POWER TRANSMISSION SYSTEM CAPABLE OF SYNCHRONIZING POWER TRANSMITTER APPARATUS HAVING MULTIPLE OPERATION MODES, WITH POWER RECEIVER APPARATUS HAVING MULTIPLE OPERATION MODES

A current meter measures a current value associated with input power inputted to a code modulator. A code modulation circuit modulates the input power to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmits the code-modulated wave to the code demodulator via a transmission path. A control circuit controls the code modulation circuit. The code modulation circuit has operation modes different from each other depending on a direction of the input power, and a direction of the code-modulated wave to be generated. The control circuit generates waveform information indicating variations of direction of the input power over time, based on the current value measured by the current meter, and determines the operation mode of the code modulation circuit based on the waveform information.