Well, there it is. I made up a circuit that plays one of nine tracks at random, with selectable intervals. Two sounds can be triggered by the IR detectors which will go out of sight beyond the end of the layout. A whistle as a train enters the station and a different one as a train approaches the traverser.   The whole lot is sat neatly in  an old pa amplifier case with its own mains power supplier. This seems to make it immune from transients on the railway itself triggering sounds. T