US1537109A - Telephone system - Google Patents

Description

May 12, 1925. 1,537,109

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 1o, 1920 9 sheets-sheet 1 May l2, 1925.

J. DAVIDSON, JR

TELEPHONE SYSTEM 9 Sheets-Sheet 2 Filed Aug. 10. 1920 1,537,109 J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 1o. 1920 9 sheets-sheet /wen for Jah? al//dsa/l Jr.

May '12, 1925.

` May 12, 1925.

' J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10. 1920 i May l2, 1925.

J. DAVIDSON,y JR TELEPHONE SYSTEM Filed Aug. 10, 1920 May 12, 192s. 1,537,109y

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10, 1920 9 Sheets-Sheet 6 I s AL; L+ IH May 12, 1925.-

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10. 1920 9 Sheets-Sheet 7 May 12, 1925. 1,537,109

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10,y 1920 9 Sheets-Sheet s lvwwww. W u wl H uw T@ w w du i QNFWI. .JMW i f%\% May 12, 1925.

1,537,109 t J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10, 1920 9 Sheets-Sheet 9 y fw Af;

Patented Maly 12, 1925..

PATENT7-0FFficE. n

JOHN DAVIDSON, JR., or TRENTON, NEW JERSEY, nssieNon 'ro AME'RicAN `TELE- PHONE AND TELEGRAPH COMPANY, A conroianrioN or NEW YORK.

TELEPHONE SYSTEM.

Application `filed August 10,v 192,0. VSerial No. 402,632.

To all w/iom t may concern;

Be it known that l, JOHN DAVIDSON, Jr., residing at Trenton, in the county of Mercer and'State of New Jersey, haveinvented certain Improvements in Telephone Systems, of which the following is a speciiication.

This invention relates to methods and means for controlling a switchingI device by a plurality of sets of impulses in particular as applied to telephone systems in which the signals for a plurality oi'l trunk lines extending between widely separated oilices are controlled over a single signaling` path common to such trunk lines.

In systems of this character it has been proposed to employ, at opposite ends ot the signaling path, switching means for temporarily rendering the common signaling path individual te the various trunk lines served thereby, this individualizing apparatus coinprising means for translating into code signals the signals initiated by the diii'ereiit trunk lines, means for transmitting over the signaling path the code signals which are individual to the trunk lines, and means tor receiving and translating code signals into signals individual tothe respective trunks.`

Heretotore some systems of this character have been arrangedy for manual trunling only. It fi's desirable to arrange Vthe trunk circuits so thatthe incoming trunk terminals th'ereo'f may be `extended by automatic switching Kmeans to mechanical oiiices, to

`manual offices or to man-ual oliic'es yprovided In thisrei with call indicator mechanisms. spect the invention is in the nature of an improvement over the arrangement shown in applicants Patent No. 1,493,109, issued May 6, 1924. In order to accomplish this withoutsacrificing the efficiency of the trunk circuits for speech transmission, yit is desirable to transmit all supervisory signals over a common signaling path, thereby tree-ing the tru-nk circuits for the transmission of high :frequency switch controlling impulses and for the transmission of speech.

Anobject of the invention is to control a switching device by a code of impulses and `by other impulses. This is done by transmitting a code of impulses over a circuit to associate a switching device with another circuit and transmitting impulses over the latter mentioned circuit to control the switching device.

It is another object `ot the present invention. to provide improved signalingk means for systems ot this vcharacter by means ot which code impulses 'are transmitted over a common signaling path Jtor controlling the association of impulse receiving mechanisms with the incoming ends of a plurality of trunk circuits and tor controlling the'transmission ot all signals required for superrling automatic mechanism associated with the distant or incoming end of kthe trunk.

For ythe attainment oi" these objectsof the invention `there is provided at the originating. end ot ,the trunk lines and 'associated signaling path, apparatus individual to each trunk line responsive to the `seizure othe trunk, for setting up and transmitting a code of impulsesover `the common signaling path. These impulses are received at the terminating end of the signaling path and translated into a switching in'ipulse iior starting up a finder switchy for associating impulse receiving mechanism with vthe trunk takenfor use by the originating operator. The apparatus lat the originating end ot' the trunk lines is also arranged to .transmit further .code impulses over the signaling path for controlling the application oi ringing current and for controlling the release of the connection upon disconnection of the voriginating toll operators cord circuit trom Ithe employed trunk.

Apparatus individual t0 eachtrunk line is also provided at the terminating end ot' the trunk lines and associated signaling path for setting up and transmitting over the common signaling path, codes oli impulses which are received at the originatiiigend ot the signaling path and translated into signaling impulses for controlling the operation of `a supervisory signal associated with ithe toll `operators cord circuit, which is at `that time connected with a particular trunk circuit. This supervisory signal is arranged to give'l theopeiator la dialing signal to apvprise her that dialing impulses may be transmitted, as soon as the kimpulse receiving mechanism has been associated with the terminating end of they truuk vcircuit with which she has established connection, to give the operator the. usual supervisory signals when the connection has been extended to the distant called line, when the called subscriber responds, and when the called subscriber restores his receiver to the switchhook; and to give the operator a flashing signal to indicate that the called partly is busy if connection has been established to a subscriber in a distant mechanical otice or that the called subscriber is operating his switehhook for a recall.

For further attaining the objects ot the invention `there are provided means for transmitting dialing impulses of relatively high frequency tor example, 800 cycles, which, because oi their relatively high trequency are readily transmitted over the toll trunk i talking path without interference with the telegraph facilities oi? the trunk, and means for translating these impulses at the incoming end of the trunk circuit into direct current switch controlling impulses.

