Microwave Data Systems iNet 900 Quick Start Manual page 45

DRAFT 6—8/29/01
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 iNet 900 transceivers, 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 Access Point 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
Access Point station communicates with several Station Adaptors for
the purpose of gathering telemetry data.
Access Point (Station)—The one radio transceiver in a spread spectrum
network that automatically provides synchronization information to one
or more associated remote transceivers. A radio may be programmed for
either Access Point or remote mode using software commands. See Sec-
tion 6.0, PROGRAMMING (beginning on page 21).
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 05-2873A01, Rev. A MDS iNet 900 Installation and Operation Guide 37