US2204445A

US2204445A - Centralized traffic controlling system for railroads

Info

Publication number: US2204445A
Application number: US179982A
Authority: US
Inventors: Neil D Preston
Original assignee: General Railway Signal Co
Current assignee: SPX Corp
Priority date: 1936-05-16
Filing date: 1937-12-15
Publication date: 1940-06-11
Anticipated expiration: 1957-06-11

Description

June 11, 1940. N. D. PRESTON CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed May 16, 19156 3 Sheets-Sheet 1 n3 I M Q 1 fill 4'43 9Q mwi n E 3T2 T [Tali I 3 @E m2 e3 INVENTOR Mam Adi m \w\ ll. 1. n .5 1 i H wzfi iis fim m sm 5 EN K mm n v 1d! l../ coEEou 35 m fizu yrmu Pl |l. TI 10mm. n n 5: 8 5 I u u u in MM m .8 Q2 x 5 w 0 9. 350 n N. D. PRESTON June 11, 1940. 2,204,445

czm'm mzsn TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 3 Sheets-Sheet 2 isY vnv d On 20 a: is

Original Filed May 16, 1936 June 11, 940- N. D. PRESTON CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed llay 16, 19:56

3 Sheets-Sheet 3 lll lrllLlll vl f v tions during a short time.

Patented June I l 1 940- I UNITED STATES PATENT oF'F cr.

'CENTRALIZED TRAFFIC CONTROLLING SYSTEM FoRnAILRoADs Neil D. Preston, Rochsten-N. Y., assignor to Gen-' eral Railway Signal Company, Rochester,

Original application May 1 6-, 1936, SerialNo. 80,095, now Patent'No. 2,169,480, dated August Divided and this application Decem berl5, 1937, Serial No. 179,932 10 Claims. (01. 177 -353) has now matured intoPatent No. 2,169,480 dated August'l5, 1939.

In railroad traffic controlling systems the traffic is controlled from acontroloflice usually located at a central point with respect to an outlying field station or a plurality of field stations. The field station or stations are connected to the control-ofiice bymeans of the'communication system. -The location of trains and the condition of the various 'trafiic controlling de-' vices at the outlying field station or stations are indicated to the attendant in the control oilioe. These indications relating to the condition of the trafiic controlling devices and the like are transmitted to the control ofiice by. means 0 the communication system.

The present invention is particularly useful in a system which is called 'upon to carry out a relatively large number of controls and indica-' The present em-' bodiment more particularly relates to a system comprising a control office anda; single station although it will be understood that the invention is not limited to a single station.

The communication system provided intercom nects the control of ice and the field station and it is so organized that complete control and supervision of the various devices-such as the form of: the

- trol oflice to the outlyingfield station. The

three line Wires are referred to in this disclosure. as the A line, .the'C line and the B line. Y The A line and the 0 line in combination are used for the transmission of controls. The B line and the 0 line in combination are used to effect the synchronous stepping of the step-by-step mechanisms in the control officeand at the field station. The B line and the C line in common are also used to, transmit indications from the sta- 1 tion tothe control oflice. Thus the C line is a devices at the field station. Similarly when indications are transmitted the coded impulses common return conductor for the A and B lines and these three line conductors serve to provide two separate and distinct line circuits. Since the system is of the coded duplex type it is operated through cycles during each of which transmission of controls and/or the transmission of indications may occur. .When controls are transmitted the coded impulses makeup code combinations for the operation of the controlling make up code combinations for operating the v indication receiving devices at the control oflice. I

' For the transmission of controls a predetermined numberof' impulses of selected polarities are applied to theA line circuit for operating the apparatus at the field station and the distinctive character (polarity) of these impulses determines the particular controls to be transmitted to the station.

For the transmission ofindications the B line,

circuit is energized with impulses of distinctive character (polaritylias determined by the selective connection of one way devices (rectifiers) in the B line at the station. This selective energization of the B lineis accomplished by the con-- trol ofiice' attempting to energize the B line with a impulse at the beginning-of an impulse period, with the station permitting the B line to bethusenergized with a impulse for one indication condition and preventing the B line being energized with a impulse for another indication condition. When the B line is prevented from being energized with a impulse then the office transfers the circuit and energizes the B line with a impulse.-

It will thus be seen that the B line is energized for each impulse period and this energization, irrespective of its character, causes the step-byst'ep operation'at the office and at the station. The energization of the B'line with or impulses at-each step of a cycle provides a choice of two 'indications'which are transmitted at each step. Since'the A line is likewise energized with a,(+) or a impulse at each step a choice.

of two control conditions is transmitted at each step" of the cycle. 1

For convenience in .describingthe operation of this system the energized periods of the B line circuit will be referred to as'the on periods and I the deenergized periods of the B-line circuit will be referred to as the oif periods. In the present embodiment the A and B line circuits" arenormally deenergized. At'the start of a control cycle the B lineis energized with a impulse for conditioning the circuits, after which the system steps through the cycle as will be explained in detail. When the system is initiated from the station the B line is energized with a (-1-) impulse for conditioning the circuits of the system, after which the system steps through a cycle as will be explained in detail.

