk line represented in the drawings may be considered as trunk lineNoL: As showny relays indiridual'to the outgoing end of this trunk line No. l are connectedby means of individual signal control leads A and G and restoring'leads B and D with the allotted contacts oi levels-(2- and 5 signal control leads il and C being connected to the respective first Llllfl'SQCOl'ltl contacts of level (6 and restoring conductors or leads, B and D to the respective first and second contacts of level 3). Each trunlz line is-p idedxwith j similar signal control and restoring leads at the ethos similarly coni'iected-with the selector switch G. The automatic selector switches shown in the drawing are provided withwsuificient contacts to accommodate thirty trunk lines. To the first and second contacts of the le*-;*elsoneto s' I l to the respective trunk lines, is connected current of the polarities in'combinations as indicated in the following table, there being a different combination for each trunk line '30 of the switch G.

and also for the 'firstand second-contacts allotted thereto. I

at the ethos Y is l ike'the switch G in structure and is associated-with the sending dis tributer S in the same manner as switch G is associated with the sending ,distributer S. Similar start and motor magnets 30'' and MM and stopping, slow releasing and re lease relays 32", 33 and at are also provided for the automatic selector switch G. This automatic selector switch ,t is associated with the incoming ends otthe trunk lines by means oi three individual conductors and acommon conductor. .This switch G is associated with the trunk lineL shown in the drawings, by means of the individual signal control leads A and C and restoring lead BD and a common start lead ST, individual conductors or leads A? and C being connected with the 1 allotted first and second contacts of level 0/,

individual conductor of lead BD with both allotted contacts of the level 6 and the common conductor with the start magnet The selector switch G is associated with each or" the otheritrunk lines through similar signal control and restoring leads A, C and BD. The polarities connected with the individual sending segments 1' to 6 of the sending distributor S are determined by the position of the brushes 1 to 6 of the switch G, and the difierent combinations of polarities connected with the allotted first and second contacts of the levelsone to siXfor the various trunk lines are identical with those connected with the automatic selector switch G. These are shown in the preceding table.

In order that the signals transmitted from the oiiice X by the sending distributor S and received at the o'llice Y may be utilized, there are provided thereat six locking relays 41 to 46 inclusive, having energizing windings connected with the respective individual receiving segments 1 to 6 of the receiving distributor R. When anegative impulse is transmitted from a' particular individual sending segment, the lock-up relay connected with the corresponding individual receiving segment, will be energized and locked up. Lock-up relays 41 to 44 control a plurality o1 receiving and selecting relays 50 to 64 inclusive. which cooperate with lock-up relay 45 to select a signal control. circuit individual to a trunk line, while lock-up relay 46 controls the polarity of current connected with the selected signal control circuit. The individ ual signal control circuits are connected with contacts of the relays 57 to 64 inclusive. Similar equipment is provided at the central ofiice X for utilizing the signals transmitted from the oflice Y over the common signaling conductor 1?.

Having in mind this brief description of the apparatus of the system shown in the drawings, it is thought that the lllVQlltlOll will be more thoroughly understood from a description of the operation 01". the system shown Connection of 00rd circuit F with trunk Zinc L 73 thereupon operates over a circuit from" battery tnrough the winding of marginalrelay 72, sleet e contacts of the plug 70 and the jack 71 and the winding of relay 73 to ground. Relay 72 is marginal and does not operate at this time. Relay 73 in operating causes the energization of relays 74 and 75, relay 74 operating over a circuit from battery through the contact of relay 73, winding of relay 74 and the normal contact of relay 76 to ground, while relay 75 operates over a circuit from battery through the contact of relay 73, winding of relay 75 and the normal contact of relay 77 to ground. Relay 74 in operating establishes a locking circuit for itself through one of its contacts to ground, and causes the energization of a differential relay 76 over a circuit from battery through the left-hand winding of relay 76 and an alternate contact of relay 74 to ground. Immediately upon energization, relay 76 by the closure of its inner lefthand alternate contact is rendered independent of relay 7 4, while relay 74 is locked up independent of relay 76. Relay 74 in operating causes the energization of the start magnet 30 over a circuit from battery through the start magnet 30, common start lead ST, middle normal contact of relay 78,

right-hand contact of relay 79 and right- ,hand alternate contact of relay 74 to ground. Start magnet 30 closes the circuit of the motor magnet MMwhich is of the self-interrupting type. The motor magnet advances all brushes of the selector G step-by-step until the brush (it engages the contact to which the signal control lead A is connected. This signal control lead A was previously grounded by the energization of relay 74 so that upon the engagement of the brush a; with the first contact assignedto trunk line L relay 32 operates over a circuit from battery through the upper winding of relay 32, brush a, signal control lead A left-hand normal contacts oi relays 78 and 7 9, and an alternate contact of relay 74 to ground. Relay 32 in operating opens the operating circuit of motor magnet MM thereby stopping the advancement of the brushes of the selector G. The relay 32 also completes a locking circuit for itself which may be traced from battery through the contact of relay 34, the middle alternate contacts and the lower winding of relay 32 to ground. The operation ol relay 32 causes the energization of relay 78 over a circuit from battery through the contacts of release relay 34 and slow releasing relay 33, upper alternate Contact of relay 32, brush 7), restoring lead B right-hand normal contact of relay 78, winding of relay '78, right-hand contact of relay 79 and an alternate contact of relay 74 to ground.

