Rufus Turner wrote a fabulous book on single-transistor projects. I reviewed the book for Amazon. See... http://www.amazon.com/125-One-Transistor-Projects-Rufus-Turner/dp/0830695370 You have to be careful with early transistor projects. Most of the transistors are germanium. After making circuit changes, you can build these circuits with modern, silicon parts. At minimum, the silicon transistors require changes to the bias circuits. (Sometimes, you'll need to make other changes, too.) For help with the changes, refer to my page at... http://www.hawestv.com/transistorize/germanium1.htm Equivalents to some early semiconductor types are unavailable today. (Or available only as used, or new-old stock parts). Such semiconductors include tunnel diodes, unijunction transistors and most early FETs. Redesigning circuits with these parts could be rather difficult. James T. Hawes