From the introduction: Yags High Tech covers the equipment available during the period from the early 20th century (Technology Level 6) through to the early 21st century (TL 8). Though it is barely more than 100 years, there is a huge change in the type of items available. However, they are all close enough to the present to be considered Modern, and for most people to have a vague understanding of what these periods in history were like.