Matrix is an analog device mainly responsible for controlling the switching between front-end video sources and control lines. For example, if you have 70 cameras but only 7 monitors, the matrix can display any combination of 10 images on any of your monitors (automatic rotation); And the monitoring host is a digital video storage device. If you have 70 video sources, you need to equip a host that can record 70 channels. However, the more stable ones on the market have 16 channels (although many manufacturers promote 32 channels, the stability is poor). Therefore, if you want to record all the videos, you need to equip at least 5 16 channels and reserve 10 channels.