US2002985A - Automatic printing telegraph exchange system - Google Patents

Description

y 1935. e. A. LOCKE 2,002,985

AUTOMATIC PRINTING TELEGRAPH EXCHANGE SYSTEM Filed Dec. 9, 1952 3 Sheets-Sheet 1 Q Q k Q rs r L g I i m t fi g EL l/Vl/EN7OR GALOCIQ-T May 28, 1935. G. A. LOCKE AUTOMATIC PRINTING .TELEGRAPH EXCHANGE SYSTEM 3 Sheets-Sheet 2 MR NW N Gt I IIHIILIT INVENTUR V G. A. LOCKE 0 7 AT7URNEV EI-I IM' y 8, 1935. G. A. LOCKE 2,002,985

AUTOMATIC E RINTING TELEGRAPH EXCHANGE SYSTEM I Filed Dec. 9, 1952 3 Sheets-Shae; 3

Patented May 28, 1935 UNITED STATES PATENT o cE; .4

AUTOMATIC PRINTING TELEGRAPH I EXCHANGE'SYSTEM George A. Locke, Glenwqod, N. 3L,w assignor to Bell Telephone Laboratories, Incorporated, New York, N; Y.,'a corporation'of New York Application Dec-embers, 1932, Serial No; 646,368 '9 Claims. (01. ire-T2) the receiving printers to two or more of' the sending stations. 7 V

Heret'ofore, printing telegraph systems wherein a group of receiving printers'were so arranged that in response to the operation of a key at a sending station, the first idle receiving printer of the group may beselected for'r'eceiving the transmitted message, the communication circult extending from the sending station to the receiving station being normally closed. Should allthe receiving printersof a group bej'found busy by the sending station, the operator at the sending station will receive a signal indicating that she should restore the key and try again.-

According to the present invention, a plurality of normally deenergized communication lines re-# spectively connect a plurality of sending stations to a central oifice' whereat incoming calls are automatically distributed to a group of idle printers, the first idle'printer of the group being selected by each incoming call. Should all the-printers be busy at the time a call is received at the central ofice, a busy lamp at an operators position in the central office lights and the operator in response to this light connects an auxiliary teletypewriter to the calling line whereby the message may be received at the central oflice. The auxiliary printer at the central office is further arranged to transmit messages to the printer at any oneof the sending stations and to the printers at two or more sending stations simultaneously for broadcasting purposes.

Among the features disclosed herein are the iollcwing 1. The provision of a key at a sending oroutto indicate "to-the operator that all the main printer's at the central oflice are busy and the auxiliary printer being adapted to be connected by the operator to 'the calling line associated with the lighted lampyito pick up, the message. .7 3. The 'system'istso arranged that the central ofiice'may oziginate a call to a line 'on a broad- I cast to'a group orall theliries simultaneously.

' Other objects and featureswill appear in the following detailed description taken in conjuncs tion with the following drawings. v

Re'ferringjto the drawings? 1;

V Fig. 1 shows a schematic layout of a sending, orioutlying station; It also shows a; second sending station represented diagrammatically by a block;

Fig: 2 schematicallyrshows a'por-tion' of the equipment attire" central' -ofiice. The equipment shown the'upper and middle-parts of the drawings represents" that associated with the calling station shown somewhattin detail in Fig. l.j The equipment shown in the lower part,that is, within the block, is usedwhen transmitting from the central ofiice to the'second outlying station shown inFigglyand l. Fig. 3 illustrates schematically the arrange ment of the maimprinters, the auxiliary printer and the equipment usedbythe operator at the eithenindividually or' f0r broadcast purposes.