By the employment of the common signaling path for transmitting all supervisory signals in conjunction with means for employing high frequency transmitting and receiving mechanism for transmitting switch controlling impulses over t-he trunk circuit, it is possible to utilize the talking conductors of the trunk for the connection of telegraph apparatus thereto, to prevent tying up expensive signaling apparatus permanently with a particular toll trunk and thereby obtain a more etlicient use of the signaling apparatus, and to permit the use of as many telephone repeaters in the toll trunk as are found necessary for efficient transmission.

The invention may be more readily understood by reference to the following description considered in connection with the accompanying drawings, in which Fig. l shows a cord circuit at an originating toll operators position, a calling subscribers line which may be associated with the toll operators position .in any well-known manner, and the calling jack ot one of the toll trunks appearing before the toll operators position; Fig. 2 shows relay mechanism individual to the outgoing end of a toll trunk and code impulse sending mechanism associated with the outgoing end of' a signaling path common to a plurality ot toll trunks; Fig. 3 shows a receiving and translating mechanism for receiving code impulses incoming over the signaling path; Fig. i shows a sending mechanism associated with the distant terminating end of the signaling path and common to a plurality of toll trunks, together with relays individual to the incoming end of one of said toll trunks for controlling said sending mechanism; Fig. 5 shows a receiving and translating mechanism associated with the distant terminating end of the signaling path for receiving code impulses incoming over the signaling path from the originating toll operators position and for controlling the individual relays of the associated group ot trunks; Fig. 6 shows one of a plurality ot iinder switches for associating a high frequency impulse repeating mechanism with a toll trunk which has been taken for use, and a selector switch in which the incoming end of the toll trunk terminates; Fig. 7 shows a terminating operators cord circuit and the line oi a subscriber to which the toll connection may be extended; Fig. 8 shows a lamp indicator for association with the operators cord circuit shown in Fig. 7, on which indicator a registration oi the number of the line desired may be set up by impulses transmittedthereto by the toll operator; and Fig. 9 shows a cord circuit at the position ot a terminating operator in an ottico equipped for extending calls in accord ance with oral directions received from the originating toll operator, together with means for automatically associating the operators head set with the cord circuit taken for use.

Figs. l to 8 inclusive, when arranged with Fig. i). at the right of Fig. l, Fig. 3 beneath Fig. Q, Fig. il at the right of Fig. Q, Fig. 5 beneath Fig. il, 6 at the right of Fig. il. Fig. 7 at the right of Fig. 6, and Fig. 8 beneath Fig. 7, show as much of a complete organization of circuits as is necessary to illustrate the manner in which a connection may be established from a calling subscribers line in an originating office X to a subscribers line in a terminating office Z which is equipped for switching in accordance with call indicator line designations. Figs. l to 6 and 9 when arranged as above indicated but with Fig. 9 substituted for Figs. 7 and 8 and placed at the right ot Fig. 6. shou as much of a complete organization ot circuits as is necessary to illustrate the method of extending calls to a terminating oliice -W equipped for straight-'forward switching through call circuit trunks.

The apparatus disclosed in Figs. l, 2, and 3 is located at oliice X, that shown in Figs. l, 5, and 6 at an intermediate otlice Y, thatshown in Figs. 7 and 8 at a terminating ottice Z, while that apparatus shown in Fig. 9 is located at a second terminating oilice lV. Like apparatus at the two oli'ices X and Y will be designated by the same reference characters without primes at the otlice X and with primes at the oflice Y.

Referring to the drawings there is shown a toll trunk line L comprising two talking conductors extending from the originating oliice X to the intermediate oiiice Y. At the originating otlice X there are provided a plurality of toll cords one of which is shown at F, by means or" which connection may be Sil I irl established with the trunk line L. The trunk line L terminates at the ofiice Y in an oflice selector switch H, by means `of which the tollv line L may be connected with any one of the terminating oiiices such as Z or l or with a full mechanical exchange (not shown), and also terminates in multiple terminals appearing bef'ore a plurality of linder switches, one of whichis shown at K.

At the terminating oliice Z the trunk lines extending from the bank of selectors H one of which is shown in Fig. 7 terminate in plug terminals by Vmeans of which connections may be extended to subscribers7 lines in the terminating oiiice, one of which lines is designated as B. Connections are eX- tended at the ofiice Z in accordance with designations set up upon the call indicator shown at I in Fig. `S, which indicator is common to a plurality `of terminating trunks and `is associated `with any one of such trunks bymeans of a finder switch shown at M. l

At the ofiice W,- each of the trunk circuits, incoming from the bank of selectors H, terminates in a calling plug by means of which connections may be extended to subscribers lines, one of which has been designated B. At this ofiice the operators set O may be associated with any one of the incoming trunk circuits by means of a finder switch N.

The selector switch H at the intermediate ofiice Y may, in addition to having access to terminating ofiices Zl and W, have access in the well-known manner to trunk circuits eX- tending to full mechanical oflices. As the apparatus usually employed in such mechanical offices is well-known, it is not deemed necessary to illustrate such apparatus in the drawings.

1While only onetoil cord circuitone toll trunk line, one oiiice selector switch H. one terminating trunk at `the otiice Z, one ter-- minatmg trunk at the oiiice W, and onesubscribers telephone line' at each ot the offices Z and W have been shown, it isto be understood that this is for the purpose `ot convenience onlyand that as many ot such circuits and lines may be provided as are necessary to meet the requirements' of the trafiic.

