US1703831A - Continuous inductive train-control system - Google Patents

Description

Feb. 26, 1929. 7

W. H. REICHARD CONTINUOUS INDUCTIVE TRAIN CONTRQL SYSTEM Filed May 24, 1926 m INVENTORI w AZATTORNEY Patented Feb. 26, 1929 UNITED STATES FNT OFFICE.

PAT

WADE H. REIGHARD, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK. i

CONTINUOUS INDUGTIVE 'IPRAIN-CONIROL SYSTEM.

Application filed May 24,

This invent-ion relates to automatic train control systems of the continuous inductive type. i

In train control systems of the two position or two condition continuous inductive type, the train is permitted to proceed in response to train control current flowing; down one rail of the trackway through the axles of the train and back through the other rail, that is,

in response to currenttlowing in the usual track circuit. For well known reasons if the train is permitted to proceed in response to current flowing in the usual. track circuit this same current cannot be used for controlling the track relay, because it is necessary. to cut off the train control track circuit current in a, caution block, and if this same current, were used for operating the track relay the removal of energy from one block would effect removal of energy from the next block in the rear, this now being a caution block, and this block in turn would cut off the on orgy of the next block in the rear, and so on ad infinitum; and for this reason it is impracticable to use the same current for train control purposes and for track relay control purposes in a system of this kind. One eX- pedient heretofore proposed is the use of direct current in the track circuit for track relay control purposes and in superimposing alternating current thereon under clear traffic conditions only, so that there is only direct current flowing in the track-circuit under caution trailic conditions but alternating current also is flowing therein under clear traffic conditions. Several other important problems in two position continuous inductive train control systems are: the necessity of means. requiring the engineer to manifest his vigilance in entering a caution block and in passing successive stop signals, and the need of amplifying means which will not produce a false clear indication due to an internal electrical disturbance in the car-carried system, for instance, such as. voltage fluctuations due to commutator construction known as commutator ripples, and the like.

In view of the above and other important considerations, it is proposed in accordance with the present invention to use alternating current ofone frequency for track relay control purposes and use alternating; current of another frequency for train control purposes, and to apply the alternating current for 1926. .Serial No. 111,289.

track relay control purposes at the entrance endsof the blocks for the normal direction of trafilc, and to apply the alternating current for train control purposes at the exit ends of the blocks; to arrange the amplifying apparatus in a manner so that voltage fluctuations due to commutator ripples will not be applied to the grid of the first of the two successive audions, so that such fluctuations will not be amplified by the first audion; and to provide suitable cab signaling; means which will inform the engineer to trailic conditions ahead and as to when he must acknowledge or manifest his vigilance.

Other objects, purposes and characteristic features of the invention will appear from the description of the invention, and will in part be obvious from the drawing.

In describing the invention in detail refer ence will be made to the single figure of drawing in which both the car-carried and trackway apparatus of one particular train control system embodying the present invention has been shown. i

Referring tothe drawings it appears 6X- pedient to divide the system as shown into three distinctive parts; namely, the way apparatus, the influence transmitting and amplifying mechanism, and the train control and cab signal mechanism; therefore, these parts will be considered separately.

Track way apparatus.

In the arrangement shown the track rails 1, have been divided by insulating joints 2, into blocks in the usual way, of which the block I and the adjacent ends of two other blocks H and J have been shown; and since these various blocks are the 'same, like parts of each block are designated by like refer- 'ence characters having distinctive exponents.

At the entrance'end of each block, the normal direction of traffic being as indicated by the arrow, is provided a wayside signal Z, which may be a light signal or a semaphore signal and which for convenience has been illustrated as a semaphore signal of the three posi tion type.

