US2045951A - Centralized traffic controlling system for railroads - Google Patents

Description

Patented June 30, 1936 CENTRALIZED TRAFFIC CONTROLLING SYSTEM Fon RAILROADS Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application June 28, 1933, Serial No. 678,045

14 Claims. (Cl. 246-3) a system with the traffic controlling devices which are supervised thereby. This invention is an improvement over the invention disclosed in'the prior application of Wells Ser; No. 634,370 filed September 22, 1932, and the improvement only is claimed herein. V 1 V V The centralized traific controlling system contemplated by the present invention includes means for establishing communication between a central control ofiice anda large number ofoutlying field stations by means of a station'selective coded type of communication system. Such a communication system usually provides for the transmissionvof a plurality of different series of code combinations which may be transmitted over the line circuits connecting the control office The transmission of any and the field stations. one such series of impulses causes the selection of a particular station and the control of the devices at the station.

The selection of a particular station may be accomplished in any one of a number of difierent Ways by a suitable station selective coded type system, such as shown, for example, in my pending application, Ser. No. 613,353, filed May25, 1932.

However, the present invention more-particularly pertains to themanner in which a selected station responds to. a series of code impulses 'to accomplish the control of the devices at that 3 station.

This is accomplished in the system of the present invention by the provision of control relays for the switches and signals which are positioned on the steps taken by the field station apparatus,

after that station is selected, in accordance with the? character of the code. impulses for the corresponding steps. One difficulty in systems of this character has been to insure that such control receiving relays haverproperly responded to 4-, their corresponding code impulses during the last cycle of operation. This difiiculty-has been overcome in thesystem of the present invention by providing a control receiving relay for each different code character, and that all of these control receiving relays shall be deenergized at the beginning of each cycle of operation in order for them to be rendered subject to the code impulses for that cycle. Thus, as it is possible to receive but one character of impulse for any one step, it

' 5; is obvious that only one control receiving relay tion, suitable means is provided that no control receiving relays may be positioned unless all such relays are in their normal positions at the beginning of the cycle upon which they are to be con'" trolled. I

With such an arrangement of control code receiving apparatus; it is apparent that each de vice 'must have responded by the endof a cycle of operation in order for the control devices to be in' proper positions for setting up a route over the track switch located at a particular field sta-' tion. I

Other'features of the present invention reside in the various circuit arrangements particularly adapted for systems of this character. 'Thesecharacteristic features of the invention thus briefly stated will be explained more in de tailin' the following description of one embodi ment of the invention; and various otherchar-z acteristic features, functions and advantages of a system embodying the'invention will be in part pointed out and in part apparent as the descrip-v tion thereof progresses. I

will be made to the accompanying drawing in which the various parts are designated by suitable reference characters, and in which:-. The single figure illustrates diagrammatically the apparatus and circuits provided inaccorda'nce with the present invention at a typical field station for the control of a single track switch and the signals for governing traflic thereover.

For the purpose of simplifying the illustration and'facilitating in the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been. made more With the purpose of making it easy to understand the principles and mode of operation than I with the idea of illustrating thespecific construcnnec qnsto the terminals of batteries or other sources of current instead of showing all of the wiring connections to these terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current; and the circuits with which these symbols are used, always have current flowing in the same direction. In the event that alternating current is employed instead of direct current, it is to be understood that these symbols and represent the relative instantaneous polarities of such current.

Communication system in general.A centralized trafiic controlling system in which the present invention is more particularly useful, consists of a control office and a large number of outlying field stations. Communication is then established between the control ofiice and the field stations for the transmission of controls to govern the traflic controlling devices at such stations, and for the transmission of indications to give the operator in the control ofiice information as to the location of trains and the response of the various trafiic controlling devices at the stations.

This communication is established over a station selective coded type communication system in which a small number of line wires is employed for the transmission of the controls and indications by means of suitable code combinations of impulses. 7

It is considered unnecessary in the disclosure of the present invention to specifically illustrate the apparatus in the control ofiice for impressing a plurality of series of different code combinations on a line circuit in accordance with the positions of code jumpers and control levers. It is also considered unnecessary to illustrate the entire apparatus of a field station required for assumed that such a communication system may be of any suitable type, such as disclosed, for example, in my pending application Ser. No. 613,353, filed May 25, 1932, above referred to.

The present disclosure more particularly indicates that the application of impulses to a linev circuit causes suitable step-bystep operation at a field station irrespective of the character of those impulses; while the character of the impulses is employed for actuating suitable control receiving devices in a similar manner as disclosed in my above mentioned application. However it is to be understood that those impulses which cause the step-by-step operation may be, if desired, distinct and separate impulses from those that cause the actuation of the respective control receiving devices for the several steps of the system.

