Implementations herein relate to an input/output (I/O) module which can be grouped to form several modules next to each other on a mounting rail, and which can be electrically connected to each other by means of blade/fork contacts. The blade contact element and the fork contact element of the blade/fork contact are designed in such a manner that it is not necessary to group the modules before the assembly on the mounting rail. Instead, subsequent I/O modules can be added to the top or the side of the existing group. Similarly, it is possible to take out or replace individual modules subsequently. Further implementations relate to electrical contact elements for achieving cross jumping between I/O modules. Here, for example, such electrical contact element may be designed as a combined blade-fork contact element.