UART (universal asynchronous receiver-transmitter) The device that performs the bidirectional parallel-to-serial data conversions necessary for the serial transmission of data into and out of a computer.

UDDI (Universal description, discovery and Integration) The protocol that lets programs discover Web services in a public web directory.

UDP (user datagram protocol) A TCP/IP protocol describing how messages reach application programs within a destination computer. This protocol is normally bundled with IP-layer software. UDP is a transport layer, connectionless mode protocol, providing a (potentially unreliable, unsequenced, and/or duplicated) datagram mode of communication for delivery of packets to a remote or local user.

UDP/IP (user datagram protocol/internet protocol) See: UDP above.

ULSI (ultra-large-scale integration) A logic device containing a million or more gates.

ultrasonic Of or relating to acoustic frequencies above the range audible to the human ear, or above approximately 20,000 hertz. Compare with supersonic.

unbalanced line See: balanced line

UPS (uninterruptible power supply) A back-up power supply (commonly used with computers) that automatically continues to supply AC power when the main AC source fails.

URL (uniform resource locator) A Web address. A consistent method for specifying Internet resources in a way that all Web browsers understand. For example, "http://www.showorks.com," is the URL for SHOWORKS's home page on the web. The "http" part tells the Web browser what protocol to use, and the remainder, "www.showorks.com," is the URL.

USB (universal serial bus) A serial bus that acts like a special purpose local area network. Proposed by a consortium of Compaq, Digital, IBM, Intel, Microsoft, NEC and Northern Telecom in March of 1995, the intended purpose is to replace the typical cable ghetto found on most PCs. A USB equipped machine was envisioned that would have only three ports: USB, monitor, and LAN. The USB port would support 63 devices, and eliminate the need for all specialized parallel, serial, graphics, modem, sound/game or mouse ports. USB is completely "plug and play," i.e., it detects and configures all devices automatically, and allows "hot swapping" of devices.

UV (ultraviolet) Electromagnetic radiation at frequencies higher than visible light yet lower than those of x-rays. Commonly used to erase EPROMs and in wireless and fiber optic data transmission.

UWB ( Ultra Wide Band ) Instead of traditional sine waves, UWB broadcast digital pulses that are timed precisely on a signal across a very wide bandwidth. According to the UWB Working Group (www.uwb.org), UWB can transmit large amounts of data over a variety of frequencies , at very low power, over short distances.  with more power , UWB can transmit over longer distances and through obstacles.  This was demonstrated in one of the technologies first applications, Ground Penetrating Radar.  Currently max transmission speeds are limited to 60Mbps, but some industry analyst are predicting 1Gbps in the near future.