MultiModemISDN User Guide
Universal Serial Bus: A collection of Universal Serial Bus devices and the software and hardware that allow them to connect the capabilities provided by functions to the host.
Universal Serial Bus Device: Includes hubs and functions. See device.
Universal Serial Bus Driver: The host resident software entity responsible for providing common services to clients that are manipulating one or more functions on one or more Host Controllers.
Universal Serial Bus Interface: The hardware interface between the Universal Serial Bus cable and a Universal Serial Bus device. This includes the protocol engine required for all Universal Serial Bus devices to be able to receive and send packets.
Unshielded Twisted Pair (UTP): Telephone-type wiring. Tansmission media for 10Base-T.
Upstream: The direction of data flow towards the host. An upstream port is the port on a device electrically closest to the host that generates upstream data traffic from the hub. Upstream ports receive downstream data traffic.
USB: See Universal Serial Bus.
USBD: See Universal Serial Bus Driver.
USB Performance categories: Low Speed (Interactive Devices at 10-100 Kb/s); Medium Speed (Phone, Audio, Compressed Video at 500Kb/s - 10Mbp/s); High Speed (Video, Disk at 25-500 Mb/s)
UTP (unshielded twisted pair) —Telephone-type wiring.
V
V.110—One of the terminal rate adaptation protocols for the ISDN B-channel. V.110 is more hardware-intensive than the V.120 B-channe l standard.
V.120—One of the terminal rate adaptation protocols for the ISDN B-channel. V.120 is more software-intensive than the V.110 B-channe l standard.
Videotex—A two-way information-retrieval service that can be accessed by terminals and by a TV set (with installed decoder). Allows interactive retrieval of information pages from a central resource. See also ISDN.
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).
X
X.25—ITU-T’s definition of a three-level packet-switching protocol to be used between packet-mode DTEs and network DCEs. X.25 corresponds with layer 3 of the 7-layer OSI model.
X.75—An ITU-T standard for linking X.25 packet-switched networks. X.75 defines the connection between public networks, i.e., for a gateway between X.25 networks.
