This unit is a water resistant switching type voltage converter intended for use on vehicles with a 24V electrical system to power an independently isolated 12V supply of either polarity. The unit includes the addition of an independently isolated low power converter which may be used as a continuous supply for memory maintenance The unit can deliver 5A continuous and 6A intermittent output load current and has output overload and over temperature protection with a fully automatic reset. The unit has an output capacity of 5A subject to temperature as well as over-current and thermal overload protection. The unit provides total galvanic isolation of the 12V output from the 24V input. The unit is assembled in an aluminium extruded case and encapsulated in silicone rubber; this allows reliable operation in harsh vehicle environments and areas of high ambient temperatures. This unit is available with suffix P to meet Institute of Petroleum DOC – 1.92.1 for use on hazardous vehicles.