Index

Lights and electronics

    General info

    The flaming touch and the campfire probably constituted early man's first use of 'artificial' lighting. Prehistoric man, used primitive lamps to illuminate his cave. Nowadays the electrical lighting is the most commonly used form of artificial lighting. The history of electrical lighting is long. In 1809, SIR HUMPHREY DAVY first demonstrated the electric carbon arc at the Royal Institution in London. The electric arc was also used for lighting at the Paris Opera. The principal of the electric arc is still used today by many older followspots and film projectors, used in entertainment facilities around the world. In 1877 Thomas Edison became interested and experimented with electric lighting. On October 15, 1878, the Edison Electric Light Company was incorporated. Edison patented more than 1000 inventions. Besides the incandescent lamp, Edison is given credit for inventing a system of electric generation. Although Edison did not invent the electric filament lamp, he did however turn theory into practicable form and was one of the first to successfully market incandescent lighting. Edison's first successful lamp used carbonized cotton thread as a filament, installed in a glass bulb, with all air evacuated. In 1880 Edison experimented with other materials for filaments, including wood, grasses, hair and bamboo. Of the over 6000 specimens tested by his laboratory, bamboo, became commonly used for filaments. In 1880, on January 17, Patent number 223,898 was issued to Edison for the T.A. Edison Electric Lamp. After the introduction of the tungsten filament, the next highly significant step in the development of the incandescent lamp, came in 1913 when the first gas-filled lamp was produced. Coiled filament gas-filled lamps in 500, 750 and 1000 watt sizes were introduced in 1913. They gave a much better light at higher efficiency with the same life as former lamps. Nitrogen gas was used in the first lamps but argon was substituted in 1914. Nowadays artificial illumination consumes more than 25% of electricity generated over the world. There are several trends in energy saving technologies for lighting industry. The first is implementation new lamps such as fluorescent, mercury, sodium, metal halide, halogen lamps. The second is associated with electronic circuit design for such lamps.

      Outside lighting information

      • Light Pollution Information - Light can pollute the outdoor environment and wash away the view of stars in the sky. This curable problem and can be prevented through the application of well designed and applied outdoor lighting.    Rate this link
      • The Dark Side of Light - Although light pollution?s impact on stargazing is as clear as day, its effects on other environmental elements are just coming into focus. The evidence shows that artificial lighting has dire consequences for animal behavior, particularly on the ability to navigate at night.    Rate this link

      Home and workplace lighting info

      The majority of all indoor and outdoor lighting in the home today is provided by incandescent lamps, commonly referred to as conventional "light bulbs". The light bulb is the most widely used lamp in residential and many commercial and industrial lighting applications for general lighting. Halogen lamps are a type of incandescent lamp that gives "whiter" light, lasts longer, is usually small, is slightly more efficient than normal bulb and costs more.Halogen lamps are best suited for lighting areas where a direct focus of light is required.

      Linear Fluorescent Tubes are the most common source of lighting in commercial facilities and can be found in many homes.Compact Fluorescent Lamps (CFL's) are of the same technology as linear tubes, but much smaller. CFLs operate with a ballast and a screw base adapter to accommodate their use in many indoor and outdoor applications. Typically, a 25 watt fluorescent lamp is supposed to give offas much light as a 100 watt incandescent bulb. Those power rating are about right, if you wait about 1 minute for the fluorescent to comeup to full brightness. When installing compact fluorescent bulbs, be sure that they do not heat too much inside the la,p. It is possible for those to fail due to excessive temperature. They don't need to reach the temperatures produced by incandescent lamps to fail after a month or two. Compact fluorescents are great, get a "name brand" for longer bulb life. Compact florescents should not be used on any circuit which is controlled by scrs or triacs (dimmers, motion detectors, security lights) unless they aredesigned for this purpose.

      Low-voltage halogen lamps are becoming more popular for lightingstores, buildings, hotels, andhouses. The lamps come in different configurations and wattages (typically up to 50W). Typical voltages are 6, 12, and 24V, supplied by a safety isolating transformersthat are usually connected on their primary side directly to themains power line (110 VRMS or 220 VRMS). Most typical voltage used for low voltage halogen lighting is 12V. Most of the time the safety isolating transformer feedingthe lighting circuit is located in the ceiling of the room near the lights itself. In low voltage halogen lighting the most commonly used lamp types are MR 16 lamps. They are Multiple Reflector 2 inch lamps, seen as shop display lamps absolutely everywhere, available in low voltage flavour 12V, needs little transformer beside lamp, and mains voltage 240V flavor usually 50W or 75W and choice of beam angles. The low voltage lamps are typically very bright.

      Note on light bubs and fixture power ratings have necessary meaning. You might wonder why should a mostly-metalic goosneck desk lamp say 60W? What if I put a more powerful bulb in it? 100 watt and 150 watt light bulbs radiate more heat than a 60 watt bulbdoes. More heat creates more damage to the light fixture. When the lighting fixture was designed, it was designed to accept a certain amount of heat andstill work properly over the useful lifetime of the fixture. If a fixture is designed to work properly with a 60 watt lamp in it, that means that theheat radiated by a 60 watt lamp will not destroy the fixture and the fixturewill continue to function over its useful lifetime. If a 150 watt lamp isput into a fixture rated for 60 watt lamps, the fixture will soon bedestroyed by the excessive amout of heat radiated by the 150 watt lamp andmay bread down and be the source of a fire. The designers will likely also have in mind a safe working teperature to the user, ie putting a higher wattage bulb in may raise the temperature of any metalwork on the lamp to a dangerous temperature which could cause burns to unsuspecting little fingers. The same principle applies to other lighting fitures as well. So for safety reasons NEVER exceed the wattage rating for the lamps in the fixture that they are going to go in. If you do, there may be damage, and a danger for a fire hazard! If if you need more light (lumens) from an existing fixture, a compact fluorescent rated at anything less than 60 watts of input power wouldbe ok for 60W rated lighting fixture. Typically, a 25 watt fluorescent lamp is supposed to give off as much light as a 100 watt incandescent bulb but the same amount or less heat than 25W normal light bulb. Another tip on some fixtures is to use a small reflector bulb in the lamp. Not only can you get away with a lower wattage for the same amount of lightdirected to a specific area, but for a given wattege, less heat is transferred back into the lamp. When using reflector lamp be sure to check carefully that the reflector bulb fits to it without blocking the air circulation or causing excessive hat to any place (for example getting to near to some heat sensitive part of fixture).

