Glossary of Technical Theatre Terms – Lighting (advanced)


ACL / A.C.L.
Acronym for AirCraft Landing Light. See AERO.

ACN
Advanced Control Network. A new (2003) ethernet-based control protocol between control desk, dimmers & moving lights. Developed by ESTA and Strand Lighting. DMX nodes are used to communicate with non-ethernet devices.

ACN
Advanced Control Network. A new (2003) ethernet-based control protocol between control desk, dimmers & moving lights. Developed by ESTA and Strand Lighting. DMX nodes are used to communicate with non-ethernet devices.

ADB
(Manufacturer) Belgian manufacturer of lanterns, control desks and dimming equipment. Named after the initials of it's founder, Adrian de Backer.
ADB website

ADB 62.5
Near-obsolete digital lighting control protocol developed by ADB. Uses a 5 pin XLR connector but is NOT compatible with DMX512

ADDRESS*
Each item of equipment controlled by DMX512 has an address, which is the first DMX control channel to which it will respond. For example, in a situation where you have three 6-way dimmer racks, the first should be addressed to 1, the second to 7 and the third to 13.

AERO
A type of high intensity Par lamp that derives its name from its use as an aircraft landing lamp. The true Aero is 28V and 250W, although there are many variations. The lamp has a very tight beam.

ALPHAPACK
(Trade Name) Portable 3 way dimmer pack manufactured by Zero 88.
Zero 88 website

AMX-192
See MULTIPLEXED SIGNAL.

ANALOGUE SIGNAL
A continuously variable signal that can have any value over a given range.
1) In lighting: an analogue voltage within the range 0 to 10 Volts can have values of 0, 2, 8.785 or any value between. Most dimmers require an analogue voltage in order to operate (from 0 to -10V or 0 to +10V depending on the manufacturer). Most lighting control desks produce a digital multiplexed output, which is converted by a demux box to an analogue signal for the dimmer. See also Digital dimmer.
2) Sound: An analogue recording will record the exact waveform of the original sound, simply converting it to an electrical signal at the microphone, and back into air movement at the speaker. See DIGITAL.

ANGSTROM
Unit of measurement of length (e.g. for wavelengths of light). 1 Angstrom is equal to one ten billionth (1 x 10-10) of a metre. The unit is named after the Swedish physicist Anders J. ?ngstr?m.
See WAVELENGTH.

ANSI / A.N.S.I.
American National Standards Institute. Three letter ANSI codes are used in the US to identify lamps.
ANSI website

ANTI PROSCENIUM
Originally Ante Proscenium, meaning in front of the proscenium.
See ADVANCE BAR.

APOLLO DESIGN TECHNOLOGY
(Manufacturer) US-based manufacturer of gel, gobos, effects and scrollers.
Apollo Design Technology Inc. website

ARC LIGHT
See DISCHARGE LAMP.

ARCHITECTURAL LAMP
A type of linear filament lamp with contacts at 90 degrees to the filament which can gives the appearance of a continuous line of light (similar to neon, but dimmable).

ARCLINE
(Trade Name) A coloured plastic tube containing a number of small strobe units which, when triggered, flash in sequence down the tube. Many tubes can be connected together.

ARRI
(Manufacturer) German/US manufacturer of film lighting and cameras (Arriflex). Founded in 1917. Previously, Arri made a range of lighting desks (including Imagine, Impulse, Mirage, Microlux) which were early versions of desks now produced by ETC. ETC took over the lighting control side of Arri in 1995.
ARRI website

ART-NET
Ethernet-based lighting control protocol, developed by Artistic Licence. ArtNet can carry up to 256 DMX512 universes on the ethernet saving on cable runs. With the development of wireless networking the possibilities are endless.
Art Net website

ARTISAN
(Trade Name) Moving light control console made by Vari*Lite.
Vari*Lite Website

AVOLITES
(Manufacturer) UK-based manufacturer of lighting control consoles (Azure, Pearl, Sapphire, Diamond) and dimmers.
Avolites website

AWG
American Wire Gauge. US system for measuring the thickness of wire. The lower the number, the thicker the wire.

BAFFLE
1) A sheet of material used to prevent a spill of light in a lantern or in part of a set.
2) A panel in a loudspeaker cabinet designed to reduce back interference noise by isolating the front and rear of the loudspeaker diaphragm.
3) A panel in an auditorium positioned so as to reduce sound reflections and improve the acoustics of the space.
4) What most of this jargon will do to any non-technical theatrical type.

BAKELITE
(Trade Name) Early type of thermosetting plastic often used for electrical plugs and sockets. Has a distinctive fishy (ammonia) smell when burning.

BALLAST
A unit used in conjunction with discharge lamps containing capacitors, inductors and other start-up circuitry. The inductor is initially used to develop a high potential (voltage) to strike the discharge and is then used to limit the current flow while the lamp is lit.

BALLYHOO
(US) Swinging a followspot beam around in a figure of eight pattern. A more random effect is sometimes known as an RKO (after the searchlights used in the RKO Pictures movie logo.

BARE ENDS
Term to describe an electrical cable which has no connector at one end (for example, a SPEAKON to BARE ENDS cable is used to connect the terminals of a speaker cabinet to a speakon socket, and a 63A socket to bare ends might be used to wire in a temporary supply from a power distribution board before connecting equipment. Any installation work of this sort should only be carried out by a qualified electrician, and should never be done 'live'.

BASE PLATE
A metal plate which prevents damage to floors when using scaffolding or trussing.

BAUD
(Bits per second) Measurement of the speed of electronic communications protocols. DMX512 operates at 250,000 baud (i.e. 250,000 electronic signal changes per second).

BECTU
Broadcasting, Entertainment, Cinematograph and Theatre Union. The UK entertainment technicians union. (US equivalent is IATSE)
BECTU website

BETAPACK
(Trade Name) Portable 6 way dimmer pack manufactured in the UK by Zero88.
Zero 88 website

BIFOCAL SPOT
Profile lantern with two sets of shutters, one of which produces a hard edge, and one a soft edge. Not necessary in zoom profiles, because this requirement is fulfilled by two lenses.

BINARY*
BIT = Binary Digit. More information coming soon.

BIOBOX
(Aus) Australian term for the lighting control booth at the rear of the auditorium. Shortened version of BIOGRAPH BOX, after it's original function as a cinema projection box. Sometimes also known as the DOME if followspots are controlled from the same position.

BLEECON
Trade name for a type of low voltage 8 pin connector which is similar to the audio DIN plug. Used most often for carrying signals from analogue lighting control desks to dimmers or to demux boxes. Originally manufactured by Belling and Lee, hence BLEEcon (for connector).

BLEED
1) Dimmers which are incorrectly trimmed are said to bleed. That is, the dimmer still gives a small output, causing the lantern to glow, when the control signal is at a minimum.
2) A contrasting colour paint still showing through a newly-applied top coat is said to be bleeding.

BLONDE
2000W open-faced flood lamp used in film / TV lighting. So-called because of it's yellow/gold paint finish. See also REDHEAD.

