US1720866A - Railway-traffic-controlling apparatus - Google Patents

Description

July 16, 1929. A A; H SON 1.720.866

RAILQVAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 192,8 2 Sheets-Sheet 1 OR, H. 5'. Thompson,

H ATTORNEY July 16, 1929. H. A. THOMPSON 1.720.866

V RAILWAY TRAFFIC CONTROLLING APPARATUS I I Filed Set. 1s, 192e 2 Sheets-Sheet 2 V ENTOR H, FLT/wornpsah M ATTORNEY Patented July 16, 1929.

UNETED STATES.

PATENT OFFICE.

HOWARD A. THOMPSON, OF EDGEWOOD BOROUGH, PENNSYLVANIA, A$SIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A

(1031 03 ATION OF PENNSYLVANIA.

RAILWAYTRAFFIG-CONTROLLING APPARATUS.

Application filed September 13, 1928. Serial No. 305,757. 9

My invention relates to railway traffic controlling apparatus, and particularly to automatic signaling apparatus of the type involving light signals. I

I will describe two forms of railway traf fic controlling apparatus embodying my 1nvent-ion and will then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view illustrating one form of railway traffic controlling apparatus embodying my invention. Fig. 2 is a similar view showing a modified form of the apparatus illustrated in Fig. 1, and also embodying 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 stretch of railway track over which traffic normally moves in the direction 111- dicated by the arrow. These track rails are divided, by means of insulated joints 2, into a plurality of successive track sections BC, (1 D, etc. Each such track section 18 provided with a track circuit comprising a source of current located the exit end of the section, and a track relay located at the entrance end of the section. As here shown, the source of current for each track circuit is a track transformer designated by the reference character E with an exponent corresponding to the location, and having its secondary 3 connected across the rails. The primary 4 of each transformer E is constantly connected with the terminals X and Z of a suitable source of alternating current not shown in the drawing. The track relay for each track section is designated by the reference character F with an exponent corresponding to the location, and comprises a track winding 5 which is constantly con nected with the rails, and a local winding 6 which is at times supplied with alternating current in a manner which will be described hereinafter.

Each track section is provided with a line transformer designated by the reference character K with an exponent corresponding to the location, and comprising a primary 18 which is constantly supplied with alternating current from an alternator L over line wires 49 and 50, and a secondary 17 which is divided into three sections 17 and 17 Each track section is also provided with a line relay designated by the reference character H with an exponent corresponding with the location. Each line relay H comprises a local winding 9, a reverse control winding 7, a normal control winding 8, and four contacts 12, 13, 14, and each capable of being moved into a left-hand or reverse position, a vertical or middle position, and a right-hand or normal position. Referring particularly to line relay H the winding 9 of this relay is constantly supplied with alternating current from the terminals X and Z. The winding 7 of this relay is also constantly supplied with alternating current over a circuit which passes from section 17 of secondary 17 of line transformer K through Wires 19 and 20, winding 7 of line relay H and wires elO and 21 back to section 17". Winding 8 of relay H is provided with three circuits. The first circuit for this winding passes from section 17 of secondary 17 of line transformer K through wires 19 and 23, winding 8 of relay H front contact 24; of track relay F wire 25, back contact 26 of track relay F and wire back to section 179 of secondary 17 of line transformer K l V hen this first circuit is closed, the current which flows in winding 8 of relay H is of the same relative polarity as the current flowing in winding 7, and this current flowing in winding 8 therefore aids the effect of the current flowing in winding 7 Under these conditions relayH is energized in the reverse direction. The magnitude of this current in winding 8 is such that if winding 7 should become open-circuited for any reason when this first circuit is closed, relay H would still be energized in the reverse direction. The second circuit for winding 8 of relay H passes from section 17 of secondary 17 ofline transformer K, through wires 19 and 28, windingS of relay H front contact 24 of track relay F wire 25, front contact 26 of track relay F wire 27, reverse contact 15 of line relay H and wire 28 back to section 17 b of secondary 17 of line transformer K hen this second circuitis closed, the current which flows in winding 8 of relay H has approximately thesame magnitude as the current flowing in winding 7 of this relay,

