3G GSM Door Intercom, incorporates a professional industrial grade 3G engine that receives calls at its SIM number, as any ordinary 3G phone. The system operates in the GSM module Quad-band and 3G 800/850/900/1900/2100Mhz, this Intercom works with both 2G and 3G Simcards. When a visitor arrives at your property they will press the call button on the intercom which will then connect to a phone number (up to 3 numbers can be added which will be rung in sequence) of your choosing, once you answer the phone and speak to them you can then open the gate from your phone and let them in remotely from wherever you are in the world.