The supervisory signals for supervising calls overa plurality of toll trunk lines may `be controlled over a single signaling path common to the trunk lines and comprising a conductor P extending from the originating oiiice X to the intermediateoiiice Y, which path is shown as having a grounded return. The signaling path is arranged in a well-known manner for duplex operation, for which purpose there are provided at the ends the artificial balancing lines AL and i'liiiieientially balancedrelays 25 and 25. Each end of the common signaling conductor P is connected with a commutatoi' tor sending and receiving signals. These commutators vare preferably of the wellknown start-stop type of distributors employed in connection with printing telegraph systems. Such commutators are dis` ollice Y, and similarly the commutator at i the cnice Y comprises a sending distributor S and a 'receiving distributor R for tra-nsniitting signals, to, and receiving signals from, the oflice X-over the conductor P. These commutators at bothv oflices X and Y are of the same construction and a description ot one will be sufiicient, and for convenience the construction of the sending and receiving distributors S and R will be described. The sending .andreceiving disti-ibutors S and R each comprises a series of stationary rings, some of which are continuous and others segmented. A common shaft `for the distributors has brush-arms 9 yand 10 mounted thereon andnormally held against rotation by the respective armatures of two separately controlled release magnets SRM and HRM. The outer end of each kbrush-'arm is insulated from the inner end so that each brush-arm controls two separate groups of circuits. Between the common shaft and each brush-arm there is rovided fiictional clutch mechanism ljnot shown.) by means of which the constantly rotating shaft causes the rotation of each brush-arm when released. The face of the sending commutator S is stationary and is provided with a common sending ring 14, a restoring segment fr, a start segment s, 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 receiving distributor R is also stationary and lis provided with a common receiving ring 19 and individual receiving segments 21 to 26 for selecting a circuit according to the code of signals received over the signaling conductor P, segments 27 and 28, through which the signal is completed, segments 29 and 30 for controlling the circuit lof the associated release magnet and a ring 31 ment 19 and the alternate contact is connected with the segment 29. W'hen. the relay 25 is operatively energized the re lease magnet BRM is energized to release the bruslrarm 10. :it the intermediate oiiice Y the common conductor P is connected with the common sending segment 14, while the normal contact ot 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 29. vWhen the relay 25 is opera tively energized, the release magnet RRM is energized to release the brush-arm l.

The codes ot signals transmitted over the conunon signaling conductor P by the sending distributors S and S are determined by the polarity of current connected with the individual sending` segments et the respective sending distributors S and S. rlfhese polarities are determined by the position of the brushes ot automatic selector switches G and G provided at the respective ottices X and Y. These auton'latic selector switches which are conunon to a plurality of toll trunk lines are alike in structure. The automatic selector switch G is provided with eight brushes a, b, c, d. e, 7', g, and 71, mounted upon a single shaft driven by a motor magnet hldl, initially controlled by a start relay 200 connected to the start conductor or start lead ST common to a group of trunk lines. Brushes c to 7L, inclusive, are connected directly with the respective individual sending segments l. to 6 of the sending distributor S. Brush a is connected with one windingl of stop relay 201 which controls the circuit of the motor magnet MM and the energization of the release magnet SRM of the sendingdistributor S. Brush Z) is connected with a contact of relay 202 for the purpose of assisting in the control otthe switch, as will more fully appear hereinutter. Relay 202 and a release relay 203, associated with the automatic selector switch G, are controlled by the sending distributor S tor reasons which will more tully hereinafter appear. A plurality of contacts, equal to twice the number ot toll trunk lines to which the automatic selector switch G is common, is associated with each brush on selector G. The contacts associated with the different brushes are mounted at different levels in position to be engaged by the respective brushes as they are rotated by the motor magnet MM, Two correspondingly positioned contacts o t all levels are allotted to each trunk line; tor example, the irst two contacts may be allotted to trunk line No, l, the second two to trunk line No. 2, etc. The two contacts ot levels a and Z) allotted to each trunk line, are connected with relays indi idual to and associated with the outgoing end of the trunk line. rl`he trunk line L has been shown associated with the iirst two contacts of each level of switch G. As shown, relays individual to the outend of this trunk line are connected by means otl individual signal control leads e, 205 and restoring leads 206 and 207 with the allotted contacts accessible to brushes (L and signal control leads 204; and 205 being connected to the respective first and second contacts of the level to which 1orush a. has access and restoring conductors 206 and '20T to the respective first and second contacts olf the level to which brush 7) has access. Each trunk line is provided with similar signal control and restoring` leads at the ottico similarly connected with the selector switch G. The automatic selector switches, shown in the drawing, are provided with sufficient contacts to accommodate thirty trunk lines. To the contact of the levels to which brushes c to 71, have access allotted to the respective trunk lines, are connected current sources oi the polarities in combinations as indicated in the tollowing table, there being a different coinbination for each trunk line and also tor the two contacts allotted thereto;

The automatic selector switch G allotted at the intermediate oliice Y, is like the switch Gr in structure and is associated with the sending` distributor S in the same manner as switch G is associated with the sending distributor S, with the similar start relay 200 and motor magnet MM and with switch G is associated with the toll trunk lineL, shown in the drawings, by means of' the individual signal. control leads 204 and- 205and restoring lead 206 and a common start lead ST, individual conductors 204 andl 205 being connected with the allotted first and second contacts ofl level a, individual restoring conductor or lead 206 with both allotted contacts of the level o and the common start conductor ST with the start relay 200 .ofV the switch G. The selector switclji`- G is associated With each `of the` other trunk lines through similar signal control and restoring leads, The polarities connected with the individual sending segments 1 to 6 of the sending distributor S are determined by the position of the brushes c to it of the switch G', andthe different combinations of polarities connected with4 the allotted first and second contacts of thelevelsto which brushes c to 7L have access for the various trunk lines are identical with those connected to the automatic selector switch G, as shown in the preceding table.

lIn order t-hat the signals transmitted from the originating office X by the sending distributor S and received at the office Y may be utilized, there are provided at the office Y six locking relays 41 to46 inclusive having energizing windings connected with the respective individual receiving segments 21 to 26 of the receiving` distributor R. When a negative impulse is transmittedfrom a particular individual sending segment, the relay connected with the corresponding individual receiving segment will be energized andxlocked up. Relays 41" to 44 control a plurality of receiving and selecting relays 50 to 64 inclusive which cooperate with relay 45 to select a signal control circuit individual to a'trunk line, while relay 46 controls the polarity of current connected with the selectedsignal control circuit. The individual signal control circuits are connected with contacts of relays to 64" inclusive. Similar' equipment is provided at originating oice X for utilizing the signalstransmittted from the intermediate office Yk over the common signal `conductor P.

