Depending on the RR, the hot box detector will read out over the radio whether it has found a defect, what axle number it counted it to be on, and the total number of axles counted. It uses a pyrometer to "measure" the temperature of the bearings as they go by, although they aren't particularly accurate and are subject to variances due to environmental conditions. If the detector indicates that it has found a hot bearing, the engineer will stop the train, walk and count back to that axle, hold a special wax crayon on the suspect bearing, and if the wax melts, they have to set out the car. Usually the hot box detector will be associated with a dragger detector as well, and in some places will have other hazard detectors.