Many people now work from home and some home IT installations are as complex as those found in an office environment. When selecting a UPS system, the same principles should be applied as for an office based IT network. The ideal UPS type is an on-line system as this offers the most in terms of power protection and a break-free supply from a battery set when the mains power fails. Line interactive offer the next level in power protection. Whilst not as good as an on-line UPS the output from a line interactive is often good enough thanks to the Switch Mode Power Supply (SMPS) used within a file server. High-end residences may even more complex networks including access control and CCTV security. They may require a three phase as opposed to a single phase UPS system and possible a standby power generator to allow them to run through extended power outages.