For those who are into scale train layouts who have yet to try immersing in the hobby, they may need to know that it's the HO scale that is the most popular and well-known railway scale in the modern world both for the English and even the non-English communities. The HO scale's standard ratio dimensions is one real foot is equivalent to 3.5 millimeters.
The term HO comes with a distinct derivation as it doesn't stand for a specific word using the exact letters. "H" stands for half in HO as the "O" actually stands for zero but is pronounced that way since half of the zero or O scale is in fact an approximation of 1:87. The O scale derived its name from the preceding bigger scales as 1, 2 , and 3 and the colloquial term remains to be pronounced as "aitch - oh" to stand for aitch-zero even today. During the onset of the twentieth century the O gauge model for modern railways with the standard width of 32mm and a standard model scale of 1:45 became popular.
The real reason behind the HO scale train layout was development and introduction even before World War II is that there has been a clamor for people not having ultra large houses to have a train scale which is half the size of the O gauge. Aside from being suitable for smaller home setups, it would be more cost effective to manufacture and faster to make and because of these goals that the HO scale train layout or the HO gauge was conceived.
You might be taken aback that as early as 1922, a Nuremberg, Germany-based company called Bing has been topping the sales on tabletop railway scales for a couple of years now and they have been using the gauge of about 16.5mm for their quasi-ballasted raised tracks while this scale wasn't yet introduced as OO and HO. A company called Kibri designed and sold scale train accessories that will complement Bing's scales and measurements in response to the effort of the company. At the same time these scale trains run on with a clockwork drive but beginning 1924, most scale trains run on electricity.
The OO gauge or otherwise known as the half naught gauge became the talk of the town at the 1935 Leipzig Spring Fair and it was named the Trix Express. The rails became tin ballasts in what came about as the Marklin version and it is in contrast to the system of Bing wherein the tracks were attached and directly stamped on the ballast making the track and the ballast a single sheet of metal.
The HO scale trains was brought to life out of necessity because the Depression caused a lot of industries to downsize and people had to settle with what's available and more affordable, hence the HO smaller scale which is cheaper and easier to manufacture in general and hobbyists in the United States had fun making the HO scale better since it allows modelers to fit a lot more details and more scale miles into a small given area.