Across the rails at the entrance end of the block is impressed an alternating current derived from a transformer 5 which is con ncctedto a transmission line carrying a current having; a suitable commercial frequency, such as 60 cycles, for instance, and across the exit end of each block is connected a track relay T which has its local winding 6 connected to the same source of current,

- proper phase displacement between the currents in the windings of this track relay being obtained in any suitable manner. Since the track relay is at the exit end of the block it is necessary to repeat the indication to the entrance end of the block, and for this purpose the polar-neutral line relay LR is employed. This line relay LR controlled by a pole changer switch PC controlled by the next signal in advance, that is Z, in a manner to apply positive energy to the relay LR when the signal next in advance is in either the clear or caution position and to apply negative energy to the relay LR if said signal in advance is at danger, energy being entirely cut off from the line relay LR by the contact 7 if the track relay of the block in question is in its retracted or (lo-energized condition; The signal Z is controlled by the line relay LR in the usual manner, which needs no further description; the common return wire 8 of the signal Z, however, contrary to the usual practice includes a front contact 9 of a check relay CK more particularly described hereinafter. The description thus far has been directed vonly to wayside signal apparatus, and we will presently consider the trackway train control apparatus.

In orderto allow a train equippedwith two position continuous inductive train control apparatus to proceed, it is n cessary to impress a potential of train control currentof a suitable frequency distinctive from the track circuit frequency across the exit end of a block, so that this current may flow down one rail through the wheels and axles of the train and back through the other rail, and for this purpose the transformer 12 is employed. The circuit for applying this train control current across the exit end of the block includes, a back cont-a ct 13 of the track relay T, a front contact 14 of the line relay LR of the block in advance, and a contact 15 on the signal blade of the signal Z closed when the signal is in either the clear or the caution position, from which it will appear that the alternating train control current is not ap- 50 plied across the exit end of the block unless traflic conditions are clear and then not until a train has entered such block and has dropped the track relay thereof. This latter feature causes the secondary winding of the transformer '1 to partially shunt the track relayonly when the block in question is already occupied, and does not leave this partial shunt on the track relay under normal clear trafiic conditions. In this connection it is desired to point out that under ordinary conditions the track relay T will pick up even though the secondary winding of transformer '12 does partially shunt this relay,

'when this relay is dropped, of course assuming the block to be unoccupied at this time,

block I becoming unoccupied That is, a train passing through block I drops relay T, and causes the secondary of transformer 12 to shunt the relay T, but upon again, ll around relay T does not prevent the cuit current from picl-Iing relay 'l This transformer 12 has its primary w udiu connected to a transmission line no which supplies alternating train conlrol current oi track circuit current frequency. and which for convenience may be assumed to be cycles. For a short distance near the c-it end of each block is provided means for ca using current to flow in the same direction in both of the rails in multiple; this in order to compel the engineer to manifest his \i iiunce as he passes by this short section under adverse traiiic conditions ahead. in the particular arrangement shown, balancing rcsistances 18 and 19 are connected between the track rails at two spaced points near the or it end of the block, and to the middle point of each of these resistances connected one terminal of the secondary winding of a trausformer 20. In order to assure that this current flowing in the same direction in both of the rails, that is, simplex current, is present the check relay CK is connected in ice with this circuit, and the front contact 0 of this check relay is included in the common return wire 8 of the signal next in advance. The purpose of this simplex current will be more particularly pointed out hereinafter. At this point it may be well to note that the secondary winding of the transformer 5 has an impedance 17 connected in series therewith for limiting the current flow therein. The secondary winding of the transl'ornicr 12 preferably has suilicient internal ohmic resistance to limit the current flow therein, or has a suitable filter connected in series therewith which limits the flow of current of track circuit frequency only.

The car-carried apparatus includes a main relay MR having windings 30 and ll which are at times energized by suitable amplifying means, to the plate circuits: of which ilw. windings are connected. hlore s these windings 30 and 31 are conncr d acr the inductive reactances and 33 ihcludrd in the plate circuits of the audions A? and .i" respectively, the arrangement being such that if these audions A and A have tluir grids excited by opposite relative polarii' of an alternating current the relay Mil v. ll be energized to its normal condition. in Which its contacts 86 and 3 ussume the positions in which they are shown. This functimiiugg of the relay ME in response to two alternating current potentials of oppos te relative polari ties is preferably accomplished by making loo the circuit for one of these windings highly reactive and the circuit for the other winding high resistive 0r condensive; this may be accomplished by selecting the windings and 31 and the capacities of the blocking condenscrs 38 and 39 properly, or it may be accomplished by any other and well known the filaments of 05 A The return ends of the grid circuits of the audions A A connected to the negative terminal of the filament generator FG and lnclude the windings of the auto-transformers AT and AT respectively.

