US2388136A - Party-line printing telegraph system - Google Patents

Description

Oct. 30, 1945. A. GARDNER ET AL PARTY-LINE PRINTING TELEGRAPH SYSTEM Filed May 14, 1941 'I'Sheets-Sheet 2 L.;4.GARDN R WVENTORS- KWR/CHARDS ATTORNZLY L. A. GARDNER El AL.

PARTY-LINE PRINTING TELEGRAPH SYSTEM Filed ma 14 1941 7 Sheets-Sheet 3 ATTORNEY Oct. 30, 1945. L. A. GARDNER ET AL PARTY-LINE PRINTING TELEGRAPH SYSTEM 7 Sheets-Sheet 4 Filed May 14 1941 M/VENf s K n. RICHARDS 1 M23. c A

A 7'TORNEV L. A. GARDNER ET AL 2,388,136

Filed May 14,. 1941 '1 Sheets-Sheet 6 P N 7 l I 8 h 8 E ME W NE QE RR 7 wk MR QR QR WNN kzwkosu 282E 58w 3 Oct. 30, 1945.

' PARTY-LINE PRINTING TELEGRAPH SYSTEM LA. GARDNER wl/gvyroR K W RICHARDS A 7'7'ORNEY Oct. 30, 1945. L, A. GARDNER ETAL I BARTY-LINE PRINTING TELEGRAPH SYSTEM Filed May 14, 1941' '7 Sheets-Sheet '7 Patented Oct. 30, 1945 PART LINE PRINTING TELEGRAPH SYSTEM Ileland A Gardner,,Maplewood, and Kenneth .W.

Richards, Packanack Lake, N. J.; said Gardner assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York, andsaid Richards assignor to American Telephone and Telegraph Company, a corporationof New York Application May 14, 1941, ,Serial No. 393,324 (01. 173-2) 9 Claims.

JI'his invention relates to a communication system for transmittingsignaling impulses over telegraphlines or channels and more particularly to a telegraph system for connecting a plurality of outlying ,telegraphsubscriber stationsto a centralcrexchange office overa single telegraph line, channel ortrunlc.

An object of the, invention is to provide a plurality -,of subscriber stations with teletypewriter switching service over 'asingle line, channel or Another object of the invention is to lock out, or? prevent; a'subscriber station of a party-line groupfrom using a line, channel or trunk when another of the subscriber stations is operatively connected to thesame line, channel or trunk.

Another object is to utilize a telegraph line, channel or trunk of the repeatered type as a means of operatively extending through a local control, or switching, center, any one of a plurality of subscriber stations to a remote central office thereby giving the subscriber a party-line service over said line, channel or trunk.

\ Another object of the invention is to permit at anyone time one only of a plurality of subscriber stations to be operatively connected at theswitching center to a telegraph line extending through one or more'repeater stations tola telegraph exchange ofllce.

l 1 Another object is to provide a system responsive to-cbde ringingiwhereby any one of a plurality of subscriber stations may be operatively 'connected through the switching center to a line, channel or trunk, to the exclusion of the other of said subscriber stations connected to the same line, channel-or trunk.

l Another object is to provide a system whereby anyone of a plurality of subscriber stations may be'operatively connected through the switching center to a multis'ection line, channel or trunk extending to a teletypewriter exchange ofiice;

Another object is to provide a system having a plurality of subscriber stations connected to the switching center with means thereat for operatively connecting anyone of said stations, to the exclusion of the other of said stations, to a multisection line, channel or trunk extending through a pluralityofrepeater stations, in series, and a source of busy signals at said switching center for automatically informing a subscriber at one or moreof said subscriber stations when another of saidsubscriber stations is operatively connected to said line, channel or trunk.

Another object is to provide a system in accordance with the immediately preceding object wherein the busy signals transmitted from said source are in permutation code. According to an embodiment of the present invention a multistation teletypewriter line is connected to a teletypewriter exchange oflice. Three or more subscriber stations may be connected, in parallel, to a switching, or control, center by one ortwo wires-and the switching centermay be connected by a single wire of the single or multisection type to one or more repeater stations, in series, for repeating communication signals to the teletypewriterexchange oifice. A codecringing source is provided at the switching center whereby calls may be made to any one of a plurality of subscriber stations connected to the line on the basis of one, two and three rings respectivelyassigned to such stations. A source of busy signalsis provided at the switching center for transmitting to each of a plurality of subscriber stations permutation code signals, such as a series of letters or other known characters should any subscriber at such stations attempt to establish a connection to the line at a time when the line is in use by a subscriber at another of said stations. The idle stations of said plurality are prevented at the switching center from being operatively connected to the linewhen one of said subscriber stations is operatively connected to the line.- i r M A feature of the invention is the provision of a system wherein each of a plurality of subscriber stations "may be connected to the switching center by one or two single-wire circuits and either of such two arrangements may be operatively connected over a single-wire, single or multisection line extending to the teletypewriter exchange ofiice, each section of such line being operated half duplex employing current reversals in one direction-and difierencesof current in the other direction.-

The imention will now be described with respect to the accompanying drawings whichillus of a single wire each between each of the subscriber station-s and the switching center, and a multisection line interconnecting the switching center and the teletypewriter exchange cities.

The drawings areas follows: Fig. 1 shows three toll line subscriber teletypewriter stations A, B and C. Station A is shown stood that the equipment at eachof stations B and C is the same as that shown at station A with the exception that stations B and are equipped for attended station service only,

Fig. 2 shows the equipment, in schematic term at the switching center located in the community of subscriber stations A, B and C. It will be noted that each of the subscriber stations A, B and C is connected to the switchingcenter by two wires, one for transmission and signaling and the other for control purposes. The equipment at the switching center provides code ringing for calling the subscriber stations.

I Fig; 3 shows a single-wire circuit connecting the switching. center. to a toll line extension circuit terminating equipment located in the distant teletypewriter exchangaofiice; The terminating equipment includes a repeater. Also in Fig. 3 are shown in diagrammatic form the equipment at th'e teletypewriter exchange. office. and the equipment at a local subscriber station connecting directlyto the. office.

