Just checked behind my BT master scoket, 3 wires?

Hi,
Ive just checked behind my Master BT socket and I have 3 wires connected, and 1 lose wire, not connected.
The connecter at the back of the socket, has 4 slots for wire, and there are 3 wires connected, the first slot at the top of the socket has a wire, the next one down does not, then the next two have wires in.
I do have extension wiring.
Does this sound ok?
Thanks

If it only has 1 cable and set of connections and you have more sockets then its probably not the master socket. Can you identify it from http://www.telephonesuk.co.uk/wiring_info.htm? Does it have any components e.g. a yellow capacitor in it.
Normal connections are numbered and you need to connect to 2+5. 3 is the ring wire and is often connected, but is often better with ADSL to disconnect it.

Hi,
Thanks for reply.

I think it must be the master socket, as the BT cable that comes from the outside runs up the outside wall, the other side of the socket. But saying that, there is no yellow capacitor, so i'm not sure, I will check the other BT sockets, but they are all upstairs.
Thanks again for reply.

UPDATE,

Ok I just checked 1 of my upstairs sockets, and this looks more like the pictures from the web site you gave me to look at,there is still no capacitor and no test socket behind the face plate, but this socket does have lots of cables and it does look like a LJU2 socket.