An apparatus for monitoring the operation of a railroad train includes two on-board units which collect and utilize data for ultimate transfer to a portable unit which can be carried onto and off of the railroad train. One of these on-board units operates under microcomputer control to compute speed, acceleration/deceleration, and distance traveled data and to store such computred data for subsequent transfer to the portable unit. The other on-board unit acquires additional data under separate microcomputer control. This data acquisition retrieves either binary or analog data, or both, and stores it in the acquiring on-board unit for later transfer to a separate memory in the other on-board unit for subsequent transfer to the portable unit. Power failure detection circuits are also implemented to insure the microcomputers are initiated in respective determinate states.