US2076930A - Railway signaling system - Google Patents

Description

April 13, 1937. H. s. YOUNG RAILWAY SIGNALING SYSTEM Original Filed April 15, 19:55 v 2 Sheets-Sheet 1 INVENTOR Henry 5. Ybung. M

HIS ATTORNEY April 13, 1937. H. s. YOUNG RAILWAY SIGNALING SYSTEM 2 Sheets-Sheet 2 Original Filed April 13, 1935 QQQNEQ INVENTOR Henry S. Yozmy: BY

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HIS ATTORNEY Patented Apr. 13,

PATENT OFFICE RAILWAY SIGNALING SYSTEM Henry S. Young, Wilkinsb urg, PaQ, as'signonto The Union Switch & Signal Company, Swiss-'- vale, Pa.,a corporation of Pennsylvania Application April 13, 1935, Serial No. 16,185 Renewed July 30, 1936 24 Claims.

The present invention relates in general to-railway signaling systems, but more particularly to improvements in automatic block signaling sys-, tems. One feature ofthe invention has to do with the use of apparatus and circuits enabling advantage to be taken of an existing alternating current supply paralleling the railway, or available at the respective signal locations, in such a mannertthat clearfcontrol of the signals, may be accomplished by employing alternating current, and caution control of the signals may be accomplished .by employment of direct current. Aaiu rth'er feature resides in the provision of means enabling both the clear and caution control to be exercised over a conductor common to all signals and but one other line wire extending between the signals of adjacent sections. There are also numerous other features not specifically mentioned, but which will appear from time to time during the progress of the specification.

The invention is illustrated in two sheets of drawings wherein, Fig. l diagrammatically illustrates the invention applied to the control of semaphore type signals arranged at the junctions of adjoining track sections of a stretch of railway track; Figs. 2 and 3 illustrate different manner in which the battery charging circuits forming a part of the signaling system may be varied; while Fig. 4 shows the invention applied to the control of color-light signals located at the junctions of adjoining track sections in the same manner as arethe semaphore signals of Fig. 1.

The application of theinvention as illustrated by Fig. 1 will first be described. The reference.

control relays H and D for the associated signal,

and an alternating current relay K. The relay H is of the slow acting type and when energized completes a, circuit for moving the associated semaphore signal to,caution position. The relay D is arranged to operate by direct current received from a bridged rectifier B when such rectifier'is fed alternating current via the secondary winding of a transformer X. The primary winding of the transformer X normally receives alternating current from the secondary S3 of a transformer W at the next signal location in advance. For example, the primary winding of transformer IX; receives current from the secondary winding=$3 of transformer 3W. This circuit first extends through the signal contact 3A, thewinding of alternating current relay 3K and back tothe other side of winding S3 via the common conductor. The relay 3K picks up over this circuit and at its front contact and armature I8 then extends the connection of one terminal of the secondary S3 to the conductor 6L, through front contacts of track relay 6T, resistor IZ, the primary winding oftransformer IX, conductor 2, and thence back to the other terminal of the secondary- S3 via the common conductor. The D or clear relay of a signal, when energized, completes a circuit through the signal to hold it inits iclear position For example, withrelay ID energized the signal I .is' held in its clear positionby circuits completed b y front contacts I I, I2, and- I3 of relay ID. "I'hese circuits extend from the plus side of batteryiCl throughfront contacts ll and I2 to ffcaution and clear operating conductors l5 "and IB extending'to signal I, and from the minus terminal of battery Cl, over the common conductor and conductor 2, through front contacts l3 of relay ID to conductor l1 extending to] signal I. I

The same line conductors over which the primary winding of a transformer X is supplied with alternating current to effect energization of the fclear or D relay of a signalare' also employed as a part of the circuit of the H or caution relay of a signal. For example, the energizing circuit of relay IH extends from I the plus terminal'of'battery C2, the back contact and armature l8 of relay 3K,'lin'e conductor 6L, front contacts' of relay 5T, the winding of relay lH, back contact l4 of relay 1D and back over conductor 2 and"'the common co-nductorto the minus side of battery C2. It will be observed that part of the current flowing over conductor 6L also passes via resistor'lZ and the primary winding of the trans-, formerlX. The resistor IZ is provided in this latter circuit to prevent too muchcurrent being shunted from relay IH. When the H relay of a signal is energized its co'ntacts'Zl and 22 close a circ'uitffor moving the associated signal to its caution, position. 1 For example, 'if relay iI-I is picked up, the caution circuitofflsignal I is completed. Thi'scircuit extends from the plus sidedfybatteryicl, through the front contact and armature22 of relay IH, caution conductor I5 to the signal I and from the minus side of battery CI, the common conductor, conductor H and the front contact 2| of relay IH to the conductor ll extending to signal I.

