US2344283A - Railway signal apparatus - Google Patents

Description

March 14, 1944. PL N. BOSSART RAILWAY SIGNAL APPARATUS FiledAug. 50, 1941 3 Sheets-Sheet 1 INVENTOR l. I PaaZMBanr'am. av

flaw HIS ATTORNEY March @4, 1944. P, N, B ssmf 2,344,283

RAILWAY S IGNAL APPARATUS Filed Aug. 30, 1941 3 Sheets-Sheet 2 66 62 SW aggas G panama??? Fl .5. J y BYQ 2 H15 ATTORNEY March 14, 1944. P, N BQSSART 2,344,283

RAILWAY SIGNAL APPARATUS Filed Aug.-30, 1941 3 Sheets-Sheet 3 HIS ATTORNEY Patented Mar. 14, 1944 RAILWAY SIGNAL'APPARATUS Paul N. B'ossart, Cheswick, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa a corporation of Pennsylvania Application August 30, 1941, Serial No. 409,046

17 Claims.

My invention relates to railway signal and, communication apparatus, and it has particular reference to the organization of such apparatus into novel and improved systems for effecting control or communication by means ofenergy transmitted from a railway train or vehicle. More particularly, my invention relates to the organization of such apparatus into novel and improved systems for controlling traiiic controlling or signal devices, located along the wayside, by means of energy transmittedto the trackway from a train.

In general, it is proposedin accordance with my invention to provide means ona train for impressing on a trackway, current having a fre quency proportional to the train speed, andto provide means in the wayside receiving such current for efiecting a control or controls in accordance with the frequency of the received current. More specifical it isproposed to provide a system utilizing current impressed by a train on the trackway and having a frequency corresponding to the train speed, for controlling the operation of a warning device, such as a highway crossing signal, positioned along the wayside.

In systems for controlling highway crossing signals, it is advantageous to provide an adequate warning period during which operation of the crossing signal device is effected prior to the arrival of trains at the crossing, thereby to enable 0 operators of vehicles on the highway to bring theirvehicles to a stop short of the crossing. Ordinarily, the operation of the warning device is initiated when a train reaches a predetermined point in.the rearotan intersection, and the operation of the signal is maintained until the train vacates the crossing. In order to provide an adequate'warning interval under all conditions, the point at which operation of the signal is initiatedmust, of course, be so chosen as to provide a predetermined minimum warning interval for trains operating at the authorized provide a minimum warning interval of, say, 20

seconds prior to the train arriving at the crossing it is apparent that trains operating in the, lower ranges of speed such as at 15 miles per hour, or one-eighth as fast as the maximum authorized speed, will require eight times as. long to travel from the point of initiation of the crossing signal operation to the crossing and hence will provide a warning period eight times as long as the minimum period, or some two inutes and forty seconds induration. Such a warning interval provided for slow movingtrains is obviously undesirable since it unduly and unnecessarily blocks or ties up vehicular traffic on the highway. In addition, such unduly long warning. periods might cause motorists to disregard the warning when a train does not approach the crossing within a short time after the warning is initiated.

In view of the foregoing and other important considerations, it is an object of my invention to provide a noveland improved system forcontrolling highway crossing signals in such manner as to obtain a substantially uniform warning period of operation of the signal prior to a train reaching an intersection, irrespective of the speed of the train. Specifically, the system is organized in such a manner that in the normal range of the train speeds, such as from approximately. 7 /2 to 120 miles per hour, inclusive, the warning period of operation of the crossing signal prior to arrival of a train at the crossing is never less than the predetermined minimum period and never greater than double such predetermined minimum period. period of operation effected prior to the arrival of a train at the crossing is never more than twice as long as the minimum warning period, hence the warning period is caused to be of a substan-. tially uniform length irrespective of the train speed.

' Another object of my invention is the organization of railway signal and communication apparatus into novel and improved systems for effecting a control or controls in the wayside in response to energy supplied by a train to the trackway.

A further object is the provision, in a system or" the class above described, of means for selectively controlling a device in the wayside in acbodying my invention, and shall then point out the novel features thereof in claims.

In other words, the maximum In the accompanying drawings, Fig. 1 is a diagrammatic view illustrating the wayside portion of the apparatus embodying my invention. Figs. 2 and 3 are each diagrammatic views illustrating modifications of a portion of the apparatus represented in Fig. 1'. Fig. 4 is'a diagrammatic view illustrating the train-carried portion of apparatus embodying my invention. Fig. 5 is a diagrammatic view illustrating a modification of a portion of the apparatus represented in Fig. 4. Figs. 6 and 7 are each diagrammatic views illustrating modifications of portions of the apparatus represented in Fig. 1. In each of the several views, similar reference characters have been employed to designate corresponding parts.

As above stated, an object of my invention is to provide means controlled by energy impressed by a train on a trackway to provide a substantially uniform warning period of operation of a signal prior to the arrival of a train at a highway grade crossing. To effect this and other important objects of my invention, the wayside portion of the apparatus embodying my invention is applied, as shown in Fig. 1, to a stretch of railway track over which traffic normally operates in the direction indicated in the drawing by an arrow, or from left to right as viewed in Fig. 1. Intersecting the stretch at grade is a highway H, and provided at the railway-highway intersection are any suitable or desired forms of crossing signals or highway crossing warning devices, such as, for example, an audible signal S in the form of an electric bell. The track rails I and la are divided by means of the usual insulated joints 2 into a plurality of successive adjoining track sections J-K, KL, LM and M-N, which sections extend from the intersection in the direction of approaching trains so as to be traversed in the order named by eastbound trains approaching the crossing.

The entrance end J of the first section JK traversed by a train approaching the crossing is located ata distance from the crossing equivalent to that traversed by a train operating at the maximum permissible speed for the predetermined minimum period selected for the crossing signal; the entrance end K of the second section, K-L, traversed by the train is located at a distance from the crossing substantially equivalent to that traversed by a train operating at one-half the maximum speed for the predetermined minimum operating period; the entrance end L of the third section, L-M, traversed by the train is located at a distance from the crossing equivalent to that traveled by a train operating at one-quarter the authorized maximum speed for the predetermined minimum operating period; and the entrance end M of the fourth section, M-N, is located from the crossing a distance substantially equivalent to that traversed by a train when operating at oneeighth the authorized maximum speed for the predetermined minimum operating interval.

Each of these track sections is provided with a track circuit comprising a suitable source of current, such as a track battery 3, and a track relay, designated by the reference character TR. with a suitably distinguishing suffix, connected across the rails at the opposite ends of the section. The connection of relay TR! to the rails of section J-K is effected, as shown, over a circuit including in series front contacts 8 and 9 of relays TRZ and TR3, respectively, hence relay TRI is released whenever a train occupies one or more of the three sections J-K, K-L and L-M, and is thus responsive to traffic in each of the named three sections.

Associated with relay TRI are two repeater relays 'I'PRI and TPRZ, normally energized in series over an obvious circuit including front contact [0 of relay TR! and a suitable source of current, such as a battery not shown but having its opposite terminals designated by the reference characters B and C. These repeater relays are, therefore, responsive to traffic conditions in each of the track sections J-K, KL and L M.

