US1588227A - Railway-traffic-controlling apparatus - Google Patents

Description

June 8 1926.

H. o. HOLTE RAILWAYTRAFFIC CONTROLLING APPARATUS 1924 2 Sheets-Sheet 1 Filed July 31 W O T N E V m r w Q Q U QQsm v I mm m wN @& N IQ, .I'IL wm 1 ATTORNEY 2 Sheets-$heet H. o. HOLTE v RAILWAY TRAFFIC CONTROLLING APPARATUS Filed July 31 June 8 1926.

INVENTOR: I A- .(Q. 5, BY

LE -(2C- 051% N 1 ATTORNEY Patented June 8, 1926.

UNITED. STATES 1,588,227 PATENT OFFICE.

HAROLD O. HOLTE, 0F WILKINSIBURG, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

RAILWAY-TRAFFIC-CONTROLLING APPARATUS.

Application filed July 81, 1924. Serial No. 729,211.

My invention relates to railway traffic controlhng apparatus, and particularly to apparatus of the type comprising train carried governing apparatus controlled by energy received from the trackway. More particularly, m invention relates to a paratus of suc type in which the tram carried apparatus comprises vibration or tuned reed relays.

I will .describe two forms of railway trafiic controlling apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one form of railway trafiic controlling apparatus embodying my invention. Fig. 2 is a view showing one modification of the a paratus illustrated in Fig. 1 and also embo ying my invention.

Similar reference characters refer to similar parts in both views.

Referring first to Fig. 1, the reference characters 1 and 1 designate the track rails of a railroad over whlch traflic normally moves in the direction indicated by the arrow. These track rails. are divided, by means of insulated joints 2, into a' pluralit of successive track sections AB, B- etc. Each track section is provided with a track circuit includin a track relay and a track transformer. ach track relay is designated by the reference character K with an appropriate exponent and is connected across the rails adjacent the entrance end of the associated section. Each track transformer is designated by the reference character T with an exponent corresponding to the location and has a secondary winding 5 connected across the rails adjacent the exit end of the associated section. An

impedance 4 is interposed, as usual, between the secondary 5 of each track transformer and one rail 1* of the corresponding section.

Each section is further. provided with a 1trackway signal designated by the reference character S with a suitable distinguishing exponent. These signals S may be of any suitable form and as here shown are three position semaphore signals each capable of indicating proceed, caution or stop. These signals are controlled by means not shown in the drawing. The control of these signals S forms no art of the present invention, and it is su cient for present pur oses the signal indicates stop; when the cor-.

responding section is unoccupied but the 1 section next in advance is occupied, the signal displays a caution indication, and when the corresponding section and the section next in advance are both unoccupied, the signal indicates proceed. I

Associated with each si al S is a circuit controller 9 sooperated t at contact 9"-9 is closed when the signal indicates stop, and that contact 99 is closed when the signal indicates caution or proceed.

Associated also with each signal is a circuit interrupter designated by the reference character U with a suitable exponent. As here shown, each interrupter is a mechanical device comprising a rotatable commutator 12 of conducting material having its periphery provided with a plurality of teeth 12*. The space between each two adjacent teeth is filled with a segment 12 of insulating material. A fixed contact 13 is arranged to engage the segments 12 and the teeth12 alternately as the commutator revolves. The commutator 12- is arranged to be rotated at a uniform speed by some suitable means such as a motor 14 constantly supplied with energy from a suitable source such as alternator M over line wires ,3 and 3".

Each track transformer is supplied with alternating current from a line transformer designated by the reference character H with an exponent corresponding to the location and having a primary winding 8 constantly connected with line wires 3 and 3".

Referring particularly to the a paratus located at point B, when signal S indicates stop, primary 6 of track transformer '1 is connected directly with secondary 7 of line transformer H through contact 9+ Under these conditions alternating current is continuously supplied to section A-B. \Vhen, however, signal S displays a proceed or a caution indication, contact 9"-9 is closed, so that transformer T is supplied with energy from transformer H through commutator 12 and contact 13 of the interrupter IT. This commutator serves to periodically interrupt the alternating current and the parts are so designed and proportioned that the freefiency of the current supplied by alternator is greater than the frequency of interruption of contact 12-13. Under these conditions section A-B is supplied with energy in the form of a series of groups of impulses each group made up of a plurality of cycles of alternating current and each group separated from the preceding group by a time interval.

