Glossary
Audio Visual Glossary
acoustics – the science of sound wave behaviour in air.
ambient light – all light in a viewing room produced by sources other than the display.
ambient noise – sound that is extraneous to the intended , desired, intentional, audio; background noise.
amplifier – an electronic device for increasing the strength of electrical signals.
analogue – a method of transmitting information by a continuous but varying signal.
ANSI – American National Standards Institute.
aperture – an opening in a lens regulating the amount of light passing through the lens to the imager.
aspect ratio – the ratio of image width to image height (typically widescreen or standard).
audio processor – an electronic device used to manipulate audio signals in some manner.
audio signal – an electrical representation of sound.
bandwidth – a measure of information carrying capacity without distortion.
BNC – a professional type of video connector featuring a two-pin lock.
boundary microphone – a microphone that relies on reflected sound from a surrounding surface.
category 5 (Cat 5) – the designation for 100-ohm unshielded twisted-pair cables and associated connecting hardware whose characteristics are specified for data transmission up to 100 Mb/s. (Part of the EIA/TIA 568A standard.)
CODEC – an acronym for coder/decoder. An electronic device that converts analog signals, such as video and audio signals, into digital form and compresses them to conserve bandwidth on a transmission path.
component video – colour video in which the brightness (luminance) and colour hue and saturation (chrominance) are handled independently. The red, green and blue or, more commonly, the Y, R-Y, B-Y signals are encoded onto three wires. Because these signals are independent, processing such as chroma keying is facilitated.
composite video signal – the electrical signal that represents complete color picture information and all synchronization signals, including blanking and the deflection synchronization signals to which the colour synchronization signal is added in the appropriate time relationship.
compression – the action of the air molecules moving closer together permitting audible sound.
compressor – a compressor controls the overall amplitude of a signal by reducing that part of the signal which exceeds an adjustable level (threshold) set by the user. When the signal exceeds the threshold level, the overall amplitude is reduced by a ratio, also usually adjustable by the user.
condenser microphones – also called a capacitor microphone, it transduces sound into electricity using electrostatic principles.
cone – most commonly used component in a loudspeaker system and found in all ranges of drivers.
conferencing systems – the technology by which people separated by distance come together to share information. Conferencing systems may include projection, monitor displays, computers, satellite connections video and audio playback devices, and much more.
DA – (see distribution amplifier)
decibel – a comparison of two measurements or values. Abbreviated dB, it is one-tenth of a Bel (a unit of measurement named for Alexander Graham Bell).
delay – an audio signal processing device or circuit used to retard the speed of transmission on one or more audio signals or frequencies.
digital – a method of transmitting information by discrete, non-continuous impulses.
digital-to-analog converter – an electronic device that converts digital signals into analog form.
distribution amplifier – an active device used to split one input into multiple outputs, while keeping each output isolated, and the signal level constant.
document camera – an imaging device used to create a video image of printed documents or three-dimensional objects.
DVI – Digital Visual Interface; a connection method from a source (typically a computer) and a display device that can allow for direct digital transfer of data. The digital signal is limited to 5 meters.
electromagnetic interference (EMI) – an electrical disturbance caused by an electromagnetic field, either low frequency or radio frequency (RF).
EMI – (See electromagnetic interference.)
encoded – a signal that has been compressed into another form to reduce size or complexity, as in a composite video signal.
equalizer – electronic equipment that adjusts or corrects the frequency characteristics of a signal.
equipment rack – a centralized housing unit that protects and organizes electronic equipment.
feedback – 1. unwanted noise caused by the loop of an audio system’s output back to its input. 2. in a control system, data supplied to give an indication of status, i.e., on or off.
fibre optic – a technology that uses glass or plastic threads or wires to transmit information.
focus – the act of adjusting a lens to make the image appear clear, sharp, and well-defined.
footprint – 1. indicates where possible mounting points are to join two pieces together, the total contact area, and how they may or may not fit together. 2. space required to house an equipment rack or device. 3. coverage area of a communications satellite.
frequency – cycles per second, expressed in Hertz (Hz) or the number of cycles in a given time period.
frequency response – the range of frequencies within which a microphone is sensitive.
gain – 1. electronic signal amplification. 2. the ability of a projection screen to concentrate light.
gate – an audio processor that allows signals to pass only above a certain setting or threshold.
harmonics – higher frequency sound waves that blend with the fundamental frequency.
