IBM 5251 Series Maintenance Information Manual page 13

option: One of the items listed on a display screen
menu.
overview: A short description.
P-P: Peak-to-peak.
pc: Printed circuit.
planar: See main planar.-
PM: Preventive maintenance.
poll: A method the controller uses to determine if a
display station is ready to send or receive data.
POR: Power on reset.
port: The place where a cable is connected to a
machine.
protector: A device that aids in preventing injuries to
persons or damage to machines.
R/D: Receiver/driver.
raster: The image on the CRT that is made by the
action of the CRT electron beam as it scans across the
area of the CRT where data is displayed. Normally, the
intensity of the raster is not high enough to be visible.
However, the raster can be displayed if you install a
raster check jumper.
read-only storage (ROS): A storage area in the MPU
from which data can be read but not changed.
read/write storage: A storage area in the MPU that
stores information for later use; the information can be
changed by the MPU.
receivers: Those parts that accept data or voltages.
refresh: To continuously redisplay data on the display
screen to prevent the data from fading out; the display
adapter refreshes the data.
regen buffer: An area in read / write storage where data
is stored before it is displayed.
register: A storage device or circuit that stores those
limited parts of data needed by the system to execute
input/ output, storage, processing, and control
operations.
related: Having a common use.
required: See mandatory.
resolution: The visual quality of display screen data.
retaining ears: The projections located on the bottom
of a key module; these projections hold the module to
the frame. See reference 133.
retrace lines: The lines that appear on the display
screen when the display adapter returns the sweep to
the upper left corner of the display screen. Retrace lines
are normally blanked out. See reference 156.
retry: To repeatedly send frames of information until
the frames are received without an error by the display
station; the controller sends the frames.
ripple: Small waves present on DC voltages.
ripple level: A measurement of the AC voltage carried
on the DC voltage.
rolling: Pertains to movement on a display screen; the
movement can be either horizontal, vertical, or a
combination of both.
ROS: Read-only storage.
rt
adj: Right adjust.
serdes: Serializer / deserializer.
serializer/deserializer (serdes): A register that is used
to send and receive data between the display station
and the controller.
setup: To prepare a device for operation.
sign-on: A logon procedure performed at a display
station; the procedure can include entering the sign-on
command, a password, or other user specified security
information.
slot: A narrow opening or groove.
SOM: Start of message.
stabilizer: A rod on the Spacebar. See reference 134.
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