US2129741A - Telegraph switching system - Google Patents

Description

Sept. 13, 1938. o. c. LEVY.

TELEGRAPH SWITCHING SYSTEM 3 Sheets-Sheet 1 Filed Aug. 9, 1935 ,img

JNVENTOR.

OSCAR C LEVY .BY Z Z v ATTORNEY.

Sept. 13, 1938. o. c. LEVY 2,129,741-

` TELEGRAPH SWITCI'IINKG SYSTEM Filed Aug. 9, 1935 ssheets-sheet 2 j@ Noz Sept. 13, 1938. o. c. LEVY Y TELEGrRAPI'!l SWITCHING SYSTEM OSCAR C. LEVY Filed Aug. 9, 1935 r?. am

. the supervision and guardance of the established station such as may be located along a railroad PatentedtSept. I I y UNITED STATES PM?ENTV oFF-lcs rml-:GRAPH swl'rcnnvc srs'rnu oscar c. Levy, Baltimore, Ma., asslsnor to sssociated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application August 9, 1935, serial No. 35,425 29 claims. (ci. 11s-2) This invention relatesin general to telegraph tion on the same line; while Fig. 3 discloses a systems but more particularly to telegraph switchterminal station. ing systems wherein means are provided at the e i printing telegraph stations to' selectively estab- General description 5v lish communication between any desired ones o! In thc System dlsclcscda single Wil-telegraph 5 Said Stations: v line-indicated as |00 and normally having cur- The principal object of the invention iS t0 derent owing thereover extends in serial relation sign an improved telegraph switching system in through a, plurality of telegraph stations, only which the selection and control of the telegraph thi-ce Stations of which have been illustrated. al-

l0 stations is considerably facilitated and in which though 1t win be understood that any laltlitional the switching apparatus employed'and the opera number of similarly arranged stations can be contion thereof is greatly simplied. c nected in the line circuit. If'or the purpose of AV particular object is to effect the operation illustration, the three stations disclosed are each and automatic release ofthe selective switches; of a diierent type. In Flg.'1 an ordinary wayvv connections; and the operation of the printing is indicated. The equipment of this Way statelegraph equipment, all over asingle wire teletion' comprises a step-by-step" selecting switch graph line by means of improved simplified appav 0f the well known Strowger type as used in autoratus and circuit arrangements. l f I matic telephony in which the wipers'are rst A feature of the present invent-,ion is concerned elevated to a particular ylevel or row of bankco'n'- 20 with a system comprising a plurality of printing tacts and then rotated to the desired contact in telegraph stations arranged .Qn a, cgmmon une in the level. Incorporated in the selective switch which each station is provided with a selective is an additional Small lil-point rotary step-byswitch directively controlled from any station and Step Switch S 0f Wen known form- Inserted in '25 in which the switches are all flrst operated and the une 0f this Station is -8' Printing telegraph 25 then released to select the particular station demechanism comprising 9' transmitter or keyboard. sired, and then operated in accordance with v and a printer by means of which communication a common code to effect thc setting of the mmh can take place over the line between the stations. ing telegraph equipment of the selected Station so As this telegraph mechanism is well known in the that it can subsequently be operated for com art it need not be further described in detail. 30 munication purposes. An impulse sender or calling device lfor stepping A further feature is concerned with the Vpro the selective switches; 'a relay for-controlling the vision of means whereby a particular station on ggrmohtere? :aagugrgge 1:25

the line m'ay be equipped with a single selective complete the equipment located at this way sta- .35. l swlth but mth a plurality of printing telegraph tion which for convenience has been indicated as equipments, any one ofl which may be selectively Way anonce prepared for operation over the'line.

' Additional features of the invention are premgtrtge'dzsixgerwwctioguhhlg sented in the means and circuit arrangements for provided with two sets of printing telegraph *and 40 effecting the release of established connections; control apparatus, either which can be sclSupplying operating Current 't0 the apparatus and lected for. operation by the single selective switch svj'ltch at 9' sfation? provide a terminal .station -at this station. This station, therefore, has two mth a Plulollty of concentrated Printing equipcall nmbers assigned to it, #2l and #29. An memfs accessible f1' om a plurality of unes: and to arrangement such'as this is desirable where two 45 Provide a Stepping switch .in each selective'swiwh sets of telegraph machines are located in a buildhaving variable'mens OI controlling the release ing' with each set in a different room. A singley and answer-back functions of the Selective Switohselective switch centrally located would therefore The fregUmE ubec and features Wm be be sulllcientas the lines to thetelegi'aph'eqllillwhich together with the 606011193113111! drawings is also equipped .with acurrent rectier and conillustrates an embodiment of the invention. Retrol means 'for supplying a source of current to the ferring to the drawingsequipment from an alternating current source Fig. 1 is a schematic circuit arrangement of a whenever the equipment at the station is engaged pointed out hereinafterin the detailed description mehr, are not of very great length. Thjs stai-,10h

' telegraph way station; Fig. 2 is another way stafor operation. 55

. ing mechanism such as #32.

Fig. 3 showsI a terminal station in which the selective switch is arranged to have access to a concentrated group of telegraph printing mechanisms #5L #52, and#53, any idle one of which it can automatically sel-ect. I n addition, this switch can also engage a single particular print- This terminal station has a. number of other telegraph lines entering it each provided with an individual selective switch, and certain of the bank contacts of all the switches are therefore multipled together in order that an idle one of the connected group of printing mechanisms can be selected.

As will be noted the telegraph line at each station passes in series through the telegraph transmitting and printing apparatus, the calling device, and the line relay and certain contacts of the selective switch. 1n order-to effect the selection of any one station on the line the calling operator at a station is required to dial a two-digit number. This eects. the operation of all of the selective switches on this line, but the digits of only the called station are registered after which all switches are automatically released. Means are provided for indicating to the calling operator the condition of the line and the progress oi the connection. A two-digit number such as .#II, termed the motor-start number, is then dialled resulting' in, the conditioning of the telegraphlc apparatus atv the called station so that telegraphic communication can begin. As many additional stations as desiredmay be brought into the. connection by the calling operator dialling the wanted station numbers in succession after which the common motor-start number is dialled.

' In calling the terminal station with an individual printer number such as #32 the operations which take place are the same as that which take place at the ordinary way-station. When, however, a number is dialledy such as #5| the selective switch at the terminal station does not automatically re- .I lease and it is not necessary to dial the motor start number.

An idle printer mechanism is automatically selected for operation immediately.

Selection of way station. #61

observing the condition of his supervisory lamp LI. If'the line is not in use the lamp is dark. This-istrue of all station lamps on the line.v 'I'he calling device or impulse transmitter is then ac`- tuated by the operator in accordance with the digit 5 therebytransmitting six break impulses over the telegraph line v'IllII through all of the switch line relays at all the associated stations.

' Line relay 5 of the selective switch at station #EL as well as all otherline relays, is normally held in energized condition over the line, and at its front contacts k1 holds slow release relay |0 oper ated `over an` obvious'circuit.A Responsive tothe line interruptions 'the line relay repeats them at A the back contactsY '1' while relay IILbeingslow actingremains energized between the series ofv impulses.` The resistor connected across relay Il rendersnit still 'slower in action.

.Responsive to the'llrst break or impulse in the line, "line relay5 r deen'ergizes and Vretracts its armatures. "Atback contacts 1 it closes a'cir'cuit extending from ground through front contacts amarti ing the wipers 12 and 13 one vertical step opposite the rst level of bank contacts. The elevation of the shaft likewise results in the operation of the olf normal springs I9, 21, and 28, resulting l in their shifting to their alternate position., Line relay 5 at its back contacts 6 closes ground onto conductor 4 to close the circuit of thesupervisory lamp L. The supervisory lamp L is illuminated in this circuit and flashes in response to the impulses delivered to line relay 5. At each of the 4way stations the associated lamp is likewise lia'shed by the corresponding line relay indicating at each station the occupancy or busy condition of the' telegraph line ||i|l.A This is also an indication to the transmitting operator of the correct transmission of the impulses. The slow release vertical series relay 20 upon operating closes its :front contacts 22 to close a locking circuit for itself through these contacts and the normally open oi n'ormal contacts I9 which are now closed. The remaining series of ve impulses delivered by line relay 5 therefore passthrough front contacts I2, the now closed off normal contacts I3, rontcontacts 22, the winding of relay 20 and the vertical magnet 8 to battery. ,The vertical magnet 8 thereby elevates the wipers 12 and 13 six vertical steps or opposite the sixth level of bank contacts. Relay 20 in addition to closingv its contacts 22 at front contacts 2| closes an obvious circuit through the winding of relay I5 and the parallel resistance connected thereto to battery, resulting in the energization of this relay which at itsfront contacts I 1 closes a locking circuit for itself independent of relay 20. At front contacts 23 relay 2|| prepares the circuits of relays 40 and 45 which are completed as soon as relay I5 closes ground on its front contacts I8; the circuit for slow acting relay 40 being closed by way of lthe now closed oil. normal contacts 28, front contacts 23, through the winding of relay 40 to battery, while that of relay 45 is closed through the oil normal contacts 28, back contacts 31 and 42, through the winding of relay 45 to battery. Relay 45 is provided with a slug on the heel end so that it is slow to energize, while relay 40 energizes immediately and opens at its back contacts 42 the circuit of relay 45 before'it is fully energized, and at the front contacts 42 closes a locking circuit for itself independent of contacts 23.4 ;At front contacts 4I the circuit for relay 35 is prepared. Relay 20 remains energized throughout Y the series of impulses and when these cease line relay 5 again becomes permanently energized and at its back contacts 1 opens the' locking circuit of relay 28 which extends through its front contacts 22. and relay 20 consequently deenergizes and transfers the impulsing circuit to the rotary magnet 3. The telegraph now proceeds to dial the seconddigit of the called station #8L In response theretoline relay 5 deoperator, at way station #2| energizes once and at its back contacts 1 closes a Y circuit through front contacts I2, the now closed oi! normal springs I9, back contacts 22, front con- A tacts 4|, winding of the slow release relay 35,

ing circuit for itself through which additional series of impulses are received in case there are more than one. Relay 35 at its back contacts 31 opens the energizing circuit of relay 46 which extended through its front locking contacts 42 from the ground on front contacts I8 and off normal springs 28. Relay 46 consequently de- A energizes and prepares a circuit for relay 45 at back contacts 42. After the impulse has been received relay 35 restores due to the opening of back contacts 1 of the line relay, and at its back contacts 31 closes the aforesaid circuit for relay 45.

