[header] How to install window sensors in your home [title] Choose which windows in your home you want to make part of your home security system. [step] Buy one sensor for each, after confirming that a particular kind of sensor is compatible with your burglar alarm system. [substeps] You don't need to cover all your windows. 
Windows that are plainly visible from the street, and windows up off the ground floor, usually don't need a sensor. Neither do windows that are too small for a burglar to fit through.