I want to delay my ELT purchase as long as possible, so that more 406 options will be available and more affordable. However, I want to do as much pre-wiring as possible before I rivet the forward top skin. Although I don't know which model I will get, I imagine there is some commonality in the wiring. What wires will the ELT need? Does it need power and ground, or does it operate exclusively from an internal battery?