Apparatus at an outlying station Referring to Fig. 'l which shows the subscribers loop circuit 'at'gan :outlying station 'A,'th'e requipinent shown therein comprises aprinting telegraph' sendingandreceiving unit llll. Unit l0! comprises 'agprinter magnet 12', a set of sending contacts I03, asuitable motor i0 1, equipped with 40 a pair of motor control contacts 105 which will openby mechanical means Whena. motor stop signal is sent, and a break key [05. Themotor the circuit hereindescribed is driven by alternating current. External of the printer telegraph set or unitlare the non-locking call key I01, an alternating current power supply 108, a rectifier [09, power connecting relays H0 and H La puls-v ing relay H2 and a loop. connecting relay H3. Relays I I6 and l I2 are of the polar type. Another outlying station E is also shown but in diagrammatic form.

Apparatus at the central office Figs, 2 and 3' constitute equipment at the individual to the loop circuit of station A. There is provided at the central oflice similar equipment for each of the other outlying stations Relays 204 and 205 are associated 'withthe equip ment necessary for the central office operator to transmit messages to outlying station E. A key, not shown and corresponding to key 203, is provided to complete a connection fromthe central oflice to station B. A broadcast non-locking key 201 is-also provided whereby the-operator'may transmit messages simultaneously to all the outlying stations.

In Fig.3 four main receiving only printers are schematically represented within blocks 30 I, 302, 303 and 304,-and it is understood that the system is not limited to the number of printers shown. Printer 304 is under control of polar relay 305; Relays 306 and 301 serve to make printer 304, whene gaged by an outlying station, busy to 'allsubsequent calls from other outlying stations while it remains engaged. Each of the remaining printers 30I, 302 and 303 have associated therewith relays corresponding to relays 305, 306 and 301. Theseprinters are respectively associated with the contacts on switch bank I. When all the main printers are busy, relay 308 automatically operates to indicate the condition and the operator inserts plug 309 of a cord circuit at the toll switchboard. into spring jack, 3I0 which is associated with the lamp 3 corresponding to, say, station A shown'in the drawings, whereby the auxiliary printer 3I2 comprising a sending and receiving ,unit is connected to the line extending to station A to receive the message. Should the operator desire to originate a call to one'or. more outlying stations simultaneously, the plug 309owould be inserted in spring jack 3 I 3 and thekey or keys, corresponding to keys 203. for station A and associated with the desired station or stations, would be operated, for connecting the, auxiliary printer 3I2 to the line or lines extending to the desiredstation or stations. Should it be desired to establish a general broadcast circuit, that is, one including all stations, the printer 3I2 wouldbe connected by means of plug 309 to spring jack'x3l3 and key 201 would be: operated instead of the key corresponding to key'203 and. individual to each station of the system.

Operation of the system Having briefly discussedthe various circuit elements involved in'gestablishing a connection,

between a sending and a receiving'station, the manner in which the connection is established will now be described in detail; Referring to the drawings, under normal, conditions, a deenergized line circuit may be traced from ground I I1, break contact and armature of relay I I3, through thewinding of relayI I 0, sending contacts I03, break key I06, through the upper winding of relay II2, ring conductor II6, through the lower winding of relay 208, break contact of key 203, outer upper armature and break contact of relay and causes it;to release.

209, upper break contact of relay 2I0, make-before-break contact of relay 2I I, to ground 2| 2.

