UART

Universal Asynchronous Receiver-Transmitter. A semiconductor device that sends and receives digital data.

UF

Thermoplastic underground feeder and branch circuit cable.

UG

Symbol for coaxial connectors that are made to government specification.

See also RG/U.

UHF

Ultra High Frequency. The band that extends from 300 to 3,000 mc, as designated by the Federal Communications Commission.

UHF Connector

An input/output electronic interconnect device designed to work at frequencies up to 300 gigahertz at voltages to 500 V.

UJT

See Unijunction Transistor.

UL

Underwriters Laboratories. A US organization that sets certain standards for connector testing.

UL 94V-0

The highest flammability rating developed by UL. Indicates a housing material's ability to extinguish a flame in the event of a fire.

UL 94V-2

A lower flammability rating developed by UL and applied to connector housings. Flames on a housing made of this material would take longer to extinguish than those on material rated UL 94V-0.

Ultrasonic Bond

Process of joining materials by the scrubbing action and energy transfer of a tool that vibrates at an ultrasonic frequency (around 20 kHz for plastic; range of 60-120 kHz for metal). The energy transfer efficiently results in the heating of a material for bonding when the material innately possesses sufficient internal lossiness or friction to convert mechanical energy into irreversible heat energy during each cycle of tool forced vibration.

Ultrasonic Cleaning

Cleaning operation that uses ultrasonic vibration and agitation. It is used at various stages in the connector overmolding process.

Unbalanced Line

A single-ended transmission line in which the absolute difference of the voltages on the two conductors (of signal and ground return current shield, respectively) are unequal with respect to ground potential. 

A coaxial transmission line is an example of an unbalanced single-ended line. In contrast, a "twinax" design is an augmented or enhanced coax-like line constituting a differential line design with a pair of signal wires that create the double-ended line. In the latter design the absolute difference in voltage between one of the pairs and ground is equal (balanced) to that of the other pair and ground.

See also Balanced Line.

Underwriters Laboratories

See UL.

Uniaxial Assembly

The one directional mounting of a connector. Press-fit connectors, for example, use uniaxial assembly. This is a one direction motion of pushing the pins through the board. It is all that is required to mount the connector.

Uniformity

The variation of power level between the optical outputs of a splitter.

Unijunction Transistor (UJT)

A negative resistance semiconductor switch used for timing circuits, oscillators, and triggering circuits.

Unilay

Multiple layers of helically laid wires with the direction and length of lay being the same for all layers.

Universal Serial Bus (USB)

See USB.

Unshrouded Header

See Header.

uP

Microprocessor.

URC

Weatherproof wire.

USB

Universal Serial Bus. A serial bus standard developed by PC and Telecom industry leaders Compaq, DEC, IBM, Intel, Microsoft, and Northern Telecom. 

USB brings "plug and play" to computer peripherals. Specialized cards are not needed and integrated software eases installation of new devices. Many devices may be serially connected on a single port.

USE

Underground service entrance cable, rubber insulated neoprene jacket.

User Friendly Socket and Carrier

A cost effective method for interchanging IC devices, useful wherever field replacement, updating, or reprogramming is required of microprocessors, ROMs, PROMs and EPROMs.