
Glossary
Transmission Control Protocol / Internet Program (TCP/IP): A
Terminal: The screen and keyboard device used in a mainframe environment for interactive data entry. Terminals have no “box”, which is to say they have no file storage or processing capabilities.
Terminal Adapter (TA): An ISDN DTE device for connecting a
Tie line: A dedicated circuit linking two points without having to dial a phone number (i.e., the line may be accessed by lifting the telephone handset or by pushing a button).
Time Slot: One of 24 channels within a T1 line. Each channel has a 64K bps maximum bandwidth. “Time slot” implies the time division multiplexing organization of the T1 signal.
Toll Call: A call to a location outside of your local service area (i.e., a long distance call).
Tone dialing: One of two methods of dialing a telephone, usually associated with
Topology: Physical layout of network components (cables, stations, gateways, and hubs). Three basic interconnection topologies are star, ring, and bus networks.
Transmission Control Protocol (TCP): A communications protocol used in Internet and in any network that follows the US Department of Defense standards for internetwork protocol. TCP provides a reliable
Transport Layer: Layer 4 of the Open Systems Interconnection (OSI) model; provides reliable,
Transport Protocol Data Unit (TPDU): A transport header, which is added to every message, contains destination and source addressing information that allows the
Trunk: Transmission links that interconnect switching offices.
TSR (terminate and stay resident): A software program that remains active and in memory after its user interface is closed. Similar to a daemon in UNIX environments.
Tunneling: Encapsulation data in an IP packet for transport across the Internet.
Twisted pair wiring: A type of cabling with one or more pairs of insulated wires wrapped around each other. An inexpensive wiring method used for LAN and telephone applications, also called UTP wiring.
U
UART (Universal Asynchronous Receiver/Transmitter) (pronounced “you art”): A chip that transmits and receives data on the serial port. It converts bytes into serial bits for transmission, and vice versa, and generates and strips the start and stop bits appended to each character.
UNIX: An operating system developed by Bell Laboratories that features multiprogramming in a
Unshielded Twisted Pair (UTP):
V
V.25bis: An
V.54: The
•local digital loopback (tests DTE send and receive circuits),
•local analog loopback (tests local modem operation),
•remote analog loopback (tests comm link to the remote modem), and
•remote digital loopback (tests remote modem operation).
Virtual Circuit: A logical connection. Used in packet switching wherin a logical connection is established between two devices at the start of transmission. All information packets follow the same route and arrive in sequence (but do not necessarily carry a complete address).
77 |