With the introduction of the light steel wagons, the SBB planned to operate the city express train between Geneva and Rorschach with short, light trains. For this purpose, three baggage railcars were initially ordered, which had an output of almost 1,000 kW and a top speed of 125 km/h. Thanks to the BBC spring drive, good suspension properties could be achieved at higher speeds. Since the space required for the electrical equipment was limited due to the relatively low output, there was sufficient space in the car body for the luggage compartment.

During the Second World War the volume of traffic increased sharply and it was not to be expected that it would decrease again after the end of the war. Although the RFe 4/4 had multiple controls and gangways, operation with two or three baggage railcars distributed across the train was not optimal. Thus, the development of a pure, more powerful electric locomotive was commissioned, from which the Re 4/4 I emerged.

Thus, no further orders followed and the three pieces were sold in 1944. Both new operators underwent a conversion of the railcars, during which some problems that had arisen were fixed and the maximum speed was reduced to 90 km/h with a new gear ratio. The weight had increased by 3.5 tonnes. With the conversion, the designation was changed to Fe 4/4 and from 1962 it changed to De 4/4.

The first example with the number 601 ended up on the Bodensee-Toggenburg railway and was used there until 1977. Then it came to the Sihltal-Zürich-Uetliberg-Bahn. It has been used as a historic vehicle since it was sold to the Oensingen-Balsthal-Bahn in 1994.

The other two examples, numbered 602 and 603, were sold to the Swiss Southeast Railway in 1944. Two suitable control cars were built there in order to be able to use them together with a motor car and a trailer as a shuttle train. The last use took place in 1993 and 1994 respectively. While the 602 was scrapped in 1997, the 603 is now owned by Swisstrain together with the 601 and serves as a spare parts donor for them.