Relay 7 8 in operating completes a locking circuit for itself from battery through its right-hand alternate contact and winding, right-hand contact of relay 79, and an alternate contact of relay 74 to ground. Relay 78 inoperating removes the ground from signal control lead A connected thereto by the operation of relay 74, thereby opening the energizing circuit of relay 32 which, however, remainsoperated due to the closure of its locking'circuit; v Relay '32 ,in" closing its lower, alternate con-tact, causes the energization of the release magnet SRM- over a circuit from battery through ring 15,

brush 9, and segment 16 of the sending dis-, tributer S, the loweralternate; contact of relay 32, and the winding --of'rele'ase mags net SRM:to ground, The attraction of the armature of the release magnet SRM "upon the. energization thereof= releases the brush 9 Wl11Cl1 is thereupon rotated through a complete cycle at the end of which the brush The.

is stopped in its normal position brush 9 in being rotatedfirstengages start segment -s thereby connecting positive current with the. common signalingconductor P. This brush then [moves out of engage ment withthe segment 16, thereby opening theenergizing circuit of and causing. the

deenergization of the release; inagn'et SR-ML tacts on the first, second, fourth,- fifth and a sixth levels, while negative current is connected with such first contact of thethird level. When the.-brush.9 engages segment 17, slow releasing relay 33 operates over a circuit from battery through" segment 15, brush 9, segment 17 and the winding of relay 33 to ground. The operation of relay 33 removes battery from-.tlie brush 6. As

the brush 9 successively engages the individ- I ual sending segments 1 to, 6, currents of the polarity connected with these segments are successively connected with the conductor P. hen brush 9 moves out of engagement with segment v17 the energizing circuit of the slow-releasing relay 38! is opened and upon the engagementrof brush 9 with segment 18 release relay 34 is energizedovera circuit from battery through-segment 15, brush 9, segment 18 and thewi-nding of the release relay 34 to: ground. The e11ergiza-, tion of releaserelay 341 opens the locking circuit ofrelay 32 ,where-upon' thisrelay releases. Relay .is madeslow in releasing so that its, contact. remains open until after the openingoof the contact of release relay 3 1. As the brush9 movesout of'engagement with segment 18 release relay 34; is de-' energized. \Vhen brush 9 engages restoring segment 1", negative current 'islconnekzted with the common signaling conductor P.

I The automatic selectingswitch G; is nowin condition-to be seized by another truIl'kline,

since the trunk line Lliis disconnected, there,-

From, an in from' and the sending distributerS is in normal condition.

The "connection of positive current from 25 at oflic e Y over a circuit frompositive battery through segment S, brush 9, common segmentis jw-ith'conductor P causes the operation of the differential polarizedmelay sendingring l4 and the junction point between thewinclings ofdiiferential polarized relay 25, then by one path through the lower winding of relay 25 and artificial line to'ground and by another path through the upper winding of relay, 25, conductor P, both windings ofthe differential polarized relay 25, and theartificial line tov ground. 1

The operation of relay 25 causes the energization of release magnetRRM-over a cir cuit from battery throughthe alternate contact of relay 25,'segment 22fbrush 10 segment 23 and thejwinding of rel'easemag;

.net RBM'to ground. The attraction of the armatureof the release magnet RRMnpon the energi'zationthereof, releases the brush 10 which is thereupon-rotated through a complete cycleat the end of which the brush is stopped in its normal: position. As the brush l0 moves out of engagement with the segments 22" and. 23, the release magnet RR-M is I dejenergi-zed and permits the res torationof its armature to normal position preparatory to stopping the brush when it reaches its ,normal position. brush 10 moves out of engagement with segmentSl', relay 82 is de'e'nergized, closing its contact which is common to the locking circuits of relays 4:1 to 46 inclusive. The

. armature of the differential polarized relay 25 remains n its alternate position ,as long as POSltlVG current is connected with the other end ofconductor P and moves to its normal position whenever negative current is connected with the other endof conductor P. The brushes l0 and 9 are being rotated at the same time and while brush 9 is in engagement with segment 8 to which negative current is connected, the armature of relay When the. .i

25 moves to its normal position and brush 10 engages indlvidual recelvlng segment I 3'. Relay 43 thereuponoperates over a circuit from battery through thenormal contact of relay 25, common receiving ring 19',

brush 10', individual receiving segment 3' and the lower w nding of relay 48 to,

ground. B elay 43, then locks up through upper winding and contact and the contact of relay 82,'andcauses theoperationof re lays 51 and 52 over a circuit from battery, throughwindings or relayse52and 51 and the lower contact otrelayv48 to ground.

When the brush 10" cngag es segments 20 and 21., signal receiving "relay 85 operates over a circuit-..from'-negative battery 86 through thenormalcontact of relay 46, segment 20", brush 110 segment21, normal conenergized over a circuit from battery through tact of relay 15, lower normal contact of relay 50, lower alternate contact of relay 51, upper normal contacts of relays 58 and 58, selected signal receiving conductor E", individual to trunk ,line L and the lefthand winding of relay 85 to ground. Relay 93 is energized in parallel with relay 85 but does not lock up, on account of the open contact of relay 92 which is not energized until after the locking up of relay 85 and the release of relay 93. The energization of relay 93 at this time performs no useful function. Relay 85, in operating, completes a locking circuit for itself from battery through its right-hand alternate contact and right-hand winding to ground. The operation of the relay 85, individual to the incoming end of the trunk line L causes the lamp 90 to be lighted over a circuit from battery through the right-hand alternate contact of relay 85, lower normal contact of relay 91 and the lamp 90 to ground. Relay 85 in closing its left-hand alternate contact connects supervisory relay 94 in circuit with the talking conductors of the trunk line L extending toward the plug. When the brush 10 moves out of engagement with the segments 20 and 21, the energizing circuit of relays 85 and 93 is opened causing the denergization of relay 93. Slow-releasing relay 92 is then the right-hand alternate contact of relay 85, r1ght-hand normal contact of relay 93 and the winding of relay 92 to ground. When the brush 10 engages the segments 22 and 23', the armature ot relay 25 is in its normal position, since brush 9 is connected with restoring segment 1" and negative current is connected with the conductor P, and the energizing circuit of the release magnet RRM will be open. The engagement of the brush 10' with the segment 31 causes the energization of relay 82 over a circuit from battery through the ring 2 1, brush 10, segment 31' and the winding of relay 82 to ground. The energization of relay 82' opens the locking circuit of relay 13 which re leases, causing the deenergization of relays 51 and 52. All apparatus associated with the automatic selecting switch G, the sending distributer' S, the receiving distributer R and the relay selecting and receiving circuit, is now in normal condition, so that it may be associated with any other trunk line;

The lighting of the lamp 90 serves as'a guard signal tothe operator at the office Y, indicating that the operator at the otfice X has connected the toll cord circuit F with the proper trunk line L Connection of toll switching trnnh circuit M with telephone line N.

