Block Diagram The security system comprises of an Arduino Uno microcontroller and a standard SIM900A ... (3,4); // RX and TX pins to communicate with GSM module #define msg_key 7 #define call_key 8 ...

The Spark Electron was released a few days ago, giving anyone with the Arduino IDE the ability to send data out over a GSM network. Of course, the Electron is just a GSM module tied to a ...