Z scale
Z scale is one of the smallest commercially available model railway scales (1:220), with a track gauge of . Introduced by Märklin in 1972, Z scale trains operate on 0–10 volts DC and offer the same operating characteristics as all other two-rail, direct-current, analog model railways. Locomotives can be fitted with digital decoders for independent control. Model trains, track, structures, and human/animal figures are readily available in European, North American, and Japanese styles from a variety of manufacturers. History. Z scale was introduced by the German model train manufacturer Märklin in 1972 at the Nuremberg Toy  Fair. It was the brainchild of Helmut Killian, Märklin's head design engineer at the time. The letter "Z" was chosen to designate the new scale, its place as the last character of the German and English alphabets signaling the thought that there would never be a smaller commercial model railway scale. While there have been attempts since then to bring even smaller scales to the market, they remain niche products without a wider followingthe largest market being T gauge (1:450, gauge), designed in Japan and manufactured in China. Originally running on 8 V DC, track voltage was increased to  10 V DC around the year 2000. Accessory power has always been 10 V AC. In 1978, a Märklin Z scale locomotive pulling six coaches made its entry into the "Guinness Book of World Records" by running nonstop for 1,219 hours, and travelling a distance of before the train stopped due to failure of the motor. Z scale, at its inception, was predominantly a European scale, but it has an increasing number of followers in other parts of the world. There are now also manufacturers in North America and Japan and China, among others. Z scale enthusiasts throughout Europe, North  America, and Japan participate regularly at most national and regional model railroad exhibitions and shows, where they have demonstrated the outstanding operation and layout design characteristics of the scale. While prices were initially higher for Z scale products (particularly locomotives) compared with those available in larger scales, as volume production, computer-aided design and manufacturing techniques, and the number of competing manufacturers increased, prices have come down to a point comparable to those of high-quality models in other scales. As early as 1988, Märklin announced their intention to offer digital train control systems in Z scale, and Märklin's  1988 Z scale product catalog listed three locomotives with a built-in digital decoder. However, the technology was not developed enough, and the manufacturer had to cancel these plans, mainly due to heat dissipation problems in locomotive decoders. Since then, these problems have been solved, Z scale has embraced advanced electronics (e.g., microprocessors originally developed for cell phones, surface-mount technology, etc.), and an increasing number of modellers have converted their locomotives to use third party digital model train control systems. The first attempts to use digital system in Z scale were based on NEM standard, Selectrix, which offered the  smallest decoders in the market, with thicknesses of less than 2 mm. German company Müt brought also the first digital control central unit designed specially for Z scale in the market in the early 2000s. Use of the popular National Model Railroad Association (NMRA) Digital Command Control (DCC) standard has expanded substantially in Z scale recently as locomotive decoders with sizes comparable to the sizes of smallest Selectrix decoders have become available. Z scale is now a mature modelling scale, with model locomotives, rolling stock, buildings, signalling and human and animal figures becoming available in increasing numbers from an expanding  variety of established and particularly smaller, fast-growing manufacturers. Z scale layouts have been winning local, regional, and national level competitions, such as best of show at the NMRA National Train Show (NTS) in July 2001, in St. Louis, MO. Advantages. The diminutive size of Z scale makes it possible to fit more scale space into the same physical layout as would be used by larger-scale models. Z scale can also be beneficial when there is a need to build very compact train layouts, such as novelty setups in briefcases, guitar cases, or jewellery boxes. Several transportation museums, for  instance, have used Z scale to present real world railway scenes. Z scale allows longer trains and broader, more realistic curves than is practical in larger scales. Drawbacks. Due to the small size of Z scale and, in particular, the low weight of the locomotives (a small Z scale engine can weigh as little as ), it can be challenging to ensure reliable operation. In particular, the track must be kept clean, as minuscule particles of dust, dirt, or corrosion can easily stop locomotives. Poorly-installed trackwork can be a source of consistent derailing of rolling stock (although this is true , to some extent, in any scale). All of this can create issues for modellers who are interested in prototypical operationsin particular, switching. The low weight of Z scale locomotives contributes to their difficulty pulling trains up grades. In practice, the grade is kept under 2% for reliable operation of trains up to seven, four-axle cars; shorter trains can operate on grades up to 4%. Pulling power of locomotives can be increased by use of traction tires, or by adding weight using high-density materialtungsten powder (used in metal golf club driver heads) and lead are popular choices. The smaller  market for Z scale results in a limited range of available products, including both rolling stock and accessories; some of the demand is therefore met by cottage industries. Manufacturers. There is a growing number of smaller manufacturers, both in Europe and in North America, of Z scale specialty items such as detail parts, electronics, track-building aids, structures, scratch-building supplies, and tools in addition to rolling stock.