US1811857A - Railway traffic controlling system - Google Patents

Description

June 30, 1931. L. E. MELHUISH 1,811,857

, RAILWAY TRAFFIC CONTROLLING SYSTEM 4 Filed Nov. 50, 1926 3 Sheets-Sheet 1 [oz/rem: Ale/ M. k y .31;

A/fnmev L. E. MELHUISH 1,811,857

AY TRAFFIC CONTROLLING SYSTEM s Sheets-Sheet 2 .lun 30, 1931 RAILW Filed Nov. 30, 1926 //7ve/7f0/:' Laurence f. Mgy/ls/z y W I Af/amey June 30, 1931. MELIHUISH 1,811,857

RAILWAY TRAFFI IC CONTROLLING SYSTEM Filed Nov. 30, 1926 3 Sheets-Sheet 3 3 is k s "J &

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' Af/omey Patented June 30, 1931 UNITED STATES ATENT orrics LAURENCE E. MELHUISH, or GLEN RIDGE, NEW JERSEY, AssIeNoETo wEs'rERN ELEG- TR-Io COMPANY, INCORPGRATED, on NEW YORK, N. Y., A CORPORATION OF NEW YORK RAILWAY TRAFFIC dONTRQLLING SYSTEM Application filed November 30, 1926. Serial No. 151,664.

This invention relates to communication between relatively movable bodies, and especially to automatic train control.

According to this invention, each track relay of a block signaling system controls the frequency of waves radiated from an antenna provided near the relay, in response to track conditions, and the waves are picked up by the antenna of a heterodyne detector on the train as the train passes the transmitting loops. The frequency of the oscillator in the heterodyne detector is fixed. The detected waves diifering from each other in frequency pass through respectively corresponding frequency selective circuits in the output of the detector and control the power supply and the brakes for the train in accordance with the track conditions.

Fig. 1 shows schematically a system embodying the invention;

Fig. 2 shows wayside signaling and wave generatin apparatus such as is located near each of the insulated rail joints which, as usual, divide the train rail into successive signaling locks; and

Fig. 3 shows equipment such as is carried by each train for receiving anddetecting the waves generated by the wayside apparatus of Fig. 2 and controlling the power supply and the brakes-0f the train in accordance with the received signals.

Referring first to Fig. 1, the reference characters 1' and r designate the track rails of a railway, which rails are divid d by in.- sulated joints to form blocks rl B, BC,

and so forth.

arrow. 7

Each block has a track circuit comprising the track rails of the block, means for applying alternating signaling olectromotive force across the rails adjacent the exit end of the block and a track relay adjacent the entrance end of the block. The source of E. M. F. for each track circuit is a secondary winding 3 of a transformer which is designated T with a subscript corresponding to the location, and the relay for each track circuit is designated by the reference character .1 with a subscript corresponding to Traffic along the railwayzis normally in the direction indicated by thethe location. For example, the traclrcircuit for block BO includes the secondary winding 3 of transformer T and relay J The primary windings of the several.

transformers T are connected with transmission mains 4: which extend along the railway and to which alternating signaling current is supplied by suitable means, such as by a generator 7 Each track relay is of the three-position type, comprising two windings 5 and 6. The former is connected directly with the track rails and receives track circuit current which at times is reversed in relative polarity with respect to the current of the transmission line at in a manner pointed out presently. The other winding is constantly supplied with alternating current directly from the right hand section of secondary winding 3 of the adjacent transformer T. Each of these relays, therefore, responds to reversals of the relative polarity of the current in the corresponding track circuit with respect to that of the transmission line 4; in other words, the contact fingers 8 and 10 of each relay are swung to the left when the relative polarity of the track circuit current is normal, and to the right when the relative polarity of the track circuit current is reverse, and these contact fingers are spring biased to the vertical or intermediate positionswhen the track winding of the relay isdeenergized. 7

Located at the entrance of each block is a roadside signal which is designated by the reference character S with "a subscript corresponding to the location of the signal. As here shown, thesesignals are of the type, known as lightsignals, each comprising three electric lamps G, Y and R, indicating proceed, caution and stop, respectively, when illuminated. Each signal S is controlled by contact finger 8 of the adjacent track relay in such a manner that lamp G is illuminated when the relay is energized in the normal direction, lamp Y is illuminated when the relay is energized in reverse direction, and lamp R is illuminated when-the relay is deenergized. These lamps are supplied with current from the secondary winding 3 of the adjacent transformer T, and the circuits will be obvious from the drawing without further explanation.

