A method is provided which protects persons in the vicinity of a high frequency field-emitting device, in particular a European train control system antenna of a rail vehicle. A photo-detecting element for detecting light emission of light emitting element and a resistor is connected in series and a threshold voltage of the transistor is detected by the voltage of the node. Multiple element definitions and groups of elements are identified. The remote monitoring interface may include a plurality of status icons respectively representing the plurality of remote patient monitors. The folding base unit folds the first unit on top of the second unit.