Charrett Sheldon. Electronic Circuits and Secrets of An Old-Fashioned Spy

Illustrated edition. — Paladin Press, 1999. — 128 p. — ISBN13: 978-1581600278; ISBN10: 1581600275.Learn to build bugs or take advantage of those already in place; assemble a DFMF decoder or decode phone tones without one; construct a red box for free pay phone calls; crack answering machine passwords; defeat digital and spread-spectrum cordless phones with an FM phone tap; and much more! For academic study only.