Briefly, in accordance with one embodiment of the invention, a differential digital-to-analog converter utilized in a transmitter path of a transceiver utilizes a differential R2R architecture. Thereby, stable pick up accuracy can be ensured by calibrating an aging variation of the coordinates system owing to thermal elongation or contraction of the camera moving mechanism. A main database maintains the first data set. The AT sends an IP packet to a correspondent node via a first mobile node external device.