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, but with additional metal contacts attached to the bottom of the housings.
1978 LEGO Sets
1978 was transformative: the modern minifigure arrived with articulated limbs and standardized proportions, becoming the heart of LEGO play. Three pillars launched in force—Town, Space, and Castle—bringing buses and services to city streets, astronauts and bases to the cosmos, and knights and keeps to medieval scenes.