but is of the opposite relative polarity, so I that this current in winding 8 neutralizes the effect of the current in winding 7, and relay H therefore closes its middle contacts. The third circuit for winding 8 of relay H passes from section 17 b of secondary 17 of line transformer K in series through wires 19 and 23, winding 8 of relay H, front contact 2 1 of track relay F wire 25, front contact 26 of track relay F wire 27, and thence through middle contact 15 of line relay H and wire 29 back to section 17 of secondary 17 of line transformer K or through normal contact 15 of line relay H and wires 30 and 29 back to sections 17 of secondary 17 of line transformer K When this third circuit for winding 8 of relay H is closed, current from both windings 17 and 17 of transformer K flows in winding 8, and this current is of approximately twice the magnitude of the current flowing in winding 7, and is of the opposite relative polarity from the current flowing in winding 7, so that this current in winding 8 opposes and exceeds the effect of the current in winding 7 and relay H therefore closes its normal contacts. If all of the circuits for winding 8 are open, the contacts of relay H are swung to their reverse positions under the influence of windings 9 and 7 The circuits for the remaining line relays are similar to the circuits ust traced for line.

relay H", and will be readily understood from the drawing.

The supply of current to the winding 6 of each track relay is controlled by the reverse contact 12 of the associated line relay and by the front contact 16 of the track relay itself. Referring particularly to track relay F, for example, when reverse contact 12 of line re lay H is closed current is supplied to winding 6 of relay 1 over a pickup circuit which passes from terminal X through reverse contact 12 of line relay H, wires 31 and 32, and winding 6 of relay F to terminal hen relay F is closed, however, current is then supplied to winding over stick circuit which passes from terminal K through frontcontact 16 of track relay F wire 32, and winding 6 of relay F to terminal Z.

Locate-d adjacent the entranre end of each track section is a traclstway signal here shown as a light signal having an upper group of lamps 11, and a lower group of lamps 10. The upper group of lamps 11 comprises a green lamp G, a first yellow lamp Y a second yellow lamp Y and a red lamp R; and the lower roup of lamps comprises a green lamp G and a red lamp R When both red lamps in signal are lighted, the signal indicates stop; when the second yellow lamp Y of the upper group and the red lamp R of the lower group are both lightec the signal indicates approach; when the first yellow lamp Y of the upper group and the green lamp G of the lower group are both lighted, the signal incicates approach restricting; and when the green lamp G of the upper group and the red lamp R of the lower group are both lighted, the signal indicates proceed.

As shown in the drawing, a train indicated diagrammatically at W occupies the section immediately to the right of point D so that track relay F is tie-energized. All circuits for winding 8 of line relay H are therefore open at front contact 2 1 of track relay F and the contacts of line relay H occupy their reverse positions. A stop indication circuit for signal J is closed at back contact 33 of track relay F and current flows from section 17" of secondary 17 of line transformer K through wires 19, 39, and 38, red lamp R of the lower group, wires 37 and 36, red lamp R of the upper group, wire 35, back contact 33 of track relay F ,,and wires 3t and 21 back to section 17. The red lamp R of the upper group, and the red lamp R of the lower group are therefore both lighted, so that signal J indicates stop. Section CD is unoccupied, so track relay F is energized. The first circuit for winding 8 of line relay H is therefore closed at front contact 24: of track relay F and at back contact 26 of track relay F and the contact of relay H occupy their reverse positions. An approach indication circuit for signal J is therefore closed at front contact 33 of track relay F and at reverse contact 13 of line relay H and current flows from section 17 of secondary 17 of line transformer K through wires 19, 39, and 38, red lamp R of the lower group, wires 37 and d3, the yellow lamp Y of the upper group, wire 42, reverse contact 13 of line relay H wires 56 and s1, front contact 33 of track relay l and wires 34 and 21 back to secondar 17'. The yellow lamp Y of the upper group and the red lamp R of the lower group are therefore lighted, and signal J indicates approach. In section BG, track relay F is energized and the second circuit for winding 8 of line relay H is therefore closed at front contact 2 1 of track relay F and at reverse contact of line relay H so the contacts of relay H occupy their middle positions. An approach restricting indication circuit for signal J is closed at front contact 33 of track relay F and at middle contact 14- of line relay H and current flows from section 17 of secondary 17 of line transformer K through wires 19, 39, and 47, green lamp G of the lower group, wire 16, yellow lamp Y of the upper group, wire 45, middle contact 14: of line relay H wire 53 and 41, front contact 33 of track relay F and wires 3% and 21 back to'section 17 of secondary 17. The yellow lamp Y of the upper group and the green lamp G of the lower group are therefore lighted, so that signal J indicates approach restricting. Track relay F at point A is energized, and the third circuit for winding 8 of relay H is therefore closed, so

