This is one individual littleBits bit:The roller switch is a handy switch that gets activated when the roller is pushed in. Put it on a door to make it do something when the door hits the wall. You can also flip the mode switch and make it do the opposite: do something when the roller is released, just like a fridge light! What’s littleBits? littleBits is a system of electronic modules that snap together with tiny magnets for prototyping and play.

Check out the detailed electrical diagrams on GitHub.