10-16 V AC/DC for prepared locomotives from Marklin, Trix, Brawa. Diameter 7mm. Same as Marklin 72270.

 For digital operations with older style decoders, where the smoke generator is permanently coupled to the track power, use Seuthe #24 (Marklin 0903). The Seuthe 24 smoke generator has a higher operating voltage of 16-22 volt. It has a green bottom.

On a digital layout, the track voltage is higher. A regular #20 smoke generator connected straight to track power would get too much power, and as a result, run too hot and burn too much smoke. If the generator is connected through the decoder, the voltage to the generator will drop. In that case you use this #20 or the Marklin 72270.