Signal and Train ControlRULES, STANDARDS, AND INSTRUCTIONS (R,S&I)

STC – 7

Definitions

Subpart G

This presentation is provided for reference only.

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Learning Objectives
        - Understand that these regulations are engineering design standards and must be incorporated into the design of any on-board signal system.
        - Understand that actions taken during the installation, maintenance, or modification of the system must not negate these design standards.	

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CAUTION

The following presentation was developed to provide general information only. For detailed compliance information please refer to 49 CFR 236 – Rules, Standards and Instructions, Subpart G.  It is recommended that each employee refer to appropriate manuals and regulations when dealing with any specific issue.

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When in doubt, go to the book!

Information

The FRA Rules, Standards, and Instructions are considered to be the minimum standard allowed for the installation, inspection, maintenance, and repair of signal and train control systems, devices, and appliances.  Each railroad may adopt more stringent standards. Refer to your railroad’s signal standard and instruction manual for further guidance.

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§ 236.700 Definitions.

For the purpose of these rules, standards, and instructions, the following definitions will apply. 

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§ 236.701 Application, brake; full service.

An application of the brakes resulting from a continuous or a split reduction in brake pipe pressure at a service rate until maximum brake cylinder pressure is developed. As applied to an automatic or electro-pneumatic brake with speed governor control, an application other than emergency which develops the maximum brake cylinder pressure, as determined by the design of the brake equipment for the speed at which the train is operating. 

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§ 236.702 Arm, semaphore.

The part of a semaphore signal displaying an aspect. It consists of a blade fastened to a spectacle. 

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§ 236.703 Aspect.

The appearance of a roadway signal conveying an indication as viewed from the direction of an approaching train; the appearance of a cab signal conveying an indication as viewed by an observer in the cab. 

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§ 236.705 Bar, locking.

A bar in an interlocking machine to which the locking dogs are attached. 

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§ 236.706 Bed, locking.

That part of an interlocking machine that contains or holds the tappets, locking bars, crosslocking, dogs and other apparatus used to interlock the levers. 

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§ 236.707 Blade, semaphore.

The extended part of a semaphore arm which shows the position of the arm. 

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§ 236.708 Block.

A length of track of defined limits, the use of which by trains is governed by block signals, cab signals, or both. 

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§ 236.709 Block, absolute.

A block in which no train is permitted to enter while it is occupied by another train. 

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§ 236.710 Block, latch.

The lower extremity of a latch rod which engages with a square shoulder of the segment or quadrant to hold the lever in position. 

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§ 236.711 Bond, rail joint.

A metallic connection attached to adjoining rails to insure electrical conductivity. 

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§ 236.712 Brake pipe.

A pipe running from the engineman's brake valve through the train, used for the transmission of air under pressure to charge and actuate the automatic brake equipment and charge the reservoirs of the electro-pneumatic brake equipment on each vehicle of the train. 

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§ 236.713 Bridge, movable.

That section of a structure bridging a navigable waterway so designed that it may be displaced to permit passage of traffic on the waterway. 

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§ 236.714 Cab.

The compartment of a locomotive from which the propelling power and power brakes of the train are manually controlled. 

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§ 236.717 Characteristics, operating.

The measure of electrical values at which electrical or electronic apparatus operate (e.g., drop-away, pick-up, maximum and minimum current, and working value). 

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§ 236.718 Chart, dog.

A diagrammatic representation of the mechanical locking of an interlocking machine, used as a working plan in making up, assembling and fitting the locking. 

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§ 236.719 Circuit, acknowledgment.

A circuit consisting of wire or other conducting material installed between the track rails at each signal in territory where an automatic train stop system or cab signal system of the continuous inductive type with 2-indication cab signals is in service, to enforce acknowledgement by the engineman at each signal displaying an aspect requiring a stop. 

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§ 236.720 Circuit, common return.

A term applied where one wire is used for the return of more than one electric circuit. 

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§ 236.721 Circuit, control.

An electrical circuit between a source of electric energy and a device which it operates. 

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§ 236.722 Circuit, cut-in.

A roadway circuit at the entrance to automatic train stop, train control or cab signal territory by means of which locomotive equipment of the continuous inductive type is actuated so as to be in operative condition. 

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§ 236.723 Circuit, double wire; line.

An electric circuit not employing a common return wire; a circuit formed by individual wires throughout. 

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§ 236.724 Circuit, shunt fouling.

The track circuit in the fouling section of a turnout, connected in multiple with the track circuit in the main track. 

