Loksound 5 sound decoder for the real track or EFE 143 and 144
In the EFE model its easy to fit, one screw gives you access to the next18 decoder. In the Realtrack model it fits under the floor in the non motorised end, so the model needs to be disassembled to fit it.
Use the built in speaker on the EFE model or choose a FREE speaker upgrade from the list.