What if Xiaomi's mobile phone doesn't display the calling number?

Determine whether the caller ID function is enabled;

Call a few more people to see if there is any display or partial display, find out the reasons and find out the countermeasures;

It is also possible that the caller ID function is not enabled. You can call the operator to complete the call display function according to the voice prompt.

Caller display service is a service that can automatically display the caller's number on the display screen of the phone, and can know the caller's phone number in advance. "Caller ID" is also called "caller ID transfer". There are two kinds: one is hanging up, that is, when user A calls user B, the phone of user B can receive the phone number of the calling party from the exchange and display the phone number; The other is the off-hook state, that is, when users A and B are talking, user C calls user B again, and B can receive the phone number of user C after hearing the prompt tone. At this time, B can choose the calling object as needed.

Integrated Services Digital Network (ISDN) is a communication network developed on the basis of digital telephone network, which can provide end-to-end digital connection and carry a variety of services including voice, image and data. ISDN adopts digital transmission and digital switching technology, and integrates telephone, fax, data, image and other services into a unified digital network for transmission and processing, providing users with two interfaces: basic rate (2B+D) and primary group rate (30B+D).

B-channel: the supporting channel of ISDN, which provides 64kbps bandwidth to transmit voice or data. D channel: the control channel of ISDN, which transmits sideband signals between ISDN network end and user end. Basic rate interface (BRI): A standard for defining ISDN interface, which generally includes one D channel and two B channels, usually called 2B+D.

reference data

Baidu encyclopedia. Baidu Encyclopedia [reference time 20 17- 12-27]