BNC
Coaxial connector used for carrying a composite video signal or radio frequency signal. BNC stands for Bayonet Neill Concelman - after original inventors Carl Concelman and Paul Neill who developed the connector in the late 1940s. BNC is also thought to stand for 'Bayonet Nut Connector'.

BOMB TANK
Metal bin or box covered with fine mesh in which Theatrical Maroons can be safely detonated.
See also PYROTECHNICS.

BOOMERANG
1) See COLOUR CHANGER.
2) Old name for a BOOM (vertical lighting position).

BOWENS
Short for Bowens Flash Unit. Instrument which produces a bright white flash when triggered. Used by professional photographers. Unlike a STROBE, the Bowens unit needs to charge up between flashes (around 10 seconds) so is unsuitable for the same applications, but is ideally suited for recreating bright lightning flashes on stage.

BOX
Lighting Box - see CONTROL ROOM.

BOX BOOM
US term for a front of house vertical lighting position (predominantly sidelight as the booms are rigged from the boxes nearest the proscenium arch).

BOX TRUSS
See TRUSS.

BSI
British Standards Institute.

BUBBLE
1) (especially TV and Film) Jargon for a replacement lamp.
2) The glass part of a lamp.
See also GLOBE, LAMP.

BULGIN
Range of connectors used for multipin or 'non-standard' connections. The small 3 pin Bulgin plug is used on the Le Maitre Pyroflash system. The larger 8-pin round 'truck plug' allows the connection of 6 dimmer circuits (up to 6A each) via a single multicore cable. This is ideal for carrying multiple dimmed circuits to a moving set-piece or truck. The 8-pin round connector has become a standard for disco lighting systems.
Bulgin Components website

BUSBAR
Metal bar carrying incoming electrical supply into which portable dimmer racks or other large power requirements can be wired directly. An enclosure containing busbars is a Busbar Chamber.

C.C.T.V. / CCTV
Closed Circuit television. A video relay system, used in the theatre to give a view of the stage to remote technical operators (especially stage managers). Also used to give musical performers a view of the conductor (and vice versa) to help in keeping time. It's called Closed Circuit because the signal is not being broadcast anywhere - there's a direct link between camera and monitor.

CABLE GRIP
A U-shaped clip and saddle used for terminating wire rope. Also known as a Bulldog, Dog Grip or Wire Rope Clip.

CAMLOCK
(Trade Name - Crouse Hinds - CAMLOK) Single pole connector used on professional power distribution & dimming systems. A separate connector is used for each phase/neutral of the supply.Originally developed for touring concerts, as power demands increase it's finding more use in theatres.

CANTATA
(Trade Name) Range of 1200W lanterns produced by Rank Strand (now Strand Lighting) in the UK.
Strand Lighting website
Strand Archive

CAROUSEL
Circular slide magazine; also refers to a 35mm slide projector using this type of magazine (Kodak trade name). See PROJECTION.

CAST LIGHTING
Canadian creators of WYSIWYG software.
Cast Lighting website

CHAIN HOIST
Manually operated or electrically driven hoist for lifting scenery and lighting equipment. The chain hoists are rigged to fixed points in the venue. Commonly used to lift lighting truss into position for touring shows or concerts.

CHIAROSCURO
(n.) In Lighting or Scenic design (and the Art world), Chiaroscuro means the use of contrasts of light and shade, especially in order to enhance the depiction of character and for general dramatic effect. Many painters are said to be masters of Chiaroscuro (especially Rembrandt, Caravaggio etc.) From the Italian words chiaro 'clear, bright' and oscuro 'dark'. From the Random House Word of the Day website.

CHOPPERS
(Followspot term) Two horizontal masking shutters used in followspots to shape the beam above and below.
Submitted by Bert Morris.

CID
(Compact Iodide Daylight) A high intensity discharge lamp that produces a light similar in colour temperature to daylight approx. 5500K). A 1000W CID lamp produces 2.5 times more light than a 2000W tungsten halogen source.

CIE
(Commission Internationale d'Eclairage) International lighting forum which has produced (amongst many other things) a series of universally recognised symbols for lighting plans.
CIE website

CITT
Canadian Institute for Theatre Technology.
CITT website

COLOUR CORRECTION
The use of colour filters to compensate for the different colour temperatures of different light sources. Important in lighting for TV and film.

CONCAVE
Lens shape. Edges are wider than the centre of the lens. Useful to remember that 'caves' go inward.

CONDENSER LENS
Loosely applied to any spotlight lens which condenses diverging rays into a beam, but more correctly to the short focus combination of two or more lenses in a jacket used for illuminating a slide or effect disc. Also used in some profile lanterns and followspots to produce a smoother light (especially for gobo work).

CONDUIT
Metal or plastic pipe used to carry electrical conductors as part of a permanent electrical installation. See also Trunking.
Also used to add weight to the bottom of a flown cloth.

CONVEX
Lens shape. Edges are thinner than the centre of the lens.

COVE
US for front of house catwalk lighting positions. Also 'Balcony Rail'.

CROSBYS
US for saddle and 'U' cable clamps (from the manufacturers name).
Crosby Group website

CSI
(Compact Source Iodide) A high intensity discharge lamp. Most often used in followspots, because it has a colour temperature (approx. 4000K) close to that of the tungsten halogen lamps.

CUE STACK
Section of a lighting desk which allows a list of pre-plotted lighting states to be 'played back' on the push of a button. These lighting states normally have fade times allocated to them. Lighting desks designed for theatrical use will have this as the primary control, but a rock desk will have more 'hands on' control as a priority, only providing a cue stack for occasional use.

D54
See MULTIPLEX.

DAISY-CHAINING
Connecting items of equipment together by linking from one to the next in a chain. Used for connecting demux boxes to dimmers etc.

DESIGNERS CONTROL
See RIGGERS CONTROL.

DIMMER DOUBLING
A system designed by ETC where two ETC lanterns can be connected to a single ETC dimmer, and have different intensities. It only works with 115V / 60Hz supplies (e.g. USA). A special adapter ('twofer') is connected to the dimmer output. This contains a series of diodes which split the AC sine wave into two halves (positive and negative). Each half is sent to a separate socket on the adaptor and from there to a modified ETC Source Four lantern with a 77 volt lamp. Using these lower voltage lamps means that full intensity is achievable using only half the AC wave. The system will not work in the UK or other countries with 50Hz power supplies as the flickering of the lamps is too noticeable.
Dimmer Doubling information on ETC website

DIMMER LAW (Control desk)
The dimmer law in a lighting desk defines the relationship between the control value (fader position) and the console output value (outgoing DMX level).
Submitted by Andre Broucke

DIMMER LAW (Dimmer)
The dimmer law defines the relationship between the incoming DMX control value and the dimmer output RMS voltage. Common dimmer laws are 'linear RMS voltage' and 'linear light output'. Around the rated lamp voltage the light output is quite sensitive to voltage variations (a slightly lower voltage can also improve lamp life). If the dimmer is set to 'linear light' and you fade from 100% to 95%, the light output will be reduced by 5%. If you set the dimmer to 'linear RMS voltage' and you fade from 100% to 95%, the light output will be reduced by more than 5%.
Submitted by Andre Broucke

DIMMING SHUTTER
Mechanical way of dimming the light output from a discharge lamp or projector when dimming the lamp is not possible. Consists of a series of horizontal blades which are rotated to reduce and then cut the light completely. See also DOWSER/DOUSER.

