US1504173A - wight - Google Patents

Description

Aug. 5, 1924. 1,504,173

S. N. WIGHT AUTOMATIC TRAIN CONTROL SYSTEM Filed Maych 1a. 1921 2 Sheets-Sheet 1 Aug. 5 1924.

S. N. WIGHT AUTOMATIC TRAIN CONTROL SYSTEM Filed March 18 941 2 Sheets-Sheet 2 {lllllllll Patented Aug. 5, 1924.

UNITED STATES 1,504,173 PATENT OFFICE.

SEDGWICK N. WIGHT, OF hOCHESTER, NEW YORK, ASSIGNO-R TO GENERAL RAILWAY SIGNAL COlYIPANY, OF GATES, NEV YORK. A. CORPDRATION OF NEW YORK.

AUTOMATIC TRAIN-CONTROL SYSTEM.

Application filed March 18, 1921.

To all whom may concern Be it known that I, SEnowicK N. WIGHT, a citizen of the United States, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Automatic T rain-Control Systems, of which the following is a specification.

This invention relates to automatic train control systems for single track railroads, and more particularly to the track equip ment and the controlling circuits of such a system.

On single track railroads protection must be provided for train movement in either direction, that is, protection for trains traveling in opposite directions toward .each other (opposing movements), and trains traveling in the same direction as on double track railroads (following movements). These and other requirements for single track operation of trains have been satisfied, so far as signal indication is concerned, by the type of automatic block signal system now commonly known as an absolute-perinissive-block system.

There are various types of train control systems employing ditl'erent forms of car apparatus and track devices, but in those types which operate in accordance with the principle of failure on the side oi? safety, the traclrway means is such that it is placed in the proceed or safety condition by the closing of a circuit or the like, and is auto matically changed to its danger or stopping condition when such circuit is broken.

The present invention i primarily directed toward providing an arrangement of circults and devices for use in connection with an A. P. B. system which will open and close the controlling circuits for the track de' vices of the train control system, in such a way that said track devices will coinn'umicate the desired impulses or influences to passing trains in proper co iormity with the signal indication. Other .specitic objects and advantages of the invention will appear hereinafter.

In the accompanyingdrawing, 1 is a diagrammatic view showing one arrangement of the signals in an absolute-permissive-block system;

Figs. 2 and dare simplified diagrammatic views of two arrangements of controlling circuits for the track element at a signal Serial No. 453,302.

cation, where there are oppositely located opposing signals;

Fig. 4 is a diagrammatic view of one typical form of car equipment, and illus trates the way in which it cooperates with the track element; and

Figs. 5, 6, and 7 are simplified diagrammatic'views showing other arrangements of controlling circuits for the track element, which are more particularly applicable to a signal location where there is only one signal.

The controlling circuits embodying the invention have been shown in the form which they will take in connection with the particular A. P. B. system disclosed in my prior Patent No. 1,294,736, dated Feb. 18, 191.9, but by simple modifications and adaptations readily apparent to those skilled in the art, the same principles may be applied to A. P. B. systems oi other specific forms. Since the detail construction and operation of the A. P. B. system of my prior patent is fully shown and disclosed in said patent, it will be suthcient, in order to obtain a clear understanding of the present invention, to explain this A. P. R'system merely in a general way, and without attempting to point out the detail construction, circuits and mode of operation.

Fig. 1 illustrates one arrangement of signals for an A. P. B. system. The stretch of single track (shown by a single heavy line) between two passing sidings X, is divided into track sections AB-C etc., in the usual way by insulated joints 2. Sig na ls, designated S to S are located at intervals along this stretch of single track, and .in the arrangement shown, these signals are arranged in pairs. The two signals S and S at each end of the stretch and controlling train movement into the stretch, are known as the absolute or starting signals, and are made distinguishable in some suitable way, as by the shape of the blade and marker lights, from the other signals, these starting signals, when in the stop position, signifying stop and stay. The other sig nals are permissive signals, and when in the stop position, signify that the train may proceed in accordance with certain prescribed rules, expecting to find another train or other obstruction ahead.

