 The last systems were manufactured around 1995, although there are still a few GEC 4220 systems operating in 2018 with maintenance provided by Telent and some GEC 4310 were operating until 2013.The GEC 4000 series hardware and firmware included a pioneering facility known as Nucleus.Nucleus implements a number of features which are more usually implemented within an operating system kernel, and consequently operating systems running on GEC 4000 series systems do not need to directly provide these features themselves.