Why can't a mobile phone with dual cards and dual standby support the use of two telecom cards at the same time? What happened?

Because CDMA was developed in Qualcomm, every telecom mobile phone needs to pay the patent fee to Qualcomm, and the profit of the mobile phone manufacturers is meager. If the telecom mobile phone can use two cards, the cost is too high.

Because telecom mobile phones need CDMA and 4G signals to be online at the same time, the cost of dual telecom card mobile phones is higher than ordinary mobile phones. If dual cards are used at the same time, four signals need to be online at the same time, so the hardware loss of the mobile phone is too great, which is not worth the loss.

Telecom cards are not cheap, not many users use them, and even fewer users use dual telecom cards. Therefore, from a practical point of view, there is little demand for dual telecom card mobile phones, so many mobile phones cannot use dual telecom cards.

Extended data:

Some "dual standby" in the market are not real dual card dual standby. For example, some mobile phones can insert two cards, but only put two cards into the phone, which is just "dual card standby". It is necessary to switch the mobile phone to switch the A card to the B card (or switch from the B card to the A card), so as to realize the pseudo-dual-card standby.

References:

Baidu Encyclopedia-Double-open and Double-standby Mobile Phone