t21p-e2.bin is a binary firmware file for the Yealink SIP-T21P E2
This file is typically used when a Yealink phone fails to boot and enters . t21p-e2.bin
sha256sum t21p-e2.bin file t21p-e2.bin binwalk -e t21p-e2.bin strings t21p-e2.bin | head -n 200 binwalk --dd='.*' t21p-e2.bin t21p-e2