The ERCO Professional Net is a flexibly modular system which can handle virtually all requirements demanded of a professional lighting control system. Other systems, such as heating/ventilation/airconditioning, blind/daylight-control systems, can be connected via standardised interfaces and controlled via Professional Net operating elements. A comfortable LNSbased system plug-in is available for the installation. The Professional Net is a strictly hierarchical ordered system (which as far as possible, is also shown in LNS).