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ROC827 Instruction Manual
Issued Mar-06 Glossary A-2
C (continued)
Comm Module
Module that plugs into a ROC to provide a channel for communications via a specified
communications protocol, such as EIA-422 (RS-422) or HART.
CF
Compare Flag; stores the Signal Value Discrete (SVD).
Configuration
Refers either to the process of setting up the software for a given system or the result of
performing this process. The configuration activity includes editing the database, building
schematic displays and reports, and defining user calculations. Typically, the software
setup of a device that can often be defined and changed. Can also mean the hardware
assembly scheme.
Configuration
Tree
In ROCLINK 800, the graphical display that appears when a configuration file opens. It is
a hierarchical branching (“tree-style”) method for navigating within the configuration
screens.
CPU
Central Processing Unit.
CRC
Cyclical Redundancy Check error checking.
Crosstalk
The amount of signal that crosses over between the receive and transmit pairs, and
signal attenuation, which is the amount of signal loss encountered on the Ethernet
segment.
CSA
Canadian Standards Association. See http://www.csa.ca.
CSMA/CD
Carrier Sense Multiple Access with Collision Detection.
CTS
Clear to Send modem communications signal.
D
D/A
Digital to Analog signal conversion.
DB
Database.
dB
Decibel. A unit for expressing the ratio of the magnitudes of two electric signals on a
logarithmic scale.
DCD
Data Carrier Detect modem communications signal. In addition, Discrete Control
Device – A discrete control device energizes a set of discrete outputs for a given setpoint
and matches the desired result against a set of discrete inputs (DI).
DCE
Data Communication Equipment.
Deadband
A value that is an inactive zone above the low limits and below the high limits. The
purpose of the deadband is to prevent a value (such as an alarm) from being set and
cleared continuously when the input value is oscillating around the specified limit. This
also prevents the logs or data storage location from being over-filled with data.
Device Directory
In ROCLINK 800, the graphical display that allows navigation through the PC Comm
Ports and ROC Comm Ports setup screen.
DI
Discrete Input.
Discrete
Input or output that is non-continuous, typically representing two levels (such as on/off).
DMM
Digital multimeter.
DO
Discrete Output.
Download
The process of sending data, a file, or a program from a PC to a ROC.
DP
Differential Pressure.
DSR
Data Set Ready modem communications signal.
DTE
Data Terminal Equipment.
DTR
Data Terminal Ready modem communications signal.
Duty Cycle
Proportion of time during a cycle that a device is activated. A short duty cycle conserves
power for I/O channels, radios, and so on.