Servos virtually always have encoders built in, for a closed-loop system. They can, therefore, "self home" using a regular limit swtich.
The process is that the carriage travels over to the home switch, and trips it. Now that it "knows" where it is in relation to the limit, it starts "looking" for wht's known as an index line or index count in the encoder. So it sneaks past the limit switch until it spots that index line and then stops. It now knows, to whatever the resolution of the encoder is, where it is.
As I understand it, theoretically I could add encoders to my steppers, and the Acorn board, with some help, could read them and do that "self homing" routine.
However, at the moment I am NOT anywhere near experienced enough with the necessary software in general or the Centroid stuff in particular, to be able to pull that one off. So I'm gonna try and stick with mechanical limit switches. At least those I can understand.