15A PLUG
Standard power connector in UK theatres. Three round metal contacts (live, neutral and earth); the principal difference from the domestic 13A connector is that the 15A version has no fuse.

3D STUDIO MAX
Software for constructing detailed 3D models and producing animated 'walkthroughs' and 'fly-throughs', manufactured by Discreet. The program has been renamed 3DS MAX and is becoming the industry standard for 3D design for visualisation and animation.
Discreet website

A TYPE
See JACK.

A-D CONVERTER
Short for Analogue / Analog to Digital Converter. Changes a continuously varying electrical signal into a stream of binary data. Found in computer soundcards, Minidisk & CD Recorders etc..

A.J. / AJ
n. Jargon for an Adjustable Spanner. (UK) Known in the US as a C Wrench (short for Crescent Wrench).

A.L.D. / ALD
Association of Lighting Designers.(UK)
ALD Website

A1
Lighting Industry Forum code which identifies the (original) recommended usage of different lamp types. A1 coded lamps are for use in projection. See also CP, T, P2, K.

AB
A technique used to record in stereo. Two (identical) microphones are placed next to each other, parallel to each other, and pointing in the same direction. As you're looking at the action, the one on the left is panned hard left on the mixer and the one on the right is panned hard right. There are some problems with this technique, such as reflections off each microphone, leading to comb filtering and also a narrow coverage. Some sound techs try to overcome the coverage problem by spacing out the microphones, although this can lead to 'muddy' sounds due to delays. See COMB FILTERING and XY.

AB POWERING
See PHANTOM POWER.

ABO
Association of British Orchestras.
ABO website

ABSORPTION
The ability of a surface to absorp sound. The absorption coefficient of a material is a figure between 0 and 1, representing its degree of absorption.

ABTT / A.B.T.T.
The Association of British Theatre Technicians.
ABTT Website

AC
Short for ALTERNATING CURRENT.

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

ACN
Advanced Control Network. New show control protocol being developed by ESTA using ethernet. Designed to improve on the limitations of DMX512.
Historical overview of protocols

ACOUSTIC PICK-UP
See PICK UP

ACOUSTICS
The behaviour of sound and its study. The acoustics of a room depend on its size and shape and the amount and position of sound-absorbing and reflecting material.

ACT
1) Subdivision between sections of a play. A short play is a 'One-Act-er', a play with one interval has two Acts etc. Acts are subdivided further into Scenes.
2) The thing Actors can do which makes them different from Techies (!!).

ACT CHANGE
TO BE DEFINED

ACT DROP
Victorian stretched framed and painted canvas. Used as a visual stimulation during scene changes, and to indicate that there was more to come (the end being indicated by the HOUSE TABS). There are believed to be only two operational today - an original one at Gaiety Theatre, Isle Of Man, and a 1996 reproduction at Her Majesty's Theatre, Ballarat, Victoria, Australia.
Term now used to refer to any front cloth or tabs lowered during intervals. Especially pantomime / musicals.
Gaiety Theatre
Her Majesty's Theatre

ACTING AREA
That area within the performance space within which the actor may move in full view of the audience. Also known as the playing area
This term is also used to describe the smaller subdivisions of the main stage area which are lit separately by the lighting designer (e.g. 'The stage is split into 6 acting areas, 3 downstage and 3 upstage').
(Also the name of an early Strand down-lighting floodlight - known as 'Ack Ack').

ACTING EDITION
Published copy of a script containing notes for the actor and technicians, often credited to the design team of the premiere production not necessarily the playwright.

ACTIVE
In electronics (particularly audio), an 'active' circuit operates with an external power supply and is usually low power, while a 'passive' circuit operates directly on the signal using the inherent power of the surrounding circuitry.
This is why an active crossover is usually placed before the amplifiers, with integrated circuits and line level signal processing (100 Ohms impedance or greater), while a passive crossover acts after the amplifiers where the power level is much greater (16 Ohms impedance or less). Amp to speaker level is generally between 2 and 16 Ohms, while preamplifier electronics are generally 100 to 100K Ohms.
Submitted by Bruce Trotter

ACTOR
Person (male or female) who's role is to play a character other than his/her own. Although the term 'actress' is still used for a female actor, many women prefer to have the same title as the men.

AD LIB
The presence of mind by an actor to improvise when;
1) another actor fails to enter on cue
2) the normal progress of the play is disturbed
3) lines are forgotten
4) It may also be a bad habit developed by some actors whereby unnecessary 'gags' are introduced into the dialogue.

ADAM
See DIGITAL RECORDING.

ADAPTOR
1) Connector which allows two or more electrical devices to be connected to a single power outlet. The connection is normally parallel, that is, each device is fed the same voltage, but the current is divided between them. Sometimes known as a 'Twofer'. A three-way splitter is known as a 'Threefer'. A Series splitter is also available where a voltage is shared equally between two loads.
2) Also an ADAPTOR can be the same as a JUMPER.
See SERIES SPLITTER, JUMPER and GRELCO.

ADAT
See DIGITAL RECORDING.

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

ADDITIVE COLOUR MIXING
See COLOUR MIXING.

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.

ADJUSTABLE SPANNER
See A.J.

ADN
Advanced Dimmer Network. Networking protocol developed by ADB.
ADB website

ADVANCE BAR
Lighting bar positioned just downstage of the proscenium arch. Also known as ANTI PROSCENIUM.

AERIAL
Cable or rod used to send and receive radio signals (connected to transmitter and receiver or tuner).

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.

AES/EBU
Audio Engineering Society / European Broadcast Union. Digital audio transfer standard, similar to S/PDIF. Uses 3 pin XLR connectors.
What is AES/EBU

AETTI
Arts & Entertainment Technical Training Initiative (UK).

AGC
Automatic Gain Control. Circuitry within recording equipment which compensates for differences in volume in the incoming sound signal by adjusting the gain automatically. Helps to reduce wild swings in volume.

AGITPROP
The original sense of agitprop was 'agitation and propaganda on behalf of Communism', or 'a government agency or department responsible for agitation and propaganda'. The main current sense of the word is simply 'propaganda, especially socially or politically motivated propaganda appearing in literary works, films, etc.'; though the word often refers to political propaganda, it is not restricted to communist doctrine.
The word agitprop is a borrowing of Russian Agitpróp, a shortening of Agitatsiónno-propagandístskii otdél 'the Agitation Propaganda Section (of the Central Committee, or a local committee, of the Communist Party)'. It is first found in English sources in the mid 1930s.
From the Random House Word of the Day website.

AISLE
A passage through seating.

ALGINATE
An organic polymer which is a viscous gum found in the cell walls of brown algae. The commercial variety is extracted from seaweed. Supplied as a powder, when mixed with water it becomes a fast-setting mould-making material which is used to make casts of body parts or delicate prop items. The resulting mould is very detailed and strong. Dental alginate is used to make casts of teeth and gums. Take care to store the powder in an air-tight container as it's very absorbant and will 'go off' very rapidly if left open to the air.

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

ALTERNATE
Alternative name for an Understudy who is hired to understudy a main role but also contracted to play that role in certain performances. See also STANDBY, SWING, UNDERSTUDY.