Other objects and advantages of the present invention will be hereinafter set forth in the specification and claims and further details will be understood by referring to the accompanying drawings which illustrate the different methods of carrying out the invention by way of example.

The drawings illustrate in a diagrammatic manner the apparatus and circuits employed and for convenience in describing the invention those parts which have similar features and functions are designated in the different figures oy like reference characters, generally made distinctive by the use of distinctive exponents representative of their location and by the use of suitable preceding numerals representative of the order of their operation and in which:

Fig. 1 illustrates in a schematic manner the line circuit arrangement connecting the control office and the field station of the preferred form, showing only the apparatus most closely associated with the line circuits.

Fig. 2 illustrates in more detail the apparatus and circuit arrangement (of the preferred form) employed at the control oifice for providing means whereby an operator may govern the switches and signals at the field station and whereby indications may be received in the con' trol office from the field station. a

Fig. 3 illustrates the apparatus and circuit arrangements somewhat in detail (of the preferred form) as employed at the field station for providing control of a single track switch and for transmitting indications to the control ofice in accordance with the present invention.

Fig. 4 illustrates the circuits for controlling the stepping relays of Figs. 2 and 3.

When tracing the detailed circuits ofthe preferred form, Fig. 3 should be placed to the right of Fig. 2 with correspondingly numbered lines in alinement.

For the purpose of simplifying the illustrations and facilitating inthe explanation, various parts and circuits have been diagrammatically shown and certain conventional illustrations have been employed. The drawings have been made more with the purpose of making it easy to understand the operation of the invention than with the idea of illustrating the specific construction and arrangement that would preferably be employed in practice.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of current and the circuits with which these symbols are used have current flowing in the same di rection, that is, from to The symbols (13+) and (B) are employed to indicate the positive and negative terminals respectively of a suitable battery or other source of current having a mid-tap (CN) and the circuits with which these symbols are used may have current flowing in one direction or the other depending upon whether the terminal (33+) or (B-) is used in combination with tap (CN).

Control office equipment, preferred forum-The control ofiice (see Fig. 2) includes a control machine having a group of control levers for controlling apparatus at the field station, a miniature track layout corresponding to the track layout at the station and various indicating lamps or equivalent devices, together with apparatus and circuits to accomplish the desired operation of the system.

The apparatus for a single track switch at the field station comprises a switch machine control lever SML, a self restoring starting button SB, a

miniature track switch is and a track occupancy indicating lamp OS. It will be understood that one or more additional switch machine levers may be pnvided if aplurality of track switches are located at the field station. It will also be understood that the single starting button SB is used irrespective of the number of control levers provided.

Similarly, one or more signal control levers are provided but for convenience only a single signal control lever SGL has been illustrated, since the control of the circuits by additional levers may readily be understood after an explanation of the control by the lovers illustrated.

The control office includes a control line relay CF of the neutral quick acting type. A stepping line relay lSF of the biased-to-neutral polar type is provided for controlling the stepping operation and for receiving the indications at the control ofiice. A second stepping line relay ZSF is provided for controlling the operation of an extra impulse relay PX, the purpose of which will be described in detail. Relay ISF controls a line repeating relay FP which repeats the energization of relay lSF irrespective of the polarity oi energization of the 13 line circuit. A slow acting line repeating relay SA is controlled by relay F]? to mark the bounds of a cycle of operations, that is, relay SA is picked up at the beginning of a cycle, remains picked up during the impulses of a cycle and is dropped at the end of the cycle after a predetermined period of time has been measured off following the last impulse.

Associated with the line repeating relays is a bank of stepping relays including relays VP, IV and 2V. This bank of relays is for the purpose of marking oh the successive steps of each cycle, since the particular circuit arrangement for the stepping relays is immaterial for an understanding of the present invention, this circuit arrangement is not shown in Figs. 2 and 3 but only indicated by the dotted line connecting front contact 2% of relay SA with the relays VP, iv and 2V. The control circuits for these relays VP, IV

and 2V havebeen shown in Fig. l, but for the detailed operation of the stepping relay bank reference is made to Fig. 2 of the parent Patent No. 2,169,480 granted August 15, 1939. Referring to Fig. 4 the impulses of each cycle cause intermittent energization of the line repeater relay FP. The initial picking up of this relay FP causes the slow acting relay 3A to be picked up as is evident from the control circuits of relays SA shown in Figs. 2 and 3. With the relay SA now in its attracted condition and with the relay FP energize'd a pick-up circuit is closed for the half-step relay VP which starts from the terminal of a battery and includes the front contact l30 of the relay SA, the front contact l3! of the relay FP, back contact I32 of the stepping relay 2V, back contact I33 of the stepping relay IV,

