Recently replastered a ceiling and disconnected the pull cord switch which was pretty old and knackered anyway. Unfortunately, I forgot to remember which wires went where. I have three wires coming out of the ceiling - all of them red (but presuambly they can't all be live?) - and three slots in in the socket for the wires to go into - L1, L2, and COM. Anyone got any idea how I can work out which ones go where?

 Goes without saying I'll be turning off the power at the mains first.