It just has two slots – one to send in a layer, the other a switch to turn the entire layer on or off. Super basic, nothing complicated. Great for those big flythrough scenes where you need to do something like “Turn off all calculations on Layer X after frame 200”.
Originally I created it as a Python tag that would turn on or off the layer it’s parent object was a part of, but that went screwy fast if you wanted to have that particular layer hidden on your timeline – because the switch would disappear with the layer. Thus my adjustment to Xpresso, where I essentially wrote my own version of Niklas’ great tool.