An uninterruptible power supply (UPS) is an electrical system that is specially designed to keep work from stopping. When the utility power fails or falls to unsuitable levels, a UPS switches to battery energy as a backup source, helping prevent power interruptions in even a single second's time. A UPS electrical system is provided so as to maintain the voltage within acceptable limits, regulate power conditions, and implement emergency power. Modern computerized features including automatic voltage regulation, surge suppression, and battery back up will ensure all connected equipment operate smoothly. UPS electrical systems now are widely used in many fields - for example health care, data centers and international finance which cannot accept even a moment's downtime due to power.