At the time the operator at the ofiice Y, designated th trunk line with which the operator of ofiice X should connect the cord circuit F, the operator at the otlice Y also communicated with the operator at the ofiice i nating this trunk, inserts plug 100 of the toll switching trunk circuit M into jack 101 of the telephone line N. Relay 102 and cutoli relay 103 thereupon operate over a circuit from battery through the winding of relay 102, sleeve contactsfof the plug, 100 and the jack 101 and the winding otcut-ofi' relay 103 to ground. relay 102 causes supervisory lamp 101 to be lighted over acircuit from battery through the lamp 104:, lower alternate contact of re The energization of lav 102, resistance 105and the normal conta ct of relay 106 to ground. The operation of cut-ofl' relay 103 disconnects line relay 107.

from the line wires of thetelephone line N.

Uonn-ection 0 f trunk line L with toll switching tritnh circuit M The operator at office Ybb s'er'Vingthe lighted condition of the lamp inserts plug 110 of of the trunk line L into jack 111 of the toll switching trunk circuit M. Relay 112 thereupon operates over a circuit from battery through the winding of relay 112, sleeve contact of the plug 110 and the jack 111 and resistance 113 to ground. Relay 91 operates upon the energization of relay 112 and in opening its lower normal contact eX- tinguishes the lamp 90. The energization of relay 91' also causes the operation 01 supervisory relay 9 1 of the trunk line L? and relay 106 of the toll switching trunk circuit M over a circuit from battery through the left-hand winding of relay 106, left-hand normal contact of relay 108, tip contacts of the jack 111 and theplug 110,

upper alternate contact of relay 91, upper normal contact of-ringing relay 1141, wind ing of supervisory relay 94;, left-hand alterna te contactrof relay 85, lower normal contact of ringing relay 114:, ring contacts 01 the plug 110 and the jack 111, the righthand normal contact of relay 108 and the righthand winding of relay 106 to ground. The energization of relay 106 opens the circuit of and extinguishes the lamp 104:.

The energization of the supervisory relay 94 causes the energization of relays 116, 117, 118 and 119, the energizing circuit for relay 116 being from batterythrough the winding of relay 116 and the alternate contact of supervisory relay 94: to ground. The energizingcircuit for relays 117' and'118 may be traced'from battery through'the windingof relay 117, the left-hand contact of relay 120, winding and normal contact of relay 118, left-hand normal contact of relay 119, righthand contact of relay 120, right-hand nor ternate contact of relay-118 to ground. The

energizing circuit for relay 119 -may be traced from battery through the winding of relay 119, right-hand normal contact thereof, right-hand contact of relay 120, righthand normal contact of relay '121and the alternate contact of supervisoryxrelay 94 to ground. Relay 119 upon being energized opens its left-hand normal contact,

which is in the energizing circuit of relays 117 and 118, and completes a locking circuit for itself from battery through the winding and alternate contact of relay 119, left-hand normal contact of relay 122, right-hand normal contact'of relay 121 and the alternate contact of supervisory relay 94 to ground. The energizing circuits for relays 116, 117, 118 and 119 are closed simultaneously'and the energization of relay 119 as already explained opens a contact in the energizing circuit of relays 117 and 118. In order that this contact may not be opened until after relays 117 and 118 have been energized relay 119 is made slightlyv slower in operating than relays117 and 118, but is sufiiciently fast in I energizing and deenergizing that it follows the energization and deenergization of the supervisory relay 94. The energization of relay .118 causes the operation of relay 123 over a circuit from battery through the right-hand alternate contact of relay 85, winding of relay 123, left-hand normal contact of relay 124 and the right-hand alternate contact of relay 118 to ground. Relay 123 in closing its contact prepares an energizing circuit. for relay 124, which, however, as long as relay 118 is energized, is shortcircuited by the left-hand normal contact of relay 124 and the right-hand alternate contact of relay 118. Relay 118 in closing its left-hand alternate contact grounds the signal control conductor Af connected with the first of the two contacts on level a of au tomatic selecting switch G" allotted to trunk line L The energization of relay 117 causes the energization of the start magnet 30, which thereupon closes the operating circuit to the motor magnet MM. This motor magnet which is of the self-interrupting type thereupon advances the brushes, of the switch G step-by-step until the brush a engages the contact to which the signal control conductor A is connected when relay ground.

32 118 energized to open the circuit of motor magnet MM. The relay 32, upon being energized completes a lockingcircuit through its left-hand winding and in closing its right-hand alternate contact causes the energization ofrelay 120 over a circuit from battery through the contacts of release relay 34 and slow releasing relay 33, right-hand alternate contact of relay 32, brush Z), restoring conductor BD and the winding of relay 120 to ground, Relay 120upon being energized opens the locking circuits of relays 117 and-118. The resulting deenergiza 7 tion of rela r 117 onens the ener izin circuit of start magnet 30. The openingof the left-hand alternate contact of relay 118 removes tl'le ground connection from the signal control conductor A. The opening of the righthand alternate contact of relay 118 upon the de'energization thereof removes the short-circuit about the winding of relay 124, which thereupon operates over a circuit from battery through the right-hand alternate contact of relay 85, winding and contact of relay 123, winding of relay 124 and the left-hand normal contactrof relay 121 to The closure of the left-hand alter nate contact of relay 32. causes the energization of the release magnet SRM of the send ing distributer Sover a circuit from battery throughring 15, brush 9, segment 16, lefthand alternate contact of relay 32 and the winding of the release magnet SRMto ground. I i

