US2559401A - Control of hump and trimmer signals for classification yards - Google Patents

Control of hump and trimmer signals for classification yards Download PDF

Info

Publication number
US2559401A
US2559401A US20177A US2017748A US2559401A US 2559401 A US2559401 A US 2559401A US 20177 A US20177 A US 20177A US 2017748 A US2017748 A US 2017748A US 2559401 A US2559401 A US 2559401A
Authority
US
United States
Prior art keywords
relay
signal
hump
control
indication
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US20177A
Inventor
Delbert F Cobourn
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Rail STS USA Inc
Original Assignee
Union Switch and Signal Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Union Switch and Signal Inc filed Critical Union Switch and Signal Inc
Priority to US20177A priority Critical patent/US2559401A/en
Application granted granted Critical
Publication of US2559401A publication Critical patent/US2559401A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B61RAILWAYS
    • B61LGUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L17/00Switching systems for classification yards
    • B61L17/02Details, e.g. indicating degree of track filling
    • B61L17/023Signalling; Signals with multiple indicating means

Definitions

  • My invention relates to control of hump and trimmer signals for railway classification yards, and particularly to means for insuring safe operation of such signals.
  • a signal which is known as a hump signal governs operation of a locomotive which moves cars from the receiving yard over the hump for distribution to the various tracks in the classification yard.
  • a second signal which is known as a trimmer signal, governs operation of a locomotive which rehandles cars that have gone onto the wrong tracks in the classification yard.
  • the trimmer signal is provided with a yellow indication for proceed and a red indication for stop
  • the hump signal is provided with a green proceed indication for high speed hump operations, a green over yellow indication for medium speed hump operations, a yellow proceed indication for low speed hump operations, a red indication for stop, and a flashing yellow indication for back-up movements.
  • the trimmer signal can be controlled to display its proceed indication only when the hump signal is controlled to indicate either stop or back-up.
  • the hump signal can be controlled to display any one of its forward proceed indications only when the trimmer signal is controlled to indicate stop.
  • One feature of my invention is the provision of means for preventing the hump signal from displaying a false steady yellow forward proceed indication when it should be displaying a fiashing yellow back-up indication, especially while the trimmer signal is displaying its yellow indication.
  • the accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention, in which a flasher relay is controlled by the hump signal control lever to be energized when this lever is placed in the position for controlling the hump signal to display its back-up indication, and in which a slow release repeater relay is controlled by the flasher relay, or by the hump signal control lever when this lever is placed in the position for controlling the hump signal to display either its yellow low speed proceed indication or its green over yellow medium speed proceed indication, and also in which the hump signal is controlled by 2 the flasher relay and by the slow release repeater relay to display its steady yellow low speed proceed indication or the flashing yellow back-up indication according as the flasher relay is deenergized or is energized while the slow release repeater relay is energized.
  • a receiving yard is shown, from which cars are moved over a bump track H from which they are in turn distributed to the various tracks of a classification yard.
  • a hump signal, designated by the reference character HS, and a trimmer signal, designated by the reference character TS, are located adjacent the summit of the hump.
  • Signal HS comprises a green or high speed proceed lamp G, a yellow lamp Y, which, upon being steadily lighted alone, provides a low speed proceed indication, and which, upon being periodically lighted, provides a back-up indication, and a red or stop lamp R. Lamps G and Y of signal HS, when lighted at the same time, provide a medium speed proceed indication.
  • Signal TS comprises a proceed lamp Y and a stop lamp R.
  • a manually operable lever, designated by the reference character TV, for controlling signal TS, has a normal or stop control position n and a proceed control position r.
  • a second manually operable lever, designated by the reference character HV, for controlling signal HS, has a backup control position f, a normal or stop control position 11, a low speed forward proceed position 0, a medium speed forward proceed position d, and a high speed forward proceed position 1'.
  • Contacts operated by each of these levers are shown as circles, in which are placed reference characters to show the positions of the respective levers in which the contacts are closed.
  • Contact l, for example, of lever HV is closed only while lever HV is in its J position as shown by the reference character I in the circle for contact I.
  • Contact 4 of lever HV is closed only while lever HV is in its 0 or its at position, or at any point between these two positions, as shown by the reference character cd in the circle for contact 4.
  • Levers HV and TV are mechanically interlocked with each other so that lever TV can be moved to its r position only when lever HV is in its 11. or its 1 position, and lever HV can be moved to any one of its proceed control positions 0, d, and r only when lever TV is in its n position.
  • Each of the signals HS and TS is there fore prevented from being controlled to display a proceed indication while the other signal is displaying a proceed indication.
  • a flasher relay F is controlled by a circuit which is closed only while lever HV is in its 1 position.
  • Relay F has a first contact 8 which is normally open, and which is periodically closed when relay F becomes energized;
  • a second contact 5 of relay F is normally closed and is periodically opened when relay F is energized.
  • a slow release repeater relay control circuit which includes contact 4 oflever HV, and has a second control circuit which includes contact 8 of relay F.
