Communication devices for linking computer networks; communication software; apparatus for controlling the storage of data; apparatus for data collection; apparatus for data entry; apparatus for data input; apparatus for data memories; apparatus for data output; apparatus for data storage; apparatus for data transmitting; apparatus for guarding data communication systems against unauthorised access; apparatus for interconnecting data processing equipment; apparatus for reading data on optical apparatus; apparatus for receiving data; apparatus for retrieving data; apparatus for sending data; apparatus for the acquisition of data; apparatus for the communication of data; apparatus for the conversion of data; apparatus for the graphic display of data; apparatus for the storage of data; apparatus for the storage of pictorial data; apparatus for the storage of textual data; apparatus for transmitting data; apparatus for transmitting data by the telephone network; apparatus for use in data logging; computer apparatus for the storage of data; computer apparatus for transmitting data; computer controlled workstations for data entry; computer data input apparatus; computer databases; computer installations for the storage of data; computer interface units for translating data; computer networks for the storage of data; computer software; downloadable computer software; computer software for providing a graphical presentation of data; computer software for scientific data analysis; computer software for use in database management; computer related data communication apparatus; computer software for mapping; computer software for monitoring, tracking and managing personnel, vehicles and assets; connecting devices for data collection; connecting devices for data transfer; data files; data processing installations incorporating expandable architecture; data processing software; data processing software for graphic representations; data programmes; data recorded in computer accessible form; database programs; databases; programs for data processing apparatus (recorded); programs for data processing apparatus recorded on disks; programs for data-processing; programs for processing data on computers; luminous beacons; navigational instruments; satellite navigational devices; software for satellite navigation systems; GPS navigations systems