UPS questions

[harley3344]

I tryed searching th forums for a ups topic but failed so if im reposting im srry, I need basic info on what the functions of ups's do like will they use power off the wall jack untill power gos out than kick in and provide battory power or does it require to hook up seperatly or what?
next what brands would be the best to get and last the longest- cheap ect. Thanks ( I belive I chose the wrong area)

 

[brady]

This has a lot of information that may be useful to you : http://en.wikipedia.org/wiki/Uninterruptible_power_supply

 

[harley3344]

Thanks answered alot of my questions but didnt suggest any brands can somoe give me some suggestions. Thanks