The sending distributer thereupon functions to successivelyconnect with the commen signaling conductor P currents of the polarities connected with the individual sending segments of this distributer. The

loo

polarities connected with the sending segments 1 to 6 are-determined by the polariconnected with segment 3. lVhile the brush 9 is making a complete cycle, the release magnet SR-M is dei nerglzed when the brush moves out ofengagement with segment 16,

is closed. during the time the brush is in engagement withsegment 17, and'the release: relay 34 is energized during the time the brush is in engagement with the segment 18, whereby the apparatus associated with the sending distributer S and the automatic selectingswitch Gfu'nctions in the same manner as that associated with the sendingdistributer Sand the automatic selecting switch G. Relay 120 becomes deenergized the circuit of the slow-releasing relay 33 upon the energization of the slow releasing relay 33. Relays 117 and 118 are not energized upon the release of relay 120, for the energizing circuit of these relays 117 and 118 is open at the left-hand normal contact of relay 119 which is locked up at this time.

The diiierential polarized relay 25 connected in the common signaling conductor P at the office X operates when the brush 9' engages the individual sending segment S, whereupon the release magnet Rlllil oi the receiving distributor R is energized'to release the brush 10. hen the brush 9 later engages the sending segment 3, the relay 25, is deenergized whereupon relay 13 energizes over a circuit from battery through the normal contact of relay 25, common receiving segment 19, brush 10, individual receiving segment 3 and the lower winding oi relay Q?) to ground. Belay 13 thereupon locks up through its upper winding and contact and the contact of the now deenergized relay 82. Relays 51 and 52 operate upon the energizetion of relay 43. Later upon the engagement of the brush 10 with the segments 20 and 21, relay '77 operates over a circuit from negative battery 86 through the normal contact of relay &6, segment 20, brush 10, segnient 21, lower normal contacts of relays 4:5 and 50, lower alternate contact of relay51, upper normal contacts of relays 53 and 58, signal receiving conductor E and the lefthand winding of signal receiving relay 77 to ground. Relay 77 thereupon locks up through its right-hand windings and righthand alternate contact, opening the energizing circuit of the slow releasing relay 75, and grounds resistance 130, thereby connecting this resistance in parallel with the winding of relay '73. The resistance of the circuit including the winding of the marginal relay 72 is thereby reduced to such an extent that the relay 72 operates to light the supervisory lamp 131. When brush 10 of the receiving distrihuter R reaches its normal position relay 82 is operated whereupon relays L3, 51 and 52 are restored to their normal condition. The lighting of the supervisory lamp 131 serves as a signal to the operator at the oihce X that the connection has been completed through to the line of the wanted subscriber and that the established circuit is in condition for signaling the subscriber of the wanted line. i

Operator at ofiice X, (remotes ringing key.

The operator at oiiice X upon observing the lighted condition of the supervisory lamp 131 may actuate ringing key 132 which connects a source of ringing current 183 with the talking conductors of the cord circuit F and the trunk line L Relay 1% is thereupon operated causing the energization of relay 79. The energization of relay 79 opens thevlocking circuit of'and release of relay 7 8. I Operator at ofiicc X restores ringing my. Upon the restoration of the ringing key 132 to normal position relay 134: releases, causing he deenergization of relay 79, thereby closing 1tsleft-hand contact to ground the signal control conductor A The de'energization of relay 78 followed by the deenergization of relay 79 restablishes the energizing circuit for the start magnet 30, whereupon the automatic selector switch G and the sending distributor S function in the same manner as when the plug was inserted into the jack 71 transmitting the same combination of impulses over the common signaling conductor P. The receiving distributcr It also functions as before to receive and distribute thecombination of impulses whereby the relay 82 is released, relay as energized and-locked up and relays 51 and 52 operated. Then when the brush 10" engages the segments 20and 21, relay 93 operates due to an impulse over a circuit from negative battery 86, through the lower normal contact of relay 4L6, segment 20, brush 10" and segment 2110f the receiving distributer R, lower normal contacts of relays 45 and 50', lower alternate contact of relay 51; upper normal contacts of relays 53 and 58, signal receiving conductor TF and the right-hand winding of signal receiving relay 93 to ground; Relay 93 immediately locks up over a circuit from battery through ts left-hand. winding and left-hand alternate contact and the contact of rela 92 to ground. The 0 ienin of J 7 h l l L a b the right-hand normal contact or relay 95 opens the energizing circuit of the slow re lease relay 92 while the closure of the righthand alternate contact of relay 93 causes the energization of the slow release relay 135 over a circuit from battery through the right-hand alternate contacts of relays 85 and 93 and the winding of relaye13 5 to ground. Relay 185 in operating causes the operation of a slow release relay-136 and ringing relay 114:, these relays operating in parallel upon the closure of the righthand, contact or relay 135; The opening of the normal contacts of ringing relay 11 1 causes the deenergization of supervisory relay 9 l, but relays 116, 119, 123 and 124: do not release for they are held operated 1 through the contact of relay 136 which is energized while the ringing relay 11 1 is energized. The opening of the contact of relay 92 upon the full release thereof opens the locking circuit of relay 93 which there upon releases. The opening 01": the righthand alternate contact of relay 93 causes the causes the release or" the slow releasing relay which i in opening its right-hand contact opens the tact of relay 32,ibrush 5', restoring conductor BD" and the winding of relay 120 to ground. Relays 117 and 121 are deenergized -upon the energization of relay 120.

