Microwave Data Systems MDS 9810 Installation And Operation Manual page 73

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.
Frequency Hopping—The spread spectrum technique used by the
MDS 9810 transceiver, where two or more associated radios change
their operating frequencies several times per second using a set pattern.
Since the pattern appears to jump around, it is said to "hop" from one
frequency to another.
Frequency Zone—The transceivers use up to 1,019 discrete channels
in the 902 to 928 MHz spectrum. A group of 128 channels is referred to
as a zone. The transceivers use eight frequency zones. (Five channels are
reserved for network control purposes.)
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.
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. Figure 3 on page 3 shows an example
of an MAS system.
Master (Station)—The one radio transceiver in a spread spectrum net-
work that automatically provides synchronization information to one or
more associated remote transceivers. A radio may be programmed for
either master or remote mode using software commands. See Section
6.0, PROGRAMMING (beginning on Page 28).
MCU—Microcontroller Unit. This is the processor responsible for con-
trolling system start-up, synthesizer loading, hop timing, and key-up
control.
Microcontroller Unit—See MCU.
MDS 05-3301A01, Rev. C MDS 9810 Installation and Operation Guide 65