Fig. 4 shows the relative arrangement of Figs 1, 2 and 3. 1 "Fig. 5 shows three toll line subscriber. teletypewriterstationsAZ B" and C'. Station A isshown in schematic form and each of stations B and C is shownin diagrammatic form, it being understood that the equipment at each of stations B andC. is the same as that shown at station A ex'ceptthat stations. B and C are equipped for attendedserviceonly.

Fig. 6 shows the equipment, in schematicform, at the switching centerlocated inv the community otsubscriher. stations A, B. and C. It will be noted that each of subscriber stationsA, B and C! .isconn'ected to. theswitching center by a single wire which isutilized forthree-functions, namely, transmission, signaling. andcontrol. The equip; ment at thi switching center provides code ring.-. in'g. f.or..ca11i the. subscriber tat ons.

Fig.7.. showsthee u pment, in schemat c form, atan. intermediate repeater point a mu tisece tion line. ircuit withwi ing adapt d r usev wit coderin ing.

Fig. 18; shows the. single-wire multisection line terminating. in a switchboard, at the teletypewriter exchange. ofiice. Also in Fig. 8- are shown in diagrammatic form. th equipment at the xchan e. office. and. the. equipment at a. local-51 scriber station connected directly to the exchange office.

. Fig. 9, shows the. relative arrangement of Figs.

la d SYSTEM X RESQ N:

' Inasmuch as-station A is shown in detail, and stations B andC aresubstantially-similar to station 'A, anescr-iption of the equipment employed a t' station Aand" the method oi operation of such equipment is believed to be sufiicient for a description'and method-of operation of the equipm'e'n't'at each of; stations'B-and C which are shown in diagrammatic iorm. Station A is connectedto the switching center bytwo conductors I0 I and I02. Stations B and C and similarly colinected by their respective pairs of conductors I03 and I04, and I05 and I06. The upper conviding unattended station service, if desired, and

is identical with Fig. 1 of United States Patent 2,143,000 granted to W. W. Cramer et al. on January 10, 1939, except that the power switch at station A has an extra pair of contacts for grounding control conductor I02. The equipment at each of stations'B and C is identical with Fig. 5 ct United States Patent 2,143,000 except that no facility for unattended station service is provided, stations B and C being arranged to operate on the basis of attended station service only.

Fig. 2 shows a schematic circuit arrangement ofthe equipment located at the switching cent er- Common to stations. A,.B and C is a source 201; of continuous ringing current for calling by code any one of: the subscriber stations, for exam.- ple, one ring for station A, two rings for station B andthree. rings for station C. At station. A which is equipped for both unattended and attended station service, relay 1:48 is responsive to one prolonged ringing signal as compared with the one ringing signal of short duration used when the station is arranged as an attended station, Also, common to stations A, B and C is a busy signal source. The busy signal are trans.- mitted bythe alternate. operation and release of relays 202 2031 and. 2&4 to. produce a series. of letterssignals at the teletypewriter of a sub. scriber at one of the. stations, whereat an attempt is made to call by turning on the. power switch when the line to. the switchboard is in use. by a subscriber. at one of the other stations. Line relays. 205 206 and 201: are respectively provided for stations A, Band C' and; utilized when operated for controlling an established connection be-. tween the respectively; associated subscriber, stations and line. 208;. Relay 20.9. when operated by any. one. of the line. relays. servesv to connect the source at busy signals over the. normal contacts ofany one. or more. of the. line relays. which are in normal condition at the time. Theso ime 2.0] of continuous ringing current is. under control. of alternating current relay 1H and; slow-release relay 2 ;l:3-.

Barty. ormultistation. n 2.01 s. of; the s n ewire type and. represents. the toll line. x ension circuit arranged fer-connection throuehthe con.- trol, or switching, center to. any one of: stations A. and; aine 13. erm na es e. repeat Qft e .01 11" termina in quinrnee te the r.- erators. swi hboard. nv he te e rhewr ter x.- chang oflice, the toll: line terminatin u pment including Jack; 3115. =e toll line terminatin equipment he-s .;.-I; tn P a. Qi- Unit S ate Ba ent ..lri3,1 QQ.;s1 p ran ed-s n proximity to. jack; 3.05 is operators cord c rcuit 3.06;.and; perators pos tion circuit 1, hath o win :maytbe similan es 3 and 4., respectiveht .zeeaaqc. Another Jack 3001 at. the. operators. switchboarct is part of a local; subscrib ers. line-terminatin equipment. 309 which. in: turn, is. conn'eotedtby means of, conductors.- 301k and 3 it tothe. local. subscriber s station D. The local subscriber-sline-terminatingequip, ment and: the local.subscriber sstationnlmaya be similar to;Fig. 5;.ofiUnited States Patent; 2 ,l.' 43000. Other line terminating. equipment-"suchias those METHOD or OPERATION Operator calls Assuming that a connection is desired with one of subscribers stations A, B and C, the operator connects one of several cord circuits such as cord circuit 305 to jack 305 and then operates a ringing key (not shown) associatedwith cord circuit 306, say one operation of the ri'ngingkey for stationA, two operations for station B and three operations for station C. Station A which has assigned to it one interval of ringing current is shown as being arranged as hereinbefore stated for both attended and unattended station service because ofits having one ring signal only. For unattended station service, the one ring signal will be for a prolongedinterval sufiicient to operate slow-to-operate relay I49, relay I48 operating first and then followed, in turn, by relays I49 and I50. Relays I49 and I50, upon operating,

energize rectifier I I4 and start teletypewriter motor II5. Stations B and C are arranged for attended station service only and therefore have no'relays corresponding to relays I48, I49 and I50 or motor stop contacts corresponding to those designated I5I. This ringing current is transmitted through toll line terminating equipment, 30I and line conductor 208 to the switching center; Should the call be to station A, one normal operation of the ringing key (not shown) would cause one interval of ringing current to be transmitted over the innermost lower armature and back contact of each of line relays 205, 206 and. 201, in turn, conductor 2I0, through the winding of alternating current relay'ZII, condenser 2I2 to ground. Relay 2 would operate in response to the ringing current and thereby operaterelay 2I3.

