I want to install a monitor in the shop, with an area of more than 20 square meters. How many cameras do I need? Where can I buy it in Beijing?

Four is enough, one at the door and one at the cashier. You can put two in the shop as needed. You have a computer that cannot be connected directly. You need a 4-channel video capture card. The price of the camera varies according to the definition. Cheap about 200, expensive 6-70 1. You also need wires, a power supply for the camera and a hard drive for the computer. Without 1TB,