Close-circuit television (CCTV) is the use of video cameras to transmit signal to a specific, limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point to point wireless links. CCTV is often used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations and convenience stores. Increasing use of CCTV in public places has caused debate over public surveillance versus privacy. People can also buy consumer CCTV Systems for personal, private or commercial use. More advanced form of CCTV, utilising Digital Video Recorders (DVR), provide recording for possibly many years, with a variety of quality and performance options and extra features (such as motion-detection and email alerts). In industrial plants, CCTV equipment may be used to observe parts of a process from a central control room; when, for example, the environment is not comfortable for humans. CCTV systems may operate continuously or only as required to monitor a particular event.