The brushes of the selector switch G engaging the second set of contacts allotted -mined .by the polarities connected with the contacts of the automatic selector switch G engaged by the brushes 1' to 6. When the combination of impulses has been transmitted, the sending distributer S and the automatic selector switch G and associated apparatus are restored to normal position,

and the relay 120 is deenergized. These transmittedimpulses being received at the office X, cause theenergization and locking up of relays 43 and 46as the brush 10 of the receiving distributer R passes over the individual receiving segments 3 and 6 thereof. The operation of relay 43 causes the energization of relays51 and 52 in the manner hercinbefore described. Since relay 46 is energized when brush 10 engages the segments 20 and 21 of the receiving distributer It, the signal receiving relay 77 will be differentialized and released. This is brought about byconnecting a positive impulse from battery 99 with the originalenergizing circuit ofrelay 77. The relation of the number of turns of the two windings of signal receiving relay 77 is such thatwhen, positive current traverses theleft-hand or energizing winding of this relay at the same time that negative current is traversing the right-hand or locking winding the relay is differential ized and releases its armatures. The opening of the left hand alternate contact of this relay disconnects the resistance 130 from parallel relation with the winding of relay 7 3, whereupon the marginal relay 72 releases 7 its armature and extinguishes the lamp 131. Relay. 77 in releasing also causes the operation of the slow-release relay 75, restoring the apparatus at the office X to the samecon dition as it was prior to theinse'rtion of the plug 110 into the jack 111. The extinguishment of the lamp131 serves as a signal to the operator at theoliice X that the wanted subs scriber has responded. V

Subscriber restores recciocr to siuz'tchhook.

At the conclusion of the conversation the subscriberat the station on telephone line N restores'the receiver to the switchhook relays 43, 51 and 52.

thereby releasing supervisory relay 145 which opens a circuit of and releases relay 1.08. Relay 106 is thereupon connected in circuit with supervisory relay 94 thereby causing the energization of this relay 94. Just prior to the energization of the supervisory relay 94, all relays individual to the incoming end ofthe trunk line L which are controlled by the supervisory relay 94 are dcenergized.

The energization of the supervisory relay 94 causes the operation of relays 116, 117, 118 and 119 in the manner before described, causing the movement of the automatic se-, lector switch G until its brush a engages the grounded signal control conductor A, when the sending distributer S transmits over the conductor P, the same combination of impulses transmitted when the plug 110 was inserted in the jack 111. The operation of relay 118 also causes the energization of relay 123. Relay 120 also operates when relay 32 is energized to release relays 117 and 118. Upon the release of relay 118, relay124 operates. Upon the return of the brush of the sending distributer S to normal position andthe release of relays 117 and 118, the automatic selector switch Gr and the sending distributer S are freed from the trunk line L .and may thereafter be temporarily associated with any other trunk line. The transmitted combination of impulses is received at the office X through the action of the relay 25 and the receiving distributer B causing through the energization of relays 43 51 and 52 the energ g'ization and locking up of signal receiving relay 7 7 in the manner previously described. Resist ance 130' is thereupon connected in parallel with the winding of relay 73 to cause the operation of relay 72, whereby the supervisory lamp 131 is lighted to furnish a disconnect signal. Relay 75 releases upon the energizationof relay 77. -Following the energization of relay 77, the brush 10 is stopped in its normal position and relay S2 is energized causing the deenergization Operator at 077206 X disconnects toll 00rd cir- Quiz? F from trim/ 0 line L I The operator at office X upon observing the lighted condition of the supervisory lamp 131 withdraws the plug 7 0 from the jack 71, causing the release or relays 72,73, 74 and 7 8. The release of relay '72 opens the.

circuit of and extinguishes the supervisory lamp 131. The release of relay 74 causes the energization of start magnet 30 over a circuit from battery throughthe winning of start magnet 30, start lead ST, outer righthand alternate contact of relay 76 and the right-hand normal contact of relay '74 to ground. The deeneigization of relay 7-4 also grounds conductor C connected with energizing circuit of ringing relay 114 and slow releasing relay 136. Rlnging relay 1141 reissues beij'ore relay 186 and upon the, closure of the normal contact of this ringing relay 111, superrisery relay lllis immediately energized. The contact of relay 136 is not opened until after the closure of the alternate contact of the supervisory relay 94E.

llhile ringing relay 111 is energized the source of ringing current 137 is connected with the toll switching trunk circuit M to cause the energization of ringing response relay 138. While the energizing circuit of relay 106 opened by the opening of the normal, contacts of ringing relay 1 4.,- relay 106 does not have time to close its normal contact before the closure of the upper alternate contact of the ringing relay 114, when a temporary holding circuit for relay 106 is completed from battery through the left hand winding of relay 106, left-hand normal contact of relay 108, tip contacts of the jack 111 and the plug 110, upper alternate contact of relay 91 and the upper alternate contact of ringing relay 11 1 to ground. The response of relay '88 causes the operation of rela 108 and ringing relay 189 over a circuit including the left-hand \vindii'ig of relay 108 and the winding of ringing relay 139 in series and the contact of relay 188. The energization of relay 108 closes its alternate before opening its normal contacts, thereby establishing a substitute holding circuit through the left-hand winding of relay 106. Therefore, the lamp 101 is not lighted during the energization oi the ringing relay 111. Upon energization, ringing relay 139 connects the source of ringing current 1 10 with the line of subseriber l for emising the operation of the usual call bell 1 11 at the station Upon the release of relay 11-1 ringing current from the source 187 is disconnected from the toll s itching trunl: circuit M and ringing response relay 138 releases, causing the deenorgization of relay 108 and ringing relay 139. The release of relay 108 connectsboth windings of relay 106 in circuit with the siuiervisory relay 9-1; hefore the holding circuit of relay 106 is opened at the alternate Contact of relay 108, whereby this relay 1.06 remains energized. The (le'elnergization of relay 189 disconnects ringing current from the source of current 140 from the line of subscriber N.