With reference to the accompanying drawing, a control office has been indicated by merely a dotted rectangle which is illustrated as connected to a field station by three line wires including a control line wire l2, an indication line wire H, and a common return line wire I0. It is assumed that these three line wires not only extend from the control office to the field station illustrated, but also extend to each of the succeeding field stations of the system. These line wires I0, II and I2 are so connected as to complete two line circuits, namely a control line circuit and an indication line circuit. The control line circuit is provided for the transmission of impulses of selected polarities from the control ofiice and includes at each station a three-position biased-to-neutral polar line relay F. The indication line circuit is employed for the transmission of indications subsequent to the registration of a particular field station in the control ofiice in such a manner that any particular field station may transmit its indications, one station at a time to the control office, all of which has been omitted as an understanding of such operation is unnecessary for an understanding of the present invention.

Field station apparatus.-The dotted rectangle indicated as a field station is assumed to be a complete field station apparatus of which those parts more particularly relating to the present invention have been illustrated in detail in the accompanying drawing.

The field station includes besides its line relay F, a neutral line repeating relay FP of the quick acting type which is energized each time the line relay F isenergized, irrespective of the polarity of such energization, and is deenergized each time the line relay F is deenergized.

A slow acting neutral relay SA is picked up by the first impulse of each series of impulses and is dropped at the end of such series, although it is actually energized only during the successive impulse periods marked off on the control line circuit and repeated by its quick acting line repeating relay FP. This operation is accomplished by reason of the slow acting characteristics provided for the relay SA, so that its contacts remain in picked up positions during the deenergized time spaces which separate the successive energizations or impulses of the control line circuit. The relay SA is preferably slow acting in picking up as well as dropping away, although its drop-away time is relatively much longer than its pick-up time.

The field station includes a station selecting relay ST which is energized or picked up whenever the field station is selected for the reception of controls. Although the control of this relay ST has not been illustrated, it is to be understood that it may be controlled in any suitable manner so as to be responsive to the characters of the impulses of the first part of each code combination applied to the control line circuit, that is, whenever such impulses form the code combination assigned to this field station, this relay ST is picked up prior to the actuation of the stepping relays at this station which operate during the reception of controls, as explained more in detail hereinafter.

Associated with this station selecting relay ST is a repeating relay STA which is provided for certain checking purposes hereinafter explained in detail.

A stepping relay bank is provided at the field station which takes one step for each deenergizecl condition of the control line circuit after the first energization of the line circuit for the first impulse of a code combination. However, only those relays of this bank which operate after the station is selected, have been illustrated, such for example as the stepping relays 3V, 4V and 5V. Although the stepping relays'have been indicated as being picked up during the deenergizcdconditions of the control line circuit, so that the energized condition of the control line circuit may be directly effective to condition a control receiving relay, it is to be understood that these operations may be reversed, if so desired, so that the stepping relays may be actuated during the energized conditions of the control line circuit with the character of suchenergizations stored until the following deenergized conditions, all of which has been disclosed in various preceding patent position to the other by a suitable switch machine SM, which may be of any suitable type known to those skilled in the art.

Associated with the track switch TS and the switch machine SM is preferably a suitable point detector contact mechanism- (not shown) for properly controlling a switch position repeating relay WP. This switch position repeating relay WP is of the polar-neutral type which is'ener gized with one polarity when the track switch TS is in one extreme position and locked and is energized with the opposite. polarity with the track switch TS in its opposite extreme position and locked, but is deenergized whenever the track switch is unlocked or is in operation.

Suitable signals lA-.lB are provided for governing trafiic over the track switch TS in an eastbound direction; while suitable signals ZA-ZB are provided for governing westbound trafiic over the track switch TS. Although these signals have been illustrated as color light signals, they may be of any other suitable type governed in accordance with traffic conditions subject to manual control as provided in accordance with the present invention, which sig'nalsare provided for advising theengineer of a train or automatically governing train control apparatus. v

These signals are normally at-stop but are cleared subject to traflic conditions whenever their corresponding signal control relays [AG-BEG, 2AG2BG are energized. The automatic control has been merely indicated in the drawing by the provision of the home relays IH. and 2H, and it is to be understood that the relay IE is controlled in accordance with trafiic conditions in advance of the signal IA; while the home relay 21-1 is controlled in accordance with trafiic conditions in advance of the signal 2A, all of which has been disclosed in various prior applica-,

tions, such as for example, in the application of S. N. Wight, Ser. No. 120,423, filed July 3, 1926.