The relative polarity of current supplied to the track circuit of each block is controlled by contact finger 10 of the track relay for the succeeding block, in such manner that the relative polarity of the track circuit current is normal when the relay is energized in either direction, and reverse when the relay is deenergized. The immediate source of supply for each track circuit is a transformer designated by the reference character 11 with a subscript corresponding to the location, the secondary of which transformer is connected across the track rails through a reactor V. The circuit for the primary winding of the transformer 11 when relay J is deenergized, is from the middle terminal of secondary winding 3 of transformer T through conductor 12, primary windin of transformer 11 conductor 13, contact finger 10 of relay J and conductor 14 to the left hand terminal of transformer secondary 3. The current thus supplied to the track circuit of block B-'-C is of reverse relative polarity. \Vhen relay J is energized in either normal or reversed direction, the circuit for the primary winding of transformer 11 is from the middle terminal of secondary winding 3 of trans former T throu 'h conductor 12, primary winding of transformer 11 conductor 13, contact finger 10, contact 21 or 22, conductor 23 and conductor 16 to the right-hand terminal of transformer secondary 3. The current then supplied to the track circuit of block 13-0 is of normal relative polarity.

The reactor 1V comprises two windings so arranged on an iron core that, when track circuit current flows through either winding to the rails and back through the other winding, the windings are in series aiding relation, and so the device WV offers considerable impedance to such current flow and prevents abnormal flow of current from secondary winding 3 when the track rails are short-circuited by the wheels and axles of a car or train.

Located near the entrance to each block is an electric space discharge oscillator designated by O with asubscript corresponding to the location of the oscillator. As described presently with reference especially to Fig. 2, each oscillator has its filament energizing circuit suppled with energy derived from a secondary winding 30 of the adjacent transformer T, and supplies o cillating E. M. F. to an adjacent antenna 31 through an adjacent transformer 32, and each oscillator has three frequency determining circuits controlled by three relays 33, 34, 35, respectively, which have their windings in parallel with the adjacent lamps G, Y and B, respectively. Thus, each antenna 31 radiates waves of three different frequencies, say 29,000, 28,000 and 27,000 cycles per second, when the movable contact 8 of the adjacent track relay occupies its left-hand, right-hand and center positions, respectively.

Referring now to Fig. 2 especially, cur rent from line 4 is supplied to the primary winding of transformer T which has four secondary windings, 3, 30, 46 and 47. Winding 46 supplies uni-directional space current'to an electric space discharge oscillation generating tube 48 of oscillator 0 through an electric space discharge rectlfier tube 49. Vinding 47 supplies A. C. for heating the filament of tube 49.

The input circuit to rectifier tube 49 is traced from winding 46, conductor 177 to the plate of the tube and conductors 178 and 179 and condenser 53 to the filament. The D. O. output of the rectifier flows from the filament of tube 49 to the plate of tube 48 over an obvious circuit including the winding of relay 51 and choke coil 52. The space current return extends from the filament of tube 48 over conductors 180 and 181 to the mid-point of winding 30 and,

thence to winding 46 over conductor 178..