The selector switch H, shown at the intermediate office Y, is of the step-by-step type similar to that disclosed in Goodrum Patent 1,231.013, issued lune 26, 1917. The finder switch, designated K, is of the well-known rotary step-by-step type and is employed to connect an impulse repeating? device indicated by the dotted rectangle 600 with the incoming end ofk a toll trunk line L. This repeater may be of' the type disclosed in Patent to rie lo.y 1,202,925 issued October 31, 1916.

The call indicator shown at I in Fig. 8

scribers station A, over toll trunk line L comprises a switches which, through transfer relays, are connected in succession to a local stepping circuit and are under the control of impulses repeated over the trunk line extending from the terminating office Z to the intermediate office Y by the repeater 600 at the office Y. Each of the step-by-step switches of the register is provided with a bank having ten terminals which are connected .with indieating lamps. The indicator I is associated with the trunks terminating in the office Z by means yof a step-by-step switch Mof the` well-known rotary type. t

The toll operators position in office Xj is provided vwith a high frequency impulse sending device diagrammatically shown by the dotted rectangle 10,0 and of the type shown in the patent to C. R. Englund No, 1,245,446 issued November 6, 1917, which is under the control of the operators impulse sending dial 101, This impulse sending device 100 may be associatedl with cord circuit F atl the operators position by `means of a key.102. Having in mind this brief description of the apparatus of the system shown in the drawings, itis. thought that the invention will be more thoroughly understood from a description of the operation of the system shown, and therefore a description of the method of extending a call from the'sub- 7 through the intermediate office Y, and toV the subscribers. station B in terminating offlee Z will first be explained.

The subscriber, whose substation is designated A., desiring to establish connection with theL subscriber, whose station is designated B, which line terminates in the terminating office Z, will, in any well-known manner, as through an originating operators position (not-shown) and a. switching trunk, obtain connection with ators position at ofiice X, shown in Fig. 1. The operator in response to the call inserts the answering plug 103 of the idle cord circuit F in the jack 104 of the switching trunk, thereby causing the energization of sleeve relay 105. Relay 105 upon energizing closes the tip strand of' the answering end of the cord circuit, thereby enabling the toll operator to converse with the calling` subscriber A, or with the operator at the originating office, as soon as the toll operator throws her listening key 106 to connect her head set with the answering end of the cord circuit F. Upon ascertaining that the calling subscriber A desires connection with the subscriber in an office which is accessible over the toll trunk L, the toll operator inserts the calling plug 107 of the cord circuit F inthe jack 108 of an idle toll trunk L, which is selected by testing in the well;- known manner. v

plurality ef rotary stepfbrstep los the toll operleo e A. circuit is now established extending from grounded battery through the winding or marginal sleeve relay 109, the right-hand Winding ot' relay 110, over sleeve conductor 111, through the sleeve contact ot plug 10T, the sleeve contact otjack 108, the Winding of relay 208, and thence to ground through the Winding of marginal relay 209. Relays 110 and 20S operate but relays 109 and 209 do not operate at this time, owing to their marginal nature. Relay 208, upon energizing, closes a circuit 'for relay 210, which circuit may be traced from grounded battery through the inner left-hand armature and back contact of relay 211, the Winding of relay 210, and thence to ground through the front contact and armature of relay 208. Relay 2107 upon energizing, closes a locling circuit 'for itself extending from grounded battery through its inner lett-hand armature and front contact, the Winding ot relay 210, and thence to ground at the armature and :tront contact ot' relay 208. Relay 210 also closes an energizing circuit tor relay 211 Which may be traced from grounded battery through the outer left-hand front contact ot relay 210, and thence to ground through the left-hand Winding of relay 211. Relay 211, upon energizing, closes a locking circuit for itself extending through its inner lett-hand armature and t'ront contact, and opens at the back contact ot this armature the initial energizing circuit of relay 210.

Upon the energization of relay 211, ground is connected to the start conductor ST over the intermediate left-hand armature and front contact of relay 211, the.

right-hand armature and back contact of relay 212, and the right-hand armature and back contact oit relay 213, and ground is connected to signal control conductor 205 over the outer left-hand armature and front contact of relay 211, the outer right-hand armature and front contact ot relay 210, the

` left-hand armature and back contact of relay 212, and the outer left-hand armature and back contact of relay 213.

"Relay 200 nonv energizes over conductor ST and closes a circuit tor the motor magnet MM extending from grounded battery through the armature and contact of magnet MM, the left-hand armature and back contact of stop relay 201, and the front contact and armature ot relay 200. Motor magnet MM, upon energizing in this circuit, advances the brushes ot the distributor switch G over their respective levels of con tacts until the brush a linds a grounded conductor 205 corresponding to a toll trunk which has been taken for use by the toll operator. Assuming that the conductor 205, corresponding to the toll trunk L, is the first grounded conductor to be encountered bv the brush a, a circuit is established for the stop relay 201 extending 'trom grounded battery through the left-hand Winding of this stop relay, through the brush a, over conductor 205, and thence to ground as previously traced at the outer left-hand armature of relay 211. The stop relay 201 upon energizing, opens the circuit of the motor magnet MM and thereby arrests the movement of switch G. Relay 201 also closes a lockingcircuit for itseltl extending from grounded battery at the armature and back contact otl release relay 203, through the inner right-hand armature and front contact of relay 201, and the right-hand winding thereof to ground. Relay 201 also closes a circuit 'for release magnet SRM ot the send ing distributor S, which circuit extends trom grounded battery through the ring 15, the inner brushes of the brush-arm 9, segment 16, the front Contact and outer righthand armature of relay 201, and thence to ground through the winding of the release magnet SRM. The attraction ot the armature ot the release magnet SRM, upon the energization thereof, releases the brush-arm 9, which is thereupon rotated through a complete cycle, at the end ot' which the brush-arm is stopped in its normal position. The brush-arm 9, in being rotated. first engages start segment s, thereby connecting positive current With the common signaling conductor P.

