This GSM remote works with a Telstra 4G sim card. The sim card can be prepaid with a long expiry. Data and voicemail services must be disabled. The GSM Remote connects to the control board of your gate motor and when called from your mobile phone it triggers the gate to open. This simplifies the process of opening your gate as when you are in your car with hands free you can simply ask SIRI or Google Assistant to call the gate and it will open.