This wiring diagram is for trailer 12N plugs & sockets (normal) , 12S plugs & socket (suppplementary) & 13 pin. All caravans manufactured mid 2009 onwards will have 13pin electrics as standard. The trailer industry will move towards fitting 13 pin plugs and by 2012 we expect this to be industry standard. There are adapters on the market to help with transition ie. the adapters can change 13pin on vehcile to accept 7pin on trailer & vice versa.