Relay 2 I3 which is of the slow-to-release type, upon operating, closes at its armatures and contacts three circuits extending from common source 20I of continuous ringing current, through the indicating lamp .2I4, over conductors 2 I5, 2 I6 and 2| I, in parallel paths respectively extending over transmitting conductors IOI, I03 and I05 to the ringer at each of stations A, B and C, the ringer at station A being designated II.

The subscriber at station A upon identifying the single interval of ringing current will respond by operating power switch I08. Power switch I00, upon being operated, completes a path from grounded alternating current source I 00, conductor IIO, middle contacts of the switch, conductor III, through the winding of relay II2 to ground. A path, parallel to that extending over conductor ,l I I, extends over conductor I I3 through rectifier Ill and printer motor H5 in parallel. Rectifier III is energized and printer motor II5 starts operating Relay II2, upon operating, closes a circuitfrom line IOI, through recall key H6, testout key I", armature and contact of relay II2, resistance I I8, through the upper winding of receive relay II9, resistance I20, retardation, or choke, coil I2I, resistance I22, armature and marking,"or lower, contact of. send relay I23,

causes current to flow in two parallel paths, one

extending from the positive terminal of the rectifier through the right-hand biasing winding of send relay I 26 and'the left-hand biasing winding of send relay I23 to the negative terminalof the rectifier and the other from the positive terminal of the rectifier, conductor I29, break key I30, transmitting contacts I3I of subscribers teletypewriter I32, conductor I33, normal contacts of line-in key I34, conductor I35, regulating resistance I30, conductor I 31, through the respective left-hand and the right-hand operating windings, in series, of send relays I26 and I23, to the negativeterminal of the rectifier. Printer magnet I40 of subscribers teletypewriter I32 is also normally energized by current flowing from rectifier II4 over a circuit including conductor I4I, through the winding of printer magnet I40,conductor I42, varistor elements I43, retardation coil I44, marking, or left-hand, contact and armature of receive relay II9, retardation coil I45, to ground at the lower normal contacts of key Ill. The biasing-or lower, winding of receive relay IIB-is energized over conductor I46 and resistance I38, and serves to operate receive relay H9 to its spacing, or right-hand, position when line IOI is opened. Resistance I38 is of the adjustable type in' order that it may be adjusted to suit conditions of the line through the control unit to the switchboard at the teletypewriter exchange ofiice. A further description of the various elements in the circuit shown in Fig. 1 may be had by referring to United States Patent 2,143,000, supra. Power switch I08, upon being operated, connects ground at its outermost righthand contacts. to control conductor I02 of a circuit which extends over thecontact and innermost upper armature of each of line relays 201 and 206, in series, through the winding of line relay 205 to grounded battery. Relay 205, which is theline relay for station A, operates and (1) at its outermost upper armature and contact closes an operating circuit for relay 208 which operates to connect at its upper armature and contact and its inner'lower armature and contact busy signal conductor 2I8 to two parallel paths, one extending over conductor 2I9, middle lower armature and contact of relay 201, line conductor I05 and the other extending over conductor 220, middle lower armature and contact of relay 200,

line conductor I03, whereby should the subscriber v at either 'of stations B or C originate'a call while station A is using line 208, the subscriber so attempting such call would receive a busy signal; (2) at both its middleupper and its inner upper armature respectively opens two paths whereby the subscribers of either of stations B or C could not operate their respective station line relays I to start conductor 229 whereby relay 202 is operated to cause the busy signal to be transmitted by polarized relay 204 as will be hereinafter described. Therefore a line relay such as any one of relays 205, 200 and 201 causes, when operated, the subscribers stations other than that which caused the line relay to operate, to be locked out from any established connection to the line and prevents an operator at the teletypewriter exchange oflice from establishing two simultaneous connections to the alternating current relay 2 to transmit code ringing currents.

The marking current flowing from rectifier I I operates the calling-in circuit at the switchboard of the teletypewriter exchange office thereby causing the line lamp associated with line 208 to operate ina manner as described in United States Patent 2,143,000, supra.

Idle condition The line 200 at the control, or switching center, shown in Fig. 2, is, during an idle period, open to direct current inasmuch as it is connected in a circuit extending over the innermost lower armature and back, or normal, contact of each of line relays 205, 206 and 201, in series, to conductor 2I0 through the winding of alternating current relay 2I I, condenser 2I2 to ground, condenser 2I2 serving to block direct current and relay 204 which is of the polarized type and serves to transmit the busy signal is normally held on its marking, or lower, contact by current flowing in its biasing, or right-hand, winding.

Operator calls The operator at the teletypewriter exchange office connects a cord circuit to line 208 in the usual way and thereby causes a lamp located at the switchboard and associated with the selected line, to light. The operator then operates the ringing key associated with the selector cord circuit to transmit in code, that is, one signal to called station A, two signals to called station E, three signals to called station C. Ringing current over line 208 from the switchboard causes alternating current relay 2II to operate. Relay 2 I I, upon operating, causes supplementary ring relay 2I3 which is of the slow-to-release type to transmit ringing in unison with operators ringing key from source 2'0I at the switching center to subscribers stations A, B and C' simultaneously. The supplementary relay 2I'3' is inserted between relay 2 and each. of station line conducto rs I-0I, I03 and I05 to prevent line hits from causing false operation of the subscribers station ringers. In response to the one, two and fthree rings, the subscriber at the called station operates the power switch corresponding to. switch I08 at station A and the connection is established for communication purposes as hereinbefore described for a call from subscribers station A to the teletypewriter exchange ofiicei. When the operator at the teletypewriter exchange Qfiice observes the line lamp extinguished he knows that the established connection is prepared for transmission.

Busy signal The operation of any one of line relays 205-, 206 and 201 connects ground tothe winding oi relay 209 which operates, and at the same time grour'i'ded battery is connected to the start conductor 229 whereby relay 202 is operated in anobvious circuit. Relay 202, uponoperating, appliesgrounded battery on start conductor 22 9 to operate relay 20.3. Relay 203', upon operating,

opens the operating path of relay 202. Relay 202, being of the slow-to-release type, holds momentarily after its operating circuit is opened and then releases thereby removing grounded battery from the operating circuit of relay 203. Relay 203 which is also of the slow-to-release type holds momentarily after its operating circuit is opened and then releases thereby again closing the operating circuit of relay 202 which reoperates, and in turn, causes relay 203 to reoperate. Inasmuch as relays 202 and 203 are of the slowto-release type, about one half second release, ground will be applied to conductor 220 for. about one-half second and removed for about one-half second alternately. These cycles continue as long as a line relay, such as relay 205, 206 and 201, remains operated. The operation and release of relay 202 applies approximately sixty impulses per minute provided to transmit a busy signal.

