A plug-in unit with integral cable connection to the operating part of an endoscope and plug connections for lamps, mechanical, and/or electronic modules is characterized in that a hollow tube extending to the distal end of the endoscope is inserted into the plug-in unit by the integral cable connection and the operating part and has its proximal end positioned so that it is freely movable in the plug-in unit in such a way that can be conducted out of a closeable bore-hole in the wall of the plug-in unit.