US2344324A - Railway signaling system - Google Patents

Description

G. R. PFLASTERER RAILWAY SIGNALING SYSTEM Marh 14,1944.

'FiledJan. 14, 1942 2 Sheets-Sheet l INVENTOIZ GeozyaRPflamez-wn HISATTOR/VEK March 14, 1944. G.-R. PFLASTERE R V RAILWAY SIGNALING SYSTEM Filed Jan. 14 1942 2 Sheets- Sheet 2 [AP wza an ar 4 I e INVENTOR.

Patented Mar. 14, 1944 UNITED STATES PATENT OFFICE r 2,344,324 RAILWAY SIGNALING SYSTEM George It. Pfiasterer, Greenville, Pa assignor to The Union Switch and Signal Company, Swissvale, Pa, a corporation of Pennsylvania Application January 14, 1942 Serial No. 426.7 45

6 Claims. (c1. 246-33) ing movement of traflic into the sin le track stretch between two passing slidings from displays ing its clear indication whena train moving in the other direction is approaching theother end of the single track stretch.

A further object of my invention is to provide a signaling system of the type described which is arranged so that two trains approaching a single track stretch simultaneously will not both receive clear signal indications from the signals at the entrance ends ofthe single track stretch.

Another object of my invention is to provide an improved signaling system of the type described which is arranged so. thatno more line wires are required than are needed in the systems heretofore employed.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawings.

In practicing my invention I provide line circuits coextensive with the single track stretch between two passing siding's and employ direct current in these circuits to control the signals governing traflic in both directions in this track stretch. In addition, I provide means to supply alternating current over the line wires for the signals for each direction of traffic and have means responsive to this energy for controlling the clear aspects of thev signals governing entrance of trains into the single track stretch. The supply of alternating current to the line circuit for the signals for each direction of traffic is controlled so that the. supply of this energy is cut off when a train traveling in the opposite direction approaches the end of the single track stretch to thereby prevent the display of aclear indication by the signal governing. entrance of trains moving in the otherdirection in the single track stretch. 7

I shall describe one form of railway signaling system embodying my invention, and shall then point out the novel features thereof in claims.

In the drawings Figs. 1A and. 115. when placed together with Fig; 113 at the right form a diagram y of a stretch of railway track equipped with signaling apparatus embodying my invention.

In order to simplify the drawings and to enable the circuits to be more readily traced I have identified each signal by a letter and number, and each relay by a letter or combination of letters with a distinguishing prefix identifying the signal with which the relay is associated.

Furthermore, instead of showing the sources of current for energizing the various line and local circuits I have shown only the terminals of these sources. The terminals of the sources of direct current are designated B and C, while the terminals of the sources of alternating current are designated BX and OK. The, direct current may be provided by batteries, while the alterriatirig current may be supplied from a commeri move in either direction.

For purposes of illustration it will be assumed that th left-hand end of the track stretch is west, and that the right-hand end thereof is east so that train movements from left to right are eastbound, and train movements from right to left are westbound.

The track rails are divided by insulated joints into track sections; designated T with a distingu shing prefix. Each section is provided with a track circuit comprising the usual track battery connected across one end of the section rails, and a track relay, designated TR with an appropriate prefix, connected across the other end of the section rails.

The ends of the non-track circuited passing sidings PS are connected with the main track by track switches W.

Theheadblock signal 28 governs traffic on the 1, main track'movi'ng from left to right across the switch 2W at the right-hand end of the passing siding IPS into the adjacent single track stretch, while the headblock signal is governs trafiic is, 35 and IS, depending on the direction of be governed in accordance with the positionof the switches in the manner well known in the nects one terminal of the primary winding of transformer 8M to terminal BX of a source of alternating current, while the other terminal of this winding is connected to the other terminal of the source. The secondary winding of this transformer is connected in series with line wire l4 and is of such low resistance as not to substantially reduce flow of direct current in this 'circuit. On the supply of alternating current art. This control of the signals by-the switches F is not a part of this invention, andhas been omitted to simplify the. disclosure, Similarly" to the primary winding of transformer 8M energy is induced in the transformer secondary winding and is supplied over wires 14 and IE to the'primary winding of transformer EN. The

