Glossary
Appendix D
D-18
Parallel Operation
A type of information transfer where all bits, bytes, or words are
handled simultaneously.
Parallel Output
Simultaneous availability of two or more bits, channels, or digits.
Parallel Transmission
The simultaneous transmission of bits which constitute a character.
Parity
The use of a self-checking code employing binary digits in which the total
number of ones is always even or odd.
Parity Bit
An additional bit added to a binary word to make the sum of the number of
ones in a word always even or odd.
Parity Check
A check in which the parity bit is compared with a previously computed
parity bit.
Peripheral Equipment
Units which communicate with the programmable controller, but are not
part of the programmable controller. Example: a programming device
or computer.
PID Control
See Proportional, Integral, Derivative Control.
PR
See Preset Value.
Preset Value (PR)
The number of time intervals or events to be counted.
Pressure Switch
A switch that is activated at a specified pressure.
Process
(1) Continuous and regular production executed in a definite uninterrupted
manner. (2) One or more entities threaded together to perform a
requested service.
Processor
The decision making data and storage sections of programmable controller.
P