Since the L conductor of a section includes front contacts of the track relay of the associated section the operating current for both relays D and H of a section is interrupted whenever the section is occupied. When both the D and H relays of a signal are deenergized the signal will be in its stop position and will, at its A contacts open the circuit of the associated K relay.

At each signal location a secondary S2 of the associated transformer W feeds alternating current to a bridged rectifier BR, which in turn feeds direct current through a resistor Y at the proper voltage to maintain the associated battery C properly charged. The lamp employed in the semaphore signal is continuously energized by alternating current supplied to it via a secondary SI of transformer W.

As shown in the drawings, all sections of the stretch are unoccupied, and at least two sections in advance of section 8-9 are assumed to be also unoccupied; accordingly, all track relays T and all D relays are energized, and all signals are in their clear position.

It will now be assumed that a train enters section 6-! and that accordingly the track relay GT of this section becomes deenergized. With the contacts of track relay 6T open, the line conductor BL is interrupted and relay ID becomes deenergized. The relay ID on releasing, at back contact I4 prepares an operating circuit for relay II-I and at front contacts I I and I2 disconnects the plus terminal of battery CI from the caution and clear operating conductors I5 and I6 of the associated signal I. The signal I accordingly moves to its stop position in the usual manner. The relay ID also, at the front contact of its armature I3, disconnects the conductor H from the branch conductor 2 of the common conductor and accordingly from the minus terminal of battery CI, and at its back contact closes a shunt about the caution operating circuit of signal I. This shunt path extends from the back contact of armature I3 through the back contact and armature 22 of relay IH to the caution conductor I5 of signal I, and from the armature I3 of relay ID to the conductor I! of the signal. Since in this type of signal it is necessary for the caution circuit to be energized to move the signal to clear position, it will be evident that the traced shunt path fully guards the signal against its being falsely cleared while relays IE and ID are both deenergized. When the signal I returns to its stop position its contact IA opens and therefore disconnects the alternating current from relay IK and from the line conductor 5L. The relay 1K accordingly releases its armature I8, which, at its back contact connects the plus side of battery CI to the line conductor 5L. When the train clears the section preceding 6'I the battery potential applied to conductor 5L becomes effective to energize the H relay at the preceding signal location to control the movement of the signal of the preceding section from its stop to its caution position.

When the train enters section 'I-B track relay 'lT releases and interrupts the feed circuit for relay 3D. When relay 3D releases, it interrupts points in the clear and caution circuits of signal 3 and places a shunt about its caution operating circuit in the same manner as the corresponding relay ID of section 6-! controls signal I. When signal 3 returns to its stop position, its contact 3A opens the circuit of relay 3K, which accordingly also releases.

As soon as the train clears section 61, the track relay 6T again picks up and, with relay 3K in its release position, completes the operating circuit of relay IH. Relay IH now picks up and completes the caution operating circuit of signal I.

When signal I reaches its caution position its contact IA recloses the circuit of relay IK. The relay IK accordingly picks up its armature I8, thereby disconnecting the plus side of battery CI from the conductor 5L and reconnecting alternating current thereto to release its H relay and pick up its D relay to control the movement of the signal of the preceding section from its caution to its clear position.

When the train enters section 8-9 the track relay 8T releases and interrupts the feed circuit of relay 5D. When relay 5D releases it interrupts points in the clear and caution circuits of its signal 5 to eiTect its return to stop position.

and places a shunt about its caution operating circuit in the same manner as the corresponding relays ID and 3D controlled their signals.

The signal 5, in returning to its stop position at its contact 5A interrupts the alternating current supply to relay 5K and line conductor IL and accordingly relay 3D also becomes deenergized. When the relay 5K releases, the front contact of armature I8 opens a second point in the alternating current path to line conductor IL and at its back contact connects the conductor 'IL to the plus side of battery C3.

