Rail King 4-6-4 Dreyfuss Locomotive Operator's Manual page 6

Manual Volume Control
To adjust the volume of all sounds made by this engine, turn the master volume control
knob located under the tender clockwise to increase the volume and counter-clockwise to
decrease the volume.
Proto-Sound 2.0
Volume Adjustment Knob
Figure 4: Manual Volume Adjustment
6 RailKing Dreyfuss Steam Engine