The actual frequencies used may have any reasonable values, but for purposes of explanation I will asume that the frequency of the uninterrupted alternating current is 300 cycles per second, and that the frequency of the interruptions is 15 cycles per second, that is, 15 groups per second.

As shown in the drawing a train indicated diagrammatically at V occupies the section to the right of point C. Signal S is therefore at stop and section B-O is being supplied with uninterrupted alternating current at 300 cycles per second. Signal S is at caution and signal S? is at proceed, and so section AB and the section to the left of point A are each supplied with alternating current of 300 cycles per second interrupted at the rate of 15 groups per second.

I will now proceed to explain the train carried apparatus by means of which the trackway circuits hereinbefore described control the train governing means.

Located at some convenient place upon the locomotive, as in advance of the first axle, is a pick-up device comprising two windings 13 and 13 disposed in inductive relation with the'two track rails and connected in series so that voltages induced in the two windings 13 and 13, by an alternatin'g current which flows in opposite directions in the two track rails at an instant,

are additive.

The reference character D designates a vibration relay comprising a magnetizable core 16 carrymg a winding 15. A olarized vibratable armature 17 of magnetizable material has its left hand end rigidly fastened to the core 16 and its right end' free to swing back and forth adjacent the other end of the core 16. Winding 15 of relay D is connected in series with the windings 13 and 13 and the circuit is tuned to resonance at 300' cycles per second by means of condenser 62. Furthermore armature 17 is tuned, by means of weight 17, to mechancial resonance at a frequency of 300 cycles per second. A fixed contact 17 coacts with the free tip of armature 17 so that contact 17-17 is closed once during each oscillation of the armature when the relay is energized with current at a frequency of 300 cycles per second. A transformer E is provided with a primary winding 19. con nected in series with a suitable source of direct current such as a, battery 18, and conassess? tact 1717". The secondary 20 of transformer E is connected, through a suit-able rectifier 21, with winding 15 of a second vibration relay F, similar to relay D, but having its armature 17 tuned to mechanical resonance at the frequency of the groups of impulses supplied to the trackway, that is, at 15 cycles per second. An ordinary electromagnetic relay 25 is inserted in series with relay F for reasons which will appear hereinafter. Contact 17-17 of relay F controls the supply of direct current from battery 39 to primary 22 of transformer J as will be clear from the drawing, and a direct current impulse is therefore delivered to transformer J 15 times'each second when relay F is operating. The secondary 23 of transformer J supplies energy through a i'ectifier 24 to a second electromagnetic re- The two electroma netic relays 25 and 26 control train governing means which may be of any suitable form, and as here shown comprises three separate electric lamps G, Y and R arranged when lighted, to indicate proceed, caution and stop, respectively.

When relay 26 is energized, current flows from a suitable source of energy such as a battery 27 through wire 28, front contact 29 of relay 26, wire 30, lamp G, and wire 31 back to battery 27. When this circuit is closed lamp G is energized and the train receives a proceed indication. When relay 25 is energized, but relay 26 is de-energized, current flows from battery 27, through wire 28, back contact 29 of relay 26, wire 32, front contact 33 of relay 25, wire 34, caution lamp Y and wire 31 back to battery 27. When this circuit is closed lamp Y is lighted and a caution indication is displayed on the train. When, however, relay 25 is de-energized, current flows from battery 27 through wire 35,

back contact 36 of relay 25, wire 37 lamp R, and wire 31 back to battery 27 Under this condition lamp R is lighted to display a stop indication on the train.

