I don't know which model you are talking about mobile phone Today's mobile phones are basically all connected to the Internet, and there is no main card or secondary card. You can insert cards at will. Another situation is customized phones. Because of the operator's subsidies, there will be some restrictions on the card insertion of the machine. In addition, now all Netcom's mobile phones only have customized phones. The telecom card and the mobile card can only be used together. It can only be used for mobile 4G Internet access, and there is no situation where the phone card cannot be used. To sum up what you said, mobile phones can also be divided into primary and secondary cards, It only means that this mobile phone is very old and out of date.

All Network Communication of Telecom 1.0 mobile phone Only telecom 4G and mobile 2G3G4G are supported. When telecom is set as the main card and operates in 4G mode, mobile is reduced to 2G and both cards can be used. At this time, telecom is the main data network. When the mobile is the main card and operates in 4G mode, the telecom card has no signal and cannot answer the phone when the mobile 4G data is caused because the telecom does not support 2G mode. How to distinguish? To buy a All Netcom mobile phone, you need to buy a mobile phone that supports 4G3G2G. At the same time, Telecom also supports 4G3G2G mobile phones, that is, All Netcom 3.0. It is important to note that this has nothing to do with the tricks of Telecom. It is the defect of Qualcomm Telecom's dual card at the beginning. Now it has been solved.

Most of all Netcom mobile phone Both support the telecom card as the primary card, and the primary and secondary cards can be switched freely. If the telecom card cannot be the primary card, it is often called pseudo All Netcom, that is, it only supports the two G call function of Telecom. When you buy a mobile phone, you must understand the wireless network communication parameters, such as the mode and the supported frequency band. Some so-called All Netcom mobile phones are used to save costs, It only supports the frequency bands of the three major domestic operators. If there is no such frequency band, there will be no signal at all. Many early All Netcom mobile phones are like this, such as Xiaomi Note All Netcom mobile phones. So friends who plan to go abroad must pay attention when buying mobile phones. Now my personal experience (used), Apple 6 and later All Netcom mobile phones, as well as Huawei Mate and P series All Netcom versions, Others are not clear. It should be true All Netcom, a network that supports most of the world's mobile communications. Make sure to purchase the full Netcom version without mistake

I have a favorite fan. I don't have any fans yet

The following is a screenshot of P10 network parameters

You should have bought mobile customized 4G+ mobile phone The so-called All Netcom is actually a mobile customized machine. If any card (China Unicom, China Telecom) is mobile, the other card will be locked in the 2g mode, so you can only use mobile 4g. Unless you use China Unicom+China Telecom, or China Unicom+China Telecom, China Telecom+China Telecom, you will not be allowed to use 4g

Today's Intelligent All Netcom mobile phone Both support blind insertion. There is no difference between primary and secondary cards. Telecom cards can also be used as primary cards. You mean that if China Mobile Unicom is the main card, China Telecom is the secondary card, and China Mobile Unicom network is the default data, the data of China Telecom cannot be used. At present, all smart phones do not support the primary and secondary cards to use data at the same time, so the data should be switched as the default data. I hope the above answers can help you!

There are only two reasons why the answers are so full of nonsense.

1. Your mobile phone Telecom is not supported.

2. You bought a mobile 4G+All Netcom mobile phone, which is customized by China Mobile and specially produced by the manufacturer with subsidies. As long as there is a mobile card in this mobile phone, the mobile card must be the main card, and the secondary card can only be used to answer and make calls and cannot access the Internet. If you want to use other cards to access the Internet, you must first close the mobile card!

Therefore, when you buy a mobile phone, don't buy the so-called All Netcom 4G+. It's not that it is tall, but that it is mobile and installed

You are right mobile phone It is estimated that the understanding of the mobile phone of China Netcom is still five years ago. Nowadays, all mobile phones of China Netcom support blind plug in. You can set one card as the main card, and the other card can use 2G or 3G to make calls. However, both cannot be telecom cards, or the secondary card cannot register with the network.

Xie Jin: You should have bought a mobile contract machine. Double card and double standby mobile phone If there is a telecom mobile phone, it is a telecom based card. For mobile phones that do not support telecom cards, the parameter description indicates that the primary and secondary cards cannot use telecom at the same time (because the telecom card slot is smaller and the mobile unicom card slot is larger), so the primary and secondary cards cannot use telecom at the same time. Finally, all Netcom mobile phones support telecom cards.

At present, mobile phone All networks have been fully connected.

The mobile phone is equipped with two card slots to freely select the operator card. The primary and secondary cards can be switched at will, and 4G network use will not affect each other. In real life, it saves the trouble of changing the mobile phone due to changing the operator. At the same time, it realizes global roaming and greatly improves the convenience of traveling abroad and working.

Including but not limited to the following models:

Huawei: Maimang 5. Changxiang 6S Nova、Mate 9、P9、P10

OPPO：A57、A37、R9S、R11

Vivo: Y67、Y51A、XPlay6、X9

Xiaomi: red Meter note4 , Hongmi 4A, Xiaomi 5, Xiaomi MAX2, Xiaomi MIX, Xiaomi 6 and many other models of various brands.

However, many customers still encounter problems such as the purchase of mobile phones that are all Netcom, but some operator cards cannot use 4G networks.

So, how to distinguish the true from the false? Let's talk about it

1. Look at the appearance. A phone with operator logo and "4G+" is not a real All Netcom phone.

2. Ask the shopping guide: If one mobile card is inserted into the mobile phone and the other is inserted into the telecom card or China Unicom card, can the telecom card or China Unicom card use the 4G network? Telecom and Unicom cards can access the 4G network, which means they are truly all connected. If they cannot access the 4G network, they are false all connected. (This method is inconsistent, because some shopping guides have weak professional knowledge or are more or less ambiguous for sales, so ask yourself clearly)

3. Mobile phone test: put the mobile card and the telecom or unicom card into the mobile phone card slot. In the dual card management, try to change the default mobile data to the card slot where the telecom or unicom card is located. Try to open web pages, QQ, WeChat and other network tools. If you can access the Internet, it is true to all Netcom.