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§ 236.725 Circuit, switch shunting.

A shunting circuit which is closed through contacts of a switch circuit controller. 

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§ 236.726 Circuit, track.

An electrical circuit of which the rails of the track form a part. 

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§ 236.727 Circuit, track; coded.

A track circuit in which the energy is varied or interrupted periodically. 

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§ 236.728 Circuit, trap.

A term applied to a circuit used where it is desirable to provide a track circuit but where it is impracticable to maintain a track circuit. 

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§ 236.729 Cock, double heading.

A manually operated valve by means of which the control of brake operation is transferred to the leading locomotive. 

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§ 236.730 Coil, receiver.

Concentric layers of insulated wire wound around the core of a receiver of an automatic train stop, train control or cab signal device on a locomotive. 

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§ 236.731 Controller, circuit.

A device for opening and closing electric circuits. 

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§ 236.732 Controller, circuit; switch.

A device for opening and closing electric circuits, operated by a rod connected to a switch, derail or movable-point frog. 

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§ 236.733 Current, foreign.

A term applied to stray electric currents which may affect a signaling system, but which are not a part of the system. 

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§ 236.734 Current of traffic.

The movement of trains on a specified track in a designated direction. 

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§ 236.735 Current, leakage.

A stray electric current of relatively small value which flows through or across the surface of insulation when a voltage is impressed across the insulation. 

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§ 236.736 Cut-section.

A location other than a signal location where two adjoining track circuits end within a block. 

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§ 236.737 Cut-section, relayed.

A cut-section where the energy for one track circuit is supplied through front contacts or through front and polar contacts of the track relay for the adjoining track circuit. 

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§ 236.738 Detector, point.

A circuit controller which is part of the switch operating mechanism and operated by a rod connected to a switch, derail or movable point frog to indicate that the point is within a specified distance of the stock rail. 

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§ 236.739 Device, acknowledging.

A manually operated electric switch or pneumatic valve by means of which, on a locomotive equipped with an automatic train stop or train control device, an automatic brake application can be forestalled, or by means of which, on a locomotive equipped with an automatic cab signal device, the sounding of the cab indicator can be silenced. 

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§ 236.740 Device, reset.

A device whereby the brakes may be released after an automatic train control brake application. 

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§ 236.741 Distance, stopping.

The maximum distance on any portion of any railroad which any train operating on such portion of railroad at its maximum authorized speed, will travel during a full service application of the brakes, between the point where such application is initiated and the point where the train comes to a stop. 

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§ 236.742 Dog, locking.

A steel block attached to a locking bar or tappet of an interlocking machine, by means of which locking between levers is accomplished. 

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§ 236.743 Dog, swing.

A locking dog mounted in such a manner that it is free to rotate on a trunnion which is riveted to a locking bar. 

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§ 236.744 Element, roadway.

That portion of the roadway apparatus of automatic train stop, train control, or cab signal system, such as electric circuit, inductor, or trip arm to which the locomotive apparatus of such system is directly responsive. 

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§ 236.745 Face, locking.

The locking surface of a locking dog, tappet or cross locking of an interlocking machine. 

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§ 236.746 Feature, restoring.

An arrangement on an electro-pneumatic switch by means of which power is applied to restore the switch movement to full normal or to full reverse position, before the driving bar creeps sufficiently to unlock the switch, with control level in normal or reverse position. 

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§ 236.747 Forestall.

As applied to an automatic train stop or train control device, to prevent an automatic brake application by operation of an acknowledging device or by manual control of the speed of the train. 

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§ 236.749 Indication.

The information conveyed by the aspect of a signal. 

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§ 236.750 Interlocking, automatic.

An arrangement of signals, with or without other signal appliances, which functions through the exercise of inherent powers as distinguished from those whose functions are controlled manually, and which are so interconnected by means of electric circuits that their movements must succeed each other in proper sequence, train movements over all routes being governed by signal indication. 

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§ 236.751 Interlocking, manual.

An arrangement of signals and signal appliances operated from an interlocking machine and so interconnected by means of mechanical and/or electric locking that their movements must succeed each other in proper sequence, train movements over all routes being governed by signal indication. 

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§ 236.752 Joint, rail, insulated.

A joint in which electrical insulation is provided between adjoining rails. 

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§ 236.753 Limits, interlocking.

The tracks between the opposing home signals of an interlocking. 

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§ 236.754 Line, open wire.