The initial application of ground to conductor 23,0 discharges condenser 22I which is normally charged to a potential equivalent to that of battery 222 and the subsequent removal of ground from conductor 230 allows condenser 22I to recharge to its former potential. This charging current flows through the operating, or left, hand, winding of relay 204 and is of sufilcient volume and flows in such a direction as to momentarily overpower the biasing current in the right-hand winding of the relay.

In response to this charging current, relay 204 operates to its spacing, or upper, contact for a period of 20 milliseconds and at the rate of 'once per second. This intermittent 20 millisecond ground is appliedv to conductor 218, all armatures r station teletypewriter because it causes a sufficient amount of current to flow in the proper direction through the line, or upper, winding of receive relay I19 to overpower the biasing winding' of this receive relay for a period of time required to produce the letters signals. The

subscriber attempting to call, after notin this signal, restoresv the power switch,

Break signal The transmission of a break sign-a1 performs the same function as described in United States Patent 2,143,000, supra.

Subscriber recalls A: recall signal is transmitted by operating the recall key, such as key III; at station A. This momentarily opens the line circuit and produces a recall signal at the switchboard in the usual Since the power switch at the subscribers station remains operated, the associated line relay holds the connection through the control unit.

Subscriber disconnects The disconnect signalis transmitted by turning .off the pow-err switch which removes ground at; the outermost rightehzanel contacts of the switch. from the control conductor I02 for station A and deenergizes the rectifier such as that designated. lid for station A whereby current no longer flows in the transmission conductor. such Operator abandons a call.

No relays are operated other than ringing re lays 2I I and 2I3 which are directly under control of the ringingkey of the switchboard, no action takes place other thanthe operator ceases ringing if the subscriber does notanswer.

SYSTEM Y GENERAL DESCRIPTION As hereinbefore stated, system Y consists of Figs. 5, 6, 7 and 8 andi's designed for use with a party, or multistatiomtoll line extension circuit having two or more sections.

-Referring to Fig. 5, the equipment at station A is shown in schematic form and that at each "of stations B and C is shown in diagrammatic form. The equipment at each of stations B and C is identical with that at station A except that station A is equipped for both attended and unattended station service whereas stations B and C' are, equipped for attended station service only. Stations A, B and C are identical with stations A, B and C, respectively, employed in System X hereinbefore described, except that stations A, B and C have no control conductors such as conductor I02 at stationA, conductor I04 at station B and conductor I05 at station C, the transmitting and signaling conductor at each station of System Y serving for control purposes also.

Fig. 6 shows in schematic form the equipment at the control, or switching, center. Common to stations A, B and C isa source GM of continuous ringing current for calling by code any one of I the stations, for example, one ring for calling station A, two rings for calling station B and three rings for calling station C. At station A which, as hereinbefore stated, is equipped for unattended service, slow-to-operaterelay 540 is responsive to T one prolonged ringing signal as compared (with the one ringing signal of short duration used with station A arranged on an attended station basis. Also, common to stations A, B and C is a source of busy signals effected by relays 602, 603 and 604 for producing the letters signals at the teletypewriter of a subscriber at one of the stations, at which an attempt is made to call by turning on the power switch whenithe line to the switchboard at the teletypewriter exchange office is in use by a subscriber at another of the stations. spectively provided for stations A, B and C and supplementary relays 600, 609 and (H0 are respectively utilized when operated for controlling an Line relays 605, 606 and 60! are reestablished connection between the respectively associated subscribersstation and line 6] I. Relay 6I2 when operated by any one of the supplementary line relays B08, B00 and 0 I0, causes relay 6 I3 to operate. Relay 6 I 3, upon operating,serves to connect the sourceof busy signals over the normal contacts of any one or more of relays 600, 609 and IiI0 which are in normal condition at the time. I

The source GM of continuous ringing current is under the control of relays 5M, 0| 5, BIG and GI I. Relay I5 I 5 is of the alternating-current type and relay BI! is of the slow-to-release type. Polar relays 6I8 and [H9 are normally held in the positions shown, by mechanical biasing springs. All relays are normally released and polar relay B04 is normally held in its marking, or left-hand, position by,the biasing current flowing through its lower winding. Relays BIB and 6 I 9 are used, in conjunction with slow-to-release relay 620, when transmitting signals from any one of subscribers stations A, B and C'. A transmission signal from any one of the subscribers stations reverses the direction of line current for the marking and the spacing conditions and relay BIS is poled for operation when the subscribers station teletypewriter set is marking and relay [H8 is poled for operation when the subscribers station teletypewriter set is spacing. Therefore relay 620, which as hereinbefore stated, is slow to release, will remain in its operated position during the transmission to supply the holding ground for relay BIZ and the source of busy signal. Also relay 620, when operated, furnished holding battery for operating outthrough relay 6I4 whereby the subscriber's line is connected over conductors BI I and through to the multisection line repeater.

