Disclosed is a data transmission system to transmit digital data through a wireless transmission path, including: a first device including a communication condition detecting section, a data supplying section, a bit-rate converting section, a transmission buffer, a transmission communicating section and a channel switching section; and a second device including a reception communicating section, a reception buffer and a buffer storage amount detecting section, wherein the communication condition detecting section comprises a jamming detecting section, and when the jamming detecting section detects jamming, the bit-rate converting section lowers bit rate of the digital data to predetermined bit rate, and the channel switching section switches the communication channel to a channel where influence of the jamming is less, based on detection results by the buffer storage amount detecting section.