What is CCTV?

CCTV is an abbreviation of closed-circuit television. Unlike conventional television broadcasting, the video signal is transmitted only to a limited number of recipients, such as monitors and recording devices connected directly to the system. It is therefore a closed circuit in which access to the footage is restricted to authorised persons.

In everyday language, CCTV is used as a general term for video surveillance and surveillance systems, whether they are based on analogue technology or digital, network-based systems. The term video surveillance is also commonly used as a synonym.

How does a CCTV system work?

A CCTV system has three main components: cameras, a recording device, and one or more monitors for viewing the footage. The cameras capture images and transmit the video to a central unit that stores and manages the recordings.

Traditional analogue CCTV cameras transmit their video signal via coaxial cable to a DVR (digital video recorder), which converts the analogue signal into digital format and stores it. Modern IP-based systems work differently. The camera processes and digitises the image itself before transmitting the data via network cable or wirelessly to an NVR (network video recorder) or cloud storage. These systems can also be accessed remotely via a computer or mobile phone.

Types of cameras used in CCTV systems

• Box camera is the classic design, featuring a visible rectangular housing and interchangeable lens. It is well suited to locations where the camera should be clearly visible and act as a deterrent.
• Dome camera is housed in a semi-spherical enclosure, making it difficult to determine which direction the lens is pointing. It is commonly used indoors in shops, offices and public spaces.
• Bullet camera has a cylindrical design and is commonly used outdoors. It is resistant to weather conditions and well suited to monitoring longer distances.
• PTZ camera (pan, tilt, zoom) can be controlled remotely and moved from side to side and up and down, while also allowing the operator to zoom in on a specific area. It is used in environments that require flexible coverage of larger areas.
• Thermal camera detects heat radiation rather than visible light and can operate in complete darkness. It is well suited to perimeter protection and environments where conventional cameras may not provide sufficient coverage.

Analogue CCTV or IP camera?

Many older systems are based on analogue CCTV technology using coaxial cable and a DVR. The advantage is that the equipment is often less expensive and straightforward to install if the necessary infrastructure is already in place. The disadvantages include lower image quality, limited remote access and the fact that analogue signals cannot be encrypted.

An IP-based CCTV security camera offers higher resolution, encryption and the ability to monitor the system remotely over a network. IP cameras require more bandwidth, but they are scalable and easy to expand. A PoE switch (Power over Ethernet) allows both power and data to be transmitted over the same cable, simplifying installation.

For anyone building a new system from scratch, IP-based solutions are now the most common choice, while analogue systems can still be an option where coaxial cabling is already installed in the building.

Storage and recording time

How long a CCTV system stores recorded footage depends on the available storage capacity, the number of cameras and the resolution used. An analogue DVR system with limited hard drive capacity and lower resolution may store footage for several weeks, while an IP-based system with high-resolution cameras will use up storage space more quickly unless video compression is used. Modern systems often use H.265 compression, which reduces file sizes without significantly affecting image quality.

IP-based systems can also store footage in the cloud, providing redundancy if the local recording device is damaged or stolen. For organisations with high documentation requirements, it is common to establish retention policies specifying how long footage should be stored before it is overwritten.

What is CCTV surveillance used for?

CCTV surveillance is used in a wide range of settings, from shops, offices and car parks to industrial premises, residential buildings and public spaces. The most common purposes are to prevent and deter crime, provide evidence in cases of burglary or vandalism, and improve safety and security for employees and visitors.

Modern CCTV cameras can be integrated with alarm systems. If a camera detects movement, it can trigger an alarm and send notifications directly to a designated person or an alarm receiving centre.