Extract Huawei B681 firmware V100R001C994B105 on your computer
Install the firmware update file for Huawei B681 downloaded from Huaweiflashfiles.com
Follow the procedure for updating firmware that is given in Package.

Huawei Flash File | Size: 15.38 Mo
Version: V100R001C994B105
Operator: Normal
Operating systems: Windows 7/8/10/XP/Vista
Huawei B681 Firmware Download