UPS

Keep your computer, NAS, server, Point of Sale equipment or home security system powered and safe from electrical surges by using an uninterruptible power supply.

UPS devices plug straight into your wall (using the normal 10A socket). If they detect that power is lost (i.e. a surge or spike) they will switch onto battery mode and are designed to temporarily power important devices. They usually have surge protection too.

People often use a UPS for their home networking, security system, computers or audio-visual equipment. Pretty much for anything that is a pain when it "goes down". UPS batteries usually last anywhere from 15 minutes to 8 hours, depending on the load placed on them.

Most uninterruptible power supplies will have the ability to connect to your computer, either by USB or a direct network cable, and can be controlled by management software.

They give off an audible alarm when they switch to battery mode, so they're a crucial failsafe for those looking to protect their electronics.