Apple AirPort Time Capsule 802.11n (4th Generation) - Manual (Page 25)

25 Chapter 2 SettingUpYourTimeCapsule
Your first backup with Time Capsule and Time Machine could take overnight
or longer, depending on how much data you’re backing up. To speed up the initial
backup, connect your Time Capsule to your computer using Ethernet. In each
subsequent backup, Time Machine backs up only files that have changed since the
previous backup, so the backups don’t take as long.
Time Capsule is a great wireless backup solution for portable computers. Since
the first backup can take some time, plug your portable into a power adapter—this
conserves battery power and guarantees that backups won’t be interrupted. Also,
for the best wireless performance, place your portable computer in the same room
as your Time Capsule.
If you shut down your Mac or put it to sleep during a backup, Time Machine stops the
backup and then continues from where it left off after your Mac starts up again.
For more information about Time Machine, choose Help > Mac Help from the Finder
menu on a computer using Mac OS X Leopard or later, and then type Time Machine
in the search field.