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.
Tiltmeter: works like a carpenter's level, and measures vertical movement along a fault. Creep meter: Measures movement along a slip-strike fault, so it measures horizontal movement along a fault. Laser ranging device: detects changes in distance to a reflector. Basically, it's a device that bounces beams off a reflector to detect fault movements. GPS satellite system: Uses a network of Earth-orbiting satellites and measures tiny vertical/horizontal movements of markers set u on the opposite sides of a fault.