Disclaimer: Flashing third-party firmware voids any remaining warranty (though Astak no longer exists). The author is not responsible for bricked devices. Proceed at your own risk.
Format your USB drive to FAT32. Name the volume "ASTAK_UPDATE". Copy the IP700_12.0.2.1.bin file to the root directory (not inside any folders). Astak ip-700 software 12
The bar will move slowly. It takes exactly 90 seconds. The unit will beep twice and reboot automatically. Astak ip-700 software 12