      Suggested lighting levels (Illuminating Engineering Society (IES) Handbook)
      Area: Approximate Light Level (footcandles)
      Offices: 75
      Conference Rooms: 20-50
      Auditoriums: 20-50
      Kitchens: 50 (avg.)
      Cafeterias: 10-20
      Reception Areas: 25-30
      Drafting Rooms: 100-200
      Corridors/Restrooms: 10-20
      Writing Areas: 20-50
      Doctor's Treatment Areas: 200
      Storage Rooms: 5-50
      Stores (general): 30-100
      Stores (sales displays): 50-150

      The foot-candle is equal to one lumen per square foot and "the difference between the lux and the lumen is that the lux takes into account the area over which the luminous flux is spread. 1000 lumens, concentrated into an area of one square meter, lights up that square meter with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square meters, produces a dimmer illuminance of only 100 lux.

      Wall hangings, retail displays, and trade show exhibits of all kinds can be very effectively lit with track lighting. Track light is a light fixture mounted on and movable along an electrified metal track. Lighting tracks are available in a variety of finishes, shapes, sizes and wattages, and with a variety of light sources and design accents. Track lighting is generally used to provide accent lighting, task lighting, and general lighting in that order. Track lighting is a very flexible lighting system. The individual track fixtures can move along the track, be swiveled or rotated while in a given position, and then aimed in any direction giving you excellent versatility to change your lighting scheme whenever the need arises. Track fixtures are available in line voltage and low voltage with a choice of incandescent, halogen, fluorescent, or metal halide light sources. Track lighting fixtures can offer an opportunity to be creative and make an aesthetic statement. Track lighting may use halogen, incandescent, fluorescent, or metal halide light sources. Track lighting can be used very successfully in any number of locations: hallways, museums, art galleries, trade show exhibits, offices, conference rooms, studies, churches, restaurants, taverns, hotel rooms, and libraries.

      Here are few lighting tips for positioning lamps on some lighting applications:

      • Before deciding on a particular form of lighting, check the bulb types - shapes and wattage which can be used with the selected light, as there are many different types available.
      • Traditional wall lighting is often more often decorative rather than practical. The idea is adding soft lighting to the room through candle shaped bulbs concealed behind parchment shades, they are designed as a feature to look at rather than see or read by.
      • Enclosed fittings are useful in a hall, landing, porch or in a bathroom. Many of these designs are weatherproof and therefore are suitable in a damp bathroom area.
      • Spotlights are very fashionable and versatile as they can send beams in any direction when mounted on adjustable arms. They can be used to illuminate cupboards, desks, pictures, mirrors or seating areas. However care must be taken when positioning a spotlight to avoid dazzle when seen from another angle. This problem is easily overcome when the lighting is high up the wall or on the ceiling.
      • Fluorescent tubes can spread light easily over an area. They do have the advantage of bright lights with minimum heat given off. They are more efficient than filament lights at turning electricity into light and cheaper to run.
      • Fluorescent lighting tubes give off different types of light. The cold, whiter lights are particularly useful in a loft, workshop or shed. In the house do not choose a blue or greenish shade, as they are bad for your eyes if used alone and also can make you look ill. It is better to choose a warmer yellow colour for a softer lighting effect.
      • For creating the accent lighting of objects on a wall, the wall itself, or any vertical surface, position the track fixture so that the light coming from the fixture makes a 30-degree angle with the vertical. If you are trying to illuminate a reflective wall hanging that can produce glare (for example, a framed photograph covered with glass), do not place the track lighting more than 2-3 feet from the wall.
      • For wall washing a non-textured vertical surface mount the track parallel to the wall being lit and about 2 feet to 3 feet from that wall on ceilings up to 9 feet. Mount the track 3 feet to 4 feet from the wall on ceilings between 9 feet and 11 feet high.
      • For wall grazing textured vertical surfaces (such as draperies, stone, or brick) mount the track 6 inches to 12 inches from that wall with the fixtures the same distance apart and aimed downward.
      • Both wall washing and wall grazing are generally best accomplished by using recessed lighting rather than track lighting.
      • Some general lighting can be provided by track fixtures aimed at a wall or by spill light from fixtures used for accent lighting.

      There are also special decorative lights that are mostly designed for decorative purposes and the actual light output is secondary need. Examples of such are christmas light sets. They look nice, but do not give much total light output. The world glows with a colorful light at one time of the year - Christmas. Everywhere you look, Christmas lights sparkle and brighten almost every door step, window, and Christmas tree in very manu countries. Since the 17th Century, people have lit their Christmas trees to sit by its' comforting glow. The history of electrical christmas lights starts from year 1882. At year 1882 Edward Johnson, an associate of Edison's, created the first string of Christmas lights by hand wiring 80 red, white, and blue bulbs together in a string. At year 1895 President Grover Cleveland put lights on the White House Christmas tree. In 1903, the first strings of Christmas lights were sold to the masses. Strings of Christmas lights continue to evolve. Filament light bulbs are losing ground to energy-saving light-emitting-diode (LED) Christmas lights. Nowadays it is hard to imagine Christmas without bright, twinkling lights. Christmas lights are available at indoor and outdoor versions. The indoor versions are typically considerable cheaper and are only ment to be used inside. Outdoor Christmas lights are an excellent way to decorate your house and yard during the holidays. Outdoor lights are designed in such way that they are safe to use outside where enviroment can be from wet rain to freezing cold. The outside lights are designed in such way that they are safe to be on those hard environments and will last years in such enviroment (using indoor lights outside would be an electrical hazard and they would propably fail pretty quicly). Most outdoor christmas lights are based on low voltage bulbs and powered through low voltage transformer (typically 24V AC output). The low operation voltage and electrical isolation (provided by transfrer) from mains voltage provide the safety. There are also high power outside lights hat operate at mains voltage directly, those lights are constructed so that they are comptely waterproof and can withstand outside weather (because mains voltage is on this system be careful when using them, do not touch them when power is on in case insulation has failed on some place of the set).

      Usually it is a good idea to select a light that is double-insulated or that has been wired with an earth conductor. Double-insulated lights will show the double box symbol. Check also the lamp rating is suitable for the enviroment they are ment to work at.

      Architectural lighting

      Architectural lighting, the use of light in buildings, is critical to the performance of everyday activities and to the appreciation of the built environment. Using Architectural Lighting Controls, specific architectural details of an area can be enhanced and almost any effect or mood can be created. By controlling the lighting in an area, different moods can be artificially created for the desired effect, whether it be a relaxing atmosphere or to stimulate a lively response. In restaurants, for example, different scenes may be required to create a suitable atmosphere, depending on the time of day, e.g. brighter lights at breakfast time, but more subdued lighting effects at dinner. Many buildings are used for more than one purpose at different times. This creates the need for versatility & flexibility of a system. With lighting control, the mood of the lighting can be altered to reflect the mood of the activity taking place and create a suitable ambience. For example, a church may wish to change the lighting scene depending on the event which is taking place. Different scenes would be suitable for a funeral compared to a wedding. Offices are benefiting from lighting control systems. Gradually altering the levels of light throughout the day working with external lux levels, perhaps by incorporating daylight sensors maintains optimum light levels and can increase productivity in an office. In retail, lighting can be used to encourage people into shops and draw attention. Special effects can be incorporated to create interesting features.