The foregoing operations constitutethe control of the selector switch at station #6| in selecting this particular-station by positioning the wipers 12 and 13 on bank contacts #6L At all of the other stations on the line, as well as the terminal station the associated selector switches will likewise be operated to the bank contacts corresponding to bank contacts #6L At these locations, however, the bank contacts will'be dead, that is, no operating circuits will be connected to them. At station #6L however, the bank contacts #6I will be engaged by wipers 12 and 13 and the upper bank contact'is connected directly to a relay 66.

As a result of the energization of relay 45 it closes ground on its front contacts 46 through the winding of slow-to-energize relay 65, the wiper 12, bank contact #6I upon which it is now resting, through the upper winding of relay 66 to battery. Relay 66, upon energizing, closes a locking circuit for itself through its front contacts 62 to grounded contacts I6 of relay I5. At its front contacts 6| it closes ground onto conductor 4 to permanently` mummia@ the lamp'L to indicate to the operator at the way station #6| that his selector switch has been operated to the proper contacts at his station and also that the line is busy. At `front contacts 63. relay 66 prepares a circuit for the motor-start relay 59 of station #6L Relay. 65 at its front contactsy 16 closes ground through wiper 16 n ow resting on the lower contactof bank #6| which in this instance is dead. At front contacts 66 an operating circuit for relay 55 is prepared,

While at front contacts 69 an alternate holdingv Answer-back indication The purpose of opening the line circuit at this time is to provide an answer-back indication to the operator at the calling station #2| to advise him that the selector switch at station #6| has been properly operated and station #6I selected from all the other stations on the line. The manner in which this answer-back supervision is brought about will now be pointed out. The opening of the line at back contacts 66 results in the deenergization of line relay for an appreciable length of time. Relay 5 upon deenergivzing closes ground on its back contacts 1,

and opens the front contacts for a time suicient to permit slow release relay I6 to completely deenergize. Contacts I2 of this relay restore with.- out effect at this time. A circuit however is now closed from ground on back contacts II, front contacts I6, through the winding of slow-to-pullup relay 25 and the multiple connected resistor to battery. After a time interval relay' 25 completely energizes and operates its front contacts 26, thereby removing the short circuit from around slowto-energize relay 36 'and connecting ground through the winding of this relay and the resistor connected thereto, to battery. At front contacts'32 relay 36 connects ground to one side of the winding of relay 25, thereby shunting the current flow to the winding of this relay and permitting it to slowly deenergize. After ashort time relay 25 opens its front contacts '.26 again and closes the shunt circuit around relay 36, while at back contacts 26 it now completes a circuit extending from ground through front contacts 3|, before relay 36 has completely deenergized, through the winding of stepping magnet 48 of the stepping switch S to battery. Relay 36 upon eventually falling away opens its iront contacts 32, thereby removing the short circuit from around relay 25 so that it can again energize, from the ground on back contacts At back contacts 26 relay 25 opens the circuit of the stepping magnet 46 andy at the back contacts again` closes the circuit of relay 36. The alternate interaction between relays 25 and 36 continues indennitely as long as slowl relay I6 is deenergized; Each time that relay 36 energizes and closes its front contacts 3|'and subsequently opens these contacts the stepping magnet 48 receives an impulse of current which results in the rotary movement of the wiper 49 step by step across its associated bank contacts.

Responsive to the first step of wiper 46 it engages/the first bank contact thereby closing a circuit extending from ground on the Wiper through front contacts 69, which are at this time closed, through the winding of relay 55 to battery. At its front contacts 51 relay 55 upon energizing closes a locking'circuit for itself extending from grounded front contacts 66. Re-

sponslve to' the first step of the wiper 66 the off Anormal contacts 66 are closed, resulting in the preparation of the circuit of the release magnet 61 of the switch S. At the front contacts 56 relay 65 again closes the circuit of the telegraph line |66 which during this time has been opened at back contacts 66. This action results in the energization again of the line relay 5 so that at its front contactsv itagain/ closes the circuit ofslow-release relay i6. Slow-release relay I6 upon 'energizing at its back contacts opens the energizing circuit of. relay 25'to stop the interaction of this relaywith relay 36. At front contacts il a circuit is closed by relay iextending to off normal springs 44 and release magnet 61 to battery. The operation of the release magnet 46 results inthe restoration of the wiper 46 from the bank contact upon which it had been resting. An instant before wiper 66 reaches its normal positi'onthe off normal contacts 64 are opened to deenergize the release magnet 61.

During the time that the telegraph line circuit |66 is opened at back contacts 66 and subsequently closed at front contacts .56, the supervisory ,lamp L| atstation #2| is given a. prolonged fiash causedby the line relay |65 of station #2| deenergi'zing and closing contacts |66 to light vthe lamp. This likewise occurs at all other stations and serves as a busy indication to these stations, and as an answer-back indication to the operator at station #2| to advise him that the switch at telegraph station #6| has Automatic release of switch y lAs a further result of the energization and locking up of relay 55 which terminates vthe answer-back period, ground is closed on its front contact 58 through the vertical shaft springs 43, Ywhich are only opened when the wipers are posicuit for itself. by way of the oil.' normal contacts 21. As a result of the energization of release magnet |3 the selector switch shaft is caused to be released. 'I'he wipers 12 and 13 are withdrawn 'from the bank contacts upon which they 1 are resting and an instant before the wiper shaft has reached its normal position the on' normal contacts I9, 21,` and 23 are opened. At 0E normal contacts 21 the locking circuit of release magnet I3 is opened. At oif normal contacts 26 the, circuit of relay 45 is opened and it restores. As the wiper 12 leaves the contact-6| the circuit of relay 65 is broken and this relay deenergizes, opening the holding circuit of. relay 55 at front contacts y|58, while at. back contacts 66 it closes a point in the telegraph line circuit which, however, is closed at this time at contacts 56. Relay 55 subsequently deenergizes and opens the initial operating circuit of the release magnet I3 at its front contact 55, while at front contacts 51 it opens a further point in its locking circuit. At

i front contacts 56 the Vpreviously closed point in the circuit of the telegraph line |05 is opened. The selector switch at way station #6i is now in its normal released position with relays 5, Il), I5, and 60 held energized at this time.

`The operation and release action ci the selector switches at each of the other way stations on the line takes place exactly in the same manner as that described in connection with-the selector switch at station #6L with the exception that their associated relays corresponding to cutthrough relay 6|) ,oi station #5i will not be operated. The stepping switches S at each of. the

" other stations connect their relay corresponding to relay 55 up for operation to eect the release action of the switch. At station #2i the corresponding cut-through relay which is not operated is |65 while atstation #26 at the same location the relayis |80. Relay 65 being now locked in energized condition the circuit from contacts 6| over conductor 4 to the su rvisory lamp L maintains this lamp lit to call he attention of the operator at station #5| that he has been called, while the supervisory lamp LI at station #2| having been flashed once to give an answerback indication informs the operator at this station that the proper connection has been made. -The lamps at the remaining stations on the line are dark at this time.

Starting lthe printer motors operate their wipers one vertical step and one Y rotary step in the same manner as has been previously described 1n the first setting of these switches. The line relay 5 falls back once for each digit, the first operating lthe vertical magnet 8 and the second lthe rotary magnet 9. Wipers 12 and 13 are thereby placedinto engagement with bank 'contacts #I I. As a furtherre'sult of the engagement ot the wipers with the bank contacts #II on the iirst level, the first level shaft springs 43 are opened thereby opening a point in the circuit of the release magnet II to prevent the possibility of the release of the switch at this time. Slow-to-energize relay 55 is now energized as before from relay 45 by ground on front contact 46 ofthis relay, winding of relay 65, wiper 12 resting on bank contact #I I, through the resistance 14 to battery. At back contacts 66 relay 55 again opens the line circuit |55 to transmit the answer-back signal to the sending operator at station #2| to inform him that he has correctly dialled the motor-start contacts at way station #6LA At front contacts 55 and 55 relay 55 closes the initial energizing and the locking circuits for relay 55 which at its front contacts 56 again closes the line circuitl to end the answer-back time interval.

During the second answer-back' transmission the stepping switch S operates as before to set its wipers 49 opposite the first bank contact to close the initial energizing circuit for relay 55 and terminate the answer-back time interval at contacts 58. When'the line circuit is again closed relay 5 energizes and closes the circuit to relay l l I0 to stop the interaction of relays 25 and 3l and to release the stepping switch S. At grounded front contact 56 relay 55 prepares a circuit for release magnet I3 which, however, is opened by the shaft spring 43 at this time. At grounded front contacts 10 relay 55lcloses a circuit extending from these contacts tothe wiper 13 and the lower bank contact #Il upon `which it is now resting, iront contacts 530i relay 65 which has previously been locked energized the rst time the selector switch was operated, then over the circuit extending to the motor-start relay 59 to battery. /Relay 59 upon energizing closes an obvi- 4ous circuit for the operating motor of the printing and transmitting telegraph mechanism. The operator at station #2| operates his motor-start key |26 which closes a local circuit for his printing and transmitting apparatus motor. Telegraphic communication may now take place over the telegraph line |00 between station #2| and station #6L The line relay 5 as well as all other relays along the telegraph line |00 mayy utter slightly in response to the telegraphic impulse transmitted over the telegraph line |00, but this will have no eect upon the switches as the duration of the impulses is not of suilicient length to permit the relay I0 to restore between the impulses and because the circuits to the operating magnets are open.

