USP Line Card (V.35/X.21/RS-232) Overview
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Alcatel-Lucent
Beta Beta
OmniAccess 5740 Unified Services Gateway CLI Configuration Guide
USP LINE CARD (V.35/X.21/RS-232) OVERVIEW
In synchronous communications, data is sent as frames of sizes that vary from a
few bytes through 1500 bytes for Ethernet or 4096 bytes for most Frame Relay
systems. The clock is embedded in the data stream encoding, or provided on
separate clock lines such that the sender and receiver are always in
synchronization during a frame transmission.
There are two types of devices that communicate over a Serial Interface: DTE
(Data Terminal Equipment) and DCE (Data Circuit-Terminating Equipment).
A DTE connects to a network through a DCE device. In a typical scenario, a DTE
device is connected to a DCE device. The DCE device provides a clock signal that
paces the communication between the device and the router.
V.35/X.21/RS-232 are well known communication protocols over synchronous
serial lines.
• V.35 Interface
The V.35 interface was originally specified by CCITT as an interface for
48kbps line transmissions. It has been adopted for all line speeds above
20kbps.
V.35 is a mixture of balanced and common earth signal interfaces. The control
lines including DTR, DSR. DCD, RTS, and CTS are single wire common earth
interfaces. The data and clock signals are balanced signals.
• X.21 Interface
The physical interface between the DTE and the DCE is defined in ITU-T
recommendation X.21. The DCE provides a full-duplex, bit-serial,
synchronous transmission path between the DTE and the local PSE.
• RS-232 Interface
RS-232 is specified by Electronic Industries Association. It specifies signal
voltage, timing, function, a protocol for information exchange, and mechanical
connectors. Signal function includes signal for ground, data interchange, flow
control, control of the remote modem, modem status and control signals. For
synchronous communication, these signals provide timing information for the
transmitter and receiver, which may operate at different baud rates.
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