The ,sg'cncral scheme of operation of the P. B. system schematically illustrated. in

Fig. 1 is as follows: When a train enters the stretch of single track from either end, it causes all of the opposing signals to as sume the stop position, thereby blocking trains approaching in the opposite direction. As this train travels through the stretch of single track, these opposing signals are held in the stop position until passed by the train. The signals behind this train are caused to assume in turn, the stop, the caution, and the clear positions, so as to permit follov7- ing movements under signal protection the same as in double track block signal systems. The circuits and devices employed in obtaining this operation oi the signals are fully explained in my prior patent; and tor the purpose of describing the present invention, it is suilicient to note that the track between successive signals, as S -S is di vided into tWo track sections, il-l3, each. provided with a track battery (not shown) and a track relay 3, the track relays being located at the ends of the track sections nearest the signals, and that there is a polarized line relay L at each signal for controlling the position thereof.

In the present invention it is assumed that the track elements of the train control system are of the type which is caused to assume the inactive or proceed condition when a controlling circuit therefor is closed. and the active stopping condition when sai d circuit is opened, this circuit including a soru-ce of energy, or being merely a conducting path, according to the particular type of train control system. While various terms of trick elements may be employed in con nection With this invention, 1 have selected for illustration a track element Which acts inductively through an intervening air gap to influence suitable car apparatus. This track element produces its stopping eflect by virtue of its magnetic qualities. and may be said to be of the inert type. Referring to big. 4, this track element T shown coniprises a U-shaped iron core 4, with enlarged pole pieces 5, and is provided with a coil 0 on each leg, said coils being Wound and onnected in series so as to be cumulative in their effect when flux passes through said core.

The car element for cooperating with this particular form oi track element. comprises a similar ill-shaped iron core or yoke Y, with enlarged pole pieces 7, and is supported on the locomotive or other vehicle in any si able manner so as to pass directly over hie track element T. On one leg of the yoke is a coil or Winding 8. conveniently termed the primary coil; and on the other leg is another coil 9, conveniently termed the sec onclary coil. he primary coil 8 is encrgized by a battery 10, and to check the integrity of this energizing ircuit, a balanced relay ll This n is includedin said circuit.

relay R is provided with an armature L biased by an adjustable spring 12, \vl" is adjusted so as to balance the attraction erted on the armature When the normal cur rent flows. The armature 11 carries a head or" insulatin material which is disposed between movable contact springs or fingers liB-l/t cooperating with stationary contacts (indicated conveniently by arrows). It the battery 10 should depreciate, or the energizing circuit for the primary coil 8 break, the spring 12 overcomes the attraction of the relay and moves contact spr ng l Way from its iooperating lined contact thereby breaking the circuit which includes in series the springs 13l land their fixed contacts Likewis it the primary coil 8 should be short-circuited the current in the relay i1 increases above the normal and attracts the armature 11 in opposition to the spring 1), so as to move contact spring 13 out or en gageinent with its cooperating fixed contact. thereby 'lneaking the circuit.

The secondary coil 9 is connected to a relay ll which is constri'lcted the same as the relay il with such changes in the wind' or the like that may be desirable to obta n the required operating characteristics. relay R and the secondary coil are couuectco in series With a battery 15. which i .ciiierably has a low voltage. it this circuit becomes broken, or the secondary coil 9 short-circuited, the relay it opens contacts in the same way as above described. Also, it the normal current through said relay is increased or decreased by induced voltage in the secondary coil 9, the relay ll opens its (011i acts.

