To provide a data transmission system where power consumption required for transmission is reduced with respect to data at a high transition rate similarly to the case with data at a low transition rate.

The data transmission system 200 has a transmission circuit 210, a reception circuit 250, and a transmission line 10 that is connected between the transmission circuit 210 and the reception circuit 250. The transmission circuit 210 encodes data D0 to generate coded data D1 and outputs the coded data D1 to the transmission line 10. The reception circuit 250 receives and decodes the coded data D1 from the transmission line 10, decodes the data D1 to produce the data D0 and outputs the decoded data D0 to an output terminal 252.