Closed Circuit Television (CCTV) An image communication system that refers to a television system that transmits video in a specific area and plays only in fixed circuit equipment. Such as video recorders, monitors in buildings, etc. This type of broadcast mode is called CCTV. Its signal is transmitted from the source point only to a specific TV set that is prearranged to communicate with the source point. Widely used for a large number of different types of surveillance work, education, videoconferencing, etc. The cable used in CCTV is coaxial cable. Coaxial cable can be divided into baseband coaxial cable and broadband coaxial cable (ie network coaxial cable and video coaxial cable) in terms of use. Coaxial cables are divided into 50Ω baseband cables and 75Ω broadband cables. Baseband cables are further divided into thin coaxial cables and thick coaxial cables. Baseband cables are only used for digital transmission, with data rates up to 3484Mbps. Coaxial cable refers to a cable with two concentric conductors, and the conductor and the shielding layer share the same axis. The most common coaxial cable consists of a copper wire conductor separated by an insulating material. On the outside of the inner layer of insulating material is another layer of ring conductor and its insulator, and then the entire cable is surrounded by a sheath of polyvinyl chloride or Teflon material.