As illustrated in'the drawing, train V equipped with the train carried apparatus just described, occupies the section to the left of point A, which section is supplied with 300 cycle alternating currrent interrupted. 15 times per second. Relay D is therefore energized in such manner that its armature 17 vibrates at the rate of 300 cycles per second, which vibrations are interrupted 15 times er second. Each vibration of armature 1 causes an impulse in the primary r/ Winding 19 of transformer E, and hence there is induced in the secondary 20 of this transformer a series of groups of alternating current impulses, the frequency of these groups being 15 per second. The interrupted alternating current so created is rectified by rectifier 21 and hence the current supplied to winding 15 of relay F ispulsatoperates to vibrate its armature at 15 cycles per second. As a result pulsating direct current of 15 impulses per second is fed to primary 22 of transformer J. The resulting alternating current in. secondary 23 is supplied through rectifier 24, in the form of pulsating direct current, to relay 26, which relay becomes energized. It should be stated that although the supply of current to relay 25 is interrupted 15 times per second, the relay has a sufficient time interval to bridge over this period of de-energization and relay 25 therefore keeps its front contacts closed.

Proceed lamp (1 is then lighted and the train receives a proceed indication.

' Train V will continue to receive a proceed indication throughout section AB. When the train enters section BC, the uninterrupted 300' cycle current will continue to energize relay D. The energy now supplied to relay F is uninterrupted pulsating direct current having a periodicity of 300 cycles per second. Relay F does not respond to this frequency and hence the armature is at rest and relay'26 is de-energized. Relay 25 is, however, energized by the pulsating direct current supplied thereto and .hence the train receives a caution indication.

If the train V should enter the section to the right of point C, alternating current in the rails would beshunted away from the pick-up coils of train V by the wheels and axles of the-trainV'. Relay D would then be de-energized, relay F'would, of course, be

deprived of energy, and relays 25 and 26 would both be de-energized. Lamp B would then be lightedand the train would receive a sto indication.

Re erring now to Fig. 2, the apparatus here shown is modified to embody the control of thetrain carried apparatus from the trackway through the medium of two alternating currents of different frequencies, one of which currents is at times interrupted in a manner similar to that explained in connection with Fig. 1. Each of the track relays K, in Fig. 2 comprises two windings 10 and 11. One winding'lO of each such relay is constantly connected with the rails adjacent the entrance end of the corresponding section and the remaining winding 11 of each relay is constantly supplied with alternating current of a frequency different from that supplied by generator M. For example, the frequency supplied to winding 11 may be cycles per second and as here shown current of this frequency is constantly supplied to each winding 11 from secondary 51 of a transformer designated propriate exponent. The primary 52 of each such transformer P is constantly supplied with alternating current of 60 cycles per second from an alternator Q over line wires 53 and 53. Each track relay K is provided with a plurality of contacts arranged to swing to one side 'or the other in response to the relative polarity of the 60 cycle currents supplied thereto.

Referring particularly to section B,-C, when relay K is de-energized alternating 60 cycle current of one relative polarity which I shall term reverse relative polarity, is supplied to section B-C over contacts 54: and 55 of relay K? and relay K is then energized in such direction as to swing the contacts thereon to the left hand or reverse position. When relay K is energized in the reverse direction 60 cycle current of the other relative polarity which I shall term normal relative polarity is supplied to section B-C and'the contacts of relay K are swung to the right hand or normal position. When relay K is energized in the normal direction the 60 cycle current supplied to section B-C is also of normal relative polarity. Furthermore when relay K is de-energized 300 cycle alternating current is supplied continuously to section 13-0 at an intermediate oint' in the section from secondary 7 o transformer H over contacts 56 and 57 of relay K Primary 8 of transformer H is constantly supplied with 300 cycle current from generator M as in Fig. 1.

Each section is provided with an interrupter here shown as an. electromagnetic device 49 provided with a circuit including its own back contact and supplied with energy from 300 cycle line wires 3 and 3 through a rectifier 50. It follows that device 49 continuously operates to open and close contact 61. The parts may be so disposed and proportioned that the frequency of the operation of device 49 is 15 operations per second. I

When relay K is energized 'in either the normal or reverse direction transformer H supplies 300 cycle current to section B-C, adjacent the exit end of the section over contact 61 of device 49 and contacts 58 and 59 of relay K". It follows then, that under these conditions section BC is supplied with energy in the form of 300 cycle alternating current, interrupted 15 times per second to form a series of groupsiof impulses each group separated from the preceding group by a time interval.

