说明：  no intro
(51 Single-chip electronic calendar electronic calendar, time display, alarm, date, and keyboard settings feature stopwatch function keys A: Set-digit+ 1 alarm mode switch for the alarm clock stopwatch timer mode switch for function keys B: Set-digit-1 for the alarm clock mode switch function keys C: set mode and set the stopwatch mode select button function keys for Clear D: in the four work mode switch set alarm switch)