US1126623A - Alternating-current block-signal system. - Google Patents

Description

ALTERNATING CURRENT BLOCK SIGNAL SYSTEM.

APPLICATION FILED PEBJI, 1905.

W2 S Q12 T M W12 G. D. EHRET.

[F U o O H (Xv-100 O Patented Jan. 26, 1915.

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THE NORRIS PETERS 60.. PHQTo-LITHQ. WASHING TON. D. c.

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wq B 113 G. D. EHRET. ALTERNATING CURRENT BLOCK SIGNAL SYSTEM.

APPLICATION FILED IBBJI, 1905. 1,12 23, Patented Ja1L26, 1915.

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THE NORRIS PETERS CO. FHGm-LITHQ. WASHINGTON. D. C.

CORNELIUS D. EHRET, OF ARDMORE, PENNSYLVANIA.

ALTERNATING-CURRENT BLOCK-SIGNAL SYSTEM.

Specification of Letters Patent.

Patented Jan. 26, 1915.

Application filed February 11, 1905. Serial No. 245,217.

To all whom it may concern Be it known that I, CORNELIUS D. Ermn'r, a citizen of the United States, residing at Ardmore, in the county of Montgomery and State of Pennsylvania, have invented a new and useful. Alternating-Current Block-Signal System, of which the following is a specification.

My invention relates to signaling systems, more especially those employed in connection with steam or electric railways to indicate the condition of the track in advance of the train or car.

I t is the object of my invention to provide a signal system wherein the usual relays and other contact devices are dispensed with in order to obviate the troubles attendant upon such types of apparatus.

It is the object of my invention to provide signaling apparatus distributed along tracks of many miles in length, the energy being supplied from a central power station. The energy is preferably of the high tension alternating current kind which is reduced in pressure for use on the track circuits.

It is the object of my invention to provide also motor operated signals, the motors being preferably of the commutatorless type; and it is the further object of my in vention to provide means whereby a single motor may operate to display both home and distant signals.

For an illustration of several of the numerous forms my invention may take, reference is to be had to the accompanying drawing, in which Figure 1 is a diagrammatic view of the circuits for a clock signal system in which a home signal only is operated. Fig. 2 is a diagran'n'natic view of the circuit arrangements in which both home and distance signals are displayed. Fig. 3 is a diagrammatic view of circuit arrangements in which a single phase current is supplied. Fig. 4; illustrates a simple means of interconnecting a sei'naphore arm or signal mechanism with a switch S, for use in the system shown in Fig. Fig. 5 is a diagram of a modified circuit arrangement.

Similar reference characters refer to similar parts throughout the drawing.

Referring to Fig. 1, 1, 2, and 3 represent the three conductors of a high tension two phase alternating current supply circuit, preferably of constant potential, a generating station being installed at intervals of say 100 miles along the railroad, each station supplying current to a distance of 50 miles in both directions. The pressure on this supply circuit may be made many thousands of volts as is commonly practised in long distance power transmission. L and 5 represent the two rails of a single track railroad, the direction of travel being assumed to be that indicated by the arrow. The track is divided into blocks, as A, B, C, D, at desired intervals by the insertion of the insulating material 6, as is the common practice in block systems. At the entrance to each block is installed signal apparatus to indicate the condition of the block to the engineer or motorman on the train or car about to enter such block. At the end of each block, that is, at the right hand end as viewed in Fig. 1, there is installed a step down transformer T, preferably of the constant potential type, for impressing upon the track circuit a very low potential alternating current. 79 and 8 represent the primary and secondary wind ings respectively of such step down transformers. From each terminal of the secondary winding .9, connection is made by conductors 7 and 8 with the two track rails. 9 represents a non-inductive resistance whose purpose is to prevent a complete short circuiting of the secondary winding 8 of each of the step down transformers when the track rails are short circuited by the wheels and axles of a train or car. These resistances 9 are made as small as possible and yet great enough to prevent overheating of the transformer T in the case where a train or car should remain indefinitely in a block- At the entrance to each block is installed an alternating current motor, preferably of the induction or asynchronous type, in which the rotor or secondary carries a closed circuited winding without commutator or contact device of any sort. These motors are well known in the art of power transmission. In the drawings the rotor of said motor is represented by 1* while the stator or primary windings in Figs. 1 and 2, are represented by to and 10 to indicate that they are traversed by current from the different phases of the supply circuit. Each of these windings produces a component of the rotary magnetic field upon which the operation of the motor depends. An inspection of Figs. 1 and 2 will show that the track circuits of neighboring blocks are traversed by current from the different phases of the supply circuit. Thus in Fig. l the track circuit of the block A is supplied with current from the phase 1, 3, of the supply circuit; block B by current from the phase i l, 2; block C by current from the phase 1, 3

