In 1930, the Bodensee-Toggenburg-Bahn (BT) ordered six four-axle mixed-traffic locomotives with a low axle load from SAAS, with the mechanical part being provided by SLM. They were inspired by the ÖBB class 1170 and had an output of 1,200 kW. They had two two-axle bogies and all axles were powered by one traction motor each with a Sécheron quill drive. In this configuration they were also suited for express services with a top speed of 80 km/h on lightly built lines. With an axle load of 16.5 tonnes, the maximum tractive effort was 137 kN.

After the Emmentalbahn (EB) and the Solothurn-Münster-Bahn (SMB) had been electrified, they ordered four and two of the same basic construction. When the Burgdorf-Thun-Bahn (BTB) was switched from three-phase to single-phase, they ordered two more. After the EB and BTB merged into the Emmental–Burgdorf–Thun-Bahn (EBT), one additional locomotive each was ordered in 1944 and 1953. All these were a bit lighter and had a lower tractive effort.

Initially the Be 4/4 was used in passenger and freight service and later also in express service. From 1945 they were rebuilt with regenerative brakes and train control systems. In the sixties they also received multiple controls and were used double-headed with heavy freight trains. With the introduction of more modern locomotives and multiple units in the eighties, the Be 4/4 was only used in freight and shunting service. After their withdrawal in 2000, three have been preserved in working order with six more either on display or earmarked for possible restoration.