  • lamp R of signal HS passes from terminal BX of a suitable source of lighting current, through contact I of lever HV, and lamp R of signal HS to terminal NX of the same source of lighting current.
  • LampR of signal TS is lighted by a similar circuit which'includes contact 2 of lever TV.
  • relay F in some way becomes falsely 'deenergized, such as by a broken connection
  • relay HR would in turn become deenergized because contact 8 of relay F would remain opened. With relay HR deenergized, its contact 6 will open the circuit for lamp Y of signal HS, causing this lamp to be extinguished. If relay HR were not used and therefore contact .5 of relay. HR were omitted from the circuit for lamp Y of signal HS, then lamp Y of signal HS would be steadily lighted while relay F is deenergized, and therefore signal HS would be displaying a steady yellow proceed indication while signal TS is also displaying the yellow proceed indication.
  • relay HR on account of being controlled by relay F, prevents lamp Y of signal HS from displaying the low speed proceed indication while signal TS is displaying its proceed indication in the event that relay F should become falsely deenergized when it should be energized for controlling signal HS to display the flashing yellow back-up indication.
  • the trimmer signal is manually controllable for displaying a proceed indication only while the'hump signal is manually controlled for displaying a stop or a flashing back-up indication
  • the combination comprising, a flasher relay having a first contact which is open while said flasher relay is deenergized but which is periodically closed while said flasher relay is energized and having a second contact which is constantly closed while said flasher relay is deenergized but which is periodically opened while said flasher relay is energized, a slow release relay, a manually operable control device having a first and a second and also a third control position, ,means controlled by said control device in said first control position for energizing said flasher relay, means controlled by said control device in said second and third control positions for energizing said slow release relay, other means controlled by said first contact for periodically energizing said. slow release relay, means controlled by said control device in said third control position for controlling said
  • a manually operable device for controlling the trimmer signal is mechanically interlocked with a second manually operable device for controlling the hump signal so that the first manually operable device can be moved to a reverse control position for controlling the trimmer signal to display a proceed indication only if the second manually operable device occupies a stop control position or a back-up control position
  • the combination comprising, a flasher relay, a slow release relay, means controlled by said second manually operable device in said back-up control position for energizing said flasher relay means controlled by said second manually operable device in a third or a fourth control position for energizing said slow release relay, other means controlled by said flasher relay for periodically energizing said slow release relay While said flasher relay is energized, means controlled by said second manually operable device in said fourth control position for controlling said hump signal to display a green light, and means controlled by said flasher relay and by said slow release relay for controlling said
  • the trimmer signal is manually controllable for displaying a proceed indication only while the hump signal is manually controlled for displaying a stop or a flashing backup indication
  • the combination comprising, a flasher relay having a first contact which is open while said flasher relay is deenergized but which is periodically closed while said flasher relay is energized and having a second contact which is constantly closed while said flasher relay is deenergized but which is periodically opened while said flasher relay is energized, a slow release relay, a manually operable control device having a back-up control position and three forward proceed control positions as well as a stop control position, a circuit controlled by said control device in said back-up control position for energizing said flasher relay, a circuit controlled by said control device in either a first or a second one of said forward proceed control positions for energizing said slow release relay,
  • a second circuit for energizing said slow release relay controlled by said first contact of said flasher relay a circuit controlled by said control device in its said stop control position for controlling said hump signal to display a stop indication, a circuit controlled by said control device in either its second or its third forward proceed control position for controlling said hump signal to display a green light, and a circuit controlled by said second contact of said flasher relay and by a front contact of said slow release relay for controlling said hump signal to display either a flashing yellow light for back-up indication or a steady yellow light for a forward proceed indication according as said flasher relay is energized or is deenergized while said slow release relay is energized.
  • a color light signal comprising a green and a yellow and a red element
  • a manually operable control device having a normal control position and four reverse control positions
  • a flasher relay having a first contact which is open while said flasher relay is deenergized but which is periodically closed while said flasher relay is energized and having a second contact which is constantly closed while said flasher relay is deenergized but which is periodically opened while said flasher relay is energized
  • a slow release relay means controlled by said control device in the first of said reverse control positions for energizing said flasher relay, means controlled by said control device in either a second or a third reverse control position for energizing said slow release relay, other means controlled by said first contact of said flasher relay for at times energizing said slow release relay, means controlled by said control device in said normal control position for lighting said red element, means controlled by said control device in either its third or its fourth reverse control position for lighting said green element, and means controlled by said second contact of said flasher relay and by a front contact

