“Some people collect stamps, coins or baseball cards, I collect electronic circuit schematics. I own several book shelves and file cabinets full of electronic circuit books, IC application manuals and circuit encyclopedias. I often use my collection for reference.”
David A. Johnson, – P.E. consulting electronics engineer.
(This resource by dave is very important for Electronic Enthusiasts, Engineers and R&D Engineers. I say this as an R&D Professional with more than 20 years off the ground)
Capacitance Proimity Switch Technology -The Design Corner, Imagineering E-Zine
“These switch circuits used a sensitive high impedance circuit to detect the small AC power line signals, picked up by the human body from nearby appliances.”
These are the type of technologies that lead to the Touch Screens on Tablets and Phones.