An overhead wire line consisting of single conductors as opposed to multiple-conductor cables. 

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§ 236.755 Link, rocker.

That portion of an interlocking machine which transmits motion between the latch and the universal link. 

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§ 236.756 Lock, bolt.

A mechanical lock so arranged that if a switch, derail or movable-point frog is not in the proper position for a train movement, the signal governing that movement cannot display an aspect to proceed; and that will prevent a movement of the switch, derail or movable-point frog unless the signal displays its most restrictive aspect. 

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§ 236.757 Lock, electric.

A device to prevent or restrict the movement of a lever, a switch or a movable bridge, unless the locking member is withdrawn by an electrical device, such as an electromagnet, solenoid or motor. 

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§ 236.758 Lock, electric, forced drop.

An electric lock in which the locking member is mechanically forced down to the locked position. 

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§ 236.759 Lock, facing point.

A mechanical lock for a switch, derail, or movable-point frog, comprising a plunger stand and a plunger which engages a lock rod attached to the switch point to lock the operated unit. 

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§ 236.760 Locking, approach.

Electric locking effective while a train is approaching, within a specified distance, a signal displaying an aspect to proceed, and which prevents, until after the expiration of a predetermined time interval after such signal has been caused to display its most restrictive aspect, the movement of any interlocked or electrically locked switch, movable-point frog, or derail in the route governed by the signal, and which prevents an aspect to proceed from being displayed for any conflicting route. 

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§ 236.761 Locking, electric.

The combination of one or more electric locks and controlling circuits by means of which levers of an interlocking machine, or switches or other units operated in connection with signaling and interlocking, are secured against operation under certain conditions. 

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§ 236.762 Locking, indication.

Electric locking which prevents manipulation of levers that would result in an unsafe condition for a train movement if a signal, switch, or other operative unit fails to make a movement corresponding to that of its controlling lever, or which directly prevents the operation of a signal, switch, or other operative unit, in case another unit which should operate first fails to make the required movement. 

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§ 236.763 Locking, latch operated.

The mechanical locking of an interlocking machine which is actuated by means of the lever latch. 

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§ 236.764 Locking, lever operated.

The mechanical locking of an interlocking machine which is actuated by means of the lever. 

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§ 236.765 Locking, mechanical.

An arrangement of locking bars, dogs, tappets, cross locking and other apparatus by means of which interlocking is effected between the levers of an interlocking machine and so interconnected that their movements must succeed each other in a predetermined order. 

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§ 236.766 Locking, movable bridge.

The rail locks, bridge locks, bolt locks, circuit controllers, and electric locks used in providing interlocking protection at a movable bridge. 

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§ 236.767 Locking, route.

Electric locking, effective when a train passes a signal displaying an aspect for it to proceed, which prevents the movement of any switch, movable-point frog, or derail in advance of the train within the route entered. It may be so arranged that as a train clears a track section of the route, the locking affecting that section is released. 

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§ 236.768 Locking, time.

A method of locking, either mechanical or electrical, which, after a signal has been caused to display an aspect to proceed, prevents, until after the expiration of a predetermined time interval after such signal has been caused to display its most restrictive aspect, the operation of any interlocked or electrically locked switch, movable-point frog, or derail in the route governed by that signal, and which prevents an aspect to proceed from being displayed for any conflicting route. 

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§ 236.769 Locking, traffic.

Electric locking which prevents the manipulation of levers or other devices for changing the direction of traffic on a section of track while that section is occupied or while a signal displays an aspect for a movement to proceed into that section. 

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§ 236.770 Locomotive.

A self-propelled unit of equipment which can be used in train service. 

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§ 236.771 Machine, control.

An assemblage of manually operated devices for controlling the functions of a traffic control system; it may include a track diagram with indication lights. 

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§ 236.772 Machine, interlocking.

An assemblage of manually operated levers or other devices for the control of signals, switches or other units. 

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§ 236.773 Movements, conflicting.

Movements over conflicting routes. 

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§ 236.774 Movement, facing.

The movement of a train over the points of a switch which face in a direction opposite to that in which the train is moving. 

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§ 236.775 Movement, switch-and-lock.

A device, the complete operation of which performs the three functions of unlocking, operating and locking a switch, movable-point frog or derail. 

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§ 236.776 Movement, trailing.

The movement of a train over the points of a switch which face in the direction in which the train is moving. 

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§ 236.777 Operator, control.

An employee assigned to operate the control machine of a traffic control system. 

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§ 236.778 Piece, driving.