As soon as the train clears section 'I8, the track relay IT again picks up and, with relay 5K in its released position, completes the operating circuit of relay 3H. Relay 3H now picks up and completes the caution operating circuit of its signal 3. When signal 3 reaches its caution position its contact 3A recloses the circuit of relay 3K. The relay 3K accordingly picks up its armature I8, thereby opening the energizing circuit of relay IH by disconnecting the plus side of battery C2 from the conductor EL and reclosing the alternating current circuit through the primary Winding of transformer IX to effect the reenergization of relay ID. It may be well to mention at this time that, owing to i the slow release characteristic of relay IH it holds the caution circuit of its signal closed until relay ID has had time to pick up and close the clear circuit of the signal, so as to prevent the signal from starting to move toward its stop position when changing from its caution to its clear position.

In case a train enters a section and then recedes out of it, it will be seen that alternating current will be applied to the L conductor to pick up the D relay of such section, while the associ ated I-I relay is in its release position. Owing to the construction of the H relay, it has a high impedance to alternating current and therefore will not pick up on the alternating current volt age applied. The circuit of the H relay is, however, opened at the back contact I4 of the D relay and so prevents operation of the H relay should it, through faulty adjustment, have a tendency to do so. The opening of the back contact I4 also serves to save such alternating current power as might otherwise flow through the H relay when alternating current is being ap plied to clear the signal.

"When the train clears section 89, a circuit such as traced for relay III -will immediatelybe completedthrough the relay 5I-I'and the signal 5 will accordingly be moved from its stop to its caution position. I. i

In Fig. "l it willbe observed that the batteries at the respective signal locations are under continuous charge. With this arrangement if abattery charging rectifier BR becomes short-circui'ted'the alternating current of the secondary S2 of the transformer W will flow out over the L conductor when the associated signalis at stop at thesarne time that the plus terminal of theassociated battery is connected to the conductor. L to operate the H relay. The alternating current voltage of the secondary S2 is insufficient to operate the D relay, "however, and therefore no false operation of a signal will result from failure 'of a battery charging rectifier.

In Fig. 2 the battery charging circuit is illustrated as passing through front contact l9 of the K relay. With the battery charging circuits modified in this manner, charging of the battery occurs only while the associated signal is in its clear or caution position, and therefore while the battery itself, is disconnected from the associated L conductor. There is accordingly no opportunity with this arrangement of feeding alternating current from the secondary S2 to the L conductor.

In Fig. 3 is shown a still further "manner in which danger of alternating current from the transformer winding S2 reaching the L conductor may be avoided. In this illustration the batwhile the battery is connected to the Lconductor, and charging will only occur while the signal is in the clear or 'caution. position.

In case 'of temporary failure of thealternating current supply the K and D relays will obviously become deenergized. The Krelays will, however, complete the usual operating circuits of the H relays and accordingly the signals which were formerly displaying a clear indication will now display a caution indication. The track relays will function in the usual manner to open the line circuits as their respective sections arev occupied and accordingly the signals of occupied sections will return to stop inthenormal manner. i

In applying the invention to an automatic block signaling system employing color-light signals, as has been done in Fig. 4, the circuits are quite similar to those already described and therefore thedescription of the latter application need be only briefly gone into. In the illustration of Fig. 4, asin Fig. 1, all sections of the stretch and two or rnore'sections in advance of sections 36-41 are assumed to be unoccupied and therefore all signals areldisplaying a clear. indication. The H and D relays of thecolor-lightsystem are controlled in identically the same manner'as when employed in a system employing semaphore signals. The actual .operatingfcircuit of the H relay of the color-light system, however, is slightly different than that employed in the semaphore system. In

