Spent the last few days installing CAT5 wiring, so took the opportunity while the floorboards were up to add lighting etc switches beside the computer which involved using intermediates. Used the MK grid system as I needed more than one on one plate. Of course, the old other switches didn't match anymore, so I replaced these too.
And here's the point.
The single MK logic switches (bought from a shed) came with instructions. Idly glancing as you do, it said to wire an intermediate 1&2 to L1 L2 on the two way switches. But 1 & 2 as marked on the grid switch were the same pole - ie with the switch 'off' RH1 (top) went to RH2 (bottom) and LH1 (top) went to LH 2 (bottom) - in other words the layout was as expected for any intermediate I've ever seen. Wire it as they said (admittedly not for a grid switch) and it wouldn't work.
Just to clarify, the grid switch was marked thus:-
__________ | | | 1 1 | | | | | | | | | | 2 2 | |_________|
I suppose it would be logical to make the terminals on an intermediate the same as on a two way, but if they are changing things, would be an idea to do it all at once...