DIN
Deutscher Industrie Normen. European standard covering audio connectors and tape equalisation characteristics.

DIP SWITCH
Small plastic switch used to configure the functions of a piece of equipment. Most often used for setting the DMX address of either a moving light, colour scroller, or LED unit.
DIP stands for Dual In-line Package.

DISCHARGE LAMP
A high-powered source of light produced by means of an electrical discharge between two electrodes. An arc light, for example uses a discharge between two carbon rods which are manually or automatically fed together as they are burnt up. The use of this type of lighting is restricted to non-dimming applications such as followspots and projection, where dimming is achieved by mechanical means. Many of the new generation of moving lights use discharge lamps, dichroic filters and mechanical dimming shutters.
See BALLAST, CSI, CID, MSR, HMI, HTI, Xenon, MBI.

DISCONNECT
(US) Also known as a COMPANY SWITCH, this is a large capacity power connection point on/near the stage which touring companies can use to connect their equipment.

DISSOLVE UNIT
Interface connected between two or more slide projectors and a tape player. Synchronisation signals recorded onto the tape are detected by the dissolve unit and fade up the lamp in one slide projector while changing the slide in the other, and then vice versa, producing a dipless crossfade between the two images.

DISTRIBUTION BOARD
System of interconnected fuse carriers and cabling that routes an incoming power supply to a number of different outputs. Known colloquially as DISTRO.

DISTRO / POWER DISTRO
See DISTRIBUTION BOARD.

DMX512-A
See MULTIPLEXED SIGNAL.

DOME
1) (Aus) Follow spot location usually at rear of the upper gallery. Sometimes referred to as BIOBOX, where the control booth and followspot position are the same. 2) (Aus) A Followspot in any location (from the above).

DOME OP
Australian term for the followspot operator. See DOME.
Submitted by Mac Calder

DONUT
A metal plate with a hole in the middle inserted in the colour runners of a lantern to sharpen focus (in the case of a profile) or reduce spill.

DOWSER (UK) / DOUSER (US)
A metal flag used in larger followspots and projection equipment to cut off the light beam without cutting off the electrical supply. Discharge lamps cannot be dimmed, so this is the only way of stopping light. Discharge lamps need a period of cooling down when they are turned off before they can be turned on again, so they should not be switched off if needed again within about two hours.
See also DIMMING SHUTTER.

DRIFT WIRE
A length of suspension wire of standard length with eyelets at each end between the counterweight bar and the top of the scenic piece flown from it.

EARTH SPIKE
Copper rod inserted into the ground to maintain earth continuity (especially when using generators etc.)

EARTHING
Electrical safety requirement that metal parts of electrical equipment are connected to a common earth or ground point so that in the event of a fault, excess current can be carried away, causing the fuse to blow. Known in the USA as Ground. Some sound problems (such as hums) can be cured by altering the earthing / grounding arrangements of the system, but this should never involve removing the earth connections to equipment, only by adding an earth connection where none exists, or by adjusting the way audio cables are wired. Seek professional advice to avoid safety problems.

EGGS
Slang term used for Strand Pattern 123's, due to their shape.
Strand Archive

EMF
Abbreviation for Electromotive Force, or VOLTAGE.

EQUITY LIGHT
See GHOST LIGHT.
More on Ghost Light

ERF / E.R.F.
(US) Short for Ellipsoidal Reflector Floodlight. See also ERS.

ETC
(Manufacturer) US/UK based manufacturer of lanterns and lighting control equipment.
ETC website

ETHERNET
Computer networking protocol which is installed on many new lighting desks, to allow networking between the main desk, dimmers, and remote desks around the theatre.

EXCITER
1) See ENHANCER.
2) Exciter Lamp - the lamp in a film projector that shines through the optical soundtrack and enables it to be read by a light sensor.

EXPRESSIONISM
Theatre design and performance style which places greater value on emotion than realism. The trademark Expressionist effects were often achieved through distortion.

EYE CANDY
Lighting equipment used (especially at live music events) to look good to the audience or the camera, rather than being used to light the performers. This is distinct from equipment used to light the air above / around the band (when haze or smoke is in use) as this has a scenographic function. Eye Candy equipment provides limited functional light. 

F.B.O.
Abbreviation for Fade to Blackout.

FEEDER
In the US, a main power cable to an installation is known as a feeder.

FESTOON
1) See Swag
2) Describes tabs which adopt a sculpted shape.
3) A length of cable incorporating a number of lamp holders used for outdoor party lighting etc. Available in multi-circuit form so that the lamps can be 'chased'.

FIBRE FRAME
A colour frame made from heat resistant fibres, which doesn't get as hot to the touch as a standard metal frame.

FIELD
Refers to the spread of light intensity across a beam. Most profile lanterns have an adjustable field. A Flat field has an even distribution, a peak field has a 'hot spot' in the centre of the beam. A flat field is essential when using gobos. See Profile.

FLOATS
Early form of footlights using burning wicks floating in oil across the front of the stage. Now applies to anything rigged on the front edge of the stage (eg Float microphones, Uplights / footlights etc.)

FLOORPOCKET / FLOOR POCKET
(US) A electrical socket mounted under a flap in the stage floor (UK equivalent is DIP).

FLUORESCENCE
The property of some materials to glow when subjected to light. This normally refers to ultraviolet light, although blue visible light (along with many other colours) can cause fluorescence. The materials degrade the UV wavelengths into longer and therefore visible reflected rays. See also Phosphorescence.

FLYING PIG SYSTEMS
(Manufacturer) Makers of the Wholehog / Hog range of lighting control desks.
Flying Pig Systems website

FOG
See SMOKE MACHINE

FOOT-CANDLES
An non-SI unit of illuminance (or light) used in film, TV and architectural lighting industries. The unit is defined as the amount of illumination the inside surface of a 1-foot radius sphere would be receiving if there were a uniform point source of one candela in the exact center of the sphere. Alternatively, it can be defined as the illuminance on a 1-square foot surface of which there is a uniformly distributed flux of one lumen. This can be thought of as the amount of light that actually falls on a given surface. The foot-candle is equal to one lumen per square foot.
The SI derived unit of illuminance is the lux. One footcandle is equal to approximately 10.764 lux, although in the lighting industry, typically this is approximated as 1 footcandle being equal to 10 lux.
In the lighting industry, footcandles are a common unit of measurement used to calculate adequate lighting levels of workspaces in buildings or outdoor spaces. Footcandles are also commonly used in the museum and gallery fields, where lighting levels must be carefully controlled to conserve light-sensitive objects such as prints, photographs, and paintings, the colors of which fade when exposed to bright light for a lengthy period.

