Glossary of Terms


Lantern Collection 
Lamps Collection 
Glossary of terms 
Brackets Collection 
Gear Collection 
Switching Devices 

Aero-screened lanterns. Lanterns which have been modified with a specially designed shuttering fitted to the bowl to reduce side glare from the lamp, where, for instance, stray light rays could affect aircraft operations in and around airports. (See also cut-off lanterns).

Arc light. An intense white light produced by connecting two carbon electrodes to an electric power supply. The electrodes become white-hot when they are momentarily brought in contact at their tips and then withdrawn from each other, a luminous electric arc develops across the gap. The relatively high resistance to electric current in the gap causes the electrode tips to heat to incandescence and emit a brilliant light. The principle was first demonstrated by Sir Humphrey Davy in 1802. For more information on arc lamps visit:

Arc tube. A sealed quartz glass tube found inside HPMV, HPS, and MH discharge lamps, where an electric arc is created between two electrodes, heating the gases inside the high pressurised arc tube and creating an intense white light.

Asbestos. Fibrous, heat resistant material (normally off-white in colour) that used to be used extensively in the electrical industry, but has been banned in the UK (and most other countries) for many years because it is proven to be carcinogenic. Asbestos was once used in the manufacture of streetlighting and can still be found in old lanterns where it was used as a heat insulator for wiring situated close to the heat of the lamp. It was also used in braided rope form as a door seal on some lantern bowl-rings and on older control-box doors. The main danger is from old crumbling Asbestos where particles of dust from disturbed asbestos can easily be breathed in if care is not taken. Protective clothing, gloves, and facemasks should always be worn when handling this material. Old asbestos needs to be disposed of properly, and is normally destroyed by specialist companies in high temperature furnaces designed for its disposal. Always seek advice if you come across this material, and leave well alone if you're unsure, or not properly protected.

Back-Boards. Wooden boards usually found inside the bases of columns, or the back of control boxes, onto which the control gear and cut-out is mounted.

BC (bayonet cap). Widely used method of fixing the lamp into the lampholder (BC cap lamps) by means of a ‘push and twist’ spring loaded locking device within the lampholder that secures the lamp by its two-pin lugs. 22mm is the standard BC size used in commercial fittings in the UK, although 15mm BC caps are sometimes used in some domestic light fittings.

BC-3 (3-pin bayonet cap). Similar in size and shape to the normal BC lamps and lampholders holders, but designed with a set of three-pin locators, instead of the two-pin locators found on normal BC cap lamps. The off-set pins also ensure that the lamp cannot be fixed into the lampholder the wrong way around. 80-watt and 125-watt MBF lamps normally use 3-BC caps.

Blended Mercury lamps. Sometimes called self-ballasting lamps, these are mercury lamps that require no external ballast, but instead use an internal tungsten filament that acts as ballast; the MBFT mercury lamp is an example of such a lamp.

Bowl. The translucent part of the lantern which surrounds the lamp. Bowls were at one time made exclusively from glass, but these days are normally made from polycarbonate plastic. Bowls used to rely on a prismatic surface built into them to refract the light from the lamp, directing and concentrating the light in the required direction. However, modern high-pressure sodium, and metal-halide lanterns tend to use clear plastic bowls, instead relying on the silver reflector dish mounted above the lamp to direct the light.

Bowl Ring. Usually an aluminium or non-ferrous metal ring into which the lanterns bowl is fixed; the ring effectively secures the bowl to the lantern's canopy. Bowl-rings are normally found in older type lanterns, and especially those that used glass bowls.

Bracket, bracket arm (aka 'out reaches'). The metal, or concrete arm mounted on to the top of the column that supports the lantern. In cases where the bracket arm is very long, a tie-bar, or stay-bar is sometimes used to support the weight of the bracket.

