[PROBLEMS] To provide a data communication system that can perform a light modulation of brightness perceivable to human eyes and that can perform high quality communication using illuminating light. [MEANS FOR SOLVING PROBLEMS] A PWM modulating circuit (11) creates a PWM modulation signal in which the pulse width has been adjusted in accordance with a light amount control signal corresponding to a desired light amount. The PWM modulation signal is sent to a phase inverting circuit (12). For example, when a transport data signal is 0, the phase inverting circuit (12) outputs the PWM modulation signal as it is. When the transport data signal is 1, the phase inverting circuit (12) inverts the phase of the PWM modulation signal and then outputs the phase-inverted signal. In accordance with this phase-inverted signal, a light source driving circuit (13) drives a light source (14), such as an LED or an organic EL, thereby causing it to emit a light. In a data receiver (2), a photo-sensor (21) converts the light irradiated from the illuminating apparatus (1) to an electric signal, and a phase detecting circuit (22) detects the phase from the electric signal and outputs the received data signal. ® KIPO & WIPO 2008
DATA TRANSMITTING APPARATUS