GSM-based calling system is basically a project for the coal mine workers who put their lives at risk when they enter the mines for work. Mines are deep down beneath the Earth where there is no signal for making even an emergency call and hence once the mine worker enters the mine, he gets totally disconnected from the outside world. To avoid this, a GSM-based coal mining system is being developed and with this system, coal mine workers can easily make a short range call to the workers or helpers outside the mine in case of emergency or can at least signal them when there is a danger. This project will consist of a GSM mobile which will make calls and some other metal detectors for detecting hazards in the air which will cause the LEDs to glow in case of any emergency.