FRENCH FLAG
Film/Video term. A card or metal panel fitted to an adjustable arm used to stop unwanted light from directly entering the lens of a camera.

FTP
1) See also HIGHEST TAKES PRECEDENCE (HTP) and LATEST TAKES PRECEDENCE (LTP).
2) File Transfer Protocol - a method of transferring files across the internet.

FULL UP FINISH (FUF)
A shorthand note for manual desk lighting operators to bring all relevant dimmers to full for the end of a song / finale of a show to 'draw the applause'. Still applies for the snap build on the last beat of a song. See also LIGHTS UP

FUZZ LIGHT
A lamp with a revolving mirror and a coloured plastic dome. Gives a 'police light' effect. Usually 12 Volt or 240 Volt operation.

GALAXY
(Trade Name) Large computerised memory lighting desk. Previously manufactured by Rank Strand (now Strand Lighting)
Strand Lighting website
Strand Archive

GAM
(Manufacturer) USA based manufacturer of lighting gels, gobos and accessories. GAM stands for Great American Market. See COLOUR FILTER, GOBO.
GAM website

GAS TABLE
Distribution point for gas used in theatre lighting (from around 1816 - 1890). Various valves and wheels controlled the flow of gas from the central point to each part of the stage, so that by using a team of people, complex lighting fades could be achieved, before the advent of electricity for lighting. According to Richard Pilbrow (Stage Lighting Design: The Art, The Craft, The Life 1997) the gas table was the first stage lighting switchboard.

GEMINI
(Trade Name) Medium size computerised memory lighting desk with 180 channels. Previously manufactured by Rank Strand (now Strand Lighting)
Strand Lighting website
Strand Archive

GENIE
(Trade Name) A range of mobile access platforms or lifting devices with either hand-cranked or compressed air lifting mechanisms.
Genie Industries website

GERB
See PYROTECHNICS.

GFI / G.F.I.
(US) Ground Fault Interruptor. See RCD.

GHOST LOAD
A lamp or group of lamps used to smooth out the waveform from electronic dimmers when using an inductive load(ballasts, transformers) rather than a resistive load (lamps). Also known as a Load Lamp.

GHOSTING
A method of determining the exact position of a followspot's beam by faintly exposing it on a darker area of the stage or upon the drapes. Often done just before a 'pick up' so the operator can have the lantern aimed and ready. A more professional practice is to use sights to line up a followspot.
Submitted by Jayson Bowles

GHOSTLIGHT / GHOST LIGHT
Ghost Light (ramagrrl on Flickr) (US) A light left burning overnight on stage to keep friendly spirits illuminated and unfriendly spirits at bay. Also believed to keep the theatrical muse in a 'dark' theatre, and to stop people tripping over bits of scenery when they come into the theatre in the morning.
The ghost light consists of a vertical pole with a bare light bulb on it, and is placed on stage. Care should be taken that the cable doesn't create a trip hazard, and that the light bulb is protected with a metal cage. 
The type of bulb is not critical - it should be chosen so that enough light is emitted to enable people on stage to see furniture / other items to stop them tripping over. Where possible an energy-saving lamp should be used. 
Also known as the 'Equity Light'. See link below for more information.
Could also refers to the light emitted by a lantern when a dimmer has not been 'trimmed' correctly, and is leaking.
More information about Ghost Light

GLASS GOBO
A highly detailed gobo consisting of an aluminium pattern sandwiched between two thin pieces of glass. A glass gobo is more expensive than a standard steel gobo, and requires special handling. A glass gobo holder must be used which allows the glass to expand when heated. When used in lanterns more powerful than around 650W, the lamp should be preheated before being turned to full to warm up the gobo, otherwise the thermal shock may cause the glass to crack.

GLS
General Lighting Service. Lamps designed for general everyday use.

GPC
(US only) Grounded Pin Connector. A 3 pin plug used to connect instruments to cables / lighting circuits.  Also known as Stage Pin Connector. 

GROUP
A subdivision, permanent or optional, of a lighting board control preset, or a sound desk.

HALOGEN CYCLE
Chemical process occurring in Tungsten Halogen lamps which makes them possible. During the lamps life, Tungsten evaporates from the filament, and would normally deposit itself on the glass wall of a Tungsten lamp, causing it to blacken, and causing the output of the lamp to reduce until it finally blew. In a Tungsten Halogen lamp, the Tungsten combines with the Halogen gas elements present in the lamp envelope and is re-deposited back onto the filament. This process needs a very high temperature to operate, so Tungsten Halogen lamps are able to be a lot smaller, and run a lot hotter, than their Tungsten equivalents. See also Tungsten Halogen.

HARMONY
(Trade Name) Range of 1000W lanterns produced by Rank Strand (now Strand Lighting) in the UK.
Strand Lighting website
Strand Archive

HIGH HAT
See TOP HAT.

HIGHEST TAKES PRECEDENCE*
Abbreviated to HTP, this is the standard by which some lighting desks operate.
If there is more than one control on the desk affecting a particular channel, then the highest level of the controls will take priority and affect the output of the desk and the dimmers.
This system is universal on manual lighting desks, but there are problems with the control of moving lights, scrollers etc.
See LATEST TAKES PRECEDENCE.

HMI (Hydragyrum Medium arc-length Iodide)
A mercury-halide discharge lamp with a colour temperature of 5600K (daylight).

HOOK UP
A Hook Up is paperwork generated by the Lighting Designer for a show. It lists connections or layouts between number systems. For example, a Channel Hook Up lists the channel numbers used on the lighting plan alongside the dimmer numbers into which they're connected, and a brief text description of that channels function.

HOWIE BATTEN
(After Howard Eaton) This is a two circuit (two colour) 120V per circuit MR16 (PAR 16) batten developed by Howard for lighting cloths at close proximity. A row of these hung above a cloth allow you to light the cloth where there is little space. They have also become popular as footlights. The battens are designed to be used in pairs on a 240V (UK) power supply, connected via a series splitter to share the 240V down to 2 x 120V battens. They are also known as MR16 Battens or L&E Battens (after the manufacturer). 
Howard Eaton Lighting Ltd. website

HTI
See DISCHARGE LAMP.

HTP
See HIGHEST TAKES PRECEDENCE.

IEC / I.E.C.
International Electrotechnical Commission. The UK mains inlet connector / 'kettle lead' is known as an IEC LEAD.
IEC website

IMAG
Short for Image Magnification - the use of live feed video cameras and huge video screens to bring the details of an artists' performance to a huge stadium-sized audience.

IMPEDANCE
A term for the electrical resistance found in a/c circuits. Affects the ability of a cable to transmit low level (e.g. sound) signals over a long distance. Measured in Ohms. Speakers are rated according to power handling capabilities (Watts, W) and impedance (Ohms).

INHIBITIVE SUBMASTER
See SUBMASTER.

