Tetser for the 12S Socket with a low load test to prove the function of your Grey 12S Socket. The unit has 5 LED's for Pin 1.Reverse Lights, Pin 2 BAttery Charger (or Spare Post 1997), Pin 4 Permanent Live, Pin 6 Fridge, Pin 7 Fridge Earth through Pin 7 (Post 1999). Please read reviews and see combined offer with a 12N Tetser for a discount offer.