extreme secure and high availability systems with strong access control

How is it done?

The US intercontinental titan missile system, had to be extremly secure.
But the soldiers on duty also had to be unlock and fire the rocket within minutes if requested!

This was done by:
- two person control
- unlock key in a padlock with 2 locks
- simultaneous actions
- 6 character code lock for fuel lines, from padlock
- code received by radio + code from padlock
- strong perimeter security 

Source: http://www.crypto.com/blog/titans