Minecraft 1.8.9, Minecraft 1.10
If you put 4 regular rails down in a T shape, and you put a redstone torch or redstone block next to the junction, it doesn't switch. On the other hand, placing a lever replacing the torch and powering the lever will activate the junction.
Here is a list of other things that work:
- Pressure plates
- Redstone Chests
- Detector rails
- This is because all these things are placed unpowered, but redstone torches and redstone blocks are placed powered.
See Etho's LP Video: https://www.youtube.com/watch?v=Vfi8czqZo_0