Selling Atomic Clocks for the past 20 years. Atomic clocks are designed to keep accurate time by using the governments signal in Boulder Colorado which resets all the atomic clocks all over the USA every night. Double sided ceiling or wall hung clocks are great for the hallways of schools, churches or hospitals. 14" and 16" wall hung clocks are great for classrooms and even gyms. The clock guard is perfect for your school's gym clock guard to protect your atomic clock. We do not recommend using in basements with no windows. It is best to have above ground with a window for better reception.