In the train carried apparatus the 300 cycle track current supplies relays 25 and 26 through the medium of windings 13 and 13 as in Fig. 1. In addition the train carried pick up device comprises two other pick up windings 38 and 38 connected in the same manner as windings 13 and 13*" and also in inductive relation with the track rails.

1 mary 41 of a transformer O, the secondary 42 of which supplies energy torelay 44 through a rectifier 43. It will thus be clear that relay 44 is energized only when the train occupies a stretch of track which is being supplied with 60 cycle alternating current.

The circuit for the proceed lamp now may be traced from battery 27, through wire 45, front contact 46 of relay 44, wire 28, front contact 29 of relay 26, wire 30. lamp G, and

wire 31 back to battery 27. This circuit is closed only when relays 26 and 44 are encrgized, under which conditions" a proceed indication is received on the train. When relays 44 and 25 are energized but relay 26 is de-energized, a caution indiction is displayed by the lighting of lamp Y, current flowing from battery 27 through wire 45, front contact 46 of relay 44, wire 28, back 3 contact 29 of relay 26, wire 32, front contact 33 of relay 25, wire 34, lamp Y, and wire 31 back to battery 27. When relay 25 is de-energized a circuit is completed from battery 27, through wire, 35, back contact 35 36 of relay 25, wire 37, lamp R, and wire 31 back to battery 27. When this'circuit is closed lamp R is lighted and the train then receives a stop indication. It should be pointed out that when relay 44 is de- 0 energized, the left hand terminal of battery 27 is connected with wire 37 through wire 45 and back contact 46 of relay 44, and it therefore follows that the train receives a stop indication due to the lighting of lamp R- when either relay 44 or 25 1s tie-energized.

As shown'in the drawing the train V occupies the section to the right of point C. Relay K is then de-energized and section 13-0 is supplied with continuous 300. cycle current at point X and with 60 cycle current i of reverse relative polarity at point C. Relay K is therefore ener ized in the reverse direction and section --B is supplied at point B with 300 cycle current interrupted to form 15 groups per second, and also with 60. cycle alternating current of normal relative polarity. Relay K is therefore energized in the normal direct-ion and the section to the left of point A is supplied wit-h 300 cycle current interrupted at the rate of 15 groups per second, and also with 60 cycle current of normal relative polarity.

Train. V provided with the apparatus hereinbefore explained, occupies the section to the left of point A and relays D and F essee? are operated, as explained in connection with Fig. 1, by the interrupted 300 cycle current. Relays 25 and 26 are therefore both energized. At the same time relay L responds to the 60 cycle current induced in windings 38 and 38 to vibrate its armature 17. Pulsating direct current is then supplied to pr1- mary 41 from battery 40 at a periodicity of 60 impulses per second. The resulting 60 cycle alternating current supplied by secondary 42 is changed, by rectifier 43, into uni-directional current which energizes relay 44. The train then receives a proceed indication which persists as the train proceeds through section AB. When train V enters section BC the continuous 300 cycle current continues to energize relay D, and

hence relay 25, but relay F cannot respond to this current and relay 26 then becomes de-energized. Relay 44 is still energized and the train receives a caution indication. After the train passes point X in section BC, the supply of 300 cycle current to windings 13 and 13 is discontinued, such current being shunted away by the wheels and axles of train V Relays D and 25 then become de-energized and the train receives a stop indication. If the train should enter the section to the right of point 0 this stop indication would continue to be displayed since both 300 cycle and 60 cycle are shunted by the wheels and axles of train V and hence all relays 25, 26 and 44 will be de-energized. It should be noticed that any cessation of the 300 cycle current or the 60 cycle or both of them will result in a stop indication.