The windings of relay 51 and choke coil 52 are of high impedance to the frequencies generated by tube 48, and condenser 53 readily by-passes the input current to the rectifier and thereby prevents it from reaching:

tube 48. Oscillations generated by tube 48 are supplied to the antenna 31 through a condenser 54 and the transformer 32, the condenser 54 preventing flow of D. C. from the plate to the filament of tube 48 through.

the primary winding of transformer 32 or preventing the flow through a parallel path consisting of a resistance 55 and a tuned circuit 56 connected in series with each other. The circuit 56 determines the frequency of the oscillations generated by oscillator O, and comprises an inductance coil 60 and condensers 61, 62 and 63, the condensers being connected across the coil, only one at a time, by the armatures of relays 33, 34 and 35, respectively. The grid and the filament of the tube 48 are connected by a circuit including a coil 65 which is inductively associated with the coil 60, whereby oscillating current of a frequency determined by the constants of circuit 56 is fed back from the output circuit to the input circuit of the tube so that sustained oscillations are produced by the oscillator 0. As pointed out in United States patent to D. M. Terry, No. 1,573,948, February 23, 1926, in order to produce oscillating current of sinusoidal wave form of the frequency determined by the constants of the circuit 56, the resistance 55 should preferably be sufliciently large to limit the amplitude of the generated waves to such a value that the oscil lator operates on the most nearly linear portion of its characteristic curve representing the relation between input voltage and output current.

Referring now to Fig. 3 especially, which shows equipment such as is carried on each train, that is, to be controlled in response to track conditions, an antenna 70 receives wavestransmitted by the antennae 31 as the train passes the respective antenna 31. Preferably, the antenna 7 and each of the antennae 31 are directional in such manner a that the antenna 70 receives and each of the similarly to the choke coil 52.

. antennae 31 transmits with maximum 'effieffectively receive waves from a given an tenna 31 at any considerable distance therefrom, and cannot effectively receive waves from more than one antenna 31 at a time. 'F or example, the antenna 70 and each antenna 31 may be a loop in a plane at right angles to the track rails.

The waves received by antenna 70 are delivered to the primary winding of an input transformer 71 of a balanced demodulator DM of a heterodyne radio receiver H which includes a single frequency heterodyne oscillator O. The oscillator comprises an electric space discharge oscillation generating tube 73, and is of the same general type as oscillator O. Filament heating current for tube 73 is supplied from a secondary winding 74 of a transformer 75 which has its primary winding connected to an A. 0. generator 7 6 which may employ any type of power i. e. steam or electric, available on the train. Unidirectional space current for tube 73 is supplied from a secondary winding 77 of transformer 75 through a full wave rectifier R, and a choke coil 52 which functions The rectifier R comprises two electric space discharge rectifying tubes 78 and 7 9 which have their filaments connected in parallel and supplied with filament heating current from a secondary winding 80 of'the transformer 75. In oscillator 0, elements 32, 52, 53, 5 4, 56, 61 and are similar in structure and function to the elements of oscillator O which are designated by'the same reference characters, respectively, without the prime mark. The demodulator DM comprises two electric space discharge tubes 81 and 82, andis of the general type of the balanced duplex modulator disclosed in the U. S. patent to Carson, 1,343,307, June 15, 1920. The filaments of tubes 81 and 82 are connected in parallel with the filament of tube 73, for energization from the'secondary windin 7 1. For supplying unidirectional space current from winding and rectifier R to the space paths of tubes 81 and 82, a circuit including those paths is connected in parallel with the path through choke coil 52 and the discharge space of tube 7 3, that circuit extendingfrom the filaments of rectifier B through the winding of a relay 85, a choke coil 86, and thence to the filaments of the demodulator through two parallel branches, one of the branches containing one half of the primary winding of a demodulator output transformer 87 and the space discharge path in tube 81, and the other nected, through a transformer 90, to the common portion of the two similar input circuits of the demodulator tubes 81 and 82. The duplex demodulator suppresses transmission of unmodulated current of the frequency of oscillator O to the secondary winding of the output transformer 87 of the demodulator, but combines the Waves received by antenna 70 from the antenna 31 with the waves from oscillator O to produce in that Winding, wave components having frequencies equal respectively, to the differences between the frequency of oscillator 0 say 30,000 cycles per second, and the frequencies of oscillator 0 corresponding to the connection of the condensers 61, 62 and 63 in circuit. These components are transmitted to the windings of relays 91, 92 and 93 respectively, through frequency selective circuits 94, 95 and 96 respectively, which are shown by way of example, as narrow band filters of a type disclosed in Fig. 2 of U. S. patent to Campbell, 1,227 ,113, May 22, 1922. Energization of the relays 91, 92'and 93 causes relays 101, 102 and 103 respectively to become energized and to light a green light G, a yellow light Y and a red light R, respectively, of a 'cab' signal S. The current for operating relays 101, 102 and 103 and lamps G, Y and R is supplied from a secondary winding 100 of the transformer 7 5 through circuits which are obvious from the drawing without further expla nation.

