Souriau’s 851 series of circular connectors were originally developed to ensure reliable electrical connections in aircraft. Due to the lightweight compact size and general characteristics, the 851 series has been utilized in numerous applications. The 851 connectors feature a positive bayonet coupling mechanism which ensures reliable mechanical and electrical connection between mating halves. The plug features a helical locking ring that couples with the three dowel pegs on the receptacle ensuring rapid locking. Orientation and location is achieved with a system of five raised keys on the plugs which couple with corresponding slots on the receptacles. Connectors with different angular positioning of the insulator relative to the shell can be provided to prevent undesired accidental mating of adjacent connectors with the same contact arrangements.

The connector shells are manufactured from aluminum alloy with several finish options. The insulators are molded from elastomer and are bonded into the shells. Grommets are also made from elastomer and are supplied with appropriate accessories in the solder version. Copper alloy contacts have gold or tin over nickel plating. To facilitate cabling, solder and PC tail contacts size 20 with a gold plated active part and tin plated terminations are available. The 851 connectors conform to the following international standards: MIL-DTL-26482 series I, NFC 93422, HE 301B, VG 95328, GAM/T1 list.

Souriau’s 852 series is a lightweight version of MIL-C-26482 Series II connectors. Locking is achieved by a bayonet quick-release system. Plugs, receptacles, and accessories are manufactured from stainless steel or light aluminum alloy with black anodized (non-conductive) plating, nickel (conductive) plating, olive drab or yellow cadmium (conductive) plating. Gold plated crimp contacts are removable from the rear and retained by metallic clips. Mini-coax and thermocouple contacts may also be installed instead of standard contacts.

The hard insulator is a thermoplastic material. The insulators are fluid resistant as specified by MIL-C-26482 Series Il / HE302 / EN3646, including previous standards NFL54130 / NAS 1599 / LN 29504. Front and rear silicone elastomer parts provide an effective seal between connector and cable and also at connector interface. Hermetic versions are available for both the 851 and 852 series.