Although I have herein shown and described only two forms of (railway trafiic controlling apparatus embodying my invention, it .is understood that various changes and modifications may be made therein within the scope of the appended claims. without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. Railway traflic controlling apparatus comprising a stretch of railway track, means for supplying said stretch at times with uninterrupted alternating current, means for supplying the stretch at other times with interrupted alternating current, and governing means including two vibration relays selectively responsive to said currents.

2. Railway traflic controlling apparatus comprising a stretch of railway track, means for supplying alternating current to said stretch, means for at times regularly interrupting the supply of said current, a vibration relay responsive to the presence of said alternating current in the stretch, a second vibration relay responsive to the continuity of said current, and governing means controlled jointly by said two relays.

3. Railway trafiic controlling apparatus comprising a stretch of railway track, means for at times supplying energy to said stretch in the form of a series of groups of impulses each group made up of a plurality of cycles of alternating current, a vibration relay responsive to said alternating current, a second vibration relay responsive to said groups, and governing means controlled jointly by said relays.

4. In combination, a Vibration relay, means for supplying an alternating current to said relay, means for at times breaking up said alternating current into a plurality of groups each separated from the preceding group by a time interval and each group comprising a plurality of cycles of said current, a second vibration relay controlled by said first relay and having a maximum response at the periodicity of said groups, and golverning means controlled by said second re a 5. In combination, a stretch of railroad track, means for supplying said stretch with alternating current of one frequency, means for at times interrupting said current to form a series of groups of impulses, each impulse comprising a plurality of cycles of said current, a vibration relay, means for supplying said relay with current of the frequency of said alternating current, a second vibration relay, means controlled by said first relay for supplying said second relay with current of the periodicity of said groups, and governing means controlled by said second relay.

6, In combination, a stretch of railway track, means for supplying said stretch with alternating current of one frequency, means for at times interrupting said current to form a series of groups of impulses, each impulse comprising a plurality of cycles of said current, a vibration relay arranged to receive energy from the trackway and tuned to mechanical resonance at the frequency of said current, a second vibration relay tuned to mechanical resonance at the frequency of said groups, means for delivering a surge of uni-directional current to said second relay for each operation of said first relay, and golverning means controlled by said second re ay.

7. In combination, a stretch of railway track, means for supplying said stretch with alternating current-of one frequency, means for at times interrupting said current to form a series of groups of impulses, each impulse comprising a plurality of cycles of said current, a vibration relay arranged to receive energy from the trackway and tuned to mechanical resonance at the frequency of said current, a second Vibration relay, means for delivering a surge of uni-directional current to said second vibration relay once for each group of cvcles of said alternating current, a third relay inserted in series with said second relay, and governing means controlled by said second and said third relays.

8. In combination, a stretch of railway track, means for supplying said stretch with alternating current of one frequency, means for at times interrupting said current to form a series of groups of impulses, each impulse comprising a plurality of cycles of said current, a vibration relay tuned to mechanical resonance at the frequency of said alternating current, a circuit for said relay in inductive relation with the trackway and tuned to electrical resonance at the frequency of said alternating current, a second vibration relay, means controlled by said first relay for at times operating said second relay in synchronism with said groups, and governing means controlled by said second relay.

9. In combination, a first vibration relay, means for at times supplying said first relay with alternating current, means for at times breaking up said current into a series of groups of impulses, a circuit controlled by said first relay and including a source of direct current and the primary of a transformer, a second vibration relay, a circuit for said second vibration relay including a rectifier and the secondary of said transformer, and governing means controlled by said second relay.

10. In combination, a first vibration relay, means for at times supplying said first relay with alternating current, means for at times breaking up said current into a series of groups of impulses, a second vibration relay controlled by said first relay and arranged to be operated when such first relay is receiving said groups of impulses but not when the first relay is receiving continuous alternating current, and governing means controlled by said second relay.

11. In combination, a relay having a vibratable armature, means for causing said armature to vibrate continuously at times and intermittently at other times, a second vibration relay arranged to operate only when said armature vibrates intermittently, a third relay arranged to be energized when said armature vibrates continuously or intermittently, and governing means controlled by said second and third relays.