For the purpose of illustration, it is assemed that the subscriber at station A desires to estab lish a connection to the first idle main printer at the central ofiice. Call key I01 is operated Wherebyground II! is connected to the tip conductor. I I5, through the upper winding of relay 20B, outer lower armature and break contact of relay 222, upper make-before-break contact of relayZII to grounded positive battery 2I3. Re lay' 208 operates and connects ground to the circuit extending through the winding of relay 2I4 to: grounded battery. Relay 2I4, which is of the slow-release type, operates and applies ground at its inner armature and contact to a circuit extending over the contact and lower outer armature of relay 2I0, armature and contact of stepping magnet 2I5 to grounded positive battery 2H3. A relay 2I1 is normally held ope"- ated by the circuit extending from grounded battery 2 I6,through the right-hand winding of the relay to ground. The application of ground at the inner right-hand armature of relay 2I4 short-circuits the normally closed circuit extending through the right-hand winding of relay 2I1, The release of relay 2| 1 will cause the stepping magnet 2I5 to operate and thereby move the wipers on banks I, II and III-on thevstepper switch S one step to their respective'second contacts. The energization of the stepping magnet opens the contact at its armature, to remove the short circuit from the right-hand winding of relay'2I1 causing relay 2!! to reoperate. The stepping magnet, therefore, is deenergized again closing the contact at its armature. The closing of the contact of the armature of. the stepping magnet again shortcircuits the right-hand winding of relay 2I1 which releases; The release of relay 2I1 causes the stepping magnet to reoperate thereby causing the wipers of banks I, II and III to move to their respective third contacts. The wipers will continue to step around their respective banks until the wiper of bank II arrives on the contact to which grounded battery is found on the break contact of a relay corresponding to relay 301. Assuming that receiving printers 30L 302 and 303 are busy, relays 3M, 3I5 and 3I6 will be operated and grounded battery will be found on the fifthcontact of bank'II because receiving printer 304 is the first idle printer and relay 301 is deenergized. Under this condition a circuit may be traced from grounded positive battery at the make-before-break contact of relay 301, conductor 3I1, fifth contact of bank II, and its associated wiper, through the upper winding of relay, 2I I,1through the left-hand winding of relay 2I1, to ground at the outer armature of relay 2I4. This circuit Will operate relay 2I1 and hold it operated preventing any further stepping of the stepper switch wipers. The circuit just traced will operate relay 2I I, thereby'removing ground at the lower make-before-break contact of relay 2 II and applying grounded positive battery through the ring conductor I I6 in a circuit traceable from battery 3I8, left-hand armature and contact of relay 308, conductor 3I9, lower inner armature and contact of relay 2I I, make-beforebreak contact of relay 2I0, outer upper armature and break contact of relay 209, normally closed contact of key 203, through the lower winding of relay 208, conductorl I6, through the upper winding of relay II 2, closed contact of key I06. transmitting contacts I03, through the winding of relay I: l armature and. break con tact ofirelay: H13, tov ground: H111 Relays; tilt and Mlof station A operate. Relay 01in operating, closes a circuit extending from- .one side. of the alternating current power supply=l00,' through the windingzotrelay: ljtl, armatureand contact: of relay use, backi 'toI the opposite. side of the power supply. Relay iiH operates. and at its.let-- hand contact. and armature closes. a locking circuit for itself and an'operating: circuit for the motor 1 04 Relay I H. closes at' its, right-hand. armature and contact a circuit for energizing the. rectifier M9; the rectified tcurrentserving-to. op;-

.erate relay :3, energizes. the lower winding of relay-H2, and: operates'the printer magnet we when the armature of relay l ltisrin engagement. with its associated make. contact. The current flowing through the loweriwinding' of relay latii's considerably 'less and opposite. than that;.flow

ing through the upper winding and therefore when the line circuit is open and; nocurrent' is flowingthrough the upper winding,v the current; inthe lower winding will hold the armature of.

relay. |ll2 in the position shown. If thecall hey:v

I201 has. not already been released, the starting; of motor 1:04? at station. A .willcbe a signal tor the subscriber to release key. 101.. When key t1; isreleased: and relay H3; is operated'theloop. circui-t will be closed? from groundedpositivebat.-

-' tery 311118, left-handarmature and contact of. relay 308,.conductor '3;l-8=,.-lower -inner armature and contact. 05'- relay 2d l1, make-before-break content. of relay 21:0, upper outer armature: and, break: contact of relay 2G9,gnormally closed contact o key: 203,1 throughlthelowerwinxiing; of relay: 208,,

ring conductor. H6 through the upperwinding; of relay"! t2, 'c1osed':contact; ofikey ME, trans-- mitting contacts E03, through; the winding." ofrelay: H0; armature and make contact. of. relay H3, normally closed contacts of. keyJ-W'Lltip. con,- ductor 5, through the upper winding of relay 20.8, lower outer: armature; and break contact of relay 222, make; contact-and, upper armature: ofi relay 2fl|,.Wlp8II'-0f. bank I" on its. fifth-contact,

