The DC-DC converters provide clean 24 VDC power suitable for instrumentation and control networks and process equipment. For operation under the most harsh and demanding conditions, the units are fully sealed and enclosed to protect against moisture, shock, and vibration. Power from a battery or other source as 12 or 24 VDC nominal is converted to a 24 VDC output. The units are designed with extremely rugged surge and transient suppression in addition to sustained over/under voltage protection.