Abstract
This paper presents about microcomputer, microcontroller and data transmission via computer network for application of housing estate security system. This system consists of three parts, the first part is a security system for each house using MCS-51 microcontroller as a central processing unit scanning 32 sensors and control 4 appliances and send alarm with siren and call house-owner or police station automatically, the second part is master/slave network that use microcomputer to display all alarms in graphic format and send control data of all system using serial communication RS-485 standard which can support up to 991 homes at transfer rate of 9600 bps. The third part of this project is Internet connection facility that enables users to examine status of sensors and turn Electrical Equipment ON/OFF via WEB browser.
