DS EN 4645-003:2009 Aerospace Series - Connectors, Optical, Circular, Single And Multipin, Coupled By Threaded Ring, Self-Locking 1,25 Mm Diameter Ferrule With Removable Alignment Sleeve Holder - Part 003: Square Flange Receptacle - Product Standard Defines the characteristics of mounted square flange receptacles in the family of circular connectors with triple start threaded coupling.