      Disco lighting

      The first effects in dance hall lighting appeared long before disco's started. In the 1940's it was discovered that if you shine a light on a ball covered with mirrors that you get one beam off every mirror (seen for example in 1942 film Casablanca). When disco's came along in the late sixties and early seventies the mirror ball was the first effect to adopted. Other lighting could be provided by red bulbs or other colored light bulbs. First strobo effects were generated by using a powerful spotlight with a spinning wheel in front of it (this wheel has holes in it). Soon "Ultra Violet", which made white things glow in the dark, was adopted to disco lighting (makes white clothers to shine, even underwear through clothing).

      The first real dedicated disco lights were invented in about 1968 when someone decided to control lighting using electronics. The most popular effect from this era wa the light organ, that made lamps to flash to different frequencies, originally three channels (bass, middle, treble).

      In the early seventies light sequencers came to use. The idea was to make the lights only react to the bass beat so that one light channel would turn on at time and the light bulb on would change every time the bass beat hits. This gave an easy and dramatic sound activated effect that the eye could follow easily and the Sound Sequencer or Sound Chaser was born. Over the years various variations of this technology have been used.

      In the later 1970's the smoke machine arrived. Instead of just seeing the lamps flashing, provided you used the right kind of lamp, you could see the whole beam passing through the air. This heralded the reign of the "PIN SPOT" (PAR36) with a narrow concentrated beam. Sound Chasers combined with PAR36 light and smoke could be used to create qutie stunning effects. Ath the same time came motorized effects like helicopter and sweeper that turned the ligth bulb generating the light beam. Next came flower effect, that produces the multiple beams using mirror ball type (possibly colored and spinning) mirror system and force them in one direction through a lens.

      Modern disco lighting nowadays is generally modern technology combined with earlier ideas. Multiple beams of the mirror ball, 3D "in air" beam projection and sound activation are the main components still nowadays. The new component on disco lighting used often nowadays are intelligent lighting instruments. Those intellinget lighing instruments send a light beam through a colour filter and a shape (called a "GOBO") then project it onto a mirror that is aimed to different directions with two electrical motors (usually stepper or servo motors). They allow selection of light color, beam shape, beam brigtness and beam direction. Those intelligent lighting instruments are generally controlled using digital DMX-512 light control interface, and the light operator runs them trough a special light control panel or computer program.

      Stage and show lighting

      Lighting is important in theatre and shows. Lighting allows us to see the performers. Lighting provides a tool for setting moods and tones of scenes on stage. Different type of performanced have different lighting needs. Here are some typical lighting situations:

      • Dance - Back lighting
      • Musical - Beamlighting
      • Theatre plays - a somwhow realistic looking combination of different lights
      • Straight Theatre - Light through a window...
      Stage lighting is achieved by the use of a large number of powerful stage lights, or lanterns (or luminaires). There are a great variety of these, for different applications, or of different make or vintage. So there are many different types of lighting instruments used in any theatre. Each type of instrument plays an important role in the overall lighting scheme. The most common light types used in theatres are plane convex lights, freshnels, profiles, which are the generic classes of spotlights. In addition to this floods are used for various applications. Also used are PAR cans , but these offer little control and are used more in rock lighting than in theatre. Most luminaires use at least one lens, which is a piece of glass with one or both sides curved for concentrating or dispersing the light beam; this produces a variation in the beam angle and the quality of the light produced. Some luminaires utilise an attachment on the front of the unit called a barndoor. This consists of four movable metal flaps which are used to control the spill of light produced.The lamp which generates the light inside light instrument is a glass (or quartz) envelope which contains a filament or electrodes surrounded by a gas. The most common lamp types are:
      • tungsten
      • tungsten halogen
      • HMI (Hydrargyrum Medium arc-length Iodide)
      • CID (Compact Iodide Daylight)
      • SCI (Compact Source Iodide)
      Lanterns are hung (or rigged) in lighting positions and are focused (or angled) onto the stage (or anything else). If coloured or tinted light is required, as is usually the case, sheets of gel (or colour) held in special gel frames are placed in front of the lanterns.

      The light color is controlled by color filters that are placed in front of the light bulb that created the white light. The filter passed through the needed wavelengths to produce the needed light color. In the early days of the electric filament lamp, gelatin color filters were used to color stage lighting fixtures. Gelatin filters dissolved when wet, and could not withstand the high heat from the tungsten halogen lamp. Next filter technology was Cinemoid. Cinemoid used a colored acetate sheeting, with inherent self-extinguishing properties. 'Cinemoid' is no longer produced and has been replaced by polyester based materials, such as 'Roscolux' and 'Lee' filters. All Lee's light control and color effect filters are made from a tough polyester film base, which is impervious to water, is totally transparent and has a high melting point. This base is then coated with specially prepared lacquers. The lacquer coating is applied to both sides of the film, is also tough and flexible and has a high resistance to water and heat. This kind of filters may scratch and the surface color may actually vaporize from the surface, through atmospheric contact. 'Roscolux' filters are designed to withstand the high temperatures of stage and studio lighting fixtures. Roscolux filters are colored when the plastic is in the resin stage before the polymer is cast into film. This results in a tough, resistant and durable filter with the color actually part of the plastic, instead of just applied to it.

      The key to lighting control lies in the dimmer. Light dimmer allows the controlling of the light output (the light intensity) of different lighting instruments. Those dimers used to be resistances, autotransformers, saturable reactors and other specialist components. Nowadays light dimmers use phase control principle and use electronics switching components like thyristors, triacs, GTOs and FETs. Thyristors and triacs being the most commonly used components for dimmers in use nowadays. Dimmers are normally available in channels, which can be thought of as electrical circuits capable of handling a rated load. Standard dimming channels are offered in 600-, 1,200-, and 2,400-watt capacities, which correspond to electrical loads of 5, 10, and 20 amps in 120V AC system. In 230V AC systems most the channels are most often offered with 4A (920W) or 10A (2300W) power. In large dimming setups all the dimmer are usually located in the central dimming room or other central location. The lanterns are usually tailed and plugged up to dimmer outlets via a patch board. Various types of cabling and connectors are used to connect lighting instruments to dimmers. Often times, permanent theatre installations will have special outlet strips along the lighting battens to connect the instruments. In less permanent installations movable breakouts are used. Breakouts connect normal single light connectors to a multi-conductor cable usually terminated with a Socapex connector. Using multi-conductor cables the amount of separate wires coming from dimmers to lights can be reduced (=easier to manage). In small set-ups the lights are just directly wired to the dimmer outlets. In distributed dimming systems the dimmers with few channels of outputs are rigged together with lighting instruments to lighting setup, and then all separate dimmer devices are controlled using one lighting console through DMX-512 bus.