Associated with the track relays TRi, and TR3 is a polarized relay PR provided with an energizing circuit completed when relay TR! is released and relay TR3 is picked up. .The circuit of relay PR. includes pole changing contact members l2 and I5 of relay PR2, hence when the circuit of relay PR is completed, the relay is caused to operate its contact members to one extreme position such as to their left-hand positions, as viewed in the drawings, when relay TR2 ispicked up to supply current of one relative polarity to the circuit, and such relay operates its contact members to their opposite extreme or right-hand positions in response to energy of the opposite polarity supplied to the circuit when relay TRZ i released. When the energiZ- i'ng circuit of relay PR. is opened, as when relay TRI is picked up or relay TR3 is released, the contact members of relay PR operate to their pendant or intermediate positions.

The track relays TR and the associated relays TPRl, TPRZ and PR, have associated therewith apparatus arranged so as to cause operation oi the crossing signal S to be initiated when a train enters section J-K, K L or LM at a speed in excess of one-half, one-quarter and one-eighth the authorized maximum speed, respectively, That is to say, when a train approaches the crossing at a speed ranging between one-half and the full maximum authorized speed, operation of the signal is initiated when such train enters sect-ion J-K. If the train is operating at a speed varying between one-quarter and one-half the maximum authorized speed, the initiation of the op eration of the signal is postponed oi delayed, ill" a manner to be made clear presently, until the train enters section K-L. Should the train be operating at a speed varying between one-ighthf and one-quarter of the maximum authorlied; speed, operation of the signal is then postponed until the train enters section L-M; while if the train is operating at a speed less than oneelghth of the maximum speed, operation of the signal is then initiated when section MN is entered.

The above described control of signal S is effected by means of an operating circuit provided for the signal and controlled by the track relays TR and by means receiving energy impressed by a train on the trackway and selectively respon sive. to the frequency of the received current. The operating circuit of signal S comprises two alternate paths, one path of which includes back contact I? of relay TR4 and a source of cur rent, and the other path of which extends from terminal B through back contact 18 of relay 'I'PRZ, back contact IQ of, a control relay CR, to be referred to hereinafter, and signal S to the other terminal C. It is apparent, therefore, that operation of signal S is efiected whenever relay TRd, associated with section M-N, is released, and that operation of th signal may be effected whenever relay TPR2, controlled by traflic in sections J-K, K-L and L-M, inclusive, is. released. provided that control relay CR also is released.

Relay CR has associated therewith wayside apparatus comprising means for deriving from the trackway energy applied thereto from a train; and decoding means operated by such receiving means for controlling'relay CE in accordance with the frequency of the received energy. Such receiving means, as shown, comprise conductors, one of which, conductor 2!, is connected at 22 to rail of section M-N and extends parallel to the rail a short distance in either direction, while the other conductor 23 is connected at 24 to track rail in. of section MN and likewise extends in either direction parallel to such rail a short distance, of the order of 100 to 200 feet. Each conductor is grounded at each end and is tuned, as by condensers 25, to a predetermined or desired frequency. Adjacent the point of connection of the conductors to the track rails are provided loops, preferably having a single turn, which are coupled to pick-up coils 26 tuned by condensers 2'! to a frequency corresponding to the predetermined frequency.

Alternate means for coupling the pick-up coils 25 to the trackway may be employed and are shown in Figs. 2 and 3. In Fig. 2 a pick-up coil 26 is disposed in the trackway in inductive relationship with both track rails l and la. In Fig. 3, pick-up coil 25 is inductively coupled with a loop. formed in a wayside conductor '29 disposed adjacent the track rails and extending from the crossing to the entrance end of section JK first to be entered by a train approaching the crossing. This wayside conductor 28, grounded at each end, is preferably tuned, as by condensers 3G, to a'frequency corresponding to the predetermined. frequency hereinbeiore mentioned, and may be utilized to transmit along the trackway current of a predetermined frequency applied from a train or vehicle to the trackway in a manner to be made clear presently.

Use of the conductor 23 is optional and may, if desired, be either dispensed with or employed in connection with impedance networks provided at the adjacent ends of each two adjoining track sections. These impedance networks comprise a pair of impedance elements 31 connected respectively across the track rails at the adjacent-ends of two adjoining track sections, and which pair of elements are center-connectedso as to transmit around the associated pair of insulated-joints 2 energy flowing in the rails in multiple; but which impedance networks are effective'to prevent track circuit energy, flowing through the rails in series, from being transmitted around the joints from one section into the adjoining sec-- tion. The impedance networks are, therefore,

effective to transmit through the trarkway andaround the insulated'joints' 2 energy applied from a train to the two rails of thetrackway in parallel.

The. decoding" apparatus hereinbefore mcn-- tioned comprises an amplifier'-demodulatoi'- filter unit ADF, a plurality of relays,.designatedr plifier-demodulator-filter unit are not shown in:

the drawing, but such unit may be similar, for

example,- to'units of. the type shown in United States: Letters, Patent: No; 2,064,639 granted. on

December 15, 1936, to Leland C. Whitelock et al, and employed in train communication systems for amplifying, demodulating and filtering current supplied to the trackway. Unit ADF, however, differs from the usual amplifier-demodulator-filter units in that it incorporates two call units, one unit Ul being tuned to a first frequency of modulation and the other unit U2 being tuned to a second frequency of modulation impressed on the current received from the track rails.

The amplifier-demodulator-filter unit ADF is connected by wires 35 and -36 to pick-up coils 2t, and it incorporates the usual electron tube amplifiers which may have their plate circuits energized, as indicated in the drawing, only when relay TPRI is released to close its back contact 31. However, if desired, such plate circuits may be steadily energized. One relay SR is connected to the output terminals of call unit U2 of the unit ADF, and hence is energized during the interval that current modulated at the second frequency is received by the unit from the trackway.

The other call unit Ul supplies energy to two relays IR and ER, which relays accordingly are picked up when current modulated at the first frequency is received by the amplifier-demodulator-filter unit ADF.

The relay chain RC, as shown, comprises a plurality of relays 46, 4|, 42 and 43-. One relay 4!! functions as an impulsing relay for a purpose to be made clear presently, and is caused to operate at a rate dependent upon the rate of operation of relay IR and the position of polarized relay PR. When relay PR is energized by current of one polarity and its polar contact members are in their left-hand positions, as viewed in the drawing, the four relays of the chain are sequentially energized or operated, and relay 4G is caused to operate a rate onequarter as fast as relay IR. When relay PR operates its contact members to their right-hand positions, relays 49 and ll; are" alternately operated and relay 4E accordingly operates at a pulsing relay 49. The other winding 45 ofrelay' FR is energized, in series with another portion of the winding 46, over an obvious circuit com-' pleted when back contact 48 of relayed is closed. The two portions of winding 45 are disposed so as to create opposing fluxes when energized, hence it follows that the flux in transformer 4% is caused to reverse at arate proportional to the rate of operation of relay 4!]. The two windings 4'4 and 45 of relay FR-a're arranged so that when the windings are alternately energized, contact member 5!!- of the relay is reversibly operated from oneextreme position to the other, and the windings of the relay and the proportioning of the transformer 4'! are so selected and proportioned i that each winding 44 and d5 effectively energlzed' only when the rate of flux reversal in trans former 4'? does not exceed a predetermined rat-e. Control relay CR, also comprises two windings,

one winding iii of which is energized by current derived from secondary winding 49 of transformer 41 and at times such current is caused to be substantially unidirectional in character due to the rectifying action of contact 56 of relay FR. That is to say, when flux having a given direction is present in transformer 41, current of one relative polarity is induced in one portion of winding 49 and is supplied over contact 50 of relay FR, in one position of the relay, to winding 5| of relay CR. Then, when the direction of flux in the transformer is reversed so that current of the opposite relative polarity is induced in the other portion of secondary winding 49, and if the rate of flux reversal is within that which relay FR follows, contact 50 is swung to its other position to cause the current induced in secondary winding 49 to flow through winding 5| in the direction corresponding to the current flow through the relay when contact 50 of relay FR is in its one position.