ALTERNATING CURRENT*
An electric current that reverses direction in a circuit at regular intervals. Abbreviated to AC. UK mains electricity is AC and changes direction 50 times per second (that is, the frequency is 50Hz).
See also DIRECT CURRENT.

AMATEUR
Member of a theatre company which is not professional.

AMBIENT NOISE
The sound heard in a given room with no sound sources. Each space has a particular sound which aids our identification of the kind of space we're in.

AMDRAM
Short for Amateur Dramatics.

AMP
Abbreviation for ;
1) AMPERE
2) AMPLIFIER

AMPERE
The standard unit for measurement of electrical current passing through a circuit (usually abbreviated to AMP). Written as 'I' in equations. Cables, fuses and switches are designated by their current carrying capacity. (Following phrase refers to UK standards). Square pin plugs are rated at 13 Amps maximum and Round pin plugs at either 5 Amps or 15 Amps maximum, depending on the size of the pins. If a cable rated at 5 Amps is used with a load of 15 Amps (for example), the cable will overheat and possibly catch fire.

AMPHITHEATRE
Circular or oval open-air theatre with a large raked seating area (often semi-circular) sloping down to the stage. Originates from ancient Rome where vast amphitheatres were built for spectator sports and games.

AMPLIFIER
Sound equipment that converts the low voltage, low current signal from a tape deck, mixer etc. into a higher current signal suitable for driving speakers.
As a general rule, each speaker in a sound system requires a separate amplifier. Each amplifier case usually contains two amplifiers (for the separate left and right parts of the sound signal), so with a single amplifier box, you can drive two speakers.
See POWER AMPLIFIER, CROSSOVER.

AMPLITUDE
The strength of a vibrating wave; in sound, the loudness of the sound.

AMX
Powerful programming language with allows you to control a wide range of audio-visual equipment using simple interfaces (push buttons or touch screen). Widely used in complex audio-visual installations.
AMX 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.

ANGEL
Individual or company which financially supports a production.

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. Ĺngström.
See WAVELENGTH.

ANILINE DYE
A type of deep penetrating natural dye originally made from coal tar. Water-based or alcohol-based dyes are available. As the product will stain anything it comes into contact with, protective gloves and eye protection should be used.

ANIMATEUR
(From French) Facilitator of a community, education or group event (social, cultural or artistic). The Animateur may be a group leader, or may have initiated a project. She or he is responsible for running the event.

ANIMATION DISC
See EFFECTS.

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

ANTAGONIST
The opposite of the PROTAGONIST in a drama.

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

ANTI RAKE
The act of modifying furniture or props by shortening the upstage legs etc. so that they can stand level on a raked stage. Known as COUNTER RAKE in the US. See also Raked Stage.

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

APRON
Section of the stage floor which projects towards or into the auditorium. In proscenium theatres, the part of the stage in front of the house tabs, or in front of the proscenium arch.

ARBOR
US equivalent of CRADLE in a counterweight flying system.

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.

ARENA
Form of stage where the audience are seated on at least two (normally three, or all four) sides of the whole acting area. See END ON, THRUST, IN THE ROUND.

ARIA
A solo performance in an opera used to highlight the emotional state of the main character(s).

ARMOURY
The Department in a large producing theatre which deals with the maintenance and storage of prop weapons.

ARRAY
A set of loudspeakers flown in a performance space. See also CLUSTER.

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

ARTIC
Short for Articulated Lorry. Lorries of 40 feet length (or more) are used to transport sets, costume, props and sound & lighting equipment from venue to venue. A number of companies specialise in moving theatrical and musical tours around the country / world.

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

ARTNET
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.
Artistic Licence website

ASIDE
Lines spoken by an actor to the audience and not supposed to be overheard by other characters on-stage.

ASM
Assistant Stage Manager.

ASSISTANT STAGE MANAGER
Usually shortened to ASM, the assistant stage manager is the most junior member of the Stage Management team, and is often in charge of sourcing and running Properties during the run of a show. She or he is also a member of the stage 'crew'. See also STAGE MANAGER and DSM.

ATAEA / A.T.A.E.A.
Australian Theatrical and Amusement Employees Association. Union for Australian theatre technicians, now part of MEAA. See BECTU and IATSE for the UK and US equivalents.

ATMOSPHERE
The normal background sound at any location.

ATTENUATE
To reduce the intensity of a sound signal. This is what the 'PAD' switch does on a sound desk.

ATTRIBUTES
The controllable parameters of a moving light are known as the ATTRIBUTES. All moving lights will have pan & tilt, with many having colour wheels, gobo selection, gobo rotation etc. as additional attributes.

AUDITION
Process where the director or casting director of a production asks actors / actresses / performers to show him/her what they can do. Sometimes very nerve-wracking, but auditions can be a fairly painless process if handled properly. Performers are often asked to memorise a monologue from a play they like to perform for the director. Books full of suggested monologues are available. You may be asked to do a 'Cold Reading' which tests your own response to a piece of text you've not prepared.

AUDITORIUM
The part of the theatre accommodating the audience during the performance. Sometimes known as the 'house'. From the Latin Audio - 'I hear'.

AUTOCAD
Industry-standard CAD program for architects and designers. WYSIWYG contains a cut-down version of Autocad, along with visualisation tools.

AUTOMATED FIXTURE
See MOVING LIGHT.

AUTOMATIC STOP
Many reel-to-reel tape players for theatrical use have a facility that stops the tape mechanism when a piece of clear leader passes a detector adjacent to the erase head. This can be used to cue the tape up ready to start the next effect.

AUTOMATION
1) Facility available on larger sound mixing desks allowing channel muting or even fader moves to be taken under the control of a computer to ensure accurate and repeatable mixing.
2) Describes the method used instead of stage crew for moving bits of set around shows with a big budget. See MOUSE, SPADE.

AUXILIARY INPUT or RETURN
A route back into the sound desk for a line level signal sent to a piece of outboard equipment (usually effects processor / EQ unit etc.) via an auxiliary send.

AUXILIARY OUTPUT or SEND
An additional line level output from a sound desk which can be used for foldback or monitoring without tying up the main outputs. Each input channel will have a path to the Aux buss. Also used for feeding a signal to an effects processor. See Auxiliary Return.

AVAB
Swedish lighting equipment manufacturer.
Also, AVAB can refer to a digital lighting control protocol developed by the company. It's slower than DMX512 but still in use. It often uses a 5 pin XLR connector, but is NOT compatible with DMX512.
AVAB website

AVISTA / A VISTA
A change of setting / scenery unhidden from the audience. This technique is increasingly popular due to modern advances in scenic automation, where entire set changes can be accomplished in seconds.

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.

AWG
Australian Writers' Guild.
AWG website

B-TYPE
See JACK.

BACK PROJECTION
See PROJECTION.

BACK-UP
A section of a lighting control board (sometimes a separate unit) which provides an alternative method of control should the main board fail.

BACKCLOTH
See CLOTH.

BACKDROP
See CLOTH.