From this arrangement it will be seen that the grids of the audions A A are considerably negatively biased due to the drop of potential across the resistances R and R respectively, as well as due to the potential drop across the filaments of audions a and c A potential is applied to the primary portion of the transformers AT and AT by the alternating current potential drop across the inductivereactances 40 and 41 respectively in the plate circuits of the audions a and a and the alternating current flowing due to this potential flows through the condensers 12 and 43 respectively.

Mounted on the railway vehicle, which has been illustrated by the wheels and axles 46, and in front of the first wheels and axle thereof are receivers 47 and 48 having winding-s s9 and 50 thereon which are tuned or resonated to the frequency of the train control current by condensers 51 and 52 respectively. One end of each of the windings 419 and 50 is connected to the common return wire 5d from whence they lead through the grid bias battery CB, commonly known as a C battery, to the negative terminal of the filament generator FG, the other ends of the coils 49 and 50 being led through the reversing switch RS to the grids of the audions a and a respectively. From this construction it appears that the C battery CB applies a negative bias to the grids of the audions a and a respectively which audions comprise the first stage of the amplifying mechanisn'i, the sec- 0nd stage including the audions 1 and A If the railway vehicle 46 enters a clear block train control current will flow toward the train in one rail through the wheels and axle of the train and away from the train in the other rail, and this train control currentimpresses relatively opposite alternating potentials on the grids of the audions a and a respectively, which audions in turn apply amplified alternating current potentials to the grids of the second stage audions il and A respectively, and which in turn produce a flow of alternating current in the relayMll to cause it to assume its normal position. When the train enters the short section between balancing resistances 18 and 19 the effect of the current produced by transformer 12 predominates over the effect produced by the current derived from the transformer 20 so that no ch ange'in the condition of the main relay MR takes place when passing}; from left to right into the section 1819 under clear tralfic conditions of the block. If a train enters a cantion block from which the. supply of train control current connect d across the exit end of the block has been removed, as for instance by the dropping of contact 141 the relay MR assumes its die-energized position, and when the train passes beyond the balancing re stance 18, and encounters d e simplex current flowing through the rails in multiple, one supplied by transformer 20, the induced voltage in coil. and 50 will be in phase, inst ad of in opposition, whereby the relay MR is energized to the reverse or left hand dotted position. As described above, with loop current in the rails, the main relay MR is so connected up as to be energized to normal position. In changing from loop to simplex current in the rails, as between balancing resistances 18 and 19, the net effect is to have left one of the loop currents unchanged, and to have changed the other 180, i. e., to ha re reversed the other. Thus, if with loop current, the relay MB is acted on by two currents displaced about 90 in phase, then with simplex current, the relay is acted on by two currents likewise displaced in phase about 90; but the displacement is in the angular direction reverse to the normal displacement. For a further and more dc ailed description of an amplifier of this general type reference .may be had to the prior application of William D. Hailes #752,838 filed Nov. 26, 1925. A more detailed functioning of the system will be described under the head of operation hereinafter.

il /rain control and ca?) signaling mechanism.

The particular train control mechanism illustrated in the present en'ibodiment of the invention is one of the permissive ty e, in which the unrestricted progress of the train is only interfered with in the event the on gineer is not attending; to his duties and does not manifest his vigilance when he should; and in order for the train to proceed in territory where there is no train control current flowing in the usual trackway circuit there is provided a supplemental relay, which may be energized by the engineer when he manifests his vigilance by performing a manual act upon his entrance into territory in which adverse traffic conditions exist. In the arrangementshown this relay which is conveniently called an acknowledging relay has been designated AR. By the arrangement shown it'is possible the engineer to pick up this acknowledging relay AR it he depresses the acknowledging push button Ac/ c before the brakev control relay BB is tleenergized. The normal energizingcircuit for the brake control relay BR may be traced as follows: beginning at the terminal B of a suitable source of energy, contact 37 ot' the main relay MB in its normal position wires 61, 62 and 63, winding of the brake control relay BR, to common return wire C connected to the other terminal of said source of energy. The circuit 111st traced Is also closed when the main relay MB is in the reverse position in which event the wire 6% is included in the circuit. With the brake control relay BF. energized the electropneumatic brake applying device E. V. is energized through the following circuit bee'inning the ter- 6 connected to the other side of said source.

