How Do CCTV Cameras Work?

Updated February 21, 2017

A closed circuit TV camera (CCTV) transmits video, and sometimes audio, signals to a monitor, set of monitors, multiplexer or computer. Each camera uses either a wired, wireless or digital network to transmit the audio and visual signals to a private reviver.

Analogue CCTV

Analogue CCTV systems use one of two main conduits to transmit audio-visual information. The first, and most common, is a wired configuration. The second uses a wireless transmitter to connect to a receiver.

Wired CCTV installations run a cable or wire between the camera and the monitor. The image data is usually transmitted over a coaxial cable. The audio is usually transmitted over a simple copper wire or wires. The signal transmitted over these wires and cables is then fed in to a monitor or a set of monitors if the image needs to be visible in different locations. A multiplexer can be used to display feeds from multiple cameras on a single monitor. Each camera's picture would take up a pre-set amount of space on the monitor. Analogue CCTV cameras can also be routed to an image capture board on a computer to allow the audio-visual information to be viewed on a computer monitor.

Wireless CCTV installations are similar to wired. The difference is that a radio transmitter is attached to the camera. A radio receiver is then attached to the input on the monitor system or computer. Wireless systems are useful in a couple of situations. The first is when the distance between the camera and the monitor is too far to be practical for a cable run. Wireless CCTV is also good when cables aren't practical because of aesthetic reasons.

Digital CCTV

CCTV installations can also be digital. Digital CCTV often uses internet Protocol (IP) cameras. An IP camera is a camera that contains the camera and hardware to convert the audio and video signals to a stream of packets that can then be transmitted over a local area network (LAN) wide area network, (WAN) or even over the internet.

Digital CCTV has many advantages over analogue. First, it can use existing wired or wireless internet, including Wi-Fi. Because of this, it isn't limited by distance. A CCTV camera can be set up in one city and have its signal transmitted easily to another city. Another advantage of digital CCTV is that a series of cameras can be routed to a wireless hub, thus minimising the amount of cabling required for a complex installation.

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About the Author

Although he grew up in Latin America, Mr. Ma is a writer based in Denver. He has been writing since 1987 and has written for NPR, AP, Boeing, Ford New Holland, Microsoft, RAHCO International, Umax Data Systems and other manufacturers in Taiwan. He studied creative writing at Mankato State University in Minnesota. He speaks fluent Mandarin Chinese, English and reads Spanish.