BACKFLAP
Hinge frequently used in Scenic Construction.

BACKING
1) Scenic piece which goes behind an opening in the set (window etc.) to hide the technical areas beyond. Also known as a Backing Flat
2) The money invested in a commercial production (by a Backer).

BACKLIGHT / BACK LIGHT
Light coming from upstage, behind scenery or actors, to sculpt and separate them from the background

BACKLINE
Backline refers to the equipment which stands at the rear of a live band when they are performing. Guitar amps, bass amps etc. are standard backline equipment. Basically, everything a live band needs apart from the instruments the band hold (e.g. guitars), the PA (and front of house desks etc.) and the band themselves is backline.

BACKSTAGE
The part of the stage and theatre which is out of the sight of the audience. The service areas of the theatre.

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.

BALANCED LINE
A method of carrying sound or data signals which reduces interference by using a third conductor, the shield. In the balanced line the shield, which is grounded, is in addition to the two signal- (or data-) carrying conductors. Balanced lines are less prone than unbalanced to interference. In balanced lines, one of the signal wires carries the audio signal, while the other carries an out-of-phase (inverted) copy. When the signal reaches the destination, the inverted copy is flipped and added to the original. Any noise added by interference is also inverted. When combined with the non-inverted noise, the two noise signals cancel each other out. See UNBALANCED LINE.

BALCONY
(US) American term for the Circle - upper level in the auditorium.

BALCONY RAIL
See CIRCLE FRONTS.

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.

BANDWAGON*
A wheeled platform. More information coming soon.

BANDWIDTH*
The range of a piece of sound equipment. If an equalizer has cutoff frequencies of 200 and 2000 Hz, then the bandwidth is the difference between them, in this case 1800 Hz.

BANJO
(US) Horizontal rail along which a curtain runs (also known as a BANJO TRACK).

BANTAM
See JACK.

BAR
The horizontal metal (steel or alloy) tube (usually 48mm in external diameter, but can be up to 60mm) hung from flying lines (or forming part of a grid) from which lighting equipment and scenery etc. may be suspended. Also known as a BARREL. When vertical, known as a BOOM. Sometimes known as a PIPE in the US, although many curse that usage, and demand the use of Batten ; 'A pipe is what you smoke; a batten is what you hang your instruments from.'.
Language, especially in theatre, is rarely universal!

BAR BELLS
Bar Bells are rung in public areas of the theatre to warn the audience that the performance is about to start/continue. Usually operated from the prompt corner and sometimes followed by Front of House Calls. The bells are also used as a warning to FOH staff that the interval is about to commence or that the show is about to end.

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'.

BARN DOORS
See BARNDOORS

BARNDOORS
A rotatable attachment consisting of two or four metal flaps (hinged) which is fixed to the front of a Fresnel or PC type lantern to cut off the beam in a particular direction(s).
Profile lanterns use SHUTTERS to achieve a greater degree of control and accuracy.
Barndoors are also available for parcans and birdies. BLACKWRAP can be used to reduce additional light spill where barndoors aren't doing the job.

BARREL
See BAR.

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

BASKET
The generic rigger's term for using a basket hitch with an extra shackle to ease or speed fitting or removing slings at height or in awkward situations.
Submitted by Chris Higgs

BASKET HITCH
A method of slinging that employs a sling wrapped around an object and both ends or eyes being connected by a component at the support point, hook, etc..
To lift a load as if in a basket.
Submitted by Chris Higgs

BASKET SHACKLE
Rigging term: In a BASKET assembly the basket shackle is the bow shackle connecting basket hitch sling to the rest of the lifting system (motor, down leg, etc..) Sometimes called the base shackle (US).
Submitted by Chris Higgs

BASS
Lower end of the musical scale. In acoustics, the range (below about 200Hz) in which there are difficulties, principally in the reproduction of sound, due to the large wavelengths involved.

BASS BIN
Slang for a speaker cabinet containing a Woofer designed for Bass sound reproduction (see also Subwoofer).

BASTARD PROMPT
Used when the Prompt Corner is Stage Right instead of the usual Stage Left. This may be for architectural reasons in a theatre with no wing space Stage Left, or may be because of the layout of set pieces which obscure a view from Stage Left, or because the band is on Stage Left and the Stage Manager can't hear him/herself cueing !

BASTARD SIDE (B.S.)
Terminology used to describe Stage Right when there is a Bastard Prompt. Stage Left is then known as Opposite Bastard (O.B.)

BATTENS
1) Timber at the top and bottom of a cloth. A Sandwich batten is used to carry a hanging cloth. It comprises two flat pieces of timber screwed together with the edge of the cloth between them.
2) Timber used for joining flats together for flying.
3) Compartmentalised floodlights set up so as to allow colour mixing. See also GROUNDROW. Low voltage battens are commonly used as light curtains & for colour washes. Known in the US as a STRIPLIGHT.
4) US term interchangable with PIPE for a flying bar.

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).

BC HOLDER
Type of UK domestic lampholder that has largely been replaced by the ES (Edison Screw) and the GES (Goliath Edison Screw) for general lighting applications in the theatre. Stage lighting equipment uses prefocus lamp bases. (Most types of Festoon still use BC holders.)

BEAM ANGLE
The angle of the cone of light produced by a lantern. Defined as the angle within which the lowest intensity in a beam of light from a lantern is not less than one-tenth of the maximum.

BEAMLIGHT
Flood lantern which uses a parabolic reflector and a low voltage high intensity lamp to produce an intense near-parallel beam. Also known as a Beam Projector.
A PARCAN is a special type of beamlight.

BEAT
1) In acoustics, a periodic variation in amplitude which results from the addition of two sound waves with nearly the same frequency. Also affects radio reception.
2) A deliberate pause for dramatic / comic effect.
3) A measure of time when cueing (e.g. 'the LX cue needs to go four beats after the door is closed').

BEBEE
(US) An American lever hoist, the name of which is often used generically for any lever chain hoist.
Submitted by Chris Higgs

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

BEGINNERS
A call given by Stage Management to bring those actors who appear in the first part of a play to the stage. e.g. 'Act One Beginners to the stage, please'. The actors/actresses are then called by name.
A similar call is given after the interval (e.g. 'Act Two Beginners to the stage please'). See also HALF, QUARTER.

BELAY
Marine rigging term for making off a line. Often encountered in climbing and mountaineering meaning the actions of rope management in arresting falls.
The belay is the attachment point to a rockface or structure. The belayer is the person tending the rope and belaying equipment (see DYNAMIC BRAKING) and 'to belay' means to perform the action of belaying. Originally with just gloved hands, now via sophisticated friction devices.
Submitted by Chris Higgs

BELL BOARD
A live sound effects board on which are mounted a number of different types of doorbells / phone bells etc. Usually operated by stage management.

BELT VOICE
Singing term - refers to a voice which has not been classically trained, but can 'belt out' songs. See also LEGIT VOICE. (For example Cosette in Les Miserables needs to have both a Legit Voice and a Belt Voice)

BELTPACK
Part of the communication ('cans') system in a theatre, the Beltpack contains the controls and circuitry to drive the HEADSET worn by crew members. Each beltpack connects into the headset ring and back to a PSU (Power Supply Unit) which is powered from the mains.
See also CANS.

