ALn 556 # 1202 of the Ferrovie dello Stato (FS) in the italian national railway museum of Pietrarsa. The diesel railcars of the ALn 556 group, built by FIAT, are the natural evolution of the earlier ALn 56 project, developed starting in 1936, when it became apparent that there was insufficiency of a single rolling stock to carry out the passenger services whose users had rapidly increased. In order to couple a second railcar to it, it was necessary to have another driver at the wheel which, combined with the need for another agent in the carriage, made the economic convenience of using railcars completely disappear. A multiple control device was therefore devised that would allow their use from a single driving bench. To indicate multiple-command coupling of a railcar, it was decided, by convention, to double the first digit of group identification; thus ALn 56 became ALn 556. The series was put into service in 1937 and continued to be given the nickname Littorina. The ALn 556 were built between 1937 and 1939 in 192 units divided into two subseries with differences in motorization; the first subseries included units 1201 to 1299 and the second subseries included units 1300 to 1392.