. primary Winding of this transformer is connectthe supply of energy to the relays IH and BI-I i which govern the signals is and 88 may be controlled by trafiic or other conditions in advance of these signals in any manner well known in the art. The control of the supply of energy to these relays is not a part of this invention and has been omitted in order to simplify the dis closure. p v

Each signal has associated therewith a polarized relay H, which is preferably of the retained neutral type, while the windings of these relays are of such high impedance as to substantially prevent flow of alternating current therein.

The signals each have a directional stick relay SR associated therewith, while the signals 28 and 13 have relays J associated therewith which are energized when alternating current is supplied thereto from the other end of the single track stretch as hereinafter explained.

In most instances the relay contacts are shown directly under the relay with which they are associated, but in -some cases in order to simplify the drawings relay contacts are shown separated from the 'relay, and where this is done the relay with which the contacts are associated is indicated by appropriate reference characters placed directly above therelay' contacts.

The equipment is shown in the condition which it assumes when the track stretch is vacant, and the switches 2W and 1W are in their 'normal positions in which they direct traffic neutral contacts of this relay are picked up; As

relay 8H'is energized; its contacts II] and H are picked up so that direct curent of normal polarity is supplied :over the 'line circuit consisting of line'wire l4 and common wire IE to relay BI-I so that the neutral contacts of this relay are picked up 'and the polar contacts of the relay are in their normal positions and contacts I! and I8 of the relay establish the circuitv f the green lamp G of signal 68.

In addition, contacts 20 and 2| .ofrelay-6H cause direct current of normal .polarity to be supplied over the line circuit consisting of line Wire 24 and common wire 25 to relay H so that its neutral contact 26 and its polar contact 21' cooperate to establish the circuit of the green or clear lamp G of signal 48.

'In addition, at this time contacts 28 and 29 of relay 4H cause direct current of normal polarity to be supplied over the line-circuit consisting of wire 32 and common wire 33 to relay 211 so that its contacts 35 and 36 establish the circuit to supply energy to thegreen or clear lamp As relay 8H is picked up, its contact 4U ed. across the wires l4 and 15 in multiple with the winding of relay SE. The transformer primary w inding is of such high resistance as to substantially prevent flow of direct current therein, while the winding of relay 6H is of such high impedance as to substantially prevent flow of alternating current therein.

' *On the supply of alternating current to the primary winding of transformer 6N energy is wire.

: 4H. The primary winding of transformer 4N is of such high resistance as to substantially pre-- vent flow of direct current therein, while the impedance of the winding of relay 4H is so high as to substantially prevent flow of direct current therein. 1

The secondary winding of transformer 4N is included in series with line wire 32 and is of low resistance to permit free flow of direct current therethrough. On the supply of alternating current to the primary winding of transformer 4N energy is induced in the transformer secondary winding and is supplied therefrom over the line circuit consisting of wire 32 and common wire .33 to. the primary winding of transformer 2N1which' is connected across line wires 32 and 33 in multiple with the winding of relay 2H. En-

ergy from the secondary of the transformer 2N is supplied through a suitable rectifier to the relay 2J so that contact 31 of this relay is picked up and establishes the circuit of the green lamp G of signal 28.

The relay IH is governed in any manner well known in the art by traffic or other conditions in advance of signal IS, and as the stretch is assumed-to be vacant, the neutral contacts of this relay are picked up. 'Accordingly, contacts 40 and 4| of relay IH' cause direct current of normal polarity to be supplied to the line circuitconsisting of wire 43 and common wire 33, while contact 42 of relay l H causes alternating current to be supplied to the primary winding of transformer IM, the secondary winding of which is connected in series with line wire 43.

