The accumulator railcars of the ETA 150 series were very popular among passengers due to their excellent ride comfort and low noise levels. A total of 232 units were built from 1954 to 1965. Additionally, 216 control cars of the ESA 150 design were put into operation. The railcars, which were primarily used on flatland routes, were also affectionately referred to as "Flashlight Express," "Socket InterCity," or "Accu Blitz." Their operational area included Augsburg, Schleswig-Holstein, eastern Lower Saxony, Rhineland-Palatinate, southern Hesse, and the Ruhr area.