Also, the lamp G is energized under normal clear trarlic conditions through a clrcuit including the contact36 ot the main relay ill-R; which c1rcu1t-may readily be traced 1n the d rowing. I

O 7) o ation.

For reasons heretofore git-en. wits a train passing along}; the trackway under clear trattic conditions the main relay MR will remain in its normal energize-Cl condition when pass ing through the sections 1819-because the simplex current flowing; between the balancing; resistances 18 and 19 near the exit end of each block is insufficient to interfere with the proper energization of the main relay by the train control track circuit current supplied by transformer '12, that is, the train control current is the predominating current oi" these two currents. r I

Let us assumethat the engineer is not vi ilant, and that the bloclr J in the particular arrangement shown is occupied by another train. which of course will cause the line relay "lilt to assume the de-energized condition.

vtrain to a stop.

agaoaesa sume their retracted position thus causing the brake control relay lllt to assume its deenergized condition. and the act of acknowledging; at this time of no :2 oil because the pickup circuit for the relay All (traced below) is open front contact 92 of relay BR.

l fith the brake control relay in its retracted condition. the bral-zc applying; dcrice E. P. V. is thus do-encrgiacd and brings the its soon as the train has been brought to a stop the engineer it he wishes to again proceed may alight to the around and operate the reset push button lltil. which is only accessible from the ;:ground. It the push button R1"? is dcpres. l the following circuit for picking: up the acnnowlcdeing re lay closed beginning at the terminal B, contact 37 of the main relay Mil when in its de-energized pendant position. wire 7'3, normally open Contact 77 of the reset button RS, wires 78 and 79., upper winding 80 of the acknowledging relay to common return wire C connected to the other side of the said source or energy. This causes the achnowledging relay All to assume its energized condition thus causing; the followinu dick circuit to be closed. bearing; in mind that the main relay is still (lo-energized :-be;rinui1'1 r at the terminal B contact 37 oil: the main relay MR. wire 81, front contact oi. the acknowledging relay All. the lower winding; 84: of the acknowledging relay An. wire 83 to common return wire C. l l ith this stick circuit closed the acknowledging: relay All is stuck up, and the closure of its front cont-a ct 85 willclose a circuit for energizing the brake control rela BR, which ma be traced as follows: beginning at the terminal ll, trout contact 85 of the acknowledging relay AP, wires 86 and ($3. winding ot the brake control relay llll. to common return wire C. The engineer may now return his reset push button to normal thereby closing the contact 70. and since the contact 72 is now closed the device E. l V. will again assume its ener .ed inactive condition. This expedient ot including; the contact 70 of the reset push lmtton BS in the circuit of the device E. P. V. is resorted to in order to avoid the reset push button RS being tied or otherwi e fastened in its active posi' tion permanently.

Let us now assume that the train in question passes from the blocl; ll into the block I while the block J occupi l by another train, and that the engineer attending: to his duties and realizes that he about to pass a signal at caution and manifests his vigilance by depressing the acloiowlmlc'ing push hut.- ton rte/ 4:. in dcprc im; this push button A0]? a pick up circui relay AB is completed which may be traced as follows: hep; min at the terminal B, contact 90 oi the iu'linowledgriug push lJllll" ton 126/ 11 wire 91. front con act 952 ot the brake control relay BR, wires 98 LtI1(l 9,WlI1(l Ill) ing 80 of the acknowledging relay AR to common return wire C. It should be noted that the engineer is given a time interval within which to acknowledge, after de-energization of l R, equal to the r lease time of such relay BR. engineer will maintain the acknoui push button A070 in its depressed position until the train has entered the caution block I and the main relay MR has assumed its de-energi zed position; this is permissible even though the contact 90 is closed for an appreciable time, because the contact 68 will not open the circuit for the device E. l V. until a certain interval of time has elapsed, this by. reason of the retarded action effected by a suitable time element device which prevents the contact 68 from immediately opening, which time element device in the particular arangement shown has been conventionally illustrated by the dash pot 95. It is desired to point out that the acknow edging means effective for a predetermined time only, if actuated, is merely an illustration of suitable means for accomplishing the desired result, and that any other suitable means may be used, if desired. As

.soonas the main relay MR assumes its deenergized condition the stick circuit for the acknowledging relay AR heretofore traced is again closed, so that the brake control relay and in turn the device E. P. V. is maintained energized, the device E. P. V. being held 1nactive in spite of the fact that there is no train control current flowing in oposite d1- rections in the two rails ahead of the train.

