Trailer Socket Interconnector 13 Pole Plug To Connect With 7 Pole Car Socket, Designed to enable recovery of trailers and caravans fitted with a 12v supply without the need for fitting a rear lighting board. It enables full operation of the trailer / caravan rear light clusters, also allowing full connectivity to any multi-pin socket fitted to the recovery vehicle. The most commonly fitted sockets to HGV vehicles are 7 Pole Commercial HGV; 7 Pole passenger Vehicle; 13 Pole (Scheduled for introduction late 2008).