These days, the use of computers has become an integral part of human life. In fact, the average person cannot function well in a day without the utilization of a number of computer-run and automated devices, one of which is the UPS system, also known as uninterrupted or uninterruptible power supply.There are different manufacturers of UPS systems today, thanks to the fact that demand for such products has shown a significant increase over recent years. Because of this, there are now several brands to choose from. One must choose carefully, though, in order to get the right UPS system for his computer, lest difficulties be encountered later on. There are also different types of systems to consider, including the three general categories, namely the on-line, line-interactive, and the standby uninterruptible power supplies.An on-line UPS makes use of a double conversion method as regards the acceptance of AC input and the consequent rectifying to DC in order to pass through the battery; it then inverts back to AC (specifically a 120V one) in order to power the protected equipment. On the other hand, a line-interactive UPS works to maintain the inverter in line, redirecting the computers batteries DC current path away from the normal charging mode into temporary supplying current the moment power is lost. Meanwhile, a standby (also known as off-line) UPS carries a load powered actually by the input power; this means that the backup power circuitry is only called upon when the utility power encounters some difficulty or fails entirely. Most computer users want the standby variety or the line-interactive variety, as these uninterruptible power supplies are known to be less burdensome on the pocket. Let us get to know these technologies more.The standby UPS, among the others, offers the most basic features: It provides battery backup and surge protection. This kind of system allows equipment to be connected directly to whatever incoming utility power; the surge is protected via a plug strip, which is normally connected across the main power line. Once the incoming utility power falls below the expected level, the standby UPS then works to turn on its simple internal DC-AC inverter circuitry, and then mechanically switches the equipment to its DC-AC inverter output – all of which happens in 25 milliseconds or less, depending on much time the standby UPS takes to detect lost utility voltage.The line-interactive UPS operates in similar fashion as the standby UPS, but there is an additional feature in the form of a multi-tap variable-voltage auto-transformer, a special kind of electrical transformer that has the ability to subtract or add powered coils of wire, thus decreasing or increasing the overall output voltage. This variety can tolerate over-voltage surges and under-voltage brownouts (even continuous ones) without ending up consuming the battery reserve or causing any more interruption while making the switch from power to battery.Those using large power units have another option on their hands, namely the dynamic UPS, which makes use of a synchronous alternator or motor connected on the mains through what is called a choke. A flywheel holds the energy and an eddy-current regulator maintains power on the load. Other uninterruptible power supplies technologies include the diesel rotary UPS and the fuel cell UPS.