China Telecom's "E-Jitong" is a patented telecommunications product that mainly uses mobile phone RF-UIM cards (radio frequency mobile phone cards) to implement various applications such as access control systems, garage management, attendance systems, and consumer systems. The mobile phone access control function means that by configuring passwords and permissions for mobile phone users, mobile phone users can use their mobile phones to swipe their cards to open the door. At present, "Yijitong" is mostly used uniformly in enterprises and institutions. Telecom 189, 180, 133, and 153 mobile phone users do not need to change their mobile phones or numbers. They only need to change a specific mobile phone card to realize these functional operations.