phone line wakes Mac Mini

I've discovered with with the keyboard and mouse unplugged, I can wake my Mac Mini by picking up the telephone. When I hang up, the computer wakes up.

If I find my computer awake when I come home, I suppose it's because my phone rang in the last few minutes.

Are all Mac Minis like that? Should I disconnect the phone line when I leave? That would keep it from waking up and provide lightning protection.

Thanks, that was easy! I'd been to Energy Saver but overlooked the Options button.