Method of and system for transmitting signals, e.g. control signals, request signals, interrogation signals etc. in a control system comprising at least two units, wherein at least one of said units is designed to operate as a master unit and wherein at least one of said units is designed to operate as a slave unit, whereby a plurality of channels may be used for the transmission, whereby a first unit performs the steps of detecting a vacant channel and transmitting a signal via said vacant channel, and whereby at least one other unit performs the step of scanning the channels for transmitted signals.