The present invention includes lithium manganese oxide spinel compounds having a low porosity, a high tap density and a high pellet density, and methods of preparing these compounds. An apparatus for performing the method is also disclosed herein. The rotor includes a rotor end face and at least one or a plurality of grooves. Switching between receiving antennas is accomplished by measuring power of a signal received from a mobile communication device at each receiving antenna, and selecting a receiving antenna based on the measured power. Also, a transmitter comprising at least one such optical network component is suggested. Then, the frequency of the clock signal outputted from the clock signal generator is adjusted in response to the control signal.