What are the key features of a smart home system? Your response should contain less than 300 words. Your answer must contain a title, wrapped in double angular brackets, such as <<poem of joy>>. Highlight at least 2 sections in your answer with markdown, i.e. *highlighted section*. Include keywords *automation*, *security*, *energy efficiency*, *voice control*. At the end of your response, please explicitly add a postscript starting with *P.S.*.

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