Almost all "N" gauge rolling stock is fitted with the "Rapido" coupler. This is what most Dapol, Graham Farish and Peco models will have as standard. (Some multiple-unit models that are intended to stay as a rake have different couplers as standard; they aren't designed to inter-mate with anything else).
There are actually two variants of the Rapido-type coupler. The version supplied by Dapol and Graham Farish has a small spring to return the coupler to the centre. The "ELC" version supplied by Peco does not have a spring, and it ifs free to lift vertically. Both of these couplers mate with each other.
To uncouple both of these types, a movable "ramp" can be installed into the track. This needs to lift to uncouple, and lower down to allow trainst to pass normally. For example the Peco SL-330 module does this; it can be operated manually or by using a point motor. Then in the raised position, the arm on the bottom of the coupler is pushed up, and the couplers lift and and are allowed to separate.
There is an alternative magnetic method to uncouple the Peco ELC style couplers. This has a small strip of iron mounted to hang down below the coupling. When an electromagnet under the track is activated, this iron strip causes the coupling to lift up.
My experience with these couplers has been as follows.
- When coupled, the "return spring" type will stay coupled. A train can reliably be driven round the railway and it will never break apart.
- It is quite hard to couple them together if the train is on a curve.
- The Peco ELC variant have been prone to uncoupling themselves on my railway.
Either uncoupling method does not permit subsequent shunting while preventing a "recoupling" from occurring. That means an uncoupler will be needed in every spot where a coupling needs to be split. At the end of a terminus station platform, that isn't a problem; in a shunting goods yard it may be more of one.