DIY Security systems @ NYTimes… via /. If you want to build your own, check out our archives…

WHEN Ken Jongsma built his new house, he found that the builders had already installed a basic security system — sometimes called a prewire. A tinkerer and engineer, Mr. Jongsma, 50, decided to upgrade and monitor the system on his own.

“What most people do not understand is that a residential alarm prewire is a come-on by alarm companies to get you to sign up for their — usually expensive — monitoring,” he said.

Until recently, Mr. Jongsma’s attempt to install and maintain his own security system would have been impossible. Now, however, with a little knowledge, even nonengineers can add a security system to their homes for less than a standard prewired installation by a professional.

Most security systems consist of two parts: the hardware and the monitoring service. For decades, the hardware (window and door sensors and motion detectors, for example) was often installed by professionals, as it required some wiring and cabling.