1. GSM Quad-band, can work in the worldwide GSM Networks; 2. No call charges. theGSM Gate Opener/Relay Switchrejects the call from authorized number then carries out the turn ON/OFF action on the first 'ring'; 3. Multiple applications. (gates, bollards, barriers, garage doors, shutters and access doors or machines); 4. Secure - Using caller ID for identification, unknown callers are ignored; 5. Can be operated from anywhere, no distance limit;