oh @#$@ a nieghbour told me the false post info i appoligise for any inconvience submitted i grow outdoor and am know aware of the facts.. PLEASE FORGIVE the babble !! Combination HPS/MH lamps combine a metal halide bulb and a high pressure sodium bulb in the same reflector, either with a single integrated ballast assembly or two separate ballast assemblies. The combination of blue metal halide light and red high pressure sodium light creates an ideal spectral blend and extremely high outputs.
Switchable, convertible & two-way lamps
Switchable, Two-Way and convertible lamps are used to burn either a metal halide bulb or an equivalent wattage high pressure sodium bulb in the same fixture, but not at the same time. These fixtures are used for propagating and vegetatively growing plants under the metal halide, then switching to a high pressure sodium bulb for the fruiting or flowering stage of plant growth. To change between the lamps, only the bulb needs changing and a switch needs to be set to the appropriate setting.