The direct current supplied to line wires 43 and 33 feeds to relay 3H so that its contacts 45 and establish the circuit of the green lamp G of signal 38,, while contacts 48 and 49 of relay 3H cause direct current of normal polarity to be supplied over the line circuit consisting of wire '50 and common wire 25;to;relay 5H. .'Contacts 53 and 53 of relay 5H, therefore; establishthe circuit of the green lamp-G of-signal 58, while contacts 54 and 55 of relay 5H cause direct current of normal polarity to be supplied over thefi line circuit consisting of wire 5'lfand common wire l5 to relay 1H so that its contacts 59 and .66 establish the circuit to permit energy to be supplied to the green lamp G :of signal 1S.

The alternating current supplied to transform--' er IM is supplied therefrom through transformers 3N and 5N to transformer 1N from which it is supplied through a rectifier tov 'relay IJ so that its contact 6| is picked up and establishes the circuit of the green lamp G of. signal is;

The primary windings of the transformers 3N, 5N and 1N are of such high resistance as to sub stantially prevent flow of direct current therein, while the secondary windings of transformers IM, 3M and 5M are of low resistance so as to. :i-

tion, as the portions of the main track adjacent the passing sidings are vacant, alternating current is supplied from'the passing siding at either end of the single track's'tretch to the relay J at the other end of the single track stretch to there- 'by condition the associated headblock signal to display a green or clear indication;

, Operation of equipment on passage of an eastbound train; through the track stretch When an eastbound train enters the portion of the track stretch within the control limits of relay IH, the circuit of this relay is interrupted and the relay contacts release so that contact 64 interrupts the pick-up circuit of the directional stick relay ISR. The control of relay l H is arranged so that the circuit of this relay is interrupted before the train enters section IT and releases relay ITR to thereby insure that the contact 64 of relay IH interrupts the pick-up circuit of relay ISR before-this circuit is established by contact 63 of relay ITR.

At this time, therefore, contact 65 of relay l SR remains released and interrupts the circuitcontrolled thereby'for supplying energy to transformer IM. On release of the contacts of relay lI-I its contact 42 interrupts the supply or alternating current to transformer IM; with the result that energy is no longersupplied therefrom through transformers 3N, 5N and TN'to relay U,

and contact 6| of this relay releases'and interrupts the circuit of the green lamp C1 and establishes the circuit of the yellow lamp Y of signal 1S. v V

It will be seen; therefore; that as soon as an eastbound train enters the control limits of re-v 1 lay IH, the headblock' signal at the other'end of the single track stretch is caused to display its yellow or caution indication instead of its green indication so that a westbound train apcuts off the .supplyof alternating :current to transformer 8M, and thereby causes release of relay ZJ so that itscontact 31 interrupts the circuit of the green lamp G and establishes the circuit of the yellow lamp Y of signal 28, so that an eastbound train will reduce its speed before entering the single track stretch.

When the eastbound train under consideration advances into section 2T, track relay 2TH releases and its contact 66 interrupts the supply of energy to relay 2H and to transformer 2N, and thus to relay ZJ. Accordingly, contact 35 of relay 2H releases and establishes the circuit of the red or stop lamp R of signal 2S. In addition, on release of the track relay -ZTR its contact 61 interrupts the supply of direct current to the circuit of line wires 63 and 33, whil it establishes connection between these wires so that'on the supply of alternating current to the primary-winding of transformer 'IM energy Will be supplied from the transformer secondary winding over wires 43 and 33.

;On release of contact 61 :of track relay ZTR and interruption of the supply of direct current energy to line wires 43 and 33, relay 3H releases and its contact'45 establishes the circuit of the red light R of signal 38. In addition, on release 'cuit consisting of wires '5lland 25, and relay 5H releases so that its contact 52 establishes the circuit of the red lamp R of signal 55..

