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Old 2nd Oct 2012, 11:46 pm   #5
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
Default Re: 13 amp plug question

The purpose of the hole in old plugs has puzzled me, too.

The GEC catalogue for 1911-12 has this note on the pages for its "Factory" earthed plugs:

Quote:
The S679, S700 & S701 are provided with earthing connections on both socket and plug, the terminals for attaching the earth wire being fixed in a position on the outside where they can be seen, as called for in Home Office Regulations , Form 928, issued February 1910, Regulation 13, pages 33 and 34.
No earthed connectors for domestic use were listed at this date, but perhaps the requirement for the earth terminals of industrial connectors to be actally located on the outside to facilitate inspection was initially carried over in modified form to the early earthed domestic connectors. I used to have two almost identical 5A 3 pin surface mounted sockets to BS546 gauge. One, presumably the earlier one, had the earth terminal protruding beyond the lower rim of the case where it was clearly visible when installed, whereas the earth terminal of the other was located within the casing as per current practice. However, my experience is that, with old plugs, the hole adjacent the earth pin is much too small to allow the earth connection to be inspected properly.

Last edited by emeritus; 2nd Oct 2012 at 11:59 pm. Reason: typo correction
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