The TE Connectivity 501933-3 is a duplex multimode fiber optic adapter that converts an FSD receptacle to a pair of ST receptacles. FSD is a duplex, keyed rectangular interface used in some premises and datacom panels; ST is the bayonet-style round connector common in multimode patch cords. This adapter lets you terminate an FSD bulkhead and patch into standard ST-terminated cables without re-terminating the panel side. The housing is beige plastic, panel-mounted with a flange that secures it to a cutout in the patch panel or equipment chassis. The M-keying prevents inserting the adapter into a bulkhead keyed for a different interface. A dust cap is included on each port to keep the ferrule end-faces clean when the adapter is not mated.
Compatibility and Cross-Shop Notes
This adapter is purpose-built for the FSD-to-ST conversion — it is not a generic LC-to-ST or SC-to-ST coupler. The FSD end is a duplex, keyed rectangular interface that does not accept standard LC or SC connectors. If your panel is terminated with LC connectors, you need an LC-to-ST adapter, not this part. No pin-compatible alternative is listed in the same series; the 501933 base number covers several keying and color variants, but the FSD-to-ST conversion is specific to this order code.