each H relay includesthe winding ofthe K relay associated with the next signal in advance. The windings ofthe K relaysare. of low resistance but of high'imped'ance so that they offer very little resistance to the flow of the direct current employed in operating the H relays. The circuit for an H relay of the color-light system, 43H, for example, extends from the plus terminal of battery C6, throughthe back contact and armature 48 of relay 45K, over line conductor 35L, through "the front contact of track relay 3ST, the winding of relay 43 H, back contact 49 of relay 43D, conduc-' tor 52, the common conductor, conductor 54, and through the winding of alternating current relay 45K and conductor 55 to the minus terminal of the battery CB. i I Since the color-light signals have no contact the K relays are operated through contacts of their associated H or D relay. Referring to the relay 43K, for example, its operating circuit while relay 43D is energized, extends from the left terminal of secondary S5 of transformer 4W over the common conductor, conductor 54, through the winding of relay 43K, conductor 55 and through front contact 46 of relay43Dto the right terminal of the secondary winding S5; or alternatively via the front contact 40 of relay 43H when the latter relay is the one energized, and is deenergized whenever both relays 43H and 43D are deenergized. The armature 48 of relay 43K corresponds to the armature iii of the K relays employed in the system shown in Fig. land in like manner feeds alternating or direct current to its associated line conductor 34L. 7

In the color-light system the clear and cantion lamps of the signals, identified in the drawings as the G and Y lamps of the signals, are arranged to receive their operating current from the associated alternating current source; while the stop lamps, identified in the drawings as the R lamps of the signals, are arranged to receive theiroperating current from the associated battery. Forexample, the G lamp of signal 43 is energized by alternating current supplied by the secondary winding S6 of the transformer 4W,

over a circuit extending from the right terminal of windingst, through conductor 55, the lamp G, the front contact and armature 4'! of relay 43D,

the back contact and armature 42 of relay 43H,

and. armature 44 and front contact of relay 43K to the left terminal of the secondary winding S6.

With relay 43H energized, in lieu of 43D, the Y lamp is energized by current supplied to it by the secondary winding S6 via the front contact the color-light system the operating circuit of.

accordingly the relay 43K is also in the released minus terminal of battery C5.

43D, the R lamp, and over conductor to the a In the color-light system the slow release char acteristic of the H relays prevents momentary completion of the R. lampcircuit of a signal when the indicating condition of the signal'is being changed from caution to clear, by holding the Y lamp circuit closed until the D relay has had time to pick up and establish the circuit of the G lamp of the signal.

In the color-light system, in case of failure of the alternating current supply, the K and D relays become deenergized as they do in the semaphore system. The G lamps of the signals which before such failure were lighted to display a clear indication, are accordingly retired. The K relays of such signals on releasing, however, now complete the customary energizing circuits for the H relays under their control and accordingly'the H relays become energized in the usual manner. With the H relay of a. signal location energized and the K relay of the same location deenergized, a direct curent operating circuit is established for the Y lamp of the associated signal. For example, with the relay 43H energized and the relay 43K in the released position, a circuit is completed for the Y lamp of the associated signal 43. This circuit extends from the plus terminal of battery C5, through the back contact and armature 44 of relay 43K, armature 42 and front contact of relay 43H, through the Y lamp of the signal to conductor 55 and to the minus terminal of the battery C5. It will, therefore, be seen that in applying the invention to the control of color-light signals, as in the application of the invention to the control of semaphore signals, the failure of the alternating current supply will cause the signals to display caution and stop indications in acordance with trafiic conditions.

Although the invention as described herein has only been applied to automatic block signaling systems employing semaphore and color-light signals, it will be understood that various changes and modifications may be made to apply the same to signaling systems employing other types of signals without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim is:

1. In combination, a railway track divided into sections, three relays D, H and K for each section at the entrance thereof, a line circuit extending between adjacent sections and over which either relay D or H of the rear section may be operated, means for supplying said line circuit from the forward of said sections with current suitable for operating one or the other of such relays D or H depending upon the energized or deenergized condition of the relay K of the forward section, track circuits for said sections including track relays having contacts for effecting the deenergization of the D and H relays of their associated section when such section becomes occupied, traffic controlling means at each relay location directly controlled by the D and H relays at such location, and a circuit for the K relay at such location controlled exclusively by the traflic controlling means at such location.

2. In combination, a railway track divided into sections, three relays D, H and K for each section at the entrance thereof, a line circuit extending between adjacent sections and over which either relay D or H of the rear section may be operated, means for supplying said line circuit from the forward of said sections with current suitable for operating one or the other of such relays D or H depending upon the energized or deenergized condition of the relay K of the forward section, track circuits for said sections including track relays having contacts for effecting the deenergization of the D and H relays of their associated section when such section becomes cc cupied, trafiic controlling means at each relay location controlled by the D and H relays at such location, and a circuit for the K relay at such location controlled by the traific controlling means at such location.