BETA SP
Professional video tape format developed by Sony (short for Betacam SP). Beta SP is broadcast-quality and is a relative of Sony's failed Betamax domestic standard.

BETACAM
TO BE DEFINED.

BETAMAX
TO BE DEFINED.

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

BI-AMPLIFICATION
A way of optimising the efficiency of a speaker system by separately amplifying the High Frequency (HF) and Low Frequency (LF) portions of the sound signal (after the crossover) and sending them down two pairs of cables to the speaker. Multipin Speakon connectors have been developed to do this.

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.

BILLY BLOCK
A pulley on a short length of rope used to divert the pull of a working rope, or to suspend a single item in storage.

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

BINAURAL
Sound reproduction using two microphones usually in a 'dummy head' (to emulate the shape and the response of the human hearing system) feeding a pair of headphones, so that the listener hears the sound he or she would have heard at the recording location.

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.

BIRDIE
A compact low voltage display luminaire containing a Par 16 or MR16 lamp. So called because it is similar to, but much smaller than, the Parcan, and is hence 'one under Par'. (It's a golfing reference). Requires a 12 Volt external transformer, but is ideal for concealing in pieces of set or as downstage uplights.
See also MR16.

BIT PART
A small role for an actor.

BLACK BOX
A kind of flexible studio theatre where the audience and actors are in the same room, surrounded by black tabs (curtains). Doesn't necessarily describe the audience layout, which can be easily reconfigured.

BLACK COMEDY
A comedy play with a distinctly disturbing quality. It may have a macabre theme, or relate to the more unpleasant side of life. Also a play by Peter Shaffer with unusual lighting requirements.

BLACK HOLE
Accidentally unlit portion of the stage.

BLACK LIGHT/BLACKLIGHT
See ULTRA-VIOLET.

BLACKOUT / BO / B.O.
1) Complete absence of stage lighting. Blue working lights backstage should remain on and are not usually under the control of the board, except during a Dead Blackout (DBO), when there is no onstage light. Exit signs and other emergency lighting must remain on at all times.
2) The act of turning off (or fading out) stage lighting (e.g. 'This is where we go to blackout')

BLACKS
1) Black clothing worn by stage management during productions.
2) Any black drapes or tabs, permanently or temporarily rigged. Used for masking technical areas.

BLACKWRAP
(Trade Name) Thin black aluminium product which is used to temporarily mask light coming out of a luminaire's body, or to control spill. A self-adhesive tape version is also available.

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 THROUGH
Transformation from a scene downstage of a gauze to another scene upstage, by slowly crossfading lighting from downstage to upstage. If a gauze is lit steeply, or from the sides, it will appear solid. If this light is turned off and light added to the set upstage of it, it will disappear.

BLEEDING
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.

BLIND PLOTTING
The facility on some lighting control desks for the operator to make changes to the plot, without affecting the state on stage.

BLINDERS
Lamps arranged around the stage directed into the auditorium, originally to prevent spectators seeing the stage during scene changes when the house tabs were not lowered. Now used for effect in rock concerts etc.

BLOCK
Frame in which one or more pulley wheels (sheaves) are mounted.

BLOCK PULLEY
TO BE DEFINED.

BLOCKING
The process of arranging moves to be made by the actors during the play, recorded by stage management in the prompt script. Positions at the start of scenes are noted, as are all movements around the stage (using terms such as 'Gardener X DSL' meaning the Gardener crosses to downstage left.)
Blocking Notation

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

BLUES
Blue lights used backstage in a performance situation. See also working lights.

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'.

BO'SUN'S CHAIR
A small seat or cradle rigged on a rope over a pulley whereby a technician may be hoisted to work at an otherwise inaccessible position.

BOARD
The main control for the stage lighting. Originally known as the switchboard or dimmerboard, it is now usually remote from the dimmers. The lighting operator for a show is said to be 'on the board', and is sometimes known as the 'board op'.
Known in the US as the Light Board.

BOARDS
Slang term for the stage floor. (e.g. 'How long have you been treading the boards?').

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

BOOK
1) See PROMPT BOOK.
2) The action of opening or closing a BOOK FLAT.
3) The non-sung text of a musical is known as the Book. The sung text is called the Libretto.

BOOK FLAT
Two-fold piece of scenery. Book flats are free-standing when angled open, allowing quick setting and compact storage. Booking describes the action of opening or closing a book flat.

BOOM
1) Vertical scaffolding pole (usually 48mm diameter) on which horizontal boom arms can be mounted, carrying lanterns. Often used behind wings for side-lighting etc. Booms have a base plate (known as a TANK TRAP) or stand at the bottom and are tied off to the grid or fly floor at the top (not always necessary for short booms). Booms can also be fixed to the rear of the procenium arch (Pros. Boom) or hanging from the ends of lighting bars. Sometimes known in the US as a light tree. A light tree mounted upstage of a Tormentor is known as a Torm Tree.
2) An arm mounted on a microphone stand.

BOOM ARM
See BOOM.

BOOM BASE
A wooden board with vertical scaffold tube adaptor used as a base for lighting booms. Although the base provides a degree of support (especially with added brace weights) booms often require additional support from above.
Sometimes known as a TANK TRAP, as it's very hard to drive a tank over a boom base?

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

BOOTH
(US) Control Room.

BORDER
A narrow horizontal masking piece (flattage or cloth), normally of neutral colour (black) to mask the lighting rig and flown scenery from the audience, and to provide an upper limit to the scene. Often used in conjunction with LEGS.

BOSS PLATE
Metal plate fixed to the stage floor into which a bolt can be screwed for fixing scenery.

BOTTLESCREW
(Also Bottle Strainer, Barrel Strainer) Threaded device which is used to tension a wire, or to provide an adjustable link in a cable, to fine-tune the height of flown scenery. (Known in the USA as a Turnbuckle)

BOUNCE
1) Diffuse light that has been reflected from the stage, walls, cyclorama etc.
2) 'Bounce' is sometimes used for a flat (non-curved) cyclorama. Strictly, a bounce is a white or light blue cloth onto which light is bounced to backlight another cloth. A bounce doesn't need to be seamless, whereas a cyclorama should be.
3) Describes the fast in/out movement of 'bouncing' flown house tabs, used during curtain calls. This can also apply to the fast blackout/lights up cues that happen at curtain calls.
4) This facility is available on many multitrack tape machines. Describes the mixing down of multiple sounds from different tracks onto one track, hence freeing up the other tracks to be re-used. Allows many sounds to be recorded onto one tape.

BOUNDARY MICROPHONE
A microphone mounted on a flat plate which acts as a reflective surface directing sound into the mic capsule. Used for general pick-up over a large area. A PZM (Pressure Zone Microphone) is an omnidirectional boundary mic for picking up sound from all around. A PCC (Phase Coherent Cardoid) picks up only from in front of the microphone.
See also THREE TO ONE RULE and COMB FILTERING.

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.

