25
TERMINAL SERVERS
3.3.4 C
ONNECTING
S
ERIAL
D
EVICES TO THE
T
ERMINAL
S
ERVER
You may connect any RS-232/RS-423 device to any of the serial ports of the
Terminal Server. This section describes the following procedures: connecting
DCE and DTE devices, pin layouts of the RJ-45 connector, and RJ-45 to DB25
or DB9 conversions.
Connecting DCE and DTE Devices
Two types of RS-232 devices can be connected to the Terminal Server serial
ports:
• DTE (Data Terminal Equipment) Devices—These are directly-attached
devices, such as terminals and computers, that provide data in the form
of digital signals at its output.
• DCE (Data Circuit Terminating Equipment) Devices—These are devices
that provide the functions required to establish, maintain, and terminate
connections and also provide the signal conversions required for
communication between a data terminal equipment and the telephone
line or data circuit. Modems connected to the serial port of the Terminal
Server in order to overcome the RS-232 50-ft distance limit are considered
to be DCE devices.
The Terminal Server serial ports act as individual DTEs. A simple and direct
pin-to-pin cable is required if such a serial port is to be connected to a
modem (similarly for any other DTE-to-DCE connection).
However, if terminals are connected directly to one another (in a DTE-to-
DTE configuration, since both the terminal device and the Terminal Server
port are DTEs), a special cable must be used. This cable, known as a “cross
cable” or “null modem cable,” includes crossed-connections between specific
RS-232 pins so that each DTE will recognize the other as a DCE.
Summary of Contents for LE2101A-BT-R2
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