The Signalling Record Society

Acronyms, Signalling Terms, Railwayman's jargon &c.

This page should be regarded as “Work in Progress”. The webmaster will welcome additional information for this page.

Signal Fact 47

The Great Western Railway, astonishingly, installed a three position upper quadrant signal at Paddington in 1914.

It was a 'one off' automatic signal on the down main line, functioning as an advanced starting signal.

On this page will be found a selection of acronyms and other terms relevant to signalling, train describers and to other material on this web site and used either within the railway industry or by the signalling fraternity.

Some of the terms listed will not have been in common (universal) use. This particularly applies to Railwayman's jargon (slang) terms where the term used sometimes varied between different parts of the country or between railway companies. No attempt has been made in this list to indicate the likely geographic scope of such regional jargon as this can become blurred with the passage of time.

Where multiple definitions occur for the same acronym or term, the context in which it is used will normally make it obvious which definition applies.

Parts of this list initially appeared in "Broad Survey" published by the Friends of the National Railway Museum in 2000. They are included here with their permission. Other parts have been gathered from a variety of sources and / or contributed by users of this web site.

Acromym or Term	Explanation
A end	[i] The end of a multiple sets of points (eg. crossover) worked by a single lever or control, the A end tradionally being the nearest to the signalbox, then B, C, etc. In wide area power signal box territory the A end is that first encountered by a train proceeding in the down direction. [ii] The end of a station platform nearest London or other major location where platforms at an intermediate station are split for operational purposes. [iii] The end of a station platform nearest the buffer stops where platforms at a terminal station are split for operational purposes.
AB / ABS	Absolute Block System. Method of signalling designed to ensure that only one train will be authorised to be present in a specific section of line at one time. The section is normally between two adjacent signal boxes but intermediate block sections also exist. Primarily associated with mechanical signalling, the absolute block principles also apply to TCB (see below).
AB [PF]	Permissive Block System. Method of signalling that allows more than one train to be present in a specific section of line at one time.
ABCL	Automatic Barrier Crossing Locally Monitored. An automatic level crossing equipped with half barriers and road traffic signals, the correct operation of which is monitored by the train driver. Automatic Half Barrier Crossing
Abolish	Verb used in signal alteration notices, etc, to describe the permanent taking out of use, and "taking away" of, a signalbox, signal, siding etc. Used for distinction from "closing" in the case of signal boxes (which might "close" at 6am every Sunday and re-open on Monday), and from "remove" (which might mean "move", as in "the signal will be removed to a new location 200 yards nearer the box").
Acceptance of a Train	A term used in absolute block signalling where a signalman gives permission, by the block instrument, to the signalman at the preceding signal box for a train to proceed into the block section.
Accommodation Crossing	A private vehicular level crossing connecting land in the same ownership.
Advance	An alternative term for beyond.
Advance Signal	A running signal located beyond the starting signal, usually governing entrance to the block section ahead.
AHB	Automatic Half Barrier Crossing. An automatic level crossing equipped with half barriers, road traffic signals and telephones communicating with the supervising signalbox.
AHBC	Automatic Half Barrier Crossing. An automatic level crossing equipped with half barriers, road traffic signals and telephones communicating with the supervising signalbox.
AHBCL	Automatic Half Barrier Level Crossing. An automatic level crossing equipped with half barriers, road traffic signals monitored by the train crew.
AHBLC	Automatic Half Barrier Level Crossing. An automatic level crossing equipped with half barriers, road traffic signals and telephones communicating with the supervising signalbox.
AI	Area Inspector. Supervisory grade formerly in charge of the signalmen in a given area. Now replaced by the LOM.
ALC	Accommodation Level Crossing. Unsupervised level crossing provided to allow the owner of land bisected by the railway access across the line.
ALCRM	All Level Crossing Risk Model. Computer model of risks at level crossings, related to levels of road and rail traffic, methods of crossing operation, etc. Produces an overall risk score for each crossing.
ALR	Arm & Lamp Repeater. An instrument on the block shelf showing the signalman the position of a semaphore signal arm and whether the light is burning.
ALRMS	Access Level Crossing Risk Management System.
Annett's Key	A large metal key used to provide interlocking between, for example, a signal box and a ground frame. There is only one key, and it can be used to release a lever, or the whole frame, in the signal box, or the ground frame, but not both at the same time. Multiple patterns of key allow several instances to be used in one signal box, but each key will only fit its own lock. Invented by railway employee J E Annett.
Annett's Lock	A metal box with keyhole to receive an Annett’s Key, attached to a lever frame or ground frame and connected to the interlocking of other levers.
Annett's Shield	A thin metal plate mounted on a semaphore signal in front of the spectacle plate, so as to obscure the green aspect glass when the signal is at danger or caution. Thus a false indication cannot be given by sunlight illuminating the green glass, allowing a driver to see only the intended red (or yellow) light of the signal.
Annunciator	[i] Audible indicator provided in the signal box to advise the signalman of the arrival of a train at the home signal when that signal is at stop. [ii] Audible indicator provided in the signal box to advise the signalman that a train has left (cleared) an intermediate block section.
AOCL	Automatic Open Crossing Locally Monitored. An automatic level crossing equipped with road traffic signals, the correct operation of which is monitored by the train driver.
AOCL+B	Automatic Open Crossing Locally Monitored. An automatic level crossing equipped with road traffic signals plus barriers, the correct operation of which is monitored by the train driver.
AOCR	Automatic Open Crossing Remotely Monitored. An automatic level crossing equipped with road traffic signals the correct operation of which is monitored by the supervising signal box.
APC	Automatic Power Control. Magnet placed on sleeper ends on overhead electrified lines, to switch off and on the traction supply to a train, e.g. at neutral sections.
Approach Control	The restriction of the aspect of a signal to ensure that the driver can comply with the turnout speed or to control the speed of a train for a call-on, warning or shunt class of route.
Approach Locking	The locking of any route from a signal when a driver has or may have seen a proceed aspect. The route cannot be unlocked for a specified period of time that ensures that either the train has passed clear of the set route or has come to halt at the protecting signal.
Approach Release	An alternative term for approach control.
AR	Arm Repeater. An instrument on the block shelf showing the signalman the position of a semaphore signal arm.
Arming Loop	Part of TPWS track equipment further from a signal, which prepares the system to act if the train reaches the trigger loop in too short a time.
ARS	Automatic Route Setting. A system for setting routes without the action of the signalman based upon a stored timetable, train-running information, defined priority and selection criteria.
ASB	Adjoining Signal Box.
Aspect	Any valid indication of a signal.
ATC	Automatic Train Control [i] A term for the former Great Western Railway's electro mechanical system of advising the train driver of the aspect displayed by a distant signal. [ii] A term used to describe on board automation that supplements or replaces the driver's judgement for control of the train.
ATO	Automatic Train Operation.
ATP	Automatic Train Protection. A system that enforces compliance with speed restrictions and signal aspects by the train driver.
ATR	[i] Automatic Train Reporting. [ii] Automatic Train Regulation.
ATS	[i] Automatic Train Supervision. [ii] Automatic Train Stop.
Automatic Signal	A signal controlled by the passage of a train.
AWB	Advance Warning Board. A sign incorporating a St George's cross to inform the driver to regulate the speed of the train applicable over an open level crossing.
AWI	Advance Warning Indicator. Advance warning board for a PSR ahead, using an inverted triangle with yellow edging, showing the speed restriction ahead inside it in black numerals. Distinguished from the sign at the point where actual restriction applies, which has a circular board with a red edge, very like standard UK road speed limit signs.
AWS	Automatic Warning System. A system that provides audible and visual to the driver at the approach to signals, certain level crossings and speed restrictions.
Axle Counter	A method of train detection achieved, electronically, by counting the number of axles entering and leaving a track section. A calculation determines whether the track section is clear or occupied.
B
B end	[i] The end of a multiple sets of points (eg. crossover) worked by a single lever or control, next furthest away, the A end always being the nearest to the signalbox. [ii] The end of a station platform furthest from London or other major location where platforms at an intermediate station are split for operational purposes. [iii] The end of a station platform furthest the buffer stops where platforms at a terminal station are split for operational purposes.
Back Board	See Backboard.
Back Contact	Back contact is a relay contact that is made when the relay is de-energised and hence in normal electrical terminology would be normally closed.
Back Turn	Signalman's term for the afternoon shift.
Back-un	Railwayman's jargon for a distant signal.
Backboard	[i] An obsolete term for a distant signal. [ii] Matt black screen surrounding the aspects of a colour light signal, provided to enhance visibility against the background
Backing Signal	Signal controlling wrong direction movements within station limits.
Backlight	Small white light shown from the back of a semaphore signal towards the signalbox, only when the signal is on, to confirm the lamp is alight. When the signal is "off", a mechanical shutter, the backlight blinder, obscures the light.
Backlock	[i] An electrically operated lock that prevents a signal lever from being restored to the normal position until certain conditions have been met. [ii] a means of allowing a signalman to place a signal to danger immediately after a train has passed the signal or, in the case of an emergency, as it is approaching whilst retaining the interlocking of the levers that control points protected by the signal.
Balise	See Transponder below.
Bang Road	Railwayman's jargon term used when a train is proceeding in the opposite direction to that for which the line it is travelling on is signalled.
Bank(ing) Engine	Engine employed to assist other trains up steep gradients, either pulling from the front or pushing in the rear. If at the rear, sometimes not coupled to the main train, and in this case presenting a special problem to the signalman, as once it had pushed a train to the top of the incline and the latter had accelerated away, the bank engine was then left behind in section. Special rules, bell codes, etc, applied to banking engines, and on single lines a "banking staff" was sometimes used. A banking engine, or banker, may also be known as a Pilot Engine, especially if located at the front of a train. Release and return of banking engines was the reason for additional sidings at various summit-level boxes, e.g. Blackwell, Hawes Junction, and created additional work for the signalmen there.
Banner Repeating Signal	A signal in the format of a bar against a white background that gives the driver advance information of whether a signal with inadequate sighting distance is on or off. Usually illuminated during the hours of darkness.
Bell Code	Prescribed series of codes used when communicating between two locations using bells.
Berth Track circuit	The track circuit immediately on the approach to a signal.
Bi-directional line	A line on which signalling provides for running moves in both directions.
Big Dipper	Railwayman's jargon for a semaphore signal mounted high on a tall post.
Biscuit	Railwayman's jargon for a single line token.
Black Light	An empty bulb socket.
Black Oil	Railwayman's jargon for an unlit semaphore signal.
Black Signal	A colour light signal that is not displaying an aspect or a semaphore signal where the lamp, electric or paraffin, has failed.
Blackboard	Railwayman's jargon for an oblong shaped ground signal.
Blinder	A mechanical shutter which obscures the backlight of a semaphore signal.
Block Bell	A single stroke bell for communication between block posts.
Block Indicator	The part of a block instrument that provides the signalman with a continuous visual indication of the state of the line between adjacent signal boxes.