through the winding of the relay VP to the other terminal of a battery. As soon as the relay VP assumes its energized position a stick circuit for this relay including the front contact I30 of relay SA and the stick contact I34 of the relay V? is closed. With the relay VP now energized and the relay deenergized during'the n t v fi cation'receiving relays the control of indicating period of the B line a pick-up circuit for the first stepping relay IV is closed which may be traced as follows: beginning at the terminal front contact I35 of the relay SA, back contact I36 of the relay PP, front contact I3! of the relay VP, back contact I38 of the relay 2V, through the winding of the relay IV to the terminal With the firststepping relay IV picked up it will be stuck up through a stick circuit including front contact I40 of relay SA and stick contact I4I of relay IV. Also, with the relay FP now deenergized a second stick circuit for the relay V1? is closed which includes the front contact I of therelay SA,,the back contact I 3| of the relay FF and the stick contact I42 of the relay VP. The first traced stick circuit for the relay VP is, of course, broken when the first stepping relay IV is picked up. Picking up of the relay FPduring. the second impulse. of the cycle causes the second traced stick circuit for the relay VP to be broken thereby causing-deenergization of the relay VP there being no available pick-up circuit for this relay VP with the relay IV energized and the relay 2Vdeenergized. During the second deenergization of the B line and ,deenergization of the relay FP a pick-up circuit forthe relay 2V is closed which may be'traced through the front contact I of relay SA, the back contact I36 of steps of the cycle as selected bythe operation of relay FP, back contact I31 of relay VP, the front contact M3 of relay IV, to the winding of the relay 2V. With this relay 2V once energized it is stuck up through a stick circuit including the front contact I40 of relay SA and the stick contact I45 of stepping relay 2V. In the same mannerpas just described for stepping relays IV and 2V any number of stepping relays may be successively picked up one during each deenergization of the intermittently closed B line, of the system. Atgthe end of an-operating cycle the slow dropping relay SA will of course assume its deenergized position'thereby breaking all of the pick-up and stick circuits for'the stepping relays V and also breaking all of the control circuits for the relay VP.

An impulse controlling relay E is controlled by the stepping relays, this impulse controlling relay operating to connect and disconnectcurrent' to the A and B line circuits during the on and offf periods. The A line circuit is energized with a impulse from line battery LB when positive polarity controlling relay PC is' picked up and with a impulsewhen negative polarity controlling relay NC is picked up. This polarity' of 'energizati'o'nis determined during the 01f periods'while impulse relay E is energized, after which the Aline is energized with a selected polarity when relay E drops to mark the end of the off periods.

Indication receiving relays IIR and 21R are provided to receive the indicationwhich is transmitted from the field station at the particular the stepping relay bank in the I control 'oflice. These relays are of the polar magnetic stick type,

that is, their contacts remain in the positions to which they were last actuated until shifted by the'energization of their windings with an impulse of opposite polarity. .Relay IIR. receives I the indication asto whether or not the track sec tion at the field station is occupied and indicates this condition by energizing or deenergizing lamp OS. Relay 2IR. rnay receive any other in-, .clication required, but: since the operation of rey 13 s typical of the operation of other .indi-' trains. A

devicesby relay HR is not shown.

- Field station equipment, preferred form-The neldstation (see'Fig. 3) comprises a turnout track connected to a main track by means of a track switch TS. This track switch is .operated from one extreme locked position to the other byasuitable switch machine SM. The switch machine is controlled by aswitch machine controlrelay SMR of the two-position polar magnetic stick type which is governed from the control office through the medium of the communication system herein disclosed. Relay'SMR controls the operation of the switch machine by energizing its normalor reverse operating wires from a local source of current as controlled by This control preferably includes contact I00. suitable approach locking and other automatic signalling means as usually employed but not shown in the present disclosure for the sake of simplicity.

Suitable signals are associated with track switch TSfor governing traffic thereover. These signals are also governed from the control orfice through the medium of the communication system in any suitable way by means of control relays, such as relay SGR, operated from the control ofiice'in a similar manner as the switch machine contrcl relay 'SMR. The detailed circuit arrangement of the signal control at the field station has been omitted from the present 'disclosure since it is immaterial for an understand ing of the present invention.

The detector tracksection has a normally closed track circuit with the usual track battery and track relay 'Ifor'indicatin'g the passage of since the detailed circuit, arrangement for "operating these relays is immaterial for an understanding of the present invention their control has merely been indicated by the dotted line extending from front contact I20 of relay SA to the stepping relays.

A change relay CH is provided to register a change in condition of any of the traific controlling devices at the station so that the system will be initiated for the'transmission of new indications. The detailed 'control'of this relay has not been shown since it is well known in the art how such a relay is made responsive to a change in condition of 'traffic controlling devices and resensitifzed during the succeeding cycle of operations so that it may respond'to the next change. This change relay CH maybe controlled in the same manner as the change relay of Patent No.

2,082,543 to Judge is controlled. The front conta'ctof the lock relay will of course be omitted fromthe pick-up circuit in, a system where :no

lock-out relay'is employed, as is trueof the system of the instant application. Impulse relay PL is provided for selectively connecting rectifiers IRF and ZRF to the B line conductor-as determined'by thecondition of thetrafiic controlling devices, which .arelto transmit these conditions III to the control ofilce by means of indications. It will be understood that these rectifiers may be of any approved type for permitting current to flow through each one in only one direction, such as the Well known copper-oxide rectifier.

