What kind of card is sim card?

SIM card is what we often call a calling card. Without a SIM card, we can't receive short messages. Besides, you can't answer and make phone calls. For example, SIM is as important as people's ears. Without it, you can't receive information.

1.SIM card is the only customer identification in the field of mobile communication. It stores the information of digital mobile phone customers, encryption keys and other contents on the chip card, which can be used for mobile communication network to identify customers and encrypt voice information when customers talk.

2. At present, there are three kinds of SIM cards on the market: standard SIM card, micro SIM card and nano SIM card, and the three models are from big to small. With the development of the times, the standard SIM card has been abandoned, and it is mostly used for pension machines and functional machines. The latter two kinds of micro SIM cards and nano SIM cards are the mainstream smart phones in ..............