The HM-DW001 is easily installed in your home or office, each sensor will let the system know if a door or window has been opened or closed. Programming the system to alert you of a change is simple. When used in conjunction with other modules, like a lighting or appliance module, the system can be programmed to turn on lights or fans when you open a door. Plus, door/window sensors can help you save energy and money - check to see if windows are open before you set the system to turn on the AC or heat while you're away.