This. I worked in the PTC space in the early 2k's. The person that the FRA send to be their regulatory representative to our program did not trust transistors

This. I worked in the PTC space in the early 2k's. The person that the FRA send to be their regulatory representative to our program did not trust transistors over electromechanical switches, because you couldn't see how the transistors were failing. As you can imagine, our progress was slow.