I depends on what you want to learn, that relay course is a good intro to relay testing covering many different type, induction disk and some solid state. If you are looking for a specific relay to learn or just solid state look to the manufacturer or Doble. Overall the AVO classes are very good, I have been to a few years back. They do slip some sales stuff in there for thier products (Megger test equipment) but then again they make some pretty good test equipment.