AT89S52单片机P1引脚外接独立式按键S1-S8，分别代表数字键0-5、确定键、取消键。单片机从P3.0-P3.3输出4个信号，分别为1个电磁开锁驱动信号和密码错误指示、报警输出、已开锁指示信号，分别用发光二极管L1-L4指示。P3.4接一有源蜂鸣器，用于实现提示音。

-AT89S52 microcontroller P1 pin external standalone buttons S1-S8, respectively represent the number keys 0-5, OK button, Cancel button. MCU P3.0-P3.3 output from four signals, respectively an electromagnetic lock drive signals and password error indication, alarm output, has unlocked indication signal, respectively, with light-emitting diodes L1-L4 instructions. P3.4 connected to an active buzzer, for the realization of tone.