The SM 1525 motor and single reduction gearbox is a smaller version of the 1532 motor, being 15mm. wide and 25mm long for use in very small locomotives. A 22.0 mm diameter flywheel is an optional extra on these units.

The SM motor has a skewed armature, 2.0mm shaft, a no load speed of 8,500 rpm (+/- 10%), and a rated current of 90mA.