      Typical theatre stage lighting setup has tens of dimmer channels and lots of lights conected to them. A lot of pub venues just use a dimmer pack, small programmable DMX control desk, and a few PAR cans, usually on 4 or 6 channels. This can be a very versatile arrangement for a relatively small investment.

      The light dimmers are most often controlled remotely using light control desk which communicates with the dimmers through control cable, which can carry the control information in either analogue format (usully 0-10V DC) or digital format (most often using DMX-512 protocol). The simplest lighting board one is likely to find today allows the operator to set up two scenes and cross-fade between them. These are commonly referred to as X-Y boards. An X-Y board has a number of channels associated with it, where each channel can control one or more dimmer channels. For example, twelve channels may be controlled with a small board. Levels can be set for each of these individual channels on two scenes and a -fader allows switching between scenes. Advanced lighting boards usually provide all of the same features as an X-Y board, but add the ability to store scenes, record a sequence of scenes in a cue stack, and record light chases. Control desks normally come with provision for controlling 6, 12, 18, 24, 36 or even 48 dimmers (there are also bigger desks in very large systems).

      The followspot is simply a high power spotlight mounted on a stand. An operator (or stagehand) controls the lamp and is able to pan and tilt the spotlight, following an actor anywhere on stage. Today, the followspot fixture is still commonly used, for theatre, dance, opera and other entertainment events.

      In addition to the normal lights controlled by light dimmers, there are a huge variety of units that fall within the general category of 'intelligent'. The most well-known type is probably that of moving lights, where the luminaire is able to control the position of the light beam, together with other aspects of the light quality. Moving lights can be considered as Moving Mirror or Moving Head units. Moving head devices physically point the whole light in different directions by using a motorised yoke. Moving mirror type units (used mostly in nightclubs and rock shows) are best suited for prolonged, fast moving lighting effects. Moving lights are generally controlled using digital DMX-512 interface.In addition to those there are also color scrollers and disco effects. Use of a colour scroller system within a theatrical lighting rig can greatly increase its potential. Instead of fitting one colour filter per luminaire, the scroller allows a row of colours to be stored and wound to the chosen colour. Scrollers are pretty simple to operate. Sending a channel percent value to the scroller will set the position in the string and thus the color. What value you will need to send will depend on how many cells you have in your string, in what oder your colors are there and what color you want. Each scroller takes one light controlling channel. Powering anc controlling color scrollers vary by brand. Scrollers, moving mirrors, and other attachments for light fixturesare typically powered by a special type of external power supply. Thescroller, etc. is connected to the power supply by a special 4-pin XLRcable that provides both the DMX signal and the power (usually 24V) to the unit. You would plug the DMX line from your console into the power supplyand not the scroller. You can buy power supplies capable of poweringmultiple scrollers, so it's the responsibility of the power supply tosplit the signal and deliver it to each of the scrollers. Generally you can think that there is a power supply that takes an AC feed (NOT a dimmed) and a DMX signal from the console and then some number(like up to 16) scrollers daisy chain on 4-pin cable out of the power supply. There are also systems where each scroller takes an AC feed and a DMX signal from the console (many intelligent lighting instruments are built like this). Disco effect are type of intelligent fitting that can be used to create the effects seen in nightclubs and at parties. There is a wide range of equipment available in this category, from simple strobes to multi-colour, multi-beam units. Most disco light effects are either controlled through DMX-512 interface or move automatically semi-randomly based on sound around them (some have built-in microphone or sound input connector for this).

      There are also so called "intelligent lights". Typical intelligent light instrument allows the user to control the light color and direction the light points to, possibly also can change a gobo figure. This kind of intelligent lighting fixtures are generally controlled through DMX-512 interface (idea is that one or more channels in DMX-512 data controls each intelligent light adjustable function). There is wide variety of intelligent lighting fixtures made for different uses, from a small night club to a large rock show stage use. Here are few things to consider when selecting intelligent lighting fixture:

      • 1) Noise from fans... check out everything... Buying sight unseen can lead to disappointing expectations when a unit is either too dim or too noisy. Pan/Tilt limits... Reset options. Some have it others need it programmed in the controller.
      • 2) Stepper motors vs servo.... Just depends on the level of smoothness you're looking for in movement. Some lights are more accurate and move smoother than some other lights.
      • 3) Cycle time... Many of the lower end fixtures run for say 15 mins. and need a cooling down period. Most of the bigger and pricier moving lights have adequate cooling to run continuously.
      • 4) Intensity of candle power &/or lumens output to a defined distance. Compare to a set standard of your application.
      • 5) Check the price and life of the light bulb used in the device. The bulbs can run $140-400 each on some lights.
      Often the Dj lights of 250 watts or less won't have the punch to be really visible when using fresnels, pars, or ERS's of 575/750/1000 wattages forwashes. The Dj gear is OK for smaller events like home parties, small low ceiling clubs, but do not work on large stage applications. SO before getting anything you need to know what purpose do you want them for: club, arena rock, corporatebooths/parties and how much money do you have for units and then buying bulbs. All these factors are issues to add when buying intelligent lighting.

      Typical small "rock and roll" club stage setup few sets of PAR can bars connected to dimmer pack (6 ot 12 channels) and some moving lights.PAR lamps stand for Parabolic Aluminised Reflector. The PARABOLIC ALUMINIZED REFLECTOR (or PAR lamp) is a sealed beam type of lamp, similar to an automotive headlamp. The filament, reflector and lens are all optically aligned at the factory, and sealed into a single lamp - resulting in a highly efficient source. As the PAR lamp is a complete lighting unit, fixtures for them are very simple indeed. The PAR lamp is also sometimes known in Europe as the 'pressed glass reflector lamp'. PAR cans come in many versions (PAR 56, PAR64 etc.). Today, PAR lamps are available in various diameters (4.5" to 8"), and various wattages (75-1000 w.) The highly efficient PAR64 lamp (8' lens) is extensively used by the theatre and entertainment industry and the fixtures are often referred to as 'PAR cans'. The bigger the number with a par can is the bigger its size. Electric lamps used in PAR lamps are sized by multiples of 1/8 inch. Therefor a PAR-8 (if such exists) would have a 1 inch diameter glass envelope.A PAR-64 is 8 inched in diam. To convert PAR number to inches divide lamp number by 8. Some common PAR lamp types:

      • PAR 36: Practically all the PAR 36 fittings are standard disco pinspot type with the very narrow beam 6V 30W bulb. Most typical bulb used is VNSP bulb type 4515, which has 5 degrees beam and uses 6V 30W. The PAR 36 cans almost always have a transformer built in, and the bulb has screw terminals on the back. There are also other more rerely used special PAR 36 lamps used (12V models, up to 100W models etc.). PAR 36 lamp diameter is 4.3 inches (around 110 mm). PAR36 lamps come in a mega range of odd ball voltages and powers for things like marine and aircraft (for example 28V ACL version). Generally PAR36 lamps are a bit shortlived on continuous duty.
      • PAR 38: PAR 38 lamp diameter is around 4.75 inches (around 120 mm). This type of bulbs have typically ES Edison Screw cap. Typical lamp power levels available are 60, 75, 80, 100, 150 and 300 watts. Typical beam spreads are 30 and 60 degrees (special 12 degree bulbs exist also). This type of lamps are common in shop display fittings and security lights, also in outdoor garden lighting (special bulb version for outdoor use).
      • PAR 46: PAR 46 lamp diameter is around 5.75 inches (around 146 mm). Typical lamp power is around 200W. Bulb has blade connectors.
      • PAR 56: PAR 56 lamp diameter is around 7 inches (around 178 mm). Typical lamp power is 300W. Bulb has blade connectors. Typical beam spread is 11x25 degrees. Different beam spreads are available. PAR56 lamps are typically available at 300W and 500W power.
      • PAR 64: PAR 56 lamp diameter is around 8 inches (around 203 mm). Typical lamp power is 500W or 1000W. Bulb has blade connectors. Typical beam spread is 11x25 degrees. Different beam spreads are available.
      Today, the ellipsoidal reflector spotlight is still one of the basic tools of the stage lighting designer for spot-lighting applications. In Britain the 'ER' is referred to as a 'profile spotlight' or a 'mirror spot'. In its simplest form, the ER fixture consists of a housing, a light source, an ellipsoidal reflector and a plano convex lens. The light beam produced by an ER fixture is round (or 'conical') with a sharp defined cut-off edge. The fixture is actually a simple projection device and will optically project the image of anything placed at its focal point. The typical ER fixture has 4 integral framing shutters or an iris - to provided limited beam shaping. In addition, and of particular importance the ER fixture will also accept and project the design of a metal pattern, commonly known as a template or gobo. The typical ER spotlight uses a tungsten halogen type of lamp. Fixtures are available in lens diameters from about 4" to 10" and with wattages from 500 to 2000 watts. The typical stage and studio ER fixture has a lens diameter of 6 inches and a 1000 Watt lamp. The ER spotlight is selected by beam spread. Fixed beam spreads are available as follows: 5, 10, 15, 20, 25, 30, 35, 40, 50 degrees. Formerly in North America (1950's-1980's) beam spread was designated by specifying first the diameter and then the focal length of the lens. Example: a 6x9 (pronounced 6 by 9) was a fixture with a 6" diameter lens and a 9" focal length. In order to determine the spread in degrees of any particular fixture, the designer still needed to consult the manufacturers data sheet as the designation did not accurately identify the beam spread of the fixture. Today spotlights are specified in 'degrees' only. The following table shows approximate beam spread of several common ER spotlight fixtures:
      • 6x9 - 40 degrees
      • 6x12 - 30 degrees
      • 6x16 - 25 degrees
      • 6x22 - 15 degrees
      • 8x9 - 20 degrees
      • 8x13 - 13 degrees
      • 10x20 - 15 degrees
      Profiles are the light instruments that produce the narrowest beam. They operate on a similar principle to a slide or film projector in that they have a focal plane (the "gate") and the image of anything placed in that focal plane will be projected by the lens. The lens can be moved to sharpen or soften the focus. Generally, of course, there is nothing at the focal plane so you get a very sharp edged circular beam of light. These lanterns, however, have beam-shaping shutters (four of them) which can be pushed into the focal plane so that you can change the shape of the beam to square, rectangular or triangular. You can also place a gobo in the focal plane. Incidentally, it is also possible to get an iris diaphragm which can adjust the size of the circle of light projected by the lantern from the full width to a pin-spot. There are two types of profile: fixed beam and zoom. A fixed beam profile produces a beam of fixed spread, whereas you can vary the beam spread of a zoom. The most commonly profile to be found has a beam angle of 23 to 25 degrees. Zoom profiles are described by the extremes of their beam angle: a 16/30 profile, for example, has a beam which is 16 degrees at its narrowest and 30 degrees at its widest.

      Diffrent kind of filters are used to change the color of light that goes out of the lighting instrument. The idea of a color filter is that it is on the way of the lighting beam. The filter only lets the wanted combination of different colors (light wavelengths) through and stops everythign else (absorbs or reflects other color). The most typical way to control the ligth instrument color is to usea normal absorbing filter. It passes through the wanted light and absorbs other lighting.

      • The most often used absorbing filter type is called "gel". "Gels" are made of a special flexible transparent material that feels like plastic, but can withstand more heat than normal plastic. The lighting gels are genrally available as large pieces that are then cut with scissors to size and shape that matched the lighting instrument uses. Gels are generally installed to the color filter holder in the lighting instrument.
      • Other commonly used light color filter type is dichroic filter. Dichroic filters are made of glass covered with a metallic coating (deposited on glass), but they are able to withstand tremendous heat produced by high-powered lights focused in optical paths no larger than a quarter or half dollar. Intelligent lighting uses dichroic filters to change their light colors. Dichroic filter reflects unwanted wavelengths of light instead of absorbing them as normal filters do. Dichroic filters can be used to create saturated colors not capable from the gel filters. Dichroic filters are also available to replace conventional gels, their fragility and high cost estricts their use.
      The gobo has long been the lighting designer's tool to shape the light beam and project light shapes to stage. The gobo is placed to the focal plane of a suitable lighting instrument (typically profile) by the user or a set of gobos can be built into the instuments like intelligent lighting. Gobo is just a shadow mask that lets out the light at right shape and masks out the other light. Gobo is typically made from metal or metal-coated glass, or dichroic coated glass processed to have the wanted shape in it. A standard metal gobo is a piece of sheet metal with cutouts. (You canmake a crude and short-lived version with a Coca-cola can and apocketknife.) Meshed gobos are just like a normal gobo, just with a mesh so they cancarry completely cut out shapes and finer detail. The thing about mesh gobos is that you need to play with the degree of"defocusing" to blur out the mesh but not so out of focus as to make the image too blurry around the edges. A greyscale metal gobo has tiny holes of varying sizes tocreate a mesh and produce the greyscale. By careful juggling with the focus, mesh grayscale goboes will give you a greyscale image, rather than the on-off black and white image that you get fromcut-outs. Glass gobos are etched from metal caoted glass and will carry finest deatal. The gobo itself usually goes into a metal holder that slides into a slot roughly even with the shutters in the lighting instrument. Glass gobos need to be inserted with the shiny (mirrored) side facing the source; metal gobos can go either way. The image on the gobo will generally be projected reversed andupside-down from the way the gobo sits in the unit (trial and error will teach you if you are not sure). Color filter gel can be added as usual to the lighting instument if colors are needed. Taped-together piecesof different colored gels are sometimes used with patterns, but don'texpect to be able to control the color blending.

