Embodiments of an apparatus and method for defending a physical zone from airborne and ground-based threats are disclosed. In the present invention, the host controls real time data writing by providing a signal requesting for information on a defective area to the device for recordingplayback of data tofrom an optical disk before providing a write command. In one embodiment, the induction heating system includes a control structure with a power supply and switches coupled to each of the inductive rings, wherein activation of the switches permits current from the power supply to flow to the corresponding inductive ring. Values after the decimal point are reflected to a counter, and thus the asymmetry can be detected more accurately to improve the performance.