The section on alarms features the explosive gas alarm, which sounds an alarm before sufficient gas has built up in a home to cause a damaging explosion; the peep alarm, which is designed to sound an alarm to indicate that a dark enclosure, such as a safe or an unoccupied dwelling, has been accessed and exposed to light; an anti-theft device that can be attached to particular appliances to emit a continuing alarm when the appliance is moved; a home alarm that sounds when an intruder forces his way into the home; and a loop alarm, which sounds an alarm when an item is moved from its designated location without permission. A section on locks features the keycode lock, the infrared doorlock, and the infrared codelock. A section on miscellaneous security devices features the infrared proximity detector, the electronic "watchdog," and the forged bank note detector. For each device featured in the book, construction and installation instructions are provided, accompanied by circuit designs, PCB layouts, and a list of the necessary components. This book serves as a practical guide for selecting, constructing, and installing the featured security devices by anyone with a basic knowledge of electronic circuit construction.