BOWLINE
Most riggers' knot of choice. Secure and easy to undo after heavy loading.
Submitted by Chris Higgs

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 OFFICE
Part of the theatre front of house area where audience members can buy tickets. Most Box Offices are now computerised, and offer phone reservations. Some offer online (internet) bookings also.

BOX SET
Naturalistic setting of a complete room built from flats with only the side nearest the audience (the fourth wall) missing.

BOX TRUSS
See TRUSS.

BRACE
1) Angled strengthening timber within a flat.
2) Support for scenery (flattage) on stage
  2a.) Extendible, hooking into a screw eye on the flat and being weighted to the floor (commonly known as a 'Stage Brace')
  b. French, right-angled non adjustable triangular frame, made from timber, and attached to the flat with pin hinges. Often swung flush to the flat for storage or flying.
See also Jack (US for Brace).

BRACE WEIGHT
Slotted cast iron weight placed on foot of extendible or French brace to prevent movement. Often referred to as a 'Stage Weight'

BRAIL
A horizontal rope, wire or chain attached at either end of a piece of scenery or lighting bar pulling it upstage or downstage of its naturally hanging position to allow another flying item to pass, or to improve its position. See also BREAST LINE.

BREAK A LEG
A superstitious and widely accepted alternative to 'Good Luck' (which is considered bad luck). More available at the link below.
More on Break A Leg

BREAKAWAY
Prop or item of furniture designed to break/shatter with impact. Breakaway furniture and some props are usually capable of restoration to be 'broken' again.

BREAKOUT
A connection at the end of a multicore cable which allows the connection of many items to it. (e.g. there is a breakout box at the end of a sound multicore cable which allows you to plug microphone cables into it).

BREAKUP
A commonly used abstract GOBO which gives a textured effect to the light, without throwing a specific pattern onto the stage. Used to add interest to light beams. A leafy breakup is used for outdoor scenes / forests / spooky wood etc. to break up the light on the actors faces.

BREAST LINE
A form of brail running horizontally across the width of the stage, passed across the fly bars suspension lines and attached at the fly floors to brail the scenery up or down stage.

BRECHT / BRECHTIAN*
TO BE DEFINED

BRIDGE
A walkway, giving access to technical and service areas above the stage or auditorium, or linking fly-floors. See also CATWALK.

BRIDGE LIFT
An elevator which raises and lowers sections of the stage floor, usually by electrical or hydraulic means.

BRIDGING
Technique for getting more power out of a stereo amplifier by feeding it a mono input signal and then connecting the outputs together. The amplifier is said to be 'BRIDGED'. Check the owner's manual of the amplifier before trying this. Some amplifiers have a switch which does the bridging internally.

BRIDLE
1) A vee-shaped arrangement of lifting equipment or rigging materials that enable load to be spread or shared between the 'legs' of the bridle. Also, to reduce structural spans between suspension lines by creating such 'vees' at pick up points on the structure, or an assembly arranged to create a lifting point where required between two or more structural points.
2) The steering device on a horse.
Submitted by Chris Higgs

BRIGHTNESS
TO BE DEFINED.

BSI
British Standards Institute.

BUBBLE
1) (especially TV and Film) Jargon for a replacement lamp.
2) The glass part of a lamp.

BUILD
1) During lighting plotting, to construct a state from blackout, or to add to an existing state.
2) An increase in light or sound level. See CHECK.
3) A period of set construction ('The Build').

BULB
See 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

BULLET
American device (from the overhead power distribution industry) that grips a wire rope by spring-loaded 'collet' jaws.Not designed for supporting weight.
Submitted by Chris Higgs

BUMP
A flash or sudden jump in light level (a snap cue) (see also FLASH BUTTON).

BUMP CUE
A lighting cue that instantly bumps the lighting up to a brighter level. Usually at the end of a musical number to draw the applause.

BUMP IN
See GET IN.

BUMP OUT
See GET OUT.

BUNRAKU
Style of Japanese puppetry where the puppet operator carries the puppet onstage and is visible throughout the performance. The puppeteers are highly skilled and respected in Japan, and provide the voice as well as the movements for the incredibly detailed puppets.
About Bunraku

BURLAP
Sackcloth hessian, used as softening under steel wire rope slings. It's used because it's flexible and easy to use, and will not cause injury when dropped.
Submitted by Chris Higgs

BURNT OUT
A coloured gel that has lost its colour or melted through due to excessive heat in front of a lantern. Dark blues and greens etc. are most susceptible, and may need replacing during a long run.

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.

BUSINESS
A piece of unscripted or improvised action, often comic in intention, used to establish a character, fill a pause in dialogue, or to establish a scene. An author may simply suggest 'business' to indicate the need for some action at that point in the play.

BUSS
A signal line within a sound mixing desk that can receive its signal from a number of sources. eg the Aux 1 buss carries the signals from the input channels to the Aux 1 Send master control.

C CLAMP / C-CLAMP
US equivalent of the UK Hook Clamp. Requires a spanner/wrench to tighten. Known as a PARROT CLAMP in the US film business.

C-WRENCH
US for SPANNER. (Abbreviation of Crescent Wrench).
See CRESCENT WRENCH

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
Wiring, temporarily rigged, to carry electrical current. Depending on the size of the cable (current carrying capacity), cables are used to supply individual lanterns, whole dimmer racks, or carry signals from a microphone etc.

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

CABLE TIE
Lockable (and sometimes releasable) plastic strap used to tie a bundle of cables together, amongst many other things.

CAD
Computer-Aided Design. Using a computer to help with 2D plans and drawings, or increasingly for 3D visualisation of how a set will look, and how lighting will affect it. See also WYSIWYG.

CALL
1) A notification of a working session (eg a Rehearsal Call)
2) The period of time to which the above call refers. (eg 'Your call for tomorrow nights show is 6.55pm')
3) A request for an actor to come to the stage because an entrance is imminent (these are courtesy calls and should not be relied on by actors - eg 'This is your call for the finale Mr Smith and Miss Jones')
4) An acknowledgement of applause (eg Curtain Call)
5) The DSM on the book is said to be 'calling the cues'.

CALLING THE SHOW
The process of giving verbal cues to the lighting, sound, fly operators and stage crew during the performance. Usually done from the prompt corner by the DSM or Stage Manager over cans.

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.

CAN
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.

CANS
1) Headset earpiece, microphone and beltpack used for communication and co-ordination of technical departments during a performance. (e.g. 'Electrics on cans', 'Going off cans', 'Quiet on cans!' ).
The common system in the UK is produced by Canford Audio under the TechPro brand. In the USA, ClearCom is commonly used.
2) Any headphones.
3) Short for PARCANs.

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

CANVAS
Used to cover flats as a less heavy alternative to plywood.

CAPACITANCE*
TO BE DEFINED

CARABINER
Spring-loaded clip device used by climbers and also in stage rigging.
Named after the carbine gun which had a spring loaded gate.

CARDOID
See PICK-UP.

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

CARPET CUT
A narrow concealed slot along the front of the proscenium stage for clamping the downstage edge of a floorcloth. Becoming obsolete.

