INTERLOCK Used to enforce a sequence of actions or events 1. Event a does not occur inadvertently 2. Event a does not occur while condition c exists 3. Event a occurs before event d · EXamples Batons Critical sections Synchronization mechanisms Remember, the more complex the design, the more likely errors will be introduced by the protection facilities themselves Design Example: Nuclear detonation Safety depends on NOT working Three basic techniques(called"positive measures") 1. solation Separate critical elements(barriers) 2. Inoperability Keep in inoperable state, e.g., remove ignition device or arming pin 3. Incompatibility Detonation requires an unambiguous indication of human intent be communicated to weapon Protecting entire communication system against all credible abnormal environments(including sabotage)not practical Instead, use unique signal of sufficient information complexity that unlikely to be generated by an abnormal environmentc ��������������������� ���������� INTERLOCK Used to enforce a sequence of actions or events. 1. Event A does not occur inadvertently 2. Event A does not occur while condition C exists 3. Event A occurs before event D. Examples: Batons Critical sections Synchronization mechanisms Remember, the more complex the design, the more likely errors will be introduced by the protection facilities themselves. c ��������������������� ���������� Example: Nuclear Detonation Safety depends on NOT working Three basic techniques (called ‘‘positive measures’’) 1. Isolation Separate critical elements (barriers) 2. Inoperability Keep in inoperable state, e.g., remove ignition device or arming pin 3. Incompatibility Detonation requires an unambiguous indication of human intent be communicated to weapon. Protecting entire communication system against all credible abnormal environments (including sabotage) not practical. Instead, use unique signal of sufficient information complexity that unlikely to be generated by an abnormal environment