An electronic trip unit for an electrical switch is disclosed which has at least one electrical connection, and which can be mounted in an electrical switch and in the mounted state interoperates with the latter for the purpose of tripping the switch and where, with the electrical switch in its built-in position, the mounted trip unit has at least one front surface facing towards the front, at least one rear surface facing towards the rear and side surfaces, and whereby with the trip unit in its mounted state at least one of the side surfaces is freely accessible, and where the electrical connection is located on one of the freely accessible side surfaces of the trip unit.