US2128211A - Railway signaling system - Google Patents

Description

Aug.23,1938. TNLJUDGE RAILWAY SIGNALING SYSTEM 2 Sheets Sheet 1 Filed Sept. 25, 1956 INVENTOR ATTORNEY Aug. 23, 1938. T. J. JUD GE RAILWAY S IGNALING SYSTEM Filed Sept. 25, 1956 2 Sheets-Sheet 2 INVENTOR W ATTORINEY Patented Aug. 23, 1938 UNETED STATES gPATEN'i' OFHQE RAILWAY SIGNALING SYSTEM ter, N. Y.

Application September 25, 1936, Serial No. 102,557

12 Claims.

This invention relates in general to railway signaling systems, and more particularly to an absolute permissive block signaling system employing coded track circuits for controlling wayside and/ or cab signals.

In general, it is proposed in accordance with the present invention to provide an absolute permissive block signaling system employing coded track circuits arranged to effect the control of train movements in both directions through a portion of single track in the usual manner, but without the use of control line circuits. More specifically, it is proposed to provide in each block a track circuit associated with each direction of movement so arranged that the two track circuits are independent of each other due to the distinctive character of their energization. It is then proposed to independently code or modulate the distinctive energization of each of these track circuits in a manner to condition wayside and/or cab signals for each direction of train movement in accordance with forward trafiic conditions.

Other objects, purposes and characteristic features of the present invention will be obvious as the description thereof progresses, during which references will be made to the accompanying drawings, in which- Fig. 1 and Fig. 2 show in a diagrammatic and conventional manner the apparatus and circuits 3 of a portion of an absolute permissive block signaling system arranged in accordance with the present invention. These two figures show adjacent portions of the railway track and are intended to be placed end to end with Fig. 2 at the right.

In the accompanying drawings, a single track portion of a railway has been shown as divided by insulating joints J into track sections or blocks l, 2 and 3, and it is to be understood that this is a portion of single track wherein trains normally move in either direction and passing sidings or portions of double track will be provided at spaced intervals which have not been shown.

The present system employs the usual absolute permissive block feature wherein two or more trains are permitted to follow each other through the portions of single track between these passing sidings, but a train is prevented from entering any such single track portion which is occupied by a train moving in the opposite direction. It is believed that a description of the portion of the present signaling system associated with the typical intermediate portion of single track comprising blocks I, 2 and 3 will be sufllcient for an understanding of the present invention, and inasmuch as the apparatus associated with each of these blocks is identical, the same reference characters have been assigned to the like pieces of apparatus with an exponent corresponding to the particular block with which it is associated.

It may be briefly stated that in the present 5 system each block is provided with two superimposed alternating current track circuits, these two circuits being energized with distinctively different frequencies and reversely arranged with respect to the ends of the track rails to which the energy is applied, the track rails of course forming common electrical conductors for both circuits. More specifically, alternating current energy of one frequency is connected to one end of the rails of each block and alternating current 15 energy of a distinctively different frequency is connected to the other end of these same track rails of each block, or as shown on the drawings, the left hand end of the rails of each block is connected through a transformer LTR to a power 20 line LP energized by an alternating current generator LG, while the right hand end of these rails of each block is connected through similar transformers RTR to another power line RP energized by an alternating current generator RG which supplies a different frequency of alternating current than generator LT. It is to be understood however that in the event it is not desirable to extend the power line wires LP and RP along the trackway, the two distinctive frequencies of alter- 30 nating current can be generated locally at each block from a battery or the like such as by vibrating reed contacts operating at distinctively different frequencies and arranged to interrupt the energization of the primary of transformers LTR and RTR respectively, all in accordance with well recognized principles.

