To detect hot boxes, hot axlebox detectors are installed on main lines and use infrared to detect any abnormalities when trains go by. If an abnormal temperature is detected, the HABD sounds an alarm in the signalbox in charge of monitoring the detector. The signaller then stops the train by putting the signals at danger and the driver cheques the axlebox and notifies the signaller afterwards, so that the appropriate course of action can be taken.