For the purpose of indicating how the two different indication conditions are transmitted by the energization or the deenergization of relay PL, relay M is shown with its back contact ml closed and rela T is shown with its back contact H3 open. Relay M may be the usual relay which repeats the condition. of the signals associated with the illustrated track section, this relay being energized when all of the signals are at stop and deenergized when some one of the signals is in its proceed condition.

It is believed that the nature of the invention, its advantages and characteristic features will best be understood with further description being set forth from the standpoint of operation.

Operation The system of the present invention is normally in a condition of rest, from which it may be initiated into a cycle of operations either from the control oflice or from the field station when there are new controls or new indications ready to transmit.

Irrespective of Whether a cycle is to be for the transmission or" controls or the transmission of indications, a predetermined number of impulses are placed upon stepping line B to accomplish the step-by-step operation of the stepping relay banks. These impulses are time spaced, that is, they follow each other at definite time intervals.

When a cycle is initiated for the transmission of controls the character of the impulses placed upon A line circuit is determined in accordance with the positions of the control levers in the control ofiice. During such a cycle indications transmitted means of the character of the impulses placed upon the B line circuit, as determined by the positions of the control devices at the field. station as repeated by relays T and M for example,

When a cycle of operations is initiated from the control ofiice a series of indications are transmitted from the station to the office during this-cycle irrespective of whether a change in condition of the control devices has taken place or not. Likewise, when a cycle of operations is initiated from a field station the conditions of the control levers in the office at that time are transmitted. to the field station irrespective of whether the starting button in the control office has been actuated or not. It will thus be seen that the present invention provides for duplex operation of the system, that is, controls and indications are transmitted during a single cycle of operations.

Normal co-nditions.-Although the system may be initiated from the field station, both line circuits are normally deenergized. In order to provide a means for initiating the system from the field station the normally deenergized B line circuit is energized in response to the dropping of change relay CH Change relay CH is in its normally energized condition as previously mentioned and track relay T is normally energized when the associated track section is unoccupied. The remaining circuits of the system both at the field station and at the control office are nor-. mally deenergized.

M cmual start-With the system in a condition of rest it may be manually initiated into a cycle for the transmission of controls. Whenever such a cycle is desired the operator first positions the control levers and then actuates the starting button.

For the purpose of considering the operation of the present system it will be assumed that lever SML is in its right hand normal position and that lever SGL is in its center stop position. The actuation of starting button SB closes a circuit for picking up relay PX which extends from back contact 23 of relay E, back contact 22 of relay iV, contact ll of button SB and winding of relay PX, to

The picking up of relay PX closes a circuit for energizing the 13 line circuit with a potential and the C line conductor with a (-1-) potential. This circuit extends from (-1-) at the midtap C of battery LB in the control office, back contact 22 of relay E, C line conductor I3, rectifier ZRF, back contact E82 of relay PL, winding of relay SE, 75 line conductor 14, windings of relays ISF and ZSF in series and front contact I5 of relay PX to the terminal of battery L3. The A line circuit is deenergized at this time since both relays PC and NC are deenergized.

Relays lSF, ESF and SP are picked up by means of current flowing over this circuit, with relay lSF positioning its polar contacts to the left. A circuit is now closed for picking up relay PP which extends from contact it of relay $516 in its left hand dotted position and winding of relay FP to Relay SA is energized over a circuit extending from front contact ll of relay Fl? and winding of relay SA to The energization of relays F? and SA effect the picking up of relay VP over a circuit including front contact Hill of the relay SA, front contact ll of relay and contacts of the steppingrelays (see Fig. 4:). The operation of relays VP, IV and 2V will be pointed out at the times when these relays shift their positions. The stepping relays are energized during the oil periods and the VP relay is shifted during the on periods, which is the operation desired and assumed in the present embodiment. It should be understood that relays corresponding to the relays shown in Fig. 4 are employed at the field station and these relays operate in synchronism with those in the control office.

The picking up of relay VP closes a circuit for picking up relay E which extends from back contact 58 of relay 2V, back contact I9 of relay lV, front contact 2! of relay VP and winding of relay E to It will thus be seen that the picking up of relay PX marks the beginning of what may be conveniently termed the conditioning on period by energizing the B line circuit. The operation of relays SF lSF, ZSF, FP, SA, VP and E takes place during this conditioning period. I

The picking up of relay E marks the end of the conditioning on period and the beginning of the first off period by deenergizing the above traced 13 line circuit at back contact 12. The picking up of relay E opens the circuit of relay PX at contact 23 which allows this relay to drop.