that the contacts of relay H occupy their normal positions. A proceed indication circuit for signal J A is therefore closed at front contact 33 of track relay F and normal contact 15 of line relay H and current flows from section 17? of secondary 17 of line transformer K through wires '19, 39, and 38, red lamp R of the lower group, wire 37, green lamp G of the upper group, wire 48, normal contact 14 of line relay H wires 53 and 41, front contact- 33 of track relay F and wires 34 and 21 back to section 17" of secondary 17 of line transformer K. The green lamp G of the upper group and the red lamp R of the lower group are therefore lighted so that sig nal J indicates proceed.

It will be noted that since the pick-up circuit for each track relay includes a reverse. contact 12 of the associated line relay, if, for any reason, the line relay fails to become energized in the reverse direction while the corresponding section is occupied by a train, then when the train leaves the section, the pick-up circuit for the track relay will remain open, and the track relay will fail to become energized. As a result, the signal for the corresponding section will remain at stop, and the failure of the line relay would be detected. For example, I will assume that winding 7 or winding 8 of line relay H ,-or both, become o )en-circuited, and that a train enters section A-B. When the train enters the section, track relay F becomes de-energized, thereby opening its stick circuit at its front contact 16, and also opening all three circuits for winding 8 of line relay H at front contact 24 of track relay F Since a winding of line relay H is now open circuited, this relay becomes de-energized, and the reverse contacts of the relay do not close. When the train passes out of section AB, the pick-up circuit for track relay F is open at reverse contact 12 of line relay H so track relay F does not pick up. Signal J therefore remains at stop after the train has passed out of section AB, and the failure'of line relay H will then be detected.

In the modified form of apparatus shown in Fig. 2, the detailed arrangement of the approach restricting and proceed indication circuits for each signal has been modified so that the energy for the approach restricting and proceed indications of each signal J is supplied by the line transformer for the section next in advance. Referring to signal J for example, the approach restricting indication circuit for this signal passes from section 17 of secondary 17 of line transformer K through Wire 28, reverse contact 15 of line relay H wire 27, front contact 26 of track relay F wire 25, front contact 24 of track relay F wire 44, middle contact 14 of line relay H wire 45, yellow light Y of the upper group of signal J wire 46, green lamp G of the lower group, wires 47, 39, 19

