A centralised control mechanism, with integrated safeties, for a device for the sealed transfer between two closed spaces, this device comprising a first flange and second flange (18, 20) which can be securely attached to one another by a first bayonet connection, and a first door and a second door (22, 24) normally plugging openings respectively delimited by the first flange and the second flange, and which can be securely attached to one another by a second bayonet connection, this control mechanism comprising: - a movable control member, installed on the first flange such that it is able move between a closed position and an open position, passing through an intermediate locking position, - a system of ramps interposed between the control member and the first door, in order to separate the latter from the first flange when the control member moves from its closed position to its open position, - a first lock normally blocking the control member in its closed position, and which is automatically unlocked by the presence of the second door against the first door, - a second lock normally blocking the control member in its closed position, and which is automatically unlocked when the second flange is securely attached to the first flange by the first bayonet connection, - a third lock which is normally unlocked when the control member is in its closed position, and which automatically blocks the first bayonet connection in a condition of secure attachment of the first and second flanges (18, 20) when the control member is between its closed and open positions, or in one of these positions, - a fourth lock, which is normally unlocked when the control member is in its closed position, and which automatically acts to prevent this member returning to its closed position, after a separation of the first door controlled by the system of ramps, when the control member is between its closed and open positions, or in one of these positions, characterised in that the centralised control mechanism also comprises a protective lock which is normally unlocked in the closed position and in the open position of the control member, and which can block the control member when the second flange is not at least completely locked on the first flange between the time when the second lock is in the unlocked position, and before the time when the third lock blocks the first bayonet connection in a condition of secure attachment of the first and second flanges, so as to prevent the first door from opening. - a movable control member, installed on the first flange such that it is able move between a closed position and an open position, passing through an intermediate locking position, - a system of ramps interposed between the control member and the first door, in order to separate the latter from the first flange when the control member moves from its closed position to its open position, - a first lock normally blocking the control member in its closed position, and which is automatically unlocked by the presence of the second door against the first door, - a second lock normally blocking the control member in its closed position, and which is automatically unlocked when the second flange is securely attached to the first flange by the first bayonet connection, - a third lock which is normally unlocked when the control member is in its closed position, and which automatically blocks the first bayonet connection in a condition of secure attachment of the first and second flanges (18, 20) when the control member is between its closed and open positions, or in one of these positions, - a fourth lock, which is normally unlocked when the control member is in its closed position, and which automatically acts to prevent this member returning to its closed position, after a separation of the first door controlled by the system of ramps, when the control member is between its closed and open positions, or in one of these positions,