The deenergization of the B line circuit effects the dropping of relays iSF, ZSF and SF. Relay FF is decnergized by the shifting of contact Hi of relay ISF to its neutral position. This effects the picking up of relay !V which in turn drops relay E by opening the above described circuit at back contact 19. The picking up of relay IV closes the selecting circuit of the PC and NC relays and since lever SML is in its right hand pdsit ionvtliis circuit includes relay PC and extends from back contact 24 of relay 2V, front contact 25 of relay IV, contact of lever SML in its right hand position, PC bus and winding of relay PC, to It will be obvious that relay NC would be energized with the contact of lever JSML in its left hand dotted (reverse) position. 7

The A line conductor 33 is now energized with potential over a circuit extending from the terminal of battery LB, front contact 26 of relay PC, back contact 36 of relay NC, winding of relay CF, A line conductor 33, winding of relay CF C line conductor [3 and back contact I2 of relay E to the mid-tap of battery LB. Current flowing over this circuit energizes relays CF and C5, the latter positioning its polar contacts to the'right' A circuit is now closed for picking up relay'PX which extends from front contact 21 of relayCF, back contact 28 of relay 281 and winding of relay PX to Relay PX closes a stick circuit for itself extending from front contact 21 of relay CF, back contact 29 of relay E, front contact 39 and winding of relay PX to I The energization of relay PX applies po- .tential to the B linecircuit'at its front contact [5, as previously described,l.and since the terminal of battery LB is connected to the A line at front contact 26 of relay-PC, current flows over these two lines in series with the C line conductor l3 occupying thelneutral branch of the circuit so that this latter conductor may or may not be deenergized, as determined by the resistance values of the A and B line circuits. The energization of the B line circuit from the terminal of battery LB effects the picking up of relay 2S1 and the positioning of the contacts of relay ISF to the left. Relay SE at the station is picked up. The closure of contact l6 of relay ISF in its left hand dotted position again picks up-relay FP, which effects the deenergization of relay VP.

A circuit is now closed for picking up relay E which extends from back contact l8 of energizing the A and B line circuits by opening front contact l5. It will be'observed that the terminal of battery LBvis connected to the B line'conductor through back contact l5 of relay PX and to the A line conductor through'front contact 26 of relay PC, with the C line conductor open at back contact 52 so that there is no circuit for energizing either line circuit at this contact 24 of relay 2V.; Since it is assumed that lever SGL is in its mid position a circuit is closed for immediately reenergizing'relay PC which extends from front contact 24 of relay 2V, lever SGL'in its mid position, PC bus and winding of relayPC .to The picking up o-frelay tions.

the dropping of-relays ISF, ZS F'and SE 2V deenergizes theabove describedcircuit of relay E at back contact l8. The dropping :of relay E marks the end.- of the 1 second .off period and the beginning .of the second .on period by energizing the A line ciredit with a impulse and the B line circuit with a impulse. This change in energization of the B line circuit is due to the fact that relay PL at the stationis energized as will be described in connection. with the transmission of indica- For the present it will be assumed that relay PL is picked up sov that a circuit for-energizing the B line with a impulse may be traced frorn-the (+)"termina1 of battery LB, back contact l5 ,ofrelay PX, windings of relays ZSF and ISF in series, B line conductor l4, winding of relay SE front con-tact I02 of relay PL, rectifier IRF, C line conductor l3 and back contact l2 of relay E to the midtap of battery LB; The A line is energized during this on period;with

a potential over a circuit extending" from the terminal of battery LB, front contact 26 of relay PC, back contact 36 of relay NC, Winding of relay CF,-A line conductor 33, winding of relay CH, C line conductor 13 andback contact 12 of relay E to the midta'p'of battery LB'.

Relays ISR, 23F and SF, are energized over the B line circuit above traced, with relay SF positioning its'polar contactsto the right; at lays CF and C15 are energized over the A line circuit above traced, withrelay CF positioning its polar contact to the right. Relay ISF effects the energization of relayFP as before,-after which relay VP is picked up to energize relayE over a circuit extending from front contact- 18 of relay 2V, front contact Z! of relay VP and winding of relay-E to 'The picking up of relay E marks the end of the second on period and the beginning of the change to normal off period, which is of comparatively'long duration because there are no more steps to be', taken.- The A and B line cir-' cuits are deenergized by the picking up of back contact l2 of relay E, it being recalled that the terminal of battery LB is connected to both and A and B line conductors.

The deenergization of the B line circuit effects The shifting of contact 16 of relay ISP to its neutral position deenergizes relay PP and, since there is no circuit effective at this time to deenergize relay E, relay FP remains deenergized, for a sufficiently long period of time to effect the dropping of slow acting relay SA. Relay SA in releasing by the opening of its contacts I30 and ME! deenergizes relays VP, IV and 2V by deenergizing their stick circuits (seeFig. 4).v The restoration of thestepping relay bank to normal deenergizes relay E and the selected polarity control relay (in this instance relay PC). 7 Thedeenergization of the A line circuit causes relays CF and CF to restore tact I03 of relay SE operates relay FP in syn-' chronism'with relay FP in the control oifice.

. Furthermore the intermittent closure of front "contact IM of relay FP energizes relay SA dur- -ing the conditioning on period above described andmaintains this relay in its: picked up position 'during the following impulses of the cycle. Since relay FP jopens its front contact HM for a comparatively long internal ;oftime at the end of the cycle,'relay SA is released at approximately the same time as relay SA in the control cfiice.

It will also be mentioned at this time that relays VP W and 2V are operated in synchronism with corresponding relays in the control office by means of circuits shown in Fig. i of the drawings. These stepping relays are deenergized at the end of the cycle the same as those in the control ofiice.

