 One of the key features of Time Capsule is the ability to back up a system and files wirelessly and automatically, eliminating the need to attach an external backup drive.This feature requires OS X 10.5.2 Leopard or greater on the client computers.The backup software is Apple's Time Machine, which, by default, makes hourly images of the files that are being changed, and condenses backup images as they become older, to save space.