The dialling of the motor-start number by the operator at station #2| in addition to operating the switch at. station #5I to the motor-start level also operates all the other switches on the lineincluding that at station #2| and terminal station #5L The printing motors, however, willnot operate at these other stations due tothe fact thatthe associated relay corresponding to relay 60 ofl station #5| was not operated. The switches do not release but remain with their wipers in engagement with the motor-start con tacts as long as the connection exists.

It will be appreciated that when a telegraph station has been called by another station in addition to the operation of the associated supervisory lamp, the motor of the selected station will commence operating as an indication to the operator at that particular station that his station is sclected and a message is to be sent to his position. In case he is the sending operator it is not necessary to dial up his own selective switch in accord.- ance with his own particular number, but merely to operate his motor-start key such as B3 at station #6| or |26 at station '#ZI. This results in the direct operation of the motor.

It will be apparent from the foregoing description that the operation of the supervisory lamp indicates to the operator at the associated station the condition of the telegraph line at all times.

Wheneverv the lamp' is dark it is anv indication that the line is -idle and no messages are being transmitted. If the lamp is in continuous illumination it is an indication that the line is engaged in transmitting telegraphic messages. If the lamp iiashes intermittently in accordance with the particular number being dialled it is an indication that dialling is taking place. When the answer-back indication is ashed back to the sending station from a switch which has been set upon a particular contact, thelamp flashes slowly off and `on again to indicate the answerback condition. A still further indication is given by the lamp intermittently hashing oil and on which occurs continuously whenever the terminal station printers are all in busy conditionwhich will be shortly explained.

By moving the circuit connections extending from the bank contacts of the switch S to am! other desired one of thebanks to which the wiper 49 has access, variable time intervals may he introduced to compensate for various lengths of the line circuit between the stations or where diiferent line conditions may exist. The lengthof the answer-back signal and release periods of the switches at different stations is thereby' conveniently varied. For example, by moving the conductor which is now attached to the fth bank contact to the sixth or seventh, the length of time required for the release of the particular switch at that way station is considerably extended. Similarly by moving the conductor attached to the third bank contact to the ith' or sixth the 'Til time during which theroperation of release relay t is started, and therefore the time of the line opening, is likewise lengthened. ln a similar manner the time during which the conohictor-con-l nected to the rst bank contact is rendered ei iective may be varied by moving this conductor along to one of the other bank contacts and thereby lengthen the time during which relay 555 is started to operate, which terminates the answer-back period. This change lerlgthens the period during' which the contacts t@ are operi and o@ are closed to give a longer time interval i'orthe answerback signal.'

Release of connectie/lc After the telegraphic communication has been terminated the lrelease of the connection may take place from either oi the stations #2l or ttul. .assume that release is effected at station #66, the

operator thereat will momentarily operate thel release key iiii at her position. This places ground on the conductor extending to release relay @il and its winding, to battery. At its front contacts it a locking circuit for itself is completed to grounded front contacts it of relay i5, independent of release key et. At the back contacts iii of relay 5@ a point in the continuity of the circuit of the telegraph line iii@ is opened. The circuit of line relay t as well as all other line relays on the lineis consequently opened' and permits this relay to restore its contacts l', thereby opening the circuit of slow relay itl which after a time completely deenergizes. Relay i6 after restoring, at its back contacts i2 closes a point in the switch release magnet circuit from back contacts of armature 1. At its back contacts'll it connects ground through the front contacts IG of relay l5 which is still locked energized, through the winding of slow to energize relay 25 andthe resistance to battery. Relay at its front contacts 26 removes the short circuit from around relay Sil and closes the circuit through this relay. Relay 3l] upon energizing at its front contacts 3l prepares the circuit ci the stepping magnet 48 of switch S which is`closed as soon as relay 25 is short circuited at contacts 32 to permit its back contacts 26 to close the circuit to the stepping 'magnet 48. Relays 25'and Sil contlnue the foregoing interaction, alternately ener-f gizing and deenergizing each other and operate the stepping magnet it in a step-by-step manner to rotate the wiper itil of the switch across its bank contacts. As it steps onto its first bank contact no enect is produced on relay as it is locked energized from ground on front contacts 68 through its own locking contacts 5l. When the third bank contact is reached by the wiper to, ground is connected from this wiper without ef feet at this station, however, as relay 5K2 already has been operated by key at, but the relays corresponding to relay o@ at all other stations will be energized to effect the releasey oi the selector switches at these stations -asiwill be pointed out.

Wiper il@ eventually rcacheslits fifth bank contact, thereby connecting ground through one side of the resistance and winding of relay i5, short circuiting the relay and permitting it to restore its armatures.l At its front contacts il it opens its original locking circuit, while at iront contacts it itopens the circuit for energizing relay 25 and` this in turn permanently restores and prevents further interacting between relay iiti and this relay to stop the operation of the stepping switch S. At grounded front contacts iii relay its removes the locking ground which extended to locking :front contacts for relay t@ and permits this reiay to restore. it back contacts 5i the telegraph line circuit ill@ is thereby again permanently closed. This closure results in the reenergization of the line relay ii which. at its front contacts i again closes a circuit through the winding oi relay ill. it itsfront contacts ii relay iii closes a circuit i'or the release magnet lil d oi the stepping switch S by way of the new closed ofi normal springs rThe energization or release lrriagnet l'i permits wiper @il under action of a tension spring to restore to its normal posin tion, which an instantioeiore reaching normai position opens the ofi-normal contacts dfi, perm mitting the release magnet il to deenergiae.

Relay i5 in addition to disconnecting the loclring'grounci at its iront contacts it from relay o@ iikewise opens the locking circuit extending through iront contacts oi relay titl. Relay t@ thereupon deenergizes and restores its armatures. it iront contacts to it opens a point in the circuit of the motor-start relay R/el'ay it at its back contacts iii closes a circuit, before relay lo has fully energized` from its grounded back contacts il, the oir-normal vcontacts 2i, and the winding of .release magnet i3 of the selector switch to battery. At its contacts it magnet i3 upon operating closes a locking circuit for itself throughon-normal contacts 2l. The energization of the release magnet i3 restores the shaft carrying the wipers l2 and 'i3 to its normal position and out of engagement with the set of bank contacts #i i i. An instant before the shaft reaches its lowermost position the off- normal contacts 21, 28, and IS are moved to their alternate positions and at off-normal contacts 21 the circuit of release magnet I3 is permanently opened. 'I'he shaft springs 43 are also closed. The restoration of the wiper 12 from the bank contact upon which it was resting, opens the circuit of the relay 65 which after an interval restores its armature. Relay 65 at its back contacts t@ again closes a point in the telegraph line toil around front contacts t. At grounded front contacts t8 the locking circuit ci relay Se which extended through its iront contacts 5l is opened and this Vrelay restores its armatures. At front contact 61 the ground connected to the lamp conductor #l is opened and the supervisory lamp becomes dark, indicating to this particular station #lil that the switch has been restored to normal position. Relay restores as soon as the oir-normal contacts 2S are opened.

The foregoing release operations of the selector switch at station #di occur in exactly the same manner at the remaining way stations along the line, except that instead of directly energizing relay 5@ by the operation of the release key such as lid at each station, the opening of the telegraph line at back contacts 5l permits the stepping switches S at these various stations to operate their wipers to a position corresponding to the third bank Contact of the switch so as to energize the relay in the associated selector switch corresponding to the relay he.

Selecting either of two stations at one location The arrangement shown in Fig. 2 as has previously been stated, comprises two separate telegraph stations #2l and #2253. As these two telegraph stations may be located, for example, in different rooms of'a building, it is not necessary to provide a separate selector switch for each station. The circuit arrangement of the selector switch is exactly the saine as that described in connection with the way station #illoi Fig. l and as the detailed operations have already been described they will only be pointed out generally hereinafter. When station #il is dialled from any of the other way stations the switch steps its wipers i12 and |13 up to the bank contacts comprising #2L This results in the cnergization of relay itt which locks to its front contacts under control of relay lill. Relay lili! in locking up, at its contacts H53 prepares the circuit of the motor-start relay 459 of telegraph station #2L 'Relay lili when it energizes in series with relay opens the telegraph line circuit lil@ at its back contacts |86 in order to send the answerback signal to the calling station. This opening of the line for the answer-back signal, results in the falling back of line relay H35 to start the step-by-step operation of the stepping switch Si, which, when its wiper itil encounters its first 'bank contact, closes a circuit through contacts of relay' it for relay |55. Relay le?, at its front contacts S536 again closes the line circuit to terminate the answer-back period. At its grounded iront contacts |58 it closes a circuit through the vertical shaft springs M3 to the release magnet M3, thereby effecting the release of the switch. The stepping switch Si is released, as has been pointed out, as soon as relay lill again energizes. The answer-back flashing of the supervisory lamp at the calling station indicates to the operator thereat that the selection has been made and that the circuits are now in condition for the dialling of the motor-start number. This motorstart digit again operates the selector switch at all the way stations including thedesired station and steps the Wipers |12 and |13 upon bank contacts thereby again resulting in the transmission of the answer-back signal and in addition the closing of the ground from grounded contacts l'ill of relay |65 through wiper |13 and the bank contact upon which it is resting, front Contact itil, and motor-start relay |59, resulting in the operation of the motor at station #2L Telegraphic communication can then begin between the calling and called stations, the lamp Ll and all other supervisory lamps at other Way stations being steadily illuminated to indicate the busy condition of the telegraph line lDll. Release of the selector switch is eiected by the operation of the release key such as E21 at either the calling or the called telegraph station. If release is brought about at station #2| the momentary operation of release key |21 results in the energization of relay l5@ which at its back contacts it opens the telegraph line vcircuit to eect the release of the associated selector switch and all other selector switches at the various way stations on the line. As a consequence the stepby-step switch Si steps around to the fifth bank contact to short circuit relay it thereby permanently effecting the control of 4the release of the switches. The station #2| is therefore selected in the same manner as if it were only a single station at a particular location such as Fig. l.