HDTV – High Definition Television.
hertz (Hz) – cycles per second of an electrical signal.
horns – loudspeakers that reproduce mid to high frequencies.
IP (internet protocol) – standard networking protocol, or method, which enables data to be sent from one computer or device to another over the Internet.
keystone – the trapezoidal distortion of a square-cornered image due to the optical effect of the projection device not being located in its proper position in respect to the screen.
LAN (local area network) – a computer network limited to the immediate area, usually the same building or floor of a building.
lavalier – a small microphone designed to be worn either around the neck or clipped to apparel.
LCD – Liquid Crystal Display.
LED – Light Emitting Diode.
limiter – audio signal processor that functions like a compressor except that signals exceeding the threshold level are reduced at ratios of 10:1 or greater.
loudspeaker – a transducer that converts electrical energy into acoustical energy. Loudspeaker components are primarily a driver within an enclosure.
lumen – a measure of the light quantity emitted from a constant light source across one square meter.
lux – a contraction of the words luminance and flux; metric version of footcandle.
matrix switcher – an electronic device with multiple inputs and outputs, the matrix allows any input to be connected to any one, several, or all of the outputs.
midrange – loudspeakers that reproduce midrange frequencies, typically 300 Hz – 8,000 Hz.
mixer – device for blending multiple audio sources.
omni-directional – describes the shape of the area for microphones that have equal sensitivity to sound from nearly all directions.
operating system (OS) – platform; enables software applications to communicate with the CPU.
overhead projector – a device which produces an image on a screen by transmitting light through transparent acetate placed on the stage of the projector
PAL – Phase Alternate Line; the video standard for much of Europe and Australia.
peak – the highest level of signal strength, determined by the height of the signal’s waveform.
peaking – an adjustment method that allows compensation for high frequency loss in cables.
phantom power – a direct current (DC) power source available in various voltages.
phase – the relative timing of one signal to another.
phono – the European name for an RCA connector.
radio frequency (RF) – generally refers to signals such as radio and TV broadcast signals, or radio
radio frequency interference (RFI) – tendency of a radio transmission to interfere with other electronic signals. Radio frequency energy is radiated by all electrical equipment – when it is a strong enough signal it becomes interference in audio systems.
RAM – Random Access Memory; the most common computer memory used by programs to perform necessary tasks while the computer is on; an integrated circuit memory chip allows information to be stored or accessed in any order and all storage locations are equally accessible.
RCA – a connector most often used with line level audio signals; also known as a phono connector.
rear screen projection – a presentation system in which the image is projected through a translucent screen toward the audience; projecting an image through a translucent screen material for viewing from the opposite side, as opposed to front projection.
resolution – 1. the amount of detail in an image. 2. the number of picture elements (pixels) in a display.
reverberant sound – sound waves that bounce off of multiple surfaces before reaching the listener, but arrive at the listener’s ears quite a bit later than early reflected sound.
ROM – Read Only Memory; memory whose contents can be accessed and read but cannot be changed. Permanent memory that can only be entered once, normally by a manufacturer; may not be altered or removed.
scaler – feature in a display device that changes the size of an image without changing its shape. Scaling may be required when the image size does not fit the display device.
scan conversion – the process of changing the horizontal scan rate of one device to that of another. Usually used to describe changing the scan rate of a computer to match the television (NTSC/PAL/SECAM) video format for the purpose of recording or viewing on television video equipment.
SECAM – Sequentiel Couleur Avec Memoire (Sequential Color with Memory); the video standard in France.
Speakon(c) – specialized connector used to hook up speakers without causing a short circuit; allows connection of speaker while working, or hot.
splitter – an electronic device that divides a signal into different pieces to route to different devices.
stereophonic – commonly shortened to “stereo”, input from all microphones is split into at least two channels before driving the signal through the loudspeakers.
streaming video and audio – sequence of “moving images” or “sounds” sent in a continuous, compressed stream over the Internet and displayed by the viewer as they arrive. With streaming video or audio, a web user does not have to wait to download a large file before seeing the video or hearing the sound.
subwoofers – loudspeakers that reproduce lower frequencies, typically 20 Hz – 200 Hz.
surface mount microphone – also called a boundary microphone, placed on a table to pick up sound. Used in boardrooms and other environments where a number of talkers must be “picked up” and where the microphone needs to remain unobtrusive.
surround sound – more complex stereo playback systems that use from two to five channels for realistic sound production. The popular term used to describe an experience where the sound ‘surrounds’ you. This is best achieved using surround-encoded material, a receiver, and surround speakers.
