How to switch between primary and secondary cards when sending text messages on Apple mobile phone?

Apple sends text messages to switch between primary and secondary cards, taking iPhone XR as an example. The specific steps are as follows:

1, open your mobile home page, and click Info to enter, as shown in the figure below.

2. Enter the information interface and click New, as shown in the figure below.

3. Enter the new interface and click the recipient, as shown in the figure below.

4. Enter the recipient number or add an address book, as shown in the figure below.

5. After adding the recipient, the default mobile phone card name will appear. Click on the mobile phone card, as shown in the figure below.

6. The option of two cards appears, and switch to the card you want to use, as shown in the figure below.

7. If the handover is successful, enter a short message and click Send, as shown in the figure below.

Double-on and double-standby principle:

One is composed of two chipsets, that is, two sets of baseband chips, RF chips and memory system are installed in the mobile phone, which is equivalent to putting two complete mobile phone motherboards in the same mobile phone case.

This implementation can support two SIM cards to work at the same time, and there is no need to turn on and off the phone again, but the problem is that its cost is almost twice that of ordinary mobile phones, and its power consumption is often twice that of ordinary mobile phones. Many bulky dual-card dual-standby mobile phones on the market are using this scheme.

One is to add an analog switch to the traditional mobile phone chipset and manually switch the network. The latter is usually the realization of "dual card single standby" mobile phone, but later some enterprises use it in dual standby mobile phones, which is prone to problems such as incompatibility with various SIM cards and immature control software, and the call drop rate is very high.

The principle of the current dual-card dual-standby single-pass scheme is to switch between two networks with a control IC (chip) through software and automatically search for networks. Because the switching time is very short, such as the frequency of one thousandth of a millisecond, consumers can't feel the network switching, which is equivalent to realizing the standby of two cards at the same time.

If one card has a phone access when another card is talking, the software will also set up a way to send a short message to inform the missed call. From the consumer's point of view, you won't miss any calls, which is no different from "double standby".