GE GFK-2489 - Manual (Page 179)

9-2 TranSphere TS Wireless Extended Range IP Networking Transceivers – January 2008 GFK-2489
9
DCE—Data Communications Equipment. In data communications terminology, this is the
“modem” side of a computer-to-modem connection. The transceiver COM1 and COM2 ports
are set as DCE.
Decibel (dB)—A measure of the ratio between two signal levels. Frequently used to express
the gain (or loss) of a system.
DES—Data Encryption Standard. More information on DES is available at
www.itl.nist.gov/fipspubs/fip46-2.htm.
DHCP—Dynamic Host Configuration Protocol. An Internet standard that allows a client (that
is, any computer or network device) to obtain an IP address from a server on the network.
This allows network administrators to avoid the tedious process of manually configuring and
managing IP addresses for a large number of users and devices.
When a network device powers on, if it is configured to use DHCP, it contacts a DHCP server
on the network and requests an IP address. The DHCP server provides an address from a
pool of addresses allocated by the network administrator. The network device may use this
address on a “time lease” basis, or indefinitely, depending on the policy set by the network
administrator.
DNP3—Distributed Network Protocol 3. DNP3 is an industry-standard protocol that was
initially created for communication between electrical substation devices. Today, this non-
proprietary protocol is being widely adopted for a variety of other applications. Although DNP3
is typically employed in a client-server environment, this serial protocol is one of only a few
that allow peer-to-peer communication between devices without the need for a host computer.
It does this in the same way that IP supports peer-to-peer communication in an Ethernet
environment.
Encapsulation—Process 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 (for example, 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—Ethernet or IP data equipment connected to the ports of the transceiver.
Fade Margin—The greatest tolerable reduction in average received signal strength
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.
FHSS—Frequency Hopping Spread Spectrum. A common transmission technique used by
license-free transceivers.