please tell me what are the different kinds/types of lightning rods?
If you buy them via online, they are generally unlocked. It should say something like Motorola V3 Razr UNLOCKED or something along those lines. If it doesn't, contact the seller to get more information.
Door alarms are set on the inside. Size is not important, but must be easy to activate/deactivate You forgot the most important: a reliable motion sensor. You don't want too many false alarms (say a simple knock on the door or a windy day). If you use batteries, you need a low-battery detector.