Block Joint	Joint between two rails incorporating insulation to separate two adjoining track circuits.
Block Post	A location where trains are signalled using the absolute block system.
Block Section	The section of line between the section signal of one signal box and the home signal of the next signal box.
Block Shelf	A shelf positioned over the levers on which are mounted the block instruments, block bells, telephones, signal arm indicators, colour light signal indicators and points position indicators.
Block Signalling	A system of controlling rail traffic defined by block sections. Normally only one train is permitted in a block section.
Block Switch	A switch that enables a signalbox to be closed by putting the signal boxes on each side in direct communication with each other.
Blocking Back	An operating process for the protection of movements that will result in the occupation of track within the acceptance area.
Board	Railwayman's jargon for a semaphore signal.
Bobbing	Fault on a track circuit where it intermittently indicates the presence of a train when in fact there is none there.
Bobby	Victorian term for a Signalman, dating way back to the earliest days before fixed signals, when railway policemen controlled trains by handsignals. The term was derived from the Meropolitan Police whose chief in the 1830s was Sir Robert Peel. It has remained in use until modern times.
Booking Boy / Lad	Employee in a signalbox employed solely to record train movements in the TRB, answer telephones, take messages etc, and absolutely forbidden to operate the signalling equipment. Usually a job given to new entrants to railway service, it often became the start point of a career in railway signalling.
BOP	Booking on Point. Location where train crew sign on and off duty.
Both Ways	(see Two Holes).
Bowtie Arm	A distinctive pattern of subsidiary semaphore signal arm, resembling a bow-tie and often used to control backing movements.
Box Boy	Alternative name for a Booking Boy.
Box Phone	Or "Box to Box", a telephone circuit linking just two adjacent signal boxes.
Braking Distance [Service]	The distance in which a train is capable of stopping from a given speed without undue discomfort to the passengers.
Break Section (Box)	Small signal box introduced approximately in the middle of a long block section to enable it to be worked as two shorter sections, reducing the headway required between successive trains. Often with only a Distant and Home signal in each direction, and no points at all. Often in bleak and remote locations where no station would ever be built, perhaps only staffed at busy times and otherwise switched out of circuit. Sometimes known as an "Intermediate" box, they were gradually replaced as signalmen's pay increased, and technology advanced, by Intermediate Block (IB) signals, and later by full track circuiting and TCB.
Bullseye	The lens in a paraffin lamp.
Bus Line or Phone	Abbreviation for "omnibus line", a telephone circuit connecting all signal boxes along a section of line, rather than running just between two boxes.
BW	Bridleway Crossing.
C
C Board	Commencement point for a temporary speed restriction.
C end	The end of a multiple sets of points (eg. crossover) worked by a single lever or control, next furthest away, the A end always being the nearest to the signalbox, followed by B.
C&P	Clipped and Padlocked. A term applied to pointwork placed out of use by attaching a large screw-operated clamp holding the switch rails in a given direction, and padlocking the clamp to prevent loosening and removal. Newly installed or redundant points are usually C&P for a period before commissioning, or after or decommissioning, in a running line. This covers the period between the physical provision or removal of the connection by the permanent way staff and the operational connection to, or disconnection from, the signalbox relay room by the S&T staff. Regional variations such as "clipped, spiked and padlocked" also existed.
C-DAS	Connected Driver Advisory Systems.
Call-on [Route Class]	A route that permits movement into an occupied section.
Calling On signal	A subsidiary semaphore or colour light signal of a distinctive pattern, permitting a low speed move past a main signal at danger for certain defined purposes.
Capstan Wheel	Large spoked wheel used in some types of equipment for winding level crossing gates. The wheel was mounted in a vertical plane, usually parallel to the end of the box adjoining the level crossing. "Capstan" is really a misnomer, as the nautical original worked in a horizontal plane, like a turnstile. The railway equipment more nearly resembles a ship's helm.
Cat's Eyes	Railwayman's jargon for the proceed aspect of a position light signal.
Catch Points	Trailing points provided for the purpose of derailing an unauthorised backwards movement such as a runaway train in order to protect an adjacent line or junction.
CAWS	Continuous Automatic Warning System. System in use on Iarnród Éireann.
CBI	Computer Based Interlocking.
CC	Control Centre
CCF	Control Centre of the Future
CCTV	[i] Closed Circuit Television. [ii] Manned level crossing (full barriers) monitored using closed circuit television.
CE	Civil Engineer.
Centre Balance Signal	Semaphore signal mounted on the front of a signal post that pivots centrally when being moved between the 'on' and 'off' positions or vice versa.
Cess	Part of the railway track and formation away from the ends of the sleepers. Forms part of the track drainage system.
Chargeman	[i] Grade introduced by British Railways in 1968 to replace that of Foreman and some Supervisors. [ii] Job title used for the senior signalman in a box where more than one signaller is employed.
Circuit Controller	Switch attached to a signalbox lever to enable it to control electrical circuits.
CL	Crossing Loop.
Clear [A Signal]	To change a signal aspect from its most restrictive aspect to a less restrictive aspect.
Clear Aspect	A colour light signal displaying a green aspect or a semaphore signal in the off position.
Clearance Bar	A bar operated from a lever in a signal box to prove that no vehicle is standing foul of the clearing point.
Clearance Point	The minimum distance from points and crossings for the position of the track circuit boundary to ensure that a vehicle on one line will not be foul of a movement on the other line.
Clearing Point	The point to which the line must be clear before a train can be accepted into a block section.
Co-acting Signal	An additional signal that is provided in an area of difficult sighting. It is mounted on the same post and duplicates the aspects of the signal with which it is associated.
Colour Light Signal	A signal that conveys information by coloured lights.
Common Crossing	V-shaped casting or assembly in a pair of points where the left-hand rail of one route intersects the right-hand rail of the other. The crossing is usually fixed, but on high-speed lines moveable crossings are used, enabling a smoother passage for the train over the route selected. These latter are also known as swingnose crossings.
Concentrator	Piece of telephone equipment enabling a signalman to answer a call on any of the lines coming into his box, using just one handset, and a console to select the relevant circuit. Replaced the previous array of telephones, one on each circuit.
Control	Central office with oversight and control of train running across a wide area, often including traction, rolling stock and traincrew resourcing as well as the actual movement and precedence of trains. In railway parlance often pronounced with the emphasis on the first syllable: CON-trol.
Controlled Signal	A signal that is controlled to red from a signal box or ground frame.
Cow's Horn	Lineside post used for catching single line tablets or tokens from passing trains.
CPCR	Coal Plant Control Room.
CR	Control Room.
Cripple	Damaged railway vehicle, most often a goods wagon, not fit to be moved or only able to be moved subject to a severe speed or other special restriction.
Cripple Siding	Siding for placing crippled wagons awaiting attention.
Crossing Keeper	Employee who operates a level crossing.
Crossing Place	Location on a single train where trains going in opposite directions may pass one another.
CSR	Cab Secure Radio. Radio system for communication between signallers and train drivers.
CT	Control Tower.
CTC	Centralised Traffic Control.
CTRL	Channel Tunnel Rail Link.
CWN	Carriage Working Notice.
D
D Sign	Sign attached to a signal post, in the shape of a letter D, telling the footplate crew that a Fireman's Call Plunger is available at the signal to enable compliance with Rule 55 without walking to the signalbox.
Dark Days	Turn of duty starting at 0001, or soon after, classified as an 'early turn' for payment as night rate enhancement didn't apply.
Darwin	Train Running Information System.
DEE	Digitally Enabling Electrification project started in 2014 as part of a Government innovation strategy for digitising the railway. Atkins collaborated with industry partners Laing O'Rourke, software specialist dhp11 and Imperial College London to help bring the project lifecycle of an electrification scheme into the digital age. [source: Rail Engineer June 2016].
DEL	Down Electric Line. Running line in the down direction equipped for electric trains.
Delayed Yellow	The approach control for a warning class route.
Delta Plate	Signal identification plate incorporating a triangular symbol, indicating that the signal is not a stop signal. The triangle resembles the fishtail notch of an old distant signal arm, turned through 90 degrees.
Departmental	Train run for the benefit of the railway itself, not directly revenue-earning. For example, a ballast, overhead line maintenance or de-icing train.
Depression Bar	A metal bar mounted alongside the rail in a position that causes it to be depressed by the wheel flange of a rail vehicle.
Derailer	Ramp-shaped block of steel which can be swung on to and off the running rail in a siding by a lever in the signal box, or by power operation. It is normally kept on the rail, where it will derail any wheel which should run against it, preventing a vehicle passing any further and possibly fouling an adjacent line. Sometimes used instead of trap points if space is limited. At first glance, a derailer appears similar to a scotch block, but its function is to throw the vehicle off the track rather than holding it in place.
Det	Abbreviation for Detonator.
Detection	The proof of the position of points, normal or reverse, to the interlocking.
Detonator	A disc shaped emergency audible warning device, placed on the railhead, which explodes when a train passes over it.
DFL	Down Fast Line. Running line in the down direction.
DGL	[i] Down Goods Line. Running line in the down direction. Before the advent of large area power signal boxes, where extrance and exit were controlled by different signal boxes. [ii] Down Goods Loop. Running line in the down direction. Before the advent of large area power signal boxes, where extrance and exit were controlled by the same signal box.
DI	District Inspector. Supervisory grade formerly in charge of the signalmen in a given area. Now replaced by the LOM.
Diamond Crossing	Intersection of two railway tracks, normally at a fairly shallow angle constructed from two common crossings and two obtuse crossings. The diamond-shaped space is formed by the rails in the centre of the crossing. More complex versions allow trains to switch between one route and another, along one or both long sides of the diamond. The switching tracks are termed "slips", hence "single slips" and "double slips".
Ding Ding And Away	Railwayman's jargon term for the act of a Driver accepting the Guard's starting signal of two rings on the train bell, and starting away without checking the signal aspect. Latterly formalised as a "SASPAD".
Direction Lever	Lever controlling the direction of traffic flow on a single line between two boxes, both with such a lever, and removing the need for a token system.
Disc Signal	A shunting or subsidiary signal consisting of a small disc that is rotated through 45 degrees to give a proceed indication.
Distant Arm Proving	A means of proving the signal arm to be in the caution position before acceptance can be given for a train.
Distant Signal	A signal capable of displaying cautionary and clear aspects but not a stop aspect.
DM	Down Main line. Running line in the down direction.
DML	Down Main line. Running line in the down direction.
Dod	Abbreviation of Tommy Dodd, railwayman's jargon term for a Ground Signal.
Doll	[i] Railwayman's jargon term for a Ground Signal. [ii] Short post on top of a signal gantry or bracket post on which the semaphore arm is mounted.
Dolly	Ground Signal.
Double Block	a variation in absolute block working where a following train is not accepted from the box in rear until the first has cleared the block section ahead, and "Train Out of Section" has been received from the box in advance. Thus there is always an empty block section between successive trains. Used in various circumstances where an extra margin of safety is required, e.g. in fog or for royal trains. Also known as Fog Block.
