Control whose program is specified by the type of functional elements and their connections (DIN 19 237).
With hard-wired controls, application-specific logical connections are made by individual pipeline connections of the linking components among themselves.
Although all signals can be processed in parallel as a result of this, changes and expansions to the program require more effort than when using a PLC.
VPS can either have a fixed program, i.e. they cannot be changed (e.g. through fixed wire or circuit board connections) or reprogrammable, i.e. they can be changed (e.g. through plug-in wired connections, diode matrices, punched cards, cross bar distributors, amongst others).
VPS has become far less significant in recent years, being replaced by programmable logic controls (PLC).