The overall control architecture serving the European Tritium Handling Experimental Laboratory (ETHEL) consists of two types of apparatus:1) Programmable Logic Controllers (PLCs), Personal Computers (PCs), networks which constitute the so-called Distributed Digital Control System (DDCS); 2) Fail-safe hard-wiring which operates independently of the DDCS. This paper deals with the first type of apparatus; its hardware and software are described. The computerized system, defined by a four-level hierarchical and modular architecture, is a large distributed Real-time Control System. The operation is mainly centralised in the Control Room through a fully programmable man-machine interface (graphic displays, trends, etc.).