++《PHILIPS 音频系统手册》Sound System Reference Manual Public Address Sound Reinforcement Philips Communication & Security Systems Breda The Netherlands Tel (+31) 76 5721 407 Frans van der Meulen 1958 Jubilee Edition 1998 Sound System Reference Manual Introduction Sound systems are used for amplification of speech or music to enhance intelligibility or loudness by electro-acoustic means in order to serve an audience with a higher degree of listening comfort. A public address distribution system is designed primarily to carry live and recorded messages, signal tones and background music (if required), from several different sources, to a number of selectable remote areas. Common applications would be: hotels, restaurants, railway stations, airports, factories, oil platforms, office buildings, schools, shopping……