An air-conditioning system for airplanes is proposed in which a portion of the fresh airflow to be prepared is tapped at high pressure from a power unit and another portion is sucked in from the surroundings. A common clock is connected to at least two subsystems of the x-ray emitterdetector system to enable a plurality of noise sources associated with the at least two subsystems within the x-ray emitterdetector system to be correlated with the common clock. An equipotential region is substantially maintained around the desiccant.