What is the difference between 3-point & 4- point starter ?

What is the difference between 3-point & 4- point starter ?

The basic difference between between 3-point and 4-point starter is the connection of no volt coil(NVC).

In 3-point starter NVC is connected in series with field winding,  while in 4-point starter NVC is connected independently across the supply through fourth terminal called (L-).