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glossary

At the moment, this section is very incomplete. In time, I'll add to it - just think of it as private notes that I've made public.



aei : associated electrical industries
Manufacturing company. See AEI.


aple : association of public lighting engineers
Founded in 1924, a body of professionals interested in all manner of public lighting. Their quarterly publication, originally Public Lighing And The Public Lighting Engineer, was founded in 1936. A conference was usually held once per year, where manufacturers were invited to exhibit their latest lamps and lighting equipment.



bc : bayonet cap
Bulbholder where the bulb is inserted by pushing the base against two spring mounted electrodes and then twisting to secure.


bonnet
An older term for 'cover'. Probably named after the hat. It's use is ambigious amongst manufacturers and this probably lead to its use become depreciated. For example, Wardle used it to describe the canopy of a lantern (e.g. it covers the top of the lantern) whilst BLEECO used it to describe a Spigot Cap (e.g. it covers the top of a column).



bracket
Brackets are used to position the lantern in the desired place, usually above the centre of a road or above the kerb. They're normally attached to the top of a column, but brackets are also used to position lanterns away from walls and telegraph poles.

The vast majority of brackets have one arm which supports one lantern. Other examples can have two, three or four arms to support multiple lanterns.

Brackets are often made from the same material as their assoicated column (tubular steel, concrete), although some manufacturers offered metal brackets for concrete columns.

Early examples are highly decorative with scrollwork and finials. By the 1950s, the designs became more austere and functional.

With many early lanterns requiring fixing via the top of their canopy, many brackets are bent and angled. The most familar shape is the swan neck (see left).

A bracket isn't normally required for post-top lanterns. These attach directly to the column.



bs : british standards
The British Standards for lighting are sets of rules and regulations drawn up by the MOT and other government bodies.

They are often revised and updated. The current standards (2003) are:

BS 5489 Part 1: Lighting of roads and public amenity areas.
BS 5489 Part 2: Tunnels.
BS EN 13201 Part 2: Performance requirements.
BS EN 13201 Part 3: Calculation of performance.
BS EN 13201 Part 4: Methods of measuring lighting performance

BS EN 13201 Part 1 will no longer appear as a standard, and will probably appear as a guideline document.


Previous standards were:

  • BS 307/1931: Street Lighting. Published in 1927.

    It specified a test point and minimum illumination values (as foot candle classes):

    ClassMinium IlluminationMinimum Height Of SourceSpacing RecommendedSpacing Height Ratio
    A2.0 foot candles30 feet90 feet3
    B1.0 foot candles25 feet100 feet4
    C0.5 foot candles21 feet105 feet5
    D0.2 foot candles18 feet108 feet6
    E0.1 foot candles15 feet105 feet7
    F0.05 foot candles13 feet104 feet8
    G0.02 foot candles13 feet130 feet10
    H0.01 foot candles13 feet130 feet10

    It allowed a simple way to order and check the work of contractors and give general guidance in the planning of new work.


  • BS 398/1930: ???. Publication date: 1927-1935

    This documented specified the symmetrical light distribution from light fittings. Street lighting was part of the "Direct" class, and not less than 90% of the flux was in the lower hemisphere. The polar curves were divided into five classes:-

    1. Extra Narrow
    2. Narrow
    3. Intermediate
    4. Wide
    5. Extra Wide

    By the 1930s it was realised that both these reports were unsuitable, and had lead to some very highly directional reflectors and refractors giving narrow beams of high intensity, leading to glare and streakiness on the road.

    They set a fashion for high peak intensity.

    They were quickly succeeded by the MOT report in 1937 and subsequently obsoleted.


  • BS 1308: Reinforced Concrete Street Lighting Columns. Published in 1946.


  • BS 1249: Cast Iron Street Lighting Columns. Published in 1951.


  • BS 1788: Street Lighting Lanterns. Published in 1951.

    This document covered the mechanical and constructional features of lanterns, with regard to safety, durability and easy of maintainance.

    It did not cover photometric requirements.


  • BS Code Of Practise (BSCP) 1004 Part One: Street Lighting - Traffic Routes. Published in 1952.

    This refined the MOT Report of 1937 on Group 'A' roads and was supplimented by BS 1788 which was published the previous year.

    The total downward light the now the most important.


  • BS 1840: Tubular Steel Columns for Street Lighting. Published in 1952.


  • BS Code Of Practise (BSCP) 1004 Part Two: Street Lighting - Roads other than Traffic Routes. Published in 1956.