In addition, on release of relay 5H its con tacts 54 and 55 cut off the supply of direct current to the circuit of wires 51 and it, while its contact 12 interrupts the circuit of relay 5SR so that contact [3 of relay 58R remains released and interrupts connection from terminal B to back contact 54 of relay 5H with the result that the supply of direct current to line wires 51 and I5 is cut off when relay5H releases.

As the supply of energy to line wires 57 and i5 is cut ofi, "contact 59 of relay TH releases and 1S at the leaving end of the passing siding ZPS are placed at stop soith'a't a "westbound train will not enter the single track stretch.

When the eastbound train advances into section 3T,track relay'3TRreleases' and addiproaching the other .end of the single track .7

stretch will be notified'of the approach'of the eastbound train and'wilLreduce its speed before entering the single track stretch. a

In like mannen when a westbound trainenters the portion of the trackstretch within the con- .tionally interrupts the linecircuits consisting of Wire "32"ahd common wire 33, and of wire 43 and common wire 33.

When the train advances into section 4T, track relay lTR releases and its contact T5 interrupts the circuit of relay lI-I so that contact 26 of this relay releases and establishes the circuit of the red lamp R of signal 46. At this time contact I6 of relay 4TB interrupts line wire 56, but as 'ene'rgyis not being supplied over this wire at this time release-of-the contact (6 is without effect.

'. On. release of track'relay 4TB. its contact ll establishes the pick-up circuit for relay 4SR. This circuit also includes front contact 18 of relay 4H and is interrupted as soon as this. contact releases. As the relay 4H is of the retained neutral polar type, its neutral contacts remain picked up for a short period subsequent to interruption of the supply of energy to the relay winding, and during this period the contacts of relay 48R pick up so that its contact 19 establishes a stick circuit to maintain the relay energized after release of relay 4H. On release of contact 18 of relay 4H it establishes connection with terminal B of the source so that thereafter relay 48B is maintained energized as long as either relay 4TR or relay 41-1 is released.

As relay 4SR is energized, its contact 80 is picked up and establishes connection from terminal B to back contact 28 of relay 4H, while back contact 29 of relay 4H establishes connection from terminal C so that direct current of reverse polarity is supplied to line wires 32 and 33 When the train advances into section 5T, track relay 5TB. releases and additionally interrupts the line circuits formed by wire 50 and common wire 25, and by wire 24 and common wire 25.

When the train advances into section 6T, track relay GTR releases and its contact 8| interrupts the circuit of relay 6H, while its contact 82 interrupts the circuit of line wire 51, and its contact 83 establishes the pick-up circuit including front contact 85 of relay 6H for energizing relay BSR so that contact 86 of this relay establishes a stick circuit to maintain the relay energized after release of relay 6H.

On-release of relay 6H its contact I I establishes the circuit of the red lamp R of signal 68, while its contacts 20 and 2| establish the circuit including front contact 88 of relay 68R for supplying direct current of reverse polarity to the circuit of line wires 24 and 25.

When the train advances into section 1T, track relay lTR releases and additionally interrupts the cricuits formed by wires l4 and 5! and the common wire I 5.

On release of track relay 'lTR its contact 89 interrupts connection from line wire l4 to contact H of relay 8H, while it establishes connection between wires l4 and I5 so that the secondary winding of transformer 8M is connected directly across the wires 4 and I5 instead of being connected across these wires in series with the source of direct current. Accordingly, alternating current may be supplied from transformer 8M over line wires l4 and IE to the primary winding of transformer 6N. However, as long as relay 5TB. is released, its contact ll interrupts wire 24 so that energy is not supplied from transformer 6N to transformer 4N.

When the train advances into section 8T, track relay 8TB releases and its contact 90 establishes the pick-up circuit including front contact 9| of relay 8H for energizing relay 8SR so that the contacts of relay BSR pick up and its contact 92 establishes a stick circuit to maintain the relay 1 energized after release of relay 8H.