A checking relay COR also is provided, together with a ballast lamp BL, for a purpose to be made clear in the following description.

Ihe train-carried portion of the apparatus embodying my invention is represented in Fig. 4 as being provided on the locomotive and its associated tender, but it is to be understood of course that such apparatus may be provided on any desired railway vehicle. This apparatus, as shown, includes means for impressing on the track rails current having a frequency proportional to the train speed, and it comprises a transformer 66, a source of oscillations of the predetermined or desired frequency, preferably of the order of 1000 to 10,000 cycles per second, and means for modulating the output of the source of oscillations at a rate proportional to the train speed. The source of oscillations may, for example, comprise an inductor alternator HFG incorporated into the usual locomotive headlight generator LHG, and the output terminals of such inductor alternator are connected across the terminals of primary winding 6| of transformer 60 in series with a modulating contact of modulating device MDIU or MDI05, respectively. These modulating devices may, for example, comprise tuned alternators effective to operate at relatively low frequencies of, say, 19 and I05 cycles per second, respectively, and first one and then the other of the two devices is rendered effective to modulate the output of the conductor alternator, at a rate proportional to the train speed, by means of a suitable switch or commutator SW attached to or driven by an axle of the vehicle at a rate dependent upon the vehicle speed. A shown, the switching means SW is mounted on an axle and comprises four contact elements disposed 90 apart and mounted to engage the peripheries of a contacting surface 66 formed on the axle. Onehalf or 180 of the contacting surface 66 comprises a conducting material, and the other half comprises an insulating material. The arrangement of the modulating contacts, inductor alternator HFG, and contact elements of the switching means SW, as illustrated in Fig. 4, is such that during one-half of each revolution of surface 66, contact I of device MD'I'O is interposed in series in the connection of inductor alternator HFG to winding SI of transformer 60, and during the other half of each revolution contact I of the other modulating device MDI65 is interposed in such circuit connection. Such an arrangement obviously is effective to cause the two modulating devices to modulate the output of the inductor alternator alternately during the opposite half revolutions of surface 66.

In a modified arrangement of the modulating contacts, inductor alternator HFG, and contact elements of the switch SW represented in Fig. 5, the arrangement is such that one of the modulating contacts is shunted durin one-half of the revolution of contacting surface 66, and the other contact is shunted during the other half of such revolution. In such an arrangement, contact element 64 is connected to one terminal of inductor alternator HFG, the other contact element 62 disposed from element 64 is connected through winding 6| of transformer 66 to the other terminal of the inductor alternator, and the other two contact elements 63 and 65 are connected together by a jumper 61. Modulating contacts Ill and I05 of modulating devices MD" and MDI05 are connected, in series, directly across contact elements 62 and 64, and a connec tion is established from the other two contacting elements 63 and 65 to the series circuit connection of the modulating contacts, at a point intermediate such contacts. It is apparent that when the contacting portion of surface 66 is in the upper half, as viewed in the drawing, of its revolution, so that contact element 62 is in engagement therewith, a circuit is established from one terminal of inductor alternator HFG through contact ID of modulating devic MD'IIJ, contact element 63 or 65, conducting portion of surface 66, contact element 62 and windin 6I of transformer 60 to the opposite terminal of inductor alternator HFG, with the result that in this portion of the revolution of surface 66, the output of the inductor alternator is caused to be modulated by contact 10. During the other half of the revolution of surface 66 when the conducting portion of the surface is in engagement with contact element 64, a circuit is then established from one terminal of inductor alternator HFG through contact element 64, the conducting portion of surface 66, either contact element 63 or 65, contact I05 of modulating device MDIIJ5, and winding SI of transformer 60 to the other termnal of the inductor alternator, whereupon the output of the inductor alternator is caused to be modulated by contact I05. It follows, therefore, that the output of inductor alternator HFG is caused to be modulated at first one frequency during one-half of the revolution of member 66 and is modulated at another frequency during the other half of such revolution.

The output of inductor alternator HFG, modulated in the manner pointed out heretofore, is impressed upon the rails of the track longitudinally by means of a circuit which connects one terminal of secondary windin 69 0f transformer 66 to one of the hubs or axles of the tender, and which connects the opposite terminal of winding 69 to one of the hubs or axles of the locomotive. These axles are preferably insulated from each other, thus causing the rails in their longitudinal direction to form a part of the output circuit of transformer 60. Interposed in such output circuit is a tuning condenser H and a switch 12, the latter of which when opened functionsto interrupt the output circuit of transformer 60. Switch 12 also functions to control the operation of th modulatin devices MD, which devices are energized by current supplied from any suitable source, such as the direct current generator LHG, over an obvious circuit completed when switch 12 is closed.

Normally, the wayside portion of the apparatus embodying my invention hereinbefore described is in its normal condition as represented in Fig. 1, when sections J--K, K-L, L-M and MN are unoccupied. In this condition of the apparatus, the several track relays TR are picked up and repeater relays TPRI and TPR2 are ener gized, so that signal S is deenergized, while polar relay PR is likewise deenergized. Relays R associated with unit ADF are released, impulsing relay lil is energized over a circuit extending from terminal B through back contact l of relay 43, the upper winding of relay 40 and back contact It of relay HR to terminal C; but the other relays of the chain RC are released. Winding Q4 of relay FR is energized over an obvious circuit extending from terminal B through ballast lamp BL, a portion of winding 46 of transformer 47, winding is of relay FR and front contact 158 of relay 39 to terminal C, and contact 5!! of relay FR accordingly is caused to swing to its left-hand position, as viewed in the drawing. The flux of transformer i? is at a substantially constant state condition, hence there is no energy induced in winding 69 so that winding 5: of control relay CR is deenergized and the relay is released. Checking relay OCR is, however, in its normally energized condition.

With the wayside apparatus in its normal condition, a train or vehicle may operate on the track outside the limits of the stretch JN, and apply energy to the track rails without affecting the wayside apparatus since such trackway transmitted energy is substantialiy blocked by joints 2 at J (which joints are not Icy-passed by an impedance network), and also since any energy picked up by coils 23 and supplied to unit ADF is ineffective to cause operation of the associated relays due to the fact that the plate circuits of the unit are open at back contact 31 of relay TPRI, and as a result the apparatus of the filter is inactive.