    Light distribution in plan should be suited to environment.



bth : british thomson-houston
Originally a UK branch of the US Thomson-Houston manufacturing company, BTH produced a wide range of lamps and lanterns (under the Madza tradename). BTH's range was ahead of its time, producing designs and utilizing materials which would not become mainstream until years later.

Left: The BTH Urban Enclosed (SM278) - available as both side and top entry.



candela
Measurement of the intensity of light (introduced in 1948 by the International Committee on Weights And Measures). It replaced the Unit Candle.



candle power
???


columns
The vast majority of street lights require a column to position the lantern at the correct height above the road. First used in the 19th century, the first columns were cast-iron ornate affairs, but during the 20th century many other materials were utilized. Concrete became popular in the post-war period when iron and steel were in short supply. Fibre glass, plastic and wood have also been used for columns, but these are the exceptions.

Columns were originally designed to withstand a collision with a car, but health and safety concerns lead to columns which would crumple and bend if hit.

Most original cast iron columns were designed for manually operated gas lanterns, and there was no provision for any gear compartment. When converted to electricity, a high level control box was required, usually mounted on top of the column.



cut-off
Glare is eliminated at all normal angles of sight, but surface brightness is reduced. The maximum intensity is a 70 degrees ot the downward vertical with a negligible amount of light at 80 degrees and above.


davis
One of ELECO's companies, DAVIS produced the popular ex-ELECO range in the late 1980s.

Left: The DAVIS GR100 - originally an ELECO design.



es : edison screw
Threaded bulbholder where the bulb is inserted by screwing it in.


eleco
This manufacturing company produced a highly popular range of lanterns, brackets and columns which were utilised throughout the UK. They were most popular in the 1960s and 1970s and produced some of the most striking designs from that period, whilst also producing some of the most bulbous.

Left: The Eleco Lunar (PT 1006) - an example of a striking design.



elma : electric lamp manufacturers' association of great britain
Cartel formed by the merging of the two principle lamp rings in 1919. They represented 90-95% of the market, fixing prices and regulating output, primarily for the interests of GEC, BTH and Siemens. After government interventions and rulings, ELMA eventually became a trade union. It's assumed that the ring was broken by the Second World War.



esla : the electric street lighting apparatus co.
Manufacturing company based in Canterbury, Kent who are primarily remembered for the ultra-collectable Bi-Multi range of lanterns.


finial
Fitting at the top of a bracket. Can be purely decorative (such as a Fleur-De-Lis at the tip of a curved bracket) or is functional i.e. supporting a top-entry lantern.


foot candle
Old method of measuring illumination. Superceeded by the Candela.


frog
Spindly metal construction connecting post-top gas lanterns to columns.


ges : goliath edison screw
Threaded bulbholder where the bulb is inserted by screwing it in. These are used for larger wattage bulbs, typically 250W to 400W high pressure mercury.


gls : general lighting source
The classification of incandescent light sources.

The first incandescent bulbs used carbon filaments in a vacuum; these were then replaced by tungsten filaments in a vaccum; to be finally superceeded by gas filed tungsten filament bulbs. (An inert gas was pumped into the bulb to slow down the loss of tungsten atoms from the filament).

The original bulbs used a coiled filament, whilst coiled coil tungsten filament lamps started appearing in the 1930s: these became the standard. Old 1930s open GLS lanterns (such as ESLA Bi-Multis or BLEECO open dome refractor lanterns) should be fitted with clear single coil bulbs.

Typical wattages are: 40W, 60W, 75W, 100W and 150W (for Group B roads); 200, 300, 500 and 1000W (for Group A roads).

Variations of the GLS source are:

Clear Lamps: These are clear glass bulbs.

Pearl Lamps: Are the most common types of incandescent lamp. These are internally etched to produce a diffusing finish and usually have a grey unlit appearance.

Opal Lamps: Are less common, being sprayed inside with a diffusing coating. They have a white unlit appearance (similar to a coated elliptical MBF or SON).



glare
In the 1930s, it was believed this was governed by three factors:
  1. The brightness of the lamps.
  2. Position relative to the observer.
  3. A factor which takes account of the relative movement of observer and lamp.
Directing light at one degree below the horizontal was seen to be adventageous in the 1930s, but a cause of glare. Some authors suggested ways to minimalise it, even suggesting graduated filters along the top of car windscreens.



gs
Gas Filled. A term from the 1930s to describe the new gas filled tungsten filament lamps. Before then, the filament was held in a vacuum. Keeping the filament in an inert gas filled environment slowed the evaporation of tungsten from the white hot filament.

This became the standard.



globe
Glass bowl enclosing a lamp. An early term for bowl. Used to protect the lamps, and provide an early form of light control (either through reflection from the upper part of the globe and/or diffusion from its opaled surface).

