Timed softeners backwash on a set schedule like every other day or every sixth day ect
The Fleck 5600 has been on the market for over forty years and has lasted the test of time as one was found recently still working after thirty nine years of operation.
The mechanical display makes it immune to power surges/lightning strikes etc.
The timed type is usually the preferred model on well water with very high iron. The reason being that iron needs a consistent backwash to be removed properly and to prevent fouling the resin. In this case the optional turbulator or fine mesh resin is recommended.