Description

D. F. COBOURN July 3, 1951 CONTROL OF HUMP A'ND TRIMMER SIGNALS FOR CLASSIFICATION YARDS Filed April 10, 1948 Classification Yard Receiving Yard Nebanieal Interloek i 7 433K 1 1B 11 INVENTOR. ('obauzm HIS ATTORNEY Patented July 3, 1951 CONTROL OF HUMP AND TRIMMER SIGNALS FOR CLASSIFICATION YARDS Delbert F. Cobourn, Portsmouth, Ohio, assignor to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application April 10, 1948, Serial No. 20,177
4 Claims.
My invention relates to control of hump and trimmer signals for railway classification yards, and particularly to means for insuring safe operation of such signals.
At a hump classification yard, a signal which is known as a hump signal governs operation of a locomotive which moves cars from the receiving yard over the hump for distribution to the various tracks in the classification yard. A second signal, which is known as a trimmer signal, governs operation of a locomotive which rehandles cars that have gone onto the wrong tracks in the classification yard.
In one arrangement of hump and trimmer signals of the color light type, the trimmer signal is provided with a yellow indication for proceed and a red indication for stop, whereas the hump signal is provided with a green proceed indication for high speed hump operations, a green over yellow indication for medium speed hump operations, a yellow proceed indication for low speed hump operations, a red indication for stop, and a flashing yellow indication for back-up movements.
The trimmer signal can be controlled to display its proceed indication only when the hump signal is controlled to indicate either stop or back-up. Similarly, the hump signal can be controlled to display any one of its forward proceed indications only when the trimmer signal is controlled to indicate stop.
One feature of my invention is the provision of means for preventing the hump signal from displaying a false steady yellow forward proceed indication when it should be displaying a fiashing yellow back-up indication, especially while the trimmer signal is displaying its yellow indication.
I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.
The accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention, in which a flasher relay is controlled by the hump signal control lever to be energized when this lever is placed in the position for controlling the hump signal to display its back-up indication, and in which a slow release repeater relay is controlled by the flasher relay, or by the hump signal control lever when this lever is placed in the position for controlling the hump signal to display either its yellow low speed proceed indication or its green over yellow medium speed proceed indication, and also in which the hump signal is controlled by 2 the flasher relay and by the slow release repeater relay to display its steady yellow low speed proceed indication or the flashing yellow back-up indication according as the flasher relay is deenergized or is energized while the slow release repeater relay is energized.
Similar reference characters refer to similar parts in the drawing.
Referring to the drawing, a receiving yard is shown, from which cars are moved over a bump track H from which they are in turn distributed to the various tracks of a classification yard.
A hump signal, designated by the reference character HS, and a trimmer signal, designated by the reference character TS, are located adjacent the summit of the hump. Signal HS comprises a green or high speed proceed lamp G, a yellow lamp Y, which, upon being steadily lighted alone, provides a low speed proceed indication, and which, upon being periodically lighted, provides a back-up indication, and a red or stop lamp R. Lamps G and Y of signal HS, when lighted at the same time, provide a medium speed proceed indication. Signal TS comprises a proceed lamp Y and a stop lamp R.
A manually operable lever, designated by the reference character TV, for controlling signal TS, has a normal or stop control position n and a proceed control position r. A second manually operable lever, designated by the reference character HV, for controlling signal HS, has a backup control position f, a normal or stop control position 11, a low speed forward proceed position 0, a medium speed forward proceed position d, and a high speed forward proceed position 1'. Contacts operated by each of these levers are shown as circles, in which are placed reference characters to show the positions of the respective levers in which the contacts are closed. Contact l, for example, of lever HV is closed only while lever HV is in its J position as shown by the reference character I in the circle for contact I. Contact 4 of lever HV is closed only while lever HV is in its 0 or its at position, or at any point between these two positions, as shown by the reference character cd in the circle for contact 4.
Levers HV and TV are mechanically interlocked with each other so that lever TV can be moved to its r position only when lever HV is in its 11. or its 1 position, and lever HV can be moved to any one of its proceed control positions 0, d, and r only when lever TV is in its n position. Each of the signals HS and TS is there fore prevented from being controlled to display a proceed indication while the other signal is displaying a proceed indication.
A flasher relay F is controlled by a circuit which is closed only while lever HV is in its 1 position. Relay F has a first contact 8 which is normally open, and which is periodically closed when relay F becomes energized; A second contact 5 of relay F is normally closed and is periodically opened when relay F is energized.