connected to the terminals of the secondary s of the step down transformer, supplying current to the neighboring block to the rear. It is thus seen that the stator windings are traversed by two phase currents, the current of one phase derived from the track circuit of the block whose condition the motor is to indicate, while the other is traversed by current of another phase supplied at the end of the neighboring block to the rear. As well understood in the art of power transmission, these dephased stator currents will cause the rotor to rotate and perform mechanical work. Since however, the rotor of each motor must start from rest, (a condition attended by very small torque when the rotor winding has as low resistance as possible, and as is the practice in power work where the rotor is torotate continuously and operate at the highest electrical eificiency) and since it must produce its maximum torque at starting, I design the rotor winding so that it shall have a higher resistance than would be consistent with high efficiency in ordinary power work. To this end of securing high torque at starting, the rotor is wound with higher resistance conductor than is common in power practice, or the rotor is wound with low resistance conductor, as in power practice, and maintained in circuit therewith is an additional resistance whereby the resistance of the entire rotor winding is maintained relatively high. The result is a high torque at starting and throughout the range of move ment of the rotor.

Directly connected to the rotor shaft is the target, semaphore, disk, or other device represented by 10, whose extent of travel is limited by the stops 11 and 12. WV represents a weight or equivalent means for giving the semaphore or target 10 a bias toward the danger position, namely the horizontal position, as shown at the entrance to block C, (Fig. 1). It is to be understood, however, that instead of directly connecting the semaphore or target 10 to the rotor shaft, any suitable intermediate gearing may be employed, in order that the rotor may make a plurality of revolutions during the move ment of the semaphore or target 10 from one of its indicating positions to another.

The operation of the system shown in Fig. 1 is as follows :When the tracks are clear the motors are energizedby the cooperation of the polyphase currents in windresultant greatly decreased or zero torque of the rotor r so that the weight N rotates the semaphore or target 10 to horizontal position, thus indicating danger is in the block C. Similarly should a fault occur anywhere between. the supply conductors 1, 3, and the rails at the end of the block C, or if a rail should be removed or broken, the

winding 10 of the motor at entrance to block C will be robbed of current with resultant movement of target 10 to danger position. With a train or car bridging the rails of block (1 the non-inductive resistance 9 at the end of block C prevents undue heating of the step down transformer T at that point which continues to maintain requisite current through the stator winding w of the motor at the entrance to block D. When the train or car 13 has moved on to block I), the target 10, at the entrance to block D moves to danger position because stator winding 10 of the motor at that point is robbed of current. hen thecar or train has passed on to block D, stator windin 4.0 of the motor at the entrance to block is again energized, with resultant rotation of rotor 7', which causes the semaphore or target 10 to move to safety position as indicated by extending downwardly at an angle as shown, for example, at the entrance to block B. 7

Referring to Fig. 2, the circuit arrangements are identical with those of Fig. 1, except that provision is made for displaying both home and distant signals, that is, displaying by .the home signal the condition of the block immediately in advance, and by the distant signal the condition of the second block in advance. To. this end a reversing switch S isv inserted between the secondary s of'each step down transformer T and the track rails. As shown in Fig. 2 the two blades of the reversing switch are pivoted on the pair of contacts nearest the rails and joined by a bar of insulating material, The lower ends of the switch levers are adapted to cooperate with four contacts'in communication with the secondary s of each step down transformer T. Each switch S is mechanically connected through any suitable means such as a system of levers or gearing with the semaphore or target 10, which in Fig. 2 is adapted to assume any one of three positions to indicate safety,

warning, or danger. The switch S therefore assumes any one of the three, different positions according to the position of the semaphore arm 10.

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As shown in Fig. 4, semaphore arm 10 has pivoted thereto at 17 the rod 16 which is pivoted at its lower end at 18 to one arm of the bell crank lever 19. The bell crank 19 is pivoted at 20 to the base or frame of the apparatus. At 21 the rod 22 is pivoted to the bell crank 19 and at 23 to a connection with the insulating bar connecting the two levers of the switch S. As the semaphore arm 10 assumes different positions the switch S assumes different positions and cooperates with the contacts hereinafter referred to.

