Patent ID: 7088267

Claim:
A duplex-system digital data transmitting apparatus comprising: first receiving means for receiving a digital signal from a digital source; converting means for converting the digital signal into a signal in a form that is transmittable through a human body; frequency-modulation means for frequency-modulating the digital signal into a signal in a band that is transmittable through the human body; transmitting means for transmitting the frequency-modulated signal to the human body; second receiving means for receiving the frequency-modulated signal from the human body; reconverting means for reconverting the signal transmitted through the human body into the original signal by use of a receiver; demodulating means for demodulating the received frequency-modulated signal into the original digital signal; output means for outputting the demodulated digital signal; wherein transmission of the signal to the human body and reception of the signal from the human body are performed using a duplex transmission system; wherein said frequency-modulation means includes a function for performing frequency modulation in a plurality of different frequency bands, said demodulating means demodulates the frequency-modulated signals in the frequency bands; wherein data rates of transmission channels formed by modulating the frequency bands are different, and one transmission channel is used to monitor a connection state for maintaining group delay and phase characteristics of another transmission channel, thus maintaining connection quality of the other transmission channel; wherein the transmitter includes a first level converter circuit which converts a level of the digital signal, and wherein the receiver includes a second level converter circuit which converts a level of the signal from the human body.