For `re-built` locos we recommend that both decoder and speaker are fitted in the tender due to space (please remember decoders can get hot) and sound considerations. Four wires will need to be run through to the loco for pick-ups and we would recommend a connector so that the loco and tender can be separated. `Un-rebuilt` locos have room to accomodate both decoder and speaker within the streamlined loco body although we suggest the use of speaker 50334 to improve sound levels. Below is a list of the Function keys and their assignments applicable to this model. F1. Sound on/off F2. Long whistle (latched) F3. Short whistle F4. Buffering up F5. Coupling up F6. Injectors F7. Drain cocks F8. Safety valves F9. Guards whistle F10. Carriage door ‘slam’ F11. Wheel/track ‘groan’ F12. Fireman shovelling F13. Shunting mode. Press once the loco goes slowly, press it again and you are back to normal control. F14. Acceleration/Deceleration override F15. Aux 1