CCTV systems use video cameras to transmit signals to monitors for security purposes. There are two main types of CCTV systems: wired systems connect cameras to recording devices and monitors using cables, while wireless systems attach radio transmitters to cameras and receivers to monitors. CCTV cameras come in different types depending on whether they are used indoors or outdoors, and provide day/night surveillance capabilities. Key elements of a CCTV system include cameras, lenses, monitors, recording devices like DVRs, storage, cables, and power supplies. CCTV cameras are commonly installed in schools, shops, hospitals, bars and other public areas for security and crime prevention.