Yealink Recovery Mode
This is only applicable to SIP phone series including SIP-T42U, SIP-T43U, SIP-T46U, SIP-T48U, SIP-T57W, SIP-T54W, SIP-T53W, SIP-T53, SIP-T53C, and VP59. This feature can only be supported on new factory phones running firmware version 96.86.X.X or ...