I have a couple of these and I've had no problems with operating them. One is on the crossover below, which gives access to the 'Quarry Branch' or put another way, the continuous circuit on the Logs, Gravel & Bricks.
The lamp housing will only fit on one way, and it has a 'key' so you can't fit it 'back to front'.
I haven't as yet powered the lamp, as I didn't want too many wires around.
I have painted the arrow in green and the circle in red on mine.
I find them useful as I can see from the controller in the 'Signal Cabin' (i.e. the shed!) the route set