The track switch TS also has'associated'therewith the usual closed circuit detector track sec tion having the usual track battery and track.

relay T. A track repeating relay TR of the slow acting type is provided for directly repeating the track'relay T for purposes hereinafter pointed out. i

For the purpose of controlling the operation of the switch machine SM, two switch machine control relays WN and WR of the neutral type are provided. These relays are controlled in accordance with the character of thecontrols received over the communication system and are maintained in their last operated positions until subsequently controlled, all in a manner to be explained in detail hereinafter. The relay -WN causes the normal operation of the. switch machine SM; while the relay WR causes the reverse and WR in such a way that the relay NC is energized whenever the relay WP indicates that the track switch TS isin a normal locked position if the relay WN is picked up; while the relay RC is energized whenever the relay WP indicates that the track switch TS is in a reverse locked position if thecontrol relay WR is picked up.

Thedirection of traffic over the track switch TS is governed by the direction control relays LD and RD, only one of which may be picked up at any one time. The particular route for the direction selected by these relays is determined by the position of the track switch TS in correspondence with the switch control relays WN and WR, as

repeated bythe correspondence relays NC and over the detector track section having the track relay T; while the manual control is embodied in a stop relay S which maybe operated from the control ofiice by theltransmission of suitable code impulses, as later to be explained.

It has been previously mentioned that the present invention contemplates a centralized traffic controlling system in which indications of the positions of the various traiiic controlling devices as well as the location of trains along the trackway are transmitted to the control ofiice, but a disclosure of all such apparatus has been omitted for the sake of simplicity in pointing out the features and functions involved in the disclosure of the present invention.

Various other apparatus and devices for the field station include bus wires, circuit connections, suitable overload devices, terminal blocks and such other devices as may be necessary to be employed in actual practice, the illustration being made more with the idea of disclosing the novel features embodying this invention rather than with the idea of disclosing usual expedients.

, It is believed that othercharacteristic functions and features of the present invention will be best understood by considering various typical operations of the present embodiment.

Operation For the transmission of controls, a plurality of distinctive impulses are applied to the control w bination always have the same number of lin pulses. In other words, the code combinations are made up by alternately energizing and deenergizing the control line circuit with the energizations being one of two opposite polarities. Then each energized period or impulse is conveniently termed an on period, and its following deenergized period or time space is conveniently termed an off period.

The impulses in the first part of each difi'erent series form a combination that may be termed a station code call for the selection of a particular station; while the impulses in the latter part of each different series comprise the controls for that particular station designated by the station code call part of the series. As the station selecting part of the system contemplated by the present invention is of only general interest with respect to an understanding of the present invention, it will be treated generally; while more specific consideration will be given to the control impulses which are received by a station subsequent to its selection by the reception of its station code call.

Normal conditions.As previously mentioned, the detector track section associated with the track switch is of the normally closed track circuit type, so that the track relay T is normally energized, as is readily understood. With the front contact l3 of track relay T closed, an ob vious energizing circuit for its repeating relay TR is closed. It is also to be understood that the red or stop indicators of the signals IAIB and 2A-2B are also energized under normal conditions as all signals normally indicate stop.

As the last operation is assumed to have caused the normal operation of the track switch TS, then the switch control relay WN is energized by a stick circuit closed from through a circuit including back contact M of relay ST, bus wire l5, front contact 16 of relay WN, windings of relay WN, to With the relay WN energized and the track switch TS in a normally locked position as repeated by the relay WP, the normal correspondence relay NC is energized by a circuit closed from through a circuit including front contact ll of relay WP, polar contact I 8 of relay WP in a left hand position, windings of relay NC, front contact IQ of relay WN, to

Other relays of the system, so far as the present disclosure is concerned, are normally deenergized.

Station selection and step-by-step operation. Assuming that a series of impulses of a particular number, which impulses are distinctive by their polarities, is placed upon the control line circuit resulting in a cycle of operation to accomplish the transmission of controls to a selected station, each of the on periods is repeated by the polar line relay F, its polar contact 20 being operated either to a right or a left hand position depending upon Whether the polarity of the energization of the line circuit is positive or negative in character. Irrespective of whether the polar contact 20 is operated to a right hand or a left hand position, each of the energized positions is repeated by the relay F? by reason of circuits obvious from the drawing.

