An answering device in a system for automatic wireless transmission of multi-digit information between interrogation devices and answering devices movable with respect to one another on movable carrier units having an energy supply, numbers of railroad vehicles being transmitted to stationary interrogation devices, each interrogation device emitting an interrogation signal altering its frequency periodically in a prescribed frequency band situated in a microwave range from which the answering device selects frequencies assigned to the information as it moves past by means of resonators comprising high frequency cup-shaped line resonators, said resonators being tuned to the resonance of said frequencies for returning a prescribed number of answering frequencies to the interrogation device for each digit of the information, each answering device having a high frequency line section to which the resonators for the frequencies to be selected are respectively coupled, tuned resonators being provided for all of said frequencies, said resonators being individually switchable inoperative for setting up the multi-digit information by strong damping, a microwave PIN diode coupled in each resonator for damping the resonator by applying control voltages to the microwave diode, said diode being provided as a diode-chip integrated in an inductive coupling element insertable into an aperture in a bottom of the cup-shaped resonator.