I am trying to make Xbee based Tweek A Watt and brought all the components needed. I have the same issue that Kill A Watt device that I brought recently (2012) has different board than the original instruction, it seems event different than the one in this thread, but it seems that originator of this thread suggest using optisolator that will make the solution independent of varieties of board. I am new to electronic components/circuits. My questions are:
1) what is optisolator? what are the key functions of it?
2) where I can get one to build the solution as suggested here? are there different types of optisolator?