Double Yellow Aspect	A preliminary caution signal in four aspect signalling territory.
Down	A direction applied to a running route.
DPL	Down Passenger Loop. Running line in the down direction.
DRL	Down Relief Line. Running line in the down direction.
Drop Off Points	Form of trap points in sidings where the fixed stock rails spread outwards, wide-to-gauge. When the points are operated, the switch rails move outwards in opposite directions from within the four-foot to close the gap with both stock rails. A movement can then pass safely over. A vehicle running over the points when normal will drop straight down on to the trackbed, rather than be thrown off the track to left or right as happens with the more usual trap points; this may be necessary if there are running lines close by on both sides.
DRS	Down Refuge Siding.
DSL	[i] Down Slow Line. Running line in the down direction. [ii] Down Stour Line. Running line in the down direction (Stour Valley, West Midlands).
DTG-R	Distance to Go Radio. Used on London Underground.
Dummy	Railwayman's jargon term for a Ground Signal.
Duplicate Signal	An additional signal that is provided in an area of difficult sighting. It duplicates the aspects of the signal with which it is associated.
Dwarf	Railwayman's jargon term for a Ground Signal. The Southern Railway Working Over Appendix of 1934 referred to “disc or dwarf” signals.
E
Early Turn	Signalman's term for the morning shift.
Earth Fault	Slang expression for a train or vehicle resting on the earth (i.e. the ballast), having been derailed.
EBV	Engine & Brake Van. Just the locomotive and one or more (freight) brake vans.
ECI	Early Contractor Involvement.
ECML	East Coast Main Line.
Economiser	[i] An arrangement of the electric locking in a signal box where a circuit is normally disconnected, to save battery power. Prior to making a move where the locking may be invoked, the signalman energises the circuit, normally by the act of grasping the lever catch handle, or depressing a foot-operated plunger. Current is then supplied to the equipment, and if conditions permit the electric locking will be released. [ii] Device whereby a detonator placer actually places two detonators on the rail, some feet apart. If the first detonator explodes (as it should) when crushed by a passing train, the explosive blast dislodges the economiser holding the second detonator off the rail before the train reaches it, this saving it for future use. But if the first detonator is defective and does not explode, the second is still in place to provide a back-up.
ECP	Emergency Control Panel.
ECRO	Electric Control Room Operator. Person controlling the traction current on an electrified railway. In modern communications, the ECRO is the one person senior to the signalman in message handling protocol.
ECS	Empty Coaching Stock. A train comprising empty passenger or passenger rated vehicles.
EKT	Electric Key Token. A system of working trains on a single line.
E L & N	Early, Late and Night turns of duty.
Electronic Token	An electronic message transmitted by radio between a signal box and a train. The message gives authority, in visual form, to the driver for the train to proceed into the associated block section.
ELR	Engineer's Line Reference. Code applied to a line of route to aid record keeping.
Emergency Indicator	A lineside sign that inform the driver of an emergency speed restriction ahead.
Entrance-Exit System [NX]	A route setting system controlled by the operation of entrance and exit buttons and which initiates the setting of all points in the route.
EPS	Enhanced Permissable Speed(s).
Equal Bracket	Semaphore signal post where two dolls are mounted at the ends of a cross-beam, which is supported in the centre by a single main post. Thus each doll has an equal offset from the centre line of the signal.
ERO	Executive Research Office. The initials ERO or E.R.O. appeared as part of the stationery and stores reference on many documents issued by the London Midland & Scottish Railway and by British Railways, London Midland Region until overtaken by the BR series of stationery and stores numbering.
ERS	Emergency Replacement Switch. A switch that enables a signalman to replace an automatic signal to danger.
ERTMS	European Rail Traffic Management System. Europe wide system permitting interoperability of trains across national borders using a common means of signalling.
ESOC	Emergency Signals On Control. A switch that enables a signalman to replace all signals in an interlocking area to danger in a single operation.
ESR	Emergency Speed Restriction.
ET / ETB	[i] Electric Token Block. A signalling system used on single lines. Only one token [or tablet] can be issued at a time from the instruments for a defined block section. [ii] Electronic Block.
ETCS	European Train Control System.
ETD	Extension Trunk Dialling. Automatic landline telephone system covering the UK railway network. The name is now outdated, but was originally in contrast to the manual systems where "trunk" calls beyond a limited area had to be connected by the railway exchange operator. Post Office equivalent was STD (Subscriber Trunk Dialling).
ETS	Electric Train Staff. Development from the Electric Token system, using a metal staff as the authority handed to the driver. A full size ETS is over two feet long and a weighty object. See also METS.
F
Facing [Direction]	The direction of movement over points where the train meets the toe of the switch rail first.
Facing Points	The term applied to points where lines diverge.
Facing Road	Railwayman's jargon term used when a train is proceeding in the opposite direction to that for which the line it is travelling on is signalled.
Facing traffic	Describes traffic coming towards the speaker. Also, when on the track, it is safer to walk "facing traffic", i.e. facing oncoming trains, usually on the right-hand side of a normal double line in the UK.
Fail Safe	A design philosophy that results in failure placing and maintaining the railway in a safe state.
Feather(s)	[i] White lights route indicator mounted above a colour light signal showing a driver which route has been set for a train. [ii] Railwayman's jargon for the crossed bars placed over a signal not in use.
Fibre Optic	Signal where the light is directed to the display via optical (glass) fibres, such as modern types of banner repeater or route indicator.
Finial	Fitment at the top of a semaphore signal post.
Fireman's Call Plunger	Device provided at a stop signal to enable compliance with Rule 55 without walking to the signalbox.
Fishtail	Railwayman's jargon for a notched end semaphore distant signal.
Five Foot	A railwayman's term for the space between the two running rails of a line where the track gauge is 5 feet 3 inches.
Fixed Distant Signal	A distant signal capable of displaying only a caution aspect.
Flag (verb)	[i] Handsignalling to traincrews, either with a flag (day) or handlamp (night). May include fogsignalling, emergency speed restrictions, etc. Carried out either by a Signalman from the window of his box, or a handsignalman on the ground. For example: "Bill is flagging the Down Distant", or "I flagged the ballast train past the Up Starter". [ii] More specifically, to apply Block Telegraph Regulation 5, the Warning Arrangement. A Signalman verbally warns a Driver that the section ahead is clear, but the station or junction ahead is blocked, then waves him on with a green flag - green being the old colour for "Caution", when a white flag indicated "Proceed".
Flagging Signal	Distinctive subsidiary semaphore signal used to indicate to a Driver that he may proceed only under the Warning Arrangement (BT Reg 5), thus avoiding the need for physically flagging him on by the signalman from the box window. A nineteenth century term, later replaced by "Warning Signal".
Flank Protection	Protection from over running movements at the approach to converging tracks by additional signals or point interlocking.
Flashing Double Yellow [Aspect]	Informs the driver to expect a flashing single yellow at the next signal.
Flashing Green	Colour light signalling aspect used for trials of 140mph running. It gave the necessary increase in braking distance by confirming to a driver that the next signal would be displaying at least a (steady) green aspect.
Flashing Single Yellow [Aspect]	Informs the driver to expect a yellow at the next signal with the junction speed indicator set for the highest speed diverging route.
Flat Crossing	Intersection of two railway tracks or lines, normally at or almost at right-angles, with no facility for trains to move from one route to another. Usually found where one route crosses another such as existed at Newark and Retford, not between tracks on a single route. See also Diamond Crossing.
Fog	Performing duties as a Fogsignalman.
Fog Block	See Double Block.
Fog Object	Defined object visible from a signal box under normal conditions, but obscured when fog reaches a certain density.
Fog Signal	[i] Alternative name for a detonator. [ii] Colour light signal only switched into use in dense fog, to give drivers advance warning of the state of signals ahead.
Fogging	Performing duties as a Fogsignalman.
Fogging Machine	Single lever or small ground frame enabling a fogsignalman to operate detonator placers on lines remote from where he was stationed. Enabled one man to "fog" more than one signal, and avoided the need to cross the line in zero visibility.
Fogman	Abbreviation for Fogsignalman.
Fogsignalman	Role carried out when necessary due to fog or falling snow reducing visibility; normally undertaken by permanent way staff. Each man was allocated to a signal, or group of signals. According to the indication of the signal, he fixed or removed detonators on the line, and displayed appropriately coloured signals to the footplatemen of approaching trains with his handlamp. In extreme cases, the man could have to climb the signal ladder to discover if the signal arm was on or off. Largely rendered obsolete by colour light signalling.
Footballer	Special train run for the benefit of football fans going to or from a match.
Forever Amber	Railwayman's jargon for a distant signal permanently fixed at caution.
FORI	Fibre Optic Route Indicatior.
Form 1	Form titled thus, handed by management to a signaller at the end of a shift. Constitutes the start of a formal disciplinary process and is usually followed by a formal interview, which, if the signaller is guilty, concludes with a Form 2.
Form 2	Form titled thus, handed by management to a signaller confirming punishment awarded following conclusion of the formal disciplinary process.
Fouling Bar	Mechanical equipment used for train detection, which is activated by the wheel flange.
Fouling Point	The place where a vehicle standing on a converging line would come into contact with a vehicle on the other line.
Four Aspect Signalling	A system of colour light signalling with red, yellow, double yellow and green aspects resulting in a preliminary or first caution at least two signals before the signal at red.
Four Foot	A railwayman's term for the space between the two running rails of a line where the track gauge is 4 feet 8½ inches.
FP	Footpath Crossing. Level crossing provided for pedestrian use (only).
FPL	Facing Point Lock. A mechanical means of locking points.
Frog	Term for the V-shaped casting or assembly in a pair of points where the left-hand rail of one route intersects the right-hand rail of the other. Also properly termed the Common Crossing. The frog is usually fixed, but on high-speed lines moveable frogs are used, enabling a smoother passage for the train over the route selected. These latter are also known as swingnose crossings. Mainly used by modellers but also found on some installation diagrams with Sykes interlocking.
Front Contact	Front contact is a relay contact that is made when the relay is energised and hence in normal electrical terminology would be normally open.
G
G	In signal engineering documentation, relating to a colour light signal, denotes the green (Proceed) aspect.
G / GB	Gate Box. A control point for supervision of a level crossing. A release or verbal permission is required from the supervising signal box.
Ganger	Man in charge of a gang of Permanent Way men, comprising a Sub-Ganger and several "undermen", or "surfacemen".
Gangers Occupation Key	Large metal key, normally electrically locked in a keybox in a lineside hut or similar. If the section line was clear of traffic, the Permanent Way Ganger could remove this key, in co-operation with the signalmen on either side, and in doing so would break down the block working between the two boxes. Thus while he was in possession of the key, his safety, and that of his gang and perhaps trolley, were secured. There could be several such boxes spread along a single line section. The Ganger would have agreed with the signalman a time by which he must restore the key, to permit the passage of the next train. By restoring the key he gave his assurance that the line was again clear and fit for traffic. This system originated on the GWR.
Gantry	A signal bridge structure spanning two or more lines.
