This standard concerns patterns for r.f. coaxial connectors which may preferably be used with r.f. cables 96 IEC 50-1 or 50-2 of IEC Publication 96-2, Radio-frequency Cables, Part 2: Relevant Cable Specifications.
These connector patterns are for low power. They have a screw type coupling mechanism and are commonly known as type "SMC".
BS QC 221400:1997 history
1997BS QC 221400:1997 Radio-frequency connectors. RF coaxial connectors with inner diameter of outer conductor 3 mm (0,12 in) with screw coupling. Characteristic impedance 50 ohms (Type SMC)