Each time the front contact 2| of relay FF is closed, the relay SA is energized. Inasmuch as the relay SA is slow acting, it is preferable that the first impulse of the series be slightly longer than the rest of the impulses in order to provide the relay SA with sufficient time in which to pick up its contacts. However, once the relay SA has picked up its contacts upon the first impulse, its contacts remain in picked up positions, although the energizing circuit for the relay SA is intermittently opened at front contact 2| of relay FP, as the slowacting characteristics of the relay SA provide that its contacts shall be maintained in picked up positions for periods of time longer than the periods of time marked off by the off periods between the impulses of the series. Thus, the contacts of the relay SA remain picked up until the control line circuit has been deenergized for a predetermined period of time at the end of such series of impulses.

'The pick-up circuits for the stepping relays have been indicated as including back contact 2| of relay FF and front contact 22 of relay SA, which means that the stepping relays may take suitable code receiving means, such as shown in my above mentioned application Ser. No. 613,353, or as shown in the application of W. D. Hailes, Ser. No. 652,177 filed January 17, 1933.

As soon as the relay ST picks up its back contact 14, the stick circuit for the relay WN is opened so that its contacts drop away thereby closing a pick-up circuit for the station repeating relay STA from through a circuit including back contact 48 of relay WN, back contact 43 of relay WR, front contact 36 of relay ST, windings of relay STA, to The relay STA immediately responds closing its stick circuit from through a circuit including front contact 3! of relay STA, front contact 36 of relay ST, windings of relay STA, to This all occurs prior to the fourth impulse.

It has been the practice in some centralized traflic controlling systems to provide that the step-by-step operation shall not continue if the station fails to be selected. If such a feature is provided for the station illustrated in this disclosure, then the stepping relays 3V, 4V and 5V respond respectively to the off periods following the third, fourth and fifth impulses only when the station is selected. Assuming that the station is selected and that the station relays ST and STA have responded, as just described, then we may assume that the step-by-step operation will occur on the off periods of their respective impulses in the usual manner, all of which has been explained in detail in my above mentioned application, Ser. No. 613,353, filed May 25, 1932, and such operation will not be considered in detail.

Reception of control impuZses.Assuming that the stepping relay 3V is picked up on the third off period after the third impulse, then it is in readiness for the reception of the fourth impulse. If the character of the fourth impulse is positive, then the normal switch machine control relay WN is energized by reason of a circuit closed from through a circuit including front contact 23 of relay SA, polar contact 24 of relay F in a right hand position, back contacts 25 and 26 of relays 5V and 4V respectively, front contact 21 of relay 3V, front contact 33 of relay STA, back contact 45 of relay WR, lower winding of relay WN, to

Withthe station relay ST picked up and the repeating relay STA picked up and stuck up by reason of its stick circuit, then the bus I5 is energized through front contact 32. Thus, upon the picking up of the relay WN, its upper winding is connected to the bus l5 through its front contact l6, and it will therefore be maintained stuck up.

On the other hand, if the character of the fourth impulse is negative, then a pick-up circuit is closed for the switch control relay WR from through a circuit including front contact 23 of relay SA, polar contact 24 of relay F in a left hand position, back contacts 28 and 29 of relays 5V and 4V respectively. front contact 75..

of relay 3V, front contact 34 of relay STA, back contact 49 of relay WN, lower winding of relay WR, to The response of the relay WR closing its front contact/M connects its upp-er winding to the bus l5 whichisenergized. for reasons previously explained. I

In brief, as soon as the station'is selected, the switch control relays areall'deenergized, which, if accomplished, causes the relay-STA to pick up and allows the switch control relays to becontrolled in accordance with their new control impulses. On the other hand, if that one of the switch control relays, which was previously picked up, fails to drop awaygthen the relay STA fails to pick up and there are no controls received. V

Assuming that'the fourth impulse has"picked up one or the other of the switch control relays WN or WR, then during the fourth foff period following the fourth impulse, the stepping relay vispickedup The character of the fifth rattle; (gen ra es the control of the right directionf relay RD or is ineffective to accomplish any control. Fore}:- ample, if the fifth impulse is positive in character, then the relay RD is energized bya circuit closed from through a circuit including front contact 23 of relay SA, polarcontact 24 of relay F in a right hand position, backcontact 25 of relay 5V, front, contact 26 of relay 4V, front contact 38 of relay ST, back contact 52 of' relay LD, lower winding of relay RD, front contact v of relay STA, to As soon asthecontacts of the relay RD respond,a stick circuit is closed from through a circuit including front contact 64 of relay T, back contact 56 of stop relay S, front contact 58 of relay RD,j upper winding of relay RD, to

On the other hand, if the character of the fifth impulse is negative, thentherelay, RD is not picked up and underthe circumstances'assumed there is no control executed, but it isto benoted that under certain other circumstances the negative character of the fifth impulseis to be employed for other purposes later pointed out- The fifth stepping relay is picked up during the fifth off period following the fifthimpulse', so that the character of the sixth impulse may be utilized to position its control relays. u

If the sixth impulse is positive in -character, then the left direction relay ID is picked up, providing of course that the right direction relay RD has not previously been picked up.