Gate Lock	Mechanical control holding the large level crossing gates locked across the roadway when signals are to be cleared for a train to pass.
Gate Stops	Stops provided in the centre of the road, and the railway, to prevent level crossing gates over-running, and thus failing to lock properly. Sometimes worked by a separate lever, sometimes linked to the gate mechanism and thus automatic.
Gateman	Another term for Crossing Keeper.
GEOGIS	Geographic Information System. Database of railway infrastructure developed by British Rail in the 1980s. Since superseeded.
GF	Ground Frame. A control point with levers and/or switches to permit local operation of points and signals in running lines and sidings. A release is required from the supervising signal box.
Girder Signals	Signal erected on a set of girders across the line. Later referred to as a signal bridge or gantry. {LBSCR signalling notices 187x]
GL	Goods Loop.
Goods Line	A running line that is not signalled to passenger train standards.
GPL	Ground Position Light signal.
GPRS	General Packet Radio Service.
Green [Aspect]	Displayed by a colour light signal indicating that the next signal (two signals in four aspect areas) will be displaying a proceed aspect.
Green Banner	Later three-aspect version of the banner repeater signal, with the standard "on" and "off" aspects, but also able to display the "off" aspect on a green background, indicating that the signal ahead is showing green rather than just any proceed aspect. Only made possible with the advent of fibre-optic technology.
Groundman	Particular role in fog-signalling, where the man works on the ground near the signal box, observing tail lamps, etc, as opposed to "fogging" a signal.
GSM	Global Systems Mobile. Network system that supports mobile communications over a (very) wide area.
GSM-R	Global Systems Mobile - Railways. Network system that supports mobile communications over a (very) wide area.
GSP	Ground Switch Panel.
H
HABD	Hot Axle Box Detector. Lineside equipment for detecting an overheated axle box on a train.
Half and half or Half Cock	A railwayman's description of points and semaphore signal arms that have not fully completed their movement.
Half bracket	Semaphore signal post with one or more dolls all offset to one side of the main post (usually to the right in the UK), where the horizontal member resembles half of an equal bracket structure.
Handsignalman	A person who authorises a driver to proceed during emergencies or shunting movements using a lamp, flag or handsignals.
Harbour Lights	Railwayman's jargon for junction route indicator lights.
Headshunt	A length of track that enables a shunting movement to take place without the need to occupy the adjacent running line.
Headway	The shortest distance or time interval between successive trains that allows the second train to run at normal speed and receive clear aspects.
HMRI	His / Her Majesty's Railway Inspectorate.
HNC	Home Normal Control. A means of proving that the home signal lever has been replaced before accepting a train from the preceding signalbox.
Home Signal	The first stop signal on the approach to a signal box in absolute block signalled territory, or the one nearest to the signal box if more than one home signal is provided.
Hot Strip	Feature in the moulding of a colour light signal lens which diverts a proportion of the main beam downwards and towards a Driver stationary at the signal. An alternative to Pigs Ears.
Hump Signal	An indicator for controlling shunt movements over the hump of an automated marshalling yard.
I
IB / IBS	Intermediate Block Section / Signal. A means of splitting a long block section in an absolute block signalled area into two shorter sections. May be controlled either by the signal box in rear (the usual arrangement) or the signal box in advance.
IBH	Intermediate Block Home Signal. Stop signal controlling the movements of trains between the two parts of an Intermediate Block Section.
IBJ / IRJ	Insulated Block or Rail Joint. A rail joint of insulated material to provide electrical separation for adjacent track circuits.
IECC	Integrated Electronic Control Centre. A computerised signalling control centre that incorporates computerised interlockings, automatic route setting. Train descriptions and indications of other functions are displayed on visual display units.
IFS	Individual Function Switch. Switch controlling a single function on a panel.
Illuminated Diagram	A panel on which the track layout controlled from the signalbox is represented with the state of track circuits and other functions indicated by coloured lights.
ILWS	Inductive Loop Warning System.
IMR	Interlocking Machine Room.
In Advance	An alternative term for beyond.
Inductor	[i] Permanent or electro-magnet placed between the rails on the approach to a signal as part of the AWS equipment. [ii] Magnet placed on sleeper ends on overhead electrified lines, to switch off and on the traction supply to a train, e.g. at neutral sections.
Interlinking	Electrical connection between block instrument and distant signal, so as to ensure the latter is "on" before "Line Clear" is given. Later developed to ensure the home signal is "on", and termed Home Normal Control, or HNC.
Interlocking	Equipment for the control and releasing of signals and points in a sequence that avoids unsafe conditions being created.
Interlocking Lever	A lever similar to a King Lever, but which functions only to alter the locking conditions within a box, without by itself enabling switching out.
Intermediate Box	See Break Section.
IPS	Individual Point Switch. Switch provided on a route-setting panel to enable a set of points to be operated individually, as opposed to set as part of a route. May be used for testing, or setting up an unsignalled route. All points switches on an IFS panel work in this way.
IRJ	Insulated Rail Joint. see Block Joint.
IRSE	Institution of Railway Signal Engineers.
J
Junction Indicator	An indicator provided at a junction signal to inform the driver of the route set. The indication is either 3 or 5 lights in a row.
K
K Point	Older NER term for a switch diamond.
KCI	Key Control Instrument. Type of block instrument.
King Lever	A lever that: [i] releases signals in opposing directions on one line of a passing loop or on a bi-directional line to enable that signal box to switch out completely or remain operative as a gate box. [ii] governs directional use of a bi-directional line within a single signal box area.
KICC	Kent Integrated Control Centre.
KL	Key Lock Instrument. Gate locking system at crossing locally managed.
KL(G)	Key Locks released by Gate Box which works the crossing and provides local interlocking between the gates and protecting signals.
KL(SB)	Key Locks released by supervising signal box or remote gate box.
KL(WR)	Key Locks. BR WR version of KL(G).
Know The Road	Drivers have to confirm their "route knowledge" of particular features on a route by periodically signing a card to that effect. A driver may not drive a train on a road for which he has not signed, without a conductor driver who does know that road. Thus a signalman may not be able to divert a train over an alternative route if the driver does not "know the road" and there is no conductor driver available.
KRI	Key Release Instrument.
KT	Key Token. A physical representation, given to the driver, of authority to proceed onto a single line.
L
Lamp Proving	A system that ensures that the required lamp is lit by measuring the current in the filament.
Late Turn	Signalman's term for the afternoon shift.
LB	Line Blocked. The state of a block section when no permission has been given for a train to enter.
LC	[i] Level Crossing. A location where a road, track or path crosses the railway on the level. [ii] Line Clear. The state of a block section after a train has been accepted but before it has entered the block section.
LCF	Level Crossing Frame.
LCP	Local Control Panel.
LCU	Level Crossing Unit.
LCWS	Local Control VDU Workstation.
LE	Light Engine. Locomotive travelling on its own (no train attached).
Leads	[i] Alternative name for 'Pulls'. [ii] Plates attached to levers on which their "pulls" are written.
Leatherhead Control	Form of signalling control where a train must be proved to have passed a second signal ahead before a second train can be allowed to pass the first signal behind it. Devised in the 1930's and first installed at Leatherhead, hence the name. This was an updated version of Sykes' Lock & Block, using electrical equipment and less reliant on failure-prone mechanical gear. Replaced in its turn by full track-circuiting, and thence TCB working.
LED	Light Emitting Diode.
Length	Stretch of track for which one Permanent Way gang is responsible. May be several miles of single line, or a shorter stretch on multiple-track routes.
Lever Collar	A device which is applied over the handle of a lever to remind the signalman that the lever must not be operated.
Leverman	Subordinate signalman in a box where there is more than one man on duty at a time.
LHSC	Left Hand Switch Closed. Term used when referring to the lie of a pair of points. When the observer is standing in the four-foot, looking at the points in the facing direction, if they are set to divert a train to the right (or to go straight ahead rather than divert to the left), then the left-hand switch is closed against the stock rail. This is the LHSC position, the opposite being RHSC. Thus the two terms replace the earlier usage of "normal" and "reverse", but there is no direct correlation: LHSC can be either of what would once have been called "normal" or "reverse", and for the points under consideration, RHSC will then be the opposite lie. This newer terminology applies especially where a modern layout is designed without specified normal and reverse positions. As a check, the observer on the track should be able to read the number of the points, as shown on a nearby sleeper - if the number is upside-down, there is a mis-match somewhere in the design, the diagrams or the testing schedule.
Lifting Bar	A bar which is mechanically moved adjacent to the railhead to prove clearance.
LINX	Layered Information Network Exchange.
Little-un	Railwayman's jargon for a calling-on shunting arm semaphore signal.
LMON	Locally Monitored.
LNW	London North Western.
LOC	[i] Local Override Control. [ii] Abbreviation for location, a metal cupboard or room beside the track containing a small quantity of signalling relays, power supply equipment, etc.
Lock and Block	An enhanced system of absolute block that has mechanical linkage between each block instrument and the associated running signals to ensure that these signals are restored to normal after the passage of each train. Each line clear release also requires proof of arrival of the previous train; this being achieved by means of a track mounted treadle.
Lock Stretcher Bar	A stretcher bar is a lateral steel bar linking the two moving blades of a pair of points, there may be two or three of them. If the points have a facing point lock (FPL), the locking plunger fits into a precision-cut notch in the stretcher bar nearest the toe of the points, and this is then termed the lock stretcher bar. Only once the FPL plunger is detected to be fully home can the relevant signals be cleared. See also "One Hole" and "Two Holes".
Locking Room	The lower part of a mechanical signal box, usually at ground level, containing the mechanical and electrical locking equipment and adjusters.
LOD (P)	Lock Out Device. Patrolman's lock out device. Inhibits movements in one direcction only on designated bi-directional line(s).
LOD (T)	Lock Out Device. Traffic lock out device. Inhibits all movements on designated line(s).
LOM	Local Operations Manager. Job title post 1994 privatisation. First line manager in charge of the signalmen in a given area.
Long Section Token	A type of token covering more than one section. It can be an electronic token or a physical token.
Looped	A train is "looped" when it is diverted from a main line to a Goods Loop or similar subsidiary line, often if it is slow-moving. Similar to "turned in".
LOS	Limit of Shunt Indicator. A position light signal or a sign to indicate where shunting movements must terminate on a line in the wrong direction. Normally marked with the letters "LOS".
Lower Quadrant	Semaphore signal that inclines downward from the horizontal by 45 or 60 degrees when giving a proceed or caution message to a driver.
LR	Lamp Repeater. Instrument on the block shelf showing the signalman whether the light is burning in a semaphore signal.
Lunar Lights	Railwayman's jargon for a white lights junction route indicator.
LX	Level Crossing.
M
MAA	Moving Annual Average.
Main Arm	An arm of a semaphore signal for a running movement.
Main Aspect	The red, single yellow, double yellow, green, flashing yellow and flashing double yellow aspects of a colour light signal.
Main [Route Class]	Route from a main signal for a running move that requires the section and overlap to be clear.