The particular frequency applied to each end of each block is conducted through the track rails in series to operate a track relay at the other end, which track relay is rendered nonresponsive to the different frequency applied at the same end. More specifically, the energy applied to the left hand end of each section through transformers LTR is conducted through the rails in series to the primary of a tuning transformer RTA connected across the right hand end of the rails, the secondary of this transformer RTA being connected to the primary of a second tuning transformer R'I'B through a tuning condenser RC, whereby the secondary of the transformer RTB is only effectively energized by the alternating current of the frequency supplied by transformer LTR and is not eifectively energized by the alternating current of the frequency supplied by transformer RTR. Similar transformers LTA and LTB and condenser LC are employed at the left hand end of each section, but the condenser LC as indicated is of a capacity different from condenser RC so that the secondary of transformer LTB is only effectively energized by the alternating current of the frequency supplied by transformer RTR.

The secondary of transformer RTB energizes a direct current track relay RT through a full-wave rectifier RR and in a similar manner the secondary of transformer LTB energizes a second direct current track relay LT through a full-wave rectifier LR. In this manner, the track relay RT is controlled only by the current from the transformer LTR and track relay LT and is controlled only by the current from the transformer RTR, and inasmuch as the current from both transformers LTR and RTR flows through the track rails in series, both of these track relays LT and RT will be dropped by a train shunting the associated track section.

In order to communicate the traffic conditions from block to block without the use of control line circuits, the alternating current energization of each of the two track circuits for each of the blocks is individually modulated or coded in accordance with traffic conditions in a direction individually associated with each of thesetwo circuits. In other words, the secondary of transformer LTR is connected to the track rails through a back contact of a code repeater relay LCP which is operated in synchronism with either contact C or CWO of a modulator or coder C, and. in a similar manner, the secondary of transformer RTR is connected to the track rails through a back contact of a code repeater relay RCP likewise operated in synchronism with either of contacts CV5 or C188 of a similar coder C.

The contacts C75 and CESB may be operated in any suitable manner, but for convenience these contacts have been diagrammatically illustrated as operated'by the usual form of mechanical coding means wherein a continuously energized motor M mechanically operates contacts C75 at the rate of '7 5 times per minute and also operates contact C 86 at the rate oftimes per minute. The code repeating relays LCP and RCP are at times continuously deenergized, and at other times operated by either contact C15 or contact CIBI] as selected by traffic conditions as will be later described.

It will now be clear that when the code repeating relays LCP and RCP are operating to interrupt their associated track circuits at either the '75 or the 180 code rate, the respective track relays LT and RT are operated in synchronism therewith, and consequently the rate of operation of the armatures of relays LT and RT as affecting certain decoding means determined the respective forward trafiic conditions. The decoding means controlled by both track relays LT and RT is identical and comprises respective transformers LTD and RTD having a center tapped primary connected to one side of a direct current source of energy while the two extreme ends are alternately connected to the other side of this source of energy by front and back contacts of the respective track relay LT or RT. In this manner, alternating current isinduced in the secondaries of transformers LTD and RTD which is proportional in frequency to the rate of operation of the respective track relays LT and RT.

Decoding transformers LTE' and RTE are provided having primary windings connected across the secondary of transformers LTD and RTD respectively through condensers LCE and RCE respectively, which condensers are of a value selected to resonate or to permit an effective alterhating current voltage in the secondary of transformers LTE and RTE only when the frequency of alternating current from the secondary of transformers LTD and RTD is provided by the 180 rate of operation of the track relays LT and RT respectively. Similar tuning transformers LT? and RTF are also connected across the secondary of transformers LTD and RTD respectively but through different capacity condensers LCF and RCF whereby an effective alternating current voltage is permitted in the secondary of transformers LTF and RTF only when the frequency of alternating current from the secondary of transformers LTD and RTD is produced by either the 180 code rate or the 75 code rate of operation of the respective track relays LT and RT. The alternating current produced in the secondary of transformers LTE and RTE energize respective direct current relays LE8!) and RES!) through respective full-wave rectifiers LRE and RRE, and likewise the alternating current produced in the secondaries of transformers LTF and RTE energize respective direct current relays Ll? and Rl'5 through respective full-wave rectifiers LRF and RRF.

