A system of computers connected by a local area network(ARCNET®)controls the Munich accelerator facility. This includes ion sources, the tandem accelerator, the beam transport system, the gas handling plant, parts of experimental setup and also an ion source test bench. ARCNET is a deterministic multi-master network with arbitrary topology, using coax cables and optical fibers. Crates with single board computers and I/O-boards (analog, parallel or serial digital), dependent on the devices being controlled, are distributed all over the building. Personal computers serve as user interfaces. The LAN communication protocol is a client/server protocol. Communication language and programming language for the single board computers is Forth. The user mode drivers in the personal computers are also written in Forth. The tools for the operators are MS-Windows applications, programmed in Forth, C++ or Visual Basic. Links to MS-Office applications are available, too. ©1999 American Institute of Physics.