Fig. 7 shows a schematic circuit arrangement of the multisection line repeater conditioned for code ringing. In the idle condition all relays in the multisection line repeater are in their released positions as shown. At the left-hand side of Fig. 'Tpolar relay TM in the supervisory circuit and polar receive relay I02 in the repeater circuit are held to their markingor left-hand, positions by a holding current. in a circuit extending 'from grounded battery at the outer left-hand armature and back contact of relay I03, through their 'respective windings No. 2 in series. When a switch board operator rings after connecting a cord circuit to the toll line extension multistation circuit, the ringing current operates alternating-current relay I04 and, in turn, relay I05. Relay I05 upon operating, operates slow-to-release relay I06 and connects source I01 of 20 cycle ringing current over the operated contacts of relay 106 to con-- ductor 6II to operate alternating-current relay 6I5. Relay 6I5 operates to efiect the code ringing to the subscribers station as hereinbefore described. When the called subscriber answers by operating the power switch at the called stae tion, negative voltage is applied to a circuit extending over conductor BI I, through the winding of relay I00, to ground. Relay I08 operates. Relay I00 operates in a circuit traceable from ground at the marking, or left-hand, contact and armature of relay I0 I, conductor I32, through its winding, resistance I30, armature and contact of rela I00, resistances H0 and 'II I, and grounded battery H2. Relay I09, in turn causes the operation of relays I03 and H4. Slow-to-release relay .103, upon operating, (1) operate relay II 4; and

(2) removes at its armature and back contact,

the holding battery for relays ml and 102 and at its outer armature and front contact completes the apex for the line circuit extending through winding No. l of relay 'IOI, one path extending through resistance H5, retardation coil H6, resistance 'II'I, winding of relay T08, innermost upper armature and front contact of relay H4, to ground at the marking, or left-hand, contact and armature of polarized send relay "8; and

the other path extending through resistance H9 which is of equal value to resistance H5, front contact and outer left-hand armature of relay 103, windings No. 2, in series, of relays 102 and till, artificial line network 120, to ground. Relay H4, upon operating, (1) establishes an alternating-current circuit for holding alternating-ourrent relay 109 operated while relay 10! is following the signals received from conductor 5| I, the alternating-current path being traceable from grounded battery H2, resistances HI and H0, point E40, conductor 128, middle upper armature of relay H4, condenser 135, resistances I34 and 130, through the winding of relay I09, conductors BI and 132, marking, or left-hand, contact and armature of relay l0] to ground. The point 140 is effectively connected to ground and conductotl 128, alternately, and the condenser 135 is alternately charged and discharged during the time that signals are being received from conductor 6; (2) transfers toll line conductor 133 from ring-up relay 104 to conductor 125 which extends through the line repeater including receive relay I21 (3) transfers conductor 136 from the calling ground connection 'l4l to conductor 13? which extends to the armature of send relay H8; and (4) establishes a biasing current for winding No. 3 of relay 10! so that the relay armature remains on the contact to which it was actuated by the current in winding No. 1. As soon as conductor 125 is connected to conductor 133, marking negative battery from relay 124 flows into the toll line terminating equipment represented by box 85! at the operators switchboard, to extinguish the lamp associated with the selected cord circuit, in the same manner as when the subscriber answers the call in System X as hereinbefore described.

Receive relay 102 serves to repeat the communication signals incoming over conductor 6| I, through the upper windings, in series, of send relay H8, break relays 122 and 723 and send relay 124 whereby the latter relay repeats the signals over conductors 125 and 133 to the repeater in the toll line terminating equipment 80I at the central teletypewriter exchange office, operators cord circuit 804 to the operator's teletypewriter set. During communication relays 109, 103 and H4 function to hold the communication circuit closed.

. METHOD or OPERATION Operator calls Assuming that a connection is desired with a subscribers teletypewriter at station A, B or C, the operator connects one of several cord circuits, such as cord circuit 804, to a jack, such as jack 805, and then operates a ringing key (not shown) associated with cord circuit 804, say one operation of ringing key for station A, two oper-' ations for station B and three operations for station C. Station A which has assigned to it one interval of ringing current is shown as being arranged for unattended as well as attended station service because of it having one ring signal only. For unattended station service the one ring signal will be for a prolonged interval sufficient to operate slow-to-operate relay 549. Stations B and C are arranged for attended station service only and, therefore, have no relays corresponding to relays 548, 549 and 550, or motorstop contacts corresponding to those designated 55!. toll line terminating equipment 80!, line conductor 133, outermost upper armature and back contact of relay H4, through the winding of alternating-current relay 104, condenser 126 to ground. Relay 104 responds to the ringing cur- This ringing current is transmitted through rent and sets up a similar operation of relay I05. Relay responds to vibratory operation of relay I04 and at its inner armature and contact closes an operating circuit for relay 106 which operates but being of the slow-to-release type remains operated during each of the one, two or three intervals of ringing current transmitted from the operator's switchboard at the teletypewriter exchange ofiice. Also relay 105, upon operating, closes at its upper armature and front contact a source [01 of 20-cycle continuous ringing current to line conductor 6| l.

The ringing current incoming at the switching, or control, center over conductor 6H flows in a circuit traceable over the outer upper aimature and contact of relay 6I4, through the windin of alternating-current relay 6l5, condenser 02l, to ground. Relay 6|5 responds to the ringing current incoming over conductor 6H and closes an operating circuit for relay 6H5 which operates in accordance with the vibratory action of relay 6I5. Relay GIB upon operating, closes an operating circuit for relay 0|! which operates and being of the slow-to-release type, remains operated during the time that ringing current is applied to the subscriber station lines for operating the subscriber set ringers, such as ringer 50! at station A. Ground connections are furnished at the back contacts of relay BIB for discharging the condenser which is in series with the ringer, between applications of ringing cur rent.

Should the call be to station A, one normal operation of the ringing key (not shown) at the teletypewri-ter exchange oflice switchboard would cause one short interval of ringing current to be transmitted over each of conductors 622, 623 and 624 to respectively operate the ringers at stations A, B and C. Inasmuch as it is hereinbefore assumed that station A is being called, the sub scriber at station A upon identifying the single interval of ringing current responds by operating power switches 508. The subscribers at stations 13' and C upon hearing the single interval of ringing current will ignore the call. Power switch 508, upon being operated, completes a path from grounded alternating-current source 508, conductor 5|0. right-hand contacts of the switch, conductor 5| I, through the winding of relay 5l2 ,to ground. A path parallel to that extending over conductor 5| l extends over conductor 513 through rectifier 5M, and printer motor 5|5 in parallel. Rectifier 5! is energized and printer motor 5|5 starts operating. Relay 5|2, upon operating, closes a circuit from line conductor 622, recall key 5 l 6, test-out key 511, armature and front contact of relay 5l2, resistance 518, through the upper winding of receive relay 5I9, resistance 520, retardation coil 5I2, resistance 522, armature and marking, or lower, contact of send relay 523, retardation coil 524, negative terminal to the positive terminal of rectifier 5M, retardation coil 525, marking, or upper, contact of send relay 526, retardation coil 52! to ground 528.. The energized rectifier 5l4 supplies a source of potential difference between its terminals and thus to the circuit including ground 528 and line conductor 622. Rectifier 5 l4, upon becoming energized, also causes current to flow in two parallel paths, one extending from the positive terminal of the rectifier, through the right-hand biasing winding of relay 526 and the left-hand biasing winding of relay 523, to the negative terminal of the rectifier, and the other path extending from the positive terminal of the rectifier, conductor 529,

