Uninterruptible Power Supply (UPS) is a special type of power supply commonly found in the security industry. This power supply is used to back up the system for ten minutes or more in the event of a main power failure. The time duration of this available emergency power depends on the size of the UPS and the current power consumption of the equipment in use.
UHF signal Ultra High Frequency signal. In television it is defined to belong in the radio spectrum between 470 MHz and 850 MHz.
Unbalanced signal In CCTV, this refers to a type of video signal transmission through a coaxial cable. It is called unbalanced because the signal travels through the centre core and returns via an earthed condutor. One conductor is a fixed voltage ie earth and only the other moves. In a balanced line system neither conductor is referenced to earth.
Underscan Decreases raster size in both H and V so that all four edges of the picture are visible on the monitor.
UPS Uninterruptible Power Supply. These are power supplies used in the majority of high security systems, whose purpose is to back-up the system when the mains power fails. The duration of this depends on the size of the UPS, usually expressed in output VA (or kVA), and the hold up time expected from fully charged batteries. There are two common types, "off line" and "on line". Off line uses a switch to change from mains to battery operation, thus there can be a short break in the output. On Line UPSs are a type where the convertor is always working, hence there is no switch over break at the ouput.
UTP Unshielded Twisted Pair. A cable medium with one or more pairs of twisted insulated copper conductors bound in a single sheath, with no overall or individual screen. Now the most common method of bringing telephone signals and data to the desktop.