Train event recorder

A train event recorder – also called On-Train Monitoring Recorder (OTMR), On-Train Data Recorder (OTDR), Event Recorder System (ERS), Event Recorder Unit (ERU), or Juridical Recording Unit (JRU) – is a device that records data about the operation of train controls, the performance of the train in response to those controls, and the operation of associated control systems. It is similar in purpose to the flight data recorder or black box used on aircraft.