SFX004 Soundbug&trade; Sound Decoder for DH165xx decoders and others Are Plug N Play with any 165 series decoder Have Smart Power Management - no more booster or programmer shutdowns! Can function as a standalone Stationary Track-side/Under-layout sound decoder With Fully customizable Digitrax SFX sound capability. Includes 28mm 32 Ohm Speaker & 330uF Capacitor