A broken CD or DVD or other type of optical disc is a serious problem and one that will likely lead to loss of information stored on this media. A broken optical disc refers to a disc that has split into two or more pieces or perhaps a disc simply missing one piece.
A motion detector is a device that detects moving objects, particularly people. A motion detector is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area.
Police RADAR. RADAR speed detectors bounce microwave radiation off of moving vehicles and detect the reflected waves. These waves are shifted in frequency by the Doppler effect, and the beat frequency between the directed and reflected waves provides a measure of the vehicle speed.