Alan B. Pearce wrote: >> An intrinsically safe system does what it does by sticking to >> that part of the laws of physics that make sparks impossible. > > or encloses them in a way that will not allow the spark to reach the outside > environment. Yep, this is typically how the 2-way radio world's "intrinsically safe" products work also... push-to-talk and other open contacts are surrounded by rubber and sealed. Nate -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist