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Glossary
GL-4
February 2001 8784-A2-GB20-30
router
A device that connects LANs by dynamically routing data according to destination and
available routes.
RS-449
An Electronic Industries Association's standard for a general-purpose, 37-position,
DCE/DTE interface.
RTS
Request to Send. A signal from the DTE to the device, indicating that the DTE has data to
send. V.24 circuit 105.
RXD
Received Data. Pin 3 of the EIA-232 interface that is used by the DTE to receive data from
the modem. Conversely, the modem uses Pin 3 to transmit data to the DTE.
SDSL
Symmetric Digital Subscriber Line. A technique for the use of an existing twisted-pair line
that permits high bandwidth, bidirectional transmission.
SES
Severely Errored Seconds. Usually defined as a second during which a specific number of
CRC errors was exceeded, or an OOF or other critical error occurred.
SNMP
Simple Network Management Protocol. Protocol for open networking management.
T1
A term for a digital carrier facility used to transmit a DS1 formatted digital signal at
1.544 Mbps. It is used primarily in North America.
TCP/IP
Transmission Control Protocol/Internet Protocol. The dominant protocol suite in the
worldwide Internet, TCP allows a process on one machine to send data to a process on
another machine using the IP. TCP can be used as a full-duplex or one-way simplex
connection.
TDM
Time Division Multiplexer. A device that enables the simultaneous transmission of multiple
independent data streams into a single high-speed data stream by simultaneously sampling
the independent data streams and combining these samples to form the high-speed
stream.
Telnet
Virtual terminal protocol in the Internet suite of protocols. Allows the user of one host
computer to log into a remote host computer and interact as a normal terminal user for that
host.
TFTP
Trivial File Transfer Protocol. A standard TCP/IP protocol that allows simple file transfer to
and from a remote system without directory or file listing. TFTP is used where FTP is not
available.
transceiver
A circuit capable of acting as both a transmitter and a receiver.
transmitter
A circuit capable of generating, modulating, and sending a signal for communication,
control, and other purposes.
TXD
Transmit Data. Pin 2 of the EIA-232 interface that is used by the DTE to transmit data to the
modem. Conversely, the modem uses Pin 2 to receive data from the DTE.
UNIX
An operating system developed at AT&T Bell Laboratories and since used as the basis of
similar operating systems.
V.3 5
An ITU-T standard for a high-speed, 34-position, DCE/DTE interface.
WA N
Wide Area Network. A network that spans a large geographic area.
X.21
An ITU-T standard for a high-speed, 15-position, DCE/DTE interface.
Yellow Alarm
An outgoing signal transmitted when a DS1 or DS3 terminal has determined that it has lost
the incoming signal.