You don’t’ really know what you know until you have to explain it (or teach it) to someone else. 

When I’m asked about some of the technical aspects of functional safety, I have to stop and ask myself “What Do I Know About This?”  I’m not the kind of guy who tells you how to build a clock when you ask for the time, but I often find that quick questions are not satisfied by quick answers.  I am known to give puzzled looks to people who ask me questions.  I wish I had a dollar for every answer I started with the words “it depends,” and I would not go broke if I had to give a dollar to everyone who got a simple one-word answer.

Just because someone can’t give a yes/no answer doesn’t mean they don’t know the subject matter.  In fact, someone who is knowledgeable on a subject is very likely to begin an answer with several questions to determine the background and other factors that the original question left out.

So the next time someone asks you a question like “If a single transmitter meets SIL2, can I use redundant transmitters to reach SIL3?”, start by asking more questions:

• What is the systematic capability?
• What is the proof test interval and effectiveness?
• What is the site safety index?
• What is the mission time?  And repair time?
• What other components are part of the safety function?  And what are the failure rates?
• \What common cause factor is applicable?

If you really know your subject, you’ll have no problem coming up with questions to determine all the factors that become part of the answer.

Simple question: do you pronounce the capital of Kentucky as “Loo-ISS-vill” or “Loo-EEE-vill”?

Neither…. You pronounce it as “Frank-fort”!  I know my state capitals