BSP. 'British Standard Pipe'. These were the old British Imperial thread profiles used on lanterns that employed a screwed bracket mounting. The BSP threads commonly used were 3/4"BSP, 1"BSP, or 1 1/4" BSP threads, dependent on the size of the lantern, and the size of the bracket on to which the lantern would be attached. The measurement across the diameter of the thread was always greater than the stated thread size, as the thread size actually referred to the bore of the tube and not the outside diameter of the thread, that is, a 3'4" BSP thread would be used on a tube with a 3/4" bore running through it.

Canopy. The metal or GRP upper body of top-entry and side-entry lanterns, and the part of the lantern to which the bracket is fixed into.  

Cap. Cylindrical metal fixing at the base of a lamp (bulb), by which the lamp is fitted into the lampholder (see also BC Bayonet caps and Capacitors). For more information on caps:

Capacitors (sometimes referred to as a ‘cap’ or 'caps'). These are electrical devices used in the control gear circuit to 'smooth' the current, improving current consumption and the life of the discharge lamp and control gear. The type normally used in streetlighting are PFC (Power Factor Correction) capacitors.

Carbon Arc lighting. The earliest form of electrical discharge lighting, where an electrical arc was generated between two consumable carbon rods, resulting in a very intense light being created, similar to that of an electric welder. The very first electric streetlighting installation in the UK to use this method of illumination was along the Thames Embankment, London, in 1860's.

CDM-T, lamps. Philips brand of Metal halide lamps made in various wattages. Metal halide lamps give out an intense white light.

Cherry-Picker. Name given to vehicles with a platform mounted onto a hydraulic arm to facilitate overhead access and repairs.

Chokes, Leak Transformers, and Ballast units. Devices that stabilise the arc current in a discharge lamp after the initial starting up of the lamp. After the lamp 'strikes-up', the Ballast stabilises the current to a safe level preventing the destruction of the lamp during running.  If there were no ballast and the electrical discharge in the lamp was not controlled and balanced, the initial high voltage to create the arc within the lamp to start it would destroy the lamp almost instantly. See Control gear.

Cold Cathode lighting. Early form of fluorescent discharge tube made in the 1950's and early 60's for commercial and domestic use that has been long discontinued by lighting manufacturers.

Columns. The lamppost uprights. From their introduction in the 19th Century through to the 1940’s, streetlighting columns were generally made from cast iron and were very ornate affairs. In the post war years and through to the 70’s, pre-stressed concrete columns became popular, but over time they proved to have a poor road safety record in respect to Road Traffic Accidents; these days there is a concerted effort by most councils to replace them where possible. Other materials have also been used such as aluminium and even fibre-glass. The majority of today’s streetlighting columns are usually made from galvanised steel tubing, or fabricated steel sectional tubing (octagonal in section, wide at the base, and tapering to a narrow section at the top of the column where the bracket is attached). Modern columns are much more likely to collapse on impact, lessening the injuries to the occupants of vehicles that collide with them. Much research is currently going on to further improve the materials used in, and design of, lighting columns for road safety purposes. 

Compact fluorescent or CFL. Low pressure, single ended  fluorescent lamps, ie with only one end cap.

Contractors (lighting). Private companies who carry out streetlighting maintenance and renewal work often on the behalf of local authorities.

Control Boxes. Weather proof metal boxes (newer types can be made of plastic) into which the lantern's control gear is mounted. Control boxes are used where there is no dedicated lamppost column; e.g.  where lanterns are mounted on the sides of buildings, or on telegraph poles. Rural areas are probably the best places to see control boxes in widespread use.

Control Gear. Sometimes referred to as Gear, this is the description given to the electrical apparatus in its entirety that works the discharge lamp in the lantern, for example, Ballast + Capacitor + ignitor. The control gear is needed to strike the lamp and stabilise and smooth the current flowing through the lamp. The control gear is normally either mounted in the base of the column, or away from the lantern in a control box (remote geared), or incorporated into the lantern itself (geared or gear-in-head). Take a look at this control gear for 80w MBF lamps mounted on to a test board.

Control switch. The remote switching unit used with two-part photocells to switch the lantern on and off, when the photocell detects changing  light levels.  