Any suitable term of train control apparatus may be governed by the relays and B; but since the type of this apparatus has no bearing upon the present invention, there is illustrated. a device K. in the term oi on elr-ictro-pneuinatic-valv which upon being deenergized may be used to vent the train pipe and apply the brakes at once. or set into operation speed control equipment or any other sui able train control mechanism. The device included in a no'mellv closed circuit energized by a battery l l6 ano. interrupted when the contacts of either oi the relays lt or il are opened.

i i hen the coils 6 oi tic track element T are open-circuited, the core l 0t this element presents in eilcct a dead magnetic loop for the yoke Y of the car element and when said car element passes over this magnetic loop, the reluctance of the partial magnetic circuit through said yoke is changed, thereby producii'ig a change in the in through the secondary coil 9. This change in flux induces in the secondary coil 9 an electromotivc-l orce, alternating in character, which alternately opposes and assists the voltage 01 the battery 1.5, thereby varying VI to the current in the relay It and causing it to open its contacts and decnergize the device K. If the coils 6 of the track element are in a closed circuit of low resistance, they serve to oppose or choke back the passage of flux through the core 4:, so that as the car element passes over said core, there is no appreciable change in the flux through the secondary coil 9, and the relay R is not operated.

Thus, if the coils 6 of the track element T are open-circuited, an impulse is transmitted to the passing vehicle which may be utilized in any desired way to control its movement; but if said coils are in a closed circuit, the vehicle may pass without receiving such an impulse. In other words, with the circuit through the coil 6 closed, the track element is in its safety or proceed position, and With this circuit open, said element is in the active stopping or danger condition.

The particular car and trackvvay equipment shown in Fig. l and above described forms no part of the present invention and is disclosed and claimed in other applications.

According to the present invention, the track elements T are located on the center line of the track so that they will co-operate with the car equipment on a vehicle traveling in either direction. It is necessary, therefore, to provide controlling circuits for the track element such that it will give the desired opposingand following protection, but will not transmit a stopping impulse at the Wrong time; and the subject matter of the present invention consists primarily in an arrangement of controlling circuits for accomplishing this result.

Fig. 2 showsone arrangement of controlling circuits embodying the invention and particularlyv applicable for signal locations where there are two opposing signals located opposite each other. Since the same arrangement is employed for each signal location, a description of one will suffice for all. The signals S and S are controlled by polarized line relays L and L respectively, in the usual way, and since these control circuits are well-known and are clearly shown, no detail explanation will be given. It is noted here that these circuits have been shown according to the convention in which the letter B indicates a connection to one teru'iinal of a battery or other source of curr and the letter C a connection to the otlur terminal of said battery, either d rectly or through a common wire for the ystem.

The track. element T is preferably 10- cate-fl dire ly opposite the insulated joints 2 between the track sections B and C. The coils 6 of said track element are provided wi h two circuits in multiple. When either of these circuits is closed, the track element T is in its safety proceed condition, and with both of said circuits open, the track ele ment is in its stopping condition. These circuits include neutral and polar contacts on the line relays of the respective signals, so that each of said circuits are open when the corresponding signal is in the caution or stop position. For example, if the signal S is in the clear position, the coils 6 of the track element are in a closed circuit which may be traced as follows: Commencing at one coil 6, wire 20, polar arn'iature 21 of the line relay L wire 22, neutral armature 23 of said line relay, and wire 24 to the other coil 6. This circuit will be opened at the polar armature 21 when the signal S is in the caution position, and at the neutral armature 22 when the line relay is deene-rgized to give stop indication. In other words, if either one of the signals S or 8*, is in the proceed position, the track element is in the safety condition, but if both of said signals are in either the caution or stop position, said track element is in the active stopping condition.

The arrangement shown in Fig. 2 operates in the following manner. Suppose a train is traveling from left to right, in the direction of trafiic governed by the signal S. As the train approaches track element T, the opposing signal S is in the stop posi-- tion to block opposing train movements by virtue of the control of signal S fully plained in my prior patent.