The train is thus permitted to proceed through the caution block under the control of the engineer even though the rela MR 1s de-energized, but he is doing so at is own risk and is informed of this fact by the illumination of the red danger signal R. Upon entrance of the train into the acknowledging section 18-19 the relay MR is energized to the reverse position, as explained above, under which condition the relay BR is again energized through itsnormal circuit including contact 37 in its reverse or left hand position, themoving of finger 37 of relay MR toan energizedpositionbreaking the stick circuit for relay AR. At this time the-purple acknowledging signal lamp P is illuminated instead of the'clear lamp G, and the engineer is thereby informed that he is just about to enter a danger block and that he is required to manifest his observance and recognition of these facts. With the acknowledglng relay. AR file-energized and the brake control relay v BR maintained up by a circuit including the reverse contact of the main relay MR the train may proceed over the acknowledging section. 18 1 9, and if the engineer does not manifest his vigilance until after the drop away period of ER after entering the occupied block J a brake application will, of

course, occur. If the engineer, however, depresses the acknowledging push button A071: before the relay BR drops due to the main relay assuming the ole-energized position the acknowledging relay is stuck up, as heretofore described, and the train may proceed under the control of the engineer until it enters another caution or danger block, or zone. 7

It is observed that the train is permitted to proceed in clear territoryrin response to current flowing in the track rails; also, it is well to know that such current cannot very well be supplied at dead sections, such as, railway crossings, frogs, switches, or at junctions between blocks where the insulating joints are staggered, and it is primarily for this reason that the brake control relay ER is constructed to be slow releasing. The time required for the relay BR to assume its retracted position after its energizing circuit is broken is preferably such that a train moving at a speed of say 15 miles per hour will not allow this relay to drop during the time the train passes over the longest dead section on the railroad. The engineer is thus not required to acknowledge dead sections. If trailic conditions clear up with the train at an intermediate point in the block, the cab signal will change from red to green, and the brake control relay will be directly energized by the main relay; by this information the engineer is aware of the fact that he may accelerate his train.

It should be noted that, in general, if stray currents are flowing in multiple, along the trackway, of a frequency to which the carcarriedapparatus will respond, this flow of current may cause the relay MR to assume its reversed dotted position, in the same manner as does the simplex current from the transformer 20. It, therefore, stray currents are encounterd in a caution or danger block, where, the relay AR is stuck up due to acknowledgment at the entrance to said block, the engineer will be informed of such stray currents by illumination of the purple'lamp P, while the stick circuit for AR is broken at finger 37 of MR, and, if he is not to incur an automatic brake application after the stray current-ceases to flow he must again acknowledge and thus again pick up the re-.

lay AR or a brake application will occur when such stray current ceases to flow and relay MR again assumes its de-energized position.

Also, due to the manner in which they are connected in the system, if either of the generators FG and PG should develop fluctuations of potential in the carcarried system, the effect of such fluctuations in the currents applied to the main relay MR will be such as to cause this relay to assume its reversed position, assuming of course that they are of tender as t-hje case may he, elements 1-7 and L8 havin windin 'sal and 50 these ivindin s b M 7 i 23 sutlic ient amplitude to operate the relay, and

tion Will be a tor us to reverse aosition.

thus Will not energize ME to normal to thus setup a false clear indication onth-e train;

In this connection, it should be noted, that the various switches and amplifiers are so connected, that any voltage fluctuation developed in either or" the generators, will have the same effect on'all the various filaments and grids of the amplifiers, and he relay MR, and its windings are so connected that the torque'produced in relay ME by such fluctupt is, of course, understood, that coils l8 and 49 are so-connected to the grids of amplifiers a anda that simplex current. will have the same effect on relay MR as the currents produced by'generatorripples, While loop currentswill have the opposite efiect.

