What is a priority switch?

[wreck-it-steve]

I have one of these left over from a bulk lot I bought:

http://www.ebay.co.uk/itm/Siemens-6...ls_Supplies_Electrical_ET&hash=item3cbea726d4

What is it and how would you use it?

 

[ricicle]

It will give priority to one circuit over another eg on an off-peak time when storage heaters are on there could be a demand for hot water so the supply is switched over to the water heating circuit to reduce overall demand on the supply.
It will just depend on how you configure it so it could switch between any two circuits really.