1 conductor;:21l:8',, through the leftrhandf winding F 208:rele ases causing the release of relay 2.14., The;

release of, relay 208 applies ground to a. circuit extending; over conductor 219, through the wind ingot relay 2H1, make contact and lowerouter armature of relay 2! ltel-grounded battery. The.

.-.; l ase or relay 2M tends to release relays 2H andZ Ht, butboth relays are held operated. Relay 2H. is held; operated in a circuit. extending from.

grounded battery, through its lower winding,

The motor control contacts of the printer 304.

were closed when the circuit was closed through the. wiper of bank Iv arriving on its fifth ontact at. the. time relay 2H] operated. .At thatitime a circuit was-closed extending from grounded positive battery, through the left-hand winding of polar relay 385, conductor .218, fifth contact and wiper of bank 'I, upper armature and make contact. of relay ZI I, break contact. andlower relay 301.

outerarmatureaof relay 222,. through the upper winding of relay 208, tip conductor l tig. operated contact. of key I01- to ground Ml. Polar relay 3.05.: is electrically'biased to spacing. and when. no. line current .is connected to. it, its armature lies in the position shown. When the line current.

flows. through the left-hand winding of relay 305:, it is considerablygreater than thebiasing current flowing through the right-hand Winding and. therefore, causes the relay armature to en-' gage its contacttoiclose a circuit extending from ground at the relay armature over two parallel paths, one extending through the winding oi the:

printer magnet 32! to groundedbattery and. the other. throughjthe: right-hand winding of relay 39.6;to. grounded. negative: battery. Magnet 32k and relay 306 operate. Relay 30am operating: closes at its right-hand armature an operatingv circuit for the motor control relay'322 which operates to start the motor of printer 30.41. The starting of the printer motor closes the motorcontrol contacts. 320. The closing of the motor.

control contacts closes two: oblvious. circuits, one for locking relay 30S and the other for operating: The operation. of relay 30%! makes printer 3M busy to. subsequent calls. As hereinbefore stated, the closing of the motor controi contacts holds relay 2-l-Ii. operated over the. fifth contacts of switch bank Relay 2H! operates in the circuit hereinbefore. described and closes at its. lower innerarmature: and contacts. an operating circuit fprbusy lamp. 3H indicating that the printer! isIeng-aged; At the upper armature and make contact of relay 21B.- grounded negativev battery 224 is. con nected to the. ring. conductor lilfi. of theline oircuit in place of the grounded positive battery 3 E8,

puts the line circuit in its position for operation. When grounded negative battery 221 isconnected to. the line circuit "by the. operation of relay 2%!20; relay 208' again operates thereby'opening the operating. circuitlfor" relay 210;. Relay 210,5

however, is maintained man operated." position by alocking-zcircuitz. which maybe traced; tromgrounded battery; lower outerarmaturev and .con-

tact of relay 2, through the winding: of relay 2l0, conductor 2l9, break contact and upper ar-- mature of relay 222, conductor 225', contacts and lower-inner armature of relay 2l-0 to ground."

Relays l lll' and I I2- are responsive to message signal-impulses transmitted over the line circuit. Relay- H0 has no efi'cc't'on the power supply to printer-motor I04 because relay- I'H is locked up-overit's leit-hand armature. Relay H2, however, is efiective to operate printer magnet I02 so that a home record maybe had of the "transmitted message. a L I V Thecontacts or; switch bank II to which no printers are connected, are connected to ground and thus made busy; so that the wiper: cannot stop on a blank con-tact Disconnection; by'the subscriber 7 When the'subscriber at station-;A has completed the transmissionof a 1 message, he transmits the double shift signal, or upper case H,- which shuts down the motor of printer I04 and opens-them'otorcontrol contact 320 at printer 304. This operation is well-known in the art.

