An acoustic collision detection system that enables an aircraft to detect an approaching target, recognize the potential for collision and change course to maintain a safe separation distance, with or without operator invention. The data controlling unit is connected to a first image processing unit and a second image processing unit by separate high-speed serial buses. In an embodiment of the invention, a viewer machine displays only a most recently active shared document window even when other windows are also marked as shared. % of a pulp containing a bast fiber and in that the sheet has a thickness of 150 m or less, a basis weight of 50 gm2 or less and a degree of beating of 3070 SR. Each license server is programmed for managing a distribution of allocations to use the protected software.