Anyway, the connectors I am thinking of were part of as series. They were circular, most of them were chassis mouting plugs and cable sockets. The plug was recessed into the panel, and the socket part fitted into it. There were 1.5A and 5A versions with 2, 3, or 6 pins. Polaraision was acheaived by a groove down the side of the socket part and a corresponding ridge in the recessed plug. In many cases the wire terminals on the socket part were covered by a simple screw-on cap which means they're not not approved for use above 50V (since you can unscrew said cap and get access to live parts without the use of a tool). There were later mocels of some of the sockets with the cover held on by screws, AFAIK those are still OK for mains use. If you like I can tey to find the part numbers for them. -tony