On release of track relay 8TR its contact 94 interrupts the circuit of relay 8H so that contacts 10 and I I of relay 8H release and cause the direct current supplied to the circuit of line wires M v and I to be of reverse polarity, while contact 40 of relay 8H interrupts one circuit for supplying alternating current to transformer 8M and establishes the circuit including front contact 95 of relay 88R for supplying alternating current to thistransformer.

. When the rear of the train vacates section. vIT, track relay I'IR picks up and establishes the circuit of relay IH, while its contact 63 interrupts one connection from terminal '13 of the source to a terminal of the winding of relay ISR. Onpicking up of the relay IH its contact 64 interrupts the connection controlled thereby from terminal B to the winding of relay ISR. so that relay- ISR remains deenergized,

On picking up of relay IH its contacts 4|] and 4| establish connections to supply direct current of normal polarity to wires 43 and 33, but at this time the supply of direct current to these wires is prevented by contact 61 of relay 2TR which is released.

On picking up of the contacts of relay IH its contact 42 establishes a circuit, to supply alternating current to the primary winding of transformer IM so that current is induced in the trans former secondary winding. As contact 61 of relay Z'I'R is released, connection is established from one terminal of the transformer secondary winding to common wire 33, While the other terminal of this winding is connected to wire 43. Accordingly, alternating current from the transformer IM is supplied over wires 43 and 33 to the primary winding of transformer 3N. However, at this time contact 16 of relay 4TB interrupts the circuit of the secondary winding of transformer 3N so that energy is not supplied beyond this transformer.

-When the train vacates section 2T, track relay 2TB. picks up and its contact 6! connectsthe secondary winding of transformer IM across the line wires 43 and 33 in series with the battery from which direct current is supplied to this circuit, while contact 66 of relay 2TH is' picked up to permit energy to be suppliedto relay 2H.

When the train vacates section 3T, track relay 3TR picks up and its contact 9'! establishes the cricuit to permit energy to be supplied to relay 3H and the contacts 45 and 46 of this relay establish the circuit of the green or clear lamp G of signal 38, while contacts 48 and 49 of relay 3H are picked up to establish the circuits to supply direct current of normal polarity to wires 50 and 25.

On picking up of contact 98 of relay 3TB the circuit for supplying direct current of reverse polarity to wires 32 and 33 is complete, and this energy feeds over these wires to relay 2H so that but as contact 82 of relay BTR is open, energy is not supplied from the secondary winding of this transformer.

When track relay 4TR picks up, its contact is closed to permit energy to be suppliedto relay 4H, while its contact 17 interrupts the connection controlled thereby for supplying energy to relay 48R, but as long as relay 4H is released,- energy continues to be supplied to relay 4SR over the back contact 18 of relay 4H. Accordingly, contact of relay 48R. remains picked up and maintains the circuit for supplying direct current of reverse polarity to wires 32 and 33.

When the train vacates section 5T, track relay 5TB picks up and its contact I00 establishes the circuit. of. relay 5H, while its contact I! is closed so that. direct current of reverse polarity is supplied over line wires 24 and 25 to relay 4-H and contacts 26- and 21 of this relay establish the circuit of the yellow or caution lamp Y of signal 4,8. In addition, contacts 28 and 29 of relay 4H change the energy supplied to Wires 32: and 33 from reverse to normal polarity, while contact 18 of relay 4H interrupts the circuit of relay 4SR andthis relay releases.

When contact I-IlI of relay TR is picked up, the circuit of the secondary winding of transformer 6N is complete so that energy is. supplied from this transformer over wires 24 and 25 to the primary winding of transformer 4N. As l ointed out above, at this time energy is. supplied to transformer 8M over the circuit controlled by contact" 95. of relay BSR, while. energy is supplied, from transformer 8M over line wires I4 and I5 to transformer 6N; I

On the supply of energy to transfonner 4N energy issupplied therefrom over line wires 3-2 and 33 to transformer 2N from which. it is supplied through the rectifier to relay 2'! to pick up contact 31 of the relay. As a result on the supply of direct current of normal polarity to line wires 33 and 32 and consequent movement of the polar contact 36' of relay 41-1 to its left-hand or normal position, the circuit including front contact 3''! of relay 2J is established to light-the green or clear lamp G of signal 2S.

