Abstract: An installation coupler is disclosed for connecting a first cable (306) to a second cable (330) in and installation for supplying power to at least two workstations (322) via a free set of plug pin socket contacts (314) and via the second cable (330). The first cable (306) has a double female installation socket (300) with two sets of contacts (314) and the second cable (330) has a male installation plug (304) that can be plugged into at least one of the sets of contacts (314), with a predetermined orientation of the plug (304) relative to the set of contacts (314). The installation plug (304) includes a protruding stop (307) that partly obstructs the lower one of the sets of contacts (314) when the plug is incorrectly connected to the upper set, and that is clear of the contacts (314) when the plug (304) is correctly connected to the lower set. The protruding stop (307) thus prevents the simultaneous connection of the plugs (304) of more than one second cable (330), to the double female socket (300).