Manual Transmissions give the driver full shifting control. To change gears, the driver presses a clutch pedal, which disengages the engine from the rest of the drivetrain, and then uses a shifter to change gears. Depressing the clutch pedal generates hydraulic pressure in the clutch master cylinder, which applies the pressure to the clutch slave cylinder and disengages the clutch. A clutch cable performs the same function in older cars. The clutch assembly consists of a clutch disc, a clutch pressure plate, and a clutch release bearing. Since the 1960s, manual transmissions have grown from three to six speeds.