Mobile DJ Dictionary – Original Version Excerpted From 1997 Edition

August 25, 2009 by Mobile Beat

Mobile DJ Dictionary

  • AC (Alternating Current) – Electrical power which oscillates up and down a number of times per second. U.S. power runs at 60 times a second, or 60Hz.
  • AMP – The measurement used to describe the amount of electrical current flowing in a wire or circuit.
  • ANALOG – see Control Logic.
  • BALLAST – Used with Fluorescent and Discharge lamps. Similar to a transformer by delivering proper operating voltage, but a Ballast also limits current flow or else the lamp would draw increasing current and self-destruct. Also, Ballasts are used to provide a temporary high voltage to start the lamp or arc.
  • BEAM SPREAD – Measurement in degrees of the width or diameter of a light beam. Examples: A very narrow spot beam (VNSP) is approximately 5°, a narrow spot (SNP) 12°-20°, medium and wide floods range from 18°-55°. Note: Beamspreads expressed with two numbers indicate an oval shape. Examples: 15° x 32°, 20° x 40°.
  • CHANNEL – An individual control/power circuit, connected to and causing its lighting to turn on/off, and, in some cases, dim higher and lower.
  • CANDELA (aka Candlepower) – The intensity of light from a source or fixture in one direction.
  • CHASE – Lamps turning on and off in sequence, controlled by a variable speed control.
  • COLOR TEMPERATURE – The blueness or redness of a light source, expressed as a temperature in degrees of Kelvin. Examples: A 2,700° lamp appears very warm or red like a table lamp or pinspot. At 3,100°, the halogen lamp has more blue content and appears whiter. Sunlight at noon is approximately 5,000°.
  • CONTROL LOGIC – A low voltage DC. signal (0-15 volts) known as analog. Also, a digital signal (example: DMX512). Control Logic signals activate power packs which, in turn, activate lights.
  • CONTROLLER – A device that utilizes control logic to control lighting. In audio, the mixer/preamp is analogous to a controller.
  • CROSSFLOW – A controller function that dims one lighting channel to a lower level, while simultaneously fading another to a higher level.
  • DC (Direct Current) – does not oscillate like AC, but flows steadily. DC can literally destroy transformers and must be avoided when these are present.
  • DICHROIC – A thin rare earth coating is applied to a lamp reflector to conduct heat rays backwards and light forward.
  • DICHROIC FILTER – Durable, heat resistant material, usually borosilicate glass. Special coatings are applied to the glass which pass select wavelengths (colors) and reject all others. An audio analogy is a narrow bandpass filter. These last much longer than other color media and the hues and shades of color are pure and brilliant.
  • DISCHARGE LAMP (aka High Intensity Discharge Lamp (H.I.D.) – A family of lamps that produce light by means of an arc through a gas. Categories of H.I.D. lamps include Mercury Vapor, Metal Halide, High and Low Pressure Sodium. These offer long life and higher output of light than most other types of lamps and require the use of ballasts to operate.
  • DISPLAY – A group or area of active lighting such as pinspots, par cans, strobes, etc.
  • ELECTROMOTIVE FORCE (EMF) – When AC voltage is applied to a transformer (see inductive load), a contrary or opposing voltage builds up, and is released when the applied voltage is turned off. This EMF feeds back through the circuit where the original voltage comes from, known as BACK EMF. Back EMF is bad for powerpacks and other power output devices and can virtually blow them up. Rapid chase of transformer devices like pinspots increases this kickback or backfire. To compensate, some manufacturers install EMF protection in powerpacks and specify a reduction in total load ratings by 30-40 percent.
  • HALOGEN LAMP – An incandescent lamp containing special gases. Halogen lamps exhibit higher color temperature (whiter light) and increased operating life, usually 3-5 times longer. However, these take longer than regular incandescent lamps to go completely off or dark when turned off or chased.
  • INCANDESCENT LAMP – A lamp that emits visible light as a result of a filament being heated.
  • INDUCTIVE LOAD – Usually a load containing a winding or coil, i.e. transformer, electric motor, etc.
  • INTELLIGENT LIGHTING – A misnomer associated with moving lights or moving mirror scanners. These fixtures usually do not operate on their own and require instructions from controllers.
  • FOOTCANDLE (fc) – A measurement of light level reaching a surface. One fc = one lumen (see lumen) per square foot.
  • JOULE – An energy measurement, usually used for strobes, where 1 watt at 1 second = 1 Joule.
  • LASER – Acronym: Light Amplification by Stimulated Emission of Radiation. Also a device that creates a very tight light beam of a certain color. Lasers used for entertainment purposes utilize mirrors and motors to move the beam in varying patterns. Laser operation is tightly regulated by government agencies, primarily to protect vision.
  • LASER CHASE/DARK CHASE – In Light Chase mode, lights will appear to move or switch on in an animated sequence. Dark Chase is where a dark space will appear to move as lamps are switched off.
  • LOAD RATING – The maximum amount of watts or amps that a circuit or powerpack can handle. Exceeding the maximum load rating for any one channel, or all channels of a powerpack, could result in a complete shutdown or damage, or tripping a circuit breaker which disengages the circuit.