The block D being clear the rotor r of the motor at the entrance to block D is rotated in a counter clockwise direction until the target 10 has come into engagement with the stop 11. During this movement the weight W has been elevated through a certain distance. The tendency is therefore for the semaphorearm to come to horizontal position on decrease of torque in the motor. -With the arm or disk 10 in position above horizontal as shown at the entrance to block D the levers of the switch S are in engagement with the two contacts to the right.

When a train or car 13 is'bridging the rails of the block C, the stator winding w of the motor at the entrance to block C is robbed of current with the result that the semaphore arm 10 is moved to horizontal position by the weight W which has been permitted to move to its lowest position. As the semaphore arm has assumed this horizontal position, the levers of the switch S at the end of the block B have been moved into engagement with the two middle contacts, the result being the relative reversal of current in the track circuit of block B from what it normally is. In other words the current in the stator winding 10 of the motor at the entrance to block B has been relatively reversed, so that the direction of rotation of the magnetic field produced by the two windings Q02 and 10 has been reversed, with resultant reversal in direction of rotation of the rot-or 1' of this motor at the entrance to block B. In consequence the semaphore 10 is rotated to a position below horizontal until it engages the stop 12. During such rotation the weight W has been elevated a certain distance. In rotating to this position the semaphore arm 10 at the entrance to block B has shifted the switch S at the end of block A so that the levers engage the two contacts to the left. The result is that the current in the track circuit of block A is in normal direction, the same as if the target 10, at entrance to block B, were in safety position, as shown in the entrance to block D. This being so, the torque in the motor at the entrance to block A is such as to keep the semaphore arm 10 in safety position against the stop 11. From this arrangement it follows that when nearing the end of block A an engineer or motorman is warned by the position of the semaphore arm 10 at the entrance of block B that block B is clear but that there is a train or fault in block C. When the train 13 7 rent in the track circuit of block C, resulting in shifting the semaphore arm 10 at the entrance to block C to warning position, below the horizontal. In so doing the switch S at the end of block B is shifted to the left, thus returning the current in the track circuit of block B to normal direction, thus causing the semaphore arm 10 at the entrance to block B to be rotated against the stop 11 to indicate safety in block B. In moving from stop 12 to stop 11, the arm 10 at the entrance to block B moves the switch to the extreme right, thus momentarily reversing the relative direction of current in the track circuit of block A and finally reestablishing it in normal direction when the arm 10 has come into engagement with the stop 11 at the entrance to block B. The result is that the semaphore arm 10 at the entrance of block A does not change its position, because the reversal of current in the track circuit of the block A is only momentary.

Referring to Fig. 3, 14: and 15 are the conductors of a single phase high tension, preferably constant potential, supply circuit. A step down transformer T, and induction or asynchronous motor and a non-inductive resistance 9 is provided at the entrance to each block as in the case of Figs. 1 and 2. To effectively produce a rotating field in each motor, two stator windings, 1/1 and w I are provided and traversed by currents which are dephased with respect to each other. The windings w are connected through non-inductive resistances F, across the secondaries s of the step down transformers T. Between the windings 10 and the rails may be inserted an inductance winding L to produce a lagging current in the windings 00 The current in the windings w" is practically in phase with the electro-motive force of the secondaries 5, while the current in the windings w lags behind such electro-motive force because of the inductance L. In cases where the inductance of the rails is not sufficient to produce the necessary lagging current, the additional inductance L may be provided to secure the proper amount of lag. The windings v.0" and 20 being traversed by dephased currents, the motor at the entrance to each block becomes in effect a polyphase motor as in the cases of Figs. 1 and 2. The inductance L may be omitted, and the noninductive resistances 9 may be replaced by suitable inductance windings.

The operation of the system shown in Fig. 3 is the same as that shown in Fig. 1, that is, when the windings w are robbed of current, due to any fault in a block or the presence of a train in a block, the weights IV rotate the semaphore arms 10 against the stops 11, indicating danger. WVhen the windings w are again energized, the torque of the rotors r overcomes the weights IV and rotates the arms 10 against the stops 12 to indicate safety.

Making the rotor windings or the circuits of the rotor windings of relatively high resistance serves the additional useful purpose of reducing the amount of current traversing the rotor windings or their circuits when'the rotors are at either safety or warn ing positions, which they frequently occupy for an indefinite length of time.