and 54, line Wire 49, and wire 54, back to section 17 of secondary 17 of line trans? former K The proceed indication circuit for signal J passes from sections 17 and 17 b of secondary 17 of line transformer K, through wire 29, middle contact 15 of line relay H 3, wire 27, front contact 26 of track relay F wire 25, front contact 24 of track relay F wire 44, normal contact 14 of line relay H wire 52, resistor 51, wire 48, green lamp G of the upper group of signal J wire 37, red lamp R of the lowergroup, wires 38, 39, 19 and 54 line wire 49, and Wire 54 back tosections 17 a and 17 b of secondary 17 of line transformer K This circuit is also provided with a branch which passes from wire 29 through wire 30 and normal contact 15 of line relay H to wire 27. In other respects the apparatus is similar to that shown in Fig. 1, except that the circuit for winding 8 of each relay H, which includes a front contact of the associated track relay and a back contact of the line relay next in advance is omitted. The circuits for the remaining signals are similar to the circuits for signal F As shown in Fig. 2, the section to the right of point D is occupied by the train W. Track relay F is therefore de-energized. All circuits for Winding 8 of line relay H are open at front contact 24 of track relay F and relay H is therefore energized in the reverse direction. The stop indication circuit for signal J is closed at back contact 33 of track relay F, and signal J therefore indicates stop.

Section CD is unoccupied, and track relay F is therefore energized. All circuits for winding 8 of line relay H are open at front contact 26 of track relay F, and relay H is therefore energized. in the reverse direction. The approach restricting indication circuit for signal J is therefore closed, and signal J C indicates approach restricting.

Section B-C is unoccupied, and track relay F is energized. The second circuit for Winding 8 of line relay H is closed over reverse contact 15 of relay H and front con tact 26 of relay F and this relay is therefore energized in its middle direction. The approach indication circuit for signal J is therefore closed, and signal J B indicates approach.

Section AB is unoccupied, and track relay F is energized. The third circuit for winding 8 of line relay H is closed over middle contact 15 of relay H and front contact 26 of relay F and line relay H is therefore energized in its normal direction. The proceed indication circuit for signal J is therefore closed, and signal J indicates proceed.

One advantage of supplying the energy for the approach and proceed indications for each signal from the line transformer for the section next in advance of the signal in the manner previously described, is that if the line relay associated with the signal should fail to become energized in the reverse direction for any reason, when the section next in advance is occupied, the signal would become dark and the failure of the line relay would be detected. For example, if line relay I-I should fail to become energized in the reverse direction when the section to the right of point D is occupied by a train as shown in the drawing, as would be the case if winding 7 of this relay became open-circuited for any reason, all indication circuits for signal J would then be open, and signal J would be dark. The improper operation of relay H would therefore readily be detected.

It will be noted that the proceed indication circuit for each signal includes a resistor 51. The electro-motive force supplied to the proceed indication circuit for each signal is greater than that supplied to the other indication circuits for each signal, and the normal function of the resistor 51 is to prevent the electromotive force impressed across the lamps in the proceed indication circuit from exceeding the value of the electromotive force impressed across the lamps in the other indication circuits. The resistor 51, however, also prevents the associated signal from displaying a false proceed indication as would be the case under some conditions of operation it the resistor 51 were not provided. For example, if winding 7 of line relay H should be come open-circuited with the apparatus in the condition in which it is shown in the drawing, relay H would then become falsely energized in the normal direction by the current in winding 8, and the contacts of relay H would occupy their normal positions, instead of their middle positions. Under these conditions, if resistor 51 were not provided, signal J would indicate proceed instead of approach restricting. Since resistor 51 is included in this circuit, however, the electromotive force impressed across the lamps comprising the pr ceed indication for signal J is not sufficient to light the lamps above a dull glow so that signal J will not display a normal proceed indication, and the failure of relay H will be detected.

Although I have herein shown and described only two forms of railway traffic 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. In combination, a stretch of railway track, a line relay for said stretch comprising three windings, means for constantly supplying two of said windings with current, means controlled by traffic conditions in said stretch for supplying the remaining winding with current, means controlled by traffic conditions in advance of said stretch for at times varying the strength of the current supplied to said remaining winding, and governing means controlled by said relay.

2. In combination, a stretch of railway track, a track relay for said stretch responsive to trafiic conditions in said stretch, a line relay for said stretch comprising three windings, means for separately supplying two of said windings with current, means controlled by said track relay for at times supplying said remaining winding with current, means controlled by traffic conditions in advance of said stretch for varying the strength of the current supplied to said remaining winding, and traffic governing means controlled by said track relay and said line relay.

