A removable hard disk loading device includes a hard disc tray including a first loading place for placing a hard disk of a first size, and an accessory capable of being placed in the first containing place, wherein the accessory includes a second loading place for placing a hard disk of a second size. The battery management circuit is coupled to a plurality of battery cells, controls an input of a first pin to correspond to an input of a second pin, and determines a level of a receiving current based on a receiving signal that is input through the first pin. Each remote activator module sends and transmits electromagnetic signals within the space of the retail environment. The power detector detects a transmitting power of the transmitting signal to generate a detected power signal. The first and the second pixel electrodes are connected to the first drain and the second drain, respectively. Thus, a handoff of a voice call involving the AT may be initiated from the circuit services network to the packet data networking prior to the AT establishing a call dialogue with the packet data network.