In Figs. 1 and 2 condensers is may be inserted in the track circuits to compensate for any self induction effects which may be caused by the iron rails. The presence of these condensers is unnecessary unless the r lagging effect iaused by the rails becomes serious.

Inasmuch as it is desirable to have a very low potential. current in the track circuits while it is desirable to have a current of moderate potential in the stator windings 0.0 Q0 10 and w, the secondaries s of the transformers T of all the figures may be wound in sections so that a tap may be taken 05 to supply a low potential current to the track circuits, while the stator windings connected to such secondaries 8 may be subjected to the full potential difference developed by such secondaries. To this end the conductors 7 may be connected at one end to a track rail and at the other end to the tap in the secondaries s of the transformers T, whereby a very low potential is impressed upon the track circuits. Similar taps may be taken from the secondaries s of the transformers T of Figs. 2 and 3 for the same purpose. In Fig. 2 the contacts of the switches S would be connected to such conductors 7 while one stator winding of each motor would be subjected to the full potential of the secondary s. In Fig. 3 a similar arrangement would be made, the stator windings and the noninductive resistances F being subjected to the full potential of the secondaries s. In order that the stator windings connected with the track circuits at the beginning of each block shall be traversed by current of moderate potential, a step up transformer T may intervene between each track circuit and the associated stator winding, as shown in Fig. 5.

Though only a single track road has been shown in each of the figures of the drawin s, it is to be understood that any number of tracks may be supplied from, the same supply conductors l, 2, 3, or 14;, 15. And though the target operating motors are shown at the entrance to each block, it is to be understood that they may be placed at any other suitable position 'to, constitute overlaps when it is desired that traflic shall be in both directions on a single track.

Since it is desirable to have the potential of the current in the track circuits of all the blocks approximately the same, and since the potential of the supply circuits diminishes as the distance from the generating stations becomes greater, the ratios of transformation of the transformers T may change as the distance from the generating station changes, in order that the secondaries 8 may all deliver current at uniform potential. Or the energy supplied by the high potential circuit may be stepped down to lower potential and supplied to local supply circuits intervening between the high tension supply circuits and the transformers T. Such local supply circuits may be relatively short in length and supply current at proper potential to groups of b ocks.

From the foregoing descriptions it is seen that a block signal system is provided in which relays and kindred apparatus are entirely dispensed with, thus removing all causes and faults arising from the burning orv fusion or other troubles with the contacts. In other words there are disclosed herein block signal systems which are contactless, it being understood that the switches S of Fig. 2 are perfectly reliable as ordinary switches have come to be in the electrical arts, and are not such contacts as cause trouble in railway signal systems.

From the fact that alternating current is used the signaling systems may be operated at an economy obtainable with lone; distance high tension electrical transmission. And from the fact that alternating currents are used on the track circuits, no trouble from electrolysis at bond wires or other points is possible; nor are false signals due to leakage from other circuits or to earth currents possible since only currents of the proper frequency and of sufiieient energy will operate the motors.

The motors and the transformers, weights and other apparatus at the end of a block and the entrance to the neighboring block may be housed within the same semaphore tower base and the motors need be of small size and capacity only. There the semaphore arms are operated through gearing, the motors need only be of a rating of a small fraction of a horse power; and in the case where the si nal operated is in the nature of a target or disk within a housing, such target or disk may be directly connected to the rotor shaft and the motor may be of very small rating indeed.

- Inasmuch as the number of blocks sup- I other and independent conductors may be provided for the apparatus and will in such case be connected in circuit as the rails are shown to be connected.

It is to be understood also that lightning arresters may be applied to the high tension supply circuit and Lo the track circuits and circuit associated therewith in a manner commonly practised in long distance power transmission and in the manner practised in connection with the signal systems heretofore employed.

What I claim is 1. In a signaling system, a plurality of blocks, means for impressing alternating current of different phases upon neighboring blocks, home and distant signals, an alternating current motor for operating said home signal, said motor having windings traversed respectively by current from the phase circuits of said neighboring blocks, a switch movable with a distant signal for controlling said motor through a circuit of one of said blocks, said motor operated in response to movement of said switch for moving said home signal to indicate the position of said distant signal.

2. In a signaling system, a plurality of blocks, means for impressing alternating current of different phases upon neighboring blocks, a signal, an alternating current motor for controlling said signal, said motor having windings traversed respectively by current from the phase circuits of said neighboring blocks, a switch controlling said motor through one of said block cir cuits, and means responsive to the condition of a distant block for actuating said switch.