The condition of the track element T, therefore, depends upon the line relay L, which in turn is controlled by trains ahead of the train in question and traveling in the same direction. If there is no other train ahead, and the signal S is in the clear position, the coils 6 of the track element T are in a closed circuit, and train may pass with out receiving a stopping impulse. If, however, there should be another train ahead, either in the next or succeeding block, and the signal S is in either the stop or caution position, the coils 6 are open-circuited, and a stopping impulse will be communicated to the passing train. The same mode of operation is true for train movements in the opposite direction from right to left, the con trol of the track element being then gov erned in accordance with the indication of signal S the signal S being in the stop position. In this way, the arrangement of controlling circuits shown in Fig. 2 pro vides for governing trains traveling in either direction in accordance with the nal indication. It should be understood that the car element is carried on the locomotive or the leading vehicle of the train so that it passes over the track element before the line relay of the next track section in advance has been deenergized by the front end of the train itself. ln most cases it is fo'iuiol preferable to support the car elen'ient directly back of the pilot in front of the ponytruck.

The same control shown in Fig. 2 may be applied to each of the pairs of signals shown in Fig. l; and except in one case, the stop ping impulse is transmitted oi'ily when it necessary for the train to stop. To illustrate the x'ceptional case, suppose there is a train on the main track opposite one of the sidings X, then an approaching train about to enter the siding will receive a stopping impulse upon passing the signal 3*, since both the signals S and are in he stop position. lt may or may not be obict.- tio-nableto receive a stepping impulse under these said circumstances, depending upon the type of train control apparatus. If the s stem is one enforcing speed restrictions, or one in which a permissive control is imposed, stopping impulse in this particular instance does no harm, and strictly speaking, is proper. lf desired, the controlling condition of the track element at the starting signals may be made dependi-uit upon the position of the switch leading to the siding, or upon some manual action on the part of the trainman throwing the switch.

Fig. 3 sho vs an arrangement operated in the same way as that shown in 2 the only difference being that the controlling circuits for the track element are taken through circuit controllers U and operated by the signals S and S instead of through neutral and polar contacts of the line relays. These circuit controllers and O are shown in accordance with established convention, and are closed only when the corresponding signal is in the clear position.

Instead of arranging the intermediate nals in pairs opposite to each other, as shown in Fig. 1, a staggered arrangement of intermediate signals is sometimes employed, that. is, signals S and S are omitted, and the intermediate signals S and S used alone to give the desired opposing and following protection. In such an arrangement, there will be only one signal at each intermediate signal location, so that the circuit arrangeinent of Figs. 2 and 3 is not applicable.

Fig. 5 illustrates a modified construction for use with such staggered intermediate signals. lln this arrangement, the track ele ment T is provided with two multiple controllingcircuits as before, and one of these circuits is taken through the neutral and polar contacts of the line relay L, or through a circuit cont-roller operated by the signal The other circuit includes a. front contact of the track relay 3 of the track section B next in the rear of the signal in question. VVhe-Ii a train travels from left to right, in the direction. of trallic governed by signal 8*, it shunts-the track relay 3 M5042, rye

and opens one of controlling circuits for the track element 'l before it reaches clement, so that the controlling condition c said track element is dependent upon tli indication of signal S as before. it t traveling in the opposite. direction, how will pass the track element before shuntiu the track relay 3 and consequently wil pass said track elementwithout receiving a stoppin impulse, in spite of the fact that the signal S will be in the stop position.

Fig; 6 shows a similar arranger-m a: tn- 2. single s location. more particular u to give a stow impulse if thi signal is in the caution sition though not necessarily if the signal is in the stop posi U011.

ln this arrangement. one of the twill controlling circuits for the track element T is taken through a back contact of the track relay 3 of the track section next in advance of the signal S. A train traveling in tl e direction of tratiic governed by the signal 5%" will pass the track clement before dropping the track relay 3. and consequently the controlling condition of said track element is deptuidcnt upon the indication of said signal. A train traveling in the opposite direction, however, wil drop tra l: relay 3 and put the track element in the safety condition, before the track element is passed.