When, however, a train or vehicle enters section J-K and shunts relay TRI, repeater relay TPRl releases to close its back contact 37 and thereby render active unit ADE, while repeater relay PI-R2 also releases at the end of its slow release interval. If the train or vehicle does not impress on the trackway, energy of the predetermined frequency modulated at a rate proportional to the train speed, as for example when such vehicle is not equipped with apparatus similar to that hereinbefore described and illustrated,

in Fig. 4, or if a vehicle equipped with such apparatus enters the section with switch 12 open, then at the end of the slow release interval of relay TPR2, back contact I8- closes to complete for signal S the previously traced energizing circuit extending through back contacts I8 and I9 of relay TPR2 and CR, respectively, with the result that operation of signal S is initiated. Operation of the signal, under the assumed conditions, is maintained until the train or vehicle.

clears the crossing.

If, however, a vehicle or train enters section. JK and impresses on the trackway energy of the predetermined frequency modulated in accordance with the train speed, then the wayside apparatus functions to delay initiation of operation of signal S if the train operates at a speed below a predetermined speed but not if the train.

speed is above such predetermined speed. vAs mentioned heretofore, the particular arrangement of the wayside apparatus illustrated in Fig. 1 is such that when a train enters the section 5-52 at a speed in excess of one-half its authorized maximum speed (assumed to be 120 miles per hour), theoperation of signal s is then initiated, whereas if the train speed is less than onehalf the authorized speed, the operation of the signal is delayed until another section nearer the'intersection is entered.

With the train in section J-K impressing on the trackway, energy modulated alternately at the first and second modulation frequencies and at a rate proportional to the train speed, relays ER and SR associated with unit ADF are alternately energized and deenergized, the first relay i 2R being energized in response to the alternate intervals during which energy modulated at the first frequency is received from the trackway, and the other relay 3R being energized in response to the opposite alternate intervals during which energy modulated at the second, frequency is received from the trackway. These relays are, however, provided with slow release characteristics so that each relay remains in its picked-up position unless the modulating energy occurs at the rate or frequency corresponding to a very low train speed of the order of about, say, 5 miles per hour or less. It follows, therefore, that both relays ER and SR are energized when a train operates on the trackway at a speed above such low speed. The purpose of the relays 2R and SR will be made clear presently.

The other relay IR associated with unit ADF is likewise alternately energized and deenergized in step with the alternate intervals during which energy modulated at the first modulation frequency is received from the trackway, and relay IR is arranged to respond to such energy by picking up in response to each interval during which energy of the first modulation frequency is, received from the track rails, and by releasing during each of the other intervals during which energy of the other or second modulation frequency is received. Contacts I6 of relay IRaccordingly is operated at a rate corresponding to the rate at which the intervals of the first modulation frequency are received, orat a rate corresponding to the speed of the vehicle.

When the train occupies section J-K, polar relay PR is energized over its previously mentioned circuit by current having a polarity such that it causes contact members and 8| of the relay to assume their left-hand positions, whereupon impulsing relay 4% is energized and the relay chain RC associated with relay IR is conditioned to cause impulsing relay 411 to operate at a rate corresponding to one-quarter of the rate of operation of relay IR. Each of the relays of the chain is provided with two windings, an upper or pick-up winding and a lower or stick winding, and the relay chain is arranged in such manner that the pick-up winding of impulsing relay ii] is energized over a back contact of relay 43,

v while the pick-up winding of relays M, 42 and.43

gized, whenthe wayside apparatus is inactive and the track sections areall unoccupied, over a circuit including back contact T5 of relay 43 and back contact It of relay IR. When section JK becomes occupied and relay TRI drops to close its back contacts II and I6 to cause relay PR to swing its polar contact members 80 and BI to their respective left-hand positions, and when relay IR closes its front contact I6 in response to the first interval of energy modulated at the first frequency received by unit ADF, the stick winding of relay 48 is energized over a circuit extending from terminal B through front con- 7 tact 82 of relay 40, polar contact 80 of relay TR in its left-hand position, the lower winding of relay 4|) and front contact I6 of relay IR to terminal C; and the pick-up winding of relay 4| is energized over a circuit extending from terminal B through front contact 83 of relay 48, polar contact 8| of relay TR closed in its left-hand position, the upper or pick-up winding of relay 4| and front contact I6 of relay IR to terminal C. Relay 4| accordingly picks up and closes its front contact 84 so that when relay IR releases to close its back contact I6, the pick-up winding of relay 49 then is energized over a circuit previously traced, and the stick winding of relay 4| is energized over a circuit including front contact 84 and the lower or stick winding of the relay as well as back contact 16 of relay IR. In addition, the pick-up winding of relay 42 is energized over a circuit extending from terminal B through front contact 85 of relay 4 I, the upper or pick-up winding of relay 42 and back contact 16 of relay IR to terminal C, whereupon relay 42 picks up to close its front contact 88. When relay IR again picks up to close its front contact IS, the stick winding of relay 42 is energized over an obvious circuit including its own front contact 86 and its lower or stick winding as well as front contact I6 of relay IR; the stick winding of relay 4!! and the pick-up winding of relay 4| are also energized; and relay 43 is energized over a circuit extending from terminal B through front contact 81 of relay 42, the upper or pick-up winding of relay 43 and front contact I6 of relay IR to terminal C, whereupon relay 43 picks up to close its contact I5. When relay IR again drops to close its back contact I6, the lower or stick winding of relay 43 is energized over an obvious circuit including its front contact I and the lower or stick winding of relay 43 as well as back contact I6 of relay IR; the stick winding of relay 4| and the pick-up winding of relay 42 are likewise energized; and relay 4U releases since its stick circuit is open at front contact 16 of relay IR and its pick-up circuit is open at back contact I5 of relay 43. When relay IR again picks up to close its front contact 76, relay 4| becomes deenergized and releases, and when relay IR again releases, relay 42 becomes deenergized and releases. Relay 43 also releases when relay IR picks up following the release of relay 42, and relay 43 accordingly closes its back contact I5 to prepare the pick-up circuit of relay 40, which circuit is made effective upon the subsequent release of relay IR to pick up relay 48 and initiate the operation of the relays in the relay chain. It follows, therefore, that when the train occupies section JK, impulsing relay 40 is caused to operate its contact member 48 at a rate corresponding to one-fourth the'rate of operation of relay IR.

Each operation of contact 48 of impulsing relay 40 reverses the direction of flux in transformer 41, and causes one Winding 44 or the other winding 45 of relay FR to be energized. The windings of relay FR and transformer 41 are selected so that when relay 40 operates at a rate corresponding to a speed less than one-half of the authorized maximum speed (or a speed of less than 60 miles per hour), and the direction of flux is reversed in transformer 41 at one-fourth of such rate of operation of relay IR, the two windings 44 and 45 of relay FR are effectively energized and cause contact member 50 to be operated alternately to its left-hand position and then to its right-hand position at a rate corresponding to the rate of flux reversal in the transformer. This operation of contact member 50 of relay FR causes the alternating current induced in secondary winding 49 of transformer 47 to be supplied to winding 5| of relay CR as substantially unidirectional current, and relay CR accordingly is energized. If, however, relay IR operates at a rate corresponding to a train speed of more than 60 miles per hour and the flux in transformer 41 is reversed at a rate corresponding to one-fourth of such rate, the impedance of winding 46 is caused to build up to a value such as to limit the flow of current in windings 44 and 45 of relay FR to a value insufiicient to effectively energize the relay, and its contact member 50 accordingly is held stationary. The current induced in winding 49 of transformer 41 is, therefore, supplied to relay CR as alternating current, and relay CR accordingly is caused to remain released.