S-Video – a video signal, also known as Y/C. Y is the luminance and C is the chrominance. Y and C are transmitted on separate conductors.
switcher – a peripheral or sometimes integrated device used to select one of a group of signals.
sync – shortened form of synchronization; the timing information that keeps images displaying properly.
throw distance – the length of the projection beam necessary for a particular projector to produce an image of a specified size.
time code – a method of numbering video frames according to SMPTE standards; the 8-digit address representing hour, minute, second, and frame, recorded on the videotape’s control track.
tweeters – loudspeakers that have high frequencies, typically 2,000 Hz – 20,000 Hz.
viewing angle – the viewing angle determines how far off the axis (screen centerline) a viewer can still sit and still see a quality image. This is no greater than 45 degrees off the projection axis.
WAN – Wide Area Network; a data communications system that uses telecommunications circuits to link local area networks (LANs) that are distributed over large geographic distances.
white noise – a sound that has the same energy level at all frequencies.
WLAN – Wireless Local Area Network; a network that shares information by radio frequency (RF).
woofers – loudspeakers that have low frequencies, typically 20 Hz – 200 Hz.
XLR connector – a popular type of audio connector featuring three leads: two for the signal and one for overall system grounding. A secure connector often found on high quality audio and video equipment; sometimes called a Canon connector.
Stage Lighting Glossary
Areas - In lighting design, the divided portions of the stage sued to apportion the light.
Batten - A bar made of wood or steel from which scenery, lights, or curtains may be hung and flown in and out. Also called Pipe or fly bar.
Beam Projector - A type of lighting instrument that has no lens, used to emit a powerful beam of light with diffused light.
Black Out - A rapid extinguishing of all light on stage.
Can – or Par Can – a lighting instrument shaped like a coffee can containing a lamp that resembles a round headlamp from an older automobile. Lamp can be rotated 90 degrees to change the throw.
Crossfade - A lighting action in which a particular light cue fades down as the next light cue fades up.
Cue - As a verb, the word may be used by the stage manager, who "cues" all technical personnell either verbally or on a light, and "cues" actors by giving them their line when they have forgotten it.
Cue Sheet - The page(s) used to note the cues given by the stage manager to the different technicians.
Cyc Lights - Type of powerful lighting instruments used to light the cyc with a smooth wash.
Cyclorama or Cyc - A curved drop or wall used as a background to partially enclose the set. Quite often used to depict the sky. May be painted or lit.
Dim - To decrease the intensity of a stage light.
Dimmer - An electrical apparatus used to control the intensity of the lighting instrument to which it is circuited. Found on the lighting board.
DMX – ( Digital Multiplex) is a standard for digital communication networks that are commonly used to control stage lighting and effects.
Flood Lights – a diffused light that gives a comparatively uniform illumination over a rather large given area.
Focus - To direct and lock down a lighting instrument in its specified stage area.
Followspot - A hand-operated lighting instrument mounted on a swivel stand that emits a high intensity beam of light, used to follow an actor on stage.
Footlights - Ground based Striplights used for general lighting. Maybe permanent or mobile.
Fresnel - A type of lighting instrument that emits a soft-edged, diffused light.
Gel - Transparent material used to colour the lights.
Gobo - A metal cutout used in an Ellipsoidal Reflector Spotlight that projects an image on stage. Also
called Template.
Hot Spot - The area of the greatest illumination projected by a lighting instrument.
House Lights - Lights used to illuminate the area where the audience sits.
Instrument - A term used for any lighting device.
Intelligent lights - stage lighting that has automated or mechanical abilities beyond those of traditional, stationary illumination, such as movement, colour, gobos & focus. Although the most advanced intelligent lights can produce extraordinarily complex effects, the intelligence lies with the programmer of the show rather than the instruments or the lighting operator. For this reason, intelligent lighting is also known as automated lighting, moving lights or moving heads
Lamp - The part of a lighting instrument that emits the light; the "light bulb" of the instrument.