CARTRIDGE
A tape loop in a box which can cue itself up to the beginning of the recorded track in a cartridge player. Previously used extensively for radio jingles, and sometimes for theatre sound effects, but now superceded by Minidisk.

CASSETTE
Originally, Compact Cassette. Popular domestic 1/8' tape format. Difficult to cue up accurately, so awkward for live theatre, but cheap, so often used by small scale touring companies as sound effects source. A different cassette is used for each effect. However, Minidisk prices are coming down to the extent that cassettes are rarely used for sound effects now.

CAST
The members of the acting company.

CAST LIGHTING
Canadian creators of WYSIWYG software.
Cast Lighting website

CASTING
The process of the director choosing actors to perform the characters in the play.

CASTORS
The wheels on a TRUCK or underneath a REVOLVE.

CASUALS
Part-time temporary technicians (paid by the hour).

CATENARY
Horizontal wire rope under tension (from the Latin 'catena' meaning a chain, the curve associated with a horizontally stretched chain length which is impossible to straighten due to it's self weight).
Submitted by Chris Higgs

CATHARSIS
A catharsis occurs when a moment of high tragedy at the emotional climax of a play is followed by an emotional cleansing for the characters and the audience.

CATWALK
An access walkway to equipment. Unlike a BRIDGE, not necessarily across a void.

CD (Compact Disc)
Digital sound storage medium introduced in 1982. Provides a high quality source of music, sound effects etc. Also used as a playback medium for sound effects etc by large theatres with long running shows, although CDR (Recordable CD) is becoming more affordable by the day.

CENTRE LINE
Imaginary line running down the stage through the exact centre of the proscenium opening. Marked as CL on stage plans. Normally marked on the stage floor and used as a reference when marking out or assembling a set.
Known in the US as CENTER LINE.
See also SETTING LINE.

CENTRE STAGE
The middle portion of the stage - has good sightlines to all seats of the auditorium.

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.

CHAIN POCKET
Fabric pocket along the width of the bottom of a cloth or tab holding a chain which weighs the bottom of the cloth down.

CHANNEL
A complete control path for signals in lighting or sound equipment.
In a lighting desk, the channels are directly controllable by the lighting operator. Within the desk, the channels are 'patched' to a dimmer or dimmers which the desk then sends a signal to depending on the level of the channel.

CHAPERONE
Adult who takes responsibility for a group of young people while they're away from their parents. A legal requirement when working with children (and a relief for the stage management team!)

CHARACTER
TO BE DEFINED

CHASE
A repeated sequence of changing lighting states. A chase can be produced easily by the effects functions of a computerised lighting desk. There are standalone units designed to chase lighting circuits electronically in time to music (sound to light) or mechanically as a repeated sequence (as used in early neon signs).

CHEAT
An actor movement (or lighting change) which happens without the audience being aware of it.

CHEAT SHEET
A smaller version of the lighting plan, used by the lighting designer during the lighting plot. Also known as a Dimmer Layout or Magic Sheet.

CHECK
1) Opposite of Build; a smooth diminishment of light or sound level (e.g. Lighting: 'I think we should check this state down a touch as the song begins')
2) See Prefade Listen.

CHEWING THE SCENERY
An actor who gives a completely hammy and over-the-top performance is said to be Chewing the Scenery.
See the link below for more.
More about Chewing the Scenery

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.

CHIEF ELECTRICIAN
The senior member of the theatre's stage lighting team, although not necessarily the lighting designer. Known in the US as MASTER ELECTRICIAN.
In common with many theatre jobs, the actual duties of the Chief Electrician vary from theatre to theatre. Some chiefs are responsible for electrical maintenance of the building, some design the lighting for nearly every in-house production, some design no lighting at all, some have a team of eight staff under them, some have two. Many theatres employ casual staff to assist on lighting rigging sessions. Some theatres have a separate sound department, smaller venues have the lighting team also running sound for shows (and doing sound design for some).

CHINAGRAPH PENCIL
Usually white, wax-based pencil used for marking magnetic tape prior to splicing. Also used for marking identifying numbers on lighting gels.

CHOKE
Rigging term: A slinging pattern made by passing one end of a sling through the opposite end's eye or by making a 'lark's head' loop with an endless sling (also CHOKER HITCH (US) or STRANGLE (UK)). Useful, but reduces the SWL/WLL of the sling by 20%.
Submitted by Chris Higgs

CHOOKAS
Australian equivalent to 'Break a Leg'
More on Break A Leg

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

CHORD
The main horizontal member(s) in a truss/lattice structure.
Submitted by Chris Higgs

CHOREGOS
(Greek) Individual paying for the tragic chorus for a performance.

CHOREOGRAPHER
Member of the production team responsible for setting dances and movement sequences during the production.

CHORUS
1) In Greek theatre, a character (or group) representing an element in the drama which comments on the action, and advances the plot.
2) A sound processing effect which adds 'body' to a sound by overlapping a number of slightly delayed versions of the original sound.

CHORYPHAEUS
(Greek) Chorus leader.

CHROMINANCE
TO BE DEFINED.

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

CIRCLE
The balcony with tiered seating above the stalls. Also known as Dress Circle or Grand Circle. See also UPPER CIRCLE.

CIRCLE FRONTS
A permanent front of house lighting position in older proscenium theatres. A number of spotlights, sometimes fitted with colour changers, are recessed into the front of the circle balcony above the stalls. Sometimes known as the Balcony Rail position.

CIRCUIT
1) The means by which a lantern is connected to a dimmer or patch panel. Numbered for reference.
2) A complete electrical 'loop' around which current can flow.

CIRCUIT BREAKER
An electro-mechanical 'fuse' that can be reset, rather than having to be replaced. Available in the same ratings as fuses. See MCB, RCD.

CITT
Canadian Institute for Theatre Technology.
CITT website

CLEANERS
Auditorium working lights. Used for cleaning and setting up the auditorium before the house lights (usually more atmospheric) are switched on.

CLEARANCE
Message passed to Stage Management from the Front of House Manager that the house is ready for the performance to begin. (ie everyone is in their correct seat and there are no coach parties coming through the doors). Announced as 'We have Front of House Clearance'.

CLEARING STICK
A long, often bamboo, rod used to rescue flying objects or to prevent them from becoming entangled.

CLEAT
Piece of timber or metal for tying off a rope line by taking a turn around it, followed by a series of figure eight turns and a locking tuck(s) made in the final turn. Used when flying or for holding scenic pieces together with a cleat line.
Submitted by Chris Higgs

CLEAT LINE
Rope passed through cleats on two adjacent flats alternately to hold the flats together.

CLEW
A ring of metal which is used to join several flying lines or wires to a single pulling wire.

CLICK TRACK
Technique for reinforcing the live sound of a musical or band with recorded sound from one track of a tape. The other track of the tape consists of a click used by the musical director to keep the live band and cast synchronised with the recorded band or cast.

CLIMAX
The significant moment in the plot of a play, when things change, or reach a crisis point.

CLIPPING
Distortion in a sound signal caused by an amplifier or mixer being unable to handle the level of signal being fed to it.