INSTALLATION
1) An electrical system in a particular building (e.g. "the stage lighting installation was tested last year")
2) A piece of art designed to transform a particular room or building into something other than a room in an art gallery. Installations often use complex audio-visual equipment and can be intensely immersive experiences. (e.g. "In the studio space this week we have an installation by John Doe entitled 'Space'")

JONES PLUG / JONES SOCKET
Type of multipin connector used on some lighting desks for analogue outputs.
CINCH website

K1 HAZER
The Jem K1 Hazer is a high-performance hazer produced by Martin. It provides the combination of continuous operation, long hang time, and low fluid consumption for greater economy.
Martin Website

KEYSTONE
A function available on data projectors which allows the selective stretching of the horizontal component of the projected image so that it appears to be rectangular when projected from an angle above or below the projection surface. More advanced (expensive) projectors can also keystone the vertical component of the image, and some recent projectors can automatically detect the projection surface and can automatically keystone the image to fit.
Before data projectors, special lenses were available for slide or film projectors to apply the keystone effect.
The term comes from the wedge-shape of the stone placed at the top of an arch to spread the load of the wall above equally down both sides of the arch.

KICKER LIGHT
Lanterns placed to the side of the actor to maximise the sculptural quality of the light are sometimes known as KICKERS.

KLIEG LIGHT
Named after brothers John and Anton Kliegl, the Klieg Light was originally an intense carbon arc lamp especially used in filmmaking. Modern Klieg lights use Tungsten Halogen lamps. Klieg lights are either fitted with a fresnel lens and spherical reflector (for a wash of light) or a single or pair of plank-convex lenses and an ellipsoidal reflector for a spot light.

KVA
Kilo-Volt Amps. Unit of electrical power.

LADY AND THE TRAMP
A Lady and the Tramp moment occurs when two people clearing and coiling LX or sound cables end up both coiling the same one. Named after the Disney classic animation where two dogs end up eating the same piece of spaghetti.

LASER
Acronym of Light Amplification by Stimulated Emission of Radiation. A very high energy beam of light that remains virtually parallel throughout its length. Visible in the air only when a haze of smoke or dust is introduced. Great care is required when using lasers as this energy can cause permanent damage to the retina of the eye.
How Lasers Work

LATEST TAKES PRECEDENCE*
Abbreviated to LTP, this is a standard by which some lighting desks operate.
If there is more than one control on the desk affecting a particular channel, then the latest control to operate will be the one to affect the output on stage.
This system is used on desks with moving light functionality
See also HIGHEST TAKES PRECEDENCE.

LCL
Abbreviation for Light Centre Length. This measurement (in mm) is the distance between the top of the lamp base and the optical centre of the filament. This measurement is critical as it ensures that for a particular lantern, the filament is at exactly the correct position for maximum light output and efficiency. Many different lamp types exist, but there are far fewer lamp-base types, meaning it's possible to insert the wrong lamp into a lantern very easily, resulting in poor output and efficiency.
See also MOL.

LE MAITRE
(Manufacturer) UK based manufacturer of pyrotechnic devices (Pyroflash brand name), smoke machines and other theatre effects
Le Maitre website

LED / L.E.D.
Light Emitting Diode. LED technology is becoming extremely useful in the areas of architectural lighting and video walls. LED light sources are becoming brighter and cheaper. They are extremely efficient, and give off very little heat, making them ideal for display or architectural work. LED video walls are in use all over the world - they are more efficient and lighter in weight than projection alternatives.
The LED Museum
How LEDs work

LEE
(Manufacturer) UK based manufacturer of lighting gels. See COLOUR FILTER.
Lee Filters website

LIGHT JOCKEY or LJ
Danish slang for Lighting Designer.
Submitted by Erling Larsen

LIGHTJOCKEY
Club / DJ control and visualisation software by Martin.
Martin website

LINK
See POINT CUE.

LINNEBACH PROJECTOR
Optically simple lensless system for projecting a shape from a gel or glass slide etc. onto a set or cloth. The slide is placed in the front runners of the projector which is a floodlight (with a point source lamp, and no reflector). Often used for shadow effects or simple scenic projection. The projector was developed in Germany by Adolphe Linnebach (1876-1963) in 1916 at the Court Theatre, Dresden. In order to get a sharp image, the lamp filament should be as small and as bright as possible, with adjustment to move it towards and away from the slide. A high intensity low voltage lamp is often used for this purpose.
See also OLIVETTE.

LOBSTERSCOPE
A mechanical device that reproduces the flashing 'motion-freezing' effect of a strobe. See also KK WHEEL.

LOOM
A neatly-organised bunch of cables. A wiring loom is used to avoid messy runs of cables by keeping the cables going in the same direction (to the same piece of equipment) tied together. This saves time when installing and packing-down equipment, and ensures that a piece of cable can't be mislaid or left behind. 
The cables can be taped together (using PVC tape, never Gaffer Tape) or, for more long-lasting arrangements, with cable ties. More environmentally-friendly companies use short lengths of rope for the same purpose, which are re-used over and over again. Strips of rubber can be used for the same purpose. 
The looms are named according to their purpose (e.g. the Control Loom goes from the control desk to associated equipment, and may contain a power cable, a communication cable and a DMX512 cable for the control signals). 

LOW SMOKE
Smoke that has been chilled as soon as it comes out of the smoke machine. This causes the smoke to lay close to the floor. Use fast dispersing smoke for this effect because when the smoke heats up in the air, it will rise.
Low Smoke is much safer to work with than DRY ICE, which produces a longer-lasting effect but is more expensive.
See also CRYOGENICS, DRY ICE.

LTP
See LATEST TAKES PRECEDENCE.

LUMEN / LUMENS
A measure of light output from a source. The brightness of video projectors is stated in Lumens.
See also LUX.
What Lumen rating projector should I use?

LUX
A measure of the level of illumination on a surface (1 lumen spread over 1 metre).

MAINTAINED LIGHTING
See Secondary lighting.

MAROON
An electrically detonated pyrotechnic device giving the effect of a loud explosion. Made from gunpowder encased in stout cardboard or string. Must be used within a metal bomb tank. Originally developed in the second half of the 19th century to simulate the sound of cannon, it was often used to call out the volunteer lifeboat crew in an emergency.

MASK
1) Form of theatre where actors faces are covered with masks.
2) Early word for GOBO.

MAXXYZ
Moving Light console produced by Martin.
Martin website

MBI
Metal Halide discharge lamp. See also DISCHARGE LAMP.

MCB
Minature Circuit Breaker. Up to 63A (UK). See FUSE.

MCCB
Moulded Case Circuit Breaker (over 63A - UK). See FUSE.

MEATRACK
Wheeled rack for transporting a number of pre-rigged six-lamp bars or lanterns.

MIMIC
The VDU associated with most medium and large lighting desks has a detailed mimic of the level of all dimmers and other associated information.

MINIM
(Trade Name) Range of 300W lanterns produced by Rank Strand (now Strand Lighting) in the UK.
Strand Lighting website
Strand Archive

MINUETTE
(Trade Name) Range of 500W/650W lanterns produced by CCT in the UK.
CCT Lighting website

MIRRORBALL
Large plastic sphere covered in a mosaic of small mirrors, which reflect light outwards, to cover the area with bright dots of light. Usually accompanied by a rotator (an electric motor which turns the ball). Can be very effective when lit by pinspots, or more commonly now, intense moving light beams. 

