The ringing of a school bell announces important times to a school's students and staff, such as marking the beginnings and ends of the school day, class period, and breaks. In some schools it may take the form of a physical bell, usually electrically operated. In other schools it may be a tone, siren, electronic bell sound, a series of chimes, or music played over a PA system. In East Asian nations such as China, North Korea and South Korea, the Westminster Chimes pattern is commonly played as the bell.