| Annex A |
| UART | Universal Asynchronous Receiver Transmitter: A device providing a |
| serial interface for transmitting and receiving data. |
| UDP | User Datagram Protocol. A protocol above the IP layer that provides |
| port multiplexing in addition. In essence, you can transmit IP data |
| packets to several receiving processes in the same unit/device. |
| Unicast | |
| one to many (or many to many). In this mode, a transmit unit sends |
| video data direct to a unique destination address. |
| Upconvert | The process by which the frequency of a broadcast transport stream |
| is shifted to a higher frequency range. |
| Uplink | The part of the communications satellite circuit that extends from the |
| Earth to the satellite. |
| UPS | Uninterruptable Power Supply: A method of supplying backup power |
| when the electrical power fails or drops to an unacceptable voltage |
| level. Small UPS systems provide battery power for a few minutes; |
| enough to power down the computer in an orderly manner. This is |
| particularly important where write back cache is used. Write back |
| cache is where modified data intended for the disk is temporarily |
| stored in RAM and can be lost in the event of a power failure. |
| Sophisticated systems are tied to electrical generators that can |
| provide power for days. UPS systems typically provide surge |
| suppression and may provide voltage regulation. |
| UTC | Universal Time Coordinate: An internationally agreed basis for |
| timekeeping introduced in 1972 and based on international atomic |
| time (corresponds to Greenwich Mean Time or GMT). |
| VITC | Vertical Interval Time Code. |
| VITS | Vertical Interval Test Signal: See: ITS. |
| VLAN | Virtual LAN, a network of units that behave as if they are connected |
| to the same wire even though they may actually be physically |
| located on different segments of a LAN. |
| VPS | Video Programming System: A German precursor to PDC |
| WSS | Wide Screen Switching: Data used in |
| services, which enables a receiver to select the appropriate picture |
| display mode. |
| WST | World System Teletext: System B Teletext. Used in 625 line / 50 Hz |
| television systems |
| |
| XILINX | A type of programmable Integrated Circuit. |
| XLR | Audio connector featuring three leads, two for signal and one for |
| GND. |
| XML | eXtensible Markup Language. A very common |
| based data format. Used for many purposes: |
| configuration files, documents, etc. The readability of the format has |
| made it very popular and is now the fundament for many types of |
| WEB services. |
EN/LZT 790 0005 R1A |