A data transmission system includes a transmitter and a receiver. The transmitter mixes an original clock signal and an original data signal to generate and output a hybrid differential signal, the hybrid differential signal having multiple clock pulses and multiple data pulses. At lease one data pulse occurs between two clock pulses, and the period between two clock pulses corresponds to the frequency of the original clock signal. The clock pulses and the data pulses have different differential swings. The receiver receives the hybrid differential signal via a bus and generates a recovered clock signal and a recovered data signal based on the hybrid differential signal. The hybrid differential signal, the original clock signal and the original data signal are reduced swing differential signals.