In combination, a stretch of railway track; a relay for said stretch comprising a first, a second, and a third winding; means for constantly supplying said first and second windings with current, means for at times supplying said third winding with current which neutralizes the effect of the current in said second winding, means for at other times supplying said third winding with current which opposes and exceeds the effect of current in said second winding, and governing means controlled in part by said relay. 7

it. In combination, a stretch of railway track divided into track sections, a relay for each track section having a local winding, a reverse control winding, and a normal control winding, means for constantly supplying the local winding and the reverse control winding of each relay with alternating cur rent, means effective when the associated track section and the section next in advance are unoccupied for supplying the normal control winding of each relay with alternating current which neutralizes the effect of the alternating current in the rcverse'control winding, means effective when the associated section and the two sections next in advance are unoccupied for supplying the normal control winding of each relay with alternating current which opposes and exceeds the effect of current in the reverse control winding; and a railway signal for each section controlled in part by the associated relay and arranged to indicate stop, approach, approach restricting, or proceed, depending upon traffic conditions in advance.

5. In combination, a stretch of railway track, a track relay for said stretch, a line relay for said stretch comprising a first, a second, and a third winding; means for con stantly supplying said first and second windings with current, means controlled by a front contact of said track relay for at times supplying said third winding with current which neutralizes the effect of current in said second winding, means also controlled by a front contact of said track relay for at other times supplying said third winding with current which opposes and exceeds the effect of current in said second winding, and a railway signal controlled by said track relay and said line relay.

6. In combination, a stretch of railway track, a track relay for said stretch, a line relay for said stretch comprising a first, a second, and a third winding, means for constantly supplying saidfirst and second windngs with current, means controlled by a front contact of said track relay for at times supplying said third winding with current which neutralizes the effect of current in said second winding, means also controlled by a front contact of said track relay for at other times supplying said third winding with current which opposes and exceeds the effect of current in said second winding; and a railway signal controlled by said track relay and said line relay in such manner that said signal indicates stop when said track relay is de-energized but that said signal indicates approach,

approach restricting, or proceed when said track relay is energized depending upon whether said third winding is tie-energized, supplied with current which opposes the effect of current in said second winding, or supplied with current which opposes and exceeds the effect of current in said second winding, respectively.

7. In combination, a stretch of railway track, a source of alternating current con nected with the rails of said stretch, a track relay having a track winding connected with the rails of said stretch and also provided with a local winding; a line relay for said stretch comprising a first, a second, and a third winding, and provided with middle, normal, and reverse contacts; a circuit for the local winding of said track relay controlled by a reverse contact of said line relay, a stick circuit for said track relay including a front contact of the relay, means for constantly supplying the first and second windings of said line relay with alternating current, means for at times supplying the third winding of said line relay with current which neutralizes the effect of the current in said second winding, means for atother timessupplying the third winding of said line relay with current which exceeds and opposes the effect of current in said second winding; a railway signal for said section capable of indicating stop, approach, approach restricting, or proceed; means controlled by a back contact of said track relay for causing said signal to indicate stop, means controlled by a front contact of said track relay and a reverse contact of said line relay for causing said signal to indicate approach, means controlled by a front contact of said track relay and a middle contact of said line relay for causing said signal to indicate approach restricting, and means controlled'by a front contact of said track relay and a normal contact of said line relay for causing said signal to indicate proceed.

