GE MDS 4790M Installation And Operation Manual page 15

DCE— Data (circuit terminating) Communications Equipment. In data
communications terminology, this is the "modem" side of a
computer-to-modem connection. The transceiver board is a DCE device which
is designed to connect to a DTE device.
Decibel (dB)—A measure of the ratio between two signal levels. Frequently
used to express the gain or loss of a system.
DSP—Digital Signal Processing. Advanced circuit technique to increase radio
performance, primarily in modulation and demodulation.
DTE—Data Terminal Equipment. In data communications terminology, this
is the computer side of a computer-to-modem connection. (Connects to the
DCE device.)
Fade Margin—The maximum tolerable reduction in received signal strength
which still provides an acceptable signal quality. This compensates for reduced
signal strength due to multipath, slight antenna movement or changing
atmospheric losses. Expressed in decibels.
Frame—A segment of data that adheres to a specific data protocol and
contains definite start and end points. It provides a method of synchronizing
transmissions.
Fresnel Zone—A point of maximum width or girth of the transmitted radio
signal. Obstructions in this region (the "first Fresnel zone") can have a
detrimental effect on reception quality. As a general rule, 60 percent of the first
Fresnel zone should be free of obstructions in a well-designed system.
(Additional considerations are also required when planning an RF path. A
detailed discussion of the subject is presented in Section 8.2, RF Propagation
Planning, beginning on page 74.)
Half-Power Beamwidth—The customary way of measuring the width of a
directional antenna's radiation pattern. This beamwidth is measured in degrees
between the half-power points (the point at which the power is reduced 3 dB
with respect to the main beam).
kbps—Kilobits-per-second.
Master Station (Scanner)—Radio which is connected to the host computer.
It is the point at which polling enters the network.
Menu Directory—Front panel display screen that is the entry point to screens
for displaying radio status and programming the radio. It contains the main
menu items Configuration, Diagnostics, and Event Log.
Multipath Fading—Signals arriving at the receiver out of phase, which have
a tendency to cancel each other. It is caused by reflections of the transmitted
wave and results in distortion at the receiver or weak received signal strength.
Network-Wide Diagnostics—An advanced method of controlling and
interrogating GE MDS radios in a radio network.
Non-intrusive diagnostics—See Passive messaging.
Passive messaging—This is a mode of diagnostic gathering that does not
interrupt SCADA system polling communications. Diagnostic data is collected
non-intrusively over a period of time; polling messages are carried with
SCADA system data (contrast with active messaging).
Payload data—This is the application's user communication data which is
sent over the radio network. It is the radio data that is the primary purpose of
the radio communications.
Remote Station (Outstation)—A radio in a network that communicates with
an associated master station.
MDS 05-3628A01, Rev. B MDS 4790M (MPT 1411) I/O Guide 7