CCTV, also known as Closed-circuit television, is the use of security video cameras to transmit a signal to a specific set of monitors that are connected to the cameras. The security camera signal is not openly transmitted, though it may employ point to point wireless links. CCTV security is used for surveillance for different types of businesses that need monitoring such as banks, casinos, airports, military installations, convenience stores, and any small business. CCTV security systems can also be purchased for personal, private or commercial use. A more advanced form of CCTV, using Digital Video Recorders, or DVR's, provide recording for possibly many years, with a variety of quality and performance options and features, such as email alerts or motion-detect. CCTV systems can operate continuously or only as required to monitor a particular event. The first CCTV security cameras used in public spaces were not good cameras. The were conspicuous, crude, low definition black and white systems without the ability to zoom or pan. Modern CCTV security cameras use small high definition color cameras that can focus to resolve minute detail. Also, by linking the control of the security cameras to a computer, objects can now be tracked semi-automatically. For example, they can track movement across a scene where there should be no movement, or they can lock onto a single object in a busy environment and follow it.