A crank secured to a locking shaft by means of which horizontal movement is imparted to a longitudinal locking bar. 

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§ 236.779 Plate, top.

A metal plate secured to a locking bracket to prevent the cross locking from being forced out of the bracket. 

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§ 236.780 Plunger, facing point lock.

That part of a facing point lock which secures the lock rod to the plunger stand when the switch is locked. 

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§ 236.782 Point, controlled.

A location where signals and/or other functions of a traffic control system are controlled from the control machine. 

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§ 236.783 Point, stop-indication.

As applied to an automatic train stop or train control system without the use of roadway signals, a point where a signal displaying an aspect requiring a stop would be located. 

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§ 236.784 Position, deenergized.

The position assumed by the moving member of an electromagnetic device when the device is deprived of its operating current. 

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§ 236.785 Position, false restrictive.

A position of a semaphore arm that is more restrictive than it should be. 

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§ 236.786 Principle, closed circuit.

The principle of circuit design where a normally energized electric circuit which, on being interrupted or deenergized, will cause the controlled function to assume its most restrictive condition. 

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§ 236.787 Protection, cross.

An arrangement to prevent the improper operation of a signal, switch, movable-point frog, or derail as the result of a cross in electrical circuits. 

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§ 236.787a Railroad.

Railroad means any form of non-highway ground transportation that runs on rails or electromagnetic guideways and any entity providing such transportation, including - 

(a) Commuter or other short-haul railroad passenger service in a metropolitan or suburban area and commuter railroad service that was operated by the Consolidated Rail Corporation on January 1, 1979; and 

(b) High speed ground transportation systems that connect metropolitan areas, without regard to whether those systems use new technologies not associated with traditional railroads; but does not include rapid transit operations in an urban area that are not connected to the general railroad system of transportation. 

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§ 236.788 Receiver.

A device on a locomotive, so placed that it is in position to be influenced inductively or actuated by an automatic train stop, train control or cab signal roadway element. 

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§ 236.789 Relay, timing.

A relay which will not close its front contacts or open its back contacts, or both, until the expiration of a definite time intervals after the relay has been energized. 

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§ 236.790 Release, time.

A device used to prevent the operation of an operative unit until after the expiration of a predetermined time interval after the device has been actuated. 

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§ 236.791 Release, value.

The electrical value at which the movable member of an electromagnetic device will move to its deenergized portion. 

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§ 236.792 Reservoir, equalizing.

An air reservoir connected with and adding volume to the top portion of the equalizing piston chamber of the automatic brake valve, to provide uniform service reductions in brake pipe pressure regardless of the length of the train. 

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§ 236.793 Rod, lock.

A rod, attached to the front rod or lug of a switch, movable-point frog or derail, through which a locking plunger may extend when the switch points or derail are in the normal or reverse position. 

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§ 236.794 Rod, up-and-down.

A rod used for connecting the semaphore arm to the operating mechanism of a signal. 

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§ 236.795 Route.

The course or way which is, or is to be, traveled. 

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§ 236.796 Routes, conflicting.

Two or more routes, opposing, converging or intersecting, over which movements cannot be made simultaneously without possibility of collision. 

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§ 236.797 Route, interlocked.

A route within interlocking limits. 

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§ 236.798 Section, dead.

A section of track, either within a track circuit or between two track circuits, the rails of which are not part of a track circuit. 

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§ 236.799 Section, fouling.

The section of track between the switch points and the clearance point in a turnout. 

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§ 236.800 Sheet, locking.

A description in tabular form of the locking operations in an interlocking machine. 

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§ 236.801 Shoe, latch.

The casting by means of which the latch rod and the latch block are held to a lever of a mechanical interlocking machine. 

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§ 236.802 Shunt.

A by-path in an electrical circuit. 

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§ 236.802a Siding.

An auxiliary track for meeting or passing trains. 

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§ 236.803 Signal, approach.

A roadway signal used to govern the approach to another signal and if operative so controlled that its indication furnishes advance information of the indication of the next signal. 

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§ 236.804 Signal, block.

A roadway signal operated either automatically or manually at the entrance to a block. 

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§ 236.805 Signal, cab.

A signal located in engineman's compartment or cab, indicating a condition affecting the movement of a train and used in conjunction with interlocking signals and in conjunction with or in lieu of block signals. 

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§ 236.806 Signal, home.

A roadway signal at the entrance to a route or block to govern trains in entering and using that route or block. 

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§ 236.807 Signal, interlocking.

