Abstract: An electrical circuit for a model railroad includes a DC variable-voltage power source having a pair of output terminals connected to respective rails of a model railroad track. A capacitor and a normally-closed switch are connected in series across the output terminals. The improvement comprises an accessory circuit having first and second input lines, each connected to a separate one of the respective rails. The accessory circuit includes an AC-pass filter at the input lines and a rectifier section coupled to the AC-pass filter. A relay circuit is coupled to the rectifier section and includes an electrical contact switched between a first state, e.g., open, and a second state, e.g., closed. An electrically-powered accessory such as a whistle or horn is coupled to the contact and is energized when the contact switches from the first state to the second state.