A communications apparatus having an RF signal processing device, a baseband signal processing device and an access control module is provided. The RF signal processing device transmits and receives an RF signal and processes the RF signal in accordance with a predetermined protocol to generate a first signal. The baseband signal processing device is coupled to the RF signal processing device and processes the first signal. The access control module controls operations of the communications apparatus in at least a station mode and an AP mode. The access control module issues a first indication signal and a second indication signal under the AP mode so that the RF signal processing device and the baseband signal processing device are switched between a first power level and a second power level in the AP mode.