When relay 91 operates, its armature causes energization'of an electromagnet 11 0 for releasing a catch 111 which thereupon allows a spring 112 to close a steam cut-off valve 113 in steam line 114 and thereby cut off the motive power of the train. In the case of electric motive power valve 113 corresponds to a circuit breaker or similar device. The circuit for energizing magnet 110 extends from the left hand end of secondary winding 100, through conductor 115, armature of relay 91, conductor 116, winding of magnet 110, and conductors 117 and 118, to the right hand end of winding 100. \Vhen valve 113 has thus been tripped, it can be manually restored to its open position. The normal manually operable throttle in the steam line 114 or control handle for electric power is shown at 119.

When relay 92 operates, its armature causes energization of the electromagnet for cutting off steam and an electromagnet for releasing a catch 121 which thereupon allows spring operated switch 122 to close a circuit for energizing a magnet 123 which thereupon operates an air valve 124 in the usual air line or train pipe 126 of the air brake system, so that in at dition to the cutting off of steam, the air brakes are applied for bringing the train to rest. The circuit for magnets 110 and 120 extends from winding 100 through conductor 115, armature of relay 92, conductor 127, magnet 120, conductors 128 and 116, magnet 110, and conductors 117 and 118, to winding 100. The circuit for magnet 123 extends from winding 100 through conductor 140, a variable resistance 141, conductor 142, magnet 123, switch 122, and conductor 118, to winding 100. The magnet 123 operates valve 124 against the tension of a spring, as shown and the resistance 141 is varied by a fly-ball governor 143 which is driven by the running gear of the locomotive, so that the resistance decreases and the intensity of the application of the braking means increases, as the train speed decreases. The resistance is adjusted and proportioned so that the current in the circuit at the instant the braking means is operated in response to the tripping of latch 121 at any train speed, produces the maximum desirable value of brake pressure for normal braking. As the speed of the train lecreases the brake pressure safely may be increased and this is accomplished automatically by the variable contacts carried by the governor varying resistances 141 and 151 as already described. The normal manually operable air valve is shown at 129.

WVhen relay 93 operates, its armature causes energization of the electromagnet 110, for cutting off steam, and an electromagnet 130 for releasing a catch 131 which thereupon allows a switch 132 to close a circuit for energizing a magnet 133 which thereupon opens an air valve 134 in the air line 126 so that, in addition to the cutting off of the steam, the air brakes are applied for bringing the train to rest. The circuit for magnets 110 and 130 extends from winding 100 through conductor 115, armature of relay 93, conductor 137, magnet 130, conductors 128 and 116, magnet 110, and conductors 117 and 118, to winding 100. The circuit for magnet 133 extends from Winding 100 through conductor 140, a variable resistance 151, conductor 152, magnet 133, switch 132, and conductor 118, to winding 100. The magnet 133 operates valve 134 against the tension of a spring, as shown, and the resistance 151 is varied by the flyball governor 143, so that the resistance decreases, and the intensity of the application of the braking means increases as the train speed decreases. The resistance is adjusted and proportioned to cause the initial value to be of such intensity when the braking means is operated in response to the tripping of latch 131 at any train speed. as to have the maximum safe value for that speed. This braking is emergency braking, and decelerates the train, from any initial train speed at which it is applied, along .a different timespeed curve from that which would obtain for normal braking, initiated by the tripping of latch 121.

