CCTV (closed-circuit television) is a TV system in which signals are not publicly distributed but are monitored, primarily for surveillance and security purposes. CCTV relies on strategic placement of cameras, and observation of the camera's input on monitors somewhere.
In the traditional analog CCTV application, security cameras capture an analog video signal and transfer that signal over coax cable to the Digital Video Recorder (DVR). Each camera may be powered by plugging in the power supply right at the camera or by using RG59 coaxial cable which bundles the video and the power cables. The DVR converts the analog signal to digital, compresses it, and then stores it on a hard drive for later retrieval.
An Internet Protocol camera, or IP camera, is a type of digital video camera commonly employed for surveillance, and which, unlike analog closed-circuit television (CCTV) cameras, can send and receive data via a computer network and the Internet.
Infrared cameras (IR) are sometimes referred to as IR cameras or "Night Vision Security Cameras" because of this. Infrared cameras have IR LEDs positioned around the outer edges of the camera lens which gives the camera its "Night Vision".
A special lens with thermal sensor focuses the infrared light emitted by all of the objects in view. The focused light is scanned by a phased array of infrared-detector elements. The detector elements create a very detailed temperature pattern called a thermogram.