| 摘要 |
<p>A security system comprising a plurality of home-based units provided with ranging means, the plurality of home-based units being in communication with a communication center, and a plurality of mobile/portable units related or unrelated to the home-based units. Each mobile/portable unit is capable of communicating with one or more home-based units located in its proximity. The system may further comprise direction finding means and operate in a license-free band. The home-based units may be connected to, or integrated into, a home alarm unit, a computer or an electronic device. The ranging means of the home-based units may use spread spectrum techniques.</p> |
