CCTV is everywhere: at shops, banks, offices, apartment buildings, and more and more homes. But what does the name actually mean, and how does a CCTV system work, especially at night? This guide explains it in plain language.
What does CCTV stand for?
CCTV stands for closed-circuit television. "Closed circuit" means the video is sent to a limited set of screens and recorders, rather than being broadcast openly like normal television. Only the people who have access to the system, such as the owner or security staff, can see the footage.
What do Americans call CCTV?
In the United States, people usually say security cameras, surveillance cameras, or video surveillance rather than CCTV. In Sri Lanka, the UK, and much of Asia, "CCTV" is the everyday word. They all describe the same thing: cameras that record an area for security.
How does a CCTV system work?
A CCTV system has three main parts:
- Cameras capture video of the areas you want to watch.
- A recorder receives the video from every camera and saves it to a hard drive. An NVR (network video recorder) is used with IP cameras, and a DVR or XVR is used with analogue cameras.
- A screen or app lets you watch live video and play back recordings, either on a monitor connected to the recorder or on your phone.
In a wired system, each camera connects to the recorder by cable. IP cameras often use PoE (Power over Ethernet), so a single network cable carries both power and video. The recorder records continuously, on motion, or on a schedule, and automatically records over the oldest footage when the hard drive is full.
When the recorder is connected to the internet, you can watch your cameras and receive motion alerts on your phone from anywhere. The recording itself does not need the internet. Read more in does CCTV work without internet or WiFi?
IP cameras vs analogue cameras
- IP cameras send digital video over a network cable. They usually offer higher resolution, smarter features such as line-crossing alerts, and simpler wiring with PoE.
- Analogue HD cameras send video over coaxial cable to a DVR or XVR. They can be a lower-cost option and are common when upgrading older systems that already have coaxial cable in place.
How does CCTV work at night?
Most CCTV cameras see in the dark in one of two ways:
- Infrared (IR) night vision. Small infrared LEDs around the lens light up the scene with light that people cannot see, and the camera switches to black-and-white mode. The IR range is listed in the camera's specifications, often 20 to 30 metres for common home cameras.
- Full-colour night vision. These cameras use very light-sensitive sensors, often with a small warm white light, to keep recording in colour after dark. Colour footage makes it easier to describe clothing and vehicles.
At dusk, cameras switch to night mode automatically using a light sensor. For the best night footage, avoid placing cameras behind glass (infrared reflects off it) and keep bright lights out of the frame. Our guide to planning CCTV coverage and placement covers this in more detail.
Who invented CCTV?
One of the earliest known CCTV systems was built in Germany in 1942 by engineer Walter Bruch at Siemens, to watch rocket launches from a safe distance. Recording to videotape arrived later, and CCTV spread to banks, shops, and public spaces through the second half of the twentieth century. Today's systems record digitally in high definition and can be viewed from a smartphone anywhere in the world.
Is CCTV worth it for a home or business?
For most homes and businesses, yes. Visible cameras help deter theft and trespassing, recordings help you understand what happened after an incident, and remote viewing lets you check on your property from anywhere. The key is choosing the right cameras and placing them well.
To see what a complete system costs, read our CCTV camera price guide. When you are ready, browse our CCTV cameras and kits or ask about our professional CCTV installation, which includes a free site survey.