Abstract: A contactless inductive data transmission system provides bidirectional signal transfer between a sending-and-receiving station and one or more batteryless transponders. A high-frequency signal from the sending-and-receiving station is pulse width modulated for data transmission to a transponder and provides a system clock, which is extracted in both the sending-and-receiving station and in the transponder for synchronization, and provides the electrical power for operation of the transponder. The pulse width modulated signal is demodulated in the transponder for triggering a response wherein a modulating signal is applied by load modulation to the pulse width modulated high-frequency signal to form an information-carrying load modulated high-frequency signal, which is demodulated in the sending-and-receiving station.