A controller for a gradient sequential compression system is provided for inflating a plurality of inflatable chambers of one or more compression sleeves according to several different modes of operation. A mode of operation may define the number and selection of chambers to be inflated, the pressurization levels, the pressurization time, or the sequence of chamber inflation. To enable the controller to automatically perform a designated mode of operation based on the type of compression sleeve connected, a new and improved connecting device is provided. An indicator on an interface connector associates a predetermined mode of operation with the interface connector. A sensor associated with a complementary connector identifies the mode of operation associated with the interface connector. It is contemplated that the universal connecting device can be used for any type of system, not just controllers for a gradient sequential compression system.