Fig. 7 shows a modification of the an rangeinent illustrated in i (3, and provides for a stopping impulse at a stop sig nal, as well as a caution Slgnith which does not necessarily follow in the arra gement shown in 6. To illustrate with the arrangement shown .in i 6, suppose there is a train. on the track section C, then a following train will not receive a stopping iinpulse, because the track relay 3 is down. In the modified arrangement shown in Fig. 7, the controlling circuit for the track ele ment, which includes the back contact of the track relay 3 also includes a back con tact 31 of the stick relay 30 associated with the signal 5%, this stick relay being one of the characteristic parts of the .l. l sys tem. The control of this stick relay is fully explained in my prior patent. and need be reviewed only briefly. The pick-up circuit for said stick relay may be traced as foil lows: Commencing at one terminal of the battery (indicated by B) through contacts of circuit controller 32 operated by s I 7 S and closed between about to 33, back contac 3-5!- of track relay 3,

Wires 35-36, stick relay 30 to the other terminal of the battery (indicated by C). A train traveling from left to right picks up the stick relay, because it closes this pick-up circuit at back contact the circuit controller 32 remaining closed for a short interval. Trains traveling in the opposite direction donot pick up the stick relay ben e-o ltlt) ill) llii

cause they open its pick-up circuit at the circuit controller 32 before they drop track relay PF and close its back contact 3 The stick relay 30, when once picked up, is maintained energized by a stick circuit as follows: Commencing at B, back contact 37 oi? line relay L, wire front contact 39 of the sticlr relay itself, wires 4:O 6, and stick relay 30, to (,l. assume there is a train on the track section C, the baclr contact of track relay 3 will be closed, but it this train entered said track section from the track section B, stick relay 30 was picked up, s that the track clement behind said train in the track section C will transmit a stopping impulse to a following train. A. train approaching in the opposite direction, that is, from right to left. is able to pass the track element T without receiving a stopping impulse in the same way asdescribed in connection with Fig. 6, the st ck relay 30 in this case remaining deenergized.

From the foregoing it will he observed that this invention provides an arrangement of controlling circuits for track elements by means of whichv the controlling condition of said elements may be automatically set up to conform with the signal in dication. even though the trains move in either direction past said track element. Generally stated, this is accomplished by providing two controlling circuits for the track element, each of which may be said to correspond to one direction of train movement. If there is a pair of opposing signals at the signal location, these two circuits for the track element are governed in accordance with the signal indications. If there is only one signal at a signal location, one of these circuits is controlled in accord ance with the indication of that signal, and the other by the track circuits in such a way as to prevent an opposing train traveil. opposite to the direction of traffic gO fel-l by said signal from stopping itself.

The particular constructions and arrange ments of circuits and devices herein shown and described are obviously susceptible of various modifications and adaptations to suit various types of train. control systems and differentvforms 0'1": single track automatic block systems, and I desire t have it understood, therefore, that the embodiments of the invention shown and described are merely illustrative of: its nature and mode of operation.

lVhat I claim is:

1. In a train control system for single track railroads provided with track circuits, the combination with a track element having an inherent tendency to assume an active stopping condition and adapted when in that condition to communicate a stopping influence inductively through an intervening air gap to a train traveling in.

either direction thereby, said track element including an iron core and a Winding thereon, two separate control circuits for said track element each passing through said winding, said track element being in the same inactive condition ii either of said circuits is closed, and means controlled by a plurality of track circuits on opposite sides of the track element for separately and independently governing said circuits.

2. In a train control system for single track railroads provided with track circuits, and having oppositely located intermediate signals between sidings, said signals governing trafiic in opposite directions, the combination with a track element associated with said signals and having two control circuits each adapted when closed to cause said element to asume the same inactive proceed condition, of means subjected to the same controlling influence as said signals for controlling said circuits separately.

