Brush class 47 sound decoder and speaker (Bachmann 21-pin model)

`OO` variant for the Bachmann 21-pin model as this has different motor characteristics to the Heljan model. Below is a list of the Function keys and their assignments applicable to this model. F0. Lights on/off F1. Sound on/off F2. Horn 1 F3. Horn 2 F4. Horn 3 F5. Buffer up F6. Coupling up F7. Flange squeal F8. Air ‘tick’ F9. Wheel/track ‘groan’ F10. Carriage door slam F11. Guards whistle F12. Shunting mode (half speed) F13. Acceleration/Deceleration. Press once to over ride, press again to cancel. F14. Aux 1 F15. Aux 2