get one verizon window/door sensor. take it apart at the seams (it's not glued and does come apart. Take out the circuit board and under the board you will find the N.O. mag switch. Solder wires on both sides of the switch being very careful and not using a blowtorch! extend the wires out of the plastic cover.. Now go to radio shack and buy the alarm magnetic burglar switches..make sure they are the normally open kind. get switches for how many windows you want. Wire them in a loop.. Now when the window opens, it closes the circuit and Viola, the alarm is activated...