Sat-scribe? of telephone line ZV, removes receiver from switch/1007?.

relay 1 15, upper normal contact of ringing Supervisoryrelay 145 in operating causes 1 the energization of relay 108 over a circuit from battery through the left-hand Winding of relay 108,, contact of supervisory relay 145, right-hand winding of relay 108 and the alternate contactof relay 106 to ground. Relay 108 in operating closes its alternate and opens its normal contacts, whereby relay 106 is disconnected from the circuit including the supervisory relay 94, and is maintained energized through its left-hand winding and the alternate contact ofirelay 108. Relay 108 in operating also causes the deenergization of the supervisory relay 94.- The supervisory relay 941 in opening its alternate contact,'opens theenergizing circuit of slow releasing relay 116 and the holding circuit of relay 119. Relay 116 is slow in releasing so that before it releases its armature relay 146,,which'is slow to release, is operated over a circuit from battery relay 120, winding of relay 121, right-hand normal contact of relay 118, right-hand alternate contact of relay 1241, normal contact of relay 116 and the normal contact of super Upon the closure of the normal convisory relay 94 to ground. Relay 121 in operating completes a locking circuit. for itself and relay 117 from battery through winding of relay 117, left-hand contact of relay 120, and the winding. and right-hand alternate contact. of relay 121 to ground.

Relay 121 by opening its left-hand normal contact causes the deenergization of slow releasing relays. 123 and 124. Relay 121 by closing its left-hand alternate contact grounds thesignal eontrollead C? which is connected to the second of the twocontacts,

on the level a of the automatic selector switch G, allotted to trunk line L The energization of relay117' causes the energization ofthe start, magnet 30' whereupon the motor magnet MM advances the selector switch until the brush a engages. the contact to which the signal control conductor 0' is connected. Relay 32 thereupon operates and locks up in the manner hereinbefore described, stopping the motor magnet lvll /l. Relay then operates over a circuit from battery through the contacts of relays 3 1 and 33, right-hand alternateconthe second of the two terminals on level a of the selector switch G allotted to trunk line L Motor magnet MM functions upon the energization of the start magnet 30 toadvance all brushes of the selector switch Gr until the brush a engages the contact to which signal control conductor C is connected, whereupon the relay 82 operates and locks up, opening the circuit of the motor magnet. The operation of relay 82 completes a circuit through the right-hind winding of relay 76 which may be traced from battery through the contacts of relays 34 and 33, upper alternate contact of relay 52, brush Z), restoring conductor D and the inner right-hand alternate contact and righthand winding of relay 76 to ground. This relay 7 6 thereupon becomes diflierentialized and releases its armatures. Brushes 1, 2, a

and 5 of the selector switch G now connect positive current, with individual sending segments 1, 2, a and 5 of the sending distributer S, while brushes 3 and 6 connect negative current with the individual sending segments 3 and 6. The closure of the lower alternate contact of relay 32 energizes the release magnet SR-M of the sending distributcr to release the brush 9, which, in making .a complete revolution, transmits over the common conductor P a combination of impulses corresponding tothe polarities connected with the individual sending segments of the distributer. .The transmitted impulses are received at the oilice Y by means of the relay 25; and the receiving di'stributer It, causing the energization of re lays -13 and 46 andithe locking up thereof through the respective upper windings and upper alternate contacts thereof, and the contact of the deenergized relay 82. Relays 51 and 52 operate upon the energization of relay 43 so that when the brush 10 engages segments 20 and 21, signal receivingrelay is dilferentialized, due to a positive impulse from the positive battery 99 through the lower alternate contact of relay 16, segment 20, brush 10', segment 21',

lower normal contacts of relays 15' and 50,

lower alternate contact of relay 51, upper normal contacts of relays 53 and 58, signal receiving conductor E? and the left-hand winding of signal receiving relay 85 to ground. Relay 85 thereupon releases its armatures. The opening of the right-hand alternate contact of relay 85' causes the release of relays 123 and 12 1-, and the closure of the normal contact of relay .85 causes the lighting of the lamp over a circuit from battery through the right-hand normal contact of relay 85,10wer alternate contact of. relay 91 and the lamp 90' to ground. The

lighting of the lamp 90 now serves as a disconnect signal to the operator at the office Y. The opening of the left-hand alternate contact of relay 85 opens the circuit which includes supervisory relay-94 and r-elay106,

whereupon both of these relays release their armatures. The opening the alternate contact of supervisory relay 9e restores relays116 and 119 to normal condition. Relay 11-6 is energized after the release of relay 94 and before the release of relay 116, but is de'c'nergized upon the opening of the alternate contact of relay 116. The energization of relay 146 does not at this time perform any useful function. The release of relay 106 of toll switching trunk circuit M causes the lighting of lamp 104 over, a circuitfrom battery through'the lamp 104, lower alternate contact of relay 102, resistance 1,05 and normal contact of relay 106 to ground. The lighting of the lamp 10 i now serves as a disconnect signal to the toll switching operator at the office Z. The 013-, erators at the oflice Y and the oliice Z upon observing the lighted condition of the respective supervisory lamps 90 and 10 1, may

withdraw the

plugs

110 and 100 from the respectwe acks 111 and 101, thereby restoring all apparatus to normal condition.

Subscriberoa talc ahoae line A recalls 0 9 cmtor at ojficc l.