Should an operator at any way station dial the digit #2li the selector switch in Fig. 2 would operate in accordance with this digit to step the wipers i12 and ll of the switch upon the bank Contact set #2i resulting in the energization and locking up of relay |89 which at its front contacts lei prepares the circuit of the motor-start relay lee, which is completed when the selector switch subsequently releases and is reoperated in accordance with the motor-start number. The circuit for the motor-start relay |83 is cornpleted by relay ll through ground at front contact il@ and the wiper |13 resting on bank contact #l l. The answer-back signal is again sent at the back .contacts itt to inform the sending operator that the motor of telegraph station #29 is operating and that telegraphic communication can begin. The release action of the selector switch .is brought about in the manner previously pointed out. The'rclease conductor |28 andthe supervisory lamp conductor $29 are common to both stations so that the release and supervision can be had at either one. The motor-start and line leads, however, extend separately to the stations.

it will be understood from the description given of the operation of the way station #6| and way stations #2l and #2Q that any additional stations on the telegraph line lill) may be conditioned for operation by operating their selective switches from the sending station, one at a time. In this manner, three, fourfiive, or more stations may all have their cut-through relays, such as the relay corresponding to '60 at station #6| operated by dialling up the switches successively and after each selection have the switches automatically released. Subsequently when the motor-start number is dialled and all the switches are set upon the bank contact #Il those stations which have their cut-through relays operated will have their motor-start relays energized to start their' motors. Telegraphlc messages will therefore be. transmitted from the sending stahappen that at certain way stations along a railtion to all of the way stations which have been selected and placed in the conference circuit. As each station. is provided with' a receiving printer and a transmitter or keyboard each station can both send and receive messages.4

v Rectifier control A `In the telegraph station shown in Fig. 1 it" has been assumed that the selector switch and other road telegraph line'it is not possible to obtaina source of direct current, but a source of' alternating current of a particular frequency may be available. In an instance of this kind illustrated in Fig. 2 a full-wave rectier is provided for converting an alternating current source into direct current for -supplying the battery current for the operation of the various relays and apparatus at this particular location. 'I'he rectifier and the control circuit therefore, shown in the lower portion of Fig. 2 -comprise a transformer |99 con'- vnected to a source of alternating current and a full-waverectifier for vconverting the current. An alternating current relay |85 controls the circuit of the full-wave rectifier.

Although in the apparatus has been indicated the same as in Fig. l, it will be assumed that these connections *I are directly connected to Ithe bus bar leads extending from the output of the rectifier. Therefore, the relay I0 controlled by line relay |05 will not be normally energized until the direct current supply has been connected up by the rectifier.

In order to'explain the operation of the rectif fier control it will' be assumed that the; selector immediate release of the switch. The same action switch of Fig. 2 is to be operated to select the station #2| from any` other station along the telegraph line. In order to first prepare the rectifier for operation so that the equipment at the stationat Fig. 2 can be operated, the sending operator must first open the telegraph line- |00 for a short period of time which must be longer than the dialling of the digit 1, for example. In order to laccomplish this, the operator at station #6| presses the release key 54 for a certain period, this act resulting in the operation of release relay 50. Relay 50 at its back contacts 5| opens the telegraph line circuit thereby permitting line relay |05 of station #2| to deenergize for a period of time'corresponding to the length of time the release key 54 is held operated. The dropping back` of the line relays at all other way stations results in the deenergization of slow relay suchv occurs at all 'the other selecting switches at each 4of the way stations. The reclosure of the tele- -graph line circuit which results when relay 50 is released, permits the line relays 5 to again ener- Relays |90` andv gize and in turn close the circuit to the associated relays I0. v

' As a result of the deenergization of line relay* |05, Fig. 2, and during the time of the foregoing operations, the front contacts |01 are opened, thereby opening a point in the circuit of relay I0 which however, has not been energized due to the absence of battery potential at its terminals. The

closing ofground on back contacts |06 however,

connects ground to the conductor extending from control relay |95, back contacts |92, through the winding of alternating current relay |85, the sec- `ondary of the transformer |99 to ground. Relay energizes from alternating vcurrent received from'the A. C. source, At front contacts |86 the lcircuit of the full-wave rectifier is connectedl through its winding to battery. At its front con-- y10 these'contac'ts, back'contacts |96 of the rectiiier tacts |9| an alternate circuit for the alternating v current relay |85 is completed. independent of line relay |05. At the front'contact's |92 a circuit is completed from grounded back contact |06 of the line relay, back contacts |96, to the conductor |29 extending to the lamps LI and L2 in parallel. This notifies the operators at these stations that a call is about to be received. The calling operator at station #6| then proceeds to dial the digits of the telegraph station #2| resulting in the operation of the selective switch thereat to associate the wipers |12 and |13 with the bank'contacts #2L and the operation and locking up of the relay |60, which in addition to preparing the motor-start relayfcircuit |59 at its front contact |63. closesl a further point in the circuit of the supervisory lamps LI and L2 at front contacts |64. The motor-start number is then dialled resulting in the stepping of the switch the second time into engagement with the bank contacts #I toy complete the circuit from grounded front contacts |10- of relay |65 to the motor-magnet relayn |59. The starting of the motor in addition to the lighting of lamp LI at the station #2| indicates that this station'has been selected. The remaining operations are the same as have been heretofore described.

When the release lof the connection is to be brought about the operation of the release key 54 of the calling station #6| eiects the release of all of the switches involved in the connection. At

way station #2 l, when the switch SI encounters itsthird bank contact, groundpfrom wiper |49 isv connected to the conductor |28 attached to this bank contact. If the release is effected at station #2| the operation of release key |21 directlyl grounds this same conductor. Relay |50 is thereby energized, and' at its front contacts |52 closes the locking circuit for itself under control of contacts ||8 of relay H5. At lback contact |5| the telegraph. line |00 is opened for a period of time to l -insure the stepping of the step-by-step switches S to a position which will permit the short circuiting of the relays such as |5 and eiect the release of the associated switches.

As a further result of the groundingV of con- 'duetor |28 relay |95 of the rectifier control equipment is energized and at its front contacts |98 closes 'a locking circuit for itself. At front contacts |91 a further point in the circuit of the su- 4relays such-as |05 again energize over the telegraph line. At contacts |06 the circuit extending through front contacts |96 holding relay |90 energized is opened and relay |90 thereupon restores. At the front contacts |9| the circuit extending to the alternating current relay |85 by way of the secondary winding of transformer |99 is opened and thisl relay upon restoring opens the front contacts |86 to disconnect the rectifier from the source of alternating current. This stops the supply of direct current voltage to the equipment and as a result the relay deenergizes although relay has again'energized. Re-

lay |95 no longer having current connected to its` locking contacts |98 and its winding, after a time deenergizes. 'I he rectifier control equipment has now'been completely restored to its normal resting position as well as the remaining equipment at this way station.

Terminal station operatimz' Referring now to Fig. 3, this arrangement i1- lustrates a so-called terminal station `having assigned to it the numbers 32 and 5|. The dialling of the number 32 from another station on the line sets the selective switch at' this stationto a particular group o'f contacts numbered 32 to prepare r the telegraph equipment at the operators position #32 for operation. The switchselected as well as the other ones on the line are immediately released', after which thefcommon motor-start number is dialled. This voperation is the same as that described in connection'with the other way s tations.Y When a particular number, such as 5| `however,is dialled overthe telegraph line this station is arranged so that its selective switch is operated up to the lfth level of bank contacts and then automatically rotated to select an idle one of' would not effect the further operation of the selector switch at the terminal station.

As the terminal station #5| is, the terminus of a plurality of other telegraph lines each of which has an individual selector switch connected to it,

provision is made whereby the single group of telegraph printers are selectable from any one of .he switches. Arrangements are not provided whereby a way station on one of the lines is enablei to perform switching operations so that it vcan connect with another telegraph line and communicate thereover.

lwith'the next idle. printer. Although only telegraph printers #5|, #52, and #53 have been shown connected to contacts at the terminal station; it will be understood that these each may be mechanism or the transmitter shown in location #32 may be utilized on the line shown for transmitting thereover.

Selection of'special terminal operator In describing the operation oi' the equipment of Fig. 3 it will be first assumed that some way station on the line |00 desires to establish a connection with the special operator #32 at the terminal station. Therefore the dial such as at station #2L Fig. 2, is operated in accordance with the digit 32. The line relay 205 at the terminal station follows the impulse series and responsive to the first break in the line closes its grounded back contacts 206 to illuminate the supervisory lamp L3 and a similar action takes place at all the intervening and other way stations on the line. The lamp L3 therefore, follows the series of imf pulses indicating the dialling operations which take place over the line. At front contact 201 the circuit of slow release relay 2|0 is opened, but not for a suilicient length of time between the impulse series to permit the relay to fully restore its armature 2|2. A circuit is closed responsive to the first impulse, from the now closed back contacts 201, front contacts 2 I 2, closed olf-normal contacts 2|9, winding of' relay 220, andthe vertical magnet 209 to battery. The wipers 290, 23|,

vAt front contacts 222, relay 22l-closes a locking circuit vfor itself and the remaining series of impulses constituting .the first digit of the called number are now transmitted to the. now close'd off-normal contacts 2|9 and the front contacts The shaft of the switch is thereby further` 222. elevated'in accordance -with the remaining impulses of Vthe digit by the vertical magnet 200.

