5. Fault Tree Symbols AND GATE - Occurs if all of the input events occur simultaneously. OR GATE- Occurs if any of the input events occur either alone or in combination BASIC EVENT/INDEPENDENT EVENT- An event that requires no further development. Probabilities available from empirical data. UNDEVELOPED EVENT- Fault tree which is not developed further because there is insufficient information or it is of insignificant consequence. COMBINATION/OUTPUT EVENT- Event which is developed further
![Event Tree ,[object Object],[object Object]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)