The SPS.500 secure power supply provides cyber-security authentication and onboard intelligence for diagnostics. Encased in a NEMA 4X sealed-aluminum enclosure, users of any PLC, SCADA RTU, PAC or DCS can retrofit to the power supply inside or outside enclosures anywhere in a plant and in harsh environments. The power supply is suitable for the Industrial Internet of Things (IIoT). Features include Ethernet and OPC/UA communications, enabling local or remote monitoring of power supply health; a cyber-secure microprocessor and onboard memory for diagnostics and software-defined functionality; a built-in redundancy module; and two built-in, software-configurable Form C contact relays for operating and diagnostic status.