LED’s – A light source that is created using light emitting diodes, usually an instrument will comprise 3 sets red, green & blue (RGB) allowing for multiple colour mixing. Some instruments also have Amber, White & UV LEDS as well
Lighting Board - The console that controls all the lighting instruments. Also called the Dimmer Board.
Light Plot - A drawn-up plan that designated the placement of lighting instruments relative to the set.
Lighting Tree - A vertical pipe that is placed on the side of the stage to hold lighting instruments. Also called Boom.
Patch - To connect a circuit to a dimmer
Patch Panel - The board on which one connects circuits to dimmers.
Pre-Set - The setting on stage that the audience sees before the play begins. Refers to lights, set, and
Profile - A type of lighting instrument that emits a hard-edged circle of light. Traditionally known by their brand names (Source 4, Leko etc)
Also called an Ellipsoidal Reflector Spotlight (ERS)
Rigging - The process of putting a lighting instrument in its designated spot according to the light plot/The way in which mobile scenery is controlled.
Run - The total number of performances for a production.
Run-Through - To rehearse the show by performing from beginning to end without stopping.
Scrim - Loosely-woven material that is used as a drop. When lit from the front scrim is opaque, when lit from behind it is transparent.
Spill - Extraneous light that can be cut off with a shutter.
Wash Light - Light used to give a general illumination of the stage; quite often a specific colour is used in awash.
Worklights - Lights used for general illumination of the stage when not in performance.
Theatre Terms Glossary
Acting Area - The area of the stage where the play is performed. Also called the Playing Area.
Apron - Stage area in front of the proscenium.
Arena Stage - A stage in which the audience is seated on all four sides. Also called Theatre in the Round.
Back Drop - A large piece of canvas hung from a batten and painted to represent a particular scenic
element. Also called a Drop.
Backstage - The area away for the acting area, including the dressing rooms and the green room. Also called Offstage.
Blacks - Curtains hung both to mask the backstage area and to shape the onstage area.
Blocking - The movement and business of a actor on stage.
Book Flat - Two flats hinged together in order to be self-supporting when folded on the hinge.
Borders - In scenery, material hung at the top of the set to hide fly system from the audience. Also called Teasers.
Box Set - A set that utilizes three walls to enclose the stage area.
Call - The notification to cast and crew of rehearsal or performance. Also the countdown to curtain
provided by stage management, usually half-hour call, fifteen minute call, five minute call, and places.
Catwalk - An immobile platform above the stage that reaches from one end of the stage to the other, used to gain access to the stage equipment.
Centre Line - An imaginary or real line that divides the stage area into two equal parts, running from
downstage to upstage.
Centre Stage - The Middle of the Performance space.
Counterweight System - A type of rigging that uses weights to counterbalance horizontal battens containing, scenery, curtains, or lighting equipment.
Cue - As a verb, the word may be used by the stage manager, who "cues" all technical personnell either verbally or on a light, and "cues" actors by giving them their line when they have forgotten it.
Cue Lights - Specific lights used by the stage manager to cue backstage technicians and actors. Normally,when turned on functions as a warning and when turned off signals them to GO.
Cue Sheet - The page(s) used to note the cues given by the stage manager to the different technicians.
Cue-to-cue - A technical rehearsal that focuses on getting the physical production caught up with the acting by skipping over scenes or dialogue that have no technical cues in them in order to run the next cue.
Curtain - In addition to it's normal definition relating to draperies, a term used to indicate the start or end of a performance such as "Five minutes to curtain" (five minutes to the start of the performance).
Curtain Line - 1) The line on the stage floor where the front curtain touches when brought in. 2) The final line in the play. Also called the Tag Line.
Cyclorama or Cyc - A curved drop or wall used as a background to partially enclose the set. Quite often used to depict the sky. May be painted or lit.
Deck - The stage level, derived from ship terminology.
Downstage - The area of the stage closest to the audience.
Dresser - Crew person assigned to help with quick changes and general maintenance of costumes
throughout the run of the show.
Dressing A Set - The decoration of the set with items that are principally for aesthetic purposes only.
Dutchman - Thin strips of cloth used to mask cracks between flats. (Sometimes wide masking tape is used).
