ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Little hole on British plugs

On the Russian 220V thread, Paul said ...

I only vaguely recall this feature Paul. Do you have any pictures of that you could post? Was it new to the older 13A type? - I don't recall seeing anything like described on the older 15A standard.

I can remember some Australian plugs had this too. I'll have a scout through my boxes of fitting s& see what I come up with also.

32VAC,
Welcome to ECN mate!.
Great to have another Member from down this way on the BB.

Thanks, Trumpy. Cold where you are? Its about 17 degrees here. Another thing that I have noticed on older Clipsal plugs (end of bakelite/beginning of PVC plugtops such as the old part numbers 401s, 417s 423s & early 439s)was the way the pins were made with a 'notch' in the end. was this done to save material or just a manufacturing or design 'feature'?

Welcome 32VAC.

Here's the feature on a typical 1960's vintage BS1363 MK plug:




Ian,
Yes, this was found on BS546 as well. Here's a 15A BS546 plug of similar vintage:



And an older 5-amp BS546 plug:

You beat me to it Paul.. Is there anything you haven't got in your collection??

Digicam software is playing up again ..it will teach me not to instal any 'patch' from Microsoft everagain

I always assumed that this feature was to provide a signal earth/ground for a radio, I have used it more recently in the UK, (with an olde plugge LOL) to obtain an ESD earth for working on PC parts.. yes, I know, could be nasty if the earth isn't connected on that socket, I used to carry a 13A socket tester too. I don't think it was to save material though, some method of connecting to the earthing system would be the obvious reason, and old radios dating from this period often used 2 wire cords with a requirement for a signal ground... I guess they allowed you to connect to it for this purpose without the earth wire coming near the live wires in the plug?

Yes, that's the sort of use I always imagined for it. Most old valve/tube radios of the 1940s/50s had aerial and earth terminals on the back, and being AC/DC live-chassis models had a 2-wire cord.

The earth terminal was generally wired to the chassis via a suitable capacitor to provide a low-impedance path for RF but block 50Hz mains.

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