A fan control system for controlling a fan to dissipate heat from an electronic device includes a current detection circuit having a shunt resistor to receive current, a signal amplification circuit having an operational amplifier, and a switch circuit having an npn transistor and a pnp transistor. For example, a method in accordance with an embodiment of the invention may handle a data block of a received signal based on an estimated cross-correlation between co-channel interference and the received signal. In one embodiment the detections zones are defined by Bluetooth signals. Meanwhile, the power supply has a larger usable space therein. The sheath comprises a cylinder having an inner wall and an outer wall.