The is a legacy serial-to-Ethernet device server. Official service manuals (with schematics, component-level repair info) are generally not publicly available — Digi typically provided user guides and configuration manuals, not repair-level documentation.
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A full manual would include these chapters. I’ve reconstructed the expected sections based on similar Digi devices (ConnectPort TS, WR series): The is a legacy serial-to-Ethernet device server