Like a regular shield it has to be plugged on top of the Arduino and it can be stacked on top of other shields. It is used both as OUTPUT and INPUT. For each line it has two kinds of port that can be used: the DMX connector and theregular cable. On the front it has two DMX connectors, one for the INPUT and one for the OUTPUT. The DMX Master Shield supports up to 512 DMX modules connected in parallel. If you’re using the TinkerKit! official receivers, they have four channels each that makes a total of 128 cascade connected modules, directly controllable from your computer.