REC's, Regional Electricity Companies. The utility companys that provide the electricity supply and maintain the electric feeder cables to streetlighting, properties and industry in general.

Cut-off lanterns. Refers to certain types of lantern that through their design do not allow light emitted from the lamp to rise above the horizontal of the lantern's aperture, but instead concentrate the light downward on to the surface below. Cut-off lanterns are to be found where there are level crossings, railway bridges, and close to airports where stray light from the lanterns could affect rail or aircraft operations. See also Aero-screened lanterns.

Cutout or cut-out switch. Also know as a circuit breaker, this is an electrical safety device that will 'trip-out' and break the electrical power supply if a fault or power surge occurs. Once the fault is rectified, the cutout switch can be re-set. Here's a picture of a cut out device in an old Stanton column. In this instance the lamp's control-gear is situated in the lantern, and is not present in the base of the column.

Cycling. A term used to describe the flashing on and off of a failing discharge lamp.

Discharge lamps. Low-pressure sodium, high-pressure sodium, mercury, and fluorescent are all types of discharge lamps, and normally require electrical control gear to operate them. Discharge lamps are far more efficient to run than conventional tungsten lamps and generally have a much longer lamp life.

Discharge Tube. The discharge tube is a gas filled pressurised glass vessel found inside low-pressure sodium discharge lamps. An electric arc is created between two electrodes situated within either end of the tube that heats the sodium-metallic gas sealed within the pressurised discharge tube; this creates an intense 'yellow' monochromatic light.  Take a look at the discharge tube working in this 90w sodium lantern.

Electronic Ballasts. High frequency electronic ballasts are beginning to be more widely used in the lighting industry, as they don't require the addition of ignitors or capacitors to operate the lamp. The operation of these ballasts is such that the lamp gets a smoother 'start up' and running is more economic, leading to considerably extended lamp life. In certain circumstances, a 'dimming' circuit can be also incorporated, which will allow the discharge lamp to be run at a lower power settings if desired; this is only possible with electronic ballasts.

Enclosed Lantern. One where the lamp (bulb) is totally enclosed within the lantern by a translucent glass or plastic bowl.

ES (Edison Screw lampholder). Threaded caps are fitted to some lamps where the lamp is fixed into the lampholder by means of a screw thread. More commonly associated with the USA for domestic use, but also widely used in bigger wattage lamps in the UK. Screwed lampholders come in various sizes E27, E40, etc; where the 'E' stands for Edison-screw, and the number refers to the diameter of the threaded cap in millimetres.

Finial. Ornate end of old cast iron brackets where a top-entry lantern is attached to the bracket. Can also be the ornate top cap sometimes seen in the tops of old or reproduction metal columns that have stay-bar brackets and no out reach mounted on the top of the column.

Fluorescent lighting.  Low-pressure discharge lighting that dates back to the 1950's and that once saw extensive usage for main road lighting up until the late 1960's. Although commonly found in domestic use these days, fluorescent lighting is seeing a come back in streetlighting in the form of Compact-Fluorescent lighting, for illuminating side roads and pedestrian areas.

Fuse. Deliberate weak link in an electrical circuit that will fail if over-loaded, thus protecting the user and also the electrical circuit and its components . Fuses come in two basic forms: 1. fuse wire held in a heat-resistant holder or 2. as a cartridge fuse, where the fuse is enclosed in a sealed heat-resistant container. The downside of using fuses is that they always have to be replaced if they are 'blown'. Although widely used years ago, fuses are not generally used in modern-day streetlighting, but have been replaced with 'cut-outs' (circuit-breakers). See Cutouts.

Fuse box. Weather-proof box in which the fuses or cut-outs are mounted.

G12. Type of ceramic lamp holder for two-pin lamps that operate at very high temperatures, such as for halogen lamps.

Gear-Tray. A formed metal plate mounted inside 'geared' lanterns on to which the control-gear is mounted.

GLS. ‘General Lamp Shape’. Normal shape of a standard tungsten light bulb.

GRP. Glass Reinforced Plastic (Fibre-Glass).

