This unit will cover all the functions on the 12N and 12S as well as the 13 Pin Euro Plug. With a connection to a battery it will apply power to all the functions during the test. The Lights are fused at 5 amp and the Charging / Live / Fridge are fused at 15 amp. All fuses are breakers which means no fuse to change. An LED will stay illuminated to indicate the fuse has not tripped. There is an AMP meter connected which will prove the draw of power for the Fridge and Battery Charging / Permanent Live. a toggle switch will turn switch power to test the lights (Old 12N functions) separately or the functions of the old 12S. this is to ensure that you can work on lights and not cause too many fault errors to caravans fitted with ATC. The unit is well constructed and feels solid. this unit has been made following a request from a caravan dealer to test their caravans, It has been made for the trade and will suit mobile caravan service engineers. Connection to a battery with a 16 amp rated Cigar Lighter fitting