At front contacts 22| ground is connected through the windings of relay 2|5 through the resistance to battery. Relay 2|5 upon energizing closes its Relay' 240at its front contacts 242 closes a locking circuit for itself independent of contact 223 and at front contacts 24| prepares a circuit for the relay 235. At back contacts 243 relay 240 opens a point in the\circuit of release magnet 241 of the stepping switch S2.

After the irst digit has been transmitted line relay 205 again energizes. At the back contacts 201 the circuit ofrelay 2270 is opened long enough for it to retract its armature'including Y222. The first one of the nextseries of impulses in which the line relay 205 is responsive follows a path extending from back contacts 201, front contacts' 2|2, the now closed oil-normal contacts 2|9, back contactsv 222, front contacts 24|, through the winding of vrelay 235 and the winding of rotary magnet 209 to battery. Responsive 'to this i'irstV impulse relay 235 upon operating closes its locktend through these contacts. The wipers 29| to 203 have been elevated opposite the third level of bank oLntacts in response to the rst digit are now rotated to the second set of bank contacts #32,by the action ofthe rotary magnet 200. Relay 220, upon'falllng 4back after the i'lrst digit,

' opens the initial circuit oi' relay 240 at contacts n i 223 and relay 235 lat its back contacts 231 combined with a separate telegraph transmitterthe locking circuit extending to contacts 242 of vgrounded front contacts 211 to close the locking ing contacts 236, and the .remaining impulses exwinding of relay 265 while at the alternate front 262, and the wiper 293 for a purpose` to be derelay 249 so it restores. vAt the front contacts 231 relay 235 extends ground from the oli-normal contacts 228 through the winding of relay 289 to battery, thereby energizing this relay. At back contacts 243 relay 249 prepares the release circuit of the stepping switch S2. Relay 289 at its back contacts 282 opens a point in the upper contacts 282 it prepares a circuit for relay 269 extending to back contacts 269, front contacts scribed.

After Athe nal impulse of the series, relay 235 deenergizes and at its front contacts `231 opens the circuit of relay 289. Relay 289 in restoring closes its back contacts 292` so Vthat acircuit is now closed extending from grounded frontcontacts 2I9, back contacts 253, back contacts 262, upper winding ofswitching relay 265, back contacts 282, wiper 293, lowermost bankcontact #32 upon which it is now resting, through the righthand winding of relay 295 to battery. 'Relay 2,95 upon operating closes its locking contact 296 to grounded back contacts 299 and thereby remains energized. At its front contacts 291 it prepares the circuit of the motor-start -relay 269 at station #32. `Relay 265 upon energizing closes its release relay 2|9 is opened, and at back contacts 265 connects the telegraph line |99 directly in series with the wipers 299 and 29| through the bank contacts #32 upon which they 'are now resting, while at back contacts 266 apoint in the telegraph line is opened'for the purpose of giving the answer-back indication to/the sending sta'- tion and the busy indication to the remaining stations on the line.

As a result of the opening of the line circuit line relay 295 restores and slow release relay 2|9 which previously had its circuit opened at back contacts 212 eventually restores and closes ground onto its back contacts 2H, so that a circuit `is now closed from baci:` contacts 2H, front contacts2l6, (relay 2|5 being locked in energized condition), through the winding of slow-to-energize relay 225 and resistance to battery. Relay 225 energizes and at its front contacts 226 opens the short circuit around relay 239 and connects ground from the front contacts through the winding of this relay and the resistance to battery.

Relay 239 eventually energizes and at its front contacts 232 places a short circuit around the winding or" relay 225 so that it again restores its contacts 226 to short circuit relay 239 and deenergize the same. After relay 239 deenergizes it opens the short circuit from around the winding of relay 225 at front contact 232 so that relay 225 again slowly energizes. tion and deenergization oi relays 225 and 239 continues as long as relay I9 remains in its deenergized' state. closesthe front contacts 2 3 thereby completing the circuit to the stepping magnet 248 of the stepping switch S2 from grounded back contacts The alternate energizay Each time .relay 239 energizes it.

226. The stepping magnet 248 is energized stepby-step tov rotate the Wiper 249 across ltsbank contacts. Responsive to the rst advancement of wiper 249 into engagement with the first bank contact, ground is connected fromthis wiper through front contacts 261 and the winding of y relay 255 to battery. Immediately that the wiper 249 is advanced from its normal position the offnormal contacts 244 are closed. The circuit for at station #32 that hisI position has been selected...

At front contacts 256 relay 255 closes the tele'v graph line |99 around contacts 266 to terminate the answer-back'indication. The closing of the telegraph line at front contacts 256 permits line relay 295 to again energize sothat at grounded front contacts 291 it closes the circuit of relay 2 I9 by way of front contacts 239. AAt back contacts 2|| the operating circuit for relay 225 is opened to halt the stepping of the switch S2 while at the front contacts ground is extended through back contacts 243, oli-normal contacts 244, and the winding of release magnet 241 to battery. Release magnet 241 upon energizing permits the wiper 249 of switch S2 to restore to its normal position, at which point the off normal contacts 244 are opened.

The release of the selectivel switch at the terminal station is prepared as soon as the switch shaft carrying'wipers 299 to 2931s elevatedto the third level or row of .bank contacts. The third level shaft springs 243 are thereby closed and connect ground through front contacts 259k of relay 255, ofi-normal contacts 221, which were closed as soon .as the switch took its first vertical step', through the winding of release magnet 2|3 to battery. The energization of the -release magnet 2|3 permits the switch to restore toits normal position. The release magnet 2|3 at its front contacts 2|4 closes ar locking circuit .for

itself until it has completely restored independent of the off-normal shaft springs 243. The foregoing operations for releasing the switch do not take place until relay 255 has closed its contacts 259 which takes place after the stepping switch S2 is operated. An instant before the switch shaft reaches its lowermost position the off-nor mal contacts2l9, 221, and '228 are opened resulting in the opening at oit-normal contacts 221 of the circuit ofv release magnet 2|3. Grounded oinormal contacts 228 upon opening, open the locking circuit of switching relay 265 so that this relay restores and at back contacts 266 closes another point in? the circuit of the telegraphv line which, however, is still closed at front contacts 256. At front contacts 261 the locking circuit for If the operator at station #6| desires that I. K this particular motor-start level. When wiper other stations be connected to the telegraph line to receive the telegraphic messages, he proceeds to dial the digits corresponding to the desired stations. 'Ihe selective switches at all of the stations thereby operate into connection with a 293 is resting upon bank contacts #Il a circuit is completed extending from grounded front contacts 2|8, back contacts 253, back contacts 262, upper winding of relay 265, back contacts 282, wiper 293, bank contact on which it is now resting, front contacts 291 of relay 295 which is locked energid, through the Winding of motor-start relay 269 to battery. Relay 269 at its I grounded front contacts closes a circuit to the Relay 265 telegraph motor to operate the same. at its front contacts 210 locks under control of the off-normal contacts 228. At front contacts 269 it-disconnects the upper winding of relay 265 from the aforesaid circuit. At front contacts 213 and 214 the wipers 290 and 29| are connected together in series with the line through the bank contacts `upon which they are resting. At front contacts 261 the circuit of relay 255 is prepared while at back contacts 266 the circuit of the telegraph line is opened to initiate 1 the transmission of the answer-back signal to indicate to the calling station that the motorstart number has beencorrectly received and that the printing motor of the desired station is 'operating. It hasbeen explained that the stepping switch S2 rotates wiper 249 to the rst bank contact to operate and lock up relay 255 which at its front contacts 256 terminates the answerback indication. The stepping switch S2 is subsequently released as has been v`pointed out, andl telegraphic communication can take place over the telegraph line between the calling station and the selected position #32 at the terminal station. The telegraph line circuit extends through the transmitter and printing mechanism, calling device, line relay 205, front contacts 214,

Wiper 29| and the bank contact #Il on whichl it is resting, the upper bank contact upon which wiper 290 is resting, front contacts 213, back contacts 25|, back contacts 216, front contacts 256 and out over the line |00. I

Searchingl for an idle printer The foregoing operations of the selector switch :at the terminal station in accordance with a particular number such as #92 it will be appreciated, are somewhat similar to the operations described in the way stations #6| and #2L The terminal station in addition is provided with a concentrated group of telegraph printer machines which are arranged so that they are accessible not only to the selector switchillustrated but to selector switches associated with other telegraph lines. When connected with an idle one of the telegraph printing mechanisms the switch operates in a different manner thanv it will when operated in accordance with a particular numbersuch as #32 heretofore described. The switch upon being operated in accordance with a particular two digit number associated with the group of telegraph printer mechanisms elevates itswipers to the desired level and then rotates them across the particular level to select a set of bank contacts connected to an idle one of the printers, Where it remains. 'I'he switch is not subsequently released and it is not necessary to subsequently dial the motor-start number to startv the printing motor of the printing mechanism. In case additional stations are dialled to engage a conference connection with one of the printers at the terminal station, the other stations are first dialled up to the required position, released and then the terminal station selector switch is dialled up and remains in this position, after which the motor-start number may be dialled to operate the other switches to start the motors of the other way stations. The switch at the terminal station, however, does not respond to the motor-start number. Y

The dialling up of the selector switch in the terminal station in accordance with the #51, operates the various relays in a similar manner as has been explained in the operation of the switch when it was operated in connection with the #32. The Wipers 290 to 293 are elevated to the fifth level and rotated one step into association with the set of bank contacts representing the telegraph printer #L The operation from this point on will now be described in detail. As the wipers reach th'e bank contacts #5| the following relays will be in operated position; relays 205, 2|0, 2|5, 235, 260, and all of the off-normal contacts. Should it occur that the telegraph printer #5| be busy and connected for operation by another selector switch of anothertelegraph line the switch Wipers are rotated to the nerr?. set of bank contacts in the same row. Grcun'i, will be connected to the bank contact #5| upon which the wiper corresponding to wiper 293 is resting at the engaged switch. This ground is extended tothe switch at the terminal station to Wiper 293, front contacts 292 of operated relay 280, back contacts 269, through the windingof busy relay 260 to battery.

