The device (10) enables a mobile milking unit of a milking system of "milk transport" type to be connected simultaneously to the milk main (16) and to the milking system vacuum pipe. It comprises a fixed part (14) clampable directly to the milk main, and a movable part (12) insertable into the fixed part (12). The movable part is provided with a connector (75) enabling either a pneumatic pulsator or an electronic pulsator (70) to be connected to the movable part, possibly via an adaptor, and enabling the pulsator to communicate with the vacuum pipe (16) when the movable part (14) is inserted into the fixed part (12). Means applicable to the connector (75) are also provided to close communication with the vacuum and means to electrically connect the possible electronic pulsator (70) to an electrical energy source and, if required, to a control unit for the milking operations.