4.8.3 A complete failure in connectivity between parts should not affect their independent functionality.
4.8.4 An alternative means of operation, independent of the integration, should be available for all essential functions.
4.8.5 When systems under control are required to be duplicated and in separate compartments this should also be applied to computer-based systems.
5 User Interface
5.1 General
5.1.1 Computer-based systems should be designed for ease of handling and user-friendliness and should follow ergonomic principles.
5.1.2 The operational status of a computer-based system should be easily recognizable.
5.1.3 A user guide should be provided. This user guide should describe for example：
function keys menu displays computer-guided dialogue steps, etc.
5.1.4 An alarm should be displayed at relevant operator stations for failure or shutdown of a subsystem.
5.2 Input devices
5.2.1 Input devices should have clearly definable functions, be reliable in use and operate safely under all conditions. The acknowledgement of the instruction given should be recognizable.
5.2.2 Dedicated function keys should be provided for frequently recurring commands and for commands which must be available for rapid execution. If multiple functions are assigned to keys, it should be possible to recognize which of the assigned functions is active.
5.2.3 Control panels on the bridge should be provided with separate lighting. The level of lighting and the brightness of visual display units should be controllable.
5.2.4 Where equipment operations or functions may be changed via keyboards appropriate measures should be employed s6 as to limit access of such operations to authorized personnel only.
