Digital alarm clock circuit using 3817

describe:

U1 is a 3817 integrated circuit produced by Fairchild Corporation. It has the ability to directly drive the display, can display 12H or 24H, can sound an alarm clock on time, and automatically turn on the radio on time . The display is a FND500 light-emitting diode, and the input frequency can be 50HZ or 60HZ. U1 is a 7800 series voltage regulator, and its rated power can meet the requirements of all radios. The user can select the length of time the radio plays, at which time Q3 will output a low level and automatically turn off the radio . When the alarm clock comparator detects whether an alarm sounds or not, an alarm clock tone signal is output.