Unlocks "hidden" features like voice calling (if supported by hardware) .
To modify the firmware, the modem must be placed in "Download Mode." In older Huawei modems, this was often achieved by shorting specific test points on the circuit board (a process known as "jtag" or "boot repair"). In the E173 series, specialized software tools were historically used to send AT commands that put the modem into a state ready to receive new firmware. Huawei E173u-1 Unlock Firmware
: Repositories like Firmware Center host various versions for the E173 family. Unlocks "hidden" features like voice calling (if supported
A quick Google search reveals hundreds of forums hosting "E173u_Unlock.exe" files. Be extremely careful: Huawei E173u-1 Unlock Firmware