How to make a home security electrical circuit.?

Hi, i'm trying to figure how to make a home security circuit. I can't figure how to make a buzzer go off if a door/window is opened. Am i right in thinking i'm going to need a parallel circuit with with 2 resistors with a higher resistor above the door (higher resistor meaning with more resistance) and... show more Hi, i'm trying to figure how to make a home security circuit. I can't figure how to make a buzzer go off if a door/window is opened. Am i right in thinking i'm going to need a parallel circuit with with 2 resistors with a higher resistor above the door (higher resistor meaning with more resistance) and a lower resistor on the door for when the door's closed. Thanks
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