Some alarm installers recommend eliminating window transmitters and installing motion sensors instead. These sensors are similar to the motion detectors that turn on outdoor floodlights. That approach can cut costs, but we don’t recommend it. Motion sensors cause the majority of false alarms. Worse, they detect burglars only after they’ve entered your home. That can create a dangerous situation where you come face to face with a burglar in your hallway. Door and window transmitters are the only way to detect break ins immediately. Don’t let anyone convince you that motion detectors alone are a substitute for them. Glass breakage sensors are available too, but are optional. Most burglars only break glass in order to unlock a door or window. Then, when they open the door or window, a standard transmitter will detect the entry.