' Although the alternating for Wayside signalin and track relay control purposes i's'applied' at the entrance end of the block and therefore cannot readily reach the influence-receiving elements 4'? and 48, suitable-current filtering apparatus may be used in the'ca-r-carried circuits, so that the carcarricd apparatus will not respond to currents other than the train control currents,

which areott the proper frequency.

ltshould be noted that there are provided at the rear end oit l3l16-1110tG1,.0211',01' the rear end of the are'suhstituted in the amplifier circuits for the windin ' s 19 and 50 resnectivel when the engine and tender unit is operat dtender siveto the direction of movement of the train.

7 -Having thus shovvn'and described one specific embodiment ot'the present invention, and having given a rather complete description of the system shown; it is desired to be understood that the particular arrangement shown and described has been selected for the purposeot disclosing the-nature of the invention rather than'its scope, or the particulararrangenient preferably employed inpractice; and that various changes, modifications and additionsinay be made to adapt the invention tothe pa" tion Witliavhich it is to he used, or to adapt it to the} particular form of restriction in the'progress of the vehicle which is to he iniposed, all Without departing from the scope Trackway apparatus train; control, systems-o the continuous inductive type comprising, a traclrivay divided into 'blocks'byinsulatingolnts, a source of alternating current of one frequency connected across the track rails at the entrance end or current applied icular type or railway in connecthe block, a traclt relay responsive to said frequency connected across the track rails at the exit end of the block, means for producing a flow of alternating train control current of a ditl'erent frequency in the same direction in both rails near the exit end of the block, and means "for applying alternatingtrain control current of said different frequency across the rails at the exit end of the block if the block next advance be unoccupied, for controlling a train equipped with train control apparatus or the continuous inductive type, the relative strengths of said train control currents of said different frequency being such that the one applied across the rails at the exit endpredominates, and car-carricd train control apparatus cooperating with thetrack- Way apparatus.

Traclrway apparatus for autoi'natic train control systems of the-continuous inductive type comprising, a trackivay divided into blocks by insulating oints, a source of alternating signaling current of one frequency connected across the track rails at the entrance end of the block, a track relay responsive to said frequency connected across the track rails at the exit endot' the block, means for producing a flow of alternating train controlrcurrent oil a frequency di'llerent fromsaid one trequency in the same direction in current of said distinctive frequency across the rails at the exit end of the block if the next block in advance unoccupied, whereby a train moving in the normal direction oi traiiic may detect the two said distinctive train control currents but not signaling current and train control apparatus associated with the traclrivay apparatus.

3. Trackway apparatus for automatic train control systems ofthe continuous inductive type comprising, a traclcway divided intololocks by insulatingjoints, 1: source of alternating current of one frequency connected across the track rails-at the entrance end of the block, a two element track relay responsive only to said frequency havin one of, its windings COIlllCClQa'l across the track rails at the exit end of the block, means 'ior continuously causrug a How of alternating ing current of the same distinctive frequency across the rails at the exit end of the block when said track relay de-energized an d the next block in advance is unoccupied and train control apparatus for cooperating with;

the traclrway apparatus;

h In an automatic train control system oi the continuous inductive t 'ic. the 0011! binat-ion with traclrwav a) )aratus including means for constantly applying alternating current flowing in the same direction in the Ill) and of block so as to cause ting current to low down one rail. and bacz through the other when the next block in advance is unoccupied, the relative sartrcngth of said currents being such that the current applied across the rails at the exit end or the block predominates over the current flowing in the same direction in both rails; train carried apparatus including a three position relay which will assume its normal position in r use to current flowing down one rails: 'l mick t rough the other and will assume t o/orsed position in response to currr it it in the same direction in both rails, and'mears requiring the engineer to make an acknou edging act each time the relay assimies the reversed position.

