NFHS 5-6-2: "ART. 2 . . . Each quarter or extra period ends when the
signal sounds indicating time has expired."
NCAA 5-7-2: "Art. 2. Each period shall end when the red light or LED lights has become activated. When the light fails to operate or is not visible, each period shall end with the sounding of the game-clock horn.
a. In games when the red light is not present, the game-clock horn shall terminate players’ activity."
I could tell you a dreadful and boring story about how I own this rule, but I'll spare you. Now you own it too.