For example, assuming for the time being that the sixth impulse is positivev in character and the preceding fifth impulse was negative in character, then the left direction relay LD, is energized by a pick-up circuit closed from through a circuit includingfront contact 23 of relaySA, polar contact 24 of relay Fin a right hand position, front contact 25 of relay 5V, front contact 39 of relay ST, back contact59 of relay RD, lower winding of relay LD, front contact 35 of relay STA, to As soon as the contactsof the relay LD respond, a stick circuit is closed from through acirouit including front contact 64 of relay T, back contact 66 of relay S, front contact 5| of relay LD, upper winding of relay LD, to

On the other hand, if the character of the sixth impulse is negative, nothing is accomplished under the circumstances being described, but under certain other circumstances later pointed out such a negativecharacter of the sixth impulse is provided for other purposes;

It should be noted here that the picking up of either direction relay closes a stick circuit for the switch control relay then picked up. More specifically, if the relay RD is picked up, the front contact 51 applies energy from to the bus IE; but, ifthe relay LD is picked up, its front contact 50 applies potential from to the bus l5. In either event, the energization of the bus l5 causes the stick circuit for that particular switch control relay which is picked up to be closed until'the'di'rection and signal control relays are i dropped.

' The communication system, after completing the sixth impulse,- enters into a period of rest and the station relay ST is deenergized thereby opening the stick circuit for the relay STA at front contact 36, so that it is deenergized. If

-enly a switch control relay has been governed during the cycle of operation and neither the-LD relay 'nor' the RD relay is picked up, then that switch control relay which is picked up is main- If the switch control relay WN is picked up during the cycle of operation, the normal operating circuit of the switch machine SM is closed from through a circuit including-back-contact 42 of relay WR, front contact 41 of relay WN, operating mechanism of switch machine SM, to The closure of this normal-operating circuit causes the switch machineSM to unlock the track switch TS and operate it to anormal extreme locked position.

On the other hand, if the switch control relay WR is picked up during the cycle of operation, then the reverse operating circuit is closed for the switch machine SM from through a' circuit including back contact 47 of relay WN, front contact 42 of relay WR, operating mechanism" of switch machine SM, to Closure of this reverse operating circuit causes the switchma- ,chine- SM to unlock the track switch TS and operate it to a reverse extreme locked position.

If the normal switch control relayWN is energized during the cycle of operation, then the normal correspondence relay NC is energized with theswitch in a corresponding position as indicated by the relay WP, as previously explained. But, if the reverse control relay WR is energized during the cycle, the reverse correspondence relay RC is energized with the switch TS in a corresponding reverse position as indicated by the relay WP by reason of a circuit closed from through a circuit including Irrespective of which position the track switch is caused to assume, trafiic in an eastbound .or westbound direction may be established by the energization of the corresponding direction relay RD or LD respectively, as previously described.

If the direction relay RD is picked up and-held up as previously described, then either the signal lAor IB is cleare-d'depending upon whetherthe track switch TS is in a normal position or a repractices, to

WN' and WR.

With the relay RD picked up and the track switch TS in a normal position, the signal control relay IAG is energized by a circuitclosed from through a circuit including front contact 62 of relay RD, windings of relay IAG, front contact 88 of relay NC, through such automatic selections as may be desired in accordance with signaling practices, to The opening of back contact 75 of relay lAG deenergizes the red or stop indicator of the signal IA, while the closing of front contact 15 causes the signal IA to in- .dicate caution or proceed dependent upon the automatic control in accordance with traffic conditions as determined by polar contact '16 of the home relay iH in accordance with the usual practices.

On the other hand, if the track switch TS is in a reverse position with the relay RD energized, then the signal control relay IBG is energized by a circuit closed from through a circuit including front contact 63 of relay RD, front contact 10 of relay RC, windings of relay IBG, through the various automatic selections as required in accordance with the usual signaling The energization of the relay IBG opens back contact 12 and deenergizes the red or stop indicator of the signal IB, While the closure of the front contact 12 causes the signal IE to indicate proceed.

