MCU P1.0 output with the audio signal 1KHz and 500Hz-driven alarm sound speaker output for alarm signal to require 1KHz signal ring 100ms, 500Hz signal ring 200ms, alternately, P1.7 then a switch to control, when the switch together on the ring alarm signal, when the switch off warning signals to stop, to compile the program.

单片机报警器电路图1

单片机报警器电路图2

单片机报警器电路图3