How-to automate (Lego) trains (UNDER CONSTRUCTION)

This how-to is written based on the use of the old 9V Lego train system. The techniques described here can also be used with 12V Lego trains. RC/PF-trains are subject to a different approach, see also the last chapter of this how-to. This how-to has the following chapters:
1. Isolating track segments
2. Powering isolated track segments