There are basically two categories of machines, namely "Lock-out spring" and "Constant Pull" Lock-out string: Hand crank machines (manual) and motorised pull(belongs to the early stages of electronic stringing machines) Constant pull: Drop weight machines (manual) and Electronic Constant Pull (Also known as ECP, belongs to the later developments of stringing machine) Both categories have manual and electronic machines with different features and performance. One of the factors that different machines would affect is the stringbed stiffness of the racket.