.The track relays LT and RT also control the energization of respective slow releasing track repeating relays LT? and RT? whereby these repeating relays remain picked up either when the associated track relay is continuously energized or is operating at the 75 or 180 code rate, but drop when the associated track relay is continuously deenergized. It will now be clear that when the track relays are continuously energized, the associated repeating relays will be picked up but both the associated 180 and 75 decoding relays will be dropped; and when the track relays are operated at the 180 code rate, the respective repeating relays and both the respective 180 and 75 decoding relays will be picked up; but when operating at the '75 code rate, the respective '75 decoding relays and the respective repeating relays only will pick up; and obviously when the track relays are continuously deenergized due to a train shunt for example, all of these'relays will be dropped.

A direction stick relay LS and RS is also associated with each block, which stick relays are made slow releasing for a purpose later described. These directional stick relays LS and RS are selectively energized according to the direction of a train movement over the associated portion of track, or that is, relay LS is picked up by an east bound train movement and relay RS is picked up by a west bound train movement.

The present wayside equipment may be employed to control either wayside or cab signals or both, and consequently the method of effecting the control of both types of signals has been shown in the accompanying drawings, although it is to be understood that train movements are adequately protected by either type and consequently either wayside on cab signals may be employed alone and the other omitted from the system.

The wayside signals have been illustrated as the three indication multiple unit color light type although other types may be equally well employed, and the change in the controlling circuits necessary when using these other types will be obvious to those skilled in the railway signaling art. The

wayside signals ES govern traflic in east bound direction through their associated block and are jointly controlled by the associated decoding relays LI8I! and L15, and likewise the wayside signals WS govern trafic in a west bound direction and are jointly controlled by the decoding relays RIBIJ and R15.

A west bound train represented by wheels and axle 5 has been shown as occupying section 3 of Fig. 2, and a cab signal system which may be employed in the present system has been shown diagrammatically as carried by such train, but it is to be understood that the particular arrangement of such car carried equipment is shown merely for an example and that various other well known types of car carried signal controlling systems can equally well be employed.

In Fig. 2, the car carried equipment is illustrated as comprising receiver coils 6 and 1 carried on the train above the rails and in front of the first pair of wheels and axle whereby current is induced in these receiver coils by the alternating current flowing in the track rails from transformer LTR A means similar to that employed in the wayside equipment may be used to tune the circuit of the receiver coils to the particular frequency of alternating current received from the rails, or that is, the receiver coils 6 and 1 are connected in series to the primary of a tuning transformer 8, the secondary of transformer 8 being connected to the primary of a second transformer 9 through a condenser I0 whereby the secondary of transformer 9 is only effectively energized by the alternating current of the frequency provided by transformers LTR when the train is traveling in a west bound direction.

However, when the same train is traveling in an east bound direction, the alternating current affecting the receiver coils will be of a different frequency supplied by transformers RTR, and consequently it is contemplated that a manually operable switch II may be provided which in this case of an east bound direction of movement will be moved from its west bound position W to its east bound position E to connect a condenser I2 in multiple with condenser I I], and thus tune this circuit to the frequency of transformer RTR. However, it may be considered sufficient in some applications to arrange the tuning of the car carried receiver circuit sufiiciently broad so that the secondary of transformer 9 will be effectively energized by the frequency of current received from either transformers LTR or RTR, and in such case the switch I I and condenser I2 may be omitted.

The remaining portion of the car carried equipment may be constructed in accordance with the usual practice and has been illustrated diagrammatically as an amplifying means A amplifying the current from the secondary of transformer 9 to a value which can operate a master relay MR. The master relay MR, then operates in synchronism with the operation of the particular code repeating relays LCP or RCR the same as the track relays LT and RT, and consequently a decoding means similar to that employed in the wayside arrangement may be employed.

This car carried decoding means comprises a transformer I4 operating the same as transformer RTE in the wayside equipment but from a contact of the master relay MR rather than a track relay RT. The output of transformer I 4 then energizes a decoding relay D I 80 through rectifier I5, tuning transformer I6 and condenser I6 only when the 180 code rate is received from the rails,

and the output of transformer I4 likewise energizes a decoding relay D15 through rectifier I9, transformer 20 and condenser 2| when the or the 180 code rate is received, all in a manner which may be understood from the previous description of the wayside decoding equipment.