Polarity selection of control impuZses.When the system is initiated from the control office as above described, the first (conditioning) impulse applied to the B line circuit is in character by reason of the picking up of relay PX. This application of energy to the B line causes various relay operations which have already been described.

Assuming that the switch machine lever is in its right hand (normal) position as shown, the first on impulse applied to the A line circuit is as already described. In the event that lever SML is in its left hand dotted (reverse) position relay NC is energized to apply a impulse to the A line circuit.

This selection of the polarity of energization for the A line circuit occurs on each step by rea son or the selection made at contacts 25 of relay W, 2 of relay 2V, etc. This selectively energizes relay PC or NC in accordance with the particular position of the control lever selected for each step. It will be understood that additional levers for other control purposes may be provided and selected through additional contacts of additional stepping relays when the size of the system requires such extra selection.

From the above it will be seen that the impulse applied to the B line during the conditioning period of a cycle initiated in the control office is with the following impulses applied to the A line circuit being or in character dependent upon the positions or" the control levers rendered efiective by the stepping relays at the various steps of the cycle. This polarity determination is accomplished by two polarity determining relays PC and NC which are selectively energized during the off or deenergized periods of the line circuits in readiness for energizing the control line circuit during succeeding on or energized periods with the proper polarities as selected.

Transmission of controls-Upon the transmission of the first impulse, following the conditioning impulse, relay SMR at the field station is energized for actuating its polar contact me to the right or to the left depending upon the character of the impulse received. With lever SML in its normal position. as shown, the impulse applied to the Aline circuit actuated the contacts of relay CF to the right. A circuit is now closed for actuating the contacts of relay SMR to the right extending from (B+) contact H05 of relay CF in its right hand dotted position, back contact Hi6 of relay 2V front contact Hill of relay H7 and winding of relay SMR to (CN) This energization of relay SMR closes contact H35? in its right hand position for applying energy to the normal operating winding of switch machine SM for operating the track switch to its normal locked position.

In the event that lever SML is in its left hand (reverse) position the impulse applied to the A line circuit actuates contact it? of relay CF to the left, which applies (B-) to the circuit above described including relay SMR. This positions contact illt to the left for applying energy to the reverse operating winding of switch machine SM which operates the track switch to its reverse locked position.

in a similar manner lever SGL in its neutral position causes relay PC to be picked up for applying a impulse to the A line circuit when the second step is taken, which actuates contact Hi5 of relay CF' to the right for applying (B+) to the winding of relay .SGR over a circuit including front contact m5 of relay 2V It is believed unnecessary to show or explain the detailed operation of the circuits controlled by relay SGR since they form no part of the present invention.

Field start.This system is of the coded duplex type and indications are transmitted from the station to the control oilice during the same cycle that controls are transmitted to the station.

Referring to Fig. 3, a change in the condition of the detector track section or a change in the con dition of other traffic devices at the station may occur at any time and for convenience in describing the operation of this portion of the system it will be assumed that such change effects the deenergization of relay CH The dropping of relay CH closes a circuit for picking up relay PL which extends from back contact 33 of relay SP back contact N2 of relay CH back contact i it of relay 5V back contact N9 of relay 2V and winding of relay PL to Relay PL closes a stick circuit for itself extending from front contact Ht of relay PL, back contact ii! of relay iV back contact N2 of relay CH and over the previously described circuit to the winding of relay PL.

The energization of relay PL causes the B line to be energized with potential over a circuit extending from the terminal of battery LB, back contact E5 of relay PX, windings 0i relays and ESP in series, B line conductor It, winding of relay SP front contact it? of relay PL, rectifier iRF, C line conductor 13 and back contact E2 of relay E to the midtap of battery LB.

This energization of the B line circuit picks up relays 28F, ESP and SP In response to the actuation of contact N3 of relay iSF (to the right in this instance since the 13 line circuit is energized relays PP and SA are energized to initiate the cycle. Relays VP and E are energized as previously described in connection with a control cycle to complete the conditioning on period. The energization of relay E marks the beginning of the first off period and the system steps through its cycle as before.

During the first oil period relay IV is picked up to deenergize, at its back contact Hi, the above described stick circuit for relay PL so that this relay is now made dependent for its energization upon the circuits selected by the stepping relays and controlled by traffic devices such as track relay T and signal repeating relay M. I

ransr-iission of indications.After thus having initiated the system from the field station the controls are transmitted as previously described to actuate the control relays in accordance with the positions of the control levers in the ofiice. During the steps of the cycle indications are transmitted by relay PL selectively governing the energizaticn of the B line cir cult by means of rectifiers iRF and ZRF. For

example, with the track relay energized when the first step is taken, the circuit leading to at back contact i it of relay T is opened so that relay PL will not be picked up. During this off period the dropping of relay E energizes the A line circuit as previously described and since relayPX is deenergized, (+1 potential is applied through its back contact I5 to the B line circuit, but since back contact I02 of relay PL is closed no current can flow through rectifier ZRF over this circuit.

described. The picking up of relay PX applies a impulse to the B line circuit for positioning the contacts of relay ISF to the left which closes a circuit for actuating relay IIR. to the left extending from (B), contact of relay [SF in its left hand dotted position, back contact (ii of relay 2V, front contact 32 ofrelay iV and winding of relay IIR to (CN). With contact 34 of relay IIR in its left hand position, lamp OS is deenergized. In the event that track relay T is deenergized under the above condition, then relay PL is energized and ,relay ISF is actuated 'to the right for positioning relay IIR to the right to close a circuit through contact 34, which energizes'lamp OS to give the indication that the track section is occupied. The

manner in which relay iSF'is positioned to the right will now be explained in connection with the second step of the cycle.

