Permissive action link

A Permissive Action Link is a security device for nuclear weapons. The DOD definition is:

A device included in or attached to a nuclear weapon system to preclude arming and/or launching until the insertion of a prescribed discrete code or combination. It may include equipment and cabling external to the weapon or weapon system to activate components within the weapon or weapon system.

External links:

• http://www.research.att.com/~smb/nsam-160/pal.html
• http://www.sandia.gov/50years/answers04-05-99/answer1b.htm
• The JCAE and the Development of the Pemissive Action Link