Originally, the Hardanger Line used Class 64 electric multiple units. On 28 March 1940, NSB sent an invitation to tender for two multiple units which would be similar to Class 64. The company asked both for aluminum and steel bids. However, NSB abandoned the plans and instead signed an agreement on 4 October 1940 for delivery of three electric locomotives. The units were intended to be delivered in 1942. The mechanical components and assembly was done by Thune, and electrical parts were delivered by NEBB, except the transformer and electric controllers, which were built by Per Kure.