The previously mentioned-slow release interval of relay TPR2 is selected so that prior to the release of the relay, the wayside apparatus is enabled to pick up relay CR if the train in section JK is operating at a speed less than onehalf its maximum speed. It follows, therefore, that when relay TPRZ releases at the end of its slow release interval, operation of the signal is initiated if relay CR is not picked up due to the train operating in excess of 60 miles per hour, but if the train operates at a speed less than 60 miles per hour, the operation of the signal is postponed.

If the operation of the signal is initiated by a train entering section JK at a. speed in excess of 60 miles per hour, such operation is maintained until the train clears the crossing. If, however, operation of the signal is not initiated when section JK becomes occupied, the signal is set into operation when the train enters section K-L if the train operates at a speed in excess of one-fourth the authorized speed (or a speed in excess of 30 miles per hour), but is not initiated if the train speed is less than the predetermined speed of 30 miles per hour.

For example, I shall assume that a train approaches the crossing at a speed less than 60 miles per hour so that the wayside apparatus functions in the manner described to postpone operation of the signal when relay TPRZ releases. When the train enters section K-L, relay TRZ releases to close its back contacts I2 and I5 and pole change the current supplied to relay PR, whereupon relay PR shifts its contacts to their right-hand positions and conditions the relay chain RC to cause impulsing relay 4|] to operate at a rate corresponding to one-half the rate of operation of relay IR. With polar contacts 88 and 8| of relay PR in their respective right-hand positions, the pick-up and stick circuits of relay 40 and the stick circuit of relay 43 remain as traced hereinbefore, but the pick-up circuit of relay 43 is completed Over front contact 83 of relay 40 and the polar contact member 8| of relay PR closes in its right-hand posiwhen the train enters section K-L.

tion, hence only the two relays 4B and 43 are sequentially energized and relay 40 is caused to operate ata "rate corresponding toone-half the :relay 40 now operates only one-half and not onequarter as fast as relay IR, the upper limit of the train speed accordingly is shifted from 60 to 30 miles per hour, so that if the train operates at a speed in excess of 30 miles per hour, relay PR is ineffectively energized and relay CR releases to initiate operation of signal S. If, however, the train speed is below 30 miles per hour, then relay FR is effectively energized and relay CR also is energized to again postpone operation of the signal.

Assuming, for example, that the train in section K-L operates at a speed less than 30 miles per hour, operation of signal S is not effected In such event, operation of the signal may be effected when the train enters section L-M provided that the train operates at a speed greater than miles per hour, but such operation is not initiated when a train operates at a speed less than 15 miles per hour.

When the train enters section L-M, relay TRB releases and opens its front contacts l3 and id to deenergize relay PR whereupon contact members 88 and 8| of such relay assume their pendant positions to condition relay #8 to oper-' ate at a rate corresponding to the rate of operation of relay IR, and since relay lR now operates at a rate corresponding to the rate of operation of relay IR and not at a rate corresponding to one-half of the rate of relay IR, the upper limit of the train speed accordingly is shifted from to 15 miles per hour. It follows that if the train operates at a speed in excess of 15 miles per hour, relay FR is ineifectively energized and relay CR releases to initiate operation of signal S.

If, however, the train speed is below 15 miles .per hour, then relay FR is effectively energized and relay CR also is energized to again postpone operation of the signal.

In the event that a train approaches the crossing at a speed less than 15 miles per hour so that operation of the signal is not initiated when section L-M is entered, the signal is, set into.

operation irrespective of the train speed when section M--N is enteredand relay TR4 releases to close its back contact II. If, however, such train slows down to a very low speed or comes to a stop prior to entering the positive operating section M-N, the rate of operation of contact 12 by relay IR may then be insufficient to cause the energy induced in winding 49 and supplied to relay OR to reach a value suflicient to maintain relay CR picked up to thereby prevent operation of the signal. To preclude the possibility of causing operation of the signal with the train stopped short of section MN, the slow-speed and slow acting relays 2R and 3R are provided with control means for providing an energizing circuit for relay CR whenever either relay lR or 2B. is picked up and the other relay is released. When the train is stopped so that only energy modulated at one of the modulation frequencies is constantly impressed along the trackway, one or the other of the two relays ER and 3R is picked up while the other relay is released, so that relay QR is maintained energizedovera circuitextending from terminal B through ballast lamp contact of relay 3R and back contact 9! of relay 2R, or back contact 92 of relay SR and front contact 33 of relay 2R, to terminal C. The energization of relay CR, under the conditions assumed, prevents operation of the signal. The slow releasing characteristics of relays 2R and 3R are selected, however, so that when alternate intervals of energy modulated at the first and the second modulation frequencies are received at a rate sufficient to enable transformer 49 to effectively energize relay CR, both relays 2R and 3R are held constantly picked up and hence are not eifective to assist in energizing relay CR under such conditions.

Fig. 6 represents a portion of the apparatus illustrated in Fig. 1 modified in such manner as to provide safeguards against improper operation of the slow-speed relays associated with unit ADE. In Fig. 6, relays ZRi and JR! are employed and are controlled so as to preclude the possibility that one of the relays might remain up and the other relay remain down due to a failure in their respective control circuits, or to a failure of the apparatus on the train supplying energy to the trackway. These relays control a circuit, substantially similar to that provided by relays ER and. 3R of Fig. 1, for energizing relay CR when a train stops or slows down to a very low speed in section J-K, KL or L-M prior to entering the positive operation section M--N.

Referring now to Fig. 6, relay ZRI as shown comprises three windings ltiil, NH and H32, While relay tRi comprises two windings Hi3 and HM. A continuity transfer or make-before-break contact arrangement is provided on relay ER, and in the mid stroke position of the armature of relay ER, a bifurcated or bridging member Hit of relay IR engages both its associated front and back contact points to thereby complete an obvious energizing circuit for Winding let of rela 2R! when back contact 581 of relay 3R3 is closed. This circuit includes a suitable source of current, such as a battery Hi8. Winding Hi2 of relay 2R! is provided. with a short circuit path including contact its of relay PR in its right-hand, lefthand or dependent position, and an asymmetrical unit I Hi arranged to short circuit the winding for current caused to be induced therein due to a decay of flux in the relay but not for current induced in winding it]? due to a growth of flux in the relay. The short-circuit path provided for winding [d2 accordingly is effective to make relay 2R! slow to release, but does not materially affect its pick-up characteristics. The other winding IBI of relay 2R! is provided with a circuit eX- tending from call unit U! of the unit ADF through either front contact HI of relay ZRI or front contact I I2 of relay 3Ri, the winding iii! of relay 2R! and contact member I539 of relay PR in any one of its three positions, to the other output terminal of unit '0' l The other relaytRl has its winding '13 provided with an energizing circuit extending from one output terminal of call unit U2 of unit ADF through either front contact H3 of relay SR! or front contact iii of relay ERE, Winding I63 of relay 3R5, and contact member N5 of relay PR closed in any one of its three positions, to the other output terminal of unit U2. The other winding of this relay has a short circuit path completed through polar contact member N5 of relay 7BR closedinany one ofv its three positions and including asymmetrical unit IIS arranged so as to make the relay slow to release.

