A GSM alarm system is a wireless home/industrial security product. The security alarm itself, as well as its motion sensors and door and window opening sensors, link up to a mobile network. Basically, your GSM home security alarm will communicate with the wider GSM network using a SIM card (Vodafone , Orange ,WE , etc ). If someone is trying to tamper with your home/factory security system, they can’t simply shut off your home alarm systems by cutting your home’s power supply, or damaging its telephone lines. Your GSM security alarm will still function just fine, as it will stay connected up to the GSM cellular network using battery.