3. In combination, a railway track divided into sections, three relays D, H and K for each section at the entrance thereof, a line circuit extending between adjacent sections and over which either relay D or H of the rear section may be operated, means for supplying said line circuit from the forward of said sections with current suitable for operating one or the other of such relays D or H depending upon the energized or deenergized condition of the relay K of the forward section, track circuits for said sections including track relays having contacts for effecting the deenergization of the D and H relays of their associated sections when such section becomes occupied, traffic controlling means at each relay location controlled by the D and H relays at such location, and a circuit for the K relay at such location controlled by the associated D and H relays.

4. In combination, a railway track divided into sections, three relays D, H and K for each section at the entrance thereof, a line circuit extending between adjacent sections and over which either relay D or H of the rear section may be operated, means for supplying said line circuit from the forward of said sections with current suitable for operating one or the other of such relays D or H depending upon the energized or deenergized condition of the relay K of the forward section, track circuits for said sections including track relays having contacts for effecting the deenergization of the D and H relays of their associated section when such section becomes occupied, traflic controlling means at each relay location controlled by the D and H relays at such location, and a circuit for the K relay at such location closed when either of the associated D or H relays is energized.

5. In combination, a railway track divided into sections, three relays D, H and K for each section at the entrance thereof, a line circuit extending between adjacent sections and over which either relay D or H of the rear section may be operated, means for supplying said line circuit from the forward of said sections with current suitable for operating one or the other of such relays D or H depending upon the energized or deenergized condition of the relay K of the forward section, track circuits for said sections each including a track relay having a contact for effecting the deenergization of the D and H relays of its associated section when such section becomes occupied, traflic controlling means at each relay location controlled by the D and H relays at such location, and a circuit for the K relay at such location including front contacts of either of the associated D and H relays which happens to be energized.

6. In combination, a railway track divided into sections, three relays D, H and K for each section at the entrance thereof, a line circuit extending between adjacent sections and over which either relay D or H of the rear section may be operated, means for supplying said line circuit from the forward of said sections with current suitable for operating one or the other of such relays D or H depending upon the energized or deenergized condition of the relay K of the forward section, track circuits for said sections ineluding track relayshaving contactsfor effecting the deenergization of the'D and H relays of their associated sections-when such sections, become occupied, trafiic controlling means at each relay location controlled by the D and H relays at such location, and a circuit for the K relay at such location jointly controlled by the track relay of the section immediately in advance of the associated traffic controlling means and one of the two associated D or H relays.

7. In combination, a railway track divided into sections, two direct current neutral relays H and D'and an alternating current relay K for each section, a line circuit for each two adjacent sections including the H relay of the rear section and the primary winding of a transformer-rectifier'coupling between the line and the D relay of the rear section, means for supplying each of said circuits with alternating or direct current to selectively energize said D or H relays according as relay'K of the forward section is energized or deenergized, track circuits for the sections including track relays for the control of said line circuits, and traffic governing means for the sections controlled by said D and H relays.

8. In combination, a railway track divided into sections, two direct current neutral relays H and D and an alternating current relay K for each sectionya line circuit foreach two adjacent sections including the H relay of the rear section and the primary winding of a transformer-rectifier coupling between the line and the D relay of the rear section,means for supplying each of said circuits with alternating or direct current to I selectively energize said I) or H relays according as relay K of the forward section is energized or deenergized, track circuitsfor the sections including' line circuits, trafiic governing means having operating circuits selectively closed by said D and H-relays', and means for placinga shuntabout one of such operating circuits when both of said relays are deenergized. r

, 9. In combination, a railway track divided into sections; three relays D, H and Kim each section, a line circuit foreach two adjacent sections over which either relay D or H of the rear section may be operated, means for supplying each of said. circuits with current of one character or another according as the K relay of the forward section is energized or deenergized to selectively energize one or thother of such D or H relays,

means operatingwhe'n any one section is occupied by atrain to open the line circuit, traflic governing means controlled by the D and H relays, and operating" circuits for the K relays controlled bythe traffic governing means.

