HP 8591C User Manual page 335

Glossary
active function
The active function is the instrument's feature currently selected for use.
It may be a key selection or remote-programming command.
active function readout
The area of a display screen where the active function and its state are
displayed. The active function is the one that was completed by the last
key selection or remote-programming command.
active marker
The marker on a trace that can be repositioned by front-panel controls or
programming commands.
active trace
The trace (commonly A, B, or C) that is being swept (updated) with
incoming signal information.
air
See off-the-air tune configuration.
amplitude accuracy
The general uncertainty of an analyzer amplitude measurement, whether
relative or absolute.
ASCII
The acronym for American Standard Code for Information Interchange. It
is an eight-part code (7 bits plus parity check) used for data (information)
interchange. An ASCII value is a specific combination of bits ranging from
0 to 255 that represent characters in machine language that computers
and controllers can understand.
attenuation
A general term used to denote a decrease of signal magnitude in
transmission from one point to another. Attenuation may be expressed as
a scalar ratio of the input to the output magnitude in decibels.
Glossary-2