Assuming, however, that the left or west direction relay LD is energized with the track switch TS in a normal position, then the signal control relay EAG is energized by a circuit closed .from through a circuit including front contact 55 of relay LD, windings of relay 2AG, front contact 59 of relay NC, through such automatic selections as may be desired in accordance with the usual signaling practices, to The energization of the relay ZAG opens back contact 14 thereby deenergizing the red or stop indicator of the signal 2A, while the closure of front contact 14 causes the caution or proceed indication of the signal 2A to be displayed as selected by the polar contact ll of the home relay 2H in accordance with the usual practices.

On the other hand, assuming that the left or west direction relay LD is energized, but the track switch TS is in a reverse position, then the signal control relay ZBG is energized by a circuit closed from through a circuit including front contact 56 of relay LD, front contact ll of relay RC, windings of relay 213G, through such automatic route may be put to stop either by manual manipulation of a control lever in the control office or automatically by the passage of a train over the detector track section associated with the track switch TS.

Let us first consider the passage of a train over i the track section deenergizing the track relay T. Such deenergization of the track relay T opens the stick circuit for the relay ID at its front contact 64 so that relay LD drops away. This verse position as controlled by its control relays deenergization of the relay LD opens its front contact 56 and deenergizes the relay ZBG which in turn deenergizes the proceed indicator of the signal 23 and energizes its stop indicator.

It is noted that the opening of front contact i3 of the track relay T deenergizes its repeater relay TP, so that its back contact 65 applies energy to the stick circuits of the direction relays LD and RD, providing of course that one of them is again picked up subsequent to their deenergization upon the intitial opening of their stick circuits at front contact 64 of the relay T. In other words, means is provided for only momentarily opening their stick circuits so that'should another cycle of operation of the communication system occur immediately after the dropping of the track relay T, the controls of such a cycle will not be lost.

We may now consider how a route may be manually put to stop. As a stop control need be received only when a route is actually cleared, .then the reception of the stop code can readily be made dependent upon the prior reception of a proceed code.

For example, when the relay LD has been picked 25 up on a previous cycle, the fifth impulse can be made negative in character and energize the stop relay S which will deenergize the relay LD at the end of the cycle. Also, when the relay RD has been picked up on a previous cycle, the sixth impulse can be made negative in character and energize the stop relay S which will deenergize the relay RD at the end of the cycle. Thus, the present disclosure uses negative impulses for both the fifth and sixth impulses for the stop code, and these impulses are used to pick up the stop relay S only when the corresponding relay RD or LD is picked up. In other words, with the direction relay LD picked up by a positive character of the'sixth impulse during one cycle of operation, it can be deenergized by a negative character of the sixth impulse upon a following cycle of operation by the energization of the stop relay S. When the sixth impulse is negative, a circuit is closed from through a circuit including front contact 23 of relay SA, polar contact 24 of relay F in a left hand position, front contact 28 of relay 5V, front contact 41 of relay ST, front contact 53 of relay LD, windings of relay S, to

The response of the contacts of the relay S closes a stick circuit from through front contact 54 of relay LD, front contact 67 of relay S, windings of relay S, to In other words, the relay S is maintained energized only until the direction relay, which has allowed it to be picked up, drops away. This dropping away of the left direction relay LD is accomplished by the opening of its back contact 66 of the relay S. However, it is noted that the contact 66 of relay S is ineffective to drop the relay LD until the end of the cycle as it is shunted by the front contact 31 of relay ST which is closed until the end of the cycle when the system is restored to normal. With the relay RD picked up, a negative fifth impulse causes the stop relay S to be picked up by reason of a circuit closed from through a circuit including front con- Typical code table Sixth impulse Fifth impulse Code No.

Fourth impulse Use Not used Switch normalsignals east Switch normalsignals west Switch normal-signals stop Not used Switch reversesignal east Switch reverse-signal west Switch reversesignal stop With reference to the above code table, it is readily apparent that the track switchTS can be operated to normal or reverse positions at the will of the operator without the clearing of a route by the use of code Nos. 4 and 8 respectively. The use of such codes to eifect the 0peration of the track switch must be transmitted after the signals have been put to stop, because the switch control relays cannot be changed in their positions while a signal is cleared by the energization of one of the relays RD and LD. Thus, thetransmission of a stop code such as No. 4 or No. 8 to put a route to stop cannot be effective upon the same cycle to cause the operation of the track switch. This means that the manipulation of the switch control lever in the tower while a signal is cleared will be ineffective to either interrupt the signal control or to cause the undesired operation of the track switch during the establishment of a particular route.

It is noted that if a particular code is transmitted to clear a particular route, that. the false or undesired change of either of the signal clearing impulses of that code to the opposite character forms a code such that no signal will be cleared.

