HP 8591C User Manual page 342

The abbreviation for Hewlett-Packard Interface Bus. It is a
Hewlett-Packard proprietary parallel interface that allows you to connect
more than one device to a port on a computer or instrument. The HP-IB
bus is also called the IEEE-488 bus.
in-channel frequency response
Frequency response test that measures the flatness of an individual cable
TV channel.
incrementally related carriers
Incrementally related carriers (IRC), is a tune conEguration where all
channels except channels 5 and 6 are standard channels (see standard
tune configuration for a deEnition of standard channels).
input attenuator
An attenuator (also called an RF attenuator) between the input connector
and the Erst mixer of an analyzer. The input attenuator is used to
adjust the signal level incident to the Erst mixer, and to prevent gain
compression due to high-level or broadband signals. It is also used to
set the dynamic range by controlling the degree of internally-generated
distortion. For some analyzers, changing the input attenuator settings
changes the vertical position of the signal on the display, which
then changes the reference level accordingly. In Hewlett-Packard
microprocessor-controlled analyzers, the IF gain is changed to compensate
for changes in input attenuator settings. Because of this, the signals
remain stationary on the display, and the reference level is not changed.
input impedance
The terminating impedance that the analyzer presents to the signal
source. The nominal impedance for RF and microwave analyzers is
usually 50 0. For some systems, such as cable TV, 75 D is standard. The
degree of mismatch between the nominal and actual input impedance is
called the VSWR (voltage standing wave ratio).
integer number
A whole number with no decimal or fractional part.
IRC
See incrementally related carriers.
Glossary-9