The Digitrax Sound Bug is a sound only decoder and is designed to piggyback onto a 165 series Digitrax decoder. As there is not a lot of room in the shay, you might want to consider the Soundtraxx Micro Tsunami as a possibility. Here's a link to the specs: http://www.litchfieldstation.com/xcart/product.php?productid=999002769&cat=116&page=1 I would recommend the light steam version. If the above link is broken, you will have to cut-n-paste it
HTH,
Joe
HTH,
Joe