I do believe the SIO find is a good one. But I also know after working on these,that there is still a software problem. When they first came out, they were analog. I had no issues going into the overhead. I believe that problem started when they went digital. Also after they went digital they were parallel connected, no SIO board. One car would go into the overhead intermittently. Never could get around the fact that the NTS system didn,t work.