The CDA number identifies the sales area of the mobile phone, also known as the hardware identification number. It is the information written inside the mobile phone, and Sony Ericsson uses it to identify the sales area of the mobile phone. For example, online upgrade, many parallel K750 products sold now are all software-swiped, but the CDA number has not been changed, which means that the CDA number is still in its original sales area, so Sony Ericsson official website will recognize it as a version of other countries, so the upgraded mobile phone will become a version in other languages instead of the previous Chinese, which means that the K750 products bought in parallel now cannot be upgraded online unless the CDA number is changed. Similarly, if the parallel mobile phone does not have Chinese software, but the CDA number of Chinese mainland is changed, the mobile phone software will be directly upgraded to Chinese after online upgrade. :D & amp； mOg^%iE

Note: There is a way to modify CDA now, which means that you can't judge whether a mobile phone is a parallel product completely by looking at CDA.