| As the title suggests, this book is a collection of circuits. The circuits are all well-designed and functional although they do seem chosen at random. The technology is old (very old, I have seen versions of these from the 1940s) but it does work - mostly. This book is probably pitched at the self-taught private detective who is not too fussy about the local eavesdropping laws. This is definitely not what your country's internal securty force is using! Circuit schematics are provided along with a theoretical description and some practical tips. The book presents the circuits in six sections:
In the section on surveillance, the circuits include a simple subcarrier generator for an FM bug, a hookswitch bypass for older style (non-electronic) phones and some very old (but useful) techniques for hardwire and telephone taps. Some voice activation circuits and high gain amplifiers are also mentioned.
The section on remote control offers some very simple but useful techniques turning common consumer electronics into remote controlled devices.
The section of infra-red flashers provides variations on the same circuit - a blinking IRED which can be tracked at night with an infrared scope or a video camera.
The section on counter surveillance provides some well-known techniques for tracing radio bugs, phone taps and hardwire taps.
The section on receiver enhancements provides some simple techniques to receive subcarrier or carrier current transmissions on an HF communications receiver.
There is a section mostly dealing with circuits that record unauthorised entries or phone use. Most circuits are old, but well-proven technology. A few would be dangerous enough in North America with their 110 volt mains, but they are guaranteed lethal in the remainder of the world where 220, 230 or 240 volts is more common, or where 415 volt three-phase systems are in use. The Parts Source section is only of use to readers in North America | 