      Stage lighting systems are generally controllable using some form of lighting control desk that controls the dimmers and moving lights. The simples lighting desk might have just a set of sliders that the operator manually operates. The more complicated lighting desks usually have memory options to store many lighting scenes to the memory and allows the user to recall them as needed. PCs are coming to entertainment lighting quicly with the introduction of suitable control software and DMX-512 interfaces. There has been mixed reviews how well PC performs those tasks. Maybe in simplest systems there might not need to bring in PC, but in complicated systems where the control power of traditional lighting controld desks ends, a PC based system might be a very good choise. One recomendation; do not use the same machine for sound and lighting control; in fact if you are using a PC for any entertainmentapplication; lighting, sound, video, or image playback or showcontrol it isa very good idea to use separate and 'virgin' machines and closed networks. As all of us know Windows based PCs are very prone to crashes and randumerrors; so using separate and virgin machines is always a plus; once you connect a computer to the internet and download files to it or install any applications other than what you need for the show you have comprimised theintegrity of the computer. Always be wary of multi-use computers in show applications; there is nogarauntee that the apps will work well together. Many people have experienced difficulities with standard use machines being utilized for sound playback and show control applications.

      In many show lighting applications you can see two separate lighting controlling systems in use. There can be a traditional lighting desk for controlling the lights that go to the dimmers. Intelligent lights usually use a different console and protocol than the conventionals, and their control cable is run separately. Intelligent lights areoften controller with a special lighting desk optimized for intelligent lights controlling or with a suitable control software running on the PC. The use of PC gets more and more popular because there are many good control software applications that allow the light designer to make vry fancy control sequences that can be played back during the show with few keypresses, and best software even allow visualization that the lighting would look (you can design the effects in advance with just your PC without having the actual instrument or access to show location, and then then just do the fine-tuning at the show place when the instruments are installed).

      The stage lighting is usually handled by a light designer and a master electrician. The responsibilities of the Master Electrician (M.E.) are to hang, patch and focus the lights as per the lighting plot provided by the lighting designer (L.D.). Master Electrician controls the lighting loadin. Master Electrician must make sure all the instruments are hung and cabled correctly. Master Electrician is often called upon to patch the lighting console, focus instruments, manage strike, and so on, depending on the demands of the lighting designer. Master Electrician will get a lighting plot from the lighting designer (LD). If necessary, also find out from the intelligent lighting designer (iLD) where those instruments are going to be hung and how they should be numbered. (Most of the time, this is on the lighting plot.) With the designers, write down which instruments go on the same channel. Often times, especially with the truss, multiple instruments go on the same dimmer, and it is important to know this before figuring out how to cable things. Many times the M.E. or L.D. will also operate the lighting console for the production.

      In theatre environment the safety of foth actors and audience members needs to be considered. For actor safety all the lighting instrument must be securely put to place (so that they cannot fall, and safety cables make sure that if someting goes loose it does not fall to ground), lighting instruments must be in good condition, light away from material that can catch fire (lights can be very hot), light wiring is in good condition and proper fire extiguishers are easily available. Many theatres (most UK theaters for example), with a pros arch, have a fire curtain, also referred to as "the iron". Its mission in life is to give the audience TIME to evacuate in a safe and orderly fashion, and it should keep the smoke from an on-stage fire out of the house. Many theatres also use automatic vents above the stage, which makes sure that the smoke can get out from there easily instead of getting to audience. While these, forming a chimney, ensure that the stage becomes a raging inferno, they give the audience time to get out.

        Wiring

        Building a working stage lighting system involves lots of cabling to feed the power from the power source to the lighting instruments. Different theatres provide different means for connecting equipment to be powered. Some simply provide a large number of standard mains connectors you are used at your home and some provide high-current hookups. Many venues provide some sort of combination of high-current and low-current hookups. Often some medium-capacity feeds are also available.Any venue that has been properly wired by a qualified electrician will have a circuit breaker panel that is used to shut circuits off in the event that they draw too much current. It is the current capacity of circuit breaker (in amperes) that determines how much current a circuit can supply. The breaker size is chosen relative to the type of cabling and connector used for the circuit, as each have different capacities. Stage lighting very often uses a three phase power feed which is wired to the dimmer rack, which distributed the power to different lights. There used to be some specific recommendations on some countries specific to this kind of systems. The requirement/recommendation for phase separation is no longer in the IEE regulations (currently 16th edition). There is no requirement in the 16th Edition (or the 15th) to keep sockets on different phases separate. There is a specific requirement to label 415V potential anywhere where you may not expect to find it.Once upon a time (13th edition of IEE regulations) it used to be a requirement to keep connector connected to different phases on physically separated places (two meters apart..). Many people still think it is. However it hasn't been for the last two editions of the regulations. Stage wiring can use the normal household plugs for lights or some other mains plig types (this depends on regulations and environment used). The following plugs can be seen often in stage lighting systems:

