NTS&B Subway Signals

Quite a while ago, I came up with a simple LED circuit to use as block signals in my underground loops. The first one worked perfectly, then remaining kept blowing LEDs. I finally figured out that I had to add a resistore on the track side for that problem, but then one LED stayed lit. This turned out to be caused by the operating voltage being much higher than the track voltage. Once I set them about the same, everything started working, and I fixed the other 3 to match. Here is pictures of two of them. The boxes are made from extra battery holders from $1 Tree Accessories.