3. In a signaling system, a plurality of blocks, an alternating current supply circuit, means for impressing alternating current of different phases upon neighboring blocks, home and distant signals, an alternating current motor for operating said home signal, said motor having windings traversed respectively by current from the phase circuits of said neighboring blocks, means for reversing said motor, and means responsive to reversal of said motor for indicating the position of a distant signal.

4. In a signaling system, a plurality of blocks, an alternating current supply circuit, means for impressing alternating current of difl'erent phases upon neighboring blocks, a signal, an alternating current motor for operating said signal, said motor having windings traversed respectively by current from the phase circuits of said neighboring blocks, a distant signal, and means controlled thereby for reversing said motor to move said first named signal to an indicating position.

5. In a signaling system, a plurahty of blocks, means for impressing alternating current of different phases upon neighboring blocks, a signal, an alternating current motor for controlling said signal, said motor having windings traversed respectively by current from the phase circuits of said neighboring blocks, a switch for reversing said motor, and means responsive to the condition of a distant block controlling said switch.

6. In a signaling system, a plurality of blocks, an alternating current supply circuit, means for impressing alternating current of difierent phases upon neighboring blocks, a motor, a three position signal operated thereby, the windings of said motor connected in the different phase circuits of said neighboring blocks, means for reversmg said motor, said signal moved by gravity to one of its indicating positions and by said motor to its other indicating positions.

7. In a signaling system, a plurality of blocks, an alternating current supply circuit, means for impressing alternating current of difierent phases upon neighboring blocks, a motor, a three position signal operated thereby, the windings of said motor connected in the difierent phase circuits of said neighboring blocks, said signal moved by gravity to one of its indicating positions and by said motor to its other indicating positions, and means responsive to the movement of a signal of a distant block for reversing said motor.

8. In a signaling system, a plurality of blocks, a polyphase high potential current supply circuit, means for impressing a low potential single phase current upon each of said blocks, the single phase current in one block being of displaced phase with respect to the single phase current of a neighboring block, a signal, a polyphase motor for operating said signal, said motor having windings traversed by currents from the diflerent phase circuits of neighboring blocks, a switch for reversing the current in one of said block circuits for reversing said motor, and means responsive to the condition of a distant block controlling said switch.

9. In a signaling system, a plurality of blocks, a polyphase high potential current supply circuit, means for impressing low potential single phase current upon said blocks, the single phase current in one block being of displaced phase with respect to the single phase current of a neighboring block,

a signal, a polyphase motor for operating said signal, said motor having windings traversed by currents from the different phase circuits of neighboring blocks, and means responsive to the movement of a distant signal for reversing said motor.

10. In a signaling system, a plurality of blocks, means for impressing a single phase current on the track circuit of each block, a signal, a motor for operating the same, the single phase currents on neighboring track circuits being displaced in phase with respect to each other, said motor having a winding traversed by current of one phase from one track circuit, and having another winding traversed by current from the phase circuit of a neighboring track circuit, a three-position switch controlling said motor through one of said trackcircuits, and means responsive to the condition of a distant block for controlling said switch.

11. In a signaling system, a plurality of blocks, means for impressing a single phase current on the track circuit of each block, a signal, a motor for operating the same, the single phase currents on neighboring track circuits being displaced in phase with respect to each other, said motor having a winding traversed by current of one phase from one track circuit, and having another winding traversed by current of different phase from a neighboring track circuit, and means responsive to the movement of a distant signal for reversing the current in one of said neighboring track circuits.

12. In a signaling system, a plurality of blocks, means for impressing alternating current of difierent phases upon neighboring blocks, a motor, a three-position signal moved by gravity to one of its indicating positions and controlled by said motor to move to its other indicating positions, the windings of said motor traversed by currents from the phase circuits of neighboring blocks, a switch controlling said motor through one of said blocks, and means responsive to the condition of a distant block controlling said switch.

13. In a signaling system, a plurality of neighboring track circuits insulated from each other, a source of polyphase alternating current, means for impressing a single phase current upon each track circuit, the currents in neighboring track circuits being of different phases, a signal, a motor for operating the same, said motor having a winding traversed by current from one of said track circuits and another winding traversed by current of a different phase, and a reversing switch controllingthe track circuit supplying current to said first named winding.