Assuming a train (Fig. 1) in the block tothe right of C, while a train 161 passes from the block to the left of A to the exit end of block BC, the operation of the system is as follows. Train 160 short circuits winding 5 of track relay J Therefore, the contact fingers 8 and 10 of the relay are on their middle contacts. Finger 8 causes the relay 35 and the lamp R at location C to be energized, relay 35 connecting condenser 63 of oscillator 0 in circuit, so that the oscillator causes its antenna 31 to send out Waves of 27,000 cycles per second, which is the frequency corresponding to the emergency stop signal lamp R. Finger 10 causes the relative polarity of the track current supplied to the track rails of block BC, which is the current supplied to winding 5 of relay J to be reversed with respect to the current in power transmission line 4, so that relay J operates its fingers 8 and 10 to their right hand positions,

Finger 8 of relay J causes the relay 34 and the lamp Y at location B to be energized, relay 34 connecting condenser 62 of oscillator O in circuit, so that the oscillator causes its antenna 31 to send out waves of 28,000 cycles per second, which is the frequency corresponding to the caution signal lamp Y. Finger 10 of relay J causes the relative polarity of the track current supplied to the track rails of block AB, which is the current supplied to winding 5 of track relay J to be normal with respect to the current in transmission line 4, so that relay J operates its contact fingers 8 and 10 to their left hand positions.

Finger 8 of relay J causes the relay 33 and the lamp G at location A to be Q1181? gized, relay 33 connecting the condenser 61 of oscillator O in circuit, so that the oscillator causes its antenna 31 to send out waves of 29,000 cycles per second, which is the i frequency 'correspondingto "the safety signal lamp G. h The signals S and antennae 31 corresponding to the locations A, B, C, etc., are placed a distance in advance of those respective "locations equal to the maximum distance required for stopping a train by emergency braking. The engineer on train 161, seeing:

the safety light G at location A may open the circuit of the windingof relay 91 by a normally closed cab switch-162, and hold the switch open until the train antenna 70 reaches and passes beyond the field of effective influence of the antenna 31 corresponding'to location A. However, if the engineer fails to see the safety signal and acknowledge it byopening switch 162, the waves of 29,000 cycles per second emanating from the antenna 31 near location A and received by the antenna 70 in passing that antenna 31 and detected by the heterodyne receiver H, will cause a current of 1000 cycles per second to pass through the switch 162 and the 1000 cycle filter 94 and operate relay 91 and therefore cause cab lamp G to light and steam valve 113 to cutoff steam, so that the train de'celerates and the engineeror another member of the train crew is informed that a greener safety" signal has been passed with- 35? out acknowledgment. If the failure to ac-' knowledge the signal .was not due to any physicaldisablement o'fthe engineer, hecan manually resetthe catch 111 and proceed, knowing that the block AB' which he 1 is enteri'ng is clear and that the succeeding block is clear.

