A method and an apparatus distinguish the origin of operator inputs in electronic control systems having at least one first operating element and at least one second operating element. A first signal is processed in the electronic control system when the at least one first operating element is operated. The first signal differs from a second signal emitted by the at least one second operating element when the latter is operated, by virtue of an electronic identifier assigned to the at least one first operating element. A printing machine having the apparatus is also provided.