Group-A lanterns. A term used by manufacturers years ago that referred to lanterns for use on main roads.

Group-B lanterns. A term used by manufacturers years ago that referred to lanterns for use on minor roads.

Group-switched. Where a group or section of lanterns along the roadway are all controlled by a single master switch.

Hat. The large covers or lids found on old fashioned post top lanterns such as the REVO Solumbra;  confusingly, sometimes referred to as canopies or dust-bin lids!

HPMV. High Pressure Mercury Vapour.

HPS. High Pressure Sodium.

Hockey stick lampposts. Modern tubular lamppost design where the column and bracket are in one; so called because their shape is similar to an up-turned hockey stick.

Ignitors. Electrical devices required to 'strike' the arc up in some types of discharge lamp control gear. To enable this they generate high current to create the initial arc in the arc tube of the lamp. Once the arc is struck the work of the ignitor is done until the next time the lamp is switched on, as the ballast unit will now stabilise and control the arc in the lamp. Some ballast units have ignitors incorporated within them, so do not require an external ignitor.

Incandescent. Normal tungsten filament lamps.

Lamp. Term used in the industry for light bulbs.

Lampholder. The electrical fitting into which lamps (light bulbs) are mounted. Lampholders see long periods of use in streetlighting and are expected to give many years of service before failing, therefore like the lanterns they are fixed into they have to be constructed from tough heat resistant, anti-corrosive materials.  Lampholders for old Incandescent lamps are generally made from brass with ceramic inserts.  Most lampholders for discharge lamps are made from porcelain or ceramic materials to give long-term protection from the intense heat given off these types of lamps.

Lantern. The actual streetlight. There are various types including enclosed, open refractor, open reflector, and directional types. The canopies which house the lampholder and electrics can be made from cast iron, cast aluminium, coated steel, pressed aluminium sheeting, copper, brass, or GRP (Glass Reinforced Plastic).

LPS. Low Pressure Sodium.

MH or Metal Halide. Modern high-pressure discharge lamps that emit intense white light; these lamps are finding increasing use in certain streetlighting applications, but don't yet have the long service life of HPS lamps.

MCF tubes. Low pressure, two-ended linear fluorescent tubes that are no longer used for streetlighting purposes, but are still widely used for domestic, office and shop lighting.

Monochromatic. Single colour of the light spectrum

Open lantern. A  design of lantern where the lamp (bulb) is situated under a protective canopy/reflector, but is exposed to the atmosphere because it is not totally enclosed within a protective bowl below the canopy/reflector.

Open mirror lantern. A design of open lantern, where the reflective surface above the lamp is mirrored.

Out reach. Another term used to describe the bracket on to which the lantern is fixed (see Bracket).

Nipple. All threaded tube connector used for attaching top-entry lanterns to bracket end finials.

NEMA. National Electrical Manufacturers Association (US based organisation)

NEMA Socket. An electrical switching device (normally mounted in to the top of the lantern) and in to which a photocell is fitted; controlling the switching on and off of the lamp. Because the photocell and switch are locked together by means of a bayonet locking sysytem, they are known as one part-photocells.

PCB. Printed Circuit Board.

PCB’s (Polychlorinated biphenyls). Are a group of manufactured organic chemicals that contain 209 individual chlorinated chemicals (known as congeners). Concentrated PCBs are either oily liquids or solids and are generally colourless to light, but can be yellow in colour. They have no known smell or taste. There are no known natural sources of PCBs. Some commercial PCB mixtures are known in the United States by their industrial trade name, Aroclor. PCBs don't burn easily and are good insulating material. They have been used widely as coolants and lubricants in transformers, capacitors, and other electrical equipment. The manufacture of PCBs stopped in the United States in 1977 because of evidence that they build up in the environment and cause harmful health effects and could be potentially carcinogenic. Products containing PCBs are usually old capacitors (UK-pre 1978), old microscope oil, and hydraulic fluids.  Anyone handling old electrical capacitors (especially the old square or oblong types) needs to be very careful and wear protective clothing. If they are showing signs of leakage, damage, or corrosion, they must be disposed of properly.  Take a look at this picture of an old REVO capacitor that is badly corroded and is leaking PCB fluid.

