In order to detect gravitational waves, the kilometric interferometer Virgo needs an active control of the positions of the suspended optical components, keeping the detector at its working point. The constraints are about 10-10m RMS for the longitudinal control (“Locking”) and 10-9rad RMS for the angular degrees of freedom (“Alignment”). A dedicated hardware and software named Global Control is in charge of the Locking and the Alignment loops for the Virgo experiment. This system has been designed to match the synchronization constraint and provide a flexible tool in order to easily integrate the various algorithms needed for the control of Virgo. This paper presents the technical requirements to be fulfilled by the Global Control. Then, the dedicated hardware is described and the overall architecture of the Global Control is shown.

proposes a highly scalable and flexible environment for managing software configura- tion. Its applications range from individual developers, willing to work on simple test applications up to large software base management such as the ones usually found in large HEP experiments. permits to develop a project-specific organisation for software as well as for team operations, provid- ing simple mechanisms for groupware activities, iterative integrations, public releases, inter-project relationships. provides a high level abstraction for configuration items (packages, libraries, ap- plications, documents, build and run parameters, etc...) which can be specified in a simple language and queried upon for control operations. This approach allowed in particular to transparently make interoperate several different configuration related tools (such as 'make' in the Unix world, CVS or VisualStudio in the PC world) so as to let non-experts users mostly ignore them. For more expert users, powerful mechanisms are provided for extending the knowledge base. A really open ar- chitecture has been selected for implementating , which makes it easy to interface to a wide range of environments. is currently successfully used by several HEP experiments either as a production tool or for evaluation (eg. Virgo, LHCb, Nemo, Auger, Opera, Atlas).