singlechip also call single-chip microcomputer,it is a sort of micro-controler integrated by CPU,RAM,ROM,timing,counting and varieties of interfaces.the 51 singlechip is the most typical and representive one thereinto,it has extensive application in all realm.the topic has designed a sort of music doorbell which is controled by the singlechip AT89S51.the music doorbell system is consisted of the singlechip small system ,extand LED display and the sound circuits.programing with singlechip assemble language,reach the result of alarming when pressing the button,and displaying note synchronism回头再译