Installation guide

Glossary
150
890 USE 101 00 October 2006
frame A message unit, particularly that part between the start delimiter and the end
delimiter.
frame check
sequence
A calculated number sent with a message unit and checked by the receiver to
assure message integrity.
graded-index Fiber design in which the refractive index of the core is lower toward the outside of
the fiber core and increases toward the center of the core. It bends the rays inward
and allows them to travel faster in the lower index-of-refraction region. This type of
fiber provides high bandwidth capabilities.
ground A common signal return point from various circuit elements.
ground block An RIO network component that may be used as the single-point ground for the
system.
HLDC (high level
data link control)
The link layer protocol used on an RIO communications network.
Hot Standby
System
A 984 capability in which two identically configured PLCs are connected to the same
process via RIO cable systems. One primary PLC controls the process while the
other standby constantly monitors the process. If the primary controller fails, the
backup controller takes over system control operations.
I/O map A table in the PLC’s user memory that directs I/O data to the proper drop/channel
and I/O module.
impedance See characteristic impedance.
ingress The noise picked up by a transmission line from outside sources.
G
H
I
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com