Original sentence: " In colloquial British English, a PA system installed for public address in a building is sometimes referred to as a "Tannoy" system after the company of that name.Intercom systems, also have microphones in each room so that the occupants can reply to the central office.PA systems with a larger number of speakers are widely used in institutional and commercial buildings, to read announcements or declare states of emergency.Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars