Control of lighting apparatusses through switching modulation on a DC-bus

The system has a central rectifier unit (2) supplied with alternating voltage (9), at least one operating device (1-1'') for light sources (5-5'') and an external d.c. bus that supplies the at least one operating device for light sources with voltage starting from the central rectifier unit, whereby the central rectifier unit has a function for switching the central d.c. bus to at least two different values. Independent claims are also included for the following: (A) a method of central control of operating devices for light sources (B) and a computer software program product for supporting the inventive method.