USB - 3.5mm jack cable useful for connecting your QYT KT8900 radio to a laptop or computer and programming your radio as such. Please see the media at the bottom for further information on the procedure - this cable is just the tack for the job. You'll still need a little know-how to do it.

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The QYT KT-8900 programming cable is a USB cable used to program the frequencies and memories of QYT mobile equipment, making the process easier and faster. This cable is compatible with the following radios;

• KT-8900
• KT-8900R
• KT-7900D
• KT-8900D
• KT-980 Plus
• KT-790 Plus

The package comes with the original QYT USB cable, but without a CD. The software and drivers for this cable can be downloaded online. Please note that this cable is not compatible with certain other devices, such as the TYT TH-UV88 FM analog walkie.

NB! NB! NB!
Reading sources:
Familiarize yourself with the following. Miklor is one of the authorities 
https://www.miklor.com/KT8900/
CHIRP Now Supports QYT KT-8900D - Ham Radio Reviews

Please also have a look;

Here as well;