Having now pointed out the essential elements of the present system, it is believed that the usefulness and the various interrelated functions of the apparatus and circuits of the present embodiment will be more readily understood by vfurther description being given from the standpoint of operation.

Operation Considering that the illustrated west bound train represented by wheels and axle'5 is the only train traversing the portion of the railway system under consideration, this train then receives a clear or green cab signal as well as a green wayside signal. In other words, sections I and 2 being unoccupied, the code repeating relay LCP is con" nected to contacts CI of coder C through front contact 25 of relay RTP and front contact 26 of relay R15 thereby operating contact 21 of relay LCP to impulse the energization of section 2 from transformer LTR. at the rate of 180 times per minute which picks up the track repeater relay RTP at front contact 32 of relay RT and the decoding relays R15 and RIBIl are also energized by the operation of contact 33 of relay RT The green signal lamp G of signal WS is then ener' gized through front contact 28 of relay R15 and front contact 29 of relay RI8U In a like manner the green light G at signal WS is energized through front contacts 48 and 49 of relays R15 and RI 35 respectively, and at all west bound signals as far as the next passing track at the left of the illustrated portion of single track, a green signal will likewise be displayed.

The present train while occupying section 3 also receives a green cab signal due to the fact that code repeater relay LCP is connected to contact CISQ of coder C2 through front contact Si! of relay RTF and front contact ill of relay R15 thereby operating contact 60 to impulse the energization of section 3 from transformer LTR at the 180 code rate. The reception of these 180 code impulses by receivers 6 and 'I then operates contact I3 of the master relay ME to effect the energization of relays D15 and DI Bil as previously described, and the green cab signal G is then energized through front contacts 34 and 35 of relays D15 and DISI] respectively. The east bound signal ES however, properly displays a red or danger indication due to the continuous deenergization of track relay LT caused by the occupancy of section 3, thus dropping relay LTP at open front contact 38, and dropping relays LI8IJ and L15 due to the inaction of contact 31, and the red signal lamp R of signal ES is then energized through back contact 38 of relay L15 The LTP and L15 relays and the east bound stick relay LS being deenergized, obviously prevents energization of the code repeater relay RCP thus continuously supplying the right hand end of section 2 with alternating current from transformer RTR through back contact 39 whereby track relay LT is continuously energized to drop the decoding relays LIBil and L15 by the inaction of contact ill, and the red lamp R of the east bound signal E6 is then energized through back contact M of relay L15 Likewise the deenergization' of the decoding relay L and the east bound stick relay LS prevents the energization of the code repeating relay RCP thussupplying continuous energy to the right hand end of section i from transformer RTE through its back contact ill, and it will be clearthat the right hand end of each section in advance of the Considering now that the present train in Fig.

2 passes the insulating joints J and enters section 2, it will be clear that track relay RT will now be continuously deenergized to drop the decoding relays Rl'5 and BMW and energizes the red signal lamp R at signal WS through back contact 23 of relay BT5 The car-carried receivers S and 7 however, DOW receive current llTlpulses of the 180 coderate from transformer LTR which obviously maintains the green cab signal G energized the same as while occupying block 3.

When the present train is passing the insulating joints J separating blocks 2 and 3, it will be clear that the track repeating relays RTP and LTP will both be deenergized by contacts 32 and 35 respectively, and although these track repeater relays are necessarily somewhat slow releasing the decoding relays are necessarily still slower to release due to the shunt across their windings provided by the associated full-wave rectifiers. Consequently the track repeater relay RTP will drop before the decoding relay EH3 drops, and a circuit is then momentarily completed to pick up the west bound stick relay RS which circuit may be track from back contact 42 of relay RTP back contact 43 of relay LTP front contact M of relay RS55 through the windings of relay RS to hen the stick relay RS has picked up, it will be clear that relay R15 subsequently drops, and a stick circuit is then completed through front contact 45 of relay RS and back contact 4 3 of relay R775 to hold relay RS in its picked up condition, the stick relay RS being sufficiently slow releasing to retain its armature in its attracted position during the momentary interruption of .its energization caused by the movement of contact 44.