break key 530, transmitting contact 53I of subscribers teletypewrlter set 532, conductor 533, normal contacts of line-in key 534, conductor 535, regulating resistance 536, conductor 531, through the left-hand and the right-hand operatingwindings, in series, of send relays 526 and 523, to the negative terminal of the rectifier. Printer magnet 540 of subscribers teletypewriter set 532 is also normally energized by current flowing from rectifier I4, over conductor 54I, through the winding of the printer magnet, conductor 542, varistor elements 543, retardation coil 544, marking, or left-hand, contact and armature of receive relay 5 I9, retardation coil 545, to ground at the lower normal contact of key 5II. The biasing, or lower, winding or receive relay 5I9 is energized in a circuit extending over conductor 546 and variable resistance 552 and serves to operate relay 5I9 to its spacing, or right-hand, position when spacing polarity is added to line 622. A further description of the functions of the various elements in the circuits shown in Fig. 5 may behad by referring to United States Patent 2,143,000

supra. u l

I When the called subscriber at station A answers by turning on the power switch 508, marking, or negative, voltage isapplied to line conductor 622 which extends in a circuit traceable over the outermost upper armature and back contact of relay 6I'I, upper armature and back contactof relay 608, through the lower winding of line relay 605, back contact and inner lower armature of line relay 606, outer lower armature and back contact of line relay 601, back contact and middle lower armature of cut-through relay 6I4 to ground. Relay 605 operates, and (l) at itsouter upper armature closes an operating circuit for asupplementary line relay 608; (2) at its inner lower armature opens the operating circuit for line relay 606; (3) at its outer lower armature opens the operating circuit for line relay 601; and (4) at its inner upper armature prepares a locking circuit for itself. Relay 605, upon operating, prevents the other line relays 606 and 60! from operating during thetime that a connection is established with subscriber station A. Relay 608 operates and thereby (l) closes at its lower armature a circuit extending from grounded battery, lower armature of relay 608, through the winding of holding relay 6I2, normal contacts of relay 620, conductors 625 and 626, make-before-breakicontacts of relay 6I4 to ground, and (2) extends conductor 622 at its upper armature and front contact, to conductors 625 and 626 to ground at the make-before-break contacts of relay 6M. Relay 6I2 operates and 1) closes at its upper armature an operating circuit for relay 602 (2) completes at its inner lower armature the locking circuit for relay 605; and (3) closes at its outer lower armature the operating circuit for relay 6I3. The condition of line conductor 622 is at this time marking and in such condition, as hereinbefore stated, causes relay 6 I9 to operate in a circuit traceable over conductor 621, through the winding of relay 6 I 9, resistance 628, conductor 626, to ground at the make-before-break contacts of relay 6I4. Relay 6I9, upon operating, closes the operating circuit for relay 620. Relay 5 620, upon operating, closes the operating circuit for cut-through relay 6| 4 which operates and cuts .through the conductor 626 to the toll line ex- 'A has answered.

contact of relay I06, through the No. l'windings, in series, of relays I0! and I02, resistance H5, retardation coil H6, resistance III, through the winding of relay I08 to ground at the innermost upper armature and back contact of relay II 4. Relay I08 operates and closes acircuit extending from grounded battery H2, resistances III and H0, conductors I21 and I28, armature and contact of relay I08, conductor 12!), resistancel30, through the winding of holding relay I09, conductors I3I and I32, marking or left-hand contact and armature of relay ml to ground. Relay. I09, upon operating, closes anoperating circuit for relay I03. Relay I03, upon operating, operates relay H4 and removes grounded battery from the biasing winding of receive relay I02 and relay IOI. Also relay I03, upon operating, completes the other part of the apex. circuit which part extends over resistance H9, front contact and outer left armature of relay 103, through the No. 2 biasing windings of relays I02 and IIII, in series, to grounded artificial line network I20. Relay H4, upon operating, establishes the alterhating-current path for holding relay I09 operates while relay TM is following the signals transmitted from subscribers station A, the circuit changing in accordance with the operation o1 relay IOI; When relay TM is in its marking condition, as shown, the alternating current circuit, as hereinbefore stated, is traceable from ground at the armature and marking contact of relay I0 I conductor I32 and I3I, through the winding of relay I09, resistances I30 and I34, condenser I35, contact and middle armature of relay H4, conductors I28 and 121, resistances H0 and II I, to grounded battery I I 2. With relay IOI in its spacing position, the alternating-current circuit'is shunted to ground at the spacing contact. Also relay H4, upon operating, transfers the toll line extension circuit conductor'l33 from the winding ofring relay I04 to the transmission conductor I25 which extends through the upper winding of receive relay I2I to grounded negative battery at the marking, 01' left-hand, contact of sand relay I24. Also,relay H4, upon operating, transfers transmission conductor I36 from ground connection I4I to transmission conductor 131 which extends to ground at the marking contact of send relay H8. As soon as grounded negative battery at the marking contact of relay I24 is connected over conductor I25, to toll line extension circuit conductor l33, the cord lamp at the switchboard becomes extinguished indicating to the operator that the subscriber at station Busy line indication The operation of the letters signal circuit depends, as. hereinbefore described under System X, on the alternate operation of two sloW-to-release relays, such ,as relays 602 and 603, whereby the charging current in the upper winding of a polarized relay, such as relay 604, is of suflicient volume and in the direction to momentarily overpower the biasing, or lower, winding of relay 604 and to operate the armature of relay 604 toits spacing contact. This ground is applied for about 20 milliseconds to conductor 629 at the rateof once per second. With relay BIS operated, this intermittent 20 milliseconds ground isappliedto each of the three lower ar natures of relay {H3 and their respectively associated conductors 6.30, 63I- and 6 32. In the event that a subscriberj at any station attempts to originate a call when jthe line to the switchboard is in use by a subscriber at one of the other stations, the intermittent timed pulses of current will be transmitted over the back contact and upper armature of supplementary line relay, such as lin relay 603 for station A, relay 609 for station B and're-lay 6I0 for station C, to the conductor extending to the station whereat such call is attempted. The intermittent pulses produce letters signals at the station teletypewriter whereat the second call is attempted. Break signals The break signals perform the same functions as in the subscribers station set described for Fig. 1 of United States Patent 2,143,000, supra.

