Quote Originally Posted by Sk_rmouche View Post
Quiet a nice pattern, simple and functional

It reminds me my wiring, series of normally-closed switch embedded into a loop with relay's coil
Thank you

Yes I was thinking of doing a latching relay circuit with the normally-closed safety switches breaking the coil connection, thereby unlatching the relay. But then I also wanted a momentary push On, push OFF action through a single push button switch, and some sort of fault memory/display. So although this could have been done by adding additional relays, I though it best to do some of the logic electronically instead. And of course CMOS chips are extremely cheap compared to relays.

Another method would have been to use a PIC or Atmel microprocessor as the logic, which would have cut down on some of the components, but not enough to have really changed the cost. And I also didn't want to take the chance of creating any EMF/RF emission problems that might have resulted (although I could have run the clock speed very slow to counteract this possibility). And I was also afraid of me being tempted to use the programmability and built-in peripheral support to add all sorts of bells and whistles with all the inherent bugs that might come with it (creeping featurism).

So yes I decided to bite the bullet and keep it simple.