The operation'of the'motorcontrol contact 320:

causes relay 2 to release, which in turn re-- leases. relay M0. Relay 2 I0 is slightly slow-torelease. to permit. relay 2|: 1* to; establish; aground connection atits. lower makeebefore-break contact before relay Itllllreleases.v Relay 2M re-.

leasing,- restores the ground at relay-2| to the ringqconductor H6 and the line circuit is again normal although the stepper switchS may remain in the position which it is in' at the time;

Manual overflow In order to provide for overflow in case all the receiving only printers are busy, each stepper switch, there being one for. each subscribers line, is arranged to have its first blank contact, that is, the first contactto which no printer is connected, on bank I connected to a jack, such as spring jack 3|0. lamp 3H associated with the line circuit to Sta-.- tion A, is connected to a contact 'of a busy relay, such as relay 2|0, one being provided for each line circuit or stepper switch. --The first blank contact on bank II to which no printer is connected, normally has ground connected to it at the right-handbreak contact of 'relay 308 to prevent the bank wipers from stopping on their respective first blank contacts. Aseach receiving only printer becomes busy, each will'cause its relay of the relays 3M, 3I5, 3|6 and 307 to operate and when all the printers are busy a circuit will close extending from ground, over the left-hand armatures and contacts of the re-' lays 3M, 3|5, 3|6 and 301, in series, conductor 323, through the winding of relay 308 to grounded battery. Relay 308 operates and disconnects at its left armature the grounded battery 3|8 from the ring conductor 6 of the subscribers loopso that the subscribers printer motor will not operate until the calling line isxanswered by the" operator. A relay, such as' relay 308,

is provided for each subscribers line circuit and r all operate when all the receiving only printers are busy.

When the wiper of bank II engages the first and relay2|| closes a circuit extending from ground I, operated contacts of call key |0'|, tip conductor H5, through the upper winding of relay 203, lower outer armature and break contact of relay 222,'make contact and upper armature of relay 2| |,.wiper in engagement with the sixthcontact of bank I, conductor 224, norma-l contacts of spring jack 3| 0, through the left-hand winding of relay 324; to, grounded battery. Relay 32 4 operates and" closes a locking circuit for itself from grounded battery, break contact and left-hand armature of; relay 325, through the right-hand winding o f relay 324, over the armature and contact of 'relay 324, through the lamp 326, through the winding of relay 321 to ground. Lamp 326 lights and re.

lay 32? operates; the operation of 'the relay causes an alarm 328 to operate. The lamp 326 and the alarm 32B furnish signals to the opera tor that aparticular lineis callingfor a connection to an idle printer, and that all the re- Also a busy lamp, such as sertion of plug 309 into jack 3|0 closes a circuit extending from grounded battery, through the winding of relay 325, normally open contacts and. sleeve of jack 3'"), sleeve conductor of cord 309, through the-winding of relay 329. Relays 325 and 329 operate. ,The operation of relay 325 causes the lamp 326 to become extinguished and alarm 328 to become silent. Relay] 329 closes at its leftehand armature and contact the operating. circuit for motor'control relay 330 and. relay 330 operates. to start the motor of auxiliary printer M2. The starting of the printer motor closes the motor control contact 33I whereby a circuit is closed from ground at the control contacts, ringconductor of cord 309, ring conductor of jack 3|0, sixth contact and wiper of bank III, through the lower winding of'relay 2|| to grounded battery. locked in an operated position as long as the. printer motor is operated.

