Camera’s basic function is to transmit what it 'sees' to a recording device, as well as to a user. Camera is the eye of the video surveillance system. Digital cameras record images through a CMOS or CCD sensor, whose quality also affects the quality of the recorded footage.

DVRs can be standalone, hybrid and server recorders. They all comply with the basic audio and video requirements, such as the conversion of signal from analogue to digital, compression, reproduction and network monitoring. All recorders use hard drive as storage.

Alarm centre is the brain of the alarm system. Depending on the model, it connects to a number of sensors/zones, processes data from sensors and gives out preprogrammed orders (sets off a siren, communicates with your phone or mobile).