Omron 8025G Maintenance Manual page 254

GLOSSARY
Field maintenance: Maintenance performed to correct malfunctions by replacing read-
ily Changed parts. modules, or circuit cards.
Full-duplex: Two-way simultaneous communications.
Half-duplex: Alternate, one-way-at-a-time. independent transmission.
Header: IC socket plug to which jumper wires can be added to change circuitry on
a circuit card.
High: Logic 1.
KB data channel: Channel on which data leaves the keyboard.
LED data channel: Channel for supplying on/off instructions to the keyboard LED
indicators.
Line: Horizontal line of characters on the display screen.
~: Logic O.
MA data bus: Bus lines over which addressing is done in the terminal.
Memory: Device that temporarily or permanently stores information.
Memory seam: Highest available address in memory.
Modem: Device that modulates and demodulates signals transmitted over communications
facilities.
Monitor: Same as CRT display.
NAND gate: Gate that has a low output when all inputs are high.
NOR gate: Gate that has a low output when at least one input is high.
OR gate: Gate that has a high output when at least one input is high.
pa,e base: Defines the memory location of the character displayed in the uppermost
Ie t character position on the CRT display.
Preventive maintenance: Maintenance performed to correct abnormal conditions before
they develop Into malfunctions.
Printer: External device that supplies hard copy of data.
Program memo;r: Memory that stores the instructions needed by a CPU to perform its
functions.
Programmed read only memory (PROM): Read only memory that can be programmed by the
equipment manufacturer rather than by the memory manufacturer.