        • Cam-Loc type connector: Cam-Loc is a single conductor mating connection of large brass contacts in a rubber boot that is pretty damp proof. Cam-Lock is standard for feeder-type cable used widely in USA. There are few different sizes that are used to serve everything from a 30 Amp HMI fresnel on a movie set to 600 amps of three phase distribution for a whole rock and roll lighting rig. You need to be careful with camlocks because you need to be very careful that you plug them in right way to the high current three phase feed and a camlock that is not connected to anything has it's power carrying partwith in finger reach on the connector. Camloks are scary things when in the hands of inexperienced crew.
        • Powerlock: Powerlock is a single pole electrical connector that has been specifically designed for use in the entertainment industry. It has large brass contacts in a protective plastic/rubber boot. Powerlock connector is designed to be safer to use replacement for Cam-Loc connectors. Powerlocks are keyed to prevent them being cross-plugged and they are designed in such way that it is hard to touch the mains carruing parts of the connector, no matter if connector is mated or not. Powerlock connector is available in two versions with current rating of 400A and 600A. Powerlock connector can take cables in range 50mm? - 240mm?. In the larger scale rock & roll circuit, Camlocks are rapidly being replaced by Powerlocks as the standard large mains connector. POWERLOCK is available in four standard formats, which allow complete hook up through the standard daisy chain principle. There are two Source connectors (Source connectors are supplied with a male contact incorporating a rigid finger proof nose), one for panel mounting and one for cable attachment. These are identified as Panel Source and Line Source. The two other types are identified as Drain connectors (Drain connectors are supplied with a female contact with an optional spring loaded finger proof nose), one for panel mounting and one for cable attachment. These are identified as Panel Drain and Line Drain. Powerloks are gaining popularity because of added safety compared to Camlocks. Powerloks have a nylon peg up the middle so you can't get your finger in so easily and are also keyed so that you can't plug a phase male into a neutral female, etc. Powelocks seem to be displacing camlocks pretty quickly.
        • CeeForm: CeeForm (CEE 17 7 IEC 309) is the European standard for highish-current connectors, available in 16, 32, 63 and 125A single and three-phase variants. The CeeForm connectors are widely used in Europe for connection of three phase power to theree phase equipment, distribution panels and dimmer racks. Three phase 16A and 32A connectors are often seen in the power input of many dimmer packs and in locations where three phase power is often needed (near stage). You can see 63A connectors on larger dimmer racks. Three phase 125A connectors are seen on many conference halls in the mains ditribution panels to provide power pluggable sub-panels (that provide the needed number of 16A, 32A and 63A outlets for use). Single phase 16A CeeForm connectors are used on some lighting applications to connect power to lighting instruments. Ceeform is water protected, so it will happily sit in the rain without tripping the mains out. Ceeforms are available in splash-proof (IP44) and watertight (IP67) versions. The size of the device is determined by the amperage rating. It is virtually impossible to couple a plug and receptacle of different voltage and/or amperage ratings.
        • Parallel blase (Edison): This is the common plug that you are used to at home in USA as the mains outlet connector. Stage plugs are rated for higher loads (15 or 20 amps) than many home connectors. The main benefit that you get from using this type of plug is that they are readably available at almost any hardware store. The problem with this type of connector is that they are quite easy to unplug accidentally.
        • Stage pin: This is a rectangular connector with 3 cylindrical pins in a row. The ground and neutral are closer together, so they cannot be plugged in backwards. Stage pin plugs come in various sizes for different amperages. In general, the friction between the pins and the sockets is enough to keep them securely seated, and the male pins have a slot where one can insert a knife blade (or pin splitter) to spread the 2 halves and increase the friction. This connector is mainly used in USA. This connector is very much used for lighting instruments because it is mechanically quite good (can stand use, not too big) and using it makes it harder for anyone accidentally connecting something else that dimmable lights to dimmer outlets. Three pin 20A version is commonly used connector version. The normal pinout is that center pin is ground. The pin closest to the ground is the "neutral," and the one furthest away is the "hot." Because of the configuration of the pins, it is pretty easy to plug the plugs together, even in the dark. Spread the male pins gently if the connection seems loose. There are versions of the stage pin plug which are locking.
        • Stage Plug: This is another name for Stage Pin connector. This connector is widely used as lighting wiring connector in USA at Stage and Studio lighting. The three pin version with 20 ampere rating is quite commonly used.
        • Twist-lock: looks much like a household connector used in USA, but bigger, and the 3 pins are all slightly curved. the Ground pin is bent 90 degrees, so when you mate them and twist, they can't be pulled apart (connected and twisted in a clockwise direction locks them to each other). Twist-lock connector is mainly used for USA for currents up to 20A. Twist-Loc is standard in Canadian theatres. The available type of Twist-Loc connectors goes up to 50A 250V. In the modern twist lock this prong turns in towards the center of the plug (pictured top) in the older version the pin turns out. The benefit of this type of plug is that the locking mechanism is quite strong. The problem with this type of plug is that they can be difficult to connect in low light situations. The most commonly used version has NEMA code L5-20 (theree pins, rated for 20 amperes).
        • Round pin UK style sockets: 15A round pin UK mains plugs are UK standard theatre lighting plug and socket. Those plugs were as per pre 70's UK house wiring and are still used to differentiate dimmed from undimmed sockets, that's why you see this kind of connectors in many dimmers. Non fused plugs are generally used in the entertainment industry (as opposed to fused 13A UK plugs with square pin as used in general purpose household mains in UK). This is mainly so that all the fuses are in an easily accessible location, rather than in a plug somewhere up in the roof. The 15 Amp plug/socket combination is the most common in UK although the modern 16A (CEEform) is beginning to take over. Some venues use 5Amp connectors,whic are like the 15A but bit smaller.
        • The CEE 7/7 ("Schuko") grounded plug is used as a standard in Germany, Austria, Norway, Sweden, Finland, the Netherlands, Belgium and France; it is also used in Portugal and Spain. "Schuko" is rated for maximum 16A 250V (used in both 10A and 16A 230V AC circuits). The SCHUKO plug has two pins that carry live and neutral wires, plus two safety ground connetions on the side of plug (they make contact with ground spring on the mains jack). The thing to note on "Schuko" connector is that the connector can plugged to the mains outlet on two ways, interchanging which wire is live and which is neutral. Other note is that you can plug a SCHUKO connector also ot ungrounded power outlet.
        • Many small electronics appliances in Europe use small flat "Europlug" connector. The Europlug originated as CEE 7 and has been around for almost 30years. It is a clever design that fits all the historic national sockets in all European countries, except for the UK. IEC 884 is one spec for the "Europlug" (BS EN 50075). Europlug is used in small electrical and electronic devices that need no protective ground and consume less than 2.5 A. Europlug is found on some small very low power lighting instruments (household lighting instruments, small stroboscopes etc.).

        It is very nice to have different connectors for dimmed power and mains power. Most professional theatres in the USA use either stage pin (a.k.a. 2P&G) or twist lock connected to the dimmers and edison (2 parallelblades with ground) for domestic mains power. You have to actually work atconnecting something which shouldn't be dimmed to a dimmer since it willinvariably have an edison plug. When the power is fed to the dimmer packs and other similar similar system, high power electrical power connectors are used. In Europe CeeForm connectors are often used to connect three phase power to the dimmer racks. In USA cam-lok connectors are the standard for high current three phase power feeds (get a proper electrician to connect this set of five connectors right). In USA also some other connectors are used for high current feeds. NEMA "14-50" ("Harvard Standard") is commonly used connector for high current two phase power for rental dimmer packs (up to 50A per per phase). NEMA "14-60 " is sometimes to feed two phase power (125/250V) up to 60A to dimmer packs.

