Train Couplers is a mechanism used to connect rolling stock in a train. The design of the coupler is standard. This is almost as important as the track gauge. Since flexibility and convenience are maximized if all rolling stock can be coupled together.
HORN HOOK COUPLERS
These are the ones that probably came with your original equipment. They don’t look anything like the prototype train couplers. They rely on side pressure to hold them together. This is a major problem when backing up because the side pressure often causes derailment. Rapido couplers are used with most original N scale equipment with similar disadvantages.
These are more prototypical, they look better, and they work well with the magnetic uncouplers. Also, you don’t have as many derailments when the drains are backing up. Some people like to put Z scale knuckle couplers on the fronts of N scale locos (or N scale couplers on HO locos). The smaller train couplers look more realistic on the larger models. The same idea can apply to the backs of cabooses.
Most people don’t like horn hook couplers. They can’t wait to replace them with (or “convert” them to) knuckle couplers. They are more realistic and work well with the magnetic uncouplers. This takes a certain amount of time and effort to convert all of your equipment to knuckle couplers. This is why people usually do this in a stepwise fashion, converting locomotives and cars one at a time. Sometimes mixing them in consists till they are all converted. You can have several conversion cars on which you have a horn hook or Rapido (in N scale) coupler on one end. A knuckle coupler on the other so that you can connect both types within your consist.
Kadee was the first manufacturer to develop this system. In which a special magnet (not just any magnet) is positioned under the track. At a strategic location like in front of a branch line, spur, or ladder. Such that when a train is backed up and stopped with the knuckle coupler over the magnet. The “glad-hands” of the coupler come apart when slack is allowed.
These are also available from Kadee for all scales, primarily electromagnets activated by applying current to a wire wrapped around a cylinder many times, which creates a magnetic field. These have to be mounted in a space cut out from under the track, which is really no problem if you’ve used foam for your sub roadbed.