Editing Built-in self-test (section)

===Medicine===

Medical devices test themselves to assure their continued safety.  Normally there are two tests.  A POST will perform a comprehensive test.  Then, a periodic test will assure that the device has not become unsafe since the POST.  Safety-critical devices normally define a "safety interval", a period of time too short for injury to occur.  The self test of the most critical functions normally is completed at least once per safety interval. The periodic test is normally a subset of the POST.