A slow release repeater relay control circuit which includes contact 4 oflever HV, and has a second control circuit which includes contact 8 of relay F.
Having described, in general, the arrangement and control of the various parts of apparatus embodying my invention, I shall now describe the circuits and operation in detail.
As shown in the drawing, all parts of the apparatus are in the normal condition, that is, each of the control levers HV and TV is in its normal -or stop position 11; therefore relays F and HR are deenergized; and each of the signals HS and TS is displaying a red or stop indication.
The circuit by which lamp R of signal HS is lighted passes from terminal BX of a suitable source of lighting current, through contact I of lever HV, and lamp R of signal HS to terminal NX of the same source of lighting current. LampR of signal TS is lighted by a similar circuit which'includes contact 2 of lever TV.
, I shall assume that the hump master decides to control signal HS to display the high speed proceed indication. He will, therefore, move lever HV to its 1 position, thereby completing a circuit passing from terminal BX, through contact 3 of lever HV, and lamp G of signal HS to terminal NX.
When the hump master desires to control signal HS to display the medium speed proceed indication, he will move lever HV to its d position. Lamp G of signal HS will then remain lighted as before. Now, however, relay HR is energized by a circuit passing-from terminal B of a suitable source of current, through contact of lever HV,
and the winding of relay HR to terminal N of r the same source of current. With relay HR energized, lamp Y of signal HS will now be steadily lighted, in addition to lamp G of signal HS, by
a circuit passing from terminal BX, through contact'5 of relay F, contact 6 of relay HR, and lamp Y of signal HS to terminal NX.
If the hump master later desires signal HS to display the low speed proceed indication, he will move lever HV to its position, thereby opening contact 3 of lever HV and extinguishing lamp G. Relay HR will remain energized by its circuit previously traced, and therefore lamp Y of signal HS will remain lighted by the circuit previously traced for this lamp.
When the hump master decides to control signal HS to display the back-up indication, he will move lever HV to its ,1 position, thereby completing a circuit for energizing relay F, passing from terminal B, through contact 1 of lever HV, and the winding of relay F to terminal N. With relay F energized, its contact 8 will. be periodically closed, thereby completing a circuit for energizing relay HR, passing from terminal B, through contact 3 of relay F, and the winding of relay HR to terminal N, Since relay HR is of the slow releasing type, its contact Williemain closed during the open periods of contact 8 of relay F. With relay F energized, its contact 5 periodically opens the circuit previously traced for lamp Y of signal HS, causing signal HR has a first 4 HS to display a flashing yellow back-up indication.
I shall assume that the hump master now decides to control signal TS to display the yellow proceed indication while signal HS is displaying the back-up indication; He will, therefore, move lever TV to its r position, completing a circuit for'lamp Y of signal TS, passing from terminal BX, through contact 9 of lever TV, and lamp Y of signal TS to terminal NX. Signal TS will, therefore, display a steady yellow indication while signal HS is displaying a flashing yellow backup indication.
If, now, relay F in some way becomes falsely 'deenergized, such as by a broken connection,
while lever HV is in its 3 position, relay HR would in turn become deenergized because contact 8 of relay F would remain opened. With relay HR deenergized, its contact 6 will open the circuit for lamp Y of signal HS, causing this lamp to be extinguished. If relay HR were not used and therefore contact .5 of relay. HR were omitted from the circuit for lamp Y of signal HS, then lamp Y of signal HS would be steadily lighted while relay F is deenergized, and therefore signal HS would be displaying a steady yellow proceed indication while signal TS is also displaying the yellow proceed indication. It follows that relay HR, on account of being controlled by relay F, prevents lamp Y of signal HS from displaying the low speed proceed indication while signal TS is displaying its proceed indication in the event that relay F should become falsely deenergized when it should be energized for controlling signal HS to display the flashing yellow back-up indication.
Although I have herein shown and described only one form of 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. 7
Having thus described my invention, what I claim is: l
1. In an arrangement of hump and trimmer signals of the color light type for a classification yard, in which the trimmer signal is manually controllable for displaying a proceed indication only while the'hump signal is manually controlled for displaying a stop or a flashing back-up indication, the combination comprising, a flasher relay having a first contact which is open while said flasher relay is deenergized but which is periodically closed while said flasher relay is energized and having a second contact which is constantly closed while said flasher relay is deenergized but which is periodically opened while said flasher relay is energized, a slow release relay, a manually operable control device having a first and a second and also a third control position, ,means controlled by said control device in said first control position for energizing said flasher relay, means controlled by said control device in said second and third control positions for energizing said slow release relay, other means controlled by said first contact for periodically energizing said. slow release relay, means controlled by said control device in said third control position for controlling said hump signalrto disrelay is energized or is deenergized while said slow release relay is energized.