Brush-arm 9 then moves out of engagement With segment 16, thereby opening the energizing circuit of and causing the deenergization of release magnet SRM, which restores its armature to normal position preparatory to stopping the brush-arm when it reaches its normal position. From an inspection of the table ot polarities it will be observed that when the switch G stopped with its brushes in engagement With the irst of the two contacts in the several levels, allotted to trunk line L, that positive current is connected with such lirst contacts on levels c, d, f, g, and h, While negative current is connected with such first contact ot level c.. Vhen the inner brushes on brush-arm 9 engage segment 17, a circuit is closed extendingfrom battery through ring 15, the inner brushes on arm 9, segment 17, and thence to ground through the Winding ot relay 202. This relay, upon energizing` closes a circuit extending from grounded battery through the armature and back contact o1" relay 203, the armature and Vtrout contact ot relay 202, over the brush Z) ot switch G, conductor 20G, winding of relay 213, right-hand armature and bacl contact of relay 212, and thence to ground through the left-hand intermediate armature and front contact of relay 211. Relay 213 energizes in this circuit and at its inner lett hand armature establishes a locking circuit for itseliz independent ot the circuit extendieri kes

43 and thereby the circuit through the windings of relays 5l and 5". The circuits or thesignal receiver are now in normal position' in readiness 'for the receipt and translation of other code signals. It is to be noted that during the rotation o1 the receiving distributor, relays 41', 42, 44, 45', and 46 were not Aenergized inasmuch as relay 256 was holding its armature against its alternate contact at. the time the brushes on switch arm 10 were passing over segments 21', 22', 24', 25, and 26 con nected respectively to these relays.l

Relay 400 at the intermediate oi'lice Y, upon .energizing over the circuit traced through conductor 500, closes a locking circuit for itselic extending from lgrounded battery through its right-hand winding, and

to ground through its inner right-hand ar-v mature and front contact. The energization of relay 401 is without ellfect at this time and this relay deenergizes as soon as the receiving distributor R reaches normal position and opens the circuit over conductor 500. Relay 400, upon energizing, valso bridges the polarized relay 402 across the incoming end of the t-oll trunk line lL, through its outery armature and front contact, and at its inner armature and front contact closes a circuit extending through the right-hand armature and back contact oi' relay 401, and through the winding of slow-releasing relay 403. The energization of relay 403 is without function at this time. A circuit is `also established from battery at the inner arman ture and back contact oit relay 601, the winding of relay 602, conductor 606, conductor 404', and thence to ground at the inner armature and 'front contact of relay 400.

Relay 602 energizes in this circuit, if relay 601 is at the time deenergized, closing a circuit extending from grounded battery through the Winding Vof starting relay 604, the armature and front Contact or" relay 602, and thence to ground through the left-hand armature and back contact of relay 605 and resistance 606.' Selectable potential is also connected over the circuit above traced to the lowermost bank contact 607 of finder switch K. y

Upon the energizatiou of relay 604, a circuit is closed through the motor magnets 608 of all linder switches which are at the time idle. A circuit for the motor magnet of finder switch K, shown in Fig. 6, may bel traced from grounded battery through the motor magnet 608, the armature and back contact of this magnet, `the armature and back contact of stop relay 609, and thence to ground at the armature and front contact of relav 604. The inder switches which are started up will continue to move their brushes over their respective banks of contacts, which contacts are individual to ously traced to the contact 607,v thence overy brush 610, and to ground through the winding of stop relay 609. Relay 609 energizes in this circuit opening at itsouter armature and back contact the circuit extending through motor magnet 606, and at its inner armature and front contact closes a circuit extending from grounded batterythrough the winding of relay 611, and thence to ground at the inner armature and front con'- tact oit relay 609. t

`Relayv611, upon energizing, connects the input side ofrepeater 6 00 over its armatures and front contacts, brushes 612 and 613 of linder switch K, contacts 614 and 615 with which they are in engagement,

thence over conductors 616 and 61'?, through Y the intermediate and outer leftehand armatures and bacl-r contacts of relay 601 to the y tip and ring conductors of the toll trunlr A circuit is also closed at this time from grounded battery through retardation coil l 616, the upper armature and front contact ol relay 611, brush 612, contact 614, conductor 616, the intermediate armature and back cont-act of relay 601, the/inner armature and back contact of relay 405, the upper right-hand winding of `repeating .coil 414 the windings of polarized relay 402, the outer armature and front contactof relay 400, the lower right-hand winding of re-y peating coil 414, the outer left-hand'armature and back contact otrelay 405, vthe outer left-hand armature and bacl; contact or' relay' 601, conductor 617, bank contact 615 of linder switch K, brush 613, the lower armature and front contact of relay 611, retardation coil619,v and thence to ground through the ,winding of-relay 609. A circuit is also established at this time for relay 605, which circuit may bev traced from grounded battery through the inner armature and back contactol relay 601, wind-y ing of relay 605, bank contact 620, brush 621, and thence to ground through the inner armature and front contact of relay 609; Relay 605, upon energizing, opens the circuit of relay 604, which, if there are no other incoming calls on other trunks ofthe ing through brush Z1 of switch Gr, at its outer lett-hand armature opens the circuit extending over conductor 205, and at its right-hand armature opens the starting conductor ST.

