Difference between pneumatic, electro-pneumatic, and smart positioner

How is a pneumatic positioner different from a smart and electro pneumatic positioner

In a Pneumatic positioner, output comes from the pneumatic controller. The signal is 3 to 15 psi. positioner use flapper nozzle assembly to give O/P to the actuator

Electro-pneumatic positioner signal is 4 to 20 mA then goes to the flapper nozzle assembly

In a smart positioner, the signal is 4 to 20 mA. Flapper nozzle replaced by Hall-effect positioners and potentiometers