utils to restore TG400 after fatal update on new version https://www.yeastar.com/firmware-download/
... before using the TG V3 firmware 91.2.0.4 to upgrade, please make sure your TG gateway’s firmware version is 91.X.X.X or its SN starts with 331; using this firmware on a non-V3 gateway will result in system crash...
unpack.sh downloads firmware for TG400 unpack and prepare image S34ML01G2-TG400-firmware-53.18.0.46.bin for writing into S34ML01G2 flash chip