For example, if the code No. 2 is transmitted and the relay RD is picked up on the'fifth impulse as that impulse is. positive in character, then the succeeding sixth impulse is falsely positive in character will cause the energization of the stop relay S by reason of the closed condition of front contact 59.

'\ This is because of a circuit closed from through a circuit including front contact 23 of relay SA, polar contact 24 of relay F in a right hand position, front contact 25 of relay 5V, front contact 39 of relay ST, front contact 59 of relay RD, windings: of relay S, to

Similarly, if the signal control relay LD is intended to be picked up and the code No. 3 is transmitted, but for some reason the fifth im- HV pulse changes its character from negative to positive as. received at the field station, both the fifth and sixth impulses. being positive in character causes the stop relay S to be energizedas just pointed ou Thus, the stop relay S is energized when the negative impulse of either an east or west signal code is changed to a. positive character, sothat both relays RD and LD are insured of being deenergized at the end of such cycle thereby resulting in the establishment of no route. 1

It is readily apparent that should the positive impulse of an east or west code falsely change to a negative character, such a change corresponds to the stop code and no signal control relay RD or LD will be picked up.

If, for some reason, a stop code such as No. 4

or No. 8 is: transmitted when a route is cleared,

the change of the character of either the fifth or sixth impulse of such stop code results either in the putting to stop of such route which is then cleared or in the maintenance of the route already cleared.

For. example, if the fifth impulse of the code No. 4 is. changed to a positive character in place. of a negative character, .then the code No. 2 results and the transmission of such code with the relay RD energized maintains that relay ener gized; but if the sixth impulse of the code No. 4 changes to a positive character, then the stop relay is energized with the relay RD picked up so that. the ro-ute'is putto stop. Similar conditions are true when the signal control relay LD is picked up.

Summary Thus, from the above description it is readily apparent that a centralized tramc controlling system is provided in which it is required that the switch control relays and signal control relays actually receive their controls during a cycle of operation in order for a route to be cleared. Ifthe switch control relays do not assume deenergized inactive positions at the beginning of each cycle of operation, no control is received. If a route has been cleared, then the switch cannot be actuated because the switch control relays cannot be restored to inactive deenergized positions.

The operation of the system is such that various checks in the reception of the code are employed with regard to the signal control.

The system is also arranged so that correspondence is required between the track switch and the switch control relays so that a route cannot be cleared Without the proper response of the switch machine.

These various features and others which are apparent from a study of the above description provide a safe and reliable control for the traffic controlling devices through the medium of a code type communication system.

Having thus described a centralized traffic controlling system as one embodiment of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume; and, it is to be further understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements or practice, without in any manner departing trol means, and means allowing said control means to be conditioned over said communication system only when said control means has been rendered inactive.

2. In combination, a switch machine for operating a railroad track switch, normally active control means for causing the normal or reverse operation of said switch machine in accordance with its normal or reverse condition, a code: type communication. system operable through cycles of operation for storing a normal or a reverse condition in said control means, means rendering said control means inactive during an early part of a cycle of operation of the communication system by cancelling the normal or reverse condition stored therein, and means allowing said control means to be conditioned through the medium of the communication system during a later part of said cycle only when said control means has bee-n rendered inactive.

3. In combination, a line circuit energized with a plurality of positive and negative impulses applied thereto to form a distinctive code combination, a step-by-step means operable to take one step for each of said impulses, a positive. code receiving relay and a negative code receiving relay for each step selected by said step-by-step means, means for actuating either a positive or a negative code receiving relay on each step depending upon whether the impulse for that step is. positive or negative, and means preventing the actuation of any of said code receiving relays and permitting the actuation of said step-by-step means unless all of the said code receiving relays are in non-actuated positions at the beginning of said code combination of impulses to said'line circuit.

4. In combination, two control relays each of which has active and inactive positions, control means for selectively actuating one or the other of said control relays, conditioning means for at times rendering said control means effective only if said two control relays both assume inactive positions, stick means for maintaining the last actuated control relay in its active position, and means for rendering said stick means ineffective each time before said control means is rendered effective by said conditioning means.

5. In combination, a code transmitter, a code receiver, means for storing a received code, means for cancelling a received code before the reception of another code, and means for preventing said another code from acting on said storing means and being stored thereby until said received code has been cancelled by said cancelling means.

