This is a door alarm circuit.I have used a magnetic-reed switch for this.When the door opens the buzzer will give a beep beep sound.Changing R2 and C2 The period of generating beep sound can be changed.According to the values of this circuit you can get that sound for 4 or 5 seconds.double the value the you can double the time.Note
# this circuit operate with 9V battry.
#Build this circuit on a PCB