Relay 260, upon energizing, at its front contacts 262 closes a locking circuit for itself extending through back contacts 253 to grounded front contacts 2 I9. At back contacts 262 a point in the circuit of the upper winding of relay 265 is opened to prevent its energization at this time. After the firstirotary step or subsequent step in case there are more than one, relay 235 will deenergize due to the continued energlzatlon of line relay 205 which opens the circuit of relay 295 at back contacts 201. At front contacts 231 relay 295 upon falling away opens the circuit of relay 280'which slowly falls back and at its front contacts 292 after an interval opens the initial energizing circuit of relay 260. Relay 235 in addition closes its back contacts 230 to close a. circuit for relay 245 vextending from battery through the winding of. this relay, back contacts.

204 of rotary magnet 209, back contacts 220, front contacts 26|, front contacts 26| before re lay 290 has completely restored due to its slow action, wiper 292 and 292 and the bank contacts #5| upon which they have been set and which are strappedtogether at this point, to ground connected through.v the multiple bank 'contact of the other switch which is in engagement with the same contacts.- Relay r245 "upon energizing in the above circuit, closes its contacts 246 to close a locking circuit -fo'r itself extending to grounded front contacts 2I8, independent of the aforesaidl 284 before thisrelay has A fully restored. At front contacts 224 relay 245 closes the circuit from the grounded front contacts 2 I8 to the rotary magnet 209. The rotary magnet upon operating rotates the wipers 290 to 293 one.'rotary step into conl0 nection with the next set of bank contacts connected to telegraph printer #52. As soon as .the rotary magnet 209 energizes it opens its back contacts A204, thereby vopening the locking circuit ofrelay 245 which subsequently deenergizes and at its frontcontacts 224 opens the circuit of the rotary magnet 209. At vfront contacts 233 the circuit oi relay 280 is opened and this relay slowly starts to restore its armatures. If the bank contact'#52 encountered by wiper 292 is also in 204 a busy condition, ground from the busy switch will be again connected to Wiper 292 through contacts 28| and 26|, back contacts 238, back contacts 204, to the winding of relay 245. At the front contacts 224 the circuit for rotary magnet 209 is again closedrandA at grounded front contacts 233 the circuit of relay 2801s closed before it has completelyl deenergized. The rotary maghet steps the wipers to the next set of bank contacts #53 and at back contact 294 opens the circuit of relay 245. The foregoing cycle of operations and the interaction between relay 245 and rotary magnet 209 continues as long as busy bank contact sets are encountered by test wiper v292. The selector switch continues to automatically step in a rotary direction'across the bank contacts as long as busy ones are encountered by the wipers, and if all of the printing mechanisms are busy the wipers rotate until the last one of the group is reached. It will be noted that the test bank contacts of the last group are not connected together while all the others are.

Printers all busy 'When-wipers 290 to 293 oi' the selector switch reach the last set of bank contacts and still encounter a busy printing mechanism and the particular bank contacts are not connected together, the wipers 292 and 293'will not havev a circuit closed betweenthem through the contacts. Un-

lder this condition wiper 292 will no longer be 1 grounded from the busy bank contact on which Wiper 292 is now resting. The grounded bank upon which the wiper 293 is resting, however, will maintain relay 280 operated through front contacts 282, relay 280 still being energized. Relay Il:225 no longer receives an energizing circuit from .wiper 292 and it restores its armatures. At

' i 'grounded front contacts 23s the locking circuit 'for relay 220 is opened. At front contacts 263 irelay 260 prepares the circuit for slow-to-energize "and at grounded back contacts 293 closes the circuit to relay 215 by way of front contacts 263 and the resistance to battery, while at the alter- 4nate contacts 292 it closes a point in the lockingv circuit for relay 260 by way of back contacts 79 259 and front contacts 262 to grounded frontv vcontacts 2|8. At back contacts 264 a point in the locking circuit of relay 265 is opened.

Busy Vindication 75 Relay 215 upon energizing closes its groundedI front contacts 211 and thereby short circuits itself so that after a time due to its slcw acting characteristic it restores. As soon as contacts 211 are opened the relay again` energizes, and thereafter operates continuously in the manner.

. of a buzzer as long as contacts 283 are closed and under control of relay 200. At the back contacts 216 relay 215 opens a point in the telegraphl line |00 each time it energizes, and these inter- ,ruptions in the line continue until the release of the connection by the calling operator-is effected. As a result of these interruptions in .the

`line circuit all of-the supervisoryy lamps at all the stationarwhich have not been selected including 4the calling station, are intermittently iashed due to the fact that the associated line relays such as 205 are alternately energized and deenergized. The lamps of the'other selected stations, in case there areI any, are not flashed because they are litsteadily due to the energizationA of their cut-through relays such' as 60 at way Ystation #8L The interruptions are fast enough so as not to release the switches or permit the relays such as, I0 to restore. This serves as an indication that all of the printers in the group are in a busy condition and not" available for the reception of messages. The release of the connection stops the busy flash as will be subsequently described.

Encountering an idle printer In the event that the wipers 290 to 293 encounter a printer mechanism which is idle and not engaged by a selector of another line, grounol is no longer encountered by wiper 293. Relay 2&5 can therefore no longer energize over this wiper and upon restoring opens its grounded front contacts 233 to open the circuit oi" relay n ing ctases at the back contacts 252 a point in lthe circuit to the upperv Winding of relay 205 which is completed at back contacts 292. As a result relay 265 is energized through its upper winding from grounded front contacts 2id, back contacts 253, back contacts 262, upper winding of relay 265, back contacts 202, wiper 293, bank contact #5| upon which it is now resting, the winding of motor-start relay 296 to battery. At the front contacts of this relay the motor of the printer mechanism #5l commences to operate. As soon as relay 285 completely energizes it closes its locking front contacts 219 by way of back contacts 262 (as soon as relay 260 falls back), 252, 231, to the grounded off-normal contacts 228. At front contacts 268 the upper winding oi relay 265' is disconnected from its energizing circuit in order to remove the resistance of this winding from the circuit oi the motor-start relay 296'. l

As a further result of the energization of relay 265 it opens its back contact 212 to open a point in the circuit of relay 2m. At its back contacts 269 its opens a further point in the circuit for relay 2th.A At its front contacts 253 relayv 260 opens the circuit of relay 215, while at front contacts 262 a further point in its locking circuit is'opened. At front contacts 213' and 21H the telegraph line is switched directly in series with the wipers 290 and 29| and bank contacts #5i upon Which they are resting and which are'connected with the printing mechanism #5L At back contacts 26E the telegraph line circuit is opened for a period of time initiating the answerback indication to signal the calling station that an idle printing mechanism has .been selected. As a result of the opening of the line circuit by the contacts 266 the line relay 205 restores and at grounded back contacts 206 grounds the lamp L3 toilluminate the same and indicate that this station has cut through on a printer mechanism. Relay 210 having its energizing circuit opened by relay 265 at back contacts 212 eventually restores its back contacts 21| thereby completing a circuit through freni-.contacts 216 to relay 225. Relay 225 at iront contacts 226 removes the short circuit from relay 230 and closes its energizing circuit, Relay 230 upon energizing at front contacts 232 short circuits relay 225 and at front contacts 231 closes the circuit through back contacts 226 for the stepping magnet 248 of the switch. S2. The interaction of relays 225 and 230 continues alternately with the stepping magnet taking one step each time, resulting in the moving of wiper 249 onto its rstbank. contact and the closing of a circuit through front contacts 261 for relay 255. Relay 255, upon energizing, at its grounded front contacts 251 closes a locking circuit for itself; at grounded front contacts 259 closes a further circuit for the lamp L3; and at front contacts 239 prepares a further point in the circuit of relay 210 which will energize as soon as" the line relay 205 again energizes. At front contact 256 the answer-back period isA terminated by short circuiting the contacts 266 and the'line circuit is again closed so that the line relay 205 is reenergized. Relay 210, upon energizing, halts the operation of relays 225 and 230 to stop further operation o the stepping switch S2.

contacts 243, the operated off-normal springs 244 and the release magnet 241 of switch S2, resulting in the release of this switch. The answerback supervision results in the operation of the supervisory lamp in accordance with a flash at the calling station to indicate that an idle printer has been selected and that the sending of telegraphic messages between that station and the printing mechanism #51 at the terminal station can take place. In case it is necessary to perform any transmitting of messages from the terminal station to the sending station 'the transmitter illustrated'at the station #32 may be utilized by operating the motor-start key locally to start the motor` at this location.

