This circuit is a simple laser anti theft alarm with SCR, laser, LDR and a few other components.When the theft body cut the laser beam, the buzzer turns ON and latch (stay ON) until the Reset button pressed. I designed the PCB in the shape of tiny house (my YouTube channel logo)Parts list:BT169LDR (3pcs)Laser 5V 5mW (3pcs)Buzzer10K PotentiometerPush button Youtube video: https://youtu.be/5gywcE4WEwk