116 MDS iNET 900 User’s Guide MDS 05-2806A01, Rev. A
dBi—Decibels referenced to an “ideal” isotropic radiator in free space.
Frequently used to express antenna gain.
dBm—Decibels referenced to one milliwatt. An absolute unit used to
measure signal power, as in transmitter power output, or received signal
strength.
DCE—Data Circuit-terminating Equipment (or Data Communications
Equipment). In data communications terminology, this is the “modem”
side of a computer-to-modem connection.
COM1 Port of the iNET 900
is set as DCE.
Decibel (dB)—A measure of the ratio between two signal levels. Fre-
quently used to express the gain (or loss) of a system.
Device Mode—The operating mode/role of an MDS iNET 900 pro-
grammed to serve as the master station in an iNET network.
Digital Signal Processing—See DSP.
DSP—Digital Signal Processing. In the MDS 9810 transceivers, the
DSP circuitry is responsible for the most critical real-time tasks; prima-
rily modulation, demodulation, and servicing of the data port.
DTE—Data Terminal Equipment. A device that provides data in the
form of digital signals at its output. Connects to the DCE device.
Encapsulation—Process in by which, a complete data packet, such as
Modbus frame or any other polled asynchronous protocol frame, is
placed in the data portion of another protocol frame (in this case IP) to
be transported over a network. Typically this action is done at the
receiving end, before being sent as an IP packet to a network. A similar
reversed process is applied at the other end of the network extracting
the data from the IP envelope, resulting in the original packet in the
original protocol.
Endpoint—IP address of data equipment connected to the ports of the
iNET 900 unit.
Equalization—The process of reducing the effects of amplitude, fre-
quency or phase distortion with compensating networks.
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 15 to 20
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.
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