1 0. In combination, a railway track divided into sections, three 'rela'ysD, H and K for-each sectlon, a line circuit for each two adjacent sections over which either relay D or H of the rear section may be operated, an alternating current source and a storage battery for supplying each of said circuits with alternating or direct current to secircuits for the K relays controlled by the traffic governing means, and means for charging the battery from the alternating current source while the associated K relay is energized.

11. In combination, a' railway track divided into sections; three relays D, H and K for each section, a line'circuit for each two adjacent sections over which either relay D or H of the rear section may be operated, an alternating current source and a storage battery for supplying each of said circuits with alternating or direct current to selectively energize one or the other of said D or H relays according as the K relay of the forward section is energized or deenergized, means operating when any one section is occupied by a train to open the line circuit, trailic governing means controlled by the D and H relays, operating circuits for the K relays controlled by the tralfic governing means, and means for charging the battery from the alternating current source through front contacts of one of the associated D or H relays.

12. In combination, a railway track divided into sections, three relays D, H and K for each section, a line circuit for each two adjacent sections over which either relay D or H of the rear section may be operated, an alternating current source and a storage battery for supplying each of said circuits with alternating or direct current to selectively energize one or the other of said D or H relays according as the K relay of the forward section is energizedor deenergized, means operating when any one section is occupied by a train to open the line circuit, trafiic governing means controlled by the D and H relays, operating circuits forthe K relayscontrolled by the traflic governing means, and means for charging the battery from the alternating current source only while the associated signal is giving a proceed indication;

13. In combination, a railway track divided into sections, three relays D, H and K foreach section, a line circuit for each two adjacent sections over which either relay D or H of the rear section may be operated, an alternating current source and a storage battery for supplying each of said circuits with alternating or direct current to selectively energize one or the other of said D or H relays according as the K relay of the forward section is energized or deenergized, means operating when any one section is occupied by a train to open the line circuit, trafiic governing means controlled by the D and H relays, operating circuits for the K relays controlled by the traffic governing means, and means for chargingthe battery from the alternating current source only while alternating current is being supplied to'the associated line circuit.

14. In combination with a stretch of track divided up into track sections, a block signaling system with signals at the junctions of the respective sections, a pair of relays D and H at the junction of adjoining sections for controlling the associated signal in accordance with trafific conditions, a Krelay associated with the D and H relays, sources of alternating and direct current adjacent each signal, line circuits extending be- "tween tht sources of current at a signal and the D and H relays of the next signal to the rear, normally closed energizing circuits for the K relays of the respective sections, an energizing circuit for the D relay of each signal closed over the line circuit by the energized K relay of the signal in advance of it; a circuit for operation of the signal associated with such D relay to its clear indicating position, and including the associated direct current source; traffic controlled means effective when a section is occupied to interrupt the associated line circuit and-thereby effect the deenergization of the D relay at the entrance of the occupied section to enable theassociated signal to change from its clear to its stop indicating position, means controlled by such signal in moving to its stop position to interrupt the circuit of the associated K relay, and means controlled by such K relay for substituting the associated direct current source for the alternating current source to effect the energization of the H relay of the next signal to the rear and the deenergization of the D relay thereat, and a circuit closed by energization of such H relay for moving the latter signal to its caution position.

15. In combination with a stretch of railway track divided up into track sections each equipped with the usual track circuit including a track relay,- and also equipped with successive signal 10- cations each having a signal capable of displaying clear, caution or stop; a pair of neutral relays at each signal location for controlling the associated signal in a manner depending on which relay of the pair is energized or on the deenergized condition of both relays of the pair, means enabling the selective energization of either of said relays over a circuit comprising of but two conductors extending between the associated signal location and the next signal location in advance, and a contact of a track relay of a section intervening two signal locations included in one of such conductors.

16. In combination with a stretch of railway track divided up into track sections each equipped with the usual track circuit including a track relay, and also equipped with successive signal locations each having a signal capable of displaying clear, caution or stop; a pair of neutral direct current relays at each signal location for controlling the associated signal in accordance with traffic conditions in advance, means enabling the energization of one of said relays to the exclusion of the other from the signal location in advance over a two conductor circuit extending between such signals and including a source of direct current at the advance signal location, means including the same two conductors and a source of alternating current enabling the energization of the other relay to the exclusion of the first relay, and a contact of one of the track relays in a section of the track intervening such signal locations insuring the deenergization of both relays in case such section is occupied.

