Home-made security system lets you know when someone crosses your perimeter

Whether it’s the end of the world or just a camping trip, it’s always nice to know when an uninvited guest is crossing your perimeter. With a little knowledge and a single trip to the hardware store, you can create a fantastic perimeter alarm that won’t break your wallet. The system is a simple closed/open circuit that can be adjusted to set off anything from fireworks to an audible alarm. If you’ve got some radio experience you could easily modify this setup for a silent alarm that would trigger a signal at base camp without alerting the intruder.