Single electrics (also called 12N electrics) provide you with a single 7 pin socket at the rear of your vehicle this is used to provide the normal tail/side lights, indicator, brake and fog lights. Single electrics allows you to tow any trailer or caravan as your entire road legal lighting is provided.

Twin electrics (the second socket is a 12S socket) provides you with two 7 pin sockets at the rear of your vehicle. This allows you to tow any trailer or caravan as your entire road legal lighting (including reversing lights) are provided.

The grey or white 12S socket provides power to the caravan battery, fridge, interior light and reversing lights and is optional when towing a caravan.

Many people who only tow a caravan for a couple of hours and will then be pitching up at a caravan site with mains electricity opt to do without the 12S socket and just fit single electrics to their vehicle.

13 pin electrics have been the norm in Germany and most of mainland Europe for many years. The 13 pin system replaces the twin electrical system currently used in most UK caravans.

The 13 pin system became standard in the UK on 2009 model caravans, these first started appearing for sale around September 2008.

Even if towing a caravan with twin 12N and 12S twin plugs some times you may wish to fit a 13 pin socket. This is because some detachable towbars have a swivel plate for the electrics to be hidden when not in use. The swivel pate is usually designed for only one socket and may not work properly is a "piggy back" plate is used to fit 12N and 12S twin electrics.

Some vehicles (such as many BMW's and Audi's) allow for the purchase of a bumper cover from a main dealer which covers a bumper cut on the vehicle. These bumper covers are designed by German car makers and as such are designed to fit one 13 pin socket.