Mangle	Signalman's jargon for a particular type of level crossing gate winding apparatus, bearing a passing resemblance to a mangle.
Marks System	Early variety of time and motion study where a signalman's work was broken down into simple activities each awarded a number of "marks". Boxes with higher marks were staffed by signalmen of higher grades, and hence higher pay.
MAS	Multiple Aspect Signalling. A system of signalling using colour light signals, track circuit block and route setting.
MB	Manual Barrier. Level crossing with Manually operated lifting Barriers.
MCB	Manned Level Crossing Barriers operated locally by a signaller or crossing keeper. Usually with barriers across full width of the road.
MCB-CCTV	Manually Controlled Barriers. Operated by a signalman or crossing keeper, crossing clear confirmed by use of Closed Circuit Television.
MCB-OC	Manually Controlled Barriers. Crossing Keeper is On Call.
MCB-OD	Manually Controlled Barriers. A manned level crossing with full width barriers and equipped with Obstacle Detection equipment to allow automatic operation. Supervised as necessary from a remote sgnal box.
MCG	Manned Level Crossing Gates operated locally by a signaller or crossing keeper..
MCS	Modular Control System. Vaughan Harmon trademark.
METS	Miniature Electric Train Staff. A later variety of Electric Train Staff, reduced in length to under a foot, and only a few ounces in weight.
MG	Manned Gates. A less specific term than those below, denoting a level crossing with manually-operated gates, but giving no further details.
MGH	Manually Controlled Gates, Hand Worked.
MGW	Manually Controlled Gates with Wickets.
Miniature Arm	A semaphore signal arm that is shorter and narrower than the main arm.
Miniature Train Staff	A particular type of samller size token used in electric staff block working.
MLRI	Multi Lamp Route Indicator. An alpha numeric route indicator used in conjunction with main junction signals.
MOM	Mobile Operations Manager. Job title post 1994 privatisation. Field manager equipped with a road vehicle and responsible for first response at an incident.
Morpeth Board	A prominent lineside sign, with accompanying track magnet, advising drivers of the speed at an ensuing Permanent Speed Restriction and that they must commence braking to achieve the significant reduction in speed required. Name harks back to the accident at Morpeth in 1969 which led to its introduction.
MOS	Mobile Operations Supervisor. Job title post 1994 privatisation. Field supervisor equipped with a road vehicle and responsible for first response at an incident.
Mouse	A device that enables a signalman to enter data and to control points and signals in an IECC or computerised signalling system.
Moveable Diamonds	Southern Railway terms for Switch Diamonds.
Moveable elbow	Older name for a swingnose crossing.
Moveable Elbows	Great Western Railway terms for Switch Diamonds.
MP	Mile Post.
MPD	Motive Power Depot. Locomotive shed.
MSL	Miniature Stop Lights. Level crossing with Miniature Stop Lights.
MTIN	Miles per TIN.
MWL	Miniature Warning Lights. An automatic level crossing equipped with miniature red/green lights operated by approaching trains.
MWLB	Miniature Warning Light crossing equipped with Barriers.
MWLF	Miniature Warning Light crossing user worked Footpath.
MWLG	Miniature Warning Light crossing equipped with Gates.
MWLO	Miniature Warning Light Open crossing.
N
NB	No Block. Line worked without any form of block signalling.
NBP	Not a Block Post. Signal or gate box not functioning as a block post.
Night Turn	Signalman's term for the night shift.
NIRU	Not In Regular Use.
NMC	Network Management Centre.
NNM	Not Normally Manned. Signalling installation which is not regularly staffed; it may only be required for special movements, or redundant but not formally abolished.
Non-passable	Term applied to an automatic signal where the "automatic" sign is deliberately not displayed. This means a driver cannot invoke the rules allowing him to pass automatic signals in certain circumstances. This may be used to protect sub-station gaps, long tunnels, etc.
Normal [Position]	The position of the lever or switch in a signal box when no train is signalled to pass.
Normal [Points]	Position of points when set for the most used route. Where the points are operated mechanically by a lever, the position of the points when the lever is back in the normal position.
Normal [Signal]	The most restrictive aspect of a controlled signal or the aspect displayed by an automatic signal when no trains are present.
NRU	Not Regularly Used.
NST / NSKT	No Signalman Key Token / No Signaller Token. A system of working trains on a single line with the driver responsible for operating the token instruments that are remote from the controlling signal box. The controlling signalman has to press a release button to allow the token to be withdrawn.
NSTR	No Signaller Token Remote. A system of working trains on a single line with the driver responsible for operating the token instruments that are remote from the controlling signal box. The driver has to press a release button to allow the token to be withdrawn.
NX	See Entrance-Exit System.
NX(DB)	NX Double Button panel.
NX(KS)	NX Key Switch panel.
NX(PP)	NX Push-Push panel.
NX(TP)	NX Turn-Push panel.
O
OB	Over Bridge. Bridge allowing non-rail access across the line, above the railway.
OC	Open Crossing without road warning lights, protected only by signs.
Occupation Level Crossing	A private level crossing between premises and a public highway or between land and premises under common ownership.
Occupied	A track section having any part of a train on it.
OCS	[i] One Control Switch. A route setting signalling system with one control switch to control each route. [ii] On Company's Service. Marked on internal mail, parcel and materials traffic conveyed free of charge amongst commercial traffic. [iii] Operations Control System.
OD	See MCB-OD.
ODST	Operational Decision Support Tools.
OES	One Engine in Steam.
Off [Aspect]	[i] The arm of a semaphore or disc signal inclined at 45 degrees or more to indicate to the driver that he may proceed. [ii] A proceed aspect (double yellow, yellow or green) in a colour light signal.
Off the Road	A derailed vehicle or train can be said to be "Off the road".
Officer's Special	Train carrying only railway managers and staff, which although carrying passengers was subject to different block regulations, for example regarding the need to stop in section, perhaps to examine civil engineering works or new signalling.
OJEU	Official Journal of the European Union.
OLC	Occupation Level Crossing. Level crossing provided to allow the owner of land bisected by the railway access across the line.
Old England	The surface of the ground, or the ballast. If a wagon is said to be resting on Old England, it is derailed.
OLE	Overhead Line Equipment. All of the trackside equipment involved with supply of traction current on overhead lines.
Omnibus Line or Phone	Telephone circuit connecting all signal boxes along a section of line, rather than running just between two boxes.
On [Aspect]	[i] The arm of a semaphore signal in the horizontal (stop) position. [ii] The most restrictive (caution) aspect in a colour light distant signal. [iii] A red (stop) aspect in a colour light signal.
One Hole	Note found on signalling diagrams at points fitted with a Facing Point Lock, indicating that there is only one port (notch) cut in the lock stretcher bar. Thus the FPL can lock the points only in one of the two possible positions. Also expressed as "Locks..." or "Bolts One Way".
One Way	See One Hole.
Open	Open Crossing. No road warning lights provided.
OOU	Out of Use.
OTNS	One Train Working where staff is not provided.
OTS	One Train Working With Staff.
OTW	One Train Working Without Staff.
Out of Correspondence	A railwayman's term for the condition where normal or reverse detection cannot be obtained.
Out of the Box	A signalman taken "out of the box" is removed from normal duty, possibly for training, sent home sick, suspended or dismissed according to circumstances.
Outer Home Signal	An additional stop signal in absolute block working that allows a signalman either to accept a second train before the preceding train has entered the next block section or to give simultaneous acceptance for a train on each line at a converging junction.
Overlap	A safety margin beyond a stop signal provided as a precaution for misjudgement in braking.
P
P&C	Points and Crossings.
Panel	Control console with electrical switches to operate points and signals, or set routes through a layout. Hence a "panel box", a signalbox built to accommodate a panel, or a traditional box converted by removing the lever frame. Historically intermediate between lever frames (and power frames) and VDU-based systems.
Panel Box	Signalbox built to accommodate a panel.
Passenger Line	A line signalled to the standard laid down in the Board of Trade / Ministry of Transport / Health and Safety Executive Requirements for the working of trains conveying passengers.
Passing Out	Process of examining a signalman and passing him as competent to work a certain box. Although he may have trained and qualified in general terms, a man has to be "passed out" individually for each box he is to work, to cater for the local conditions in each case.
PB	Permissive (Block) Working. A method of working that allows running movements into an occupied block section.
Peg	[i] Railwayman's jargon for a semaphore signal. [ii] A pin that the signalman applies to retain the operating handle of a block instrument in the line clear or in the train on line position. This instrument is known as the pegging instrument. The partner instrument is known as the non pegging instrument.
Peg Over	The act of moving a block instrument to show the "Train-on-Line" and placing the peg in the handle to hold it at "Train-on-Line" position.
Peg Up	The act of moving a block instrument to show the "Line-Clear" and placing the peg in the handle to hold it at "Line-Clear"or "Train-on-Line" position.
PF	Permissive Working. For classes 3 to 8 and 0 trains.
Phantom (aspect)	Aspect in a colour light signal appearing to be lit, when in fact it is not. May deceive drivers if it is bright enough. Normally caused by sunlight reflecting from inside a lens group, having acquired the appropriate signalling colour as it does so. Later optical designs reduced phantoms, and LED signals have eliminated the hazard.
Pig's Ears	Small additional coloured lamps provided on the side of a colour light signal head, nearest a driver stopped at the signal, to assist him when he is below the main beam of the signal's main lenses. From the appearance of the small hoods fitted over each aspect..
Pilot	[i] Abbreviation of Pilotman. [ii] Pilot Engine, running some minutes in front of a particularly important movement, e.g. the royal train, to ensure the line is clear. [iii] Additional Engine attached in front of the train engine to provide additional power. [iv] Term loosely applied to a Bank engine. [v] Shunting engine working purely in a yard area, e.g. colliery, docks, marshalling yard or a large passenger terminus.
Pilotman	A person appointed to authorise movements on a line during a period of the failure of equipment, repairs or obstructions.
PL	Passenger Loop.
Platform Starting Signal	A stop signal at the departure end of a passenger station platform.
Please Explain	Letter sent by management to a signaller asking for an explanation of some irregularity or incident.
PLGS	Position Light Ground Signal.
PLJI	Position Light Junction Indicator. An indicator that displays the route at a signal by means of a row of white lights.
PLOD	Patrolman's LockOut Device. Lineside switch enabling the Permanent Way patrolman to temporarily lock out of use certain signalling functions, e.g. reversible working, for his own personal safety while examining the line.
PLS	Position Light Signal. A signal that displays its aspects by means of a row of lights.
PMUX	Panel Multiplexer. The interface between the control system in a signal box and the interlocking.
PO	Private Owner Wagon. Freight vehicles, mostly mineral wagons and vans, owned by specific customers of the railway for transport of goods to and from their own depots and yards. The PO fleet was requisitioned early in World War 2 and made common user and subsequently became part of the British Railways common user fleet.
POGO	Power Operated Gate Opener Solar powered gate opening system for user worked crossings made by Gatecare Limited, Tyson Courtyard, Weldon South Industrial Estate, Corby NN18 8AZ.
