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. Doors opening F5. Guards whistle F6. Doors closing F7. Driver/Guard buzzer F8. Flange squeal F9. Shunt mode F10. Acceleration/Decelleration override F11. Aux 1 F12. Aux 2 F13. Reverse gear clunk