2. In a control system for hump and trimmer signals for a classification yard, in which a manually operable device for controlling the trimmer signal is mechanically interlocked with a second manually operable device for controlling the hump signal so that the first manually operable device can be moved to a reverse control position for controlling the trimmer signal to display a proceed indication only if the second manually operable device occupies a stop control position or a back-up control position, the combination comprising, a flasher relay, a slow release relay, means controlled by said second manually operable device in said back-up control position for energizing said flasher relay means controlled by said second manually operable device in a third or a fourth control position for energizing said slow release relay, other means controlled by said flasher relay for periodically energizing said slow release relay While said flasher relay is energized, means controlled by said second manually operable device in said fourth control position for controlling said hump signal to display a green light, and means controlled by said flasher relay and by said slow release relay for controlling said hump signal to display a steady yellow light or a flashing back-up light according as said slow release relay is energized while said flasher relay is deenergized or while said flasher relay is energized.
3. In an arrangement of hump and trimmer signals of the color light type for a classification yard, in which the trimmer signal is manually controllable for displaying a proceed indication only while the hump signal is manually controlled for displaying a stop or a flashing backup indication, the combination comprising, a flasher relay having a first contact which is open while said flasher relay is deenergized but which is periodically closed while said flasher relay is energized and having a second contact which is constantly closed while said flasher relay is deenergized but which is periodically opened while said flasher relay is energized, a slow release relay, a manually operable control device having a back-up control position and three forward proceed control positions as well as a stop control position, a circuit controlled by said control device in said back-up control position for energizing said flasher relay, a circuit controlled by said control device in either a first or a second one of said forward proceed control positions for energizing said slow release relay,
a second circuit for energizing said slow release relay controlled by said first contact of said flasher relay, a circuit controlled by said control device in its said stop control position for controlling said hump signal to display a stop indication, a circuit controlled by said control device in either its second or its third forward proceed control position for controlling said hump signal to display a green light, and a circuit controlled by said second contact of said flasher relay and by a front contact of said slow release relay for controlling said hump signal to display either a flashing yellow light for back-up indication or a steady yellow light for a forward proceed indication according as said flasher relay is energized or is deenergized while said slow release relay is energized.
4, In combination, a color light signal comprising a green and a yellow and a red element, a manually operable control device having a normal control position and four reverse control positions, a flasher relay having a first contact which is open while said flasher relay is deenergized but which is periodically closed while said flasher relay is energized and having a second contact which is constantly closed while said flasher relay is deenergized but which is periodically opened while said flasher relay is energized, a slow release relay, means controlled by said control device in the first of said reverse control positions for energizing said flasher relay, means controlled by said control device in either a second or a third reverse control position for energizing said slow release relay, other means controlled by said first contact of said flasher relay for at times energizing said slow release relay, means controlled by said control device in said normal control position for lighting said red element, means controlled by said control device in either its third or its fourth reverse control position for lighting said green element, and means controlled by said second contact of said flasher relay and by a front contact of said slow releasing relay for steadily or periodically lighting said yellow element according as said flasher relay is deenergized or is energized.
DELBERT F. COBOURN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,298,815 Young Oct. 13, 1942 2,368,785 Shaw Feb. 6, 1945
US20177A 1948-04-10 1948-04-10 Control of hump and trimmer signals for classification yards Expired - Lifetime US2559401A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US20177A US2559401A (en) 1948-04-10 1948-04-10 Control of hump and trimmer signals for classification yards

