How do security camera systems work

A surveillance system sends the videos from the security cameras installed in different places to a monitoring center where it is possible to monitor everything in real time and record the footage to have evidence.

It works in different situations, from home monitoring to applications with thousands of cameras installed in cities, factories, hospitals, schools, laboratories and any other environments that require monitoring and recording, whether for safety or process control.

Security system surveillance station

With security camera surveillance systems, operators can watch what happens in front of each camera and react if something goes wrong.

==> It's important to understand more about CCTV cameras, so I highly recommend you to read the article: How CCTV cameras work.

The evolution of the surveillance systems

Below a quick description of the surveillance systems used over time, from the basic analog cameras and recorders to the modern digital  IP systems.

1. Analog system with Time Lapse recording

The cameras generate analog signals and send them to an analog recorder (VCR) that stores the information in analog format, this technology is very old and no longer used in new surveillance projects.

Digital Video Recorder (DVR)

2. Hybrid system with computer recording

The cameras generate analog signals and send them to a computer which uses a capture card and a software which converts the signals from analog to digital and record on the hard drive.

Computer used to record surveillance cameras

3. Hybrid system with DVR (Digital Video Recorder)

The cameras generate analog signals and send them to a digital video recorder which converts the signals to digital to store the information into a hard drive.

DVR Digital Vide Recorder

4. IP system with NVR (Network Video Recorder)

The cameras generate digital signals and send them to a digital video recorder which converts the signals to digital to store the information into a hard drive.

NVR Network Video Recorder

Analog surveilance system fundamentals

A simple analog surveillance system consists of cameras connected to a recording equipment known as DVR (Digital Video Recorder) that converts the signals from analog to digital format for recording and monitoring over the network.

Once the signal is digital, it can be stored on a hard drive or sent over the network. See the diagram below:

CCTV Diagram

In the first block, it is possible to see analog cameras of different types such as box, dome, PTZ, and bullet. They are connected to the DVR using coaxial cables

The analog signals are converted to digital video and recorded on the DVR. The digital video is also displayed on a computer’s monitor (monitoring station).

A UTP (Unshielded Twisted Pair) cable also know as “network cable” or “cat5 cable” is used to connect the DVR and the monitoring station

Traditional analog surveillance cameras have their resolution measured in TVL (TV lines) which are converted by the DVR into digital information (known as pixel).

CCTV Diagram Analog to Digital conversion

How to connect an analog camera to the Internet

To send videos over the Internet is necessary to convert it to digital, so an analog camera must be connected to a DVR before sending the video over the network.

CCTV Diagram Internet connection

Digital surveillance system fundamentals

Digital surveillance cameras (also known as IP cameras) send digital signals to the recorders, so there's no need to convert from analog to digital since this job is done directly by the IP camera itself.

The video can be recorded into a NVR (Network Video Recorder) and also sent to the Internet as shown in the following diagram.

IP CCTV Diagram

At the left side you can see an IP camera connected to the recorder (NVR) by using a network cable (also known as UTP cable or cat5e cable).

The NVR can power the camera up by using the PoE (Power Over Ethernet) standard.

==> To learn more about PoE, read the article: PoE switch for IP cameras

A router is used to connect the NVR to a laptop, mobile device and the Internet.

Analog x IP surveillance systems

There are pros and cons for both surveillance systems.

If you need record and monitor your home or small business, a basic analog surveillance system could be the right choice for you, specially if you are on a budget since the price for such systems are cheaper.

Analog cameras and recorders are easy to install and setup and just require basic skills, however there are some limitation regarding camera resolution and features when compared to an IP system. 

IP surveillance systems are a little bit more complex to setup since they require some computer network skills. If you have some problems with the cameras, you need to dig into IP address configuration and other technical stuff.

Besides the higher price tag, an IP system can use cameras with higher resolution and intelligent features such as face detection, license plate recognition, etc.

==> To learn more, read the article: IP Camera Advantages Over Analog System


Camera surveillance systems are largely used in different situations and bring a lot of interesting advantages to the users.

Consider learn more by reading the Ultimate Security Camera Guide.

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Ultimate Security Camera Guide