Trains

LEGO Trains is one of the longer running themes that dates back from 1966 and ran up until 2006. During its run there were multiple sets released running on various power platforms from 4.5volt, to 9 and 12 volt sets. Later in 2011 LEGO released additional train sets using RC and Power Functions controllers under different themes like City.

45V
The LEGO 4.5V train theme ran from 1966 until 1971 and contained 39 sets in all. The 4.5V trains used to be the voltage standard for the first electric LEGO components where the power came from a battery box with 3x 1.5V batteries.

4.5V/12V
In 1969 LEGO released the 12 volt train sets as part of the Blue Era which was named because of the rail color. In 1972 LEGO released the 4.5V and 12V train sets as part of the Blue Era which was named because of the rail color. These train sets used additional conductor rails mounted between the standard 4.5V rails and 12V motors contained in the same housings as the 4.5V motors

9V
The introduction of the 9V LEGO trains in 1991 marked the end of the 4 and 12 volt sets. These 9V trains were characterized by integral molded dark Grey rail and tie assemblies with metal conducting rails which was later integrated in the LEGO World City theme line.