A medical connector (18) has a visual signal (67) formed by a coloured screen-applied band arranged on a bolt (63). In a correct engaged position of the bolt(63) with an external element, the signal is visible. In an incorrect engagedposition, the part of the bolt (63) bearing the signal is lowered, so that the signalis hidden from view, providing an indication of a faulty situation. The medicalconnector serves to connect the end of a dialysate supply tube to an inlet portof a dialyser.
