Specifications

“Lighting Systems Made Easy” Page 24
D.C.
Direct Current. Doesn’t change polarity. Much more dangerous than A.C. at the same voltage,
as it will tend to grab onto and hold the recipient. A neglected, highly hazardous feature of
most laser power supplies. (The laser beam is usually far less dangerous to life than the
power supply.)
DICHROIC
A thin, rare earth coating often applied to a reflector to conduct heat backward and reflect light
forward. Also used as a forward pass color filter of surpassing efficiency, capable of giving
beautiful, almost monochromatic, colored light.
DIM
To lower the intensity of lighting.
DIMMER PACK
A device made to handle and adjust high power in response to control signals from a lighting
console or controller. (See POWER PACK.) Used to keep lights quiet when run 100% below.
DIODE
A device that lets electricity flow through it one way only. Diodes are used in great numbers in
all electronics.
EMF (ELECTROMOTIVE FORCE)
Back EMF usually occurs when an inductive component, such as a transformer, is switched on
or off quickly. Because a coil (inductor) does not want to change electrical state quickly (re-
luctance), it “fights back,” creating a back EMF condition. This can cause problems with switch
contacts (arcing) and circuit breakers. Neon transformers are a prime source of back EMF,
and only specially made high-inductive load type dimmer packs should be used with them.
FADER
A device, usually a slide potentiometer, used to select various lighting levels.
FLOOD
Refers to either a wide light beam, the technique of flooding an area with light, or as an abbre-
viation for a floodlight.
FLOODLIGHT
A broad-beamed light source used to flood an area with light.
FLY
To suspend lighting, or other articles, up in the air by means of linkages secured to the ceiling.
Strips of lights are commonly ‘flown’ above the front of the stage area.
FOCUS
Commonly used to denote the process of moving a lens back or forth, to produce a hard- or
soft-edged light beam or a clearly defined image. Also used to refer to the center of activity or
emphasis on a stage.