False Proscenium - A constructed proscenium that fits inside the permanent proscenium.
Fire Curtain - A non-flammable curtain hung directly behind the proscenium that protects the audience from fire or smoke emitting from the stage. May be the same as the Act Curtain. Also called Asbestos Curtain or Fireproof Curtain.
Flat - A covered wooden frame, usually rectangular. (Soft flat is cloth covered, hard flat is covered with thin wood.
Flies - The area above the stage that contains lines to be raised or lowered.
Fly - To lower or raise lines hung from the gird that are affixed with scenery or stage equipment.
Fly Gallery - A platform that runs above the stage on one side, used in the operation of fly lines.
Flyman - Crew person in charge of raising and lowering the flies.
Fourth Wall - An imaginary wall between the actor s and the audience that disallows interaction between the two groups of people.
Grid - A steel framework above the stage from which the fly system is rigged.
Green Room - A backstage room used by actors and crew as a waiting and meeting area.
Ground Cloth - A heavy piece of muslin used to cover the stage floor.
Ground Plan - A scale diagram that shows where the scenery is placed on the stage floor. Also called Floor Plan.
Ground Row - A short piece of scenery, usually self-supporting, placed in front of a backdrop or cyc to mask stage equipment.
Half-Hour - The 30-minute warning to curtain.
House - The part of the theatre where the audience sits.
House Lights - Lights used to illuminate the area where the audience sits.
Instrument - A term used for any lighting device.
Legs - Narrow Curtains or cloth that hang vertically on the sides of the stage to mask the backstage area. Also called Tormentors.
Load-in/out (Bump in/out)- The time a show goes into or out of a theatre. Large crews are usually assembled just for this period.
Masking - To hide any stage equipment or offstage area through the use of curtains, flats, etc.
Paper The House - TO give away free tickets to a performance in order to fill the house.
Pit - The area below the front of the stage. May be used to house the orchestra. Also called Orchestra Pit.
Practical - Any prop or piece of scenery that is usable.
Pre-Set - The setting on stage that the audience sees before the play begins. Refers to lights, set, and props.
Preview - A performance before the official opening; often these are rehearsals with an audience, and a time when new material is tested and tried. (Usually you get a discount for these performances.)
Prompt - To help an actor with his lines when he either asks or is stumbling.
Prompt Script - The notebook kept by the stage manager that contains all paperwork necessary to the production of the play, including a script with blocking and cues. Also called a Prompt Book.
Prop Table - The table backstage on which props are laid out, usually in a mapped out order.
Props or Properties - All objects, except for scenery, used during a play. Categorized into hand props or set dressing.
Proscenium - The outlining frame of the stage opening that separates the house from the stage. Also called the Proscenium Arch.
Quick Change - A fast costume change.
Raked - A stage that is built on an upward slant.
Rigging - The way in which mobile scenery is controlled.
Run - The total number of performances for a production.
Run-Through - To rehearse the show by performing from beginning to end without stopping.
Running Order - The order in which a show's scenes and songs are performed.
Scrim - Loosely-woven material that is used as a drop. When lit from the front scrim is opaque, when lit from behind it is transparent.
Sightlines - Imaginary lines of sight that determine what is visible to the audience on stage and what is not.
Spike - To mark on the stage or rehearsal floor the placement of set pieces.
Spike Mark - A mark on the stage or rehearsal floor, usually a piece of tape, that denotes the specific
placement of a piece of scenery or a prop.
Spill - Extraneous light that can be cut off with a shutter.
Stage Brace - An adjustable piece of stage equipment that fits into a brace cleat to support scenery.
Stage Left - When facing the audience, the area of the stage on the actor's left.
Stage Right - When facing the audience, the area of the stage on the actor's right.
Strike - The removal of all stage equipment, scenery, props, lights, and costumes from the stage area.
Technical Rehearsal - The rehearsal or series of rehearsals in which the technical elements of the show are integrated with the work of actors. Also called Tech.
Thrust Stage - A type of theatre in which the audience is seated on three sides of the stage.
Traveler - A curtain that can open to the sides of the stage.
Trim - The height to which a piece of scenery or stage equipment will be flown.
Wings - The right and left sides of the backstage area.
Worklights - Lights used for general illumination of the stage when not in performance.