As a result of the supply of energy of normal polarity to relay 5H the contacts 52- and 53 of this relay establish the circuit of the green lamp G of signal 53, while contacts and 55 of the relay are picked up to establish theconnections over which direct current of. normal polarity is supplied to wires 51 and I5 after picking up of relay BTR.

When the train vacates section 61, track relay GTR picksup, while when the train vacates: sec tion 'I'T, track relay ITRpick's-up so that its contact establishes the circuit of the relay 1H,.while its contact 89' interruptsthe connection. of the: secondary winding of transformer 8M directly across the wires I4 and I5 and connects this winding in series with the direct current source so that alternating current together with direct current of reverse polarity is supplied to Wires I4 and I5. The direct current is supplied to relay 61-1 with the result that its contacts I7 and I8 establish the circuit of the yellow lampY ofsignal' 6-S,.while-contact 85 of relay 6H interrupts the circuit of relay SSH, and contacts and M. of relay 6H cause direct current of normal polarity to be supplied to wires 24- and so that contact 21- of. relay 4H shifts to its left-hand or normal position and establishes the circuit of the green or clear lamp G of signal 48.

In addition, on picking up of the. contacts of relay 'ITR its contact. 93'establishes the circuitof the relay 1H and contacts 59and 60' of this relay establish the circuit of. the green lamp G of signal IS.-

When the train advances far enough to cause energy to again be supplied to the relay 8H, the contacts of this relay pick up so. that its contacts I0 and I I- cause the direct current supplied to line wires I4 and I5 to be of normal polarity, while its contact 9| interrupts the circuit of' relay SSH; and its contact establishes a circuit to supply alternating current to the primary winding 'of transfbrmertM. I t I From the foregoing it willbeseen that when an eastbound train approaches the east end of I I passing-siding IT; relay I-I-I-i's r leased. n ut 7 therein within the scope of the appended claims off the supply of alternating current to transformer IM so that energy is not supplied to relay Id at the other end of the single track stretch and thus prevents the display of a clear indication by that signal. At this time, if the portion of the main trackadjacentsiding ZPS is vacant, alternating current'energy is supplied to transformer 8M and is supplied therefrom to relay 2J so that signal 25 displays its clear indication.

When the eastbound train enters the single track stretch, the signals inthe rear-of the train arecontrolled so as to Warna following train of the presence of the first train. When the train advances beyond signal 48, direct current of" reverse polarity is suppliedtoline wires 32 and 33 and signal. 2S displays its yellow or caution indication. When the train advances beyond signal 63', direct current of reverse polarity is supplied to relay 4H, and signal 48 is caused to display its caution indication, while the direct current supplied to Wires 32 and 33 is changed to normal polarity. In addition, when the train is in advance of signal (is, alternating current is supplied from transformer 8M through transformers 6N, 4N, and 2N to the relay 2J so that the signal 28' will display a clear indication and thus permit a following train to proceed without reducing speed.

Furthermore, it Wlll be seen. that when the eastbound train advances into section 8T so that relay BI-I releases, the supply of alternating current to the transformer 8M is maintained by the circuit establishedby contact of relay BSR so that; the relay 2J will be maintained picked up k to cause the signal 2S to provide its clear indication.

The operation of the equipment on movement of. a westbound train through the track stretch is similar ,to that for movement of eastbound trains and will not be traced in detail. When the westbound train advances close enough to the west end' of passing siding ZPS to cause release of relay 81-1, the supply of alternating current to transformer 8M is cut off, and accordingly relay 2J releases to prevent the display of a clear indication by signal 23' and to cause this signal to provideits yellow or caution indication.