Train 161,upon entering block AB, short circuits track relay J which then movesits contact fingers 8 and 10 to their mid-posit-i'ons; Due to the movement of finger 8 to its mid-contact, n'e'ar; location A, the 'lamp G'becomes dark and lamp R becomes lighted and relay 35, instead of relay 33, becomes energized, with the consequencethat the an- 46 tenna 31 radiates waves of the 27,000 cycle dangerindicatingfrequency instead of the 29,000 cycle safety frequency. Dueto the movement offinger 10 0f relay'JA to its mid contact, the relative olarity of the track M cu'rren't supplied to t e track rails of the block in the-"rear of location A and to the winding 5 of the track relay of that block now becomesreverse of normal, andconsequent'lythat relay causes the extinguishing" 'ter relay then causes the extinguishing of When train 161 reaches a point from whichthelighted caution lamp -Y near location B is visible, the engineer may open the circuit of the winding of relay 92 by a normally closed cab switch 163, and hold the switch open until the train antenna 7 0 reaches and passes beyond the field of influence of the antenna 31 near location-B. However, if the engineer fails to see the caution signal and acknowledge it by opening switch 163, the waves of 28,000 cycles persecond emanating fromvantenna 31 and received by the antenna in passing. and detectedby the heterodyne receiver H on=the train, will'cause a current of 2,000 cycles per second to pass through the 2,000 .cycle. filter 95 and operate relay 92 and therefore cause cab lamp Y tolight and steam valve11'3 to cut-ofi steam and air valve 124'to apply the air brakes for normal braking,.so'that the train decelerates and the engineer or another member of the train crew is informed that a yellow orcaution signal has been passed without acknowledgment. If the failure to acknowledge-the signal was 9 not due to-physical disablement ofv the engineer he can manually reset the catches 111 and 122andproceed, knowing that the block BC which he is entering is clear but that the next succeeding block is not clear.v

As train 161- passes from block AB to block BC, winding 5 of track relay J becomes deenergizedi, Consequently, winding 5 of track relay J becomes energized, but with current of relative polarity-the reverse of normal, so that the contact fingers 8 and 10 of the relay J A move from their center or danger positions to their right hand or'caution positions. This movement of finger 10 causes the relative polarity of the track current supplied to the track rails of the block in advance of location A and to the winding 5 of the track relay of that block to change from reverse of normal to normal.- The latthe yellow caution light associated there- ,with' and the lighting of the green safety lamp associated therewith, and causes the antenna 31 associated therewith to radiate the 29,000 cycle safety indicating: frequency instead of the 28,000 cycle-caution indicating frequency.

The movement of contact finger 8 of track relay J from its center position to its right hand position causes the extinguishing of the red light associated therewith and the lighting of the yellow caution lamp associated therewith, and causes the antenna 31 associated therewith to radiate the 28,000

cycle caution indicating frequency instead 125' of the 27,000 cycle danger indicating frequency. I

The deenergization of winding 5 of track relay J and the consequent movement-of its 7 contact fingers from their right hand positions to their center positions causes the aspect of the associated signal S to change from the yellow or caution condition to the red or danger condition, and causes the frequency radiated from the antenna 31 associated therewith to change from the 28,000 cycle caution indicating frequency to the 27,000 cycle danger indicating frequency.

Thus the train 161 while in block BC is protected by the danger signals near the entrance of that block and by the caution signals near the entrance of the preceding block. When the train 161 reaches a point from which the lighted danger lamp It near the location G is visible, the engineer should close valve 119 and open valve 129 or otherwise bring the train to a stop before the train antenna 7 0 reaches the field of influence of the antenna 31 near that location. Upon a failure to so stop the train, the waves of 27,000 cycles per second emanating from that antenna 31 and received by the antenna 7 0 in passing and detected by the heterodyne receiver H on the train, will cause a current of 3,000 cycles per second to pass through the 3,000 cycle filter 96 and operate relay 93 and therefore cause cab lamp It to light and steam valve 113 to cut off steam and air valve 134 to apply the air brakes for emergency raking, so that the train is brought to rest before entering the block to the right of C and the engineer is informed that he has passed a danger signal. The switch 132 and valve 134 are preferably in a locked or sealed inclosure, so that they can be reset only after the lock has been opened or the seal has been broken. The train conductor may be authorized to reset them.

In case of failure to supply space current to the demodulator tubes 81 and 82, the relay 85 releasesits armature and causes a cab lamp 170 to be energized from secondary winding 74, to notify the engineer of the failure.

In case of failure to supply space current -to tube 48 of the oscillator O at any location such as A, B or G, the relay 51 which has its winding in the space current supply circuit of the oscillator releases its armature and, through conductors 17 5 and 17 6, shortcircuits the track rails of the block behind ence of atrain in that block.

