Stan;
Thanks very much for all your replies. I can see that you and I are going to be conversing on these and other technical matters over time.
First, let me say that pretty much everything I said about the ITADs I was tinkering with is WRONG. You were correct about the issue of ambient light being a problem. I just got done testing all 3 of my RealTrax ITADs and they all work. I also tested the ScalTrax ITAD and it works as well. The delay is just as you described it -- how long to wait until relay dropout after the train is no longer sensed.
On the matter of the eBay IR tx/rx pairs, I may take a look at them -- thanks for mentioning it.
Ray