Normally, both slow-speed relays 2RI and 3RI are released when filter unit ADF is inactive. If, now, energy is applied to the trackway from a very slow moving train, unit ADF becomes active due to energy received from the trackway, and relay IR picks up when the first interval of energy modulated at the first modulation frequency is received, to cause winding I of relay 2RI to become energized during the travel of the armature of relay IR from its back to its front point. Relay 2RI accordingly picks up, and closes its front contact III to energize its other winding IIII, which winding holds relay 2RI energized until the modulation frequency changes to that of the second frequency. When that happens, relays IR and 2RI become deenergized, and during the slow release interval of relay 2RI, winding I83 of relay 3RI becomes energized to close d its front contact H3 and provide a circuit which holds relay 3RI up while energy of the second modulation frequency is received from the trackway. Back contact III! of relay 3RI also opens to open the circuit over which winding I Ill) of relay 2RI is initially energized. Then, when the modulation frequency is shifted back to the first frequency, Winding IoI becomes energized over .front contact H2 of relay 3RI during the slow release interval of the relay, and relay 2RI closes its front contact III to complete the previously traced circuit which holds that relay energized during the interval that energy modulated at the first frequency is received from unit ADF after relay 3R! releases. This action of the two relays in alternately becoming energized and released is continued as long as the slow moving train impresses energy on the trackway, hence such action of the relays is effective to hold relay CR energized to prevent operation of signal S when the train occupies any one of sections JK, K-L or LM, respectively.

The relays 2RI and BRI are arranged so that if the energy applied to the trackway is modulated at a rate corresponding to a speed in the normal range of operating speeds of a train, the relays 2RI and 3RI will be both held continuously energized, due to the alternate periods of the two modulated frequencies occurring for intervals shorter in duration than the slow release intervals of the relays. In such event, the relays 2RI and 3RI accordingly do not function to control relay CR, which relay is then controlled through relay PR, relay chain RC, frequency responsive relay PR, and transformer 41, in the manner pointed out in detail heretofore.

To :preclude the possibility that, due to a failure in the elements of either the train-carried transmitting apparatus or the wayside receiving apparatus, current modulated at only one of the modulation frequencies is supplied from unit ADF, when the train traverses the stretch at a relatively rapid rate of speed, the initial circuit for energizin relay 2RI is carried through a continuity transfer contact on relay IR, and the energizing circuits for relays 2RI and SRI are carried through contacts of relay PR. Thus, should the energy be modulated at only the second frequency, then relay IR is not picked up, and neither relay 2RI nor SRI is energized so that no control of relay CR is effected, either by the slow speed relays 2RI and 3RI or by the relay chain RC and the frequency responsive relay FR.

If. on the other hand, current modulated at only the first frequency is impressed by a moving train on the trackway, relay IR is caused to .pick up whenthe train enters section JK, and winding I [ll] of relay 2RI accordingly'becomes energized to cause the relay to pick up and close its front contact III, whereupon winding I02 of relay 2RI becomes energized over its own front contact and polar contact I09 of relay PR in its pendant position (the normal position of such relay contact). Relay PR is made sufiiciently slow acting that relay IR is able to reach its full attracted position to deenergize winding I 00 of relay 2RI, prior to contact member I09 of relay PR being swung to its left-hand position due to the energization of the relay by current of the polarity supplied thereto when section J-K becomes occupied. When, therefore, contact member I09 of relay PR is operated to its left-hand position, the energizing circuit of winding IOI is interrupted during the interval that member I09 is intermediate its dependent and its left-hand positions. At this time, the short circuit path provided for winding I02 is likewise open, hence relay 2RI is made quick to release and consequently releases to open its front contact III and deenergize winding IIII, prior to contact member I 09 of relay PR reaching its left-hand position. Both slow speed relays 2RI and 3RI are deenergized, and if relay IR is held constantly energized due to current modulated at the first frequency received from the track rails, neither the slow speed relays 2RI and 3RI nor the frequency responsive relay FR are effective to energize relay CR, whereupon that relay releases to initiate operation of signal S. It follows, therefore, that the arrangement of the apparatus shown in Fig. 6 provides safeguards to assure that a failure of the train or receiving apparatus cannot improperly prevent operation of signal S.

In addition, it is to be noted that the apparatus of Fig. 6 is arranged so as to check against possibility of failure of either or both the train and receiving apparatus after the train enters the section. In such event, if energy of but one modulation frequency is supplied from unit ADF, the passage of the train over the insulated joints 2 at K or L, causes operation of contact members of relay PR and thereby functions to open the energizing circuit of winding IOI or I03 of relays 2RI or SRI, respectively, as the case may be, to insure against such windings being improperly energized.

Should the train stop in any section, however, no operation of relay CR is then effected after the supply of energy is maintained at a single modulation frequency, and the slow speed relays accordingly are properly affected to prevent operation of the signal.

In the circuit arrangement shown in Fig. 6, the slow speed relays are slow releasing under normal conditions and there is a tendency for each relay to hold up over a front contact of the other relay when energy is alternately modulated at the two frequencies at a rate exceeding the rate at which either of the two relays drops out when deenergized. If desired, the arrangement may be modified to cause both slow speed relays to be both released when the upper speed limit of their operation is exceeded, and such a modified arrangement of the apparatus is represented in Fig. '7.

In Fig. 7, slow speed relay 2R2 has a pick-up winding I 29 and a holding winding I2I, and relay 3R2 has a pick-up winding I22 and a holding winding I23. A transformer I24 is provided and has its primary winding I25 energized over an obvious circuit including front contact I26 of relay IR and a suitable source of current such as a battery I21. When relay IR is released, back contact I26 closes and replaces battery I21 by a resistor I28 selected to have a resistance substantially equal to the internal resistance of the battery so as to maintain substantially constant the resistance of the primary circuit of the transformer.

' When relay IR picks up, an impulse of energy is supplied from secondary winding I29 of transformer I24 to winding I26 of relay 2R2 through a circuit including asymmetrical unit I30 in its low resistance direction, and contact member I09 of relay PR in any one of its three positions. When relay IR releases, an impulse of energy is supplied from the other secondary winding I3I of transformer I24 to winding I22 of relay 3R2over a circuit including asymmetrical unit I32 arranged in its low resistance direction, and contact member II5 of relay PR in any one of its three positions. The energizing circuit for the holding winding of relay 2R2 is carried through its own front contact I33 and back contact I34 of the other relay 3R2, as well as contact member II5 of relay PR, while the circuit of holding winding I23 of relay 3R2 passes through its own front contact I35 as well as back contact I36 of relay 2R2 and contact member IE9 of relay PR.

