This Ring Automotive supplementary towing socket kit is typical of those you can buy in an accessory shop.
This kit includes: A 12S socket Socket sealing grommet C Mounting bracket .7-core wiring Electrical connectors F Socket bolts The combination relay (G) for charging an auxiliary battery can be bought separately.
A caravan or trailer must, by law, be fitted with certain warning lights.
These are wired up to a standard plug socket called a 12N socket which provides
a 12 volt supply to power the indicators, stop lights, tail-lights,
number-plate illumination and fog lights.
While the 12N socket is adequate for operating the obligatory lights, you
may want to run power from the car for other, non-essential accessories such as
reversing lights. A caravan without its own battery may also need extra power
for interior lights, a refrigerator or a water pump. For this you need an extra
towing socket.
Supplement
The extra socket that is fitted to the car to provide the power needed for
these additional items is known as a supplementary or 12S socket. It is fitted
near to the original socket and, like the original one, has a seven pin
connection inside. You can identify the supplementary sockets by their grey or
white caps.
The standard sockets have black caps.
If you are fitting a tow bar, and you intend towing a caravan, it is worth
while fitting both types of socket.
You can buy both ordinary 12N sockets and supplementary 12S ones in the form
of a complete kit from an accessory shop or towing specialist. The kit should
include all the items you need to fit the socket to the car such as mounting
brackets, wiring, weatherseals, indicator relay, dash-mounted warning light and
securing screws.