When bowl became the preferred term, globe was used to describe spherical, decorative glass or plastic bowls for street lights.



lantern
Assembly to redirect light as desired, and to protect the light source. Now superceeded by 'luminaire'.



lantern body
The body of the lantern can be made in the following ways:

  1. Spinning
    1. Steel
    2. Copper
  2. Fabricated Box
  3. Casting
    1. Iron
    2. Silicon Aluminium
      1. Gravity Die
      2. Pressure Die
    3. Plastic Moulding


light control
This is the method of directing light flux from a light source in designated directions. Various technologies, and combinations of those technologies, are used in a lantern:

  1. Reflector
    1. Vitreous Enamel
    2. Glass Or Plastics
      1. Silvered
      2. Aluminised
      3. Prismatic
    3. Anodised Aluminium
  2. Reflector-Refractor
  3. Refractor
    1. Single Piece
    2. Sealed Two Piece
    3. Glass
      1. Soda-Lime
      2. Heat Resisting
    4. Plastic
      1. Processed Sheets
      2. Injection Moulding
  4. Diffuser


light source
The source of light from a street lighing lantern can be produced by a number of different technologies.

  1. Incandescent Filament (GLS)
  2. Discharage Lamp
    1. Low pressure sodium (SO/H)
    2. Mercury
      1. Discharge MA/V, MA/H, MB/U
      2. Blended MBT/V
      3. Bulb Fluorescent MBF/U
      4. Tubular Fluorescent MCF/U
  3. Gas
    1. Low pressure
    2. High pressure
  4. Arc Lamp


lighting types
The spread of light from a lantern is characterised in the following ways.

  1. Prestige And Display
  2. BS Code Of Practise
    1. Group A
      1. High Angle
      2. Medium Angle (including Aeroscreened)
      3. Cut-Off
      4. Uni-Directional
    2. Group B
      1. Narrow B1
      2. Wide B2
      3. Tree Lined


ma : mercury medium pressure
The designation of the first commercial mercury discharge lamps. Invented by the GEC in 1932, the first installation was erected in East Lane, Wembley in 1932. Consisting of 400W Osira lamps in clear glass globes, the second installation in the newly designed Z8001 was installed in Wembley Way later that year.

400W bulbs were first available, quickly followed by 250W units. A 150W version was launched in 1936, but, due to the medium pressure of the mercury vapour, suffered from efficacy problems. Therefore the race was on to develop a high pressure version of the bulb which could operate well at lower wattages.

The orientation of lamp burning was also important, and several designations were used:
/V Vertical cap up
/D Vertical cap down
/H Horizonal
/U Universal

Mazda (BTH) sold the lanterns under their Mercra name. The GEC could only use the Osram name for tungsten filament lamps, so sold their mercury lanterns as Osira up until the second world war. Philips used Philora, whilst Siemens used Sieray.

Siemens were advertising the Sieray-Dual Lamp in 1936 as a combination of mercury discharge lamp and tungsten filament. The light quality was considered better from this bulb, and it didn't require any gear (the tungsten filament acting as ballast with its fixed resistance). The designation for this bulb became MAT and was also known as Blended Mercury.

There were a couple of variants (which extended the lamp's code):
T With a tungsten filament. See above.
F Coated with a fluorescent power to improve the light quality.
Watt Rating. Lumen Output. Average Life.
250 9000 1,500 hours
400 18000 1,500 hours



mantle
???


methods of control
This breaks down how a street light is switched on and off.

  1. Hand operated (both individual and group)
  2. Time clock operated (both individual and group)
  3. Centralised control using high frequency impulse or DC Bias.
  4. Contactors in cascade.


mot : ministry of transport
The government department in the UK responsible for the transport infrastructure. They're write the guidelines and rules governing street lighting.

They published their first report in 1937 (with an interim report in 1935 which covered main roads only) which superceeded and obsoleted the British Standards 307 report of 1927. The amount of light from a lantern was just one criterion (it was the principle subject of BS 307). Definite spacial arrangements of lanterns in terms of height and distance were standardized, and there were limits placed on the peak intensity of the beam, leading to improvements of glare. It was also the first document to divide roads into Group 'A' and Group 'B'.



non cut-off
Maximum intensities are directed at angles close to the horizontal. This type of lighting will be accompanied by a certain amount of glare. The maximum intensity is at 80 degrees ot the downward vertical, with no limitation on the amount of light at higher angles.


optical systems
The optical systems utilitised by street lighting lanterns include:

