Uhlenbrock 20075 Transformer 70 VA 12 / 15V Connect the Intellibox II (or Power 4, Intellibox Basic) to the 12 Volt output for N scale. In this way non- NMRA compliant N scale decoders are not damaged. For bigger scales connect the 15 Volt output to the Intellibox (or Power 4, Intellibox Basic). Track voltage is 21Volts on the 15volt windings of the 20075 transformer (Brown and Yellow connections) The track voltage is 17volts when attached to the 12volt windings of the 20075 transformer (Brown and White Connections). The lower voltage is more suitable for N Gauge layouts.