3. In a train control system for single track railroads provided with track circuits, and having oppositely located intermediate signals between sidings, said signals governing tra'tfic in opposite directions, the combination with a track element associated with said signals and having two control circuits each adapted when closed to cause said element to assume the same inactive proceed condition, of circuit controlling means in each of said circuits closed when the track circuits governing the corresponding signal are not occupied.

4. In a train control system for single traclr railroads equipped with an absolutepermissive-block system having opposite intermediate signals, a track element opposite each pair of intermediate signals, and

means for placing each track element in the inactive condition unless both signals as sociated therewith are in the caution or stop position.

5. In an automatic train control system for single track railroads equipped with an A. P. B. system having; pairs of opposite intermediate signals, a track element opposite each pair of signals, and means whereby the controlling condition of said track elements is automatically caused. to correspond with the indication of the associated signal governing traflic in the direction in which a train approaches that track element.

6. In a system of automatic train control for single track railroads, a track element comprising a non-magnetized iron core disposed symmetrically with respect to the center line of the track so as to influence c0- operating receiving elements on the vehicle traveling by said element in either direction, a winding on said core, a normally closed deenergized circuit of low resistance including said winding and adapted when closed to place said track element in its inactive condition, and automatic means for opening said circuit upon the approach of a train to said track element from either direction ii there is another trainin advance.

7, A train control system for single track railroads corprising, a track element ellecti e when in the stopping condition to transmni impulses inductively to trains traveling in either direction, said track element has, j a control winding, two control circuits for said element each passing through said winding and each acting it closed to render said element ineffective to transmit an im* pulse to a passing vehicle traveling in either direction thereby, and automatic means for maintainin closed one or the other oi said circuits during the movement oi the train in one direction or the other past said element provided there is no other track element in the direction 0]? which said passing train is traveling.

8. In an automatic train control system for single track railroads provided with track circuits, a signal governing trallic in one direction, a track element opposite said signal and having a normally closed c ntrol circuit adapted so long as closed to cause said element to assume its inactive condition, and means controlled by a track circuit in the I rear of the signal for opening said control circuit.

9. lln a train control system for single track railroads provided with track circuits, the combination with a signal, of a track element located opposite said signal and comprising an iron core and a coil thereon, said track element having two control Clljcuits each including said coil and adapted when closed to cause said element to assume its inactive condition, means for controlling one of said circuits to conform with the indication of the signal, and means controlled by a track circuit in the rear of the signal for governing the other control circuit.

10'. ln a system of train control for sin le tracli railroads having track circuits sic nal governing tratlic in one direction. a tract: element located opposite the signal and having a normally closed control circuit which normally maintains said element in its inactive condition, and means for opening said control circuit before a train traveling in the direction of traflic governed by said signal reaches said element and for maintaining said circuit closed until after the first vehicle oil a train traveling opposite to the direction of the traflic governed by said signal has passed said track element.

1].. ln a train control system for single track railroads equipped with a block signal system oi": the type described, the combination with a pair of oppositely located intermediate signals of said block signal system, a. track clement adjacent to the signals and comprising a core and a coil thereon, a

a 1,50%,1 is

" each includin nt. in a train control systen,

raidroads equipped with i nal system of the type described, th'

1' 'on with a signal, a track eleme poseo substantially opposite tl e si comprising non-magnetized core i thereon, a circuit including the coil ant, closer. if the signal is in the proceed position, and another separate c: s it incl d 5 the coil and governed by a 'aclr circuit n the rear of the signal.

