MDS 05-3447A01, Rev. F
MDS 1710A/C and MDS 2710A/C/D
7
Fade Margin—The greatest tolerable reduction in average received
signal strength that will be anticipated under most conditions. Provides
an allowance for reduced signal strength due to multipath, slight antenna
movement or changing atmospheric losses. A fade margin of 20 to 30
dB is usually sufficient in most systems.
Frame—A segment of data that adheres to a specific data protocol and
contains definite start and end points. It provides a method of synchro-
nizing transmissions.
Hardware Flow Control—A transceiver feature used to prevent data
buffer overruns when handling high-speed data from the RTU or PLC.
When the buffer approaches overflow, the radio drops the clear-to-send
(CTS) line, which instructs the RTU or PLC to delay further transmis-
sion until CTS again returns to the high state.
Host Computer—The computer installed at the master station site,
which controls the collection of data from one or more remote sites.
Intrusive Diagnostics—A mode of remote diagnostics that queries and
commands radios in a network with an impact on the delivery of the
system “payload” data. See Active messaging.
Latency—The delay (usually expressed in milliseconds) between when
data is applied to TXD (Pin 2) at one radio, until it appears at RXD
(Pin 3) at the other radio.
MAS—Multiple Address System. A radio system where a central
master station communicates with several remote stations for the pur-
pose of gathering telemetry data.
Master (Station)—Radio which is connected to the host computer. It is
the point at which polling enters the network.
MCU—Microcontroller Unit. This is the processor responsible for con-
trolling system start-up, synthesizer loading, and key-up control.
Microcontroller Unit—See MCU.
Multiple Address System—See MAS.
Network-Wide Diagnostics—An advanced method of controlling and
interrogating 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).
