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Old 17th Oct 2012, 11:39 pm   #36
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Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,313
Arrow Re: 13 amp plug question

I've always believed that is was for connecting an earth wire, such as providing an 'earth' connection for the 'earth' socket on a wireless. Since many wireless set owners would have difficulty in providing the then conventional earth plate in the garden (e.g. flat dwellers), this would provide the necessary 'earth'. (Now we all know that such an earth will be a poor radio earth, but that would not have been well-recognised all those years ago by the average wireless-user: he just wanted an 'earth' for his wireless).

Below is a photo. of an old 13-amp plug and you can see that inside it there is a small step in the plastic to assist and support such an earth wire. By looking at the internal photo, it is also very clear that the hole is not for the purposes of inspecting the internal earth connection, since the 'viewing hole' is well offset from the earth pin screw terminal.

What is not seen in those photos is the writing on the 3-pin side of the plug. It reads:
13A 250V.
NO. 689

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Last edited by Skywave; 17th Oct 2012 at 11:44 pm. Reason: General tidy-up to improve presentation.
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