CLOTH
A piece of scenic canvas, painted or plain, that is flown or fixed to hang in a vertical position.
A Backcloth (or Backdrop) hangs at the rear of a scene.
A Floorcloth is a painted canvas sheet placed on the stage floor to mark out the acting area, or to achieve a particular effect.
A Frontcloth hangs well downstage, often to hide a scene change taking place behind.
Cut cloths have cut-away open areas and are normally used as a series, painted in perspective.
A Star Cloth (also Star Drop or Starcloth) (usually black) has a large number of small low-voltage lamps sewn or pinned through it which gives a magical starry sky effect. (See also FIBRE OPTICS).
In the US, a cloth is known as a Drop (from backdrop).

CLOVE HITCH
Invaluable knot that every technician should know.

CLUSTER
Generic name for a grouping of loudspeakers hung in a performance space. (e.g. The central cluster). Also known as ARRAY.

CLUTCH
1) Purpose designed 'chain system' forging that allows a link of sling chain to be grabbed in order to shorten the reach or length of the chain. The forging ensures the 'grabbed' link is correctly loaded and no link is trapped or damaged.
2) A sailing term for a device that grips a control line or sheet in a modern rigging design.
Submitted by Chris Higgs

CM / C.M.
Manufacturer. (Columbus McKinnon Corporation.) American manufacturer of lifting equipment, including the Lodestar chain hoist range and STAC chain used in entertainment rigging.
Submitted by Chris Higgs

CMY
Cyan / Magenta / Yellow - the three secondary (additive) colours of light which are used in moving lights for colour mixing. Some cheaper systems use three graduated colour scrolls (one of each colour) in front of a standard fixture, but these take a massive amount of intensity out of the beam, resulting in a dim light on stage. Many moving lights use a similar system with dichroic colours which are more efficient and longer-lasting.

COLOR
See COLOUR FILTER.

COLOUR
See COLOUR FILTER.

COLOUR CALL
A list compiled from the lighting plan of all the colours needed for the rig, and their size. This term also applies to the act of preparing colour filters and frames from such a listing.

COLOUR CHANGER
1) Scroller, where a long string of up to 16 colours is passed horizontally in front of a lantern. Remotely controlled by the lighting desk. Some scrollers have cooling fans to prolong the life of the gel string. Stronger colours will burn out faster without cooling, or if the focus of the beam is concentrated on the gel. If colours aren't lasting very long in scrollers, try changing the focus of the lantern. HEAT SHIELD clear gel should be used between the lens and the colour scroller to absorb some of the heat.
2) Wheel : Electrically or manually operated disc which is fitted to the front of a lantern with several apertures holding different colour filters which can be selected to enable colour changes. Can also be selected to run continuously.
3) Semaphore, where framed colours are electrically lowered into place in front of the lantern. Remotely controllable. Can perform additive colour mixing by lowering two colours into position at the same time.
4) Magazine : Manual semaphore-type device used on the front of a followspot. Known in the USA as a BOOMERANG.

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.

COLOUR FILTER
A sheet of plastic usually composed of a coloured resin sandwiched between two clear pieces. The coloured filter absorbs all the colours of light except the colour of the filter itself, which it allows through. For this reason, denser colours get very hot, and can burn out very quickly. There are a number of manufacturers of Colour Filters - Lee (UK), Rosco (US), Gam (Great American Market - US) and Apollo (US) are some of the more popular. Each manufacturer's range has a numbering system for the different colours. It's important to specify which range you're talking about when quoting numbers.
A colour filter is sometimes known as a Gel, after the animal material Gelatine, from which filters were originally made.
Lee Filters website
Rosco website
GAM website
Apollo Design Technology website

COLOUR FRAME
(or Gel Frame) A frame which holds the colour filter in the guides at the front of a lantern. Many different sizes of frames are needed for the different lanterns.

COLOUR MIXING
Combining the effects of two or more lighting gels:
1) Additive : Focusing two differently coloured beams of light onto the same area (eg Cyc Floods). Combining colours in this way adds the colours together, eventually arriving at white. The three primary colours additively mix to form white, as do the complementary colours.
2) Subtractive : Placing two different gels in front of the same lantern. Subtractive mixing is used to obtain a colour effect that is not available from stock or from manufacturers. Because the ranges of colour are so wide, the need for subtractive mixing is reducing. Combining colours in this way reduces the light towards blackness. The three primary colours mix subtractively to form black (or to block all the light).
More on Colour Mixing

COLOUR SCROLLER
See COLOUR CHANGER.

COLOUR TEMPERATURE
A measure of the 'warmth' or 'coolness' of light sources and colours. Measured in degrees Kelvin. A higher colour temperature light source will appear whiter (colder). The human brain automatically compensates for different colour temperatures - a film or video camera cannot, and thus what we see as white may appear to have a blue or green tint when no colour correction is used for video. Most video cameras have a 'White Balance' control to make colour temperature adjustments, to ensure white looks white on camera.
Daylight is approximately 5600°K, Tungsten Halogen is approx. 3200°K and standard incandescent lamps are 2800°K. Many discharge light sources are in use in modern theatrical productions using discharge followspots or moving lights - colour correction filters are used to balance the colour temperatures.
See also COLOUR CORRECTION.

COLOUR WHEEL
See COLOUR CHANGER.

COMB FILTERING
An effect caused by the same sound arriving at a given point at slightly different times. This could be the listening position or a microphone. Comb filtering can be reduced in the case of sound from speakers by employing delays, and in the case of microphones by following the three to one rule. See THREE TO ONE RULE and DELAY.

COME ALONG
A lever hoist or tackle set designed for tensioning of pulling, particularly associated with catenary wire and guy rope rigging.
Submitted by Chris Higgs

COME DOWN
The time the show finishes (e.g. 'What time does the show come down this evening?') This relates to the curtain coming down at the end of the show. See also GO UP.

COMEDY
TO BE DEFINED

COMIC RELIEF
A comic scene (or line) included in an otherwise straight-faced play to provide a relief from tension for the audience.

COMMEDIA DELL'ARTE
Italian comic form - started in the Renaissance, and still has massive influence today. A range of stock characters (Harlequin, Captain, Doctor, Pantaloon, Zanni, the Lovers etc.) were represented by stylized masks. Each character had a series of comic 'lazzi' (business). The performances were based on the pre-rehearsed lazzi, but were largely improvised.
Commedia website

COMP
Short for Complimentary ticket. Free of charge ticket issued to company members or special guests. Each venue has their own policy about numbers of comps that cast / crew may be entitled to. There are often House Comps, which are good seats not sold to the public until others are sold out, which are used for VIP guests.

COMPANDER
Outboard sound equipment. Combination of a COMPRESSOR and an EXPANDER.

COMPANY
The cast, crew and other staff associated with a show.

COMPANY MANAGER
In a touring theatre company, the Company Manager is responsible for the well-being of the cast and crew of the show; ensuring their arrival at the venue, dealing with their payments, dealing with any disputes, and generally ensuring all is well and happy. The CM is also the representative of the producers in that he/she is responsible for collecting payments from the venue management.
In a building-based theatre company, the role is more administrative, dealing with payroll and other matters connected with the cast and crew of the current production(s).

