This blue gate offline 2500va ups is a standard offline ups that can keep your light for a long time. Is where the mains supply is rectified to a clean dc voltage and rebuilt into a very clean and regulated ac voltage, at all times your critical load runs from this clean no break supply. Line-interactive and off-line ups’s are single conversion, put in its crudest form your computer runs on semi regulated mains and will always suffer a small break in supply whilst the ups moves from mains mode to battery mode in a mains fail situation.