PFI Schemes. Privately Financed Investment Schemes have had a huge impact on the UK's utility industries in recent years. In the case of streetlighting, this is where a local authority hands over control of the design, replacement, and maintenance of streetlighting to private contractors. This usually signals the beginning of massive streetlighting renewal schemes in towns and cities that take on board PFI schemes, and the obliteration of older streetlighting.

Photocells or photoelectric cells are light-sensitive devices used in modern day streetlighting to switch lights on and off automatically, dependent on the surrounding light level.  Photocell control is used in mainly day lit spaces and should incorporate a delay mechanism to prevent it switching when daylight levels change rapidly.  However, there are specially designed Photocells for night use, where the lantern may be required to switch off before daylight hours. (Also see time switches).

Pre-stressed concrete. Method used in the construction of concrete columns, where the reinforcing steel rods within the structure are placed under tension by stretching them between two points while the concrete is poured around them and allowed to set. This makes the structure much stronger and less prone to complete failure if impacted.

Post-Top or column top. Reference to certain types of lanterns that don't require a bracket, but instead fit directly onto the top of the lamppost column. Old Victorian gas lanterns would be an example of a post top fitting.

Prismatic. Word used to describe multi-faceted glass or translucent materials that can deflect and/or defuse light rays.

Reflector. A bright surface normally mounted in the top of the lantern that reflects light from the lamp. This could be a mirrored surface, polished aluminium, or a white painted/enamelled surface, and can sometimes be a multi-directional reflective surface.

Refractor. A prismatic surface in a translucent material, such as glass or clear plastic that breaks up the lamp light and alters its direction and distribution.

Sleeves, over sleeves, sleeving. Sleeves are galvanised fabricated steel 'slip-over' column tops that incorporate a bracket and are used to replace unsafe and crumbling concrete brackets. This is a picture of a sleeved column in Dudley in the West Midlands).

Spigot mounting. A method of fixing the lantern to the bracket, or column, where the tube end of the bracket/column slots into the receptor of the lanterns canopy; the lantern can than be clamped or screwed into position.

Stay-bars. Horizontal mounting brackets made from thick-wall steel tubing that were built-in to concrete columns to support large and heavy fluorescent lanterns.   Also referred to as stay-bars (sometimes call tie-bars) are the steel rods, or steel strip used to support long-reach bracket arms on steel lighting columns.

Self-ballasting lamps. These are discharge lamps that do not require any external control gear to operate them. Instead they use a special filament within the lamp to act as a ballast; the MBTF blended-mercury lamp is an example of such a lamp.

Street furniture. Lampposts, bollards, traffic lights, road signs, etc. are all regarded as street furniture.

Striking the Lamp. A term used to describe the starting up of a discharge lamp.

Swan neck. Name given to brackets that are in a ? shape

Time-switches Electro-mechanical devices that have a time-date-calendar controlled switching arrangement built into them to switch lighting on and off automatically. The calendar mechanism automatically adjusts for the changing 'lighting up times' throughout the year. Most UK time switches are factory set for 52 degrees latitude, but can be adjusted for differing 'lighting up times' in locations to the north or south of this line. Calendar timeswitches are now considered to be an expensive and outdated means of automatic switching, and one that has virtually been phased out in the UK. See Photocells.

Traction Poles. Steel columns that were erected in many British towns and cities from the 1920's through to the 1950's to support the overhead running wires for electric trams and trolleybuses. It was often convenient to attached streetlighting to traction poles to save erecting separate lighting columns and causing unnecessary clutter and expense.

Return to top of page

Copyright(c) 2005 Claire Pendrous. All rights reserved.

Please note that all pictures are by Claire Pendrous, or are part of the Claire Pendrous photographic collection unless otherwise stated; none of these images can be copied without obtaining prior permission.