COMPLEMENTARY COLOURS
Pairs of colours which, when additively mixed, combine to produce white light. Examples are red + cyan, green + magenta, and yellow + blue.

COMPOSITE GOBO
See GOBO.

COMPOSITE VIDEO
TO BE DEFINED.

COMPRESSOR
A piece of sound processing equipment that ensures all wanted signals are suitably placed between the noise and distortion levels of the recording medium. It evens out the unwanted changes in volume you get with close-miking, and in doing so, adds punch to the sound mix. A Limiter is used to stop a signal from exceeding a preset limit. Beyond this limit, the signal level will not increase, no matter how loud the input becomes. A Limiter is often used to protect speaker systems (and human ears) by preventing a system from becoming too loud.

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

CONCESSION
1) (UK) A reduction in ticket price given to some eligible patrons (e.g. unemployed, students)
2) (US) A merchandising stand in the foyer of the theatre. ('The concession stand').

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).

CONDENSER MIC
(Capacitor Mic) A microphone that uses the varying capacitance between two plates with a voltage applied across them to convert sound to electrical pulses. Condenser microphones need a power supply to provide the voltage across the plates, which may be provided by a battery within the case of the microphone, or it may be provided from an external phantom power supply. A condenser mic is more sensitive and has a faster reaction to percussive sounds than a Dynamic mic and produces a more even response. See Electret Mic.

CONDUCTOR
The director of an orchestra. See also MUSICAL DIRECTOR.

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.

CONFLICT
TO BE DEFINED

CONSTANT VOLTAGE SYSTEM
See HUNDRED VOLT LINE.

CONTACT MIC
A microphone that directly picks up the sound transmitted by a solid material. See Boundary Mic, PCC, PZM.

CONTACT SHEET
1) A list of names and contact details (phone numbers, addresses) for cast and crew.
2) A sheet showing all of the frames from a roll of film to enable a choice to be made about which to enlarge properly.

CONTRAST
TO BE DEFINED.

CONTROL ROOM
Room at the rear of the auditorium (in a proscenium theatre) where lighting and sometimes sound is operated from. Known in the US as the BOOTH. The stage manager calling the cues is very often at the side of the stage (traditionally stage left) but in some venues he/she may be in the control room also. The control room is usually soundproofed from the auditorium so that communications between operators cannot be heard by the audience. A large viewing window is obviously essential, as is a 'show relay' system so that the performance can be heard by the operators. Obviously if sound is being mixed, the operator should be able to hear the same as the audience, so some control rooms have sliding or removable windows, or a completely separate room for sound mixing. Where possible, the sound desk is moved into the auditorium so that the operator can hear the same as the audience.
Also known as the BOX.

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

COOKIE
See GOBO.

CORNER PLATE
A triangle of plywood used to strengthen the corners of a flat.

CORPSING
An actor who collapses into uncontrollable laughter during a rehearsal or performance is said to be Corpsing. There are numerous ways of covering the laughter, mostly involving the actor turning away from the audience and covering his mouth with his hand.

COSTUME DESIGNER*
TO BE DEFINED.

COSTUME FITTING
First meeting between the actor and his/her costume. Enables wardrobe staff to ensure a correct fit, and to enable the actor to see if all necessary movement is possible.

COSTUME LOFT
TO BE DEFINED

COSTUME PARADE
See DRESS PARADE.

COSTUMER
Member of the WARDROBE Department. See also DRESSER.

COSTUMES
Clothes worn by the actors onstage. The responsibility of the WARDROBE DEPARTMENT.

COUNT
A measure of time used to add space between cues (for example, LX cue 12 goes on a count of 3 after the actor sits down).

COUNTER RAKE
See ANTI RAKE.

COUNTERWEIGHT
A standard weight (60 or 30 lb.) used in a counterweight flying system.

COUNTERWEIGHT SYSTEM
Method of flying scenery which uses a cradle containing weights to counterbalance the weight of flown scenery. See Double Purchase, Single Purchase, Flying.

COUR
From the French coté cour meaning Stage Left.
Derivation of Court & Garden

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

CP
Lighting Industry Forum code which identifies the (original) recommended usage of different lamp types. CP coded lamps are for Film, Television and Photographic studio use and have a colour temperature of 3200°K. See also A1, T, P2, K.

CRACKED OIL
A smoke effect which creates a haze in the air to make light beams visible. This effect is rarely used now, because it has been found to be carcinogenic. See Water Cracker.

CRADLE
Metal frame in which counterweights are carried in a flying system. Known in the US as an Arbor. See also SINGLE PURCHASE and DOUBLE PURCHASE.

CRASH BOX
Sealed metal box filled with broken crockery which can be dropped or thrown offstage to simulate breaking glass / damage etc.

CRESCENT WRENCH
(US) A open ended adjustable hand wrench originally produced by the Crescent Tool Co. Known as a C-WRENCH.

CRITIC
Journalist who writes reviews for theatre productions.

CROSBY
Manufacturer of shackles and lifting hardware (US, Canada and Belgium)
Crosby Group website
Submitted by Chris Higgs

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

CROSS FADE
Bringing another lighting state up to completely replace the current lighting state. Also applies to sound effects / music. Sometimes abbreviated to Xfade or XF.

CROSSOVER
1) A route leading from one side of the stage to the other, out of the audiences view.
2) An electronic filter in a sound system that routes sound of the correct frequency to the correct part of the speaker system. Different speakers handle high frequencies (tweeters) and low frequencies (woofers). Sometimes known as a crossover network.
An active crossover splits the signal from the mixing desk into high, mid and low frequencies which are then sent to three separate amplifiers.

CROSSTALK
A leakage between two audio circuits (e.g. between two channels on a sound mixer).

CROWN
Manufacturer of PA amplifiers and microphones.
Crown website

CRT
Cathode Ray Tube. Refers to a TV/monitor using a traditional tube (rather than a TFT / flat design)

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.

CSM
Company Stage Manager

CUE
1) The command given to technical departments to carry out a particular operation. E.g. Fly Cue or Sound Cue. Normally given by stage management, but may be taken directly from the action (i.e. a Visual Cue).
2) Any signal (spoken line, action or count) that indicates another action should follow (i.e. the actors' cue to enter is when the Maid says 'I hear someone coming! Quick - Hide!')

CUE LIGHT
System for giving technical staff and actors silent cues by light. Cue lights ensure greater precision when visibility or audibility of actors is limited. Sometimes used for cueing actors onto the set. For technical cues, lights are normally now used just as a backup to cues given over the headset system. In the UK, a flashing Red light means stand-by or warn, green light means go. The actor / technician can acknowledge the standby by pressing a button which makes the light go steady. In the US, a red light means warn, and when the light goes off, it means GO. The UK system seems to be more secure, but it depends what you're used to.

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.

CUE TO CUE
('Topping and Tailing') Cutting out action and dialogue between cues during a technical rehearsal, to save time.

CUEING
There is a standard sequence for giving verbal cues :