The entrance of the present train into block it obviously disconnects the code repeating relay LCP from the contact ClSii of the coder C at front contacts 30 and 3d of relays RTP and R75 respectively, but when the west bound stick relay Rs picks up, the code repeating relay LCP is connected to contact C15 of the coder C through front contact 66 of the relay RS In this manner the entrance of the present train into section '2 changes the energization of section from transformer L'TR, from the 180 code rate to the '75 code rate.

Now considering that the present train traverses section 2 and enters section I of Fig. 1, it will be clear that track relay RT will drop and the decoding relays R35 and R586 will be deenergized due to the inaction of contact iii, thus changing the indication at signal WS from a green to a danger or red indication by energizing the red lamp B through back contact 48 of relay R15 Likewise when the present train passes the insulating joints J separating sections l and 2, the dropping of the track repeater relay RJP before the dropping of the decoding relay R15 establishes a pick up circuit for the west bound stick relay RS which circuit may be traced from back contact 50 of relay RTP back contact 5! of relay LTP front contact 52 of relay R15 through the windings of relay RS to A similar stick circuit is completed upon the subsequent dropping of relay R15 to hold up relay RS through its stick contact 53, and the dropping of relays RTP and R15 disconnected the code repeating relay LCP from the Cl code contact at open front contacts 25 and 26 respectively, and the picking up of the stick relay RS connects the LCP relay to the contact C15 of the coder C through its front contact 55.

The coder repeating relay LCP now interrupts the energization of section 2 from transformer LTR. at the 75 code rate by its contact 2?, which in an obvious manner picks up relay R75 in Fig. 2 but allows relay RIBEI to remain deenergized. A caution signal indication is then displayed at signal WS by energizing the yellow signal lamp Y through front contact 28 of relay R 55 and back contact 29 of relay REBU The picking up of the decoding relay R15 ob viously releases the west bound stick relay RS at contact M inasmuch as the repeating relays RTP and LTP are now both picked up, and the code repeating relay LCP is disconnected from coder contact C75 at open front contact 46 of relay RS and is again connected to coder con tact C980 through front contacts 30 and M of o relays RTP and R75 respectively. The energization of section 3 from transformer LTRF' is now interrupted at the code rate by contact 6! of relay LCP which in an obvious manner provides a clear west bound signal at the entrance to section 3, which signal hasrnot been shown in the accompanying drawings.

In this manner, it will be seen that a train traversing a portion of single track picks up the stick relays associated with its particular direc tion of travel to allow a second train traveling in the same direction to follow at a safe distance in the rear of this first train. However, it may be seen that the stick relays associated with the opposite direction of travel do not pick up, or that is, considering the present west bound train movement, it is evident that the entrance of the present train into section 3 before section 2 causes the relay L75 to be deenergized before the pick up circuit for stick relay LS is closed at back contacts 32 and 3 3 of relays RTP and LTP respectively.

It will of course be clear that the three different cab signal indications are displayed on the train in the same manner as at the wayside signals, or that is, a green cab signal G is energized as previously described by the reception of the 180 code rate of impulses by the receivers 6 and i, while the reception of the '75 code rate of impulses drops relay Ditii and completes an energizing circuit for the yellow cab signal Y through front contact 34 and back contact 35 of relays D15 and Dita respectively, and the reception of either uninterrupted alternating cur rent or the reception of no current by the receivers B and l obviously deenergizes both relays D'l5 and D589] to energize the red signal lamp R through'back contacts 34 and 55 of relays D'l5 and D! 89 respectively.