The insertion of plug 309 into jack 3| 0 also disconnects the path through the left-hand winding of relay 324 and substitutes the path ex-.

tending over the make contact and right-hand armature of relay 329,, through the left-hand winding of relay 332, transmitting contact 333 to grounded positive battery. The operation of relay 325 connects at its right-hand armature and contact grounded positive battery 3|8, conductor 3|9, lower inner armature and make contact of relay 2| I, upper make-before-break contact of relay 2|0, break contact and outer armature of relay 209', normally closed contact of key 203,

through the lower winding of relay 208, ring conductor H6, transmitting side of subscribers loop circuit, tip conductor ||5,1through the upper winding of relay 208, outer lower armature and break contact of relay 222, make contact and'upper armature of relay 2| wiper in engagement with the sixth contact of bank I, conductor'224, tip of jack 310 and plug 309, make contact of relay 329, through the left-hand winding of the electrically biasedrelay 332, transmitting. contacts 333 to grounded positive battery.- The loop circuit has grounded positive battery on both ends which causes relay 208 to release, thereby connecting ground at its armature and contacts to the operating circuit of relay'2l0, as hereinbefore described. Relay 2| 0 operates to disconnect grounded positive battery 3 8 from the ring and to substitute therefor grounded negative battery 22| thereby putting the loop circuit in condition for operation at which time the motor at the subscribers sta-' tion A starts operating and the key |0'| is restored to normal. Relay 208 is deenergized momentarily only because of grounded negative'battery being connected to the loop circuit by re-' lay 2|0. Relay 2|0 is maintained operated in a circuit extending from grounded battery at the outer lower armature and contact of relay 2| I, through the winding of relay 2 l0, break contact and upper armature of relay 222, conductor 225, to ground at the contact and lower inner armature of relay 2| 0. Relay 2|0 in operating, also closes at its lower inner armature a circuit for operating the busy lamp 3 at the toll switchboard.

When the message is completed the disconnection takes place in the same manner as when the line is connected to an idle receiving only printer.

Broadcasting When it is desired to broadcast, the auxiliary Relay 2 is therefore Group broadcasting If it is 'desired'to transmit to a selected group of subscribers stations, the operator at the toll switchboard will depress a non-locking key correspondingto key 263, for each station to be included in thebroadcas't. The depressing of, say key 203, assuming that station A is to be included, closes an operating circuit for relay 222, extending through its 'upperwinding to grounded battery. Relay 222 operates and closes a locking circuit for itself, extending through its make contact and lower inner armature, conductor 226, through the winding of relay 2M, conductor 2| 9, to ground at the break contact and upper armature of relay 298. Relay 208 is deenergizedbecause grounded positive batteries are connected to both ends of the loop circuit of station A, battery 22'! being connected at one end by switch 2'03 and battery 213 being normally connected at theother end. Relay 2 22, in operating disconnects at its lower outer armature and break c ontaot the circuit normally extending to grounded positive battery M3 and substitutes thereforthe grounded positive battery 23-! at the armature of polar relay 2M. Relay 2-H) operates and closes at its lower inner armature and contact a circuit having two parallel paths, one extending from-ground, conductor 2-25, upper armature and make contact of relay 222, through broadcast lamp 221 to grounded battery, and the other, through busy lamp 3H through grounded battery. Lamps '22 and 3i I' light indicating to the operator that the loop circuit extending to station A is busy for broadcast.

If broadcast lamp- 22! remains lighted,'-t-he broadcast key 293 is released and therefore closes its normally closed contact, whereby grounded negative battery 22| is connected over the upper armature and make contact of relay 2H), break contact and upper outer armature of relay 2-99, normally closed contact of key 203,'throug h' the lower winding of relay 2E8, to the ring conductor l lt of the loop circuit to station A, tip conductor l l 5, through the upper winding of relay 208, outer lower armature and make contact of relay 222 to grounded positive battery -23l at the armature of relay 2!. Relay 208 being of the differential type does not operate and relay 222 re- I mains operated to its locking winding.