  • LUMEN – A measurement of light output, emanating from a light source or lamp in all directions.
  • MATRIX (aka X-Y Chase) – By using special controllers and powerpacks to chase large quantities of fixtures such as pinspots or par cans, many more flow patterns can be created. The controllers/packs actually fire the
    fixtures’ hot wires and neutral wires separately.
  • METAL OXIDE VARISTOR (MOV) – An electrical device commonly used in power conditioners for absorbing the energy of spikes.
    MOV’s are able to absorb spikes of an energy content at or near their maximum rating without degradation. When hit by a sufficiently large spike, the MOV may be destroyed. However,
    MOV’s are inexpensive to replace and by giving up their life, valuable and expensive equipment is protected.
  • NOISE (Referred to as Electro Magnetic Interference [EMI] and Radio Frequency Interference [RFI]) – Electrical noise is caused by many factors and phenomena, including lightning, load switching, generators, radio transmitters, lighting dimmers, etc. It can be intermittent or chronic and have an adverse effect on computer data. Noise can also become quite audible through audio and sound systems. Power conditioners often provide filters to eliminate or reduce EMI/RFI noise.
  • PAR, PAR36, PAR46, etc. – P = parabolic (the shape). A = Aluminized (the reflective coating). R = Reflector. The number indicates the diameter or size expressed in the number of 1/8 inch pitches across the front of the lamp. Example: 36 = 36 x 1/8, or 4 1/2.
  • PHASE CONTROL – A commonly used method to dim lighting. Basically, the AC waveform is switched on and off rapidly, undetectable to human vision, as a method to lower lamp output. Unlike earlier dimming methods, phase control does not generate DC which is harmful to inductive loads.
  • PINSPOT – Usually a 6 volt or 12 volt PAR36/PAR46 spotlight with built-in transformer. Quality pinspots are fuse protected and some are U.L. listed.
  • POWERPACK – Handles high power and provides the muscle for the controller brain. Analogous in Audio to a power amp. Two types are Relay/Switching packs which simply turns lights on and off and Dimming Packs, a.k.a. Dimmers which not only turn lights on/off, but also raise/lower light level.
  • POWER CONDITIONER – An electrical device used to protect sensitive electronic equipment from voltage spikes/surges, and EMI/RFI noise. Power conditioners can also include voltage regulation to protect against voltage sags or surges which exceed safe operating ranges.
  • PROTOCOL – See Control Logic.
  • QUARTZ LAMP – Usually, but not always, a Halogen lamp. Due to higher operating temperatures, quartz (instead of glass) must be used as the envelope or shell around the filaments. These must not be touched by human skin because body oil can cause them to blacken.
  • RAINLIGHT – See Pinspot.
  • SAGS (Also known as brownout) – Short term decreases in voltage. This is the most common power problem in the U.S., reaching a regular occurrence rate of 87%. Electronic devices can be damaged or may not function when voltage drops below a safe operating range.
  • SCENE – A number or combination of displays or lights switched on together to provide a specific effect or look.
  • SEQUENTIAL POWER UP/POWER DOWN – A function of certain power conditioners where the components or devices plugged into the conditioner are electrically switched on, one-at-a-time in a timed sequence. Eliminates large currents, pops, thumps and other audible noise when switching on audio components.
  • SOUND CHASE (aka Audio Chase) – Similar to Auto Chase, except the sequence of light movement is controlled by rhythm (usually bass beat) so that the lighting sequence responds to beat of the music.
  • SURGE – A short term increase in voltage, usually 10% to 35% above normal. Surges last longer than spikes (15ms to minutes) and are a result of high-powered motors, appliances, and other high current devices being switched on. Sensitive electronic devices can be damaged when safe operating ranges of voltage are exceeded.
  • SPIKE – An instantaneous, dramatic increase in voltage, as high as 6,000 volts. Usually of short duration (milliseconds) and caused by nearby lightning strikes, spikes can enter through AC, serial, or phone lines, and damage solid state components, or cause data loss. Effects can be cumulative, causing gradual deterioration and catastrophic failure.
  • TRANSFORMER – An inductive load device used to change AC input voltage to higher or lower voltage output.
  • TRIAC – A solid state, AC switch, used for heavy power handling and dimming of lighting.
  • VOLT – Describes the amount of force at which an electrical current flows.
  • VOLTAMP – A unit of electrical power and a measurement of electrical power of a device, usually a transformer. Similar to a watt, but a voltamp device must have a higher rating than the unit taking and consuming power from it.
  • WATT – A unit of electrical power and a measurement of electrical power when voltage goes from its origin to its destination. Denotes power consumed.
  • ZERO VOLTAGE SWITCHING – A sensing network which allows a triac to switch only when its supply voltage is at zero. Used for interference suppression or noiseless switching. Will not dim.
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