17. In combination, a forward section and a rear section of railway track, a line circuit for the rear section, a signal controlled by said line circuit and arranged to display a less restrictive proceed aspect when said line circuit is supplied with alternating current or a more restrictive proceed aspect when said line circuit is supplied with direct current, a source of alternating current, a source of direct current, means including said two sources of current for supplying said line circuit with alternating current when the forward section is unoccupied provided the alternating current is then available and for supplying said line circuit with direct current energy from said direct current source when the forward section is occupied or when the alternating current energy is absent.

18. In combination, a forward section and a rear section of railway track, a line circuit for the rear section, a signal controlled by said line circuit and arranged to display a less restrictive proceed aspect when said line circuit is supplied with alternating current or a more restrictive proceed aspect when said line circuit is supplied with direct current, a source of alternating current, a source of direct current, a relay which is energized when the forward section is unoccupied provided the alternating current source is then available and which is deenergized when the forward section is occupied or when the alternating current is absent, and contacts of said relay for connecting said line circuit with said alternating current source when said relay is energized and for connecting said line circuit with said direct current source when said relay is deenergized.

19. In combination, a section of railway track, a circuit for said section, a signal controlled by said circuit and arranged to display a normal proceed aspect or a more restrictive proceed aspect according as said circuit is supplied with alternating current or with direct current respectively, a source of direct current, a source of alternating current, and means for connecting said circuit with said direct current source or with said alternating current source in accordance with traffic conditions in advance of said section and for connecting said circuit with said direct current source when said alternating current source is absent. regardless of traflic conditions in advance. 7

20. In combination, a forward and a rear section of railway track, a pair of conductors for the rear section controlled by traffic conditions in that section, a source of energy of one character and a source of energy of another character, means effective when the forward sec tion is unoccupied to connect said pair of conductors with the source of energy of said one character, means effective when the forward section is occupied as Well as when the source of energy of said one character is not available to connect said pair of conductors with the source of energy of said other character, and signaling means for the rear section governed by said pair of conductors and selectively responsive to the character of current with which such conductors are. supplied.

21; In combination, a forward and a rear section of railway track, a source of energy of one character and a source of energy of another character, a pair of conductors for the rear section controlled by traflic conditions in that section, and means for connecting said pair of conductors with the source of energy of said one character or with the source of energy of said other character in accordance with traflic conditions in said forward section, said means being automatically effective to connect said pair of conductors with the source of energy of said one character when the source of energy of said other character is not available regardless of traffic conditions in said forward section.

22. In combination, a forward and a rear section of railway track, a source of energy of one character and a source of energy of another character, a pair of conductors for the rear section controlled by trafiic conditions in that section, means for connecting said pair of conductors with the source of energy of said one character or with the source of energy of said other character in accordance with traflic conditions in said forward section, said means being automatically effective to connect said pair of conductors with the source of energy of said one character when the source of energy of said other character is not available regardless of traflic conditions in said forward section, and traflic governing apparatus for the rear section con trolled by said pair of conductors I til 23. In combination, a forward and a rear section of railway track, a source of energy of one character and a source of energy of another character, a pair of conductors for the rear section controlled by traffic conditions in that section, means for connecting said pair of conductors with the source of energy of said one character or with the source of energy of said other character in accordance with traflic conditions in said forward section, said means being automatically effective to connect said pair of conductors with the source of energy of said one character when the source of energy of said other character is not available regardless of trafiic conditions in said forward section, and a signal for the rear section controlled by said pair of conductors said signal capable of displaying a more restrictive proceed aspect or a less restrictive proceed aspect according as said pair of conductors is supplied with energy of said one character or with energy of said other character respectively.

24. In combination, a section of railway track, a pair of conductors controlled by traffic conditions in said section, a source of energy of one character and a source of energy of another character, and means for supplying said pair of conductors with energy from the source of said one character or with energy from the source of said other character in accordance with trafiic conditions in advance of said section, said means being effective to supply said pair of conductors with energy from the source of said one character when the source of energy of said other character is absent regardless of traflic conditions in advance of said section.

' HENRY S. YOUNG.

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