' 12. In combination, a stretch of railway track, means for supplying alternating current to the rails of said stretch, means responsive totrafiic conditions in advance of said stretch for at times interrupting said current to form a series of groups of alternating current impulseseach group being separated from the preceding group by a time interval, and governing means on a train including a first vibration relay responsive to saidalternating current whether continuous or intermittent and a second vibratio-n relay responsive to said groups of impulses.

13. In combination, a stretch of railway track, means for supplying alternating current to the rails of said stretch, means responsive to traific conditions in advance of said stretch for at times interrupting said current to form a series of groups of alternating current impulses each group being separated from the preceding group by a time interval, and governing means on a train including a first vibration relay tuned to mechanical resonance at the frequency of said alternating current, and a second vibration relay tuned to mechanical resonance at the frequency of said groups. 7

14:. In combination, a stretch of railway track, means for at times supplying said stretch with alternating current, means controlled by traffic conditions in advance of said stretch for at other times supplying said stretch with energy in the form of successive groups of impulses each group made up of a plurality of cycles of said alternating current and separated from the preceding group by a time interval, a vibration relay receiving energy from the trackway and comprising a vibratable armature tuned to resonance at the frequency of said alternating current, a second vibration relay controlled by said armature and comprising a second armature tuned to mechanical resonance at the frequency of said groups, a third relay arranged to be energized when said first vibration relay is being supplied with alternating current continuously or in groups, a fourth relay controlled by said second armature, and governing means controlled by said third and fourth relays.

15. In combination, a vibration relay, means for at times supplying said relay with energy in the form of a continuous series of impulses of uni-directional current and for at other times supplying the relay with energy in the form of a series of groups of impulses each group separated from the preceding group by'a time interval, said relay being tuned to mechanical resonance at the frequency of said groups, and governing means controlled by said relay.

16. In combination, a vibration relay, means for at times supplying said relay with energy in the form of a continuous series of impulses of uni-directional current andfor at other times supplying the relay with energy in the form of a series of groups of impulses each group separated from the preceding group by a time interval, said relay being tuned to mechanical resonance at the frequency of said groups, a second relay arranged to be energized when said vibration relay is being supplied with such continuous impulses, a third relay controlled by the vibration relay, and governing means controlled by said second and third relays.

17. In combination, two vibration relays tuned to mechanical resonance at diiferent two vibration relays tuned to mechanical:

resonance at different frequencies, means responsive toitraflic conditions in advance of said stretch for at times continuously operating one of said relays, means for at other times intermittently operating the said first relay and continuously operating the second relay, and governing means controlled by said relays.

19. In combination, a stretch of railway track, a source of alternating current of the first frequency connected at all times with the rails of the stretch, means for at times supplying said stretch with alternating current of a second frequency, means for at other times interrupting said second current to produce a series of groups of impulses each group comprising a plurality of cycles of alternating current of said second frequency and separated from the preceding group by a time interval, a first vibration relay tuned to mechanical resonance at said first frequency and arranged to receive en ergy from the trackway, a second vibration relay tuned to mechanical resonance at said second frequency and arranged to receive energy from the trackway, a third vibration relay controlled by said second relay and tuned to mechanical resonance at the frequency of said groups, and governing means controlled by said first and third relays.

20; In combination, a stretch of railway track, a source of alternating current at times connected directly with the rails of said stretch, a contact arranged to be alternately opened and closed, means for at other times interposing said contact between said source and the rails of the stretch, and governing means responsive to current in the trackway and comprising two vibration relays one arranged to operate when the rails are supplied with alternating current and the other arranged to operate only when such alternating current is intermittently supplied to the rails.