When the westbound .train advances beyond signal 3S, alternating current is again supplied through the transformers 3N, 5N; and IN, and the relay U is picked up to permit the display of theclear indication by signal is, while after the train advances into section IT and causes release of relay II- I, the supply of alternating current is maintained by the circuit established by contact 65 of relay I SR so that relay IJ is maintained picked up to maintainthe display of the clear indication by signal 18.

It willbe seen,.thereiore,. that when the portion of the main track opposite either of. the passing sidings is. occupied by a. train approaching the single track stretch, the headblock signal at the otherzend of the single track stretch is prevented from displaying; its clear indication. Accordingly,. if atrainpasses. that headblock signal and entersthe single'track stretch, it will do so at reduced speed andwill. be able to stop before colliding with: the; train moving in the opposite direction which entered the single track stretch at the other end.

Although I have herein shown and described only one form ofrail way signaling system embodying my invention, it is understood that various changesand. modifications may be made 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 railroad track having a first and a second passing siding which are connected by a single track portion over which traflic moves in both directions, the rails of the single track portion being divided by insulated joints into a plurality of successive block sections, each block section having at the end thereof nearest the first passing siding a signal governing entrance into the block section of trains moving from the first to the second passing siding, the signals each being capable of displaying a plurality of indications, the signal for the block section adjacent the first passing siding being capable of providing a clear indication and at least one restrictive indication, each section having means governed by traific conditions in said section and controlling the signal for such section, and means responsive to occupancy of the portion of the track stretch beside the second passing siding and controlling the signal for the block section adjacent the first passing siding in such manner as to permit the display of the clear indication by said signal only when the portion of the track stretch beside the second passing siding is vacant or is occupied by a train entering said track portion from the single track portion.

2. In combination, a stretch of railroad track having a first and a second passing siding which are connected by a single track portion over which trafiic moves in both directions, a first signal at the end of the single track portion adjacent the first siding and a second signal at the end of the single track portion adjacent the second siding, said signals controlling entrance of trains into the single track portion and each be ing capable of displaying a stop, a clear, and at least one restrictive proceed indication, a first control means governed solely by traflic conditions in said single track portion for at times causing said first signal to display its stop indication, at other times to display a restrictive proceed indication, and at still other times to permit said first signal to display its clear indication, means responsive to trafiic conditions in the portion of the track stretch beside the second passing siding and cooperating with said first control means to cause said first signal to display its clear indication only when the portion of the track stretch beside the second passing siding is vacant or is occupied by a train entering said track portion from the single track portion, a second control means governed solely by trafiic conditions in said single track portion for at times causing said second signal to display its stop indication, at other times to display a restrictive proceed indication, and at still other times to permit said second signal to display its clear indication, and means responsive to trafiic conditions in the portion of the track stretch beside the first passing siding and cooperating with said second control means to cause said second signal to display its clear indication only when the portion of the track stretch beside the first passing siding is vacant or is occupied by a train entering said track portion from the single track portion.

3. In combination, a stretch of railroad track having a first and a second passing siding which are connected by a single track portion over which traflic moves in both directions, the rails of the single track portion being divided by insulated joints into a plurality of successive block sections, each block section having at the end thereof nearest the first passing siding a signal governing entrance of trains moving from the first to the second passing siding into the block section, the signals each being capable of displaying a plurality of indications, the signal for the block section adjacent the first passing siding being capable of providing a clear indication and at least one restrictive proceed indication, each block section having a pair of conductors governed by trafiic conditions in said section and having electroresponsive means energized over the conductors for said section, each such electroresponsive means being responsive to energy of one character and controlling the signal for the associated block section, means governed by trafiic conditions in the portion of the track stretch beside the second passing siding for supplying energy of a second character to the conductors for the block section adjacent said passing siding, the conductors for each block section except the section adjacent the first passing siding having associated therewith means effective on the supply thereto of energy of said second character to cause energy of said second character to be supplied to the conductors for the block section adjoining on the side nearest the first passing siding, and means responsive to the supply of energy of said second character to the conductors for the block section adjacent the first passing siding and governing the display of the clear indication by the signal for said block section.