Release of terminal station apparatus The release of the established connection may take place by the operator at any station. If it occurs at the sending station #61 the operator presses the release key 54 momentarily resulting in the energlzaticn and locking up of relay 50 which atits back contact 51 opens a point in the telegraph line. As a result all of the line relays of all of the switches on the line restore their armatures, including line relay 205 of the selective switch at the terminal station. At front contacts 201 the circuit for relay 210 which Aat this time extends through front contacts 239 is opened. Relay 210 therebycontrols the circuit of relays 225 and 230 to operate the switch S2 in a manner which has been explained to rotate the wiper '249 to the seventh bank contact which is connected to relay 250. Relay 250 upon energizing immediately closes its front con tacts 252 to lock itself energized by way of grounded front contacts 218. AIf the selective switch at the terminal station was released di- At front contacts 2li ground is extended through back rectly by the operator the release key at position #32 would have directly operated relay 250 instead of through the medium of the stepping switch .S2. At back contacts 254 the locking circuit of relay 265 is opened and it restores its armatures. At contacts 261 the circuit for locking relay 255 energized is opened and this relay restores and opens the ground connection at its contacts 259 from the lamp L3 which, however, is maintained at back contacts 206 of line relay 205 which is now in deenergized position. The circuit to wipers 290 and 29| is disconnected by the restoration of contacts 213 and 214 and the line circuit is connected straight through. At

the back contacts 266 the line circuit is again closed before front contacts 256 of relay 255 have opened. At back contacts 253 relay 250 disconnects the ground from contacts 218'extending to wiper 293 thereby permitting relay 296 to deenergize and at its grounded front contacts open the circuit for the motor #51, stopping thev operation of the same.

During the foregoing releasing operation the wiper 246` of the switch S2 continues to advance eventually reaching the bank contact #8 connected to one side of the winding of relay 21.5. Ground from wiper 240 thereby short circuits relay 215 and allows it to restore. At front contacts 216 the stepping operation of the switch S2 is halted and at the back contacts a circuit is closed extending through grounded back contacts 211 of relay 210 which at this time is deenergized, through the oil-normal contacts 221 and the winding of release magnet 213 to battery. Magnet 213 upon energizing closes its grounded front contact 214 independent of ground from back contacts 211 until the offnormal lcontacts 221 are opened. Release magnet 213 upon energizing restores the switch to its normal position and withdraws the wipers 280 to 293 from the bank contact sets #51 upon which they have been resting. At front contacts 218 relay 215 opens the locking circuit of relay 256 which has been closed through contacts 252,l

and this relay restores. At back contacts 25| the open point in the telegraph line circuit is closed. An instant before the switch shaft reaches its normal position, the off-normal contacts are open thereby opening the circuit of the release magnet 213. As a result of the reclosing ofthe telegraph line circuit the line relay 205 again energizes and in turn at its front contacts 201 by way of back contacts 212 closes the circuit of relay 210. At front contacts 211 the circuit extending through these contacts and contacts 243 is closed through the oi-normal springs 244 to the release magnet 241 of the stepping switch S2 and this switch is released. The wiper 249 opens lthe off-normal contacts 244 an instant before it reaches its normal position to open a permanent point in the circuit of magnet 241. The mechanism including all of the relays at the terminal station has now been restored to its normal position in readiness for operation by any other station to select .the same and prepare its printing mechanism for opera-- tion. It will be understood that the remainingA switches at all of the way, stations located on the telegraph line 100 are released in the same manner as has been previously described.

Particular attention is called to the facty that the stepping switches at the way stations are operated to their rst bank contact responsive to the initiation of the answer-back signal in order to provide a time interval to subsequently terminate the answer-back indication.l The step- I pingiswitches are likewise operated to their third bank contact when they are not associated with a station whose operator initiates the release in order to effect the release of the associated switch and to insure that each switch opens the line circuit at its location. This provision is made to-take care of the condition whereby one switch may eifect its release and reclose the line circuit before the other switches on the line would have i vtime to fully release. When the iinal release of the switch is to beeffected the stepping switchV is operated to its fifth bank contact resulting in the operation of the relays such as l5 to iinally restore the selective switch at that particular way station to its normal position. The connection.

of the conductors to the aforesaid bank contacts of the stepping switches may be varied in any particular manner desired. That is, the release time may be extended for a longer period so that the wiper 49, for example, at way station -6I, is required to step to the sixth or seventh bank contact before j iinal release is effected. Similarly the answer-back period between the opening of the line conductors at the contacts 66 and the closing againat front contacts 5G may -be varied any amount by moving the con--4 'ductors connected to the rst bank contact to the second, third, or fourth, as the case may be. The period of 4time or the number of steps of bank contacts betweenthe conductor connected to the third lead and the conductor connected to the fthlead, must remain constant, in order that a uniform release action by all of' the switches may be had.

From the foregoing description of the opera- 'tion of the system it' will be understood that a considerable number of variations in the`operation and arrangement of the-way stations and the terminal stations may take place from that described, and it vis therefore desired not to be limited to the exact embodiments illustrated and v described but only to the extent of the appended claims. f v

' for indicating to the calling station that the f What is claimed is:

l. In a telegraph system, a line, a plurality of stations connected to said line, a selecting switch at each station, means at each station for trans- ,mitting impulses over 'said line, means in each switch responsive to said ,impulses for operating the switch to a particular position, a cutthrough relay in each switch, each cut-'through relay being connected to adifferent position of its associated switch from that of the other cut-through relays, means responsive to the operation of said switches to a particular position for operating one of said cut-through relays and for autoxnaticallyl eiecting the release of all of said switches, means for locking the operated cutthrough relay in energized condition independent of therelease'of its associated switch. and means operated cut-through relay has been operated.

2. In a signalling system, aline, switches connected to said line, a cut-through relay and a switching relay in each of said switches, means for simultaneously operating all of said switches over said line, means controlled by the operation of only one of said switches for operating its associated cut-through and switching relays,

means responsive to the operation of said-switchi ing relay for effecting the release of said switches,

means for locking said operated cut-through relay energized independent of the release of the switches, and further means controlled by the operation of said operated switching relay for transmitting an indication over said line that said cut-through relay has been operated.`

. 3. In a signalling system, a line, a switch connected to said line, a cut-through relay, a switching relay, and a stop relay in said switch, means for operating said switch over said line to operate said cut-through and said switching relays, means controlled byv the operation of said switching relay for initiating the transmission of a signal over said line to indicate the operation of said cut-through relay, means responsive to the duration of said signal for operating said stop relay, means controlled by the operation of said stop relay for terminating the transmission of the signal over the line and for effecting the release of said switch, and means for maintaining said cutthrough relay operated independent of the release of said switch.

4. In a telegraph system. a telegraph line, .a

'plurality of telegraph stations on said line, a

selective switch at each oi' said stations connected to said line, a cut-through relay and a y switching relay in each switch, means responsive to the transmission of impulses over. said line from a calling station-for `operating all ofI said switches, means responsive to the operation oi' only one of said switches for operating the associated cut-through and switching reiays, means controlled by the operation of saidfswitching relay for initiating the release of all of said switches and for transmitting a signal over said line'indieating the operation of said operated cut-through relay to said calling'I station, means forl locking said operated cut-through relay operated inde-A pendent of the release of said switch, means responsive to the transmission oi further impulses for reoperating all of said switches, means responsive thereto for reoperating said switching relay to eect theretransmission ofthe signal over said line, and a circuit initially prepared by said operated cut-through relay when. the switch. is operated the` first time and closed when the switch is reoperated for rendering the associated station telegraph apparatus operable.

5. In a signalling system, a line, a switch connected to said line, means for operating said switch over said line, a relayin said switch, means .responsive to the operation of said switch to a l plurality'of telegraph stations each having telegraphic` apparatus, a selective switch at each station connected tosaid line, means for operating all of said selector Aswitches over the line -from a calling station, a relay in each switch,

means responsive to the operation ofonly one oi'` said switches for operating the associated relay and for releasing said switches, means for transmitting a signal overv said line to the. calling station indicating the operation yoi? said operated relay, means for maintaining said operated relayi locked energized when said syl glease, means for reoperating said switches from said calling station and for retransmitting the signal thereto, means for preventing said switches from releasing when reoperated, and a circuit connection closed by said operated relay and the reoperation of its associated switch for rendering the telegraph apparatus ofthe associated station operable over said line.

7. In a signalling system, a signal line, stations on said line, a selective switch at each station connected to said line, means controlled from a calling station over said line for operating all of said selective switches, means operated by only the switch of the called station for recording the call, means responsive to the recording of the call for initiating the transmission of an answerback signal to the calling station to indicate that the call is recorded, a stepping switch in said selective switch-of the called station, and means operated responsive to the initiation of the answer-back signal for operating said stepping switch to terminate said answer-back signal a'fter a time interval. f

8. In a signalling system, a line, a selective switch connected to said line, means for operating said Vswitch over said line, means responsive to the operation of said switch for initiating the transmission of a signal over said line, a stepping switch in said selective switch, means responsive to the transmission of said signal for initiating operation oi said stepping switch, means responsive to the continued operation of said stepping switch for an interval of time for terminating the transmitted signal, and means responsive to the termination of said signal for stopping the operation of said stepping switch.

9. In a signalling system, a line, a selective switch connected to said line, means for operating said switch over said line, means responsive to the operation of said switch for initiatingthe transmission of a signal over saidline, a stepping switch in said selective switch, means responsive to the transmission ,of said signal for initiating operation of said stepping switch, means responsive to the continued operation of said stepping switch for an interval of time for terminating the transmitted signal, means responsive to the termination of said signal for stopping the operation of said stepping switch, and means for varying the time during which said stepping switch is operated in order to provide a signal period o1' any desired length.

10. In a telegraph system, a telegraph line, stations on said line, a selective switch at each station connected to said line, means controlled over said line from a calling station for operating all of said switches on said line, means in only one of said switches for recording said call, m'eans responsive to the recording of said call for initiating the transmission of an answer-back signal over the line to the calling station to indicate the recording, a stepping switch at each station, means responsive to the initiation of said answer-back signal for initiating operation of the stepping switch in said one of said stations, means controlled by the operating stepping switch after it has operated for a time interval for terminating said answer-back signal, and means controlled at any station to initiate the operation of said stepping switch for a time interval to effect the release of said selective switches.