14. In a signaling system, a plurality of neighboring track circuits insulated from each other, a source of polyphase alternating i er-.2

current, means for impressing a single phase .current upon each track circuit, the currentsin neighboringtrack circuits being of different phases, a signal, a motor for operating the same, said motor having a winding traversed by current from one of said track circuitsand another winding traversed by current of" a different phase, a reversing switchcontrolling the track circuit supplying current to said first named winding, andnieans for shifting said reversing switch in response to the movement of a distant i controlling saidmotor through one of said signal circuits, andmeans responsive to the condition of a distant signal circuit controlling said switch.

16. In a signaling system, a source of. polyphase current, a plurality of signal circuit sections insulated from each other, both signal conductors of a signal circuit insulated from the corresponding conductors of a neighboring signal circuit, means for impressing a single phase current upon each signal circuit, the currents in neighboring signal circuits beingdisplaced in phase, a signal, a motor for operating said signal, said motor having a winding traversed by the current of a signal circuit and another winding traversed by current of different phase and connected with a neighboring signal circuit, and means for reversing said motor in response to the movement of a disan nal- 17. In a signaling system, a three-position signal, an electricmotor for actuating said signalto two of its positions, means for deene iL-gizing said motor to allow said signal to be moved by gravity to its third position, a switch controlling said motor, a signal circuit, and means responsive to the condition of said signal circuit .for actuating said switch.

18. In a signaling system, an alternating current supply circuit, neighboring track circuits insulated from each other, a signal, arotarymagnetic field motor for operating said. signal, a component of said rotary magnetic I field produced by current derived from one track circuit, and another .component of said rotary magnetic field produced by current of. different phase from a circuit supplyingcurrent to a neighboring track circuit, and means for reversing said motor controlled from a distant track circuit.

19. In a signaling system, an alternating current supply circuit, neighboring track circuits insulated from each other, a signal, a rotary magnetic field motor for operating said signal, a component or said rotary netic field produced by current derived from one track circuit, and another component of said rotary magnetic field produced by current of different phase, and means for reversing said motor in response to the move ment of a distant signal.

20. In a signaling system, an alternating current supply circuit, neighboring track circuits insulated from each other, a signal, a rotary magnetic field motor for operating said signal, a component of said rotary magnetic field produced by current derived from one track circuit, and another component of said rotary magnetic field produced by current or different phase, means for reversing said motor in response to the movement of a distant signal, said first named signal moved to a difi'erent position for each direction of movement of said motor and occupying a third position in response to the action of gravity.

21. In a signaling system, an alternating current supply circuit, a signal, an induction motor for operating said signal, a primary winding of said motor traversed by current derived from a track circuit, another primary winding traversed by current of different phase supplied directly thereto independently of a track circuit, a switch controlling the direction of current in said first named winding, and means responsive to the condition of a distant track circuit con trolling said switch.

In a signaling system, a three-position signal, a plurality of neighboring signal circuits, means for impressing alternating currents of different phases upon neighboring signal circuits, a polyphase motor deriving current from neighboring signal circuits controlling movement of said signal to two of its positions, said signal being moved to its third position by gravity, a three-position switch controlling said motor through a signal circuit, and a distant three-position signal, said switch taking a different position for each different position of said distant signal.

23. In a signaling system, a three-position signal blade biased toward one position, means for mechanically actuating the same to and for holding the same in the other positions comprising a polyphase motor, signal circuits for neighboring blocks, means for impressing currents of different phases upon signal. circuits of neighboring blocks, said motor deriving current from said means, and the current of one phase of said motor derived through one of said signal circuits.

24-. In a signaling system, a third-position signal blade biased toward one position, means for mechanically actuating the same to and for holding the same in the other positions comprising a polyphase motor, neighboring signal circuits, means for impressing currents of different phases upon neighboring signal circuits, said motor deriving current from said means, and the current of one phase of said motor derived through one of said signal circuits, a switch for reversing said motor, and means responsive to the condition of a distant signal circuit controlling said switch.

25. In a signaling system, the combination with a plurality of blocks, of a signal blade for each block adapted to take three indicating positions and biased toward one of them, means for impressing current of different phases upon neighboring blocks, a motor for actuating said signal blade to two of its positions and deriving current from said means, the current of one phase delivered to said motor derived through one of said blocks, said motor de'e'nergized in response to the presence of a vehicle in a block whereby said signal moves to its third position to which it is biased, and a switch controlling the motor associated with a signal blade of another block controlled by said first-named motor.

CORNELIUS D. EHRET.

WVitnesses WM. HAMILTON, EDITH N. BAHN.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents.

Washington, I). 0.

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