The insertion of plug 303 in the broadcast flack 3 13 closes an operating circuit for relay 22-8which iscomm'on to the broadcast circuit of all the subscribers stations, the circuit being traceable from ground, through the winding of relay 32'9, sleeve of plug 339 and jack 313, conductor 334, through the winding of relay 228, conductor 229, to grounded battery 335. Relay 329 operates as hereinbefore described to start the motor of printer 3 l2. Relay 2 28 operates and closes :a circuit extending from ground at its armature, through the right-hand winding of relays 2-05, 202, etc. in series, one of which relays is provided for each subscribers circuit, conductor 230, operated contact 331 to battery 335j The .operationof relay 329 closes the tip or transmitting circuit from grounded battery at transmitting contacts 333, through the left-hand winding of relay 332, right-hand armature and contact of relay 329, tip conductor of plug 309 and jack 313, conductor.:=336, th rougliythe left hand windings, :in series, (of lrelaysflaZ-OZ, 205, I etc.

Relays 23-2, .235, sets. operate tothe positions show-n -response to currentifiowing fromthe grounded battery :attran'smitthig contacts 333-.

The .=cu-rr'ent's respectively. flowing through the windings of each of'relays 202, 205, :etc. oppose each other ethecurrent in the leithand winding predominating. Each :ofr-the-relays. 2%,12 95, etc. respond to the signal impulses.transmittedzfrom printer 342. Relays (20, 1,294, etc. respond to their respeotivelyeassociated relays 202, 205,, etc.

and transmit the signals to their respectively .as-.

sociated loop circuits provided such circuits are selected for the broadcast by operating the ire-'- spective keys, such as key 203, shown: .for the.

loop circuit to station A.

When the broadcast message :is

transmitted from the printer 3l2 or a printer or any one of the stations connected in the broadcast circuit whereby the motorcontrol contacts in each primer are open. The opening ofcthe motor control contacts :at the receiving station of the broadcast circuit stops their respectively associated motors. In :thecase of, station A, relay I! 3 releases and ground I 1 L is thereby connected to the tip side 'ofthe stationgloop so current flows completed, 3 1 stop signal which may be the upper case 1H,

The release. of relay 222 extin- V switchboard operator at the central ofiicethen:

lays-209, 206, etc., which areindividual to the subscriber s station, are operated. Each of the re- 7 lays, 203,. 206, etc. automatically performs and causes to per-form the same function that reach of the manually operated keys, such 'as key .283,- performs incompleti-ng a group broadcast. The remainder of the operation iscthe same as described above for thegroup broadcast.

What is claimed is:

.-l.: In a :signal transmission switching system, the combinationof a plurality of sending, 'sta tions, a plurality :of receiving stations, andan auxiliaryosendingxand receiving station, rotary devices individual to each of 'said sending stations for selecting any one 'ofsaid receiving stations, a normally deenergized circuit extending from .eaohof (the sending stations to each of'said devices, operating means ateach of said sendingand adapted when all receivinglstation's :are busy, for connecting :said auxiliaay station to the send ing station connected to the last operated rotary device. r

2. In a signal transmission switching system, the combination of a plurality of sending stations, a plurality of receiving stations, and an auxiliary sending and receiving station, a signal printer at each of saidstations, a rotary device individual to each of said sending stations for selecting any one of said printers at. the receiving stations, a normally deenergizedcircuit extending from each of said sending stations to each of said devices, operating means ateach of said sending stations arranged when operated by a single movement to close one of said circuits and to thereby cause one of said devices to automatically select an idle printer at one of said receiving stations, and indicating means for informing an operator that a sending station has been connected to an idle printer at one of said receiving stations, other indicating means for informing the operatorwhen all the printers at said receiving stations are busy, and means connected to each of said devices and adapted, when all receiving stations are; busy, for connecting said auxiliary station to the sending station connected to the last operated rotary device.

