Attached are pics of Allan's 12volt Powertech Go Kart throttle that I am posting on his behalf.
The throttle pedal is connected what appears to me a PWM unit to control acceleration and give the 'soft start' required with the belt driven gearbox.
From the pics posted previously the automatic brake looks like an electronically actuated mechanical brake that works against the main drive gear. This would make sense as the motor would not be able to exert enough force through the drive belt to stop the vehicle.
Allan do you have any more information or pictures regarding this?