way of the trunk line L and the toll switch-- ing trunk circuit M, wish to signal the operator at o'li ice X, this may be'done by repeatedly opening and. closing the switchhooh contact at the station on line N.- It will be remembered that while the receiver at station on line N is off the switchhoolr and the switchhoolr contact is closed, supervisory re lay 9a and all relays 116, 117, 118, 119, 120, 121, 122, 123 and 14:6 controlled by the super visory relay are deenergized. Of the other relays associated with the incoming end of thetrunk line L signal receiving relay and relays 91 and 112 are ener ized, while signal receiving relay 93, ringing relay 111 and the slow-releasing relays 92, 135 and 136 aredeenergized. Relay 116 is made slow in releasing so that its alternate contact will be held closed and its normal contact open during the short periods when the alternate contact of supervisory relay 94 is open while the subscriber of telephone'line N is repeat edly opening and closing the switchhoolr contact to signal the operator at oflice Xi operator at the office X when the subscriber of telephone lineN is recalling this operator. Upon the first opening of the switchhook contact at the station, over telephone line N, supervisory relay 9% is energized, whereupon relays 116, 117, 118 and 123 operate in the manner previously described. Upon the operation of relay 117, the automatic selector switch G advances until the brush a engages the rontact to which signal control conductor Al temporarily grounded, is connected, when relay 32 operates. Relay 120 tien operates to deenergize relays 117 and 118, the deenergization of the latter causing the energization and locking up of relay The operation of relay 32 causes the energiaatiou of the release magnet SRM, whereupon the sending distributor S transmits over the common conductor P a combination of impulses determined by the polarities connected with the individual sending segments 1 to G, by the brushes 1 to 6, respectively. The rereivingdis tributer R, at the ol'lire X, tune' tions uponv the reception of the transmitted combination of impulses by the relay 25 to cause the temporary deenergizatien of relay 82 and temymrary energization of relays d3, 51 and 52, whereby signal receiving relay 77 is energized and locked up. Marginal relay 72 then operates to light the supervisory lamp 131. Relay 75 is deenergized upon the operation of relay 77. The closure of the switchhook contact shortly after the opening thereof causes the deenergization oi"? the supervisory relay 94;. Relay 119 is immediately deenergized and relay 14:6 energized. Then, upon the energizatien ot the supervisory relay 9 1, in response to the next opening of the switchhook contact, relays 117. 118 and 119 operate as before described. Upon the operation of relay 118, relay 122 is energized over a circuit from battery through the right-hand alternate contact of signal receiving relay 85, winding ant right-hand normal contacts of relay 122, left-hand alternate contact of relay 12st. and the righthand alternate contact of relay 118 to ground. Relay 122 immediately locks up through its right-hand alternate contact and the lefthand normal contactof relay 121 to ground. Upon the energization of relay 122, relay 119 is locked up over a circuit from battery, through the winding of relay 119, alternate contact thereof, middle alternate contact of relay 122, and the left-hand normal contact of relay 121 to ground, whereby relay 119 is removed from the control of the supervisory relay 94, during the rapid energization and deenergization thereof, while the switchhook contact is being rapidly opened and closed to signal the operator at the oilice X. The energization of relays 117 and 118 causes the automatic selector switch G to start the sending distributor S which transmits over the conductor the combination of impulses corresponding to trunk line L and determined by the brush a, connecting wlth the temporarily grounded signal control conclm-tor Upon the reception of these impulses by the relay 25 atoilice X, the receiving distributor E functions again to cause the temporary deenergization of relay 82 and the temporary energization of relays 13, 51 and 52 as before. When the brush 10 engages segments 20 and 21, signal receiving relay 98 operates over a cirruit from the negative battery 86 through the normal contact 01 relay 16, segment 20, brush 1.0, segment 21, lower normal contacts of relays -15 and 50, lower alternate contact of relay 51, upper normal contacts of relays 53 and 58, signal receiving conductor E contact ot' relay '75 and the left-hand winding of relay to ground. Relay 98, in operating, completes a locking circuit for itself from battery through the contact of relay 73 and the right-hand winding and right-hand alternate contact of relay 98 to ground. The operation of relay 98 connects an interrupter 97 in circuit with resistance 130, thereby substituting an interrupted ground for the continuous ground, which causes the intermittent operation of the marginal relay 72. The intermittent operation of relay 7 2 causes the intermittent lighting of the supervisory lamp 131 which serves as a rccall signal to the operator at the office X, while the switchhook contact may he rapidly opened and closed many times but after the second opening the only eilect pro: duced upon the apparatus associated with the trunlcline L -is the energization and deenergization of the supervisory relay 9 1 and no apparatus associated with the common signaling conductor P is affected thereby. Thereiore when the called subscriber recalls, only two combinations of impulses, or two signals are'transmitted over the conductor to cause the'intermittent lightin of the supervisory lamp at the ofiice This intermittent lighting is at a constant rate, While the rate at which switchhook contact opened and closed may vary. The intermittent lighting of the supervisory lamp which continues only so long as the rapid opening and closing of. the switchhook contact continues, is a signal to the operator at the oii'ice X that the called subscriber is signaling.

If, after repeatedly opening, and closing the switchhook contact to signal the operator at the oliice X, the subscriber at the station on telephone line ll should leave the switch hook contact closed, then supervisory relay 94 is deenergized. After the comparatively extended deenernization of this supervisory relay 94, relay 116 releases its armatures and upon the closure of its normal contact relays 117 and 121 operate over a circuit from battery through the winding of relay 117, lefthand contact of relay 120, winding of relay 121, righthand normal contact of relay 118, right-hand alternate contact of relay 124, normal contact of relay 116 and the normalcontact of supervisory relay 9 1 to ground. The energization of the relay 121 releases relays, 119, 122. 123 and 121. The operation of relay 121 also grounds the signal control conductor (1' and the operation of relay 117 causes the energization of start magnet 30. Theselector switch G thereupon functions and the brushes thereof are advanced step-by-step until brush a engages the contact to which the grounded signal control conductor (1' is connected. Then the control apparatus associated with the selector G and sending distributer S function to cause the sending distributer S to transmit the same combination of impulses transmitted at the time the receiver was removed from the switchhook when the subscriber responded to the operation of the call bell." The reception of the transmitted impulses at the ofiice -X causes the transmission of a positive impulse from the positive battery 99 over the signal receiving conductor E for difierentializing signal receiving relays 77 and 98 whereby these two relays release their armatures disconneiting the interrupter 97 from circuit relation with the marginal relay 72. The relay 72 ther upon opens. its contact and eXtinguishes the supervisory lamp 131. Relay 7 5 operates upon the deenergization of relay 77.