When the rates at which the alternate impulses of the two different modulation frequencies are supplied from unit IADF are relatively low, then relays 2R2 and 3R2 are alternately energized and deenergized and function as slow speed relays in much the same manner as relays 2R and 3R of Fig. 1, and relays 2RI and 3RI of Fig. 6. The relays are slow to pick up due to their holding windings being short circuited in the direction to provide slow pick-up characteristics, hence when the speed of the impulses actuating relay IR is increased, the relays will both be released since the time constants of the circuit supplying energy to the transformer and from the transformer to the relay are such that the current supplied to-the relays under the assumed conditions does not reach a value suificient to pick up the relays. Similarly, under the conditions assumed, the energy supplied to a holding'winding over a front contact of its own partner relay is not sufficient to maintain such relay energized when the partner relay releases, so that both relays become released and remain released as long as the impulses of energy actuating relay IR occur at a relatively rapid rate. It follows, therefore, that relays 2R2 and 3R2 function as slow speed relays when relay IR operates at a relatively low rate of speed, but that both relays are released when relay IR operates at a relatively rapid rate of speed.

The lamp BL, shown in Figs. 1, 6 and 7, preferably is a ballast lamp of any suitable and wellknown construction and comprising, for example, a filament formed of a material, such as iron wire, mounted in a sealed envelope and havin the characteristics of changing its resistance with changes in the voltage applied thereto. Checking relay CCR preferably has its winding formed of a material having a substantially zero temperature coefficient of resistance. The lamp BL and relay CCR function to maintain at a substantially constant value the voltage applied to the frequency responsive relay FR, thereby to cause-the apparatus includingrelay FR 'to'have substantially constant operating characteristics over a relatively wide range of voltage and temperature variations. Relay CCR is adjusted to release, and close its back contact 20 to complete an obvious energizing circuit forsignal S, should the voltage available drop to a value below that necessary for proper operation of the frequency responsive relay FR.

It is, of course, to be understood that while the apparatus embodying my invention has been illustraied and described with reference to certain specific values of, say, train speeds, ratio of maximum to minimum warning periods, and number of involved track circuited sections, the values specified are merely illustrative and may be varied, within limits of course, to best suit the particular conditions met in practicing the invention;

From the foregoing description, it is readily apparent that I have provided novel and improved systems for controlling wayside apparatus in accordance with the speed of a train on a track, by means of energy applied by a train to the trackway. It is also apparent that such apparatus involves novel and improved means for providing a substantially uniform Warning period of operation of a highway crossing signal when a train approaches the crossing, irrespective of the speed of the train.

Although I have herein shown and described only a few forms of railway signal apparatus embodying my invention, it is understoodthat various changes and modifications may be made therein Within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, What I claim is:

1. In combination, a stretchof railway trackway and a trafiic controlling device located in said trackway, a train to travelsaid track, means carried on said train for transmitting to the trackway oscillations modulated in accordance with the train speed, means in the trackway receiving said oscillations, and means jointly governed by the position of said traininsaid trackway and by the received oscillations for selec, tively controlling said trafiic controlling device to establish a substantially uniform time of operation of such device upon the approcah of a train regardless of the train speed.

2. In combination with a stretch of railway track, a trafilc controlling device located in the wayside, means responsive to a train on said track for controlling said signal,.and means gov erned by the position of said train on said stretch and responsive to energy applied by said train to the trackway for controlling said first-mentioned means to provide a substantially uniform time interval of operation of said device when a train approaches thereto.

3. In combination, a stretch of railway track adapted to be supplied with energy having a characteristic dependent upon the speed of a train traveling said trackwaysidemeans receiving energy fromsaid track, means operated by said-received energy and selectively responsive to the characteristics of said received energy, means responsive to the position of said train onsaid stretch and'a' trafiic controlling device in the wayside selectively controlled jointly by said energy responsive andpos'itionresponsive means to provide a substantially uniform interval of operation of said device. g I

.4. In combination, astretchofrailway track,

a train to travel said stretch provided with means for supplying to the rails thereof energy having a frequency proportional to the speed of said train, means in the wayside of said track receiving said energy, a relay operated by said received energy at a rate corresponding to the frequency of such energy, means responsive to the position of said train in said stretch, a signal device in the Wayside of said track, and means jointly governed by said train position responsive means and by said relay for controlling said signal to provide a substantially uniform operating interval regardless of the train speed.

5. In combination, a stretch of railway track, a train to travel said track and provided with means for supplying to said stretch energy having a frequency proportional to the speed of said train, means in the wayside of said track for receiving said energy when said train occupies said stretch, means operated by said received energy and selectively responsive to the frequency thereof, means responsive to the position of a train on said stretch, a signal in the wayside, and means jointly controlled simultaneously by said frequency responsive and said train position responsive means for controlling said signal to establish operation thereof when said train reaches one or another of a plurality of positions on said stretch dependent upon the speed of said train.

6. In combination with a stretch of railway track having a track circuit and a signal and means governed by said track circuit for establishing control over said signal when said circuit is occupied, a train to travel said track and having means for impressing on the trackway, energy having a frequency proportional to the train speed, means in the wayside receiving said energy, means operated by said received energy and selectively responsive to the frequency of said energy, and means governed by said last-mentioned means for at times preventing control of said signal by said track circuit means.

7. In a highway crossing signal control system for a stretch of railway track intersected by a highway and having a plurality of track circuits successively entered by a train approaching the intersection, said system comprising a highway crossing signal and means governed by said track circuits for causing operation of said signal, the

combination comprising means on a train traveling said track for impressing on the trackway energy having a frequency proportional to the train speed, means receiving said energy from the trackway and selectively responsive to the frequency of such energy, and means governed by said last-mentioned means for at times preventing said track circuit means from, causing operation of said signal until said train occupies one or another of said track circuits depending upon the frequency of current applied to the rails.

8. In combination, a stretch of railway track divided into a plurality of successive adjoining track sections, a control device operable to one or another of a plurality of positions according as a train occupies one or another of said plurality of track sections, means for applying to the rails of said trackway energy having a frequency proportional to a condition, means for receiving said energy from the trackway, an operating relay operable by said received energy at a rate proportional to the frequency of said energy, a chain of counting relays including an impulsing relay, means governed by said operating relay for supplying energy to said relay chain for causing op- 5 eration thereof, and means governed by said con trol device in accordance with its position for conditioning said relay chain to cause said impulsing relay to operate at a rate having one or another of a plurality of ratios to the rate of operation of said operatingrelay.

9. In combination, a stretch of railway track divided into a plurality of successive adjoining track sections, a control device operablgto one or another of a plurality of positions according as a train occupies one or another of said plurality of track sections, means for applying to the rails of said trackway energ having a frequency proportional to a condition, means for receiving said energy from the trackway, an operating relay operable by said received energy at a rate proportional to the frequency of said energy, a chain of counting relays including an impulsing relay, means governed by said operating relay for supplying energy to said relay chain for causing operation thereof, means governed by said control device in accordance with its position for conditioning said relay chain to cause said impulsing relay to operate at a rate having one or another of a plurality of ratios to the rate of operation of said operating relay, means operated by said impulsing relay and selectively responsive to the rate of operation of such relay, and a signal governed by said last mentioned means.

