by illusion » 4 Mar 2006 13:42
It has a number of discs, the discs have grooves cut at certain points on the edge. The key turns each disc the correct ammount, and alligns the grooves in a straight line. Once done, a small piece of metal (the sidebar) will drop into the grooves, allowing the plug to rotate freely.
The disc mechanism is also used by Abus, and interestingly, Blackspur to name two.