the invention relates to a modular connection system for industrial applications having electronic modules which have at least one data distribution device and can be mounted on a mounting rail . the electronic modules have a plurality of connections , which can be contacted via universal module locations , wherein a databus and a power supply connection are located between the electronic modules mounted on the mounting rail . connection modules are attachable to the module locations of the electronic modules and can be fastened there mechanically to produce an electrical connection between optical or electric cables and the connections .