The indoor shield must be able to protect the camera and lens from dust, impurities and corrosive gases, and at the same time to meet the installation site to achieve the purpose of anti-damage. The indoor shroud is usually made of painted or anodized aluminum, painted steel, brass or plastic. If plastic is used, use fire-resistant or flame-retardant. The protective cover must have sufficient strength, the installation interface must be strong, the window should be clear and transparent safety glass or plastic (polycarbonate). The design of the electrical connection port should be easy to install and maintain.