i am replacing a two gang switch whitch operates wall lights n ceiling light in my lounge,i have two cables coming out of the wall one has 2 wires(red n black) the other 3 wires(red black n earth which is sheathed in black).On the back of the switch the terminals are common common at the top and 1 way 2way 1way 2way at the bottom.also on the old switch there was a small piece of wire connecting something but as my wife took the old one off i have no idea which wire goes where please help