Subscriber recalls The subscriber momentarily operates recall key, such as key 5I6, at subscribers station A, which removes the transmitting negative potential from the station line circuit and supplies ground toward the control, or switching, center. Since the normal condition at the marking contact of send relay in the switchboard terminating repeater circuit (send relay is designated '65 in Fig. 2 of United States Patent 2,143,000, supra) is grounded, the voltage drop across resistor 633 falls to zero and neither relay 6I9 or M8 is operated. Hence relays 620 and GM release. The release of relay 620 connects the winding of relay 6I2 over the normal contacts of relay 620 to transmission line conductor 625 and relay 6I2 remains operated in the line circuit extending to ground at the subscriber station A. Since relay 6|! remains D- erated, the line connection previously established by the operation of the associated line relays, such as relays 605 and 608 for the line to station A, remains intact. The release of relay 6M terminates the switchboard line conductor 6| I in the winding of ringing relay 6I5. With the substitution of ground at the subscriber station for the negative potential, and the application of an open circuit (alternating-current relay 6I5 and condenser 62I) to one end of the switchboard line conductor 6 and with ground at the marking contact of send relay H8, connected to the opposite end of conductor 6, relay I08 releases. The release of relay I08 effects the release of a1- ternatin -current relay I09, which, in turn, causes the release of relay I03 and H4 and opens line conductor 133 to the switchboard to effect the operation of the cord lamp. The above functions are completed while the power switch at the subscribers station is in its off position. When the power switch is again operated to its on position, relays so released are reoperated. In response to each momentary release operation of the power switch at the power station, the cord lamp at the switchboard is extinguished and therefore in response to a recall signal the cord lamp is caused to flash a recall signal.

Subscriber disconnects The subscriber turns oil the power switch such 7 as switch 508 at station A which removes the source of power 509 from the station equipment. All operated elements release and all energized devices deenergize thereby placing an open condition on station A transmission conductor, such as at relay I2 for conductor 622. This differs from the condition when a recall signal is transmitted in which case ground is connected to conductor 622. In response to the disconnect signal, relay H2 is released and in turn the line relays, such as relays 605 and 608 for station A, release.

Also relays 6 I 8 and '6 I 9 are released when line con ductor 622 is opened and thereby cause relay 620 to release. -Relay '6I2, upon releasing, releases relays 6I3, 602 and 603. At the multisection line repeater relays I08, I09, I03 and H4 release in response to the release of relay 6M and a permanent open signal is thereby transmitted to the switchboard to light the cord lamp.

Subscriber calls Should the subscriber at station A originate a call, as for example by turning on power switch 508, negative potential of rectifier SM is applied to station transmission conductor 622 to operate relay'605 as hereinbefore described when the subscriber at station A was assumed to have answered a call originated by the operator at the teletypewriter exchange oflice. Relays 608, 612, GM, 6I9, 620,.6I3, 602, 603 and 604 operate accordingly. At the multistation line repeater relays I08, I09, I03 and H4 operate as hereinbefore described. The negative potential of the rectifier 5M applied to the line circuit causes current to flow over the line circuit and thereby causes repeater MI and. the toll line extension terminating equipment 802 to operate in a manner described in United States Patent 2,143,000, supra, to light the call lamp (not shown) at the operators switchboard. The operator responds and the operations completed by the operator are the same as here inbefore described.

Operator abandons call Should the operator desire to abandon the call while transmitting code ringing signals, it would only be necessary to' cease ringing. No relays in either the multisection line repeater or the control circuits are in a locked position during the ringing period, all operated relays will be in the toll line terminating circuit 802 and these will release when the operator removes the cord circuit from the jack of the called line.

COMBINED SYSTEMS It is understood that Figs. 1 and 2 may be combined with Figs. '7 and 8 to make another system and that Figs. 5 and 6 may be combined with Fig. 3 to constitute still other systems. The multisection line employed in System Y is operated half-duplex using polar sending-differential receiving operation over each section of the line, that is, each section is operated half-duplex with polar signals being transmitted from one end of each section and signals with a current difierence being transmitted from the other end of each section. The section shown extending between Figs. 6 and 7 receives from one end polar signals from the armature and contacts of each of send relays 523 and 526 and from the other end medium current and high current signals transmitted from the respective contacts of send relay H8. Similarly, the section shown extending between Figs. 7 and 8 receives from one end polar signals from the armature of send relay I24 and from the other end medium current and high current signals transmitted from the contacts, respectively, of relay 65 shown in Fig. 2 of United States Patent 2,143,000, supra.

What is claimed is:

l. A telegraph system comprising a main telegraphic trunk transmission circuit, a switching center at which said circuit terminates, a plurality of telegraphic stations equipped with transmission and reception apparatus for permuta tion code, a local circuit connecting each of said all other of said stations, said conditioning means comprising instrumentalities at said switching center for supplying permutation code signals to all said other circuits and said conditioning means having other means, when operated, to supply said code signals to the permutation code reception apparatus associated with any other starting element upon operation of said other starting element.