8. In combination, a stretch of railway track divided into track sections, a source of alternating current connected with the rails of each track section, a track relay for each track section having a track winding con nected with the rails and also having a local winding; a line relay for each section having a local winding, a reverse control winding, and a normal control winding, and provided with middle, reverse, and normal contacts controlled jointly by said windings; a circuit for the local winding of each track relay controlled by a reverse contact of the associated line relay, a stickcircuit for each track relay, means for constantly supplying the local winding and the reverse control winding of each. line relay with alternating current; means controlled by a front contact of the associated track relay, a front contact of the 7 track relay for the section neXtin advance,

and a reverse contact of the line relay for the section next in advance for at times supplying the normal control winding of each line relay with alternating current which neutralizes the effect of the current in said re verse control winding; means controlled by a front contact of the associated track relay, a front contact of the track relay for the section next in advance, and either a middle or normal contact of the line relay for the section next in advance for at other times supplying the normal control winding of each line relay with current which'opposes and exceeds the eifect of current in the reverse control winding; a signal for each track section capable of indicating stop, approach, approach restricting, or proceed; means controlled by a back contact of each track relay for causing the associated signal to indicate stop, means controlled by a front contact of each track relay and a reverse contact of the associated line relay for causing. the associated signal to indicate approach, means controlled by a front contact of each track relay and a middle contact of the associated line relay for causing the associated signal to indicate approach restricting, and means controlled by a front contact of each trackrelay and a normal contact of the associated line relay for causing the associated signal to indicate proceed. i

9. In combination, a stretch of railway track divided into track sections, a source of alternating current connected with the rails of each track section, a track relay for each track section havinga track winding connected with the rails and also having a local winding; a

line relay for each track section having a local winding, a reverse control winding, and a normal control winding, and provided with reverse, middle, and normal contacts controlled jointly by said windings; means for constantly supplying the local winding and the reverse control winding of each line relay with alternating current, means con trolled by a front contact of the associated track relay and a front contact of the track relay for the section next in advance as well as a reverse contact of the line relay for the section next in advance for at times supplying the normal control winding of each line relay with alternating current which naturalizes the effect of the alternating current in the reverse control winding; means control led by a front contact of the associated track relay, a front contact of the track relay for the section next in advance, and either a middle or a normal contact of the line relay for the section next in advancefor at other times supplying the normal control winding of each line relay with alternating current which opposes and exceeds the effect of current in the reverse control winding; means controlled by a reverse contact of the associated line relay for supplying the local winding of each track relay with alternating current, a stick circuit for the local winding of each track relay, a railway signal for each track section having an upper and a lower group of electric lamps; the upper group of each sig nal comprising a green lamp, a first and second yellow lamp, and a red lamp; the lower group in each signal comprising a green lamp and a red lamp; a stop indication circuit for each signal including the red lamp of the upper group and the red lamp of the lower group as well as a back contact of the associated track relay; an approach indication circuit for each signal including the second yellow lamp of the upper group and the red lamp of the lower group as well as a front contact of the associated track relay and a reverse contact of the associated line relay; an approach restricting indication circuit for each signal including the first yellow lamp of the upper group and the green lamp of the lower group as well as a front contact of the associated track relay and a middle contact of the associated line relay, and a proceed indication circuit for each signal including the green lamp of the upper group and the red lamp of the lower group as well as a front contact of the associated track re lay and a normal contact of the associated line relay.

10. In combination, a stretch of railway track, a source of alternating current connected with the rails of said stretch, a track relay having a track winding connected with the rails of said stretch, a line relay for said stretch comprising a first, a second, and a third winding, means for constantly sup plying said first and second windings with alternating current, means controlled by a front contact of said track relay for at times supplying said third winding with alternating current which aids the effect of current in said second winding, means for at other times supplying said third'winding with alternating current which neutralizes the effect of current in said second winding, means for supplying said third winding at still other times with alternating current which opposes and exceeds the effect of current in said second winding, and governing means controlled by said line relay and said track relay.

