The 21 modern FLIRT3 four-car low-floor units from the manufacturer Stadler, which are equipped with AMiT diagnostic HMI, are gradually brought into full operation in Serbia from second half of last year continuously. These rugged panel computers of the APU series collect and display the diagnostic data of vehicle technologies for the whole trainset. The EMU units is operated by the Serbian national train operator Zeleznice Srbije in the regions around Belgrade.