3Com DSA-0121D-03 Switching Power Supply

The 3Com DSA-0121D-03 Switching Power Supply is an external AC-to-DC adapter designed to power select 3Com networking devices that require a 3.3‑volt, 4‑amp DC supply. It accepts universal input from 100 to 240 VAC at 50/60 Hz, enabling operation in most regions with the appropriate plug configuration; reseller listings show an AU plug variant for Australia and New Zealand. The model designation DSA-0121D-03 specifies this 3.3 V, 4 A output unit, which is commonly used with legacy 3Com equipment whose power rail is supplied by this external brick. By delivering a stable +3.3 VDC at up to 4 A, it accommodates devices with modest startup currents and steady operating load within the rated specification. This power supply is referenced in retailer listings and regulatory documentation as the compatible AC adapter for the corresponding 3Com model family, providing a straightforward replacement when an original brick is unavailable. Its compact, external form factor keeps the device free of a built‑in PSU, aligning with how older 3Com components were designed to be powered.