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. Because the cameras communicate with monitors and/or video recorders across private coaxial / network cable runs or wireless communication links, they gain the designation "closed-circuit" to indicate that access to their content is limited by design only to those able to see it.

Older CCTV systems used small, low-resolution black and white monitors with no interactive capabilities. Modern CCTV displays can be color, high-resolution displays and can include the ability to zoom in on an image or track something (or someone) among their features. Talk CCTV allows an overseer to speak to people within range of the camera's associated speakers.

CCTV is commonly used for a variety of purposes, including:
•    Maintaining perimeter security in medium- to high-secure areas and installations.
•    Observing behavior of incarcerated inmates and potentially dangerous patients in medical facilities.
•    Traffic monitoring.
•    Overseeing locations that would be hazardous to a human, for example, highly radioactive or toxic industrial environments.
•    Building and grounds security.
•    Obtaining a visual record of activities in situations where it is necessary to maintain proper security or access controls