"M" is magnetic ballast, and thus no lamp controls. "S" is solid state ballast, and has lamp controls, and less flicker on video. The "S" also introduced position feedback in the fixture, but otherwise they are the same. The "M" was done by HES to get the fixture shipping while they were having problems with the solid state lamp ballasts. Oh, and the "S" will run the full range of voltages, whereas the "M" will only do 208/240 50/60HZ, and has be be manually jumpered for the one you want.
"M" is magnetic ballast, and thus no lamp controls. "S" is solid state ballast, and has lamp controls, and less flicker on video. The "S" also introduced position feedback in the fixture, but otherwise they are the same. The "M" was done by HES to get the fixture shipping while they were having problems with the solid state lamp ballasts. Oh, and the "S" will run the full range of voltages, whereas the "M" will only do 208/240 50/60HZ, and has be be manually jumpered for the one you want.
