Abstract: The coupling comprises a male plug (3) and a female element (2). A retaining latch (20) for retaining the plug (5) in the female element (7) is movable between a first position in which said latch (20) is capable of retaining the plug (5) engaged to a first depth in the female element (7) in which it is connected in leaktight manner to said female element, and a second position in which said latch (20) is suitable for retaining the male plug (5) engaged to a second depth that is smaller than the first depth. The latch (20) is configured in such a manner as to be returned (F3) towards the second position at least in part by positive pressure in a passage (4, 17, 26, 34) for purging the downstream pipe when the plug is at the second depth. In a variant embodiment, the coupling includes an adapter that the latch is suitable for retaining.