xviii
SIG-00-07-11 SEPTEMBER 2012 (REVISED OCTOBER 2019)
Version No.: B.2
TERM
DESCRIPTION
LED
Light Emitting Diode.
LoMA
Limits of Movement Authority.
The control center's safety interlocking logic uses the
data from all trains to issue
limits of movement authority (LoMA)
and speed limits
to each train, being careful to keep safe separation between trains. The train's
onboard computer monitors the LoMA and speed limit data against actual train
location and speed to determine potential and actual unsafe conditions. If the train is
approaching the end of its LoMA or it is nearing its speed limit, the onboard computer
warns the engineer, who is expected to take appropriate action. If the train passes the
end of its LoMA, the onboard computer automatically signals for a safety brake
application to bring the train to a stop.
MCF
Module Configuration File. Application specific configuration file. Defines how the VIU-
20e will operate in a specific application such as the Office Monitoring or Wayside
Interface applications. Contains default settings for configurable parameters.
MCP
Mobile Communications Package
MEF
Module Executable File. The VIU-20e executive software. Defines the general
operation of the VIU.
NMEA
National Marine Electronics Association.
NMEA 0183
(or
NMEA
for short) is a
combined electrical and data specification for communication between marine
electronic devices such as echo sounder, sonar, Anemometer (winds speed and
direction), gyrocompass, autopilot, GPS receivers and many other types of
instruments. It has been defined by, and is controlled by, the US-based National
Marine Electronics Association.
The NMEA 0183 standard uses a simple ASCII, serial communications protocol that
defines how data is transmitted in a "sentence" from one "talker" to one "listener" at a
time. Through the use of intermediate expanders, a talker can have a unidirectional
conversation with multiple listeners, and using multiplexers, multiple sensors can talk
to a single computer port. Third-party switches are available that can establish a
primary and secondary talker, with automatic failover if the primary fails.
OBC
On-Board Computer.
OCG
Office Communication Gateway. Communications traffic router, such as a packet
switch, that provides the interface between the office monitoring system and the
communications infrastructure.
OSI
Open Systems Interconnection. A layered, abstract description for communications
and computer network protocol design. It is sometimes known as the
OSI seven
layer model
. From top to bottom, the OSI Model consists of the Application,
Presentation, Session, Transport, Network, Data Link, and Physical layers. A layer is
a collection of related functions that provides services to the layer above it and
receives service from the layer below it.
PTC
Positive Train Control.