        In addition to connectors described above there is large number of different multi-pin connectors used to connect a group of mains circuits through one connector. Those multi-pin connectors are generally used to carry the power from light dimming racks to the lighting bars. The most commonly used connectors for this are Socapex and Harting, but there are also many other multi-pin connectors in use.

        • Socapex: Some years ago, the entertainment industry has chosen the Socapex SL61 connectors to become the world wide standard for power distribution interconnection. The Socapex brand is so famous that "Socapex" can be considered has the worldwide generic name for 19, 7 and 37 pins connectors. Some people even call it the "Soca". The 19 pin Socapex is the most commonly used, and the standard wiring for allows running six light channels through it (each up to 20A). 90 pin Socaped is probably the most widely used mains multicore connector, used in both the USA and the UK, used for delivering six 2KW (240V) circuits down a single physical cable. Socapex connector provides three seprate wires (live, neutral and ground) for all six circuits run through it. Pin 19 appears to be unused in most applications, except for Vari*Lite, who use pin 19 for the screen of the multicore. There is a common belief that it is a good idea to common the earth conductors together in each connector; it appears that this is not permitted under the USA NEC.
        • Harting: Harting makes a large selection of industrial connectors. There is a 16-pin Lectriflex/Harting connector that is commonly used for six channel dimmer connections. 16-pin Lectriflex/Harting is commonly used for for aggregating six 2KW (240V) circuits down a single physical cable. The connector is rated at 16A per pin. All six channels have their separate live and heutral pins. There are only four ground pins, that are normally connected togeher and shared by all the circuits on the cable. There is also a 10-pin Harting connector used in some applications, this carries live and neutral through pins on the connector, and ground through the connector metal shell connection. In this way 10-pin Harting connector can carry maximum 5 channels. 10-pin Harting is commonly used to carry four channels of mains power. There is also a 6-pin Harting connector.
        • Bulgin connectors: These 8 pin multipole connectors dominate the low cost and disco marketplace in the UK. They are rated at 5A per pin, with a total plug load of 6A. Those connectors are a bit unusual. The biggest nightmare with Bulgin connectors is that there are a number of different wiring schemes adopted by various manufacturers, making the interconnection of differing equipment problemsome. Fortunately the earth pin is separate from the power pins, and so it is most unlikely that misconnection will cause a shock hazard.

        Multipins connectors are often seen on the back of dimmer equipment and/or dimmer equipment racks. Sometimes separate light circuits are wired to them or out of them using an adapter that adapts the multipin connector to many separate mains single channel mains connectors or output jacks.

        For the multipins connectors descibed above there are widely accepted wiring standard how those connectors should be wired. Please note that just because a connector has a wiring standard, it doesn't mean the cable you're using is following it. Please be very careful, especially with power connectors. Always check when using somebody else's kit. If in any doubt, check!

        When installing lihgt dimmer systems you need to consider the needed power feed for them. When designing system (touring system or permanent installation), to think about is how many dimmers you can drive with the power available. Most dimmers this side of the pond come in multiples of 600 watts (600w 1.2kw 1.8kw or 2.4ks). Usually you don't need the amount of power that is the maximum power of dimmers connected to the mains feed. In general, you can "overload" your incoming power by a decent amount, meaning having more dimmer power and total light load than your feed can handle. You could get away with more since you will never have all channels at full even if all the dimmers are loaded to capacity (which is highly unlikely) unless you are a community theatre were untrained or inexperienced lighting people might have unsupervised access to your equipment. If you have more light instruments than your power input can handle at the same time, you need to make sure that your LDs/and or MEs understand about both the maximum loading capacity of your incoming circuits so they don't plan anything stupid.

        When using three phase power feed with large dimmer packs some things need to be considered in the wiring. First it ia a good idea to distribute the dimmers among phases so that they don't get radically out of phase balance. Phase controlled dimmers are a very highly non-liner loads. Dimmers do generate a large number of odd-order harmonics (worst is third), now unlike the fundamental (50 or 60 Hz line freq.) when 3rdorder harmonics are "added up" in the neutral the magnitude increases.Usual practice is to specify the neutral conductors at 130% of phaseconductors (rated for 130% of nominal phase current).

        Modern dimming systems are larger in dimmer quantity, more heavilyloaded with fixtures and more accurately fired than ever before. Electronic dimming can present many stresses on the electrical transformer that feeds thedimming system, which will make this switch gear chatter and potentiallyover-heat the wiring and the transformer. In general terms, the SCR switching distortsthe normally smooth AC waveform. This distortion is the worst in the dimming range of 35% to 70% and travels through all of the wiring involved in the system. A typical power feed to a dimmer rack would have three hot legs, one neutral anda ground wire (three-phase four wire + ground 120/208 volt servicein USA, 230V/400 volt service in Europe).In worst case (all of the dimmers are set for a 35% dimming range) more current can be carried on neutral wire than what it is rated for (unless oversized neutral is used). This can cause overheating the wire covering, wire connectionsand the transformer without main circuit breaker tripping(because the draw on the hot legs is still below their capacity).The chatter of the switch gear is an audible warning of a potentially critical problem. The chatter can also be very irritating, especially during quiet moments. This problem can then be magnified by the layout of the power feed and load wiring.

        There are also considerations of the cable types to use. The wires used in stge work need to be able to take hard use, sometimes hard climate environment (in outside shows for example) and sometines need to withstand very hot conditions. The "pig tail" is a term that refers to the cord on stage instruments. Modern pig tails are made with fiberglass and other composite, heat resistant substances. In the old days these cords were coated with asbestos as a heat insulation. Unfortunately, asbestos has a nasty habit of causing cancer, so they are not allowed anymore. This by no means implies that you will never see stage instruments with asbestos (those can be found on old istruments).

        You should, if buying second-hand, check that the lantern is safe and that check should include earth continuity between the plug and the case. You will presumambly be in possession of some test equipment so identifying which wire goes where shouldn't be too difficult. The simplest test is to measure the quality of the connection with a multimeter (you should get very low ohms reading between connector ground and equipment metal case). On some countries (for example in UK) you need to do PAT test that makes sure that groudn id connected and there is no breaks in insulation. Generally as long as you get the earth right, in normal lamp wiring it shouldn't really matter which of the other two is live or neutral. An incandescent lamp is passive device, it just conducts, so as long as it is between the hot and neutral, it doesn't care what color the wires are and which one is live/neutral. An exception to this is if the lamp socket is an edision screw (or equivalent) the neutral should go to the outer (neutral is less likely to cause danger if you accidentally touch it). If the lamp or wiring has a power switch that switches only one wire, then that wire should cut the live wire.

        Don't rely on other people's advice blindly. Check it youself. Someone's life might depend on it.