For engineer training, the two dual mode electro/diesel locomotives Gem 4/4 # 801 and # 802 of the RhB in multiple control circulated on the Arosa line, as train 9439 from Chur Sand to Arosa, near Langwies. The locomotives are capable to run under the 1000 V DC of the Berninaline, on the main network electrified with 11000 V 16,7 Hz AC the diesel is used.
