This GSM Modem can accept any GSM network operator SIM card and act just like a mobile phone with its own unique phone number. Advantage of using this modem will be that you can use its RS232 port to communicate and develop embedded applications. Applications like SMS Control, data transfer, remote control and logging can be developed easily. The modem can either be connected to PC serial port directly or to any microcontroller. It can be used to send and receive SMS or make/receive voice calls. It can also be used in GPRS mode to connect to internet and do many applications for data logging and control. In GPRS mode you can also connect to any remote FTP server and upload files for data logging. This GSM modem is a highly flexible plug and play quad band SIM300 GSM modem for direct and easy integration to RS232 applications. Supports features like Voice, SMS, Data/Fax, GPRS and integrated TCP/IP stack. The main aim of this project is to provide security to museums from thefts. Four I.R sensor pairs are interfaced to microcontroller and placed side by side. The microcontroller continuously monitors the status of these sensors. If any sensor gets activated, it will be detected by the controller and performs the predefined task of sending the SMS to particular mobile numbers which indicates that the theft occured. And a buzzer is also interfaced to the controller for audio indication, so whenever any of the sensors activates, the buzzer will also be activated through the micro controller. Here we use 8051 as a microcontroller with 5v DC Power supply. Serial (UART) protocol is primary concern here. The main heart of this project is GSM/GPRS modem and it work on GPRS AT commands.