As the brush arm 9 successively moves its brushes over the individual sending segments 1 to G, current sources oi the polarity connected with these segments are successively connected with the conductor l). When the brush-arm 9 moves its brushes out of engagement with segment 17, the energizing circuit of relay 202 is opened, and upon the engagement oi' the inner brushes on brush-arm 9 with segment 18, a circuit is established for release relay 203, which extends from grounded battery through ring` 15, the inner brushes on arm 9, segment 18, and thence to ground through the winding of relay 203. Relay 203, upon its energization, opens the locking circuit of relay 201, whereupon this relay releases As the brushes on arm 9 move out ot engagement with segment 1S, release relay 203 is deenergized. When the brushes on brusharm 9 engage the restoring segment r, current of negative polarityis connected with the common signaling conductor P, and the automatic selector switch G now in condition to be seized by another trunk since the trunk line L is now disconnected therefrom and the sending distributor S is in normal condition.

rIhe connection of positive current .trom segment s with conductor P does not affect differential polarized relay in oilice but causes the operation of the differential polarized relay 25 at the intermediate ottice Y over a circuit extending from positive battery through segment s, the outer set ot brushes on arm 9, the common sending ring 14, and the unction point between .the windish ings of differential polarized relay 25, then by one path through the lower winding of relay 25 and artificial line AL to ground, and by another path through the upper winding of relay 25 conductor P, both windings of the dil'erential polarized relay 25 and the articial line to ground` The operation of relay 25 establishes al circuit extending from grounded battery through the alternate contact of relay 25, segment 29, the outer set of brushes on arm 10 of the receiving distributor switch R, segment 30 and thence to ground through the winding of release magnet RRM. The attraction of the armature of the release magnet. upon the energization thereof releases the brush-arm 10, which is thereupon rotated through a. complete cycle at the end ot which the brush is stopped in its normal position` As the brush-arm 10 moves its brushes out of engagement with the segments 29 and 30', the circuit extending through the release magnets RRM is opened, and the magnet deenergized, permitting the restoration .of its armature to normal position preparatory to stopping the brush-arm when it reaches its normal position. vWhen the brush-arm 10 moves its inner set of brushesinto engagement with the segment 32, a circuit is established extending trom grounded battery through the ring 31', the inner set of brushes on the brush-arm 10, segment 32, and thence to ground through the winding` of relay 82. `lelay 82 thereupon energizes, connecting atv its armature and front contact a holding ground to the conductor S3', which is common to the locking circuits of relays el to 46 inclusive. rfhe armature of the polarized relay 25 remains in its alternate position as long as positive current is connected with the other end of conductor P and moves to its normal position whenever negative current is connected with the other end ot conductor P.

The brush-arms 10 and 9 are rotated synchronously, and whilebrush-arm 9 positions its brushes in engagement with segment 3 of the sending distributor S, to which negative current is connected, the armature oi relay 25 moves to its normal position and brush-arm 10 positions its brushes in engagement with the receiving segment 23. Relay L13 is thereupon energized over a circuit extending from grounded batteryv through the normal Contact of relay 25, segment 19 of the distributor R', the outer set of brushes on brush-arm 10, segment d3', and thence to ground through the lower winding of relay 43. This relay, upon energizing, locks itself to the grounded conductor 83', through its upper winding and its upperarmature contacts. At its lower armature and front contact, relay 43 closes a circuit extending from grounded battery through the windings of relays 5., and 51', which thereupon energize. Then the brush-arm 10 positions its brushes upon segments 2i" and 28', just prior to reaching its normal position, a circuit is established extending from grounded negative battery through the lower armature and back contact ot relay 46', through segment 27, the outer set of brushes on brush-arm 10, segment 28', the lower armature and back contact of relay 4-5, the lower armature and baclr contact ot' relay 50, the lower armature and front contact oit' relay 51, the upper armature and back Contact of relay 53, the upper armature and back contact of relay 58, thence over conductor 500 which is individual to the toll trunk L, and to ground through the left-hand winding of relay 400 and the right-hand winding of relay l101. As soon as brush-arm 10 moves its brushes beyond the segments 27 and 28, the circuit existing through the winding of relay 82 is opened, and this relay dcenergizes opening the locking circuit ot relay oiice selector switch H, this circuit extending'from grounded battery through the of relay 62.2.'Relay 622,-'I upon energizing,

closes a circuit for slow-release relay 628, which may-betraced from grounded .battery lthrough the winding of this relay, `and thence to ground through the armature Vand front contact of relay 622. The circuits of the repeater 600 and of thev office selector switch H are n ow in condition .to receive directive impulses for causing lthe selection of the desired terminating .oice

When relay 611 energized and established a circuit through the winding ofpolarized relay A402, said relay energized in such a manner as to move its armature into engagement with its let-handncontact, thereby closing a circuit for slow-releasing relay 406, slow operating relay 407, and relay 408, and causing the energization. of these relays. A circuit for relay 406 may be traced from grounded battery through the winding of v.this relay, the armature and lefthand contact of relay ,402,- and thence to ground at the inner armature and front contactof relay 400. ,The circuit of relay 407 may be `traced ,from vgrounded battery through the winding of this relay, the norinally closed make-before-break armature contacts ofthis relay, the right-hand armature and back contact of relay 409, the outer right-hand armature and back contact of relay 410, the armature and left-.hand contact of relay 402, and thence to ground at the armature andcontact of relay 400. Re. lay 407, upon energizing, closes a locking circuit for itselt'through its right-hand armature and make contact, the outer .left-1 hand armature and back contact of relay 411, and ,thence to ground over the circuit previously traced, through thearmature and left-hand contact of relay 402. Relay 407 thus remains under the control of relay 402 until relay 411 is operated. The circuit of relay 408inay be traced fromY groundedbattery through the windingV of relay ,412, the v Vouter left-hand armature andback contactofrelay 409, the winding of relay 408, the

break contacts ofits inner right-liand armature, the lefteliand armature and/back contacts of relay 407the right-hand armature andback contact of relay 409, and thence tovground over the circuit previously traced,

through the armature contactsjof relay 402. Since relay 407 is slightly slowrto energize, the circuit of relay 408 is estab-k lishedy before relay` 40'( energizes to'open its left-hand armature contacts. Relay 408, upon energizing in the circuit previously traced, closes a locking circuit for itself, extending` through the winding of relay 412 left-'hand armature and back contact of relay 409, its own winding and the make contacts of its inner right-hand armature lto ground.