ML
Short for MOVING LIGHTS.

Mobile Elevated Work Platform (MEWP)
(often abbreviated to MEWP) A piece of access platform with a wheeled base, which can sometimes be self-propelled by the operator. The best known manufacturer is GENIE.

MOGUL BASE*
A type of lamp base. More information coming soon?

MOL
Abbreviation for Maximum Overall Length. This measurement (in mm) is the length between the ceramic lamp bases at each end of a double ended (linear) lamp, such as that used in floods and some discharge lamps.
See also LCL.

MOLEFAY
(Trade Name) 8-lamp flood lantern used for washing large areas of stage with colour, or as an audience 'blinder' for a concert. Sometimes fitted with colour scrollers for maximum flexibility. Consists of 8 PAR 36 ACL (AirCraft Landing) lamps.

MONITOR
1) An onstage speaker which allows a performer to hear the output of the PA system, or other members of a band.
2) A video display screen (not normally able to receive broadcast TV pictures) used with a CCTV system or a computer.

MR16
A 12 Volt lamp dichroic lamp commonly used in place of a Par 16 lamp in BIRDIES. See BIRDIE.

MSD
TO BE DEFINED

MSDS
Material Safety Data Sheet. Form available from manufacturers of, for example, smoke fluids. Lists any hazardous ingredients and other safety-related data about the product.

MSR
(Medium Source Rare earth) High efficiency discharge lamp with a high colour temperature (approx 5600°K). Provides around 50% more light output than a incandescent lamp of the same wattage.

MULTI
Short for MULTICORE.

MULTIPAIR CABLE
See MULTICORE.

NEON
1) A type of discharge lighting generated by a high voltage across two oppositely charged electrodes at opposite ends of a long, thin glass tube filled with neon gas. As the electrical charge flows between the electrodes, electrons collide with neon atoms causing them to give off energy in the form of visible light. Different colours can be obtained by mixing other gases, or by using fluorescent coatings. Mostly used for advertising signs - the glass tube is bent to form letters.
2) A small mains voltage indicator lamp.

NEUTRAL DENSITY FILTER
(ND) Lighting filter which reduces the brightness/intensity of a light source without changing its colour value. Used extensively in TV/film for reducing the intensity of discharge lamps or natural light sources (e.g. windows). Rarely used in theatre as dimmers fulfil a similar function (although as incandescent lamps are dimmed, the colour temperature gets warmer).

NIETHAMMER
(Manufacturer) Brand of zoom profiles & followspots with halogen or HMI lamps. Very popular in Europe. Named after Emil Niethammer.
ADB website
Submitted by Andre Broucke

OBIE LIGHT
Compact light fitting designed to mount just above a film/stills camera lens for two reasons: firstly to create a characteristic glint in the eye of the subject of the photograph/film (it's known as the Eye Light), secondly to flatten out any lines/wrinkles in the face of the subject. The Obie Light is named after the actress Merle Oberon (known to friends as 'Obie'). It was first used by her husband, cinematographer Lucien Ballard, in the 1940s to make lines and shadows disappear from her face which were due to scarring following a car accident.
The Obie Light is normally heavily diffused.

OHM
The unit of electrical resistance.

OLIVETTE
[obsolete term] Lighting instrument using an incandescent lamp (usually mogul screw-base, 1000W). The lamp was usually mounted base-up, facing a large opening (the size of a full sheet of gel). Now used as a cyc flood, the instrument was originally designed for projecting painted glass images onto cycs. See also LINNEBACH PROJECTOR.
Submitted by Audrey Glickman

OPTICAL FIBRE
See FIBRE OPTICS.

OVERLAY
(Followspot term) The wider of two followspot beams covering the same performer.
(i.e. lamp one in a pink 'bust' (head-to-shoulder) and lamp two in a blue full-body overlay (head-to-toe).
Submitted by Bert Morris.

PAGE
1) See PAGING.
2) Some theatre announcement systems use the term 'PAGE' to mean making a call (e.g. 'Can you page Simon to come to the fly floor')
3) A way of increasing the functionality of a control on a lighting desk. For example, most computerised lighting desks with SUBMASTERS will allow you to store more than one lighting state in each submaster. Each group of submasters is given a page number which is used to select which set you want to use. See also SUBMASTER.

PAGEANT
(Obsolete) Brand name of a 1000W beamlight made by Strand Electric in the UK. Produced a near parallel beam and had a set of spill rings on the front to minimise glare.
Archive - Pageant

PAN
1) A control on a mixing desk which allows the operator to position the channel's output in the final stereo image (L - R).
2) A horizontal (side-side) movement of a camera or a moving light. Short for Panorama. See also TILT.

PAR BAR
See SIX LAMP BAR.

PARABOLIC REFLECTOR
See PAR.

PARALLEL
1) The folding frame that forms the base of a readily portable platform.
2) The opposite of SERIES when referring to wiring two loads into one outlet. The two loads share the available current, but are both given the same voltage.

PARNEL
Brand name for a wash light manufactured by ETC. It's a cross between a soft-edged focussable Fresnel and a ETC Source Four PAR.
ETC website - PARnel
Types of lantern

PEPPER'S GHOST
Optical illusion effect used to make a ghost appear on stage next to an actor. A sheet of glass is hung across the front of the stage so that the image of an actor standing in the orchestra pit appears to float on stage. First shown at the Royal Polytechnic Institution in London by J.H.Pepper on Christmas Eve, 1862. Following many subsequent events, Charles Dickens used it during readings of The Haunted Man. Several plays were written specially to use the effect around 1863, but the long-term future of the effect was limited by the fact that the ghost couldn't speak. Peppers Ghost is now used to great effect in smaller scale applications like the Haunted Mansion in Disney theme parks.
More about Pepper's Ghost

PHOENIX
A family of medium to large computerised lighting consoles manufactured by ADB. The desks use ISIS software running on an external PC-based processing unit which allows advanced networking possibilities.
ADB website

PHOSPHORESCENCE
The property of some materials that can store light energy and glow in the dark.

PILE-ON SUBMASTER
See SUBMASTER.

PIN PATCH
See PATCHING.

PIN PLUG
See PATCHING, PHONO PLUG.

POLE OPERATION
A mechanical means whereby pan (horizontal rotation), tilt (up and down) and focus of a lantern may be adjusted by a pole from floor level. Commonly used in TV & Film studios where fast resetting of positions is necessary.

PREFOCUS CAP
A type of lamp base which ensures that the filament is correctly lined up relative to the reflector and lens.

PREHEAT / PRE-HEAT
Smoother lighting builds from zero are achieved when a lamp filament has been warmed (at approx 15%) in the previous state.
Preheating lamps MAY prolong the life of the lamp by reducing the thermal 'shock' of going to 100% instantly. It's good practice to preheat lamps where possible, and some computerised lighting desks provide this function at the push of a button.
See also RIG CHECK.