A roadway signal which governs movements into or within interlocking limits. 

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§ 236.808 Signals, opposing.

Roadway signals which govern movements in opposite directions on the same track. 

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§ 236.809 Signal, slotted mechanical.

A mechanically operated signal with an electromagnetic device inserted in its operating connection to provide a means of controlling the signal electrically, as well as mechanically. 

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§ 236.810 Spectacle, semaphore arm.

That part of a semaphore arm which holds the roundels and to which the blade is fastened. 

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§ 236.811 Speed, medium.

A speed not exceeding 40 miles per hour. 

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§ 236.812 Speed, restricted.

A speed that will permit stopping within one-half the range of vision, but not exceeding 20 miles per hour. 

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§ 236.813 Speed, slow.

A speed not exceeding 20 miles per hour. 

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§ 236.813a State, most restrictive.

The mode of an electric or electronic device that is equivalent to a track relay in its de-energized position. 

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§ 236.814 Station, control.

The place where the control machine of a traffic control system is located. 

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§ 236.815 Stop.

As applied to mechanical locking, a device secured to a locking bar to limit its movement. 

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§ 236.816 Superiority of trains.

The precedence conferred upon one train over other trains by train order or by reason of its class or the direction of its movement. 

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§ 236.817 Switch, electro-pneumatic.

A switch operated by an electro-pneumatic switch-and-lock movement. 

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§ 236.818 Switch, facing point.

A switch, the points of which face traffic approaching in the direction for which the track is signaled. 

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§ 236.819 Switch, hand operated.

A non-interlocked switch which can only be operated manually. 

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§ 236.820 Switch, interlocked.

A switch within the interlocking limits the control of which is interlocked with other functions of the interlocking. 

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§ 236.820a Switch, power-operated.

A switch operated by an electrically, hydraulically, or pneumatically driven switch-and-lock movement. 

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§ 236.821 Switch, sectionalizing.

A switch for disconnecting a section of a power line from the source of energy. 

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§ 236.822 Switch, spring.

A switch equipped with a spring device which forces the points to their original position after being trailed through and holds them under spring compression. 

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§ 236.823 Switch, trailing point.

A switch, the points of which face away from traffic approaching in the direction for which the track is signaled. 

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§ 236.824 System, automatic block signal.

A block signal system wherein the use of each block is governed by an automatic block signal, cab signal, or both. 

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§ 236.825 System, automatic train control.

A system so arranged that its operation will automatically result in the following: 

(a) A full service application of the brakes which will continue either until the train is brought to a stop, or, under control of the engineman, its speed is reduced to a predetermined rate. 

(b) When operating under a speed restriction, an application of the brakes when the speed of the train exceeds the predetermined rate and which will continue until the speed is reduced to that rate. 

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§ 236.826 System, automatic train stop.

A system so arranged that its operation will automatically result in the application of the brakes until the train has been brought to a stop. 

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§ 236.827 System, block signal.

A method of governing the movement of trains into or within one or more blocks by block signals or cab signals. 

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§ 236.828 System, traffic control.

A block signal system under which train movements are authorized by block signals whose indications supersede the superiority of trains for both opposing and following movements on the same track. 

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§ 236.829 Terminal, initial.

The starting point of a locomotive for a trip. 

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§ 236.830 Time, acknowledging.

As applied to an intermittent automatic train stop system, a predetermined time within which an automatic brake application may be forestalled by means of the acknowledging device. 

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§ 236.831 Time, delay.

As applied to an automatic train stop or train control system, the time which elapses after the onboard apparatus detects a more restrictive indication until the brakes start to apply. 

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§ 236.832 Train.

A locomotive or more than one locomotive coupled, with or without cars. 

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§ 236.833 Train, opposing.

A train, the movement of which is in a direction opposite to and toward another train on the same track. 

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§ 236.834 Trip.

A movement of a locomotive over all or any portion of automatic train stop, train control or cab signal territory between the terminals for that locomotive; a movement in one direction. 

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§ 236.835 Trunking

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        - A casing used to protect electrical conductors. 

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§ 236.836 Trunnion.

A cylindrical projection supporting a revolving part. 

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§ 236.837 Valve, electro-pneumatic.

A valve electrically operated which, when operated, will permit or prevent passage of air. 

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§ 236.838 Wire, shunt.

A wire forming part of a shunt circuit. 

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S&TC  FUNDAMENTALS

49 CFR 236

Subpart G

Definitions

The End

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