Assuming that. relay M is deenergized, relay PL is energized, when the second step is'taken, over a circuit extending from back contact H of relay M, front contact H9 of relay 2V and winding of relay PL to When relay E is deenergized to mark the beginning of the next on period both the A and B line circuits are energized with potential. The A line' circuit is energized with potential because relay PC is picked up. The B line circuit cannot be energized with potential as before because contact I02 of relay PL disconnects rectifier 2RF from the B line circuit and inserts rectifier [RF which will only permit energization of the B line circuit with a impulse. Therefore the A and B line circuits are simultaneously energized under this condition instead of the A line circuit being energized in advance of the B line circuit as before. This prevents the picking up of relay PX because contact 28 of relay ZSF is opened by the time front contact 21 of relay CF is closed. With relay PX deenergized the B line circuit continues to be, energized from the (+9 terminal of battery LB throughout this "on period. This positions contact 30 of relay ISF to the right for closing a circuit which actuates relay HR to the right and which extends from (3+) contact 30 of relay ISF in its right hand dotted position, front contact 3| of relay 2V and winding of relay ZIR to (CN).

Although the transmission of indications has only been shown for two steps it will be understood that any number of steps may be similarly employed, each step providing for the transmission of a choice of two indications.

During a cycle of operations for the transmission of indications as just described, change relay CH at the station is restored to its picked up position in readiness for any other change that may occur at the field station. The circuit arrangement for accomplishing. this result is not shown since it is immaterial for an understanding of the present invention and since various expedients may be used for such accomplishment.

The change to normal period at the end of the I that control and indication cycles are initiated from the control ofiice and the field station respectively. It has also been mentioned that indications of the existing conditions of the control devices at the station are transmitted. to the ofiice during a-control cycle and controls are transmitted from the ofiice -to the field station in accordance with theexisting conditions of the control levers during an indication cycle. Thus the resulting cycle of operationsinitiated from the control ofiice or from the field station results in two way transmission; or in other words the duplex operation of the system.

- Having thus described a centralized trafiic controlling system as a preferred form, it is desired to be understood that the particular form illustrated was selected to facilitate in the disclosure rather than to limitthe form the invention may assume or its scope and it is "further to be understood that .various modifications, adaptations, and alterations may be applied to the specific form shown to meet the requirements of practice without departing from the spirit of. the invention except as limited by the appended claims.

What I claim is: i 1. In a remote control system, a control ofiice and a field station connected by a line circuit; impulsing means at said office for applying a series of current impulses to said line circuit,

means in said oflice for attempting to mark each of said impulses with one polarity, a first rectifier at said station for preventing said office from markingan impulse with said one polarity,

means in said office responsive to its failure to' mark an impulse with said one polarity for mark ing said impulse with another polarity, asecond rectifier at said station for permitting said office to mark said impulse with said one polarity, and means responsive to the polarity with which said impulse is marked for transmitting a code message from said station'to said oifice.

2. In a remote control system; a control ofiice and a .field station connected by a line circuit;

means including a source of energy for energizing said line circuit withcurrent oi one polarity; impulsing means in said office for intermittently opening and closing said line circuit, whereby a series or time spaced impulses are applied thereto; step-by-step mechanisms in said office and at said station operated in synchronism in response to said impulses; means at said station for preventing the energization of said line circuit 'withcurrent of said one polarity at certain steps of said mechanisms; means in said ofiice responsive to the failure to energize said line circuit with currentof said one polarity for applying current of' another polarity thereto, whereby said line circuit is energized with current of another polarity; and means in said office distinctively responsive to the polarity with which said line circuit is energized, whereby coded messagesrare transmitted from said station to said ofiie. I I 3 3. In a remote control system; a control oflice and a field station connected by a line circuit; means including a source "of energy for energizing said line circuit with'vcurrent of one polarity; impulsing means in said ofiice for intermittently opening and closing said line circuit, whereby a series of time spaced impulses are tip:

plied thereto; step-by-step mechanisms in said oifice and at said station operated in synchronism in response to said impulses; means at said station for permitting or preventing the energization of said line circuit with current of said one polarity at certain steps of said mechanisms; means in said ofiice responsive to the failure to energize said line circuit with current of said one polarity for applying current of another pclarity thereto, whereby said line circuit is energized with current of another polarity; means in said office responsive to the energiaation of said line circuit with current of said one polarity for preventing the application ol' current of said other polarity thereto; and means in said office distinctively responsive to the polarity with which said line circuit is energized, whereby coded messages are transmitted from said staticn to said office.

l. In a remote control system, a control ofiice, a field station, a line circuit connecting said office ith said station, means in said office for applying a series of direct current impulses of par ticular polarity to said line circuit, means at said ofilce for time spacing said impulses, 2. rectifier device at said station for at times blocking the flow of a current impulse in said line cir cuit, means at said ofiice for reversing the polarity of such particular impulse when the polarity of such impulse as originally applied is in disagreement with said rectifier, and indicating means at said control oiflce controlled by the current impulses actually flowing in said lino circuit and in accordance with their polarity.