21. In combination, a section of railway track, means for at times supplying alternating current to the rails throughout the length of the section, means for at other times supplying the rails of a portion of the section with energy in the form of a series of groups of impulses each group made up said alternating current, and a second vibration relay controlled by said first relay and tuned to mechanical resonance at the frequency of said groups.

track, means for supplying alternating current to the rails of a portion only of the section when traflic conditions in advance are dangerous, means effective when trafiic conditions in advance are safe for supplying the rails throughout the length of the section with energy in the form of a series of groups of impulses each group made up of a plurality of cycles of said alternating current, a vibration relay receiving energy from the trackway and set into operation by said alternating current, and a second vibration relay controlled by said first relay and tuned to mechanical resonance at the frequency of said groups, and governing means on a train controlled by said relays.

23. In combinat1-on,'a section of railway .track, means for at all times supplying the rails of the section with alternating current of a first frequency throughout the length of the section, means for supplying the rails of a portion only of the section with alter" nating current of a second frequency when trafficconditions in advance are dangerous, means effective when traffic conditions in ad- Vance are safe for supplying the rails throughout said section with energy in the form of a series of groups of impulseseach group made up of a plurality of cycles of such second frequency and each group separated from the preceding group by a time interval, a first vibration relay receiving energy from the trackway and tuned to mechanical resonance at said first frequency, a second vibration relay receiving energy from the trackway and tuned to mechanical 1 resonance at said second frequency, a third vibration relay controlled by said second relay and tuned to mechanical resonance at the frequency of said grou s, and governing means controlledby said t ree relays.

24. In combination, a section of railway track, means for at all times supplying the rails of the section with alternating current of a first frequency throughout the length of the section, means for supplying the rails of a portion only of, the section with alternating current of a second frequency when traflic conditions in advance are dangerous, means effective when traffic conditions in advance are safe for supplying the rails in. inductive relation with the track rails and tuned to resonance at said first frequency, a second vibration relay tuned to I mechanical resonance at said second fre- 22. In comb nation, a section of rallway quency and provided with a circuit located in inductive relation to the track rails and tuned to resonance at said second frequency, a third vibration relay controlled by said second relay and tuned to resonance at the frequency of said group, three anxiliary relays one controlled by each said vibration relay, and governing means controlled by said auxiliary relays.

25. In combination, a stretch of railway track, a source of alternating current at times connected directly with the rails of said stretch, a contact arranged to be alternately opened and closed, means for at other times interposing said contact between said source and the rails of the stretch, two vibration relays one arranged to be operated when the rails are supplied with alternating current and the other arranged to operate only when such alternating current is intermittently supplied to the rails, and governing means on a train controlled solely by said vibration relays.

26. In combinatioma stretch of railway track, a source of alternating current at times connected directly with the rails of said stretch, a mechanical circuit interrupter, means for at other times interposing said contact between said source and the rails of the stretch, and governin means responsive to current in the trac way and comprising two vibration relays one arranged to operate when the rails are supplied with alternating current and the other arranged to operate onl when such alternating current is intermittently supplied to the rails. v

nating current, a relay selectively responsive to current of the frequenc of said periodic interruptions, a second re ay selectively responsive to the frequency of said alternating current for supplying said first relay with current of the frequency of said periodic interruptions, and governing means controlled jointly by said two relays.

28. Railway trafiic controlling a aratus comprisinga stretch of railway trach, means for at times supplying energy to said stretch in the form of a series of groups of impulses of alternating current, a first vibration relay responsive to said alternating current, an a second vibration relay responsive to said grou 29. In com ination, a stretch of railway track, means for at times supplying said stretch with uninterrupted alternatin current, means for at other times mechanically interrupting said current at regular periods, and traific governing means including two relays selectively responsive to said alternating current and to said periodically interrupted current respectively.

30. In combination, a stretch of railway track, means for at times supplying said stretch with uninterrupted alternating current, means for at other times mechanically interrupting said current at regular periods, two train carried relays selectively responsive to said alternating current and to said periodically interrupted current respectiveees-nae ly, and governing means on the train controlled loy said relays.

31. In combination, a stretch of railway track, means for at times supplying said stretch With uninterrupted alternating current, means for at other times mechanically interrupting said current at regular periods, '20

and trafic governing means including a relay responsive to said periodically interrupted current but not to said current.

In testimony whereof I atfix my signature. I

HARULD O. HOLTE.

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