Just for info jimick:-. . The difference between a+c and avionics is that a+c engineers can see and practically understand what they are dealing with. . .Avionics engineers on the other hand haven't got a clue what "electricity" really is....as a matter of fact the best Quantum theory scientists in the world haven't got a clue what "electricity" really is. (try reading "the God Particle" or "Stephen Hawkins"). This explains the weird nature of avionics engineers. You could liken it to trying to fix aircraft with magic!! This is why they are all strange,confused and ramble incoherently when asked theoretical questions!!! <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . .. .Good luck anyway.