Three network cards refer to mobile phone cards that can use three network modes. According to the query of Mobile official website, three network cards refer to mobile phone cards with three network modes. Today's communication industry can be said to be the three giants of telecommunications, mobile and China Unicom. A mobile phone that can support these three kinds of mobile phone cards at the same time is called a three netcom mobile phone. The signal codes are GSM, CDMA and WCDMA respectively. At present, all smart phones on the market support the full netcom network standard.