The article also contains a link to a detailed discussion of PALs - "Permissive Action Links" - that control arming and detonation, and guard against tampering.

The article also contains a link to a detailed discussion of PALs - "Permissive Action Links" - that control arming and detonation, and guard against tampering. See: http://www.cs.columbia.edu/~smb/nsam-160/pal.html http://www.cs.columbia.edu/~smb/nsam-160/pal.html