There are two main types of gearbox. Manual gearbox and automatic gearbox.
Gear selector inhibitor
There are two different types of gear selector inhibitor - mechanical and automatic.
Automatic gearbox -- Geartronic*
The Geartronic gearbox has two different gear modes - Automatic and Manual.
Automatic gearbox -- Powershift*
The Powershift automatic gearbox transmits the motive force from the engine to the drive wheels with double mechanical clutch discs, as opposed to Geartronic which instead uses a hydraulic torque converter.
The function of the gearbox is to change the gear ratio depending on speed and power requirements.
Gear shift indicator*
The gear shift indicator notifies the driver when it is appropriate to engage the next higher or lower gear.