The energization of relay 406prepares a circuit for the slow-releasing relay 413, which circuit extends to 4the right-hand armature Contact of polarized relay 402, and isclosed as soon as the directionk of current flow .is reversed throughthe winding of relay 402. Relay 408, upon energizing, closes a circuit for relay 420 extendinofrom grounded vbattery through the winding of relayv420, the left-hand armature and back contact of relay 419, and thence to ground at the inner left-`hand armature and front contact of relay 408. Relay 420 energizes in this circuit and closes a locking circuit for itself, extending through its armature and front contact, the winding of ielay419, the inner right-.hand armature and back contact ofrelay 410 to ground at the inner armature andy front contact of relay 400.y

Relay 419, however, does not energize in this circuit since its winding is shunted by ground at the armature and contact of relay 408. Relay 412, which energized in series with relay 408 upon energizing, closes a cir-k cuit for the start relay 200` of the selector switch G', which, upon energizing, closes a circuit for lthe motor magnet MM of this switch, which circuit extends from groundl edbattery through armature and back contact and winding of the motor magnet,

through the right-hand armature and back contact of stop relay 201', and thence to ground through the armature and front con tact of relay 200. The switch G is thereupon started to move its brushes over their respective'levels of contacts, until the brush a engages the contact connected by conductor 205 to ground at the outerlett-hand armature and front contact of relay 408, this conductor being individual'to the incoming end of the trunk line L, when va circuit .is established through the right-hand winding of stop relay 201. This stop relay` energizing in this circuit, opens the circuit of the motor magnet MBL', and closes a locking circuit for itself,` extending from grounded battery through the armature and back contact of relay 203, through the Vinner left-hand armature and front contact and left-hand winding of relay 201r to ground. At its outer left-hand armature and front contact, stop relay 201 closes a circuit extending from grounded battery through the ring 15', the inner-brushes on brush-arm 9', segment 16', the outer leftllO ' grounded battery through the and in the manner previously described inv connection with the sender distributor S, transmits a code ot signals comprising two positive, a negative, and three positive iin pulses, which are received by the receiving distributor R at the originating oiiice X to lock up relays 43, 51 and 52 in the saine' manner as previously described in connection with the receiving distributor R. The send ing distributor Sl, after leaving its normal position, closes a circuit :tor rel-,ay 202, extending from grounded battei'y through the ring 15', the inner set of brushes of the briish-arm 9, segment 17 and winding of ielay 202 to ground. Relay 202', upon energizing, closes a circuit extending from armature and back contact ot relay 203, the armature and front contact ot relay 202', over the brush 7) having access to the second level of selector G', conductor 206', and thence to ground through the winding ot relay 409. Relay 409, upon energizing, opens the circuit ot relay 408, causing the deenergization of this relay. The shunt around the winding ot relay 419 is now opened and relay 419 energizes in the locking circuit ot relay 420 for a purpose to be described hereinafter.

The receiving distributor R, it will be understood, is started at the time sending distributor S is started and rotates in synclironisin therewith, and ust before reaching l its normal position closes a circuit extend ing from grounded negative battery through the lower armature and back contact of relay 46, the segment 27, the outer set et brushes of the brush-arm 10, segment 28, the lower armature and back contact ot relay 45. the lower armature and back contact of relay 50, the lower armature and front contact ot relay 1, which together with relay 52, was energized by the operation ot relay the upper armature and back contact ot relay 53, the upper armature and back contact of relay 58, thence over conductor 300 to ground through the right-hand winding or" relay 214. Relay 216 does not operate Vat this time over conductor 300, since its circuit, which is normally in parallel with the winding` oi" relay 214, is opened at this time through the armature and back contact ot slow-releasing relay 215 this relay having been previously energized bythe operation ot' relay 208. Relay 214, upon energizing in this circuit, closes a locking circuit tor itself extending from grounded battery through its lett-hand armature and front contact. its lett-hand winding, and thence to ground at the armature and front contact ot hand armature and back contact et relay 216,

through the right-hand armature and front contact oit relay 214, through resistance 217,

and thence over the sleeve conductor ot the trunk circuit L, through the sleeve et ack 108, sleeve ot plug 107, conductor 111, winding ot relay 110, and winding oi marginal relay 109 to grounded battery. The connection oit resistance 217 in parallel with' the windings of relays 208 and 209 changes the resistance ot the sleeve circuit sufficiently to permit the operation of marginal relay 109 of the toll cord circuit F, which relay, upon energizing, closes the circuit of the lamp 112` which at this time serves to give the toll operator a. dialing signal to apprise her ot the tact that the finder switch K has associated an impulse repeating device 600 with the incoming end ot the toll trunk line L, and that she may now proceed to dial the digits required to set the switch H on the tern'iinals ot the trunk line extending to the desired terminating oflice Z, and the digits required to set up the number ot the desired line in this ottice upon the lamp indicator I.