PRELUDE
(Trade Name) Range of 500W/650W lanterns produced by Rank Strand (now Strand Lighting) in the UK.
Strand Lighting website
Strand Archive

PREVISUALISATION
Computerised tools which enable design teams to show directors and other members of the production team how lighting or scenic automation will look before the set is even built. See WYSIWYG.

PROTOCOL
See MULTIPLEX.

PSU
Power Supply Unit.

QUARTZ HALOGEN
See TUNGSTEN HALOGEN.

QUARTZCOLOR
(Manufacturer) Range of TV/Film lanterns marketed by Strand Lighting.

R & V
(Manufacturer) Reiche & Vogel. German manufacturers of low voltage beamlight. Now sometimes used to describe any beamlight.
Reiche & Vogel website

RADIO CONTROL
System whereby battery-powered practicals / props on stage can be controllable from offstage with no connecting leads.

RAT STAND
Illuminated music stand (named after manufacturer).
R.A.T. website

RDM
Remote Device Management. New lighting control protocol (officially ANSI E1.20 standard) currently under development at ESTA, which allows two-way communication over standard DMX512 cable. See also MULTIPLEXED SIGNAL.

REDHEAD
800W open-faced adjustable flood lamp used in film / TV lighting. So-called because of it's red paint finish. See also BLONDE.

REMAINDER DIM
A command used on Strand Lighting memory control desks which is comparable to the SOLO function on other desks. For example, entering CH 5 REM.DIM will put channel 5 at full and will put everything else at zero.

RESOLUTION
1) The point during a drama when the plotline reaches a conclusion, and conflict is resolved.
2) A measure of the quality of a video display
3) The quality of a sound sample is measured by the sample rate (e.g. 44.1kHz is CD quality sample rate) and the resolution (either 8 bit or 16 bit normally).

RETROFIT
A modification that can be made to an existing piece of equipment after purchase to bring it up to date.

RFU
Remote Focus Unit. Name used by ETC for a remote control for the lighting desk. Same as RIGGERS CONTROL.

RIGGERS CONTROL
A remote control for a lighting desk which enables dimmer channels to be called up from the stage when rigging or focusing. Usually battery powered, sometimes with infra-red (cordless) control. A Designers Control allows whole memories to be called up and/or played back, as well as individual dimmers.

ROCK DESK
Lighting control desk designed for rock concerts, the main feature of which is the ability to group a set of dimmers under the control of a series of flash buttons, enabling the operator to 'play the lights' in time to the music. These desks usually have a very good lighting effects capability.

ROSCO LABS
(Manufacturer) USA based manufacturer of lighting gels and scenic products. See COLOUR FILTER.
Rosco Labs website

ROUNDEL / RONDEL
A circular lighting filter either made of plastic (known as a GEL) or of glass for more permanent applications or architectural installations.

SAFARI
Lighting control software originally manufactured by AVAB Scandinavia. Safari software is now maintained by ETC.<br />Safari is also the web browser installed on Apple computers and devices.
AVAB website
ETC website

SAMOILOFF EFFECT*
TO BE DEFINED

SANDNET
Network operating system integrating standard communications protocols with a multitude of industry and manufacturer-specific control protocols.
Sand Network Systems website

SCANNER
General name for a moving mirror lantern, especially those used in discos, rather than the more flexible units used in theatre.

SCISSOR LIFT
A scissor lift is a type of aerial work platform (AWP), also known as an aerial device, elevating work platform (EWP), or mobile elevating work platform (MEWP). The AWP is a mechanical device used to provide temporary access for people or equipment to inaccessible areas, usually at height. The MEWP can usually be driven around the work area by the operator at height to provide safe access to a wide area, on a flat floor. Scissor lifts have also been used in scenic automation to provide a moveable platform, often built onto a moving base. The scissor lift is used because it is a self-contained device which requires no construction for it to operate within, and which does not extend beyond the horizontal dimensions of the platform.
The mechanism to achieve the vertical lift is the use of linked, folding supports in a criss-cross X pattern, known as a pantograph (or scissor mechanism). The upward motion is achieved by the application of pressure to the outside of the lowest set of supports, elongating the crossing pattern, and propelling the work platform vertically. The platform may also have an extending bridge section to allow closer access to the work area, because of the inherent limits of vertical-only movement.
The contraction of the scissor action can be hydraulic, pneumatic or mechanical (via a leadscrew or rack and pinion system). Depending on the power system employed on the lift, it may require no power to enter descent mode, but rather a simple release of hydraulic or pneumatic pressure. This is the main reason that these methods of powering the lifts are preferred, as it allows a fail-safe option of returning the platform to the ground by release of a manual valve.

SCOOP
A special type of floodlight consisting of a lamp mounted in a large ellipsoidal reflector. The body of the instrument is usually circular which means a soft edged circular beam is produced. A standard FLOOD has a rectangular body.

SCR
Silicon Controlled Rectifier. See THYRISTOR.

SECONDARY LIGHTING
Separately powered lighting system for use throughout the building in the event of failure of the primary system. Usually battery powered. Maintained lighting is on all the time, regardless of changes in the stage lighting, and is battery backed-up.
Non-maintained systems only light in the event of power failure or an alarm condition.
Secondary lighting systems should be regularly checked by an electrician to ensure they operate correctly.

SELECON
(Manufacturer) New Zealand-based manufacturer of theatre lanterns.
Selecon website

SEMIOTICS
The study of signs - many conventions in lighting design rely on signs (blue must be night-time, red is evil etc.)
Semiotics for Beginners

SHORT NOSE
Normally refers to a Short-Nose Parcan - a lighting instrument that uses a normal size PAR lamp, but has been shortened to either make it less obtrusive, or to get a wider beam angle.

SIGHTS
A pair of metal rings attached to the side or top of a followspot which enables the operator to accurately line up the beam (by looking down the length of the followspot through the rings) before turning it on. See GHOSTING.

SILHOUETTE
1) To light the cyclorama or a piece of upstage set in such a way that the actors are cast into shadow. Can be a very dramatic effect.
2) (Trade Name) A range of 2000W lanterns manufactured by CCT in the UK.
CCT Lighting website

SIRIUS
(Trade Name) Manual/memory lighting control desk previously manufactured by Zero 88 in the UK. Available as Sirius 24 (24 channels) or Sirius 48. Desks can be linked together.
Zero 88 website

SIX LAMP BAR
An internally-wired lighting bar, designed for touring, with six socket outlets terminated in a multi-way connector (e.g. SOCAPEX or LECTRIFLEX). Often pre-rigged with lanterns (eg Parcans). Stored in Meatracks. A bar pre-rigged with Parcans is sometimes known as a PAR BAR.

SMOKE
See SMOKE MACHINE

SNAPPER
See GRELCO.

SNOOT
See TOP HAT.

SOCA
See SOCAPEX.

SOFT PATCH
See PATCHING.