6. In combination, a line circuit having a plurality of positive and negative impulses applied thereto to form a distinctive code combination, a positive and a negative code receiving relay for each step, a station relay at times picked up when said plurality of positive and negative impulses forms a code combination designated for its particular station, a station repeating relay, a step-by-step means operable to take one step for each of said impulses, a pick-up circuit for said station repeating relay closed when and only when said station relay is picked up and said positive and negative code receiving relays are all dropped away, a stick circuit for said station repeating relay including its own front contact and a front contact of said station relay, a pick-up circuit for each of said positive code receiving relays including a front contact of said station repeating relay and a contact closed for its corresponding step of said step-by-step means and said circuit being closed for that step only if the impulse for that step is positive, a pick-up circuit for each of said negative code receiving relays including a front contact of said station relay and a contact closed for its corresponding step of said step-by-step means and said circuit being closed for that step. only if the impulse for that step is negative, and means controlled by said positive and negative code receiving relays.

7. In combination, a line circuit having a plurality of positive and negative impulses applied thereto to form a distinctive code combination, a step-by-step means operable to take one step for each of said impulses, code receiving means for each step of said step-by-step means, a station relay rendered active when, said impulses are to control said code receiving means, a station repeating relay rendered active only when said station relay is rendered active and all of said code receiving means are inactive, and means for allowing said code receiving means to be controlled in accordance with said code combination only when said station repeating relay is rendered active.

8. In combination, a line circuit having a plurality of diiferent series of distinctive impulses applied thereto, particular ones of which are des ignated for particular stations of a'plurality of stations, a step-by-step means at a station operable to take one step for each impulse of the particular series designated for that station, code registering means for each step of said step-bystep means, a station relay rendered active when a particular series of impulses designated for that station are applied to said line circuit, and means allowing impulses to be registered on said code registering means only when said station relay is rendered active and all previously registered impulses have been cancelled at the beginning of the particular series of impulses designated for that station.

9. In combination, two control relays each of which has active and inactive positions, control means for selectively actuating one or the other of said control relays, conditioning means for at times rendering said control means effective only if said two control relays both assume inactive positions, a first stick means for maintaining the last actuated control relay in its active position,

means for rendering said first stick means inef-- fective each time before said control means is rendered effective by said conditioning means, and a second stickmeans for preventing said first stick means being rendered ineffective.

10. In combination, two control relays each of which has active and inactive positions, control means for selectively actuating one or the other of said control relays, conditioning means for at times rendering said control means effective only if said two control relays both assume inactive positions, stick means for maintaining the last actuated control relay in its active position, means for rendering said stick means ineffective each time before said control means is rendered effective by said conditioning means, and means controlled by each of said control relays for preventing the actuation of the other of said control relays at any time.

11. In combination, a line circuit having a plurality of combinations of coded impulses impressed thereon, a code receiver connected to said line circuit and responsive to said impulses, a code repeater controlled by said code receiver, code storing means, connecting means for connecting said code repeater to said code storing pressed thereon, a code receiver connected to said line circuit and responsive to said impulses, a code repeater controlled by said code receiver, code storing means, connecting means for connecting said code repeater to said code storing means, means controlled by said code repeater for operating said code storing means in accordance with the coded impulses impressed on said line circuit, and means jointly controlled by said connecting means and said code storing means for placing and maintaining said connecting means in a condition to allow said code storing means to be controlled by said code repeater only 7 if no code is stored in said code storing means.

13. In combination, a line circuit energized with a series of positive and negative impulses applied thereto to form a distinctive code combination, step-by-step means operable. to take one step for each of said impulses irrespective of their polarity, a positive code receiving relay and a negative code receiving relay for each step of said step-by-step means, pick up circuits for said positive and negative code receiving relays for each step prepared by the stepping relay for that step, means for energizing the pick up circuit for the positive or the negative code receiving relay on each step depending upon whether the impulses for that step is positive or negative,

and means allowing the energization of said pick up circuits for each step only providing all of said positive and negative code receiving relays.

are deenergized at the beginning of said series of impulses, said means acting without preventing the operation of said step-by-step means in response to said impulses.

14. In combination; a line circuit energized with a series of positive and/or negative impulses applied thereto to form a distinctive code combination; a series of stepping relays caused to take one step for each impulse on said line circuit irrespective of its polarity; a plurality of positive neutral code receiving relays, one for each step; a plurality of negative neutral code receiving relays, one for each step; a contact closed at the beginning of each series of impulses only providing all of said positive and negative code receiving relays are deenergized; means for energizing either the positive or the negative code receiving relayfor each step in accordance with whether the impulse for that step is positive or negative but only providing said contact is closed; stick circuit means effective after the beginning of a series of impulses for maintaining those of said positive and negative code receiving relays picked up that are selectively energized in accordance with the characters of said impulses for that series; and means for momentarily opening said stick circuit means at the beginning of every series of impulses.

THOMAS J. JUDGE.

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