2. A telegraph system comprising a main tel egraphic trunk transmission circuit, a switching center at which said circuit terminates, a plurality of telegraphic stations, each having transmission and reception apparatus for permutation code, a local circuit comprising two paths connecting each of said stations tothe switching center, each of said stations having a starting element, individual electromagnetic means at 7 said switching center responsive, over one of said paths, to the operation of said startingelement, means at .said switching center operable by the operation of any one of said starting elements to connect the station of said starting element over the other ofsaidpaths to said trunk circuit at said switching center, and means also controlled -by operation of said element to condition all other of said stations, said condition ing means comprising instrumentalities at said switching center fcrlsupplying permutation code signals over' said other path of said other circult, and said conditioning means having other means, when operated, to supply said code signals to the permutation code reception apparatus associated with any other starting element upon operation of said other starting element. 3. A telegraphic system comprising a. main telegraphic trunk transmission circuit, a switching center at which said circuit terminates, a plurality of telegraphic stations each having transmission and reception apparatus for permutation code, a local circuit comprising a single path connecting each of said stations to the switching center, each of said stations having a starting element, individual electromagnetic means at the switching center responsive over said path to the operation of said starting element, means at said switching center operable by the operation of any one of said starting elements to connectthe station of said element over said path to said trunk circuit at said switching center, and means also controlled by the operation of said element to condition all other of said stations, said conditioning means comprising instrumentalities at said switching center for supplying permutation code signals over said path. and said conditioning means having other means, when operated, to supply said code signals to the permutation code reception apparatus associated with any other starting element upon operation of said other starting element.

4. A telegraphic system comprising a main telegraphic trunk transmission circuit having at one end a source of code ringing current signals and at each end a source of permutation code signals, a switching center at which said circuit terminates, a plurality of telegraphic stations equipped with transmission and reception apparatus for permutation code, a local circuit connecting each of said stationsto the switching center, each of said stations having a starting element, means at said switching center operable by operation of any one of said starting elements to connect the station of said operated element to said trunk circuit at said switching center, means also controlled by operation of said element to condition all other of said stations, said conditioning means comprising instrumentalities at said switching center for supplying permutation code signals to all said other local circuits and said conditioning means having other means, when operated, to supply said code signals to the permutation code reception apparatus associated with any other starting element upon operation of said other starting element, and one of said stations com prising means responsive to a prolonged operae tive connection of said code ringing current source to said trunk circuit for starting the transmission and reception apparatus at said one station inde pendently of said starting element at saidone station. l

5. A telegraphic system comprising a main telegraphic trunk transmission circuit, a sourceoi code ringing signals connectable to one end of said trunk circuit, a switching center at which the other end of said trunk circuit terminates, electromagnetic devices at saidswitching center, a plurality of telegraphic stations equipped with transmission and reception apparatus for ermutation code, a local circuit connecting each of said stations to said switching center, each of said stations having a starting element, said switching center comprising a plurality of paths for connecting said'trunk circuit with any one of said local circuits, certain of said electromagnetic devices included in one of said paths and responsive to code ringing signalsin one or more intervals from said source for causing said intervals of code ringing signals to be repeated over each of said local circuits, one of said local circuits including means arranged to respond to the code ringing signals in an interval of relatively long duration to automatically operate the transmission and reception apparatus for permutation code independently of said starting element, and other of said electromagnetic devices included in said other path and responsive to signals from any one of said transmission and reception apparatus for connecting the local circuit associated with said one apparatus to said trunk circuit for communication purposes. v

6. A telegraphic system comprising a single wire telegraphic half-duplex operated trunk transmission circuit using polar sending-difierential receiving operation, a switching center at which said trunk circuit terminates, a plurality of telegraphic stations equipped with transmission and reception apparatus for permutation code, a local circuit of a plurality of conductors connecting each of said stations to said switchin center, one of said conductors arranged to transmit message signals and the other arranged for controlling the connection established with said trunk circuit through said switching center, each of said stations having a starting element, means at said switching center operable by operation of any one of said starting elements to connect the station of said element to said trunk circuit at said switching center, and means also controlled by operation of said element to condition all other of said stations to prevent said other stations from being connected to said trunk circuit when engaged in the established connection with the station of said starting element, said conditioning means comprising instrumentalities at said switching center for supplying permutation code signals to all said other circuits, and arranged, when operated, to supply said permutation code signals to the permutation code reception apparatus associated with any other starting element upon operation of said other starting element.

'7. A telegraphic system comprising a multisection single wire telegraphic half-duplex operated trunk transmission circuit using polar sendingdifferential receiving operation, a switching center at which said trunk circuit terminates, a plurality of telegraphicstations, a local circuit of a single-wire conductor type connecting each oi said stations to said switching center, said singlewire conductor being arranged to transmit message signals and to control the connection established with said trunk circuit through said switching center, each of said stations having a starting element, means at said switching center operable by operation of any one of said starting elements to connect the station of said element to said trunk circuit at said switching center, and means controlled by operation of said elements to condition all other of said stations to prevent said other stations from being connected to said trunk circuit when engaged in an established connection with the station of said starting element. a v

8. A telegraphic system comprising a multisection single-Wire telegraphic half-duplex operated trunk transmission circuit using polar sendingdifierential receiving operation, a switching center at which said trunk circuit terminates, a plu rality of telegraphic stations, a local circuit of a plurality of conductors connecting each of said stations tosaid switching center, one of said conductors being arranged to transmit message signals and the other arranged for controlling the connection established with said trunk circuit through said switching center, each of said stations having a starting element, means at said switching center operable by operation of any one of said starting elements to connect the station of said element to said trunk circuit at said switching center and means also controlled by operation of said element to condition all other of said stations to prevent said other stations from being connected to said trunk circuit. when engaged in an established connection with the station of saidstarting element.

9. A telegraphic system comprising a main telegraphic trunk transmission circuit, a switching center at which one end of said trunk terminates, a plurality of lines from said switching center to individual outlying stations including individual ringers, a main station at the OpPQsite end of said trunk, means including means'operable at any one of said outlying stations to extend its individual line (during an idle condition of said trunk) to said main ofiice, disconnect means including means operable at said station to discontinue said extension, means including operable means at; said mainoflice to selectively ring one of said outlying stations as a signal to establish such an extended connection, and means opera: tive incident to selective ringing of one of said stations when unattended to cause equipment ,at said station to establish the desired extension for the purpose of sending a message from said main station to and recording it at said one station, and means operative under control of said main station to discontinue such extension of the line of said one station.

LELAND A. Q RDNER. KENNETH .RICHARDS.

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