NonStop System Glossary

position-independent code (PIC)
Executable program or library code that is designed to be loaded and executed at any virtual
memory address, without any modification. Addresses that can be modified by the loader do not
appear in PIC code, only in data that can be modified by the loader. See also dynamic-link library
(DLL).
POSIX
The Portable Operating System Interface, as defined by the Institute of Electrical and Electronics
Engineers (IEEE) and the American National Standards Institute (ANSI). Each POSIX interface is
separately defined in a numbered ANSI/IEEE standard or draft standard. The application program
interface (API), known as POSIX.1, has become ISO/IEC IS 9945-1:1990.
power distribution panel (PDP)
A group of panel assemblies that composes a single panel that includes buses and overcurrent
protection devices (with or without switches). A PDP is used for the control of power circuits.
power distribution unit (PDU)
An assembly of outlets and fuses that is installed on both sides of a modular cabinet. This assembly
provides power and over-current protection for the components installed in the modular cabinet.
power domain
A set of customer-replaceable units (CRUs) and field-replaceable units (FRUs) that share a set of
power rails. For telco Central Office (CO) systems, the power domain is the entire system.
power factor
The ratio of real power to apparent power (that is, kilowatts/kilovoltamperes). The power factor
for a sinusoidal load is determined by the position of the applied voltage waveform with respect
to the current drawn by the load. When voltage and current are in phase with each other, the
power factor is unity, and the power for the load is equal to the product of the applied voltage
and load current (P=EI). When the current waveform lags the voltage waveform, the load is inductive.
Conversely, when the current waveform leads the voltage waveform, the load is capacitive. In
either case, the power for the load is equal to the product of the applied voltage, load current,
and the angular displacement between the voltage and current waveforms (P=EIcosf). Nonlinear
(nonsinusoidal) loads also have a power factor. However, the power factor for a nonsinusoidal
load reflects harmonic content and not angular displacement.
power factor correction
The addition of a reactive component to offset the angular displacement of a sinusoidal load.
Traditionally, the normal power factor for a facility is inductive, so the normal correction involves
the addition of capacitors to offset the lagging power factor. The capacitors offset part or all of
the inductive reactance, making the total circuit more nearly in phase with the applied voltage.
The power factor for nonlinear (nonsinusoidal) loads cannot be corrected through the addition of
simple reactive components. Harmonic filters are required to correct the power factor of nonlinear
loads.
power fail (PFAIL)
Loss of alternating current (as determined by OSM) to both processor switches. It is triggered by
an AC_LOSS event.
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