Mobile phone card has no signal. What happened?

There are three reasons for no signal: mobile base station problem; Mobile phone system problems; Mobile phone card problem.

In view of the above three problems, the following methods can be adopted:

1. First, check whether there is a signal on the mobile phones of friends around you. If someone else's mobile phone has no signal, it may be a problem with the local network base station. It is recommended to contact the local business hall for handling.

2. Try inserting another friend's mobile card with a mobile phone card. If you can't insert another card, there may be something wrong with the mobile phone system. It is recommended to contact the mobile phone after sales.

3. If there is a signal when inserting other cards, but it is not possible to insert your own card, there may be something wrong with your own card. It is recommended to take your mobile phone card to the local mobile business hall for testing.

Extended data:

Common faults of SIM card:

1. Whenever the mobile phone is turned on, it must communicate with the SIM card. These signals will not be sent when the card is not inserted. When the mobile phone does not respond after inserting the SIM card or the SIM card is displayed incorrectly, it may be caused by poor switch or poor contact of the SIM card or the use of waste cards.

If the fault still exists after replacing the new card, then the fault usually appears in the power supply part of the SIM card. At the power end, clock end and data end of the SIM card socket, you can observe the card reading signal at the instant of starting with an oscilloscope. If there is no such signal, the resistance and capacitance elements around the power switch of the SIM card should be welded with the card.

2. If the SIM card is available on one mobile phone but not on another, it may be that the functions of "network restriction" and "user restriction" are set in the mobile phone.

This can start the restriction function of mobile phone through 16 bit network control code (NCK) or user control code (SPCK), which needs to be solved by network operators. In addition, this failure may also be caused by insufficient power supply or poor contact of SIM card.