Feature: 1. The GSM‑KEY‑4G system is a security system based on the cellular network. The GSM‑KEY‑4G system is used in conjunction with the caller ID. When the authorized number calls, the system will identify the caller and open the door. 2. GSM‑KEY‑4G integrates a professional industrial‑grade 4G engine, which can receive calls with its SIM card number just like any ordinary 4G phone. Built‑in 4G module, can work anywhere in the world through 4G, 3G and GSM Net. 3. GSM‑KEY‑4G has a memory, which stores up to 200 people who can open the door. When GSM‑KEY‑4G receives a call, it will check the calling number and whether the number is in the list. Support power failure alarm for rechargeable battery (battery not included). 4. GSM‑KEY‑4G does not have the same restrictions as ordinary remote controls. Using your mobile phone, you can even open it from far away, or even from another city! When the door is already open, it is very convenient to reach the door without waiting. 5. It has two independent relay switches, and the NO.1 relay switch is activated by dialing its mobile phone number. It will reject the call and turn on the device connected to it without answering, so there will be no call charges when dialing this machine, it will identify the authorized phone number that is calling, and refuse to answer the call without answering. Specification: Item Type: Remote Control Box Material: ABS. Package List: 1 x Remote Control Box 1 x Antenna1 x USB Data Cable1 x USB Programming 1 x Manual