In a train control system tor track railroads equipped with a block si system of the type described the (Gilli/lul tion with a sin al. a track element disposed symmetrically with respect to the cente line oi the track and adjacent to the signal so as to influence cooperating car apparatus on a vehicle traveling in either direction the eby. said track element comprising an iron core and a coil thereon, two circuits each pass ng through said coil, and automatic means comprising said circuits for main training said element in the same ii'iactire cor lion tor vehicles inoi' ug in either Tllrection tl'iereliij-i unless there s another train ahead in the direction o'li' trai'iic governed by said signal,

14;. In a train control system for sin 'le track railroads equhapcd with a block si system of the type described. the coiubia, tion with two adja ent track circuits oi block signal system, a track element disposed opposite the adjacent ends oil said track circuits and ha ing winding. and means l automatically by each trac i independently establish nc 0 nuts at low resistance includiu s winding so long as that correspondind circuit is not occupied.

ln :1 train controlsystem for single trach roads equipped with a block si 'nal system oi the type described. the combi; tion with a signal. a magnetic core extending transversely of the track and disposed adjacent to the signal symmetrically vith respect to the center line of the track, a winding on said core. and two separate circuits each including said winding and governed separately by track circuits on opposite sides of the signal.

16. In train control system tor single track railroads equipped with a block signal system of the type described, the combina tion with two oppositely located intermediate signals, a track element opposite said signals and disposed symmetrically with re spect to the center line of the track, a circuit adapted when closed to maintain element in its inactive condition, means sub jected to the same controlling influence one of said signals for closing said circuit at times when the signal. may indicate proceed, a second. circuit also adapted when closed to maintain. the track element in the same inactive condition, and means subjected to the same controlling influence the other of said signals for closing the secnd circuit when that signal indicates proceed.

i7. In a train control system for single tract: railroads, trackway equipment for cooperating inductively with car-carried apparatus through an intervening air gap comprising, two adjacent track circuits, a track element at the adjacent ends of said track circuits, said track element being normally inactive, and automatic means for maintaining said clement inactive so long as either of said track circuits is not occupied.

l8. A, train control system for single track railroads for use in conjunction with a block signal system of the absolute-permissivebloclr type described, comprising a track element located opposite a signal, said track element con'i n'ising a non-magnetized core, and auton'iatic means for governing the con trolling condition of each track element to correspond with the indication of the asso' ciatcd signal for trains moving in the direction of traflic governed by said signal, and for maintaininq said track element inactive until the first car of a train traveling in the opposite direction has passed said element.

19. Inductive influence communicating means for block signal systems of single track railroads comprising, a track element having a core and a coil thereon. and disposed symmetrically with respect to the center line of the track, and automatic means for including said coil in a closed deenergized circuit of low resistance for train movement thereby in either direction unless there is another train ahead.

20. An automatic train control system of the type described, the combination with a trackway block signal automatically governed in accordance with the presence or absence of other trains ahead, a track element a iacent to said signal and having an in herent tendency to communicate the stopping influence, a non-energized control circuii" tor said element adapted when closed to render said element inactive, and automatic means for closing said circuit during the increment of a vehicle in either direction by said signal unless there is another train ahead of the signal in the direction of traflic governed thereby.

21. In a train control system, the combination with trackway signals and control means therefor constituting an absolute-permissivehloclr signal system of the general type described, track elements adapted to co operate inductively through an intervening air gap with car-carried apparatus and ar ranged to communicate an influence to passing cars to conform with the indications of each. signal, a polarized line circuit for gov- Qljlllllg each signal, and means controlled by said line circuit tor governing the contr0lling condition of the corresponding track element.

In a train control system, the combination with traclzway signals and control means therefor constituting an absolute-permissive-block signal system of the general type described, a track element at each sig nal comprising a core and a coil thereon, a circuit including said coil, and a polarized line relay governing each signal and also controlling said circuit.

23. In a train control system, the combination with trackway signals and control means therefor constituting an absolute-perinissivc-block signal system of the general type described, a track element for each sig- :11 comprising a non-magnetized core and a coil thereon, said track element being adapted to communicate an influence to a passing vehicle unless said coil is included in a circuit of low resistance, a polarized line relay governing each signal, and a circuit of low resistance for the coil of the corresponding track element governed by said relay.

In testimony whereof I afiix my signature.

SEDGWIGK N. WIGHT.

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