The invention pertains to a modular data transmission system with several modules or bus nodes that can be arranged adjacent to one another in a row. The data transmission system comprises a first bus node that features a first transmitter for the wireless transmission of data and an electrical connector, as well as a second bus node that features a first receiver for the wireless reception of data and an electrical connector. Both bus nodes are detachably fixed on a mounting rail such that they are arranged adjacent to one another in a row. The first and second bus nodes are respectively detachably connected to a bus receptacle, wherein each bus receptacle features an electrical mating connector that is coupled to the electrical connector of the respective bus node in the connected state in order to transmit energy, as well as a positioning device for positioning the respective bus node.