It will be assumed that the calling subscriber desires connection with the line ot the called subscriber l, whose directory number is 1920 -J. rllie toll operator will thereupon throw her dialing key 102 to connect the impulse sending` device to the strands ot the cord circuit F. Upon throwing the key 102 acircuit is closed 'from ground through contacts 113 of the key. and through the lett-hand winding of relay for holding this relay positively energized during the transmission et the dialing impulses to in sure that the tip strand of the calling lend oi the cord circuit is maintained closed. At its lowerinost alternate contact 114, the key 102 closes a circuit extending trom grounded battery directly to the sleeve conductor 111. in parallel with the windings of relays 109 and 110, which so increases the flow ci cur rent over the sleeve conductor that marginal relay 209 now becomes energized. Relay 109 releases while the dialing key 102is operated, and extinguishes lamp 112. Relay 209, upon energizing, closes a circuit for relay 212, er;- tending from grounded battery through the winding ot relay 212, and thence to ground through the armature and front contact oit relay 209. Relay 212, upon energizing, opens the locking circuit of relay 213, permitting relay 213 to deenergize, thereby connecting start conductor ST and the impulse control conductor 205 to the back contacts of the CII lll)

designation of the desiredline for setting the ofiice selector switch H. When the dial is released after itsinitial setting and returns Y to normal, the circuit of lrelay 115 is intermittently opened, thereby causing the lassociation of the impulse sending 'device 100 with the impulse conductors 11,6 and '11.7, a number of times corresponding `to the-setting of the dial, and sinceatthe ytime the operator listened -in onfthe connection'f'by throwing 'the listening key 106, the Vrelay i1118 was energized-over a circuit extending from battery through :the winding of this relay and the alternate contacts 119 of key 106, the impulse conductors 116 and 117, are now connected over contacts 120 and'121 of the dialing'lrey 102, through the tipand ring strands of the cord circuit F, over; the tip and ring contacts of the plug 107 and -the'jack 108, and thence to thetip and ring conductors of the toll trunk line "L Upon the movement of the dial 101 oli' normal, the off normal contacts 122 vof the dial closea circuit extending from vgrounded ibattery through these contacts, the left-hand armature and front contactot relay 1115,andto groundthrough the winding of slow-releasing relay 123, which, due toits slow-releasing character, maintains a circuit forthelamp 124'solong as the diallOlis oifnormal. I The sending device vis designed 'for transmitting high frequencyalternating current'impulses out over'the toll trunk, these impulses having-a lfrequency of preferably 800 cycles. 'These impulses are repeated through the several repeating coils of the trunk circuit `L andflow throughthe input circuit of therrepeating devicef600 atgthe intermediate oiice Y. These impulses, throughy the well-known construction ofthe repeating Vdevice 600, `cause the intermittent operation of the repeating relay V629. Y Upon each'energization, relay 629 closes a circuit extending 'from grounded battery through the winding of relay 625,' over bank contact 630 of the {inder-switchK, wiper631, and thence to grou-ndA at the armature and front contact vof relay`629. Upon each energiza? tion, relay 625 opens the bridge ofthe'incoming end of the trunk circuit L, extending throughv the resistance 626, thereby causing the deenergization of line relay ',622 of the selector switch H. vUpon each deenergization a circuit is closed from grounded battery through the winding of vertical stepping magnet 632, winding oftheislow-releasing relay 633, theleftlhand armature and front contact of slow-releasing relay 628 which,

because otits slow-releasing character, does not deenergize upon short openings of its circuit at thearmature and front contact of relay l6,22, thence through the right-hand armature and back contact of relay 623 to ground at the back contact of line relay A622. In response to each ldeenergization of line relay 622, vertical magnet 632V steps the switch shaft of the selector switch H up one step. Slowreleasing relay 633, which energizes in series with stepping magnet 632,

upon its initial energization close a circuit extending from grounded 'battery through its armature and front contact, and thence to ground through the winding of private relay 634. This circuit is maintained until thestepping impulses cease, and since Von the lirststep off normal of the switch the off normal contacts ON were closed, the relay 634 is now maintained energized over a locking circuit extending from grounded battery through the right-hand armature and front contact of relay 628, the lefthandv armature and back contact or" the rotary magnet 635, contacts 636 of the oi normal switch ON, the left-hand armature and front contact and winding of relay 634L to ground. The relay 634- is therefore maintained energized after the vertical movement of the selector switch yshaft has Vbeen com-y pletedand the relay 633 has released its armature. l

yUpon the deenergization of slow-releasing relay 633 follow-ing the termination of the lirst group of impulses, a circuit for the rotary'magnet 635 is closed extending from grounded battery through the right-hand armature and front contact of relay 628, the left-hand armature and back contact of rotary magnet 635, contact 636 of oil normal switch ON, left-hand armature and front contact of relay y6311, armature vand back contact `of relay 633, right-hand armature, back contact and winding of rotary magnet 635 to ground. Rotary magnet vv635 energizesin thisficircuit -and interrupts itsown circuit at its armature contacts, thereby stepping the switch shaft one step inthe rotaryidirection.k Rotary magnet 635 also opens the-holding circuit of the private relay 6341 at itsleftehand'armature contacts, and private relay 634 deenergizes unless the test wiper 637 of the selector switchis at that timein engagement with the test terminal of a busy trunk extending to the desired oice, in which event this test terminal will beconnected to grounded battery. Thus, so long as the test wiper 637 engages the ter` ininals ofibusy trunk lines, `private vrelay 631- will be maintained energized and rotary magnet 635 will continue to step the wipers of the switch over the selected row of trunk terminals, until the terminals of an idle trunk line are found when relay 634edei energizes, permanentlyI opening the stepping circuit of theV rotary magnet A635.

' When the testvwiper637 stops on a contact associated with an' idle-trunk, which trunk

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