Actually the twist lock is on the 120v side. GFCI-->underground line to pool timer pole ---->120v AC in the form of a twistlock plug ----> Light switch with transformer built in to convert 120v to 12v. The transformer is part of the switch which is plugged into the 120v outlet. I just wanted to know if the SR227 will survive the elements so to speak since it was labled as "indoor use only". Thanks for the reply