5. In a remote control system, a control office, a field station, step-bystep mechanisms at said ofiice and at said station, a line circuit connecting said office with said station, means at said office for applying a series of impulses of direct current to said line circuit, means responsive to said series of impulses for operating said mecha nisms in synchronism, means including a rectifier device in said line circuit at said station and electro-respon sive means in said line circuit at said office to characterize the polarities of said impulses to conform with the rectifying direction of said rectifier, and means responsive to the character of said impulses for transmitting messages from said station to said cflice during the synchronous operation of said mechanisms.

6. In a remote control system; a control oflice; a field station; a source of energy at said ofiice; a line circuit connecting said office and said station; a line relay in said circuit at said office; control means for supplying current of one po-- larity from said source to said line circuit; electric valve means included in said line circuit at said field station in a direction in accordance with the message to be transmitted to said office; electro-responsive means controlled by said control means and by said relay for reversing the polarity of current applied at said omce to said line circuit when said control means is operated to apply current to said line circuit and said line relay does not respond thereto by reason of the blocking action of said electric valve means, to thereby cause said relay to respond to such reversing of the current; and indicating means controlled by said linerelay.

'1. In a remote control system, a stepping line circuit having a plurality of series of time-spaced impulses impressed thereon, a step-by-step mechanism operable through a separate cycle for each of said series of impulses, means controlled by said mechanism for selecting a channel circuit for each step, means for causing said mechanism to take one step for each impulse of a series, two oppositely poled rectifiers at the sending station of said system, meansv for selectively connecting said rectifiers only one at one time in said line circuit on each step of said step-bystep mechanism to characterize a code, means at the receiving station for applying current of one polarity to said line circuit on a particular step and if the rectifier then connected in said line circuit does not allow said current of that polarity to flow to cause the application of current of a different polarity to said line circuit,

and indicating devices included in said channel circuits controlled in accordance with the polarity of the current flowing in said line circuit on corresponding steps.

8. In remote control system, a stepping line circuit connecting an office and a field station, means at said office for applying a plurality of series of time-spaced stepping impulses upon said line circuit, a step-by-step mechanism at said office and at said field station operable through a separate cycle for each of said series of stepping impulses, means for causing said mechanisms to take one step for each stepping impulse of a series, asecond line circuit, means for impressing a series of current impulses on said second line circuit one impulse for each step in synchronism with the application of said stepping impulses on said stepping line, means controlled by said mechanisms for selecting a plu rality of channel circuits at least one [or each step, two oppositely poled one way current de vices, means for selectively connecting one or the other of said devices in said stepping line circuit on each step, means controlled by impulses in said second line circuit for reversing the polarity of current in said first line circuit in the event a current impulse flows in said second line circuit before a current impulse fiows in said first line circuit due to the one way current device included in said first line circuit blocking the fiow of current in said first line circuit, and indicating devices controlled over said channel circuits in accordance with the polarity of cur rent flowing in said stepping line circuit.

9. In a remote control system, a first line circuit connecting an on'ice and a field station, a

second line circuit connecting said office and said field station, a line relay in said first line circuit at said ofilce and at said field station, step-bystep mechanism at said office and at said field stations controlled by said line relays, a source of current in said line circuit at said office, means in said office for intermittently closing said line circuits to establish a series of current impulses, rectifier means at said field station included in said first line circuit and normally so poled as to prevent the fiow of current in said first line circuit due to closure of said line circuits at said office, means including a line relay in said sec- 0nd line circuit at said office for pole changing the source of current in said first line circuit if said second line circuit is energized before said first line circuit is energized to cause current to flow through said rectifier means in said first line circuit, means at said field station controlled by the step-by-step mechanism at said field station for including said rectifier means in one rectifying direction or the other in said first line circuit on each step depending on traflic conditions at said station, indicating means at said oiiice, and polar contacts on said line relay in said first line circuit at said oifice for controlling said indicators in accordance with the rectifying direction said rectifying means is included in said first line circuit on each step.

10. In a remote control system, a control ofiice and a field station, a control circuit and a stepping circuit connecting said oflice and field station, line relays in said stepping circuit at said office and at said field station, step-by-step mechanism at said office and at said field station controlled by said line relays, a distinctive current responsive line relay at said field station and a neutral relay at said office included in said 1 control circuit, means including said step-by-step mechanism at said ofiice for applying current impulses of distinctive characters to said control circuit one impulse for each'step'to characterize a code, means controlled by said neutral relay 7 and including a front contact thereof for applying stepping impulses to said stepping line circuit one impulse for each energization of said neutral relay, and controlled means at said field station controlled by said distinctive impulses through the medium of said distinctive current 1 responsive relay at said field station.

, .D. PRESTON,