Point Detector	A device for proving that points have fully completed their movement before a signal can be cleared to authorise a train movement over the points.
PON	Periodical Operating Notice.
Possession	[i] The stoppage of trains on a defined section of line to allow engineering work to take place. [ii] The disconnection or restricted use of signalling equipment to enable work to be carried out.
Power Box	A signal box with all functions being achieved through the application of electric, electronic, hydraulic or pneumatic devices.
Power Frame	Signalling lever frame of reduced size, with miniature levers which operate all of the signals, points, etc by electric, pneumatic or hydraulic means. An intermediate development between the full size mechanical lever frame and the IFS panel.
PPM	Public Performance Measure.
Precede	(verb) Indicates that equipment must be operated in a certain order, e.g. the siding points precede the shunting signal for moves out on to the main line..
Preliminary Caution [Aspect]	A signal aspect to inform the driver that the next signal is displaying a caution aspect.
PP	Permissive Working. Full use for class 1, 2, 5 and 0 trains.
PP-A	Permissive Working. Attching and contingency use only for class 1, 2, 5 and 0 trains.
PP-C	Permissive Working. Contingency use only for class 1, 2, 5 and 0 trains.
PRI	Preliminary Route Indicator. Signal displaying an illuminated arrow to show a driver his route at a junction ahead. It is not a stop signal, but is provided where braking requirements differ according to the route to be taken at the junction. A replacement for the earlier splitting distant signal.
Proceed [Aspect]	A signal aspect that permits the driver to pass the signal.
PSB	Power signal box. A signal box with all functions being achieved through the application of electric, electronic, hydraulic or pneumatic devices.
PSR	Permanent Speed Restriction. A long term restriction for a section of line that is less than the overall line speed.
PTT	Public Timetable. Book or leaflet containing the times of passenger trains advertised to the travelling public together with relevant commercial information.
Pulling Off	The act of clearing a (usually, semaphore) signal, by pulling the lever to move the signal to the "off" position.
Pulls	The numbers of the levers in a mechanical box which must be pulled to release a given target lever. So, if to clear signal 23, points 14 and 18 must be pulled, then "14.18" are the "pulls" for 23, and these numbers may be signwritten on lever 23 or its description plate.
Pulpit	Raised stand with rails round three sides (entrance steps on the fourth) to enable signalman to stand by the driving cab window and speak to the driver whilst exchanging single line tokens.
Pumping Up	Act of restoring and then resetting a signal switch after a train on an IFS panel, to enable the signal to clear again when conditions permit without further intervention from the signalman at that time. Can also apply to a colour light worked from a frame if the circuit conditions permit - then it's called "re-stroking".
Putting Back	Act of restoring a signal to caution or danger, originally by putting the lever back in the frame, but the term is now also used for colour light signals.
R
R	In signal engineering documentation, relating to a colour light signal, means the red (Danger) aspect.
R/G	Miniature Red/Green warning lights including miniature stop lights.
RA	Right Away. An indicator that displays R or RA to inform the driver that the train has permission to depart from a platform.
RAI	Right Away Indicator. An indicator that displays R or RA to inform the driver that the train has permission to depart from a platform.
RBC	[i] Return Bell Communication. Simple circuit between a signal box and station platform, gate box or perhaps ground frame, with a plunger and single-stroke bell at each end. Pre-arranged signals are used for standard messages (and differ at each location), e.g. Shunter to Signalman 2 pause 3 beats: open Goods Siding points; Signalman to Shunter 4 beats: Clear Down Line. [ii] Radio Block Centre.
RC	Remotely Controlled level crossing, manned remotely.
Rear	Behind, as in behind the observer. Thus a train should come to rest a few yards "in rear" of a stop signal. In the case of a station footbridge visible beyond the signal: the bridge is "in advance" of the signal, even though in everyday speech it could be said to be "behind" it. Conversely, the signal is so-many yards "in rear" of the bridge. In railway terms, running train movements on the right line in the right direction always move in the direction from rear to advance.
Rear Signal	A stop signal encountered on approach to a location, in rear (see above) of the signal box. Later called the Home Signal. [LBSCR Signalling Notices pre-1880]
Red [Aspect]	The stop aspect of a colour light signal.
Regulating	Act of deciding the order in which trains should run, when circumstances have disrupted the booked (timetabled) working. Only applicable at boxes controlling junctions, or access to / from duplicate running lines, and considered a more skilled activity than ordinary train signalling. May be done in conjunction with a Control Office.
Relay	An electromechanical switching device used in signalling systems.
Relay Room	Room within a power signal box, usually at ground level, containing the relays and other electrical locking equipment. Also applies to a separate building for the same purpose separate to the signal box.
Release Key	Key, resembling a simple door key, which could be used to unlock a block instrument, or operate a release switch in a separate keyhole in the block shelf. Also known as a Sykes' Key, from the manufacturer. All locks were the same, the same key would operate one in any box on any railway.
Relief	[i] Loose term referring to the staffing of boxes, generally meaning "replacement". A man's "relief" might be the man due to take over on the next shift. + [ii] Additional running line to provide additional traffic capacity.
Relief Signalman	Higher graded signalman trained to operate a number of boxes, who covered for absences such as leave, sickness, vacancies, etc. over a given area.
Reminder Appliance	A device to remind the signalman that a particular control switch or lever should not be operated.
Remote Interlocking	Building containing electrical locking equipment sited remotely from the controlling signal box.
Repeater	Electrical instrument on the block shelf, showing the signalman by deflection of a pointer, coloured lights, etc, either the aspect of a signal, or whether the light is burning, or bridge bolts are locked in place, and so on.
Repeater Signal	A signal, that is not a stop signal, provided to inform the driver of the state of the next stop signal ahead.
Replacement switch	Similar to ERS but used for everyday purposes and not just in an emergency. Applies to one signal only.
Replacer	Mechanical equipment which replaces a semaphore signal to danger independently of the signalman doing so, e.g. after a train passes a treadle.
Re-stroking	Act of restoring and then immediately re-reversing a lever working a colour light signal after a train has passed, to enable the signal to clear again when conditions permit without further intervention from the signalman at that time. Can also apply on an IFS panel if the circuit conditions permit - then known as "pumping up".
RETB	Radio Electronic Token Block usually accompanied by a channel number. A signalling system for single lines where the authority for the driver to proceed is in the form of a cab signal received as radio transmitted data message from the controlling signalbox.
Reverse [Points]	The opposite position to normal [points].
Reversible Line	Running line fully equipped with signalling for use in either direction. More comprehensively equipped than the "wrong" direction of a line under SIMBIDS.
RG or R/G	Red Green. Level crossing with miniature Red & Green warning lights.
RHTT	Rail Head Treatment Train.
RI	Relay Interlocking.
Right Side Failure	A failure that does not result in a reduction of protection to trains.
RII	Relay Interlocking Interface.
RL	Relief Line. An additional running line.
Road	Loose term for either a single railway track, e.g. Coal Road, Platform Road, Down Road, or a complete line, e.g. the Old Road, the Brighton Road.
ROC	Rail Operating Centre. Other variants seen are not official.
Rotary Block	An absolute block system, devised by the Midland Railway, that forces the signalman to restore the appropriate running signals to normal before accepting a second train from the signal box in rear.
Route	The path along the section of track between two successive signals.
Route Indicator	An illuminated letter or digit associated with a signal where more than one route exists.
Route Setting	Design philosophy for a signalling control system where the signalman sets up a route for a train from A to B as one operation, rather than having to set all of the points and signals individually by their own separate controls, as on an IFS panel. OCS and Entrance-Exit panels are both examples of route setting systems.
RRI	Route Relay Interlocking. An interlocking comprising relays. Operation of the control switch by the signalman for a desired route sets up a sequence of operations that determines the availability of the route, then sets and locks the points within the route and finally clears the signal.
RSF	Right Side Failure. A failure condition that does not result in any reduction of operational safety.
Rule 55	Rule introduced c1890 setting out the procedures to be carried out when a train is detained at a stop signal.
Rule 55 Diamond	Signal post-mounted sign in the shape of an elongated white diamond, indicating that compliance with Rule 55 was not necessary, other than the sounding of the engine whistle. Fitted where a track circuit, lock and block, or other apparatus protected the standing train.
Running Dummy	Railwayman's jargon term for a Ground Signal that is required to be cleared for the passage of a train in addition to normal running signals.
Running Line	A line that runs between two distinct locations.
Running Movement	A normal train movement on a running line that is controlled by main signals.
Running Shunt	Railwayman's jargon term for a Ground Signal that is required to be cleared for the passage of a train in addition to normal running signals.
Running Signal	An alternative name for a main signal.
S
S&C	Switches and Crossings.
S&F	Switches and Fittings.
S&T	[i] Signal & Telegraph. Older definition. [ii] Signal & Telecommunications. Newer definition.
SASPAD	Starting Against Signal Passed At Danger. A type of SPAD incident where a Driver starts from rest against a signal at danger.
SB	Signal Box.
SC	Signalling Centre.
SCC	[i] Signalling Control Centre. National Rail. [ii] Service Control Centre. London Underground. [iii] Supervisory Control Centre.
Scotch Block	Also known as a Wheel Stop. A shaped wood or metal block mounted so it can be swung across the rail in a siding. Its concave curved face receives the tyre of a wagon wheel rolling against it, stopping the vehicle from moving any further. Can be worked from a signal box, ground frame, or by hand. Similar to a derailer except that it stops the vehicle on the track rather than throwing it off.
Scrubber	Signalman’s slang for a Rail Head Treatment Train (RHTT), run by Network Rail and designed to combat poor adhesion due to dead leaves, etc. Previously known as a “Sandite” train.
SCS	Signalling Control System.
SCU	Signalling Compatibility Unit.
SDC	Service Delivery Centre.
SE	SouthEastern.
Sealed Release	Press button switch fitted on the block shelf to bypass electrical locking in case of failure, etc. It was mounted inside a metal box with a glass front, and could only be operated by first breaking the glass. A serially numbered paper seal behind the glass was thus destroyed, giving evidence of use of the release, which had then to be reported to management and also to the technician for attention for repair.
Searchlight Signal	A colour light signal that changes aspects by means of coloured lens being positioned in front of a lamp.
Section Signal	A stop signal that controls entry to a block section or an intermediate block section.
Selected	Two or more separate functions, worked by one control, are said to be "selected" if the setting of another control automatically decides which one of the two operates. The signalman does not have to do the selecting separately. Especially in mechanical boxes, this provided a means to work extra signals without installing extra levers, as long as the applications of the pair of signals were mutually exclusive.
Semaphore Signal	A signal that informs the driver by means of a mechanical arm by day and coloured lights by night.
Semi Automatic Signal	A signal normally operated by the passage of trains but which can also be controlled from a signal box, gate box or a ground frame.
Sequential Locking	Locking that forces the signalman to operate the signals in a defined sequence. It is usually associated with mechanical interlocking in absolute block working to ensure the replacement of running signals behind each train.