5. In auto; atic 1 control system of the continuous induct type, the combination with trackivay apparatus including means for constantly appl 'ing alternating current flowing in the same direction in the two track rails of short section near the end of a block for en orcing vigilance of the engineer when pa ng a wayside signal indicating adverse traffic conditions, means for applying alternating current of the same frequency as said first mentioned alternating current across the rails at the exit end of the block so as to cause alternating current to flow down one rail and back through the other when the next block in advance is unoccupied, the relative strength of said currents being such that the current applied across the rails at the exit end of the block predominates over the current flowing in the same direction in both rails; and of train carriedapparatus including a three position relay which will assume its normal position in response to current flowing down one rail and back through the other and will assume the reversed position in response to current flowing in the same direction in both rails, means requiring the en ineer to acknowledge his vigilance each time the relay assumes the reversed position, and means for causing the signal at the entrance end of the next block. in advance to indicate stop in spite of favorable traffic conditions ahead if the means for applying alternating current to said short secti on fails.

6. Amplifying apparatus for amplifying currents flowing in the track rails in a train control system comprising, two audions each having a filament, a grid and a plate; a circuit for energizing the two filaments of said audions including the filaments and a grid bias resistance in series, said resistance bein contained between said two filaments; and source of direct current energy having its negative terminal connected to the free end of the filament of the first audion and the positive terminal connecting to the free end of the filament of the second audion; the grid circuit of the first audion having a grid bias battery connected in series therewith, and the grid circuit for the second audion having its grid return wire connected to the negative terminal of said source of energy; whereby a negative bias is applied to both of the grids said audions and whereby fluctuations due to commutator ripples are not amplified by the first audion.

'7. Amplifying apparatus for automatic train control systems of the continuous iu ductive type comprising in combination, a first and a second audion each having a filament, a plate, and a grid; a filament circuit including the two filaments and a filament source of current in series so that the lilarent of the second audion is connected to the positive terminal of said source and filament of the first audion is connected to the negative terminal of said source, a grid bias battery in the grid circuit of the first audion, the return wire of the grid circuit of the second audion being connected to the negative terminal of said source; whereby the grids of both audions are negatively biased, and whereby voltage fluctuations of said source are not amplified by said first audion.

8. Car-carried apparatus for automatic train control systems of the continuous inductive type comprising in combination; a three position relay which assumes its normal position under favorable traffic conditions ahead and assumes its'reversed position when it approaches a signal indicating adverse traffic conditions; a stick relay; a slow acting relay maintained energized if said three position relay assumes either the normal or the reverse position or if said stick relay assumes the energized position; said stick relay having a pick up circuit including a front contact of said slow acting relay and an acknowledging push button contact in series; a stick circuit for said stick relay including a front contact thereof and a contact closed when said three position relay is ale-energized; and a. brake control device governed by said slow acting relay.

9. Car-carried apparatus for automatic train control systems of the continuous inductive type comprising in combination, a three position relay which assumes its normal position under favorable trafiic conditions ahead, assumes its (lo-energized under dangerous traffic conditions, and which for a time assumes its reversed position when it approaches a signalindicating adversetrailic conditions; a stick relay a slow acting brake control device maintained energized if said three position relay assumes either the normad or the reverse position and which is energized' it said stick relay assumes the energized position said stick relay having a pick up circuit including a front contact of said slow actingihrake control device and an aeknowledging push button contactin series; a stick circuit for said stick relay including a front contact thereof and a contact closed When said three position relay is de-encrgized;. thereby the engineer is required to manifest his vigilance by picking up said stick relay upon his enti ce into territory Where adverse tI'EIl'JQCODL itions 10; In an automatic train control system of the continuous ind ietive type, the combination With trackway apparatus including means for constantly applying alternating; current flowing in the same direction in. the two track rails of a short near the end of a block for enforcing vigilance of the engineer when passing a wayside signal indieating adverse trafiie conditions; means for applying alternating current of the same freimos s'e'i block so as to cause alternating current to flow down one rail and back through the other when the next block in advance is unoccupied, the relative strength oi said eurrents being such that the current applied across the rails at the exit end of the block predon'iinates over the current flowing in the same direction in both rails; and of rain carried apparatus including a three position relay Which Will assume its nornml position in response to current flowing; down one rail and back through the otheand will assume its reverse position in response to current flowing in the same direction in both rails, means requiring the engineer to manifest his r 'iance each time the relay assumes its reverse position, and means for causing the next signal in the rear to indicate non-clear t 'allie conditions if the means for applying alternating current to said short section fails.

In testimony whereof I ailix my signature.

WADE H. BET CHAR I).

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