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US20177A US2559401A (en) 1948-04-10 1948-04-10 Control of hump and trimmer signals for classification yards

Publications (1)

Publication Number Publication Date
US2559401A true US2559401A (en) 1951-07-03

Family

ID=21797150

Family Applications (1)

Application Number Title Priority Date Filing Date
US20177A Expired - Lifetime US2559401A (en) 1948-04-10 1948-04-10 Control of hump and trimmer signals for classification yards

Country Status (1)

Country Link
US (1) US2559401A (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2298815A (en) * 1941-10-20 1942-10-13 Union Switch & Signal Co Railway signaling apparatus
US2368785A (en) * 1943-04-16 1945-02-06 Union Switch & Signal Co Railway traffic controlling apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2298815A (en) * 1941-10-20 1942-10-13 Union Switch & Signal Co Railway signaling apparatus
US2368785A (en) * 1943-04-16 1945-02-06 Union Switch & Signal Co Railway traffic controlling apparatus

Similar Documents

Publication Publication Date Title
US2638536A (en) Four-indication signal control system embodying polar biased code following and polarized line relays
US2559401A (en) Control of hump and trimmer signals for classification yards
US2082933A (en) Apparatus for controlling railway switches
US2607001A (en) Code detecting means
US2768287A (en) Railway track switch controlling apparatus
US2150579A (en) Railway signaling system
US2425109A (en) Railway switch and signal control and interlocking apparatus
US2298815A (en) Railway signaling apparatus
US2993117A (en) Dragging equipment detector system
US2300757A (en) Railway signal control and indication apparatus
US2017452A (en) Railway signaling system
US2368785A (en) Railway traffic controlling apparatus
US2414079A (en) Railroad track switch position indicator system and car actuated circuit controllertherefor
US2100432A (en) Railway signaling system
US1797218A (en) Railway-traffic-controlling apparatus
US2618741A (en) Time element relay control means
US2891142A (en) Railway interlocking control system
US2117128A (en) Railway traffic controlling apparatus
US1880032A (en) Railway signaling
GB528326A (en) Improvements relating to railway traffic controlling apparatus
USRE20248E (en) Kailway signaling system
US1709888A (en) Railway signaling
US2588836A (en) Arrangement for controlling special indications of distant signals
US2298806A (en) Railway traffic controlling apparatus
US2174253A (en) Apparatus for the control of highway crossing signals