SER	Signalling Equipment Room.
Service Braking	A train brake application rate that does not cause discomfort or alarm to passengers.
Setting Back	A short distance shunting movement against the normal direction of running.
Shot	[i] Another term for detonator. [ii] Place a detonator under a train: "I shot the Derby train."
Shunt [Route Class]	A route used for low speed non-passenger (usually) movements.
Shunt Ahead Signal	A subsidiary signal that authorises shunt movements ahead of the section signal.
Shunting Frame	A manned control point released by the main signal box for the control of local shunting movements.
Shunting Movement	A short distance movement along running lines.
SICA	Signalling Infrastructure Condition Assessment.
Sighting	Process of locating and focussing a signal to best advantage for an approaching Driver, a collaboration between the signal engineers and traction staff. Easily confused with, but not, "siting". Thus: "the signal was sighted for best visibility across the curve", not "the signal was sited...".
Sighting Board	White painted board or brickwork behind a semaphore signal to improve sighting of the signal by drivers.
Sighting Distance	The maximum distance at which a driver can see the aspect of a signal he is approaching.
Sighting Screen	Large screen erected at a station to prevent drivers misreading signals some way away as a guard's green signal to start.
Signal Box Panel	A panel in a signalbox that gives a diagrammatic representation of the track layout controlled from the signalbox along with the switches required to control the movements of trains.
Signal Post Replacement Switch	A switch mounted on a colour signal post to replace and maintain the signal aspect at danger during an emergency or during engineering operations.
Signaller	Modern job title replacing that of Signalman.
Signalman & Signalwoman	A person appointed to work a signal box that was also a block post. Lady signalmen were sometimes known as a Signalwoman. In more recent time, with an eye on equality compliance and political correctness, the job title has changed to the no-gender one of Signaller.
SIMBIDS	Simplified Bi-Directional Signalling to allow reversible working on a double or multi-track line whilst repairs are carried out.
Simplifier	Condensed version of the current timetable, listing the regular trains to be signalled during the day and their normal running order.
Single Stroke Bell	Bell which sounds a single beat every time current is passed through it.
Single Yellow [Aspect]	The aspect at a colour light signal that informs the driver that the next signal is at red.
SIP	Strike In Point. Trigger point for automated level crossing operation.
SITT	Snow & Ice Treatment Train.
Six Bells	Signalman’s slang for the block bell code “Obstruction Danger – 6 [beats] consecutively”, used in dire emergency and loosely described as “stop everything”.
Six Foot	A railwayman's term for the space between two parallel railway lines.
Slip points	Points laid in in a diamond crossing, e.g. a crossover between Up and Down lines may have a slip connection from the crossover into a siding outside the main running lines. Alternatively, slip connections on a diamond crossing enable trains to move between one route and the other, rather than merely cross the second route.
Slip Signal	Small size distant signal used to indicate to a driver that it is safe to approach a station where slip carriages are detached at the permitted speed.
Slipping	Practice of uncoupling a rear portion of a train travelling at speed, to enable it to serve a station where the main train did not stop. Required complex arrangements for uncoupling and disconnecting the brake pipes, communication cord, etc, special arrangements of tail lamps and a separate guard and brake compartment on the "slip portion". Extra safety precautions were also needed, as slipping infringes the basic principle of absolute block working, by having two separate trains moving in one block section at the same time. Complications also arose with stock balancing, as the slip portion had to be returned by a stopping train for the next day's working.
Slotting	A signalling function involving two or more signal boxes or control points in its operation.
SLW	Single Line Working.
SMT	Signalling Maintenance Testing.
SMTH	Signalling Maintenance Tester's Handbook.
SN	Special Notice.
Somersault Signal	Semaphore signal mounted to the side of a signal post that pivots centrally when being moved between the 'on' and 'off' positions or vice versa.
SPAD	Signal Passed At Danger. The act of driving a train past a signal, including any subsidiary signals, where all are exhibiting a stop aspect.
SPADI	Signal Passed At Danger Indicator. Modified three-aspect colour light signal, fitted with one steady and two flashing red aspects, a blue reflective backboard and an audible warning, installed at high SPAD risk locations. Normally inactive, the SPADI operates if track circuit conditions indicate a SPAD has occurred, and may display towards the train causing the SPAD, or towards an adjacent track where another movement may be endangered.
SPADMIS	Signal Passed At Danger Management Information System.
Spag Block	An abbreviation for Spagnoletti Block, a type of block instrument invented by Charles Spagnoletti, used on the Metropolitan and Great Western railways.
Spate Indicator	A trackside sign to inform the driver that a temporary speed restriction has been withdrawn.
Speaking Telegraph	Term first used before the invention of the telephone, for a telegraph circuit carrying messages in code letters (e.g. in Morse). These were made audible at the receiving end by a magnetised needle moving left or right, according to the polarity of the signal received, and hitting one of two stops, each of which made a different sound. So for instance a Morse "dot" would be signalled by a leftward deflection, producing a "tink" sound, whereas a "dash" would move the needle to the right and produce a "tonk". Thus a signalman could listen to messages while carrying out other work.
Spectacle	The frame on a semaphore signal arm which holds the coloured glass.
Speed Board	A lineside indicator showing the maximum speed allowed for the section ahead.
Speed Indicator	A trackside sign that marks the start of a temporary speed restriction and indicates the permitted speed.
Splitting Distant Signals	Two (or more) adjacent distant signals that inform the driver of the route to be taken beyond the next signal.
Sprag	Piece of rough timber, maybe two to three feet long and with a handle shaped on one end, formerly used by guards, shunters, etc to secure unbraked goods wagons. The sprag was thrust through a gap between spokes in a wheel, and fouled the ballast after the wheel had turned a small distance, stopping the vehicle.
Spring Points	Trailable points, with a spring which restores them to the normal lie if run through from the less-used direction.
SPT	Signal Post Telephone. A telephone provided at a signal for the purposes of communication with the signalman.
SRAWS	Southern Region Automatic Warning System. Development of the original AWS, which required the driver to acknowledge each aspect by a separate control, not just with one button. Initially developed by the BR(S) for vigilance purposes, then taken over by BRB HQ and renamed Signal Repeating AWS, but never entered service beyond the initial trial.
SRI	Signalling Restructuring Initiative.
SSI	Solid State Interlocking. A processor based system for controlling the interlocking between points and signals and the control of lineside signalling functions.
SSM	Shift Signalling Manager.
SSR	Sub-Surface Railway. E.g. District Line in London.
SSDC	Signalling Systems Direct Current.
SSIC	Solid State Interlocking Controller.
SSIDES	Solid State Interlocking Design.
SSIDWS	Solid State Interlocking Design Work Station.
SSP	[i] Signalling Supply Point. [ii] Standard Signalling Principle.
SSTD	Solid State Train Describer.
Staff	See Train Staff below.
Starter / Starting Signal	[i] An alternative name for a section signal. [ii] First stop signal in advance of the signal box if there is more than one such signal.
Station Limits	The portion of the line between the home signal and the section signal controlled by the same signal box.
Stencil Indicator	A low power alpha numeric route indicator to indicate to the driver the route that will be taken.
Stick	Railwayman's jargon for a semaphore signal.
STN	Special Traffic Notice.
Stock Rail	The fixed rail on each side of a set of points against which the switch rail fits.
Stop Signal	A signal capable of displaying a danger aspect.
STOPS	Signalling and Telecommunications Outturn Processing System.
Sub	[i] Abbreviation for a subsidiary signal. [ii] Substation where traction current is fed to the overhead line or conductor rail. Important to signallers as electric trains must not be stopped where they could bridge a gap between two adjacent power feeding sections.
Subsidiary Signal	An additional semaphore or position light signal controlling shunting movements and / or movements onto occupied tracks.
Sunflower	A driver's term for the caution display on the AWS indicator in the driving cab.
Suppression	Inhibition of the operation of AWS track equipment for movements to which it does not apply.
Swinging The Overlap	Procedure whereby a signalman initially accepts a train using a certain overlap, possibly on the wrong route, but then (before the train is too close) alters the route to the desired one, which may not initially have been free.
Swingnose Crossing	Crossing (points or diamond) equipped with a moveable common crossing.
Switch Diamonds	A diamond crossing in which the fixed obtuse crossings are replaced by short switch rails, similar to those in points but with a blunt end. These move together so that the rails are aligned either for one straight route or for the other. In some ways appear similar to two points placed toe-to-toe. FPLs provided as appropriate. In mechanical installations they are normally operated by a separate lever. In power installations they are usually worked in conjunction with adjacent points. Normally used in very acute crossings to reduce wear and permit higher speeds. Originally introduced around 1900 but more widely used from 1930s.
Switch Rail	The moving portion of a rail on each side of a set of points.
Switching Out	Taking a signal box out of use by linking the block instruments in the signal boxes either side of it. The routine and usually regular closure of a signalbox by linking the signal boxes on either side while the line itself remains open.
SWTH	Signalling Works Testing Handbook.
Sykes Key	Alternative name for a Release Key used as part of Sykes 'Lock and Block' signalling manufactured by W R Sykes Interlocking Signal Company. Also known as a SYX key from that company's trademark.
T
T	[i] Telephone. [ii] Telephone Working
[T]	Accommodation / Occupation crossing with Telephone.
T (number)	Formalised method of taking possession of a line, as detailed in the section of the rule book identified by the same letter / number code.
T Board	End point of a temporary speed restriction.
T-COD	Track Circuit Operating Device. Tool used to short circuit the two running rails when necessary to operate a track circuit without a train being present.
TA	Train Approaching indicator.
Tablet	A particular type of token used in electric token block working.
TAC	Train Arrived Complete. Plunger on a station platform used by a Guard or other staff member to give 3 beats on a single-stroke bell in the signal box, indicating that his train has arrived complete. Used where a train terminates before the tail lamp has passed the signal box, and thus cannot be observed by the signalman. (Rule 147) Unlike an RBC, the signalman cannot ring a bell at the platform with this circuit.
TADPOLE	Software tool used by Atkins as part of the DEE project. [source: Rail Engineer June 2016].
Taking Off	Act of clearing a (usually, colour light) signal, individually where the equipment permits, as opposed to as part of a route-setting manoeuvre.
Taking the Marks	Measuring the work done in a box by recording "marks", to verify or amend the classification of a box for pay and staffing purposes.
Tall Dwarf	Railwayman's jargon term for a Ground Signal raised up on a post.
Target	Red disc or diamond shaped placed on level crossing gates indicating that the gates are closed and acting as a stop signal.
Target Number	Local trip or shunting locomotive diagram number. Originates from the practice of displaying the trip diagram number on a disc or target attached to the locomotive.
TASS	Tilt Authorisation & Speed Supervision.
TB	Tokenless Block. A method of working single lines without using a physical token.
TB (SC)	Scottish Tokenless Block. A method of working single lines without using a physical token.
TC	Track Circuit. An electrical device using the running rails as part of a circuit that detects the absence of all or part of a train on a defined section of line.