11. In combination, a stretch of railway track divided into track sections. a source of alternating current connected with the rails of each track section, a track relay for each track section having a track winding connected with the rails and also having a local wind ing; a line relay for each track section having a local winding, a reverse control winding, and a normal control winding, and provided with reverse, middle, and normal contacts controlled jointly by the windings of the line relay; means for constantly supplying the local winding and the reverse control winding of each linerelay with alternating current; means controlled by a front contact of the associated track relay and a back contact of the track relay for the section next in advance for supplying the normal control winding of each line relay at times with alternating current which aids the effect of current in the reverse control winding, means controlled by a front contact of the associated track relay and a front contact of the track relay for the section next in advance as well as a reverse contact of the line relay for the section next in advance for supplying the normal control winding of each line relay atother times with alternating current which neutralizes the effect of the alternating current in the reverse control winding, means controlled by a front contact of the associated track relay and a front contact of the track relay for the section next in advance as well as either a middle or normal contact of the line relay for the section next in advance for supplying the normal control winding of each line relay at still other times with alternating current which opposes and exceeds the effect of current in the reverse control winding; means controlled by a reverse contact of each line relay for supplying the local winding of the associated track relay with alternating current, a stick circuit for the local winding of each track relay, a railway signal for each track section having an upper and a lower group of electrical lamps; the upper group of each signal comprising a green lamp, a first and second yellow lamp, and a red lamp; the lower group in each signal comprising a green lamp and a red lamp; a stop indication circuit for each signal including the red lamp of the up per group and the red lamp of the lower group as well as a back contact of the associated track relay; an approach indication circuit for each signal including the second yellow lamp 'of the upper group and the red lamp of the lower group as well as a front contact of the associated track relay and a reverse con tact of the associated line relay; an approach restricting indication circuit for each signal including the first yellow lamp of the upper group and the green lamp of the lower group as well as a front contact of the associated track relay and a middle contact of the associated line relay, and a proceed indication circuit for each signal including the green lamp of the upper group and the red lamp of the lower group as well as a front contact of the associated track relay and a normal contact of the associated line relay.

12. In combination, a stretch of railway track divided into track sections, a source of alternating current connected with the rails of each track section, a track relay for each track section having a track winding connec ed with the rails and also having a local winding; a line relay for each track section having a local winding, a reverse control winding, and a normal control winding, and provided with reverse, middle, and normal contacts controlled jointly by the windings of the line relay; means for constantly supplying the local winding and the reverse control winding of each line relay with alternating current; means controlled by a front contact of the associated track relay and a front contact of the track relay for the section next in advance as well as a reverse contact of the line relay for the section next in advance for at times supplying the normal control winding of each line relay with alternating current which neutralizes the effect of the alternating current in the reverse control winding; means controlled by a front contact of the associated track relay, a front contact of the track relay for the section next in advance, and either a middle or a normal contact of the line relay for the section next in advance for at other times supplying the normal control winding of each line relay with alternating current which opposes and exceeds the effect of current in the reverse control winding; means controlled by a re verse contact of the associated line relay for supplying the local winding of each track relay with alternating current, a stick circuit for the local winding of each track relay, a railway signal for each track section having an upper and a lower group of electric lamps; the upper group of each signal comprising a green lamp, a first and second yellow lamp, and a red lamp; the lower group in each signal comprising a green lamp and a red lamp; a stop indication circuit for each signal in cluding the red lamp of the upper group and the red lamp of the lower group as well as a back contact of the associated track relay, an approach indication circuit for each signal including the second yellow lamp of the upper group and the red lamp of the lower group as well as a front contact of the associated track relay and a reverse contact of the associated line relay; an approach restricting indication circuit for each signal including the first yellowlamp of the upper group and the green lamp of the lower group as well as a front contact ofthe associated track relay, a middle contact of the associated line relay, a front contact of the track relay for the section next in advance. and a reverse contact of the line relay for the section next in advance; a proceed indication circuit for each signal including the green lamp of the upper group and the red lamp of the lower group as well as a front cont-act of the associated track relay, a normal contact of the associated line relay, a front contact of the track relay for the section next in advance, and either a middle or a normal contact of the line relay for the section next in advance.

In testimony whereof I aflix my signature.

HOWARD A. THOMPSON.

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