I bought six of the latest 153IRs. I got one working OK- it responds best to lighter-colored cars (yellows, whites).
I ordered some black IR reflective tape (174950439008 on that auction site) for $7 plus shipping. It is supposed to be just semi-gloss black in light, and reflective only in darkness. I plan to cut it into narrower strips (it comes in 1-1/2 in. X 20" long) and place those LOW on the locomotives to reflect to the 153IR, activating the semaphores on my layout.
Two other 153IRs won't do anything, even waving a white paper in front of them, with the "sensitivity" set at max, or by trying "sensitivity" at lower settings. I still have to try the other four.
Any ideas??