If, after repeatedly opening and closing the switchhook contact tosignal the oper at the oflice X, the subscriber at the sta on line N should leave the switchhook con.- tact open, as when the receiver is restored the switchhook, supervisory relay 94k would be energized. An extended cnergization of the supervisory relay 9-1 causes the deiinergization of the relay 146 which upon the closure of its normal contact causes the energization of relays 117 and 121 over a circuit "from battery through the winding of relay 117 left-hand contact ofrelay 129, winding of relay 121, right-hand normal contact of relay 118, right-hand alternate (Ql'ltflQ/l] of relay 124-, left-hand alternate contact of relay 122 and the contact of relay 146 to ground. The

selector switch Gr and the sending and ceiving distributers S and R thereupon function in the manner previously described for causing the diflerentialization and release oi the signal receiving relays 77 and 98, which in releasing disconnect the interrupter 97 from circuit relation with marginal relay 72. Following the release of the relay 121, brought about in the manner before described, upon the energization of res lay 120, relays 117 and; 118 are operated over lay 118, leithand normal contact of relay 119, right-hand contact of relay 120, righthand "normal contact of relay 121 and the alternate contact of supervisory relay 9 1 to ground. Relays 117 and 118 are locked up immediately upon the energization of relay 118 and relay-119 operates shortly after the energization of relay 118 to open the original energizing circuit of relay 118. The energization of relays 117 and 118 results in the operation of the selector switch G and the sending and receiving distributor S and R for sending and receiving a combination of impulses corresponding to the polarities connected with the individual sending segments 1 to 6' bymeans of the brushes 1 to 6", the polarities being those connected with the first contacts of the first six levels on switch G allotted to trunk line L Upon the reception of these impulses by the relay 25 the receiving 'distributer R functions to cause the energization and locking up of signal receiving relay 77 whereupon marginal-relay 72 operates to light the supervisory lamp 131 which now serves as a disconnect signal to the operator at the oflice X.

Operator at'ofice X disconnects one coral circuit from and connects another cord cercm't with trunk Zane L 'operators telephone set (not shown) with the engaged cord circuit and converse with the subscriber on telephone line N. Upon being advised that the engaged cord circuit is noisy, the operator at the oflice X' may withdraw the plug 70 of the cord circuit F from the jack 71 of the trunk line L and insert the plug of another cord circuit into thejack 71 of the trunk line L, whereby a cord circuit, which is not noisy, is substituted for one which is noisy.

Upon the withdrawal of the plug from the jack 71, relay 78 is deenergized in precisely the same manner as when the ringing ,key is actuated, so that, if provision was means at the other in the fourth and sixth columns means that the third and sixth impulses to be transmitted are negative. lhe various code signals represented in the table aredetermined by the polarities connected with the tentacts of the first to sixth levels of the auto-- matic selector switches (l and G.

llhat is claimed is: i

1. In atelephone system, in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, a signaling device at one station, means at the other station responsive to rapid changes in the condition oi one ot the trunlc lines to transmit only two successive signals over the si nalin oath. a si nal rer a l P) ceiving circuit at the one station and means controlled over the signal receiving circuit and responsive to the two transmitted signals for causing the intermittent operation of the signaling device.

21in a telephone system, in combination, a plurality of trunk lines and a signaling path common thereto extendingbet'ween two stations, a signaling device at one station, station responsive to rapid changes in the condition of one of the trunk lines to transmit two successive signals overthe signaling path, a signal receivin oircuitat the one station, a signal receiving relay controlled over the signal receiving circuit and responsive to. thefirst trans mitted signal, a second signal receiving relay conditioned for operation by thecperation of the first signal receivin relay and responsivc to the second transmitted signal to cause the intermittent operation of the signaling device, and means for maintaining the second signal receiving relay operated until the de in-ergization of the first signal receiving relay.

3; in atelephone system, in combination,

a plurality of trunk lines and a signaling path con man thereto exgending between. two stations, a signaling device at one station, means at he other station responsive to ra pi d changes in the condition ot one of the trunk linesoccurring in rapid su -r'ession to transmit only two successive signals over the signaling path, a signal receiving circuit at the one station, a signal receiving relay responsive to the first transmitted signal, and a second signal receiving relay connected with the si 'nal receivi circuit upon the operation oi the first relay and responsive to i the second transmitted signal to cause the intermitten vice. y

4. ln a telephone system, in ro'mhination a plurality of trunk lines and'a signaling path common thereto extending betweon two stations, a signaling device at the station, means 'at the other station responsive to rapid changes in the-condition of one of the stations, a signaling device at operation of th signaling derupter mechanism, and a circuit for the sig nalins device and the interrupter mechanism completed through contacts of the energizer signal receiving relays.

5. In a telephine system, in combination, a plurality of trunlrlines and a signaling path common thereto extending between two stations, a signalingdcvice atone station, means at the other station responsive to changes in the condition of one of the trunk lines occurring in rapid succession to transmit two successive signals. over the signaling path, a signal receiving circuit at the one station, a signal receiving relay. controlled over the signal receiving circuit and responsive to the first transmitted signal, inter rupter mechanism, and second signal receiving relay responsive tothe second transmitted signal and cooperating with the first-.

6. In atelephone system, incomhination, a plurality oi? trunlr lines and a signaling between two one station, means at the other station responsive to changes in the condition of one of the trunl: lines occurring in rapid succession to trans mit two successive signalsover the signaling path and responsive to the cessation or such changes to transmit another si rrl over the signaling path, a signal receiving relay at the one station energized in response to first transmitted signal and det'nerg Id in response to the third transmitted s nal, a second signal receiving relay atthe one station path common thereto extending energized in response to the second transmitted signal and deenergized in'response to the third transmitted signal, and a signaling device operated by the cooperation of the two signal receiving relays when energized.

7. In a telephone system, in combination, a plurality of trunk lines and a signaling path common thereto extending between two stations, a signaling device at one station, a

signal transmitter at the other station, means normally responsive to each change in the condition of one of the trunk lines for causing the transmitter to transmit a signal over the signaling path tor controlling the sig. nalingdevice, and means rendered effective by a plurality of such changes occurring Within a predetermined period for rendering