244 Glossary
Trident Planning and Installation Guide
intermittent fault Fault or error that is only occasionally present due to unstable hardware or varying
software states.
LED Light-emitting diode. One of the color-coded signal lights on each controller circuit
board that indicates the board’s status. Each system component includes at least the
Pass, Fail, and Active LEDs.
logical slot Logical slot comprises a primary module, a hot-spare module, and associated field
termination components. A baseplate is a physical representation of a logical slot.
Markov model Generalized modeling technique which can be used to represent a system with an
arbitrary number of modules, failure events, and repair events. A Markov model
can be mathematically solved to produce a resultant probability.
MP Main Processor Module.
module Active field-replaceable unit consisting of an electronic circuit assembly housed in
a metal cover.
MTBF Mean-time-between-failure. The expected average time between failures of a
system, including the time taken to repair the system. Usually expressed in hours.
MTTF Mean-time-to-failure. The expected average time to a system failure in a
population of identical systems. Usually expressed in hours.
MTTR Mean-time-to-repair. The expected time to repair a failed system or subsystem.
Usually expressed in hours.
node Any of the machines on a network.
node number Physical address of a node.
non-triplicated
module
I⁄O module with a single set of field-interface circuitry for communication with all
three main processor modules. Non-triplicated modules provide a cost-effective
alternative to the use of TMR modules for non-critical environments.
open network Network to which an external host can be connected.
output poll time Time required by the controller to implement the outputs generated by the
application in response to inputs from the controlled process.
PE Protective earth.
PES Programmable electronic system.
To Next Page
Loading...