TCA	Track Circuit Actuator.
TCB	Track Circuit Block. A method of working trains over a section of line where safety is ensured by the use of track circuits. Primarily associated with colour light signalling, the block section is between two successive running (stop) signals. Block instruments are not required.
TCF	Track Circuit Failure.
TCI	Track Circuit Interrupter. Device fitted to catch or trap points in a track-circuited area, which ensures the track circuit remains operated if a movement runs through the trap and is derailed completely off the track.
TCOD	Track Circuit Operating Device.
TD	Train Describer. A system that identifies trains and displays their location to the signalman.
TDEU	Train Despatch(er) Enquiry Unit.
TDM	Time Division Multiplex. A protocol for transmission of data.
Tel	See T[ii] above.
Ten Foot	A railwayman's term for the space between two parallel sets of double railway lines.
TEP	Token Exchange Point.
Termination Indicator	A trackside sign indicating the end of a temporary speed restriction.
TES	Train Entering Section.
TFM	Trackside Functional Module.
Theatre Route Indicator	Another name for a multi lamp route indicator.
Three Aspect Signalling	A system of colour light signalling that provides only red, yellow and green aspects.
Three Position Semaphore	Semaphore signal, usually upper quadrant, capable of displaying danger, caution and clear messages to the driver.
Through The Road	Signalman's term for a train movement through a crossover between the Up and Down lines, the "road" here being interpreted as the entire double track, rather than a single "Up Road" or "Down Road".
TIN	Technical Incident. Train stopped for 3 or more minutes due to train fault.
TM	Traffic Management.
TMO	Trainman Manually Operated / Train Crew Operated.
TMOB	Trainman Operated Barriers.
TMOG	Trainman Operated Gates.
TMP	Traffic Management Partner.
TMR	Train Movements Room. London Underground.
TMS	Train Management System.
Toe	The front end of a switch rail
Token	The authority handed by the signalman to the driver as permission to proceed onto a single line. Traditionally a physical object but modern systems can create electronic ones.
TOL	Train on Line. The state of the block section with a train present between the section signal of one signal box and the clearing point of the next signal box.
Tommy Dodd	Railwayman's jargon term for a Ground Signal. Used by staff of Great Eastern Railway and London & North Western Railway; possibly others as well.
TOPS	Total Operations Processing System.
TORR	Train Operated Route Release. A method of releasing a route after the passage of a train without action from the signalman.
TOS	Train Out of Section.
Toton Signal	An indicator for controlling loading or unloading movements and also for controlling shunt movements over the hump of an automated marshalling yard.
TP Hut	Track Paralleling Hut. Trackside building with remotely-controlled switchgear to enable adjacent sections of conductor rail to be connected together or disconnected, to adjust power feeding conditions in emergency. Normally located between substations.
TPT	Train Positioning and Tracking.
TPWS	Train Protection & Warning System. System designed to ensure that drivers reduce speed appropriately when approaching lines subject to a speed restriction or terminal platforms.
TPWS+	Train Protection & Warning System. System designed to ensure that drivers reduce speed appropriately when approaching lines subject to a speed restriction or terminal platforms on sections of line where the line speed is higher than 70mph.
Track Circuit Operating Clip	An emergency device that can be clipped across the running rails in order to short circuit the track circuit thus restoring the signal in rear to danger.
Tracker Ball	A device that enables a signalman to enter data and to control points and signals in an IECC or computerised signalling system.
Trailable Points	A set of points that can be traversed in the trailing direction without the need to have the point blades correspond with the direction of the movement. Common place in shunting yards where points are controlled by ground staff.
Trailing Points	The term applied to points where lines converge.
Train Description	An alphanumeric identity unique to each train in a defined area within a defined period of time.
Train Staff	Physical object handed to the driver of a train where Train Staff block working is in force as authority to proceeed over the section of single line named on the staff. If another train is to follow in the same direction the driver may be handed a Ticket instead and must be shown the Staff as support for the issue of the Ticket.
Trainstop	A trackside device that initiates the brakes of a train that passes the associated signal when it is displaying a stop aspect.
Transponder	Equipment fixed adjacent to or between the running rails to pass information to and from a train by electronic means.
Trap Points	Facing points provided for the purpose of derailing an unauthorised movement in order to protect an adjacent line.
TRC	Train Running Controller.
Trigger Loop	Part of TPWS track equipment nearer to a signal, which activates the on-train equipment if the train is travelling too fast.
TRB	Train Register Book. A book kept in a signalbox to record train movements
Treadle	A mechanical or electrical device to detect the presence or absence of a train at a specific point.
TRTS	Train Ready to Start Indicator. An indicator in the signalbox, operated from a plunger on the station platform, to advise the signalman that the train is ready to depart.
TRUST	[i] Train Running and Statistics. The original definition when it was first created and introduced in the 1980s. [ii] Train Running System (TOPS). The definition currently used by Network Rail.
TS	Train Staff.
TS&T	Train Staff and Ticket Working. A signalling system used on single lines where the permission to proceed can be either the handing of the staff to the driver or the issue of written permission accompanied by display by the signalman of the staff to the driver in the event of there being one or more following trains to pass in the same direction.
TSR	Temporary Speed Restriction. A speed restriction imposed for a short period of time, usually for engineering work but occasionally because of deferred renewals.
TSS	Train Service Specialist.
Turn In	A train is said to be "turned in" when diverted from a main line to a goods loop, relief or similar subsidiary line, often to enable a faster train to overtake it.
Turn Out	The opposite of Turn In: a train is "turned out" on to the main line from a subsidiary line when circumstances allow.
TVSC	Thames Valley Signalling Centre. Located at Didcot.
Turnout	Alternative name for a set of points.
Two Aspect Signalling	A colour light signalling system using red / green two aspect stop signals only. Yellow / green repeater signals are provided where sighting distance is inadequate.
Two Holes	A note found on signalling diagrams at points fitted with a Facing Point Lock, indicating that there are two ports (notches) cut in the lock stretcher bar. Thus the FPL can lock the points in either of the two possible positions. Also expressed as "Locks..." or "Bolts Both Ways".
TWT	Train Waiting Treadle. Treadle to warn the signalman of the arrival of a train at his home signal, especially if it cannot be seen from the box.
U
UB	Under Bridge. Bridge allowing non-rail access across the line beneath the railway.
UEL	Up Electric Line. Running line in the up direction equipped for electric trains.
UFL	Up Fast Line. Running line in the up direction.
UG	Up Goods Line. Running line in the up direction.
UGL	[i] Up Goods Line. Running line in the up direction. Before the advent of large area power signal boxes, where extrance and exit were controlled by different signal boxes. [ii] Up Goods Loop. Running line in the up direction. Before the advent of large area power signal boxes, where extrance and exit were controlled by the same signal box.
UM	Up Main Line. Running line in the up direction.
Unpeg	The act of removing the pin holding the handle of a block instrument so that it would return to the central position and show the "Normal" indication.
Under the Hammer	A train accepted under the warning arrangement (Block Telegraph Regulation No.5), when the section ahead is clear but the station or junction at the far end is blocked, can be said to be "under the hammer". From the distinctive hammer-shaped semaphore arms used on the former Midland Railway for Warning Signals.
Unworked Points	Points that lie whichever way the last movement in the trailing direction left them.
Up	A direction applied to a running route.
UPL	[i] Up Passenger Line. Running line in the up direction. [ii] Up Passenger Loop. Running line in the up direction.
Upper Quadrant	Semaphore signal that inclines upward from the horizontal by 45 degrees when giving a proceed or caution message to a driver.
URL	Up Relief Line.
URS	Up Refuge Siding.
UTX	Under Track Crossing.
UWB	Crossing with User Worked Barriers.
UWC	User Worked Crossing.
UWG	User Worked Gates. Public road level crossing with gates worked by the road user.
UWW	User Worked Wicket Gates. Public level crossing with wicket gates that can be locked by the signaller.
V
VDU	Visual Display Unit. A screen on which information is displayed by electronic means.
W
Warning Arrangement	A method of signalling a movement towards a signal with a reduced overlap.
Warning Board	A lineside sign placed at sufficient distance from a temporary or emergency speed restriction to permit a reduction of speed.
Warning Indicator	A lineside sign placed at sufficient distance from a permanent speed restriction to permit a reduction of speed.
Warning [Route Class]	A route from one main signal to the next where the full overlap is not available or required.
Warning Signal	Subsidiary semaphore signal which authorises non-passenger trains to pass the section signal at Danger, under the terms of Block Telegraph Regulation 5, the Warning Arrangement. A driver understands that if his train receives the Warning signal, the section ahead is clear, but that the station or junction ahead is blocked. Thus he is "warned" that there is no overlap available at the next stop signal ahead.
WCML	West Coast Main Line.
Welwyn Control	A means, in block signalling, of preventing the acceptance of a second train before the first train has occupied and cleared the home signal berth track circuit. Name harks back to the accident at Welwyn Garden City in 1935 which led to its introduction.
Welwyn Winder	Small instrument, found in several forms, fitted on the block shelf. If a signalman has to unlock equipment, e.g. due to a route having been set but the train then cancelled, this device forces him to spend time winding a handle, and hopefully reflecting on what he is doing, rather than rushing into a dangerous move. Part of the overall "Welwyn Control" equipment.
WEN	Weekly Engineering Notice.
WFB	Weighted Fouling Bar.
Wheel Stop	See Scotch Block.
Whistle Board	Lineside reminder to the driver of the train to sound the whistle, mostly for a level crossing.
White Diamond	Unofficial name for a Rule 55 exemption sign.
Wickets	Small pedestrian gates at a level crossing, which can be locked from the signalbox, but have no connection themselves with the signal interlocking.
Wigwag	Alternating red flashing lights facing road traffic at a level crossing. Early versions omitted the amber warning light.
Wire Adjuster	Equipment in a mechanical signalbox for ensuring that the operating wire for a signal is maintained in a constant state of tension through the normal ambient temperature range.
WON	Weekly Operating Notice.
Working Book	[i] Alternative name for Working Timetable. [ii] Extracts from the working timetable for a specific location - e.g. Station Working Book or Yard WOrking Book.
Wrong Direction	Opposite to the normal direction of traffic on a particular line.
Wrong Side Failure	A failure that results in the protection provided by the signalling system being reduced.
WS	Work Station. VDU.
WTT	Working Timetable. The version of the timetable used by railway staff containing operational information regarding all trains over a section of railway. Usually split into separate books for passenger & parcels and freight traffics but other splits have been used over the years.
X
-X	Added to description of a level crossing that works automatically for wrong direction moves.
Y
Y	[i] In signal engineering documentation, relating to a colour light signal, means the yellow (Caution) aspect. [ii] In signal engineering documentation, relating to a ground signal, abbreviation meaning it has a yellow arm (mechanical) or yellow normal indication (position light), and may be passed when in the “on” position by movements in a direction to which it does not apply.
Yellow [Aspect]	Displayed by a colour light signal informing the driver to expect the next signal at red.

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