FXLuminaire® DX300SS 7.14" x 5.04" x 11.4" Stainless Steel DX Controller 300W. The DX controller is an easy-to-program, low-voltage lighting transformer for customers with intermediate on/off lighting control needs. It's the only digital facepack-controlled transformer with astronomical timing and event-based programming capabilities pre-installed, so there is no need for plug-in accessories such as timers and photocells.