scope:

This specification standardizes the interface and ratings of two versions of a medium size r.f. connector for use with flexible and semi-rigid cables. The connectors are recommended to be utilized in medium power and low reflection applications up to 11 GHz. The dielectric filled interface is especially beneficial in applications involving severe environmental exposure.

Both versions of this connector type are screw coupled versions of the Type C connector covered by I E C Publication 169-7: Radio-frequency Connectors, Part 7: R.F. Coaxial Connectors with Inner Diameter of Outer Conductor 9.5 mm (0.374 in) with Bayonet Lock-Characteristic Impedance 50 ohms (type C). In this standard, they are considered as two different types and are distinguished by the designations 169-21A respectively 169-21B. Type 169-21A (SC-A) is the older version connector which is still preferred in Europe. Type 169-21B (SC-B) is the newer American design. Both connector types originated in the United States of America.