11. In a' signalling system, a line, selective switches connected to said line, means for operating all of said switches, recording means operated by only one of said switches, means at said one switch for initiating the transmission of a signal over said line to lndicate'the'operation of said recording means, a stepping switch associated with eachof said selective switches, means responsive to the initiation of 4said signal for starting and continuing the operation of the one stepping switch associated with said one selective switch, means controlled by said one stepping switch after it has operated to a certain position for terminating the signal transmission, means responsive to the termination of. said signal for releasing said one stepping switch, releasing means in said one selective switch for again starting and continuing the operation of said one stepping switch to a different position, and means controlled by said one stepping switch after it reaches said diilerent position for effecting the release of said one selective switch.

12. In a telegraph system, a telegraph line, a plurality of stations each having telegraphic apparatus including an operating motor, a selective switch at each-station connected to the line, means controlled from any calling station over the line for operating all of said selective switches, means in' only one of said switches for recording the call and closing a point in the operating circuit of the telegraph motor at that station, means responsive to said selection for transmitting an answer-back signal to the calling station to in-v dicate that the proper selection has been made, means in said selected switch for automatically eiecting the release of said selected switch and all of said other switches, means controlled from the calling station for reoperating all of said switches and for preventing their automatic release, means in the switch `at the selected station for completing the circuit of said selected telegraph motor to operate the same, means responsive to the reoperation of said selected station switch for again transmitting the answer-back signal to the calling station to indicate that the motor of the called station is operating, means at either the calling or called stations for directly releasing the switches at the associated stations, and means controlled by the switch at which the .release is effected for releasing all said other switches on the line. l

13. In a signalling system, a normally closed line circuit, signalling stations on said line, a selective switch at each station connected to said line, each switch normally having battery potential disconnected therefrom so it cannot operate, means'at a calling one of said stations for openi'ng saidline circuit prior to the'ixiitiation of a call over said line, means in each switch responsive to the opening of the line for connecting battery potential to the switch,` means controlled,

over the line from the calling station for operating all of said switches and eiectlng the selection of the switches for disconnecting the battery poy tential therefrom. A

14. Inra signalling system anormally closed line circuit, signalling` stations on said line, a

selective switch at-'each station connected to said line, each switch normally characterized by an absence of battery potential therefrom, a source of alternating current at each station, rectiiying means at each station for converting said alternating current to direct current to render the associated switch operable, means at a calling one of said stations for transmitting a control over said line to said switch, means in each switch retion,

vselected single station operable.

fying meansto said alternating current source to render said switchoperable, and means controlled over said line from said calling station foroperating all of said switches to'eifect' a selec- .tion of only one of said stations and establish a signalling path thereto over saidline, means at any station on the line for effecting the release` of said switches, and meansresponsive to the release of saidv switches for disconnecting ysaid rectifying means from said alternating current means. v'

15. In a signalling system, a selective switch, a group ofl signal stations accessible to said switch, a single Astation also accessible to said switch, means for operating said switch to select one of said group of stations, means for maintaining said switch in connection with said selected group stameans for -operatingsaid switch to select said single station and prepare it for operation, means responsive to said selection for automatically releasing said switch, and means for r'eoperating said switch to a position rendering said 16. In a telegraph system, a telegraph line, telegraph stations on said line including a terminal station, a switch at each of said stations connected to said line, a group of telegraph apparatus accessible to the switch at said terminal station, and a single apparatus at each of said other stations, means controlled from a calling station over the line for operating all oi said switches including said terminal station switch and for automatically selecting one of said group of telegraph apparatus, means for releasing all of said switches except said terminal switclnmeans controlled from a calling station for operating all of said switches including said terminal switch to` prepare the telegraph apparatus at a called station other than said terminal station for operation, means for releasing all of said switches includingsaid terminal switch, and means for reoperating all of said switches including said terminal switch to render the selected telegraph apparatus at the called station operable.

17. In a telegraph system, a telegraph line, stations on said line including aterminal station,ase lective switch at each station connected to saidline, telegraph apparatus at each station connected to the line, means controlled from a calling station over the linefor'operating all of'said switches to select the telegraph apparatus at only one of said stations, means' responsive -to said selection for transmitting an answer-back vsignal over the line from the selected station to the calling station to indicate the selection, means for automatically releasing said switches at the en d oi the signal, further means controlled from the calling station for reoperatlng said switches and rendering the telegraph apparatus at the called station operable, means for again transmitting the answerback signalto the calling station to indicate that the telegraph apparatus is in operable condition,

a plurality of telegraph apparatus accessible to said terminal' station switch, means controlled from a calling station for operating all-of said 4 station switches including said terminal switch,- .means in said terminal switch for automatically selecting an idle one of said telegraph apparatus thereat, means for releasing all of said-switches while maintaining said terminal switch operated, and means operable in case all of the telegraph apparatus at the terminal station is in a busy condition 'for said line to-the calling station.

said switches to select current source therefrom.

` tion,

relay,"

transmitting a busy-flash signal over line, -a selective switch at each of certain of said stations connected to said line, telegraph apparatus at each of said stations, some of said stations being provided with a single set of telegraph apparatus selectable by its associated switch, other stations beingprovided with a single set of telegraph apparatus, a selective switch common to two or more of said other stations, at least one other station being provided with a' group of telegraph apparatus, means controlled by any station over said line for `operating all of only the called station, means responsive to said -selection for transmitting an answer-back signal over the-line tothe callingstation, means for repeatedly reoperating said switches to select the telegraph apparatus at other stations, and means controlled from the calling stations -for finally reoperating all of said switches after all of said selections have been made to-render the selected telegraph apparatus operableover the line. y

19. In a telegraph system, a normally closed line circuit, stations on said line each having ah selective switch associated" therewith, a current source at each station normally disconnected the telegraph apparatus at from said switch, means controlled from a callingv station for interrupting said' line circuit, and means at each station responsive to the line interruption for connecting the current source to the associated switch.

20. In a telegraph system, .a normally closed line' circuit, stations on said line, a selective4 switch at each station connected to.v said line,l a current source at each station normally-discona calling lstation for momentarily opening saidi nected from said switch, means controlled from line circuit, means in each switch responsive to the line opening for connecting the current source to the switch to render the switch operable, and means at the calling station for transmitting calling impulses over said line circuit to. operate all ofsaid switches but which render only the called 'station operable for telegraphic communication. i

21. In a telegraph system, a normally closed line circuit, stations each having a selective switch connected to said line, a current source normally disconnected from each switch rendering it inoperative, a key at each station, means responsive to the operation of said key at a calling station for momentarily opening said' line circuit, means responsive to said line circuit opening for connecting the current source to each switch to render it operable, means at the calling station for operating said switches to select thelcalled station for operation to establish a telegraphic communication path between the calling and called stations, and means responsive to the reoperation of said key for releasing all of said switches and for disconnecting said 22. In a telegraphv system, a line circuit, a pluralityof stations each having a selective switch connected to said line, a release vkey at each staa release relay in eachswitch controlled by said key for opening said line circuit, a stepping switch in each switch also controlling said release line circuit, and means in each of the other operated switches responsive to the opening of the line circuit for operating said stepping switch 23. In a telegraph system, a line, a plurality of stations each having a selective switch connected to said line, means at a calling one of said stations for operating all of said switches to eiect a telegraphic communication path with only the called one of said stations, means responsive to the connection of the4 called station to the line for transmitting an answer-back signal to the calling station, a stepping switch at the called station, means responsive to the initiation of the answer-back signal for initiating operation of said stepping switch, and means controlled by the stepping switch after it has operated for a period of time for terminating said answer-back signal.

24. In a telegraph system as claimed in claim 23 in which means are provided in the stepping switch 'for varying the time period for which the answer-back signal is terminated.

25. In a telegraph system, a line, a pluralityA of stations each having a selective switch connected to said line, means at a calling one of said stations for operating all of said switches to effect a telegraph communication path with only a called one of said stations, means responsive to the connection of the called station to the line `stepping switch after its operation for a period of time for terminating the answer-back signal,

a'release key at the stations for terminating the connections, and means responsive to the operation o! the release key at the calling station for starting the stepping switch to operate for a -period of time to eiect the release of the associated switch.

26. In a. telegraph system as claimed in claim 25 in which vsaid stepping switch includes a plurality of bank contacts and connections thereto, said connections to said contacts being changeable to adjust the period of time for which the mon to all of them, means controlled by a calling station for repeatedly operating said individual switches selectively to render at least certhain of their associated stations operable for telegraphic communication, and means for repeatedly operating said common switch to render its associated stations operable one at aftime.

28. In a`telegraph system, a line', a terminal station on said line including a. plurality of sets of telegraph apparatus, other stations on said line individually including one set of telegraph apparatus, means operative from a calling one of said stations for partially conditioning for operation ,the telegraph apparatus at at least one of said other stations, means operative from said calling station for completelyconditioning `one of said plurality of sets of apparatus for operation, and means operative from said calling station for completing theconditioning for operation of the partially conditioned set or sets of apparatus following the complete conditioning for voperation o1 said one of said plurality of sets of apparatus.

29. In a telegraph system, a plurality of lines, a terminal station common to said lines, said station including a plurality ,of sets of telegraph apparatus each adapted to be associated with any one of said lines for operation thereover, other stations on at least one of said lines and individually including one set of telegraph apparatus, means operative from a calling station for partially conditioning for operation the telegraph apparatus at at least one of said other stations, selective means at said terminal station operative from'said calling station for selecting and completely conditioning for operation an idle one of said plurality of sets of apparatus, and means operative from said calling station for completing the conditioning for operation of the partially conditioned set or sets of apparatus following the complete conditioning for operation of said one of said plurality 'of sets of apparatus.

' OSCAR C. LEVY.

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