Which of the following is the focus of Article 820?

Article 820 of the National Electrical Code (NEC) specifically addresses the installation requirements for community antenna television (CATV) and radio distribution systems. This article outlines the necessary safety standards and guidelines to ensure these systems are installed correctly and function effectively.

In the context of the NEC, community antenna systems and radio distribution systems require specific wiring practices, grounding methods, and other considerations to prevent hazards such as electrical shock or fire. The regulations established in Article 820 ensure that both the equipment and the installation meet the necessary safety and performance criteria, thereby protecting users and maintaining the integrity of the systems.

Other options, such as network optimization strategies, data communication standards, and residential electrical wiring, fall outside the focus of Article 820. They are addressed in different articles within the NEC, each tailored to cover specific areas of electrical installations and standards. Thus, the choice of community antenna television and radio distribution systems is the correct focus for Article 820.