It literally says 'the control for the isolators' — but usually, the control (lever, etc.) is located on the actual isolator itself, so there's no reason to mention it separately; unless, of course, for some reason, in your specific context, these isolators are remote-controlled, whic although certainly possible, is, I feel, perhaps slightly less likely in your context — though it does rather depend what sort of trade show this is, what sort of scale it is one, and the sort of power consumption to be expected. Obviously a trade show for industrial machinery might have different power arrangements than a flower show!

It just means that the location of the isolators must be clearly indicated, so they can be found easily in an emergency.

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Note added at 17 mins (2011-01-24 14:05:09 GMT)
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In the UK at least (though I think the concept is fairly universal), users of high-voltage outdoor neon signs must have a very readily accessible isolating switch so they can be cut off quickly in the event of an emergency; traditionally, in the UK, this is red and high up, with an eye on the lever so it can be operated by a hooked pole from ground level (while being well out of reach of tampering). This is colloquially known as the 'fire brigade isolator'.

However, even if your situation is slightly different, I still believe that 'isolator' is a good translation solution.

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Note added at 45 mins (2011-01-24 14:32:37 GMT)
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I found this Google hit while looking for something else; I feel sure the translation is likely to be shaky (Far Eastern website!), but it does in fact illustrate exactly the term I was referring to:

Cutout switch 주문 정보로부터 Cutout switch 구매자, 수입상 Cutout ...

브라우저 Cutout switch 구매 정보, Cutout switch 구매 제공로부터 Cutout switch 수입상, ... We are looking for Fireman Isolator Switch for neon sign. ...

korean.embiz.net/hb/Cutout-switch.aspx