light switch replacement

[bertyb]

Im in the middle of replacing the light switches on my hallway and stairs, downstairs is a normal 2 way switch. upstairs at 1 end of the landing is another normal switch, but at the other end of the landing is a funny looking thing. it has 2 red wires in it and 2 black wires in it?? (2 L1 terminals and 2 L2 terminals)ive not seen a switch like this before and am a little concerned as to wether or not its a dodgily wired switch.
have you any info?

[ultimatehandyman]

Hi Bertyb

The switch that you are refering to is called a intermediate switch and is positioned between two- two way light switches on a three way lighting arrangement.

There is more info on how a three way system should be wired here-

http://www.ultimatehandyman.co.uk/three ... ghting.htm