The operation of the apparatus of the present system associated with an east bound train movement is similar in every respect to the operation just described of the apparatus associated with a west bound movement, and consequently it is believed unnecessary to describe such operation in detail. The stick relays LS are of course picked up by an east bound train movement to allow east bound trains to follow in the same manner that relays RS were picked up by a west bound movement, and the west bound wayside signals WS then all display a stop indication in a similar manner during such an east bound movement. Likewise during an east bound movement of the illustrated train, the switch ii is moved to position E as previously described whereby to tune the receiver circuit to the frequency of alternating current supplied by transformer RTR, and otherwise the car carried equipment functions the same as during a west bound movement.

An absolute permissive block signaling system has thus been provided wherein three-indication wayside and/or cab signals are controlled without the use of control line circuits to permit following train movements through portions of single track but to prevent a train from entering a portion of single track which is occupied by a train moving in the opposite direction. The feature of the present invention permitting such double direction operation without control line circuits in, the arrangement of superimposed alternating current track circuits. These track circuits, although each having the track rails as common conductors are in effect two separate and distinct circuits, each circuit being individually coded and associated with one particular direction of travel. These circuits are also reversely arranged with respect to the ends of the track rails towhich energy is applied so that each direction of train movement progresses toward the source of energy in the circuit associated with that direction of movement, thereby permitting cab signal equipment to be properly controlled during each direction of movement and enabling traflic conditions at each block to be transmitted to the rear blocks in each direction by the respective circuit.

Another important feature of the present system is the method of effecting a stop indication at all signals governing traffic in a direction opposite toan established train movement. This method consists in supplying uninterrupted alternating current to the track circuit of each block associated with such opposite direction of traffic, which uninterrupted alternating current effects a stop indication at all signals controlled thereby. A particular advantage of this feature is that the track circuits are still able to detect between the occupied and the unoccupied condition of their associated blocks, and consequently other apparatus such as highway crossing signals may be conditioned directly by the track relays or the track repeater relays of these blocks in the usual manner.

The above rather specific description of one form of the present invention has been given solely by way of example, and is not intended in any manner whatsoever in a limiting sense. It is to be understood that various modifications, adaptations and alterations may be applied to meet the requirements of practice, without in any manner departing from the spirit or scope of the invention, except as limited by the appended claims.

What I claim is:

1. In a single track railway signaling system, a plurality of insulated track sections, means for applying alternating current of a first frequency to one end of each section, means for applying alternating current of a second frequency to the other end of each section, a track relay at said one end of each section responsive only to the alternating current of the second frequency, a track relay at said other end of each section responsive only to the alternating current of the first frequency, means for distinctively coding the alternating current of the first frequency in accordance with traflic conditions in one direction, means for distinctively coding the alternating current of the second frequency in accordance with trafiic conditions in the other direction, and decoding means individually controlled by each track relay and distinctively responsive to the coding of the associated frequency of alternating current.

2. In a single track railway signaling system, a plurality of insulated track sections, means for applying alternating current of a first frequency to a first end of each section, means for applying alternating current of a second frequency to the second end of each section, a track relay at said first end of each section responsive only to the alternating current of said second frequency, a track relay at said second end of each section responsive only to the alternating current of said first frequency, means for distinctively coding the alternating current of said first frequency in accordance with trafiic conditions in one direction, means for distinctively coding the alternating current of said second frequency in accordance with traffic conditions in the other di rection, decoding means individually controlled by each track relay and distinctively responsive to the coding of the associated frequency of alternating current, and wayside signals controlled by the decoding means.

3. In a railway signaling system, a portion of single track divided into insulated track sections, means for simultaneously applying differently characterized energy to opposite ends of each section, a track relay at each end of each section responsive only to the energy applied to the opposite end, means for individually impulsing the energy applied to each end of each section to form codes according to trafiic conditions, and decoding means operated by each track relay for distinctively responding to said codes.

4. In a railway signaling system, a portion of single track divided into insulated track sections, means for simultaneously applying differently characterized energy to opposite ends of each section, a track relay at each end of each section responsive only to the energy applied to the opposite end, means for impulsing the energy applied to one end or to the other end of each section in accordance with the direction of movement of a train through the portion of single track, and signal controlling means at each section distinctively conditioned by the impulsing of the energy applied to the associated section.