3. In a signal transmission switching system, the combination of a plurality of sending stations and a plurality of receiving stations, a signal recording device at each of said stations, rotatably stepping devices individual to each of said sending stations for selecting any one of said recording devices at the receiving stations, a normally deenergized circuit extending from each of said sending stations to each of said selecting devices, operating means at each of said sending stations arranged when operated by a single movement, to close one of said circuits and'to thereby cause 1 the selecting device connected to said closed cir-' cuit to automatically select an idle recording device at one of said receiving stations, indicating means for informing anoperator that a sending station has been connected to an idle record ing device at one of said receiving stations, other indicating means for informing the operator when all the recording devices at said receiving stations are busy, and another signal device arranged to be connected by the operator to said circuit when all the other recording-devices are busy, for receiving the signals.

4. A signal transmission system according to claim 3 wherein the signal device connectible to the circuit by the operator is adapted to transmit signals to two or more of said recording devices at said sending stations simultaneously.

5. A signaling switchingsystem comprising a plurality of calling stations, a called station, a signal transmitting and receiving deviceand driving. means therefor at each of said calling stations, a'plurality of signal receiving devices and driving means respectively provided therefor at the called station, switch means at each of the calling stations for establishing a connection between itsassociated signal transmitting and receivingdevice and the first idle signal receiving device, circuit closing contacts included in said signal receiving device for operating thedriving means therefor in response to the establishment of said connection, and other switch. means in each of the, signal transmitting and receiving devices for sending a special code signal to the operating signal receiving device selected in said connection whereby said'circuit closing contacts are opened to stop the operation of the driving means of saidoperating signal receiving device.

.6. In 'a signal transiriissionlswitching system, the combination of a central oflice, .a plurality of remotestations, a signal transmitting and receiving printerand a driving motor therefor at each or said stations, rotary selecting mechanisms at said central office, individual to said stations, normally deenergized circuits interconnecting said stations and said selecting mechanisms, calling means at each of said stations for energizing one of said circuits whereby the operation of one of said selecting mechanisms is started, a plurality of signal receiving printers and motors respectively provided therefor at said central ofi'ice; a plurality of relays for respectively controlling said printers and motors therefor, said relays be ing arranged to be automatically connected in successive order to one of said circuits in response to the operation of the selecting mechanism connected thereto, said motors for said receiving and said transmitting and receiving printers arranged to operate, in response to the establishment of a connection between said selecting mechanism and said receiving printer, and normally inert motor control means for said receiving printer arranged .to operate when the motor therefor operates, said control means being arranged to restore to normal in response to a special code signal transmitted by the transmitting and receiving printer associated with said one of said selecting mechanisms whereby said selecting mechanism, said receiving printer and said transmitting and receiving printer are rendered available for another call.

7. In a signal transmission system, the combinationaccording to claim 6, wherein is provided at the central office an auxiliary signal sending and receiving printer, and driving means therefor with means adapted when all the signal receiving printers are busy, for connecting said auxiliary printer to the signal transmitting and receiving printer at the calling station, the driv ing means for said auxiliary printer being arranged to stop in response to a special code signal transmitted by the signal transmitting and receiving printer at said calling station.

8. In a signal transmission system, the combi nation according to claiind'wherein is provided at the central oilice indicating means for inform- .ing an operator that a signal transmitting and receiving printer at a remote station has been connected to an idle signal receiving printer at the central oflice, and other indicating means for informing the operator when all the signal receiving printers at thecentral oflice are busy.

9. In a signal transmission system, the combination according to claim 6, wherein is provided at the central ofiice an auxiliary signal transmitting and receiving printer and driving means therefor, with means for connecting said auxiliary printer to the transmitting and receiving printer at one or more remote stations simultaneously and for starting the driving motors of the transmitting and receiving printers at said remote stations, and means included in each of the transmitting and receiving printers at the remote station responsive to'a special code signal transmitted from said auxiliary printer for stopping the drivingmotors of the transmitting and receiving printers at the remote stations simultaneously.

GEORGE A. LOCKE.

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