  1. Symmetrical
  2. Axial Asymmetric
  3. Non-Axial Asymmetric
  4. Uni-Directional


optikon
Physical embodiment of the various reflecting or refracting devices in a lantern. Therefore a lantern consists of a canopy (or boyd) and an optikon. Used by the GEC in the 1950s.


photo cell
Early versions, known as Light Actuated Switch, used a selenium cell and a single valve amplifier unit. By the 1930s, a new circuit was employed, which didn't require a valve. It was known commercially as the Radiovisor Bridge.



public lighting : public lighting and public lighting engineer
The official publication of the APLE. Founded in 1936 and published quarterly.



radio interference
This was found to be caused by some types of street lighting in the 1950s. The solution was to connect a 0.01 microfarad capacator (for 80W) or a 0.1 microfarad capacator (for 400W) across the terminals of the bulb.


raising/lowering gear
Pulleys and wires allowing lanterns to be raised and lowered. Advantages and disadvantages are:

  1. Low labour costs for maintainance.
  2. Lanterns more easily cleaned on the ground.
  3. Maintenance can be effected without causing a traffic obstruction.
  4. Elimination of risk of accidents with tower wagons.
  5. However... installation costs more and additional equipment needs maintaining.
  6. Jarring and shock can cause filament or bulb failure.


sinusoidal diagram
Introduced in 1932 as a measure of the utilisation of a lantern. When "Iso-Candle" lines are plotted on it, it becomes known as an "Iso-Candle Diagram."


so : sodium, one cap or base
Designation of the first sodium lamps, invented by Philips in 1932. The first trial installation was along a road in Eindhoven, Holland (see below). At first the authorities were hesitant about the colour of the lamp and dared not use it. But Dr. A. F. Philips agreed to install the trial installation, and if it wasn't pleasing, Philips would take it down, paying all costs.

At first, there was much laughter about the "queer yellow lamps" but motorists soon realised their benefits (good visibility, less glare, better performance in fog). Therefore the trial installation was kept.

The first installation in the UK was in Purley Way, Croydon, outside the airfield, also in 1932 (see below). This was probably prompted by the successful trial of the GEC's MA discharge lamp in East Lane, Wembley, early in the year.

It appeared that this first installation (100W DC) was installed in bucket-type cut-off lanterns. It lasted four years before being replaced with a larger installation of Wardle Liverpools on a catenary system, which lasted until the 1970s.

The bulb was typified by a two piece construction - the inner arc tube was enclosed in an outer tube which comprised a Dewar flask. When the inner tube was spent, it was removed and replaced - the outer tube, which was expensive to construct, was retained.

The Dewar vacuum chamber provided thermal insulation, allowing the inner tube to reach its optimum temperature of 260oC.

The original wattages and efficiencies were:

Watt Rating. Total Nominal Lumens.
50 2550
70 (later 65) 3780
100 6100
150 9600

Philips sold the bulb under the Philora name - technical information can be found here.

On the 15th Novemebr, 1938, ELMA reclassified the wattage and efficiencies as follows:

Watt Rating. Total Nominal Lumens. Initial Nominal Efficiency.
Lumens/Watt.
Nominal Average Efficiency thoughout life
Lumens/Watt.
45 2500 55.5 42
60 3900 65.0 49
85 6100 71.5 57
140 10000 71.5 57

By the early 1960s, the efficiencies of the lamps had improved:

Watt Rating. Inital Lamp lumens. Average output throughout life.
85 6200 5525
140 10250 9100

The orientation of lamp burning was also important, and several designations were used:
/V Vertical cap up
/D Vertical cap down
/H Horizonal
/U Universal



solid state energy saver
A low loss low pressure sodium ballast incorporating both a choke and a thyristor. These devices were marketed by DAVIS in the late 1980s, and a data sheet can be found here.


spigot
The top of the column, which has a smaller radius, and allows a bracket with Spigot Cap to be fitted onto it.


spigot cap
Screwed to the base of a bracket, it allows the bracket to be secured to the top of the column by means of three or four bolts. It fits onto the Spigot.


thyractor
A marketing name by DAVIS, the thyractor was a combination of a low loss choke (the reactor) and a thyristor. The thyristor was used as an ignitor.

Such a device would be used for SOX, SOX Plus and SOX-E.

DAVIS also sold this device as a converter unit from MBF to SON. Chokes can be connected in series, so the low loss choke decreased the wattage by a set amount (from 80W for MBF to 70W for SON for instance) and the thyristor acted as an ignitor.

A data sheet for these devices can be found here



unit candle
Obsolete measurement of the intensity of light (replaced by the Candela).


utilisation
The percentage of light available which is incident upon the surface to be illuminated.