Although it will be clear that trains may be automatically controlled in accordance with the invention without necessity of visible signals, the invention is applicable to ""railways already equipped with signaling systems of types now in satisfactory operation. Preferably, in applying the invention to such systems the track circuits of the systems are employed to control a radio transmission system of the general type of the one specifically disclosed herein, the radio transmission system and the automatic train control devices which it operates serving as an adjunct to the existing signaling system. Thus the invention can be used With or instead of any existing standard railway block signaling system, without entailing changes in clearances or structural details on either the rolling stock or the right of way. The train equipment can be installed on as many units as desired vwithout affecting other units; the track equipment can be installed on as many signal blocks as desired without affecting other blocks or interrupting trafiic; and equipped and unequipped trains and track may be used indiscriminately. (except that the automatic train control will function only when equipped trains are passing over equipped track.)

hat is claimed is:

1. In combination, a source of waves dife fering in frequency, a body movable relatively to said source, means responsive to said waves for controlling the motion of said body, said means comprising a source of waves of frequency differing from said other frequencies, means for combining said waves from said sources to produce resulting waves of frequencies different from the. frequencies of said combined waves, and means responsive to said resulting waves for con trolling the motion of said body.

2. The combination with a block system comprising blocks of track insulated from each other, a three position track relay connected to each of said blocks at the beginning of the block, means for applying electromotive force to the end of the block, each of said track relays normally assuming a given one of its three positions, and means controlled by deenergization of each track relay for causing the preceding track relay to assume a second of its three positions, of means in the neighborhood of each relay controlled by the relay for directionally radiating waves of frequencies corresponding respectively to the positions to which the relay is operated, a body movable on said track, power supply means for causing motion of said body, normal braking means for said body, emergency braking means for said body, a detector carried by said body, for detecting said waves differing in frequency to produce respectively corresponding detected Waves differing from each other in frequency, means responsive to the detected waves corresponding to the normal positions of said relays to control said power supply means, and responsive to the detected Waves corresponding to said second positions of the relays to control said power supply means and said normal braking means, and responsive to the detected waves corresponding to the third positions of the relays to control said power supply means and said emergency braking means, and self-restoring means, on said body, manually operable for preventing said detected waves corresponding to the normal positions of said relays from controlling said power supply means, and self-restoring means, on said body, manually operable for preventing said detected waves corresponding to sald second positions of the relays from controlling said power supply means and said normal braking means.

3. A system comprising a track, means at a fixed point on the trackway but independent of the rails of the track, for directionally transmitting radio waves difi'ering from each other in frequency, directional radio receiving means, movable past said point, for effectively receiving said waves 1n the immediate neighborhood of said point only, and means responding to said received waves of different frequencies selectively in accordance with their frequencies.

4. A system comprising means for generating unmodulated waves differing from each other in frequency, a single detector for detecting said waves to produce corresponding detected waves differing from said first mentioned waves and from each other in frequency, frequency selective circuits selective respectively to said different detected waves, and means connecting all of said frequency selective circuits in operative relation to said detector at the same time.

5. The combination with means for transmitting sets of waves, said sets difiering from each other with respect to frequency, of means movable relatively to said transmitting means and comprising a single detector for detecting all of said waves to produce corresponding sets of detected waves differing from said first mentioned sets in frequency, frequency selective circuits for respectively selecting said sets of detected waves, and means responsive to said selected sets of detected waves for controlling the motion of said movable means.

6. An automatic train control system comprising a track, a train movable on said track, speed reducing means for said train,

means responsive to the condition of said track for rendering said speed reducing means operative, and means for increasing automatically the intensity of application of said speed reducing means as the velocity of said train decreases.

7 An automatic train control system comprising a track, a train movable on said track, braking means for said train, and means responsive to different conditions of said track ahead of said train for decelerating said train along different time-speed curves corresponding to said different conditions, respectively, said decelerating means comprising means responsive to the speed of -my name this 29th day of November, A. D.-

' LAURENCE E. MELHUISH.

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