4. In combination, a stretch of railroad track having a first and a second passing siding which are connected by a single track portion over which tramc moves in both directions, the rails of the single track portion being divided by insulated joints into a plurality of successive block sections, each block section having at the end thereof nearest the first passing siding a signal governing entrance of trains moving from the first to the second passing siding into the block section, the signals each being capable of displaying a plurality of indications, the signal for the block section adjacent the first passing siding being capable of providing a clear indication and at least one restrictive proceed indication, each block section having a pair of conductors governed by traffic conditions in said section and having electroresponsive means energized over the conductors for said section, each such electroresponsive means being responsive to energy of one character and controlling the'signal for the associated block section, means effective when and only when the portion of the track stretch beside the second passing siding is vacant or is occupied by a train entering said track portion from said single track portion for supplying energy of a second character to the conductors for the block section adjacent said secadjacent the first passing siding and governing the display of the clear indication by the signal for said block section.

5. In combination, a stretch of railroad track having a first and a second passing siding which are connected by a single track portion over which traific moves in both directions, the rails of the single track portion being divided by insulated joints into a plurality of successive block sections, each block section having at the end thereof nearest the first passing siding a signal governing entrance into the block section of trains moving from the first to the second passing siding, the signals each being capable of displaying a plurality of indications, the signal for the block section adjacent the first passing siding being capable of providing a clear indication and at least one restrictive proceed indication, each block section having a pair of conductors governed by trafiic conditions in said section, means for supplying direct current to the conductors for each section, each section having a direct current relay energized over the conductors for such section and controlling the signal for such section, means effective when and only when the portion of the track stretch beside the second passing siding is vacant or is occupied by a train entering said track portion from said single track portion for supplying alternating current energy to the conductors for the block section adjacent the second passing siding, the conductors for each block section except the block section adjacent the first passing siding having associated therewith means effective on the supply of alternating current thereto to cause alternating current to be supplied to the conductors for the block section adjoining on the side nearest the first passing siding, and means responsive to the supply of alternating current to the conductors for the block section adjacent the first passing siding and governing the display of the clear indication by the signal for said block section.

6. In combination, a stretch of railroad track having a first and a second passing siding which are connected by a single track portion over which traffic moves in both directions, the rails of the single track portion being divided by insulated joints into three block sections including a first block section adjacent the first passing siding, a second block section adjacent the second passing siding, and an intermediate block section located between said first and second block sections, each block section having at the end thereof nearest the first passing siding a signal governing entrance into the block section of trains moving from the first to the second passing siding, the signals each being capable of displaying a clear, a caution and a stop indication, the signals for the intermediate 20 and second sections being governed by traffic conditions in the associated section, the signal for the first section being governed by traffic conditions in said first section and in the intermediate section in such manner that the signal 25 displays its stop indication when said first section is occupied, its caution indication when said first section is vacant and the intermediate section is occupied, and its clear indication when the first and intermediate sections are both vacant, and means responsive to occupancy of the portion of the track stretch beside the second passing siding for controlling the signal for said first section to permit the display of a clear indication by said signal only when the portion of the track stretch beside the second passing siding is vacant or is occupied by a train entering said track portion from the single track portion.

GEORGE R. PFLASTERER.

CERTIFICATE or CORRECTION.

Patent No. am ia March 1L 191m,

GEORGE R. PFLASTERER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 6, second celumn, lines 71 end 72, claim 11., for "nearest on the side adjacent" read -adjpining on the side nearest; and that the said Letters Patent should be read with this c orrectien therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25rd day of Ma ,-A. 1). 191m.

v I Leslie Frazer (Seal) Acting Commissioner of Patents.

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