Are you talking about the twist lock Marinco plug that connects to the RV? The other end plugs into 50 or 30 amps depending on the plug. 30 amps furnishes 110vac. The 50 amp furnishes 110vac to both sides. i.e. It could be 220vac although RVs don't use 220vac. They just use both sides of the transfomer and furnish 110vac to all circuits. Why tyey they don't furnish 220vac to the dryer is beyond my comprehension when it is available. May RV parks just furnish 110vac on both sides and being in phase isn't 220vac.