5. In a railway signaling system, a portion of single track divided into insulated track sections, means for applying interrupted alternating current of one frequency to the exit end of each section for each direction of train movement thereover, means for simultaneously therewith applying uninterrupted alternating current of a different frequency to the entrance end of each section for each direction of train movement thereover, and signaling means controlled by said interrupted alternating current to display a clear indication and controlled by said uninterrupted alternating current to display a stop indication.

6. In a railway signaling system, a portion of single track divided into a plurality of track sections, means for simultaneously applying alternating current energy of distinctively different frequencies to opposite ends of each section, means for coding the energy applied at each end of each section in accordance with traffic conditions in the two sections respectively adjacent thereto, and signal controlling means governed by the coding of the energization of each section.

'7. In a railway signaling system, a portion of single track divided into track sections, means for simultaneously applying alternating current energy of different frequencies to opposite ends of each section, means for coding the energy applied to each end of each section in accordance with traflic conditions throughout the sections respectively adjacent to each end, wayside signals responsive to the coded energy, continuous inductive cab signaling means, and selective means for rendering the cab signaling means responsive to one frequency or to the other frequency of the alternating current energy applied to the sections in accordance with the direction of travel.

8. In combination, a stretch of railway track divided into sections, a first source of alternating current, a second source of alternating current of a different frequency than the first source, a code following track relay at one end of each section responsive to the first source of alternating current only, a code following track relay at the other end of each section responsive to the second source of alternating current only, means for supplying impulses of alternating current to each section from one of said sources of alternating current in accordance with the direction of a train movement through the stretch of track, means for supplying continuous alternating current tov each section from the other source of alternating current, signals at each end of each section governing traffic in opposite directions, and signal controlling means controlled by each track relay for effecting a most restrictive indication when the associated track relay is energized by continuous alternating current and for effecting lesser restrictive indications when energized by impulses of alternating current.

9. In combination, a stretch of railway track divided into track sections, each bound and west bound signals at the ends of each section, an east source of alternating current energy of one frequency at the east end of each section, a west source of alternating current energy of a different frequency at the west end of each section, a track relay at the east end of each section I responsive only to the frequency of alternating current at the west end of the section, a track relay at the west end of each section responsive only to the frequency of alternating current at the east end of the section, means operable to intermittently connect the east source of alternating current to the east end of each section to form codes distinctive of west bound traffic conditions, means operable to intermittently connect the west source of alternating current to the west end of each section to form codes distinctive of east bound trafi'ic conditions, code responsive means controlled by the track relay at the east end of each section for governing the west bound signals, and code responsive means controlled by the track relay at the west end of each section for governing the east bound signals.

10. In combination, a stretch of railway track divided into track sections, an east source of a1- ternating current energy of one frequency applied at the east end of each section and simultaneously a west source of alternating current energy of a different frequency at the west end of each section, means operable to intermittently connect the east source of alternating current to the east end of each section to form codes distinctive of east bound traffic conditions contemporaneously therewith and means operable to intermittently connect the west source of alternating current to the west end of each section to form codes distinctive of west bound traffic conditions.

11. In combination, a stretch of railway track divided into track sections, means for applying alternating current of different frequencies to opposite ends of each section, a track relay at each end of each section responsive only to the alternating current of the frequency applied to the opposite end, means controlled by the track relay at one end of each section for governing trafiic in one direction, and means controlled by the track relay at the other end of each section for governing traffic in the other direction.

12. In a railway signaling system, a portion of single track divided into a plurality of track sections, means for simultaneously applying alternating current energy of distinctively different frequencies to opposite ends of each section, means for coding the energy applied at each end of each section in accordance with traflic condi tions in the two sections respectively adjacent thereto, and cab-carried signal controlling means governed by the coding of the current energizing each section.

THOMAS J. JUDGE.

Images