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Ultra High Frequency, UHF

It is designated by International Telecommunications Union (ITU) for the 300 to 3000 MHz band of frequencies.

Unbalanced Line

It means a transmission line in which voltages on the two conductors are unequal with respect to ground.  A coaxial cable is a common type of unbalanced line.

Underwriters Laboratories, UL

UL is a non-profit organization which tests and verifies construction and performance of electronic parts and equipment, including wire and cable.

Universal Serial Bus, USB

An external bus that supports Plug and Play installation. Using USB, you can connect and disconnect devices without shutting down or restarting your computer. You can use a single USB port to connect up to 127 peripheral devices, including speakers, telephones, CD-ROM drives, joysticks, tape drives, keyboards, scanners, and cameras. A USB port is usually located on the back of your computer near the serial port or parallel port.

Unshielded twisted pair(s), UTP

Twisted pair cables are available unshielded (UTP) or shielded (STP), with UTP being the most common. STP is used in noisy environments where the shield around each of the wire pairs, plus an overall shield, protects against excessive electromagnetic interference. A variation of STP, known as ScTP for "screened twisted pair" or FTP for "foil twisted pair," uses only the overall shield and provides more protection than UTP, but not as much as STP.

USB port

An interface on the computer that enables you to connect a Universal Serial Bus (USB) device. USB is an external bus standard that enables data transfer rates of 12 Mbps (12 million bits per second). USB ports support a plug that is approximately 7 mm x 1 mm.

User

A person who uses a computer or device.  If the computer is connected to a network, a user can access the programs and files on the computer, as well as programs and files located on the network (depending on account restrictions determined by the network administrator).

User Account

A record that consists of all the information that defines a user to Windows. This includes the user name and password required for the user to log on, the groups in which the user account has membership, and the rights and permissions the user has for using the computer and network, and accessing their resources. For Windows XP Professional and member servers, user accounts are managed with Local Users and Groups. For Windows Server domain controllers, user accounts are managed with Microsoft Active Directory Users and Computers.

User Name

It means a unique name identifying a user account to Windows. An account's user name must be unique among the other group names and user names within its own domain or workgroup.

User Password

The password stored in each user's account. Each user generally has a unique user password and must type that password when logging on or accessing a server.