Regulated, dual-polarity, and specialized voltage regulators [1].
Technicians restoring vintage audio gear, old radio receivers, or classic industrial machinery use this book to identify standard circuit topologies of the 1970s, 1980s, and 1990s. How to Make Vintage Schematics Work with Modern Components
: LED flashers, Morse code practice keys, and simple radio transmitters. Practical Electronics for Inventors
Master Handbook of 1001 Practical Electronic Circuits - Amazon.com