10. In a railway traffic controlling system, in combination, a source of ener y, means for alternately modulating the output of said source at first one and then another frequency of modulation, means governed by a condition for varying the rate at which said energy is alternately modulated, means receiving said modulated energy, a first relay energized from said receiving means when said energy is modulated at said one modulation frequency, a second relay energized from said receiving means when said energy is modulated at said other modulation frequency, said relays being provided with slow releasing characteristics selected to maintain both relays picked up when said energy is alternately modulated at a rate above a predetermined rate, a trafiic controlling device, means for operating said device, and means governed by said two relays for at times preventing operation of said device by said operating means.

11. In a railway traflic controlling system, in combination, a source of energy, means for alternately modulating the output of said source at first one and then another frequency of modulation, means governed by a condition for varying the rate at which said energy is alternately modulated, means receiving said modulated energy, a first relay energized from said receiving means when said energy is modulated at said one modulation frequency and having a make-before-break contact arrangement comprising a front contact and a back contact and a bridging member which engages both said front and back contacts when the armature of said relay operates from its released to its attracted position, a second relay and a third relay, an energizing circuit for a winding of said second relay comprisin a source of current and said make-before-break contact and a back contact of said third relay, a circuit in cluding a front contact of said second relay or a front contact of said third relay for energizing another winding of said second relay from said receiving means when said energy is modulated at said one modulation frequency, a circuit, including a front contact of said second relay or a front contact of said third relay, for energizing said third relay from said receiving means when said energy is modulated at said other frequency, said second and third relays being provided with slow releasing characteristics selected to maintain both relays picked up when said energy is alternately modulated at a rate above a predetermined rate, and a traific controlling device controlled by means rendered effective when both said second and third relays are picked up.

12. In a railway trafiic controlling system, in combination, a source of energy, means for alternately modulating the output of said source at first one and then another frequency of modulation, means governed by a condition for varying the rate at which said energy is alternately modulated, means receiving said modulated energy, a first relay energized from said receiving means when said energy is modulated at said one modulation frequency and having a make-before-break contact arrangement comprising a front contact and a back contact and a bridging member which engages both said front and back contacts when the armature of said relay operates from its released to its attracted position, a second relay and a third relay, an energizing circuit for a winding of said second relay comprising a source of current and said make-before-break contact and a back contact of said third relay, a circuit including a front contact of said second relay or a front contact of said third relay for energizing another winding of said second relay from said receiving means when said energy is modulated at said one modulation frequency, a circuit, including a front contact of said second relay or a front contact of said third relay, for energizing said third relay from said receiving means when said energy is modulated at said other frequency, means effective at times to provide said second and third relays with slow releasing characteristics selected to maintain both relays picked up when said energy is alternately modulated at a rate above a predetermined rate, and a trafiic controlling device controlled by means-at times rendered effective by said second and third relays.

13. In combination, a stretch of railway track divided into a plurality of successive adjoining track sections, a control device operable to one or another of a plurality of positions according as a train occupies one or another of said plurality of track sections, means for applying energy from a source to the trackway of said stretch, means for alternately modulating the output of said source at first one and then another frequency of modulation, means governed by a condition for varying the rate at which said energy is alternately modulated, means receiving said modulated energy, a first relay energized from said receiving means when said energy is modulated at said one modulation frequency and having a make-before-break contact arrangement comprising a front contact and a back contact and a bridging member which engages both said front and back contacts when the armature of said relay operates from its released to its attracted position, a second relay and a third relay, an energizing circuit for a winding of said second relay comprising a source of current and said make-beforebreak contact and a back contact of said third relay, acircuit including a front contact of said second relay or a front contact of said third relay for energizing another winding of said second relay from said receiving means when said energy is modulated at said one modulation frequency, a circuit, including a front contact of said secand relay or a front contact of said third relay,

for energizing said third relay from said receiving means when said energy is modulated at said other frequency, means effective at times to provide said second and third relays with slow releasing characteristics selected to maintain both relays picked up when said energy is alternately modulated at a rate below a predetermined rate, and a traffic controlling device controlled by means rendered effective when both said second and third relays are picked up.

14. In combination, a stretch of railway track divided into a plurality of successive adjoining track sections, a control device operable to one or another of a plurality of positions according as a train occupies one or another of said plurality of track sections, means for applying energy from a source to the trackway of said stretch, means for alternately modulating th output of said source at first one and then another frequency of modulation, means governed by a condition for varying the rate at which said energy is alternately modulated, means receiving said modulated energy, a first relay energized from said receiving means when said energy is modulated at said one modulation frequency, a transformer having a primary winding supplied with unidirectional energy over a front contact of said first relay, a second relay having an energizin circuit supplied with energy of one relative polarity caused to be induced in a secondary winding of said transformer, a third relay, another energizing circuit, including a front contact of said second relay and a back contact of said third relay, for energizing said second relay from said receiving means When said received energy is modulated at said one modulation frequency, a circuit for energizing said third relay by current having the opposite relative polarity caused to be induced in said transformer, another circuit, including a back contact of said second relay and a front contact of said third relay, for energizing said third relay from said receiving means when said received energy is modulated at said other modulation frequency, said transformer and second and third relays being proportioned so that when said first relay operates at a rate above a predetermined rate the energy output of said transformer is insuflicient to pick up either said second relay or said third relay, and a tra-filc controlling device controlled by means rendered effective when both said second and third relays are picked 15. In a highway crossing signal control system for a stretch of railway track intersected at grade by a highway and provided With a plurality of track circuits successively entered by a train approaching the intersection, said system comprising a highway crossing seignal at said intersection and means controlled by each of said track circuits for causing operation of said signal, the

combination comprising means on a train traveling said track for impressing on the trackway, energy having a frequency proportional to the train speed, means receiving said energy from the trackway, a relay operated by such received energy at a rate corresponding to the frequency of said received energy, means operable by said relay for at times preventing operation of said signal by said track circuit means when said received energy has a frequency above a given frequency, and other means operable by said received energy for preventing operation of said signal by said track circuit means when said received energy has a frequency corresponding to a very low or zero speed of the train.

16. In combination, in a system provided for a stretch of railway track for controlling highway crossing signals protecting the intersection of such stretch with a highway, of means on a vehicle traveling said track for supplying the track rails of said stretch with electrical energy modulated in accordance with the vehicle speed, and means in the trackway of said stretch jointly governed by the position of the vehicle in said stretch and Joy said modulated electrical energy for selectively controlling said highway crossing signals, whereby to establish a substantially uniform time interval of operation of the signals irrespective of the speed of the vehicl traveling said stretch.

17. In combination with a stretch of railway track, a traffic controlling device disposed in the wayside, a train to travel said track and having means for supplying the trackway with ener y having characteristics reflecting the speed of the train, means in said trackway selectively responsive to the characteristics of the energy supplied from said train to said trackway, a plurality of means each responsive to the presence of said train according to its position on said track for controlling said device, and means jointly controlled by said energy responsive and said train responsive means for providing upon the approach of a train a substantially uniform operating period for said trafiic controlling device irrespective of the train speed.

PAUL N. BOSSART.

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