Open as Applied to Electrical Equipment - Means
that moving parts, windings, or live parts are exposed to accidental
Ohm - The unit of measure for resistance.
Ohm's Law - Voltage equals resistance multiplied
Oil - When relating to a liquid-filled transformer,
refers to mineral oil.
Optical Fiber Cable - a cable consisting of
one or more optical fibers that transmits modulated light for the
purpose of control, signalling, or communications.
Oscillogram - A record made of an oscillograph.
Oscillograph - A device used for recording and
measuring the instantaneous values of a rapidly varying electrical
quantity as shown by its corresponding waveform.
Outlet - A point in the wiring installation at
which current is taken to supply utilization equipment.
Outline Lighting - An arrangement of incandescent
lamps or electric discharge tubing to outline or call attention
to certain features such as the shape of a building or the decoration
of a window.
Overcurrent Device - Any device capable of automatically
opening an electric circuit, under both predetermined overload
and short-circuit conditions, either by fusing of metal or by electro-mechanical
Overload device - A device affording protection
from excess current, but not necessarily short-circuit protection,
and capable of automatically opening an electric circuit either
by fusing of metal or by electro-mechanical means.
Overvoltage - A voltage above the normal rated
voltage or the maximum operating voltage of a device or circuit.
A direct test overvoltage is a voltage above the peak of the line