Inexpensive perimeter alarm | ModernSurvivalOnline.com: "Security after TEOTWAWKI (The End of the World as We Know It) will be important. Depending upon your location – methods used to be aware of 'trespassers' will vary. For those on a budget – I have discovered a very inexpensive method to provide a decent alert when a passerby trips the alarm.
The main component is a window/door alarm that can be purchased at your local Dollar Tree for $1.00 each. These alarms are very loud (90 decibels). They contain a simple on-off switch and work via a corresponding piece that when moved away from the main unit – activates the alarm. Below are the step-by-step instructions on how I made one..."