Standards useful to both manufacturers and modellers are maintained by MOROP in Europe and the NMRA in North America. These standards are generally the same for such elements as track gauge, scale ratio, couplings, and electrical power and differ for clearances and other factors that are specific to the prototype being modelled. The wheel and track standards are however slightly incompatible and most vendors follow neither standard in part because of this.
N scale locomotives are powered by DC motors which accept a maximum of 12 V DC. In traditional DC control, the speed of the train is determined by the amount of voltage supplied to the rails. The direction of the train is determined by the polarity of the power to the rails. Since the end of the 20th century, an increasing number of enthusiasts have started using digital train control systems to determine the speed and direction of their trains. This has in part been made possible by surface mount technology and new motors that draw very little current (typically 0.2amps). The most popular digital control systems used in N scale model railways are NMRA-DCC and Selectrix.
The initial agreed-to standard coupling was known as a 'Rapido' coupler from the manufacturer (Arnold); this coupler had been produced under a license from TT-manufacturer Rokal. Most companies developed their own variants of this coupler to avoid Arnold patents on the spring system. Graham Farish initially adopted a plastic flexible U rather than a spring, Peco used a compatible weighted coupler system (Elsie) and Fleischmann cunningly sidestepped the problem by using a sprung plate. All however were compatible.
The Rapido coupler system works well but is difficult to use for automatic uncoupling and also relatively large. In the U.S., Canada and Australia it has been largely superseded by a more realistic looking magnetic knuckle coupler, originally made by Micro-Trains. The MT couplers (as they are known) are more delicate and closer to scale North American appearance than Rapido couplers. Also, they can be opened by a magnet placed under the track. Other manufacturers, such as Atlas and Kato, are now making couplers that mate with Micro Trains couplers.
European modellers have the option to convert the couplings on their rolling stock to the Fleischmann Profi-Coupler system for more reliable operation should they wish to do so, but most N scale rolling stock continues to be manufactured with Rapido couplers - a design which is fairly robust and easy to mold. Modern N scale stock uses a standard NEM socket for couplers which allows different coupling designs to be used by simply pulling out the old coupler and fitting a new one of a different design. In the United Kingdom vendors are increasingly shipping both NEM sockets for couplers and buckeye (knuckle) couplers.