This is a tridonic em 33a mini basic emergency module this is a 3 cell module used for 28w 2d lamps and has a 3 hour rated duration these modules are compatible with all electronic ballasts and can be used in combination with conventional magnetic control gear too the em mini range used 5 pole techonology with 4 pole lamp changeover and delayed power switching for the ballast tridonic article number 89899951