SOLO
1) On a sound desk, the solo button on each input channel silences all other inputs so that channel alone can be heard. Dangerous to use during a show, but can be useful for fault-finding or testing equipment.
2) On a lighting desk, SOLO mode kills all other channels except the single dimmer you're working with. Again, can be useful for identifying a channel in a large rig, but can be dangerous during a show. Some desks allow you to assign flash buttons to SOLO mode which will turn off all channels except those loaded into that flash button or submaster. This can be used for a quick lightning effect (but it's a bit tacky). On Strand Lighting memory desks, the solo function is called REMAINDER DIM (or REM DIM).

SON ET LUMIERE
An audiovisual entertainment often based on an historical theme (and often produced in a historically relevant location). A voice narration is often used and lighting / special effects set the mood and portray certain events in time with the narration. Often used to refer to a performance with no performer where the meaning is communicated solely with technical effects.

SOUND TO LIGHT
A facility which can link the effects panel on a lighting board to an audio input which detects treble, mid and bass beats, and can flash lights or trigger effects in time to those beats. First used when electronics allowed it cheaply in the late 1960's/

SOURCE FOUR
(Trade Name) (Also known as S4) Range of lanterns manufacturer by ETC, and designed by David Cunningham. 
ETC website

SPARKY
See LAMPIE.

SPOT SEAT
Chair for suspending followspot operator above a stage / auditorium. Normally rigged on a truss system. The operator gets to the seat up a wire rope ladder, and is strapped into the seat. He or she will normally wear a harness when getting to the chair for extra safety. The seat itself is an adapted car 'bucket' seat.

STARCLOTH
See CLOTH.

STARLETTE
(Trade Name) Range of 1000W lanterns produced by CCT in the UK.
CCT Lighting website

STATE PLOT
See RUNNING PLOT.

STEP
1) A control on some lighting effects boards which enables the operator to 'step' through a chase effect in time to music etc.
2) Each separate component of a lighting effect is called a step. A chase effect with four channels flashing on will have four steps.

STRAND
1) (Manufacturer) Maker of lanterns, lighting desks and dimmers in the UK and Worldwide.
2) The bundle of individual fibres or wires that make up one of the helical elements in a rope.
Strand Lighting website
Strand Archive

STRIPLIGHT
1) A thin linear filament lamp similar to an Architectural, but having contacts at the ends of the lamp. Available clear or opaque.
2) (US) See BATTEN.

SVOBODA
Low voltage lighting batten used to create a light curtain. Named after Josef Svoboda, the Czech scenographer (1920 - 2002). The original Svoboda light batten is still manufactured by ADB. Josef Svoboda contacted ADB when he was looking for a manufacturer for his idea.
ADB website
Submitted by Andre Broucke

SWARBIES
3 or 4 , 500 or 1000 watt flood lamps mounted on a wooden skid,used as cyclorama bottom lighting or in between scenery groundrows. Probably derived from German theatre lighting company, Schwabe.

SWL
Safe Working Load.

TESTING AND TAGGING
Australian equivalent of the UK "PAT" Test - a regime for testing electrical equipment for safe operation and then logging the results.

THREEFER
An adaptor which enables three pieces of equipment to be connected to a single outlet or cable. Great care should be taken not to overload the circuit. See also TWOFER and GRELCO.

THYRISTOR
Also known as an SCR (Silicon Controlled Rectifier). An electronic switch which will pass current when triggered until the current passing through it falls to zero. Essential component of stage lighting dimmers. See also TRIAC.

TOP HAT
Also known as HIGH HAT or SNOOT. Cylinder of metal inserted into colour runners on the front of a parcan, narrow-angle profile or other lantern to limit spill light, particularly when used in view of the audience. Sometimes additional SPILL RINGS are used at the front of the top hat, to further limit spill, and to reduce glare for the audience if they have a clear view of the lantern. 

TRANSITION
1) The movement of actors / scenery & change of lighting / sound between one scene and another.
2) Video: An effect applied to a change of shot / camera angle to make it anything other than a simple cut.

TRIAC
(Triode Alternating Current switch) Electronic Semiconductor device which is an integral part of modern dimmers. When a current is applied to a triac, it starts conducting, and continues until the current passing through it falls to zero. Whereas a thyristor can only conduct half of the AC wave, a triac (as long as it's triggered at the appropriate point) will conduct both halves of the wave. See further explanation below.
Further explanation

TRUNKING

Metal or plastic wall-mounted enclosure for cables. Box shaped in cross-section. Known in the USA as RACEWAY.


TWIST LOCK
A type of heavy-duty NEMA (US National Electrical Manufacturers Association) plug or socket which has a locking capability. They are available in different configurations for different current loads (15A, 20A, 30A, 50A).

TWOFER
A two-way adaptor. See GRELCO.

UNIVERSE
TO BE DEFINED.

VARI*LITE
Trade name for a range of 'intelligent' moving lights and control equipment. Identified by VL numbers. The VL1 model was introduced in 1980 for a Genesis tour by Showco, USA.
Vari*Lite Website

VARIAC
A trade name for an autotransformer (formerly) used to dim lighting by tapping a selected reduced voltage off the transformer's winding. Not to be confused with resistance dimming.
Submitted by Peter Neilson

VIDEO
See CCTV.

VIRTUOSO
(Trade Name) Moving light control console made by Vari*Lite.
Vari*Lite Website

VL
See VARI*LITE.

VPLT
German Professional Lighting and Sound Association.
VPLT Website

WARP
1) (Trade name: ADB) The first zoom profile spotlight with ring control and 4 framing shutters which are fully rotatable.
2) "Warp and Weft" refers to the threads in a piece of fabric, or the fabric itself.
ADB lighting website

WATER CRACKER*
Device which produces a thin haze in the air by 'cracking' water droplets.

WAVELENGTH
The distance from one point on a vibrating wave to the same point on the next wave. The lengths of the sound waves (wavelengths) we can hear range from one inch to 40 feet. High frequency sounds have short wavelengths (and are more directional), low frequency sounds have long wavelengths (and are less directional). In lighting terms, blue light is short wavelength, green is medium and red is long wavelength. Beyond visible light are the short wavelength Ultra Violet light and the long wavelength Infra Red light. Wavelengths of light are measured in Angstroms.
See also FREQUENCY.

WHITWORTH
Pre-metric standard thread for bolts and associated fittings in the UK. (Pre 1972)

WIGGLY MIRRORS
Slang for so-called 'Intelligent' lights with moving mirrors.

WOOD'S LIGHT
Another name for Ultraviolet light, produced using a discharge lamp inside an envelope of intensely pigmented glass known as Wood's Glass. It was invented in 1903 by American physicist Robert Williams Wood (1868-1955) and allows ultraviolet and infrared light to pass through it while blocking most visible light. It was developed as a filter to use for communications during World War I. 

XENON
High output discharge lamp commonly used in Strobe lighting. Some followspots also use Xenon lamps. Xenon lamps have colour temperature of between 5600 - 6500°K.
See also DISCHARGE LAMP.

YO-